1988 MICHIGAN POTATO RESEARCH REPORT VOLUME 20 MICHIGAN STATE UNIVERSITY AGRICULTURAL EXPERIMENT STATION IN COOPERATION WITH THE MICHIGAN POTATO INDUSTRY COMMISSION THE MICHIGAN POTATO INDUSTRY COMMISSION February 28, 1989 TO ALL MICHIGAN POTATO GROWERS AND SHIPPERS: The Michigan Potato Industry Commission and the Agricultural Experiment Station of Michigan State University are happy to provide you with a copy of the results of the 1988 potato research projects. This years report includes research projects funded by the MPIC as well as projects funded through a special federal grant that the Michigan Potato Industry Commission helped secure. The federal grant data completes the fourth year of a five year project. Also included are reports on projects carried out by MSU which were not funded by the industry. Providing research funding and direction to researchers is a major function of the MPIC on behalf of Michigan growers and shippers. Input from the industry regarding research is most welcome at anytime. Regards, The Michigan Potato Industry Commission THE MICHIGAN POTATO INDUSTRY COMMISSION 13109 SCHAVEY RD., STE. 7 • DEWITT, Ml 48820 • (517)669-8377 TABLE OF CONTENTS Page INTRODUCTION AND ACKNOWLEDGEMENTS, WEATHER AND GENERAL MANAGEMENT......... 1 1988 POTATO VARIETY EVALUATIONS R.W. Chase, G.H. Silva, D. Douches, R.B. Kitchen, R.H. Leep and R. Hammerschmidt................................................... 5 DEVELOPMENT OF NEW POTATO CULTIVARS SPECIFICALLY SUITED TO MICHIGAN’S FRESH MARKET AND PROCESSING NEEDS David S. Douches, R. Chase, G. Silva, R. Hammerschmidt and J. Cash...... 37 EVALUATION OF PRODUCTION MANAGEMENT INPUTS TO IMPROVE QUALITY AND YIELD OF RUSSET NORKOTAH AND MS700-70 G.H. Silva, R.W. Chase and R.B. Kitchen................................. 40 EFFECTS OF POTASSIUM RATE AND SOURCE ON YIELD AND QUALITY OF NORCHIP AND MS700-83 G.H. Silva, R.W. Chase and R.B. Kitchen................................. 48 NITROGEN MANAGEMENT STRATEGIES FOR RUSSET BURBANK POTATOES B.C. Joern, M.L. Vitosh, D.A. Hyde, D. Duncan and B.P. Darling.......... 53 NITROGEN MANAGEMENT STRATEGIES FOR POTATOES TO MAXIMIZE PROFIT AND MINIMIZE NITRATE LEACHING: 1988 RESULTS J.T. Ritchie and B.S. Johnson........................................ 62 EFFECT OF INCREASING NITROGEN RATES UPON PRODUCTION OF RUSSET BURBANK POTATOES IN THE UPPER PENINSULA 1988 R.H. Leep.............................................................. 68 LEGUME NITROGEN CONTRIBUTIONS IN LEGUME-POTATO ROTATIONS T.S. Griffin and O.B. Hesterman...................................... 70 Page INFLUENCE OF IRRIGATION, NITROGEN AND CALCIUM LEVELS ON SPECIFIC GRAVITY AND INTERNAL DEFECTS OF ATLANTIC AND RUSSET BURBANK POTATOES G.H. Silva, R.W. Chase and R.B. Kitchen............................................................................... 79 CONTROL OF INTERNAL BROWN SPOT (HEAT NECROSIS) OF POTATOES R. Harnmerschmidt and R.W. Chase.................................................................................................. 85 IMPROVED PRODUCTION AND UTILIZATION TECHNOLOGY FOR MICHIGAN POTATOES F.J. Pierce, C.G. Burpee and R.W. Chase.......................................................................... 87 COLORADO POTATO BEETLE MANAGEMENT E. Grafius, B. Bishop, P. Ioannidis and P. Rattlingourd.............. 102 RESEARCH REPORT ON ARS/USDA COOPERATIVE AGREEMENT FOR SCAB RESEARCH R. Harnmerschmidt, D. Douches, M.L. Lacy, L. Hanson, K. Ludlam, F. Spooner and C. Wallace................................................................................................................. 115 INFLUENCE OF ENVIRONMENTAL FACTORS ON WOUND HEALING OF POTATO TUBERS IN RELATION TO STORAGE DISEASES R. Harnmerschmidt and A.C. Cameron.............................................................................................. 126 WHAT CONSUMERS WANT IN FRESH POTATOES... KNOW-HOW PRODUCERS CAN USE TO INCREASE MARKET SHARE AND PROFITABILITY Mary D. Zehner............................................................................................................................................129 THE INFLUENCE OF CHLOROPROPHAM (CIPC) ON POTATO CARBOHYDRATES DURING COMMERCIAL PRODUCTION AND STORAGE J.N. Cash, N.K. Sinha and R.W. Chase.......................................................................................132 BISULFITE ALTERNATIVES FOR FRESH, PEELED POTATOES J.N. Cash, C.R. Santerre and T.F. Leach................................................................................139 POTATO STORAGE RESEARCH — PHASE C (THIRD YEAR) Roger Brook and Todd Forbush.......................................................................................................... 149 1988 POTATO RESEARCH REPORT1 Dr. R.W. Chase, Coordinator Department of Crop and Soil Sciences Michigan State University INTRODUCTION AND ACKNOWLEDGEMENTS The 1988 Potato Research Report includes reports of potato research projects conducted at the Montcalm Research Farm plus those conducted at other locations. This volume includes research projects funded by the Special Federal Grants (USDA 85-CRSR-2-2562 and 88-34141-3372), the Michigan Potato Industry Commission and other sources. The principal source of funding for each project has been noted at the beginning of each report. We wish to acknowledge the excellent cooperation of the Michigan potato industry and the MPIC for their continued support of the MSU potato research program. We also want to acknowledge the significant impact that the funds from the Special Federal Grant have had on the scope and magnitude of several of the research areas. Many other contributions have been made in the form of fertilizers, pesticides, seed, supplies and monetary grants and we are very appreciative of this support also. A special thanks to Dick Kitchen for his excellent coordination of the production management needs and the day-to-day operations at the Farm. We also want to acknowledge the donation to MSU of the equipment building, the land and 17 new acres of land purchased by the MPIC from Mr. and Mrs. Theron Comden. This new facility will definitely allow for the improvement of the facility and farm operations and will also provide greater land availability for additional research, field days and other events. WEATHER The 1988 weather data for the Montcalm Research Station as compared to the average of the previous 15 years are presented in Tables 1 and 2. The weather during the growing season was characterized by the well publicized drought and high temperatures. Rainfall was well below normal in May and June. In the 3 month period from May to July, there were only 8 days where a rainfall of 0.1 inches or greater was recorded (Table 3). Temperatures during May, June, July and August were well above the average. There were 9 days in August when the minimum night temperature exceeded 70°F. There were 8 days in July and 14 days in August when the minimum soil temperature at 4” depth exceeded 70°F. Higher night temperatures promote higher respiration rates and is detrimental to dry matter accumulation. The combination of inadequate rainfall and higher than normal temperatures resulted in more frequent irrigations than an average year. Higher than normal rainfall in September interfered with scheduled harvesting operations. 1Printing and distribution of this report was made possible by the Michigan Potato Industry Commission and USDA grant 88-34141-3372. SOIL TESTS Soil test results for the general plot area were: pH 5.9 P lbs/a 504 K lbs/a 282 Ca lbs/a 1040 lbs/a Mg %Organic Matter 189 1.5 FERTILIZERS USED The previous crop in the plot area was alfalfa planted in April, 1987. Except in fertilizer trials, where the amounts of fertilizer applied are specified in the project report, the following fertilizers were used in the potato trials: banded at planting sidedress with irrigation 15-10-15 23 lbs N in 2 separate applications 500 lbs/a HERBICIDES AND HILLING Most of the hilling was completed by the end of May. At cracking, the potatoes were hilled, building a wide and flattened hill and placing minimal soil over the top of the ridge. Immediately after hilling, a tank mix of metolachlor (Dual) 2 lbs/a plus metribuzin (Lexone 4L) lb/a was applied on May 20. No further tillage was done until harvest. Several hand weedings were performed during the season. Potato vines were killed with Diquat+ X77 on September 8. IRRIGATION Due to the extremely dry, hot summer, 18 supplementary irrigations were applied on June 3, 9, 13, 16, 20, 23, 28, July 1, 5, 8, 13, 22, 25, 28, August 2, 4, 15 and 31. Irrigation scheduling was done according to the Michigan State University irrigation scheduling program. The minimum profile moisture content allowed throughout the growing season was 50-60%. The amount of water applied was 0.75 inches per application. Urea (28%) was incorporated into irrigation water on June 28 and July 22. Despite the prolonged dry spell, irrigation was sufficient to prevent any appearance of moisture stress. This was reflected in the average tuber yields which were about 15% higher than 1987. INSECTS AND DISEASE CONTROL Aldicarb (Temik 15G) was applied at planting at 20 lbs/a with the fertilizer. The foliar fungicide application was initiated on June 29 and 10 applications were made throughout the season. Fungicides used were Dithane M45 (5 applications), Ridomil (2 applications) and Bravo 500 (3 applications). Fungicides were generally used alternatively and were sprayed at 7-10 day intervals. Foliar insecticides used were Imidan (6/29, 7/12, 8/3 and 8/13) and Thiodan on 8/10. No serious disease or insect problems were encountered during the season. Table 1. The 15 year summary of average maximum and minimum temperatures during the growing season at the Montcalm Research Farm. April Apri Ma Max l Min yMax May Min Jun Jun Jul Augus Augus Septembe Septembe 6-Mont h Averag 6-Mont h Averag eMax e Min yMax July Min tMax t Min r Max r Min e Max e Min 57 48 58 62 50 50 49 56 53 47 54 58 60 61 52 54 36 28 35 37 31 33 31 35 28 28 34 38 36 36 31 34 62 73 63 80 67 66 69 64 72 60 60 70 70 77 74 69 41 48 41 47 45 44 42 39 46 38 39 44 46 46 46 43 73 75 79 76 78 74 73 73 70 76 77 71 77 80 82 75 52 56 57 50 50 55 50 50 44 49 54 46 50 56 53 52 81 80 81 85 81 82 81 77 80 85 78 81 82 86 88 82 57 57 58 61 56 57 58 51 53 57 53 55 59 63 60 56 77 79 80 77 82 77 81 78 76 82 83 75 77 77 84 79 56 58 53 52 57 55 58 53 48 57 55 54 51 58 61 55 68 65 70 70 75 76 70 67 66 70 69 70 72 72 71 70 45 44 46 53 52 47 49 47 44 46 45 50 50 52 49 49 70 70 71 75 72 71 71 69 70 70 70 71 73 76 75 72 48 49 48 50 49 49 48 46 44 46 47 48 49 52 50 48 Year 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 15-YR. AVG. Table 2. The 15 year summary of precipitation (inches per month) recorded during the growing season at the Montcalm Research Farm. Year 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 15-YR. AVG. April May 4.07 1.81 3.27 1.65 2.34 2.58 3.53 4.19 1.43 3.47 2.78 3.63 2.24 1.82 1.82 2.70 4.83 2.05 4.03 0.46 1.35 1.68 1.65 3.52 3.53 4.46 5.14 1.94 4.22 1.94 0.52 2.74 June 4.69 4.98 4.22 1.66 2.55 3.77 4.37 3.44 5.69 1.19 2.93 2.78 3.20 0.84 0.56 3.09 July 2.39 2.71 1.50 2.39 1.89 1.09 2.64 1.23 5.53 2.44 3.76 2.58 2.36 1.85 2.44 2.45 August September 6.18 11.25 1.44 2.61 5.90 3.69 3.21 3.48 1.96 2.21 1.97 4.72 2.10 9.78 3.44 4.27 1.81 3.07 1.40 8.62 2.77 0.04 6.59 3.82 3.24 5.34 3.90 3.30 18.60 3.32 5.36 4.72 Total 23.97 25.87 15.86 17.39 16.80 12.85 21.99 19.68 21.38 19.11 20.48 18.95 32.72 19.55 14.14 19.97 Table 3. Weather highlights at Montcalm in summer 1988. Days with Number of Days Number of Days May June Number of Days April Number of Days July Number of Days August Number of Days September RF greater than 0.1” Maximum day temp >90°F Minimum night temp >70°F Minimum soil temp >70°F 5 0 0 0 2 1 0 0 2 8 0 3 4 10 2 8 8 12 9 14 6 0 0 0 Funding Federal Grant 1988 POTATO VARIETY EVALUATIONS R.W. Chase, G.H. Silva, D. Douches, R.B. Kitchen, R.H. Leep and R. Hammerschmidt The potato variety evaluation and management program is designed to identify improved cultivars that will satisfy the needs of Michigan’s fresh market and processing industry. Round whites, russets and red-skinned varieties are tested separately and their potential for specific markets are evaluated. Round whites and russets are harvested at 2 harvest dates to evaluate their marketable and physiological maturity and adaptability to Michigan. Selected varieties are then subjected for more intensive tests to determine optimum production management inputs that improve potato quality and marketability. In all variety evaluations, special consideration was given to quality parameters. The focus was on tuber appearance, size distribution, external and internal defects, specific gravity (dry matter content), chip color, storability and culinary properties. Also of significant interest to Michigan is tolerance to common scab and bruising. Potential chipping varieties are stored in 2 storage environments (45 and 52°F) to evaluate chip color, reconditioning and storability. A. DATES OF HARVEST TRIAL FOR ROUND VARIETIES The 1988 dates-of-harvest trial was conducted at the Montcalm Research Farm. Seven named and 10 advanced selections were tested for their marketable maturity and adaptability to Michigan at 2 harvest dates of 98 and 143 days after planting. Four replications of a randomized complete block design were harvested at each harvest date. Plots were 23 ft x 34 inches with plant spacing of 12 inches. The previous crop was alfalfa. Fertilizers and Temik 15G were applied as described in the previous chapter. The hilling and herbicide application were completed just prior to cracking, which was May 20. During the growing season the crop was irrigated 18 times according to the MSU irrigation scheduling program. The amount of water applied per irrigation was 0.75 inches totalling 13.5 inches for the season. Fungicides for early blight control were usually alternated as described in the previous chapter. An early and late blight forecasting program from Wisconsin was used as a guide to commence spraying. Relative humidity and temperature at canopy levels were monitored for this purpose. Weather data was collected with a programmed Campbell’s CR21 micrologger. For chip color determinations, 20 tubers were taken at random and a slice from each tuber used for the test. Agtron E-10 Colorimeter was used for color measurements. For after cooking darkening, peeled halves of 3 tubers picked at random were cooked in steam and evaluated at 0, 1 and 24 hours. Susceptibility to blackspot bruising was evaluated in artificially bruised and check treatments. Artificial bruising was done by taking potatoes out of 40°F storage and placing 20 tubers inside a wooden drum and turning 10 revolutions at a moderate speed. In the check treatments, potatoes were tested without artificial bruising, so that any blackspot observed occurred during harvest and handling. The artificially bruised tubers were kept for 48 hours at room temperature prior to peeling. A Hobart peeler was used for peeling the tubers. Results The yield and quality parameters of round potato varieties at 2 harvest dates are presented in Tables 1 and 2. Inspite of the prolonged dry summer, tuber yields were up by about 15% compared to 1987. At 98 days, Onaway, Superior and Eramosa were the earliest in maturity. Eramosa, although the lowest yielder, matured very early (approximately 80 days) with smooth oblong tubers and good general appearance. However, some scab was noted. Among the medium to medium-late maturing varieties, MS700-83, Michigold, Saginaw Gold, W855 and AF236-1 performed well. MS700-83 produced excellent yields and acceptable chip color but the gravity was low for processing. It has excellent potential as a fresh market potato but does have susceptibility to scab, growth cracks and after cooking darkening. Saginaw Gold, which is a joint release between MSU and Agriculture Canada, produced average yields with an excellent chip color, however, dry matter is lower than desired for processing. Michigold has a higher gravity than MS700-83 and an acceptable chip color out of field with susceptibility to scab and air checks. W855 appears to have the best potential for chip processing, produced average yields with medium-high gravity and excellent chip color. It was noted that the CPB is attracted to its foliage. Tubers were attractive and free of any internal defects with some susceptibility to scab. Somerset (AF236-1) produced an excellent chip color and tubers are cylindrical in shape. Kanona (NY71) has excellent chip color but had low gravity and was susceptible to scab. MS716-15 had excellent chip color and dry matter but the yields were unusually low in 1988. Among the late maturing varieties, FL657, NY81, MS700-70 and LA01-38 produced prolific yields with a high percent of oversized tubers. MS700-70 produced the highest gravity but the type was average with medium deep eyes. There was a high percent of chip defects in FL657, MS700-70 and LA01-38 due to severe stem end browning. In the culinary tests (Table 3), undesirable levels of after cooking darkening were found in LA01-38 1 hour after boiling. Other varieties that turned slightly dark were MS700-83, Onaway, NY71, W855 and Eramosa. Some sloughing was observed with Atlantic and MS716-15, which have high specific gravity. Susceptibility of varieties to blackspot are presented in Table 4. In the artificially bruised treatments, varieties that had less than 30% of tubers with blackspot were Eramosa, MS716-15, Saginaw Gold, W848, MS700-83, and FL657. The varieties that showed a high percent of blackspot damage were LA01-38, W855, Atlantic and NY71. In the check treatments, most varieties showed no significant amounts of blackspot. Variety Characteristics MS700-83 - Mid season maturity and above average yields with medium gravity. Has excellent potential for fresh market and chipping. In some years, growth cracks and air checks have been reported. Some susceptibility to after cooking darkening in certain years and locations. Some scab was found in 1988 trials. Michigold - Yellow fleshed and tubers are slightly flattened. Mid-season maturity with high gravity. It sets heavy and the flesh has an attractive golden color. It produces an attractive golden color chip when processed from field and short term storage. In some locations, air checks and growth cracks have been reported. Susceptible to scab. MS716-15 - Medium-late maturity, tubers well shaped and smooth general appearance. It has high gravity, excellent chip color and no internal defects. It is susceptible to scab. MS700-70 - Late season maturity with prolific yields. It has high gravity and excellent chip color out of field. Tubers are somewhat rough in appearance with medium deep eyes. Tends to produce a high percent of oversized tubers at 12” spacing. Saginaw Gold - Round to oblong tubers with light yellow flesh and mid season maturity. It has an excellent chip color but the specific gravity was slightly lower than desired for processing. Good appearance after cooking. NY81 - Very late maturity with medium gravity. Tends to produce a high percent of oversized tubers at 12” spacing. Produced above average yields with minimal internal defects. Kanona (NY71) - Medium to late maturity with above average yields. Excellent chip color but the gravity was too low. Severe scab was noticed in the 1988 trials. LA01-38 - Late season maturity with above average yields. It has an acceptable chip color with medium gravity. In 1988, it had a high percent of chip defects due to severe stem end browning. In artificially bruised treatments, it was susceptible to blackspot. Some susceptibility to after cooking darkening was observed. W855 - Medium to late maturity with average yields. It has medium to high specific gravity and excellent chip color. Tends to produce undersized tubers if spaced too close. Some scab was present in 1988. Some reports of increased Colorado beetle attack to its foliage. Has potential in Michigan for chipping. Showed some susceptibility to blackspot in artificially bruised treatments. Somerset (AF236-1) - Medium to late maturity, with average yields. Tubers are oblong in shape with medium gravity. Chip color is excellent. Some growth cracks were found in 1988 trials. Eramosa - Very early maturity (80 days) with smooth, round to oblong tubers and good general appearance. It had no internal defects. Gravity is lower than Onaway. Some scab was found in 1988 trials. Has potential for first-early market. W848 - Medium to late maturity, above average yields with medium gravity. It has excellent chip color. Produced a high percent of oversized tubers at 12” spacing. Tubers had a high percent of vascular discolorations. Some scab was present in 1988. MN12823 - Medium to late maturity, above average yields with low gravity. Susceptible to hollow heart and tends to be oversized if spaced at 12”. Atlantic - Mid to late season maturity. High gravity, excellent chip color and is the major chipping variety in Michigan. It is susceptible to internal brown spot, hollow heart and scab. Norchip - Mid-season maturity with below average yields. It has medium gravity but excellent chip color. Tubers vary in size and shape and the appearance is rough. It had some scab in 1988 trials. Onaway - Early maturity with above average yields. Tubers are round to oblong. Minimal internal defects but vascular discolorations are found in some years. It has a tendency to produce oversized tubers and is susceptible to growth cracks and early blight. FL657 - A variety released from Frito-Lay, Inc. Late maturing with prolific yields. It has light yellow flesh, low specific gravity and a rough appearance on the larger tubers. Tends to oversize at 12” spacing. B. DATES-OF-HARVEST TRIAL FOR COUNT PACK VARIETIES Eighteen russet and long varieties were evaluated for the count pack and processing potential at 2 harvest dates, 112 and 144 days (Tables 5 and 6). Maturing early were Russet Norkotah, HiLite Russet, Norgold Russet and Krantz. Based on external appearance and internal defects, the varieties with count pack market potential were Russet Norkotah, HiLite Russet, A76147-2 and A74114-4. Those with high gravity and potential for processing were A7411-2, A79341-3, A79357-17 and A78242-5. A78242-5 is a very blocky russet with the lowest percent of 4 oz. tubers. After cooking darkening data is presented in Table 7. None of the potato varieties showed any undesirable levels of darkening 1 hour after boiling. Russet Norkotah, Krantz and Russet Burbank rated exceptionally good after boiling. Blackspot susceptibility data is presented in Table 8. In artificially bruised treatments, the varieties that appeared to be highly resistant to blackspot were Russet Norkotah, HiLite Russet, Norking Russet and Krantz. Varieties that had greater than 30% of tubers with blackspot damage were A78242-5, A79357-17, A7411-2, NEA71.72-1 and MN10874. In the check treatments, most varieties showed no significant blackspot. Varieties that had the best appearance after peeling were A76147-2, A79341-3, Shepody, Russet Norkotah, HiLite Russet, Norking Russet, ND671-4R and Krantz. Variety Characteristics A76147-2 - Long, very light russet, late maturity with high yields and medium It has good external appearance and minimal internal gravity. defects. Has potential for fresh market. Some heat sprouts were observed in 1988 trials. A78242-5 - Good early growth and vigor. Russet, maturity is late with above average yields and gravity. Has good external appearance and a tendency to produce a high percent of oversized tubers. Some internal defects were found in 1988 trials. A79341-3 - Late maturing russet, with high solids. Good external appearance and quality. Some hollow heart developed in oversized tubers. A79357-17 - Good early growth and vigor. Produced above average yields and medium gravity. Maturity is considered very late. Russet with good external appearance and quality. A79239-8 - Has early emergence, good vine growth and early vigor. Maturity is considered very late and similar to Russet Burbank. Produced above average yields. Some hollow heart was observed in oversized tubers. A74114-4 - Mid to late season maturity with average yields and medium gravity. Russet, has good cooking qualities. Has excellent external appearance, quality and potential for count-pack market. Internal defects are minimal. HiLite Russet - A patented variety, mid-season maturity with average yields and low gravity, somewhat similar to Russet Norkotah. Has good cooking qualities and resistance to blackspot. Has good external quality, appearance and potential for count-pack market. Shepody - Long white, mid-late season maturity. Maturity 2-3 weeks earlier than Russet Burbank normally. It has good external and internal qualities. Slow emergence and early establishment. Pre-cutting of seed is recommended. It is susceptible to scab and hollow heart may occur in larger tubers. Norgold Russet - Mid-season maturity with below average yields and gravity. Good external appearance and quality. Produced a high percent of undersized tubers. Krantz - Oblong russet, mid to late season maturity with below average yields and gravity in 1988. Produced a high percent of undersized tubers. Cooking qualities and blackspot resistance appeared to be very good. SH-1 - A patented line introduced by Plant Genetics, Inc. Very late maturity, above average yields with medium gravity. It has a very high frequency of hollow heart in oversized tubers. At harvest tubers were skinned and pink eye was observed. Russet Norkotah - Oblong to long russet, early to mid-season maturity. Tubers have a very smooth appearance with a gravity lower than Russet Burbank. Excellent potential for count pack market. Has excellent cooking qualities and blackspot resistance. A7411-2 - Mid to late maturity, average yields with high gravity. Tubers have good external appearance. Excellent potential for processing with few internal defects. Should be handled carefully because of potential for blackspot damage. NEA71.72-1 - Mid to late maturity, below average yields with low gravity. Tubers have a tendency for pointed ends and undersized. ND671-4R - Mid season maturity with below average yields. It produced a high percent of undersized tubers. Tubers have a smooth appearance with no internal defects. The gravity is lower than desired for processing. MN10874 - Late season maturity with average yields and low gravity. Tubers had no internal defects. C. RED-SKINNED VARIETY TRIAL Due to the increased interest in red-skinned varieties, 12 red selections were tested in a randomized complete block design with 4 replications (Table 9). The emphasis was on fresh market potential with uniform size, shape and color retention after storage. The varieties that showed the best appearance and color at harvest were ND2224-5R, NDT9-1068-11R, ND791-5R and Sangre. The internal defects were very minimal. The tubers were stored at 40°F to evaluate their storage performances. After cooking darkening data is presented in Table 10. ND2224-5R showed severe after cooking 1 hour after boiling. Other varieties with a tendency for after cooking darkening were W949-R, Rideau and Red Gold. Blackspot data is present in Table 11. In artificially bruised treatments, W948-R and Red Gold showed the highest frequency of blackspot. In check treatments, all varieties were tolerant to blackspot. Variety Characteristics Red LaSoda - Late maturity with above average yields. Has a tendency to oversize at 12” spacing. W949R - Late maturity with above average yields. Has a tendency to oversize at 12” spacing. Some tendency for after cooking darkening. NDT9-1068-11R - Late maturity with above average yields. Good appearance and red color at harvest. Has not performed well in storage in 1988 with decay and bruise problems. ND791-5R - Early to medium maturity with above average yields. Good appearance and red color at harvest. Vigorous early growth and establishment. Reddale - Late maturity with average yields. Susceptible to growth cracks. ND2224-5R - Early to medium maturity with average yields. Very susceptible to after cooking darkening in 1988. Excellent color and appearance at harvest. Rose Gold - Mid-season maturing with average yields. Has yellow flesh and a pink skin. Has excellent cooking qualities and blackspot tolerance. Tubers were somewhat undersized. Vigorous early growth and establishment. Sangre - Mid-season maturing with average yields. Has excellent color at harvest. Very slow early establishment and pre-cutting of seed is recommended. Rideau - Late maturing with below average yields. Had a tendency for dark ends after boiling in 1988. Very slow early establishment and pre-cutting of seed is recommended. W948-R - Very late maturing with below average yields. Showed a higher percent of blackspot in artificially bruised treatments. Red Gold - Mid-season maturing with below average yields. Has a pink skin and yellow flesh. Had a tendency to darken after boiling in 1988. MN12949 - Mid-season maturing with below average yields. Tubers have a very low gravity and tendency to be undersized. D. UPPER PENINSULA TRIAL Nineteen potato varieties were tested in a randomized complete block design with 4 replications in the Upper Peninsula. The results are presented in Table 12. Among the count pack varieties, those that produced the highest yields were A76147-2, A79341-3, A78242-5, MN10874 and A7411-2. Varieties that produced above average specific gravities were A79341-3, MN10874, A7411-2, A79239-8, A79357-17 and Russet Burbank. The round varieties produced below average yields but MS716-15 produced an exceptionally high specific gravity. E. NORTH CENTRAL REGIONAL TRIAL This trial is conducted in 14 states and provinces with entries from various breeding programs to obtain data from a wide range of locations prior to a release decision. Two MSU lines (MS716-15 and MS700-70) were included in the 1988 trial. Eighteen varieties (10 round whites, 6 reds and 2 russets) were tested in a randomized complete block design with 4 replications. The results are summarized in Tables 13 and 14. On a general merit rating based on external appearance and overall worth as a variety, the 5 top varieties in the trial were MS716-15, NDT9-1068-11R, W855, ND2224-5R and NEA22.75-1. The highest tuber yield was produced by MS700-70. Several other participating states have consistently given high merit ratings to the MSU seedlings tested in this trial. In culinary tests (Table 15), undesirable levels of after cooking darkening were observed in ND2224-5R, ND1215-1, NEA219.70-3 and NEA22.75-1. ND1215-1 had a very occurrence of internal necrosis symptoms in the peeled potatoes. In artificially bruised treatments, the varieties that showed any appreciable levels of blackspot damage were W855 and W1005 (Table 16). In the check treatments, most varieties showed no significant blackspot. F. ADVANCED ADAPTATION TRIAL Entries to this trial consisted of selections from 1987 adaptation trial and potential new lines for chipping released from other states. Two yellow varieties, ND1859-3 and ND2107-1, were included in the trial. The results are presented in Table 17. Most varieties tested in this trial produced excellent chip color. However, the specific gravity of BR7093-24 was lower than desired for processing. BR7093-24 produced prolific yields and had a tendency to oversize at 12" spacing. AF875-16 had the highest gravity (1.089) and appeared promising for chipping. In the culinary test (Table 18), undesirable levels of after cooking darkening were observed in ND1859-3, ND2109-7 and Atlantic 1 hour after boiling. Blackspot results are presented in Table 19. In artificially bruised treatments, varieties that showed a high frequency of blackspot damage were NYD164-9, ND2330-3, ND1859-3, BR7093-24 and ND2109-7. In the check treatments, however, most varieties showed no significant blackspot. Some of the promising varieties from this trial will be tested in the 1989 dates-of-harvest trial, depending on the availability of seed. G. MSU SEEDLINGS TRIAL Fourteen new MSU advanced seedlings were entered into this trial and tested in a randomized complete block design with 4 replications. These include 8 lines from the 401 series (Atlantic x Yukon Gold) and 6 lines from the 402 series (Atlantic x Onaway). Four lines from the 401 series were yellow fleshed varieties. The results are presented in Table 20. Based on external and internal quality characteristics, 7 lines were selected for further testing. These lines were MS401-1, 401-2, 401-4, 401-7, 401-8, 402-7 and 402-8. MS401-1, 401-2 and 401-8 are yellow fleshed varieties with high gravity and excellent chip color. MS401-7 had the highest specific gravity (1.090) and produced excellent U.S. #1 yields. In the culinary test (Table 21), only MS401-7 showed some tendency for after cooking darkening. In the blackspot evaluation (Table 22), MS401-4 showed the highest frequency of blackspot in artificially bruised treatments. In the check treatments, all selected varieties showed no significant blackspot. Depending on the availability of seed, some of the selected varieties from this trial will be tested in the 1989 dates-of-harvest trial. Table 1. Michigan State University — Montcalm Research Farm — 1988 — Yield of First Date of Harvest —Round varieties (98 days). Yield (cwt/a) Yield (cwt/a U.S. No. 1 Total Percent Size Distribution U.S. No. 1 Percent Size Distribution Percent Size Distribution Percent Size Distribution <2" 2-3 1/4" >3 1/4" Percent Size Distribution Pick Outs Variety No./1 No. /15 No. /15 Specific Gravity Maturity* 5 HH VD IBS Chip** Color 1.064 1.062 1.084 1.071 1.084 1.076 1.065 1.075 1.072 1.074 1.079 1.071 1.070 1.079 1.083 1.075 1.056 1.073 2.2 4.0 3.4 3.3 3.8 4.2 2.0 3.8 4.5 3.0 5.0 3.8 3.8 4.0 4.0 3.5 1.5 4 0 0 1 2 0 5 1 0 1 1 0 0 0 0 0 4 empty table cell 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 49 71 71 76 64 64 61 73 66 70 70 70 69 72 70 79 51 67 Onaway 481 FL657 463 453 Atlantic 444 MS700-83 Michigold 442 NY81 433 422 Superior AF236-l 415 415 LA01-38 Saginaw Gold 390 MS700-70 384 NY71 383 368 W848 338 W855 334 MS716-15 318 Norchip 238 Eramosa 395 AVERAGE 502 480 486 489 485 450 442 456 433 449 417 401 395 396 378 390 269 430 96 96 93 91 91 96 95 91 96 87 92 95 93 85 88 81 88 92 4 3 7 9 8 4 4 9 3 7 5 4 5 15 11 7 10 empty table cell 81 69 76 82 88 58 88 76 68 82 76 75 75 83 86 78 83 15 27 17 9 3 38 7 15 28 5 16 20 18 2 2 3 5 0 1 0 0 1 0 1 0 1 6 1 1 2 0 1 13 2 empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell *Maturity: 1 = very early; 5 = very late. **Agtron chip color: >60 = excellent; 55-60 = good; 50-55 = fair; <50 = not acceptable. Planting Date: May 3, 1988. Harvest Date: August 11, 1988. Table 2. Michigan State University — Montcalm Research Farm — 1988 — Yield of Second Date of Harvest — Round varieties (143 days). Yield (cwt/a) U.S. No. 1 Yield Percent Size Percent Size Distribution Percent Size Distribution Percent Size Distribution (cwt/a) Total Distribution U.S. No.1 <2" 2-3 1/4" >3 1/4" Percent Size Distribution Pick Outs No./2 No./20 No./20 Specific Gravity Chip Color 0 HH VD IBS Variety FL657 NY81 MS700-70 MS700-83 LA01-38 W848 Onaway NY71 MN12823 W855 Atlantic Saginaw Gold AF236-1 Michigold MS716-15 Norchip Eramosa AVERAGE 554 500 498 496 491 479 473 466 465 464 447 419 418 414 413 385 318 452 598 529 533 555 524 509 521 490 510 523 476 475 441 462 471 469 368 497 93 95 93 90 94 94 91 95 91 89 94 88 95 90 88 82 86 91 1 4 4 8 4 3 6 4 5 10 5 8 4 9 12 8 13 49 50 39 14 31 21 16 31 22 9 19 9 12 11 6 5 16 empty table cell 44 45 54 76 63 73 75 64 69 80 75 79 83 79 82 77 70 6 1 3 2 3 3 3 1 4 1 1 4 1 1 0 10 1 60 58 66 60 59 68 38 69 59 78 71 80 77 60 64 70 41 0 1 1 0 0 0 0 1 2 1 3 0 0 0 0 0 0 2 3 4 2 2 5 2 4 3 3 1 1 0 2 1 1 0 0 0 2 0 1 0 0 0 1 1 4 0 0 0 0 0 0 1.064 1.074 1.081 1.071 1.073 1.073 1.068 1.071 1.071 1.078 1.081 1.074 1.074 1.077 1.083 1.074 1.059 1.073 empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell Planting Date: May 3, 1988. Harvest Date: September 26, 1988. Table 3. After cooking darkening* of Round varieties in the 1988 dates-of-harvest trial. Variety 0 Hours 1 Hour 24 Hours FL657 NY81 MS 700-70 MS700-83 LA01-38 W848 Onaway NY71 MN12823 W855 Atlantic Saginaw Gold Somerset Michigold MS716-15 Norchip Eramosa 1 1 1 1 1 1 1.5 1.5 1 1.5 1 1 1 1 1 1 1 1 1.5 1 1.5 2.5 1 1.5 1.5 1 1.5 1 1 1 1 1 1.5 1.5 1 1.5 1 2.0 2.5 1 2.0 2.0 1 2.0 1 1 1 1 1.5 1.5 2.0 Comments empty table cell Flesh turned yellow Good 1 very dark 2 very dark empty table cell All 3 slightly dark 1 very dark empty table cell All 3 slightly dark Some sloughing Good empty table cell Nice yellow flesh Some sloughing empty table cell Slightly dark *Rating based on a scale of 1-5; 1 = no darkening, 5 = severe darkening (black). Table 4. Blackspot susceptibility of 1988 dates-of-harvest trial for Round varieties. Bruisedy Artificially Artificially Bruised y Check Percent of Tubers with Blackspot Severityz Percent of Tubers with Blackspot Check Severity 15 30 25 15 70 25 35 45 30 50 45 25 30 20 30 5 0.15 0.55 0.25 0.15 1.10 0.45 0.55 0.65 0.35 0.80 0.55 0.25 0.45 0.20 0.30 0.05 5 0 0 0 10 10 20 10 5 5 5 5 5 0 15 5 0.05 0 0 0 0.10 0.10 0.25 0.10 0.05 0.05 0.05 0.05 0.05 0 0.20 0.05 Variety* FL657 NY81 MS700-70 MS700-83 LA01-38 W848 Onaway NY71 MN12823 W855 Atlantic Saginaw Gold Michigold MS 716-15 Norchip Eramosa xVarieties are arranged according to U.S. #1 tuber yield in the 1988 dates-of-harvest trial. yTubers removed from 40°F storage and bruised artificially with 10 revolutions in a wooden drum and peeled 48 hours later. zBlackspot bruises per tuber. Table 5. Yield of Count Pack Varieties at Harvest 1 — Montcalm Research Farm — 1988 (112 days). Yield (cwt/a U.S. No. 1 Yield (cwt/a) Percent Size Total Distribution U.S. No. 1 Percent Size Distribution <4 oz. Percent Size Distribution 4-10 oz. Percent Size Distribution >10 oz. Percent Size Distribution Pick Outs Specific Gravity Maturity empty table cell empty table cell empty table cell empty table cell Variety A76147-2 A78242-5 SH-1 A79341-3 A79357-17 A74114-4 A7411-2 A79239-8 Shepody HiLite Russet MN10874 Norking Russet Russet Norkotah NEA71.72-1 ND671-4R Russet Burbank Norgold Russet Krantz AVERAGE 498 478 460 386 385 378 362 350 349 309 308 303 302 298 258 208 184 150 331 591 522 564 452 468 423 425 451 435 399 388 377 354 402 368 335 294 229 415 84 92 82 85 82 89 85 78 80 77 79 80 85 74 70 62 63 66 79 8 4 11 8 15 9 10 13 13 22 21 15 13 20 30 25 37 30 25 47 20 40 19 38 26 20 24 9 13 19 25 10 10 3 4 8 empty table cell 59 45 62 45 63 51 59 58 56 68 66 61 60 64 60 59 59 58 Maturity: 1 = early; 5 = very late maturity. Planting Date: May 2, 1988. Harvest Date: August 24, 1988. 8 4 7 7 3 2 5 9 7 1 0 5 2 6 0 13 0 4 1.074 1.074 1.076 1.085 1.080 1.074 1.091 1.077 1.079 1.070 1.073 1.074 1.070 1.071 1.070 1.076 1.070 1.070 1.075 5.0 4.0 5.0 4.0 4.0 4.0 4.0 5.0 4.0 3.0 4.0 3.5 3.0 4.0 3.5 4.5 3.0 3.5 Table 6. Yield of Count Pack varieties at Harvest 2 — Montcalm Research Farm — 1988 (144 days). Yield (cwt/a) Yield (cwt/a) U.S. No. 1 Percent Size Distribution 4-10 oz. Percent Size Distribution >10 oz. Percent Size Distribution Pick Outs Specific Gravity Internal Defects Internal Defects Maturity Internal Defects IBS HH VD Variety 527 A76147-2 508 A78242-5 SH-1 452 388 A79239-8 358 A79341-3 356 A79357-17 Shepody 303 301 MN10874 298 A7411-2 297 A74114-4 NEA71.72-1 281 Russet Norkotah 261 247 HiLite Russet Norking Russet 225 196 ND671-4R 184 Russet Burbank 146 Krantz 133 Norgold Russet 303 AVERAGE Percent Size Distribution <4 oz. 11 5 10 12 12 16 16 23 11 17 29 18 30 19 36 30 31 42 Percent Size Distribution U.S. No. 1 76 86 76 79 76 72 75 76 75 79 67 78 68 72 62 49 64 57 73 Total 697 594 592 489 471 495 406 394 397 377 422 335 362 309 320 375 227 234 416 24 48 25 26 25 23 17 8 24 19 7 21 8 7 4 2 6 3 52 38 51 53 51 49 58 68 51 60 60 57 60 65 58 47 58 54 13 9 14 9 12 12 9 1 14 4 4 4 2 9 2 21 5 1 empty table cell Internal defects of oversized (>10 oz.) tubers. Maturity: 1 = early; 5 = very late maturity. CV (U.S. No. 1) = 15.0%. Planting Date: May 2, 1988. Harvest Date: September 9, 1988. 1.073 1.075 1.075 1.078 1.081 1.078 1.077 1.071 1.087 1.073 1.071 1.068 1.070 1.072 1.068 1.075 1.071 1.069 1.074 5.0 4.0 5.0 5.0 4.0 4.5 4.0 4.0 4.0 4.0 4.0 3.0 3.0 3.5 3.5 4.5 3.5 3.0 5 2 0 8 2 5 2 0 2 1 4 2 0 2 0 1 0 0 empty table cell 0 4 22 6 4 1 0 0 2 0 0 0 0 2 0 0 0 0 0 4 1 0 0 0 0 0 2 0 0 0 0 0 0 0 0 1 empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell Table 7. After cooking darkening* of potato varieties in the 1988 Count Pack trial. Variety 0 Hours 1 Hour 24 Hours Comments A76147-2 A78242-5 SH-1 A79239-8 A79341-3 A79357-17 Shepody MN10874 A7411-2 A74114-4 NEA71.72-1 Russet Norkotah HiLite Russet Norking Russet ND671-4R Russet Burbank Krantz Norgold Russet 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1.5 1 1 1 1 1 1 1.5 1 1.0 1.5 1 1 1 1.5 1 1 1.5 empty table cell Yellowish Good Good Good Good empty table cell empty table cell empty table cell empty table cell Dark streaks Very good Good empty table cell empty table cell Very good Very good empty table cell 1.5 1 1 1 1 1 1 1.5 1.5 1.0 2 1 1 1.5 1.5 1 1 1.5 *Rating based on a scale of 1-5; 1 = no darkening, 5 = severe darkening (black). Table 8. Blackspot susceptibility of 1988 Count Pack varieties. Artificially Bruised Artificially Bruisedy y Check Varietyx A76147-2 A78242-5 SH-1 A79239-8 A79341-3 A79357-17 Shepody MN10874 A7411-2 A74114-4 NEA71.72-1 Russet Norkotah HiLite Russet Norking Russet ND671-4R Russet Burbank Krantz Norgold Russet Percent of Tubers with Blackspot Severity z Percent of Tubers with Blackspot Check Severity 30 35 20 - 15 35 30 55 35 15 35 5 5 5 15 30 5 15 0.30 0.45 0.20 - 0.15 0.50 0.40 1.35 0.90 0.15 0.55 0.05 0.05 0.05 0.15 0.50 0.05 0.20 0 10 5 20 5 5 0 5 15 5 5 0 0 0 0 5 0 0 0 0.15 0.05 0.20 0.05 0.05 0 0.25 0.30 0.05 0.25 0 0 0 0 0.05 0 0 XVarieties are arranged according to U.S. #1 tuber yield in the 1988 Count Pack trial. yTubers removed from 40°F storage and bruised artificially with 10 revolutions in a wooden drum and peeled 48 hours later. zBlackspot bruises per tuber. Table 9. Yield of Red Varieties — Montcalm Research Farm — 1988 (119 days). Yield (cwt/a) Yield (cwt/a) U.S. No. 1 Total Percent Size Distribution U.S. No. 1 Percent Size Distribution <4 oz. Percent Size Distribution 4-10 oz. Percent Size Distribution >10 oz. Percent Size Distribution Pick Outs Specific Gravity Maturity 515 420 412 409 400 388 377 372 352 345 320 291 383 577 447 468 446 465 438 481 424 399 398 401 394 445 89 94 88 92 86 89 79 88 88 87 80 74 86 5 5 9 8 8 11 21 12 8 11 19 24 64 74 75 83 66 85 77 83 70 84 78 71 6 1 3 0 6 0 0 0 4 2 1 2 empty table cell 25 20 13 9 20 4 2 5 18 3 2 3 1.066 1.067 1.058 1.061 1.060 1.060 1.072 1.063 1.068 1.074 1.073 1.054 1.065 4.5 4.5 4.5 3.0 4.0 3.0 3.5 3.5 4.0 5.0 3.5 3.5 empty table cell empty table cell empty table cell empty table cell Variety Red LaSoda W949-R NDT9-1068-11R ND791-5R Reddale ND2224-5R Rose Gold Sangre Rideau W948-R Red Gold MN12945 AVERAGE Maturity: 1 = early; 5 = very late maturity. CV (U.S. No. 1) = 16.7%. Planting Date: May 4, 1988. Harvest Date: August 30, 1988. Table 10. After cooking darkening* of Red-Skinned potato varieties in 1988. Variety 0 Hours 1 Hour 24 Hours Red LaSoda W949-R NDT91068-11R ND791-5R Reddale ND2224-5R Rose Gold Sangre Rideau W948-R Red Gold MN12945 1 1 1 1 1 1 1 1 1.5 1 1 1 1.5 2 1 1.5 1 3 1 1 2 1 2 1.5 1.5 2 1 1.5 1 3.5 1 1 2 1 2 1.5 Comments empty table cell All 3 slightly dark Good 1 dark Good All 3 very dark Good Good Dark ends Good All 3 slightly dark empty table cell *Rating based on a scale of 1-5; 1 = no darkening, 5 = severe darkening (black). Table 11. Blackspot susceptibility of 1988 Red-Skinned varieties. Artificially Bruisedy Artificially Bruised y Check Percent of Tubers with Blackspot Severity z Percent of Tubers with Blackspot Check Severity 10 20 5 5 10 25 10 10 15 45 35 5 0.15 0.25 0.05 0.05 0.15 0.25 0.10 0.10 0.15 0.95 0.55 0.05 0 5 5 10 0 5 5 0 10 0 5 0 0 0.05 0.05 0.10 0 0.05 0.05 0 0.10 0 0.05 0 Varietyx Red LaSoda W949-R NDT9-1068-11R ND791-5R Reddale ND2224-5R Rose Gold Sangre Rideau W948-R Red Gold MN12945 xVarieties are arranged according to U.S. #1 tuber yield in the 1988 trial. yTubers removed from 40°F storage and bruised artificially with 10 revolutions in a wooden drum and peeled 48 hours later. zBlackspot bruises per tuber. Table 12. Tuber yield, size distribution and specific gravity of potato varieties in the Upper Peninsula — 1988. Yield (cwt/a) Yield (cwt/a) U.S. No. 1 Total Percent Size Distribution U.S. No. 1 Percent Size Distribution Percent Size Distribution Percent Size Distribution Percent Size Distribution <2" 2-3 1/4" >3 1/4" Pick Outs Specific Gravity Variety A76147-2 A79341-3 A78242-5 MN10874 A7411-2 Shepody A79239-8 ND671-4 Norking Russet HiLite Count Michigold Russet Burbank A74114-4 MS716-15 MS700-83 Russet Norkotah A79357-17 Krantz AVERAGE 475 415 383 366 340 324 324 309 306 303 301 297 294 294 276 270 263 232 228 316 492 441 395 383 422 356 355 323 344 323 329 317 338 315 292 291 287 295 237 344 96 94 97 95 80 91 91 95 89 93 91 94 89 93 94 93 91 78 96 2 3 3 5 2 3 2 5 6 7 6 6 3 6 5 7 6 10 4 41 36 34 61 37 56 26 61 64 56 69 70 58 46 67 61 49 38 52 55 58 63 35 43 35 64 34 25 37 22 24 31 47 28 32 42 40 44 2 4 0 0 17 6 7 0 5 0 3 0 8 1 0 0 4 12 1 1.073 1.081 1.075 1.078 1.083 1.075 1.076 1.067 1.074 1.071 1.072 1.077 1.079 1.074 1.087 1.076 1.068 1.076 1.071 empty table cell 1.075 empty table cell empty table cell empty table cell empty table cell 1988 NORTH CENTRAL REGIONAL POTATO TRIALS Montcalm Experiment Station Location Michigan State University East Lansing, MI Fertilizer Treatment planter 500 lb/A sidedress 23 lbs N 6/28, 23 lbs N Date Harvested September 22, 1988 Spacing - Between Hills 12" Replications 4_____________________ 7/22 Soil Type Sandy Loam - McBride_____ 15-10-15 Date Planted May 4, 1988 Size of Plots 25' Spacing - Between Rows Number of Replications 34" 4 Environmental Factors (rainfall, temperature, irrigations, etc.): Ave. T. 5.1 16.3 20.1 26.5 22.3 15.3 empty table cell RF" 1.72 April 0.52 May 0.56 June 2.44 July 3.44 August 4.47 September Crop received 13.5" of irrigation water in 18 separate irrigations. Max. T. 11.1 23.1 27.9 29.6 28.7 21.6 Min. T. -0.2 7.9 11.4 17.9 16.3 9.2 Sprays Applied: Herbicides: Dual + Lexone - 1 application (5/20) Fungicides: Dithane Ridomil Bravo - 5 applications (6/29, 7/12, 7/26, 8/10, 8/26) - 2 applications (7/12, 7/26) - 3 applications (8/3, 8/19, 9/2) - 4 applications (6/29, 7/12, 8/3, 8/13) Insecticides: Imidan Other Data (vine killing, specific gravity, determinations, etc.): Thiodan - 1 application (8/10) Vine killing date: 9/8/88 (Diquat + X77). Specific gravity measured by weight in air and weight in water method. Extremely dry season but adequate irrigation water applied and no visible water stress was noticed. Previous crop, plowdown alfalfa. Table 13. North Central Regional Trial — 1988. SUMMARY SHEET Selection Number or Variety Aver. 1/ Mat. Most 2/ Representa­ tive Scab Area-Type CWT/A Aver. Yield CWT/A Aver. Yield US #1 Aver. Percent US #1 Aver. 3/ Total Solids EARLY TO MEDIUM MATURITY Norland Norgold Russet EARLY TO MEDIUM MATURITY Norchip EARLY TO MEDIUM MATURITY EARLY TO MEDIUM MATURITY MN13053 MN13056 EARLY TO MEDIUM MATURITY NEA 219-70-3 EARLY TO MEDIUM MATURITY MEDIUM LATE TO LATE MATURITY MN12823 MEDIUM LATE TO LATE MATURITY MS700-70 MEDIUM LATE TO LATE MATURITY MS716-15 NEA22.75-1 MEDIUM LATE TO LATE MATURITY NEA129.69-1 MEDIUM LATE TO LATE MATURITY MEDIUM LATE TO LATE MATURITY NDT9-1068-11R ND2224-5R MEDIUM LATE TO LATE MATURITY ND1215-1 MEDIUM LATE TO LATE MATURITY W855 MEDIUM LATE TO LATE MATURITY W1005 MEDIUM LATE TO LATE MATURITY Rose Gold MEDIUM LATE TO LATE MATURITY Red Potiac MEDIUM LATE TO LATE MATURITY 1.5 2.5 2.5 2.0 2.5 3.0 4.5 5.0 4.0 5.0 5.0 3.5 3.0 4.0 4.5 3.5 3.0 4.0 0 0 0 T-2 T-l 0 0 0 T-2 0 T-l 0 0 0 0 0 0 T-2 445 368 396 456 315 451 547 687 424 623 445 543 343 337 556 457 493 627 419 246 326 389 211 420 496 655 369 584 410 497 302 300 499 315 426 560 94 67 82 85 67 93 91 _ 95 87 94 92 91 88 89 90 69 86 89 15.0 16.2 18.4 16.0 16.7 17,3 16.0 19,7 20.1 17.1 18.0 15.0 15.2 15.0 19.7 19.0 18.0 15.4 *E-10 Agtron Colorimeter Chip 5/ Color Gen. 4/ Merit Rating empty table cell 50 empty table cell 38 empty table cell 62 empty table cell 43 empty table cell 51 empty table cell 64 empty table cell 1 5 3 58 empty table cell 63 67 35 empty table cell 56 42 54 empty table cell 60 70 empty table cell 58 empty table cell 43 empty table cell 30 2 4____ Early 6/ Blight Reading Comments and General Notes 4.0 4.5 4.0 4.0 4.0 4.5 4.5 5.0 4.5 5.0 5.0 4.0 4.0 4.0 5.0 4.5 4.0 4.5 Few off-shape Nice type, early sprouting Few pointed ends Tubers have scurf High % small tubers Deep eyes on both ends Variable shape Some EB rot in tubers Good type, uniform Good type empty table cell Good type, uniform Good type, EB in tubers Severe IBS empty table cell Variable shape, small tubers empty table cell Poor appearance 1/ 1-Very Early-Norland maturity; 2-Early-Irish Cobbler maturity; 3-Medium-Red Pontiac maturity; 4-Late-Katahdin maturity; 5-Very Late-Kennebec or Russet Burbank maturity 2/ AREA - T-less than 1%; 1-10-20%; 2-21-40%; 3-41-60%; 5-81-100%. TYPE - 1. Small, superficial; 2. Larger, superficial; 3. Larger, rough pustules; 4. Larger pustules, shallow holes; 5. Very large pustules, deep holes. 3/ Percent total solids, not total solids/acre 4/ Place top five among all entries including check varieties; disregard maturity classification. (Rate first, second, third, fourth and fifth (in order) for overall worth as a variety). 5/ Chip Color - PCII Color Chart or Agtron. Indicate what Agtron you are using. Agtron E-10 6/ Early Blight 1 unresistable 5 highly resistant Table 14. North Central Regional Trial — 1988. Percent External Percent External Selection Number or Variety_________ Defects (1) Scab (3) Defects (1) Growth Cracks EARLY TO MEDIUM MATURITY 0 Norland 0 Norgold Russet EARLY TO MEDIUM MATURITY 0 EARLY TO MEDIUM MATURITY Norchip 0 MN 13053 EARLY TO MEDIUM MATURITY 0 MN 13056 EARLY TO MEDIUM MATURITY NEA 219-70-3 0 0 EARLY TO MEDIUM MATURITY 0 0 0 4 4 SUMMARY OF GRADE DEFECTS Percent External Defects (1) Off Shape and Second Growth Percent External Defects (1) Sun Green Percent External Defects (1) Tuber Rot Total (4) Tubers Free of External Defects Percent Internal Percent Internal Percent Internal Percent Internal Defects Defects (2) Hollow Heart Defects (2) Internal Necrosis Defects (2) Vascular Discoloration (2) Normal tubers (5) 8 0 0 0 0 0 0 0 0 10 4 0 0 0 0 0 0 0 92 100 100 86 92 100 20 5 0 5 0 25 slight 0015 slight 0 0 0 5 slight 0 0 0 0 0 75 95 75 85 100 95 MEDIUM LATE TO LATE MATURITY 75 0 MN12823____________ 0 2020 60 MEDIUM LATE TO LATE MATURITY MS700-70________ 90 0 MS716-15___________ MEDIUM LATE TO LATE MATURITY 75 0 MEDIUM LATE TO LATE MATURITY NEA22.75-1 80 0 MEDIUM LATE TO LATE MATURITY NEA129.69-1 75 0 NDT9-1068-11R MEDIUM LATE TO LATE MATURITY 75 5 _ ND2224-5R MEDIUM LATE TO LATE MATURITY 30 0 ND1215-1___________ MEDIUM LATE TO LATE MATURITY 55 0 W855________________ MEDIUM LATE TO LATE MATURITY 90 5 MEDIUM LATE TO LATE MATURITY W1005 75 0 Rose Gold MEDIUM LATE TO LATE MATURITY 70 0 Red Pontiac MEDIUM LATE TO LATE MATURITY (1) Based on four 25 tuber samples (one from each replication). Percentage based on number of tubers 25 slight 10 _____ 25 slight 20 slight 25 slight 20 slight 0 40 slight 5 slight 25 slight 30 slight 100 92 96 96 90 92 76 100 96 0 0 90 0 0 0 4 0 4 4 0 4 0 0 0 0 8 0 0 5 0 20 0 0 0 0 0 0 0 0 0 0 0 70 5 0 0 0 0 0 4 0 5 0 0 0 0 0 0 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4 0 0 0 0 0 0 (2) Based on four 25 tuber samples (one from each replication). Percentage based on number of tubers (3) Includes all tubers with scab lesions whether merely surface, pitted or otherwise and regardless of area. Be sure to count tubers with any amount of scab in this category (4) This total - tubers free from an external defect of any sort (5) Percentage normal tubers are those showing no internal defects. Some individual tubers will have more than one type of internal defect. Table 15. After cooking darkening* of potato varieties in the 1988 North Central Regional trial. Variety 0 Hours 1 Hour 24 Hours Comments MN13053 NEA219.70-3 MS700-70 W855 Norgold Russet Red Pontiac MN12823 Norchip MS716-15 ND2224-5R NDT9-1068-11R Rose Gold Norland W1005 MN13053 NEA22.75-1 ND1215-1 1.0 1 1 1 1 1 1.5 1 1 1.5 1.5 1 1 1 1 1.5 1.5 1.0 1.5 1 1 1.5 1.5 1.5 1 1 3 2 1 1.5 1.5 1.5 2.0 2.5 1.0 2.0 1 1.5 1.5 1.5 1.5 1.5 1 3.5 2 1.5 1.5 1.5 1.5 2.0 3.0 Good empty table cell Good empty table cell empty table cell empty table cell empty table cell empty table cell Very good All 3 very dark empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell All 3 dark *Rating based on a scale of 1-5; 1 = no darkening, 5 = severe darkening (black). Table 16. Blackspot susceptibility of 1988 North Central Regional trial varieties. Artificially Bruisedy Artificially Bruised y Check Percent of Tubers with Blackspot Severityz Percent of Tubers with Blackspot Check Severity 15 5 10 30 5 0 10 15 0 10 10 0 5 25 0 0 10 0.15 0.05 0.10 0.45 0.05 0 0.10 0.15 0 0.10 0.10 0 0.05 0.25 0 0 0.10 — 15 5 15 0 0 0 10 0 15 0 0 0 10 0 0 10 — 0.15 0.05 0.15 0 0 0 0.10 0 0.15 0 0 0 0.10 0 0 0.10 Variety MN13056 NEA219.70-3 MS700-70 W855 Norgold Russet Red Pontiac MN12823 Norchip MS716-15 ND2224-5R NDT9-1068-UR Rose Gold Norland W1005 MN13053 NEA22.75-1 ND1215-1 yTubers removed from 40°F storage and bruised artificially with 10 revolutions in a wooden drum and peeled 48 hours later. zBlackspot bruises per tuber. Table 17. Tuber yield from Advanced Adaptation Lines — Montcalm Research Farm — 1988 (126 days). Yield (cwt/a) Yield (cwt/a) U.S. No. 1 Total Percent Size Distribution Percent Size Distribution Percent Size Distribution Percent Size Distribution U.S. No. 1 <2” 2-3 1/4" >3 1/4" Percent Size Distribution Pick Outs Specific Gravity Chip Color Maturity Variety BR7093-24 Atlantic ND1859-3(y) NYD164-9 AF875-16 ND2330-3 D195-24 D2109-7 ND2107-l(y) AVERAGE 559 467 432 409 361 350 324 254 245 377 600 513 469 479 405 402 400 317 344 439 93 91 92 85 89 87 81 80 71 85 4 7 7 13 9 12 17 19 28 30 13 10 10 5 4 5 0 1 empty table cell 3 2 1 2 2 1 2 1 1 empty table cell 63 78 82 75 84 83 76 80 70 Planting Date: May 4, 1988. Harvest Date: September 6, 1988. 67 69 60 64 66 60 64 70 66 1.073 1.083 1.075 1.082 1.089 1.076 1.082 1.080 1.077 1.080 4.0 4.0 3.5 4.0 3.5 3.0 3.5 3.0 3.0 empty table cell empty table cell empty table cell empty table cell Table 18. After cooking darkening* of potato varieties in the 1988 Advanced Adaptation trial. Variety 0 Hours 1 Hour 24 Hours Comments NYD164-9 ND2330-3 D195-24 ND1859-3(y) BR7093-24 Atlantic ND2107-l(y) ND2109-7 AF875-16 1 1 1 1 1 1 1 1 1.5 1 1 1 2 1.5 2 1 2 1.5 1 1 1.5 3 1.5 2 1 2.5 2.5 Good Good empty table cell 3 dark ends empty table cell 3 dark ends Good 3 dark stem ends 2 dark ends *Rating based on a scale of 1-5; 1 = no darkening, 5 = severe darkening (black). Table 19. Blackspot susceptibility of 1988 Advanced Adaptation trial varieties. Artificially Bruisedy Artificially Bruised y Check Percent of Tubers with Blackspot Severity z Percent of Tubers with Blackspot Check Severity 65 70 30 50 35 25 25 50 30 1.00 1.00 0.40 0.90 0.60 0.25 0.30 0.65 0.65 5 20 5 10 10 25 5 10 15 0.05 0.20 0.05 0.10 0.10 0.25 0.05 0.10 0.15 Variety NYD164-9 ND2330-3 D195-24 ND1859-3(y) BR7093-24 Atlantic ND2107-l(y) ND2109-7 AF875-16 yTubers removed from 40°F storage and bruised artificially with 10 revolutions in a wooden drum and peeled 48 hours later. zBlackspot bruises per tuber. able 20. Tuber yield of MSU Advanced Lines — Montcalm Research Farm — 1988 (126 days). Yield (cwt/a) Yield (cwt/a) U.S. No. 1 Total Percent Size Distribution U.S. No. 1 Percent Size Distribution Percent Size Distribution Percent Size Distribution <2" 2-3 1/4" >3 1/4" Percent Size Distribution Pick Outs Internal Defects Internal Defects Internal Defects Internal Defects Specific Gravity Chip Color Maturity HH IBS # VD/cut 631 534 471 459 441 441 428 410 408 390 383 365 331 318 309 209 408 688 577 519 485 498 473 468 439 457 466 434 418 434 334 396 309 462 92 92 91 95 88 93 91 93 89 84 89 87 76 95 78 68 88 6 5 5 4 9 4 6 5 10 15 6 8 22 4 20 30 empty table cell 72 83 70 74 70 62 77 64 77 80 77 70 73 61 77 67 20 9 21 21 18 31 14 29 12 4 12 17 3 34 1 1 2 3 4 1 3 3 3 2 1 1 5 5 2 1 2 2 1.083 1.090 1.070 1.074 1.079 1.082 1.067 1.080 1.084 1.081 1.074 1.080 1.078 1.069 1.073 1.066 1.077 53 60 51 61 60 63 48 60 64 69 52 65 60 56 66 50 5.0 4.0 3.5 3.0 3.0 4.0 2.5 3.5 4.0 3.0 3.0 3.0 2.5 3.0 2.5 2.0 5 1 23 5 10 0 0 11 4 0 19 7 7 0 3 10 empty table cell 22 4 14 0 10 4 0 31 10 4 6 8 0 3 0 4 19/40 0/28 0/30 8/39 7/34 7/40 9/40 5/40 4/31 0/16 2/30 9/40 1/9 0/30 0/4 5/11 empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell Variety MS401-5 MS401-7* MS402-1 MS402-7* MS401-3(y) MS401-2(y)* Onaway MS401-6 Atlantic MS401-l(y)* MS402-6 MS401-8(y)* MS401-4* MS402-8* MS402-2 MS402-4 AVERAGE Selected for further testing. Planting Date: May 4, 1988. Harvest Date: September 6, 1988. Table 21. After cooking darkening* of Michigan State University selections. Variety 0 Hours 1 Hour 24 Hours Comments MS401-1 MS401-2 MS401-4 MS401-7 MS 401-8 MS402-7 MS402-8 1.5 1 1 1 1 1 1 1.5 1 1.5 2 1.5 1 1 1.5 1 1.5 2.5 1.5 1 1 All 3 slightly dark Good empty table cell 1 severely dark, 2 slightly dark empty table cell Good Good *Rating based on a scale of 1-5; 1 = no darkening, 5 = severe darkening (black). Table 22. Blackspot susceptibility of 1988 Michigan State University selections. Artificially Bruisedy Artificially Bruised y Check Percent of Tubers with Blackspot Severityz Percent of Tubers with Blackspot Check Severity 15 10 40 25 10 30 5 0.15 0.10 0.65 0.50 0.10 0.55 0.05 0 5 0 5 10 0 0 0 0.05 0 0.05 0.10 0 0 Variety MS401-l(y) MS401-2(y) MS401-4 MS401-7 MS401-8(y) MS402-7 MS402-8 yTubers removed from 40°F storage and bruised artificially with 10 revolutions in a wooden drum and peeled 48 hours later. zBlackspot bruises per tuber. Funding Federal Grant Development of new potato cultivars specifically suited to Michigan’s fresh market and processing needs David S. Douches Crop and Soil Sciences Department Cooperators: R. Chase, G. Silva, R. Hammerschmidt, J. Cash Objective: The MSU potato variety improvement program's main objective is to develop and identify improved cultivars that will satisfy the needs of Michigan’s fresh market and processing industry. Justification: Michigan’s potato industry has become highly specialized and stringent marketing demands have forced growers to use specific varieties which are unpredictable because of serious production and storage limitations. Improved varieties are needed for chip processing with a higher dry matter content (19.5-21.5%) and less susceptibility to bruising and storage deterioration than the variety Atlantic. For fresh market use, there is a need for a disease resistant variety with a bright skin and smooth appearance for marketing from extended storage. The marketing of round white table stock potatoes has been very volatile and challenges of the immediate future must be met with improved raw product quality. It is essential that new varieties be developed and tested to meet the current and future needs. Methods and Procedures: The potato breeding program in the Crop and Soil Sciences Department has been reactivated in 1988 to develop improved cultivars specifically suited to Michigan. All variety and germplasm evaluations will focus on tuber appearance, size distribution, external and internal defects, specific gravity, chip color, storability, and culinary properties. Also of significant interest to Michigan is tolerance to scab (Streptomyces scabies) and bruising. Short-term goals (3-5 years) Adaptation trial: Twenty advanced lines from public breeding programs throughout the US and Canada were selected in 1988 for further evaluation at Montcalm and Clarksville Experiment Stations. In 1989, each line will be planted as 2x20 hill trials at both locations with check varieties. Only those that meet industry requirements will be selected for an advanced adaptation trial in 1990. Promising material will be maintained virus-free through tissue culture. Scab evaluation: Parental lines utilized in the MSU breeding program will be tested for their ability to confer resistance to common scab through a greenhouse bioassay developed by Dr. Ray Hammerschmidt. Advanced selections will be evaluated in the scab trial located at the Soils Farm at MSU. Mid-range goals (7-10 years) Evaluation of first-year seedlings: Approximately 10,000 seedlings derived from 100 segregating families generated at MSU will be screened at Clarksville. In addition, 5,000 seedling tubers obtained from USDA (Idaho and Beltsville) programs will be tested for adaption. Selections from this trial will be advanced to 4-hill plots in the following year. Advancement of first-vear seedlings: Single hills selected in 1988 will be tested as 4-hill plots at Montcalm and Clarksville. Further advancement will be based upon their performance in relation to check cultivars at both locations. Cultivated/Species hybrid (4x-2x) evaluations: Superior selections from the diploid exotic species have been hybridized to advanced selections and cultivars. These 4x-2x hybrid progenies (5,000 seedlings) will be grown at Clarksville to evaluate the breeding value of these diploid parents. In addition, superior hybrids will be advanced as 4-hill plots in the breeding program. Long-term goals (12-15 years) Evaluation of exotic germplasm: Plant introductions of various Solanum species (2n = 2x, 4x, and 6x) are to be evaluated for their ability to hybridize with the cultivated potatoes, to introgress disease resistances such as scab, fusarium, and virus along with tuber quality genes such as dry matter and low reducing sugars. Approximately 3,000 seedlings will be screened in 1989 and select hybrid families will be advanced for further evaluation. We expect to broaden our germplasm base with this genetic material. Research A biotechnological approach (RFLP analysis) is being tested to predict specific gravity in early rounds of selection and also to identify high specific gravity material in both cultivated and exotic germplasm. Biochemical and mechanical factors are being characterized in a series of breeding lines and cultivars to determine if correlations exist between these factors and the expression of scab resistance. The genetic basis of the factors and scab resistance are being evaluated through a diallel mating design. (Cooperator: R. Hammerschmidt) Research is being initiated to study the influence of genetic factors upon tuber reducing sugars (glucose and fructose) levels. Segregating families derived from a diallel mating are being evaluated. (Cooperator: J. Cash) The information gained from this research is being integrated into the breeding of new cultivars through (1) the development of superior parental germplasm and (2) the development and utilization of efficient assays to select superior lines that express these economic traits that the industry needs. Funding Federal Grant EVALUATION OF PRODUCTION MANAGEMENT INPUTS TO IMPROVE QUALITY AND YIELD OF RUSSET NORKOTAH AND MS700-70 G.H. Silva, R.W. Chase and R.B. Kitchen Russet Norkotah has potential in Michigan for the count pack market because of its high percentage of U.S. No. l’s and its smooth appearance. Under standard cultural practices in Michigan, it has a tendency to produce a higher percent of undersized tubers. MS700-70 is a round white, late maturing variety with high gravity and prolific yields. It has chipping potential in Michigan. The management practices recommended for new releases are generally based on standard practices adapted for commonly grown cultivars. In 1988, the optimum nitrogen and spacing requirements of Russet Norkotah and MS700-70 were studied using 3 levels of nitrogen (100, 150 and 200 lbs/a) and 3 within row spacings (6, 9 and 12”). The treatments were studied in a split-plot design with 4 replications. In addition to determining the nitrogen and spacing requirements for optimizing tuber quality, the cost/revenue analysis of each treatment combination was determined. The trial was planted on May 5. The previous crop was alfalfa and the plowdown alfalfa residue was credited with 75 lbs N/a to the potato crop. The basal fertilizer application with the planter was 500 lbs/a 5-10-15 mixture. For treatments receiving 150 lbs N, a topdressing of urea containing 50 lbs N/a was applied on June 15. For treatments receiving 200 lbs N/a, another topdressing of urea containing 50 lbs N/a was applied on July 5. Petioles for nitrogen analysis were taken on August 4. Russet Norkotah was harvested on August 30 and MS700-70 on September 28. Results Russet Norkotah - The results are summarized in Tables 1, 2 and 3. The N effect on tuber yield was not significant but the spacing effect was highly significant (Table 1). The highest tuber yield was obtained at 150 lbs N and 6” spacing. Excellent U.S. #1 yields were obtained at 6” spacing and at all 3 N levels. The percent tubers under 4 oz. size ranged from 15-17%. At higher N and spacing levels there was an increase in the oversized (>10 oz.) tubers. Although N rates produced no response in tuber yield, there was a significantly higher uptake of N in the petioles at higher N rates. This constitutes luxury consumption of N. Higher N levels were also associated with slight decreases in specific gravity. Nitrogen uptake significantly increased at wider spacings. Post harvest evaluations (Table 2) indicated that nitrogen and spacing treatments had no significant effects on after cooking darkening and blackspot. Nitrogen and seed costs/revenue per acre analysis (Table 3) indicated that 150 lbs/N and 6” spacing were the most economical for Russet Norkotah. MS700-70 - These results are summarized in Tables 4, 5 and 6. There was no response to nitrogen treatments, but the response to spacing was highly significant (Table 4). The highest tuber yields were obtained at 6" spacing. As in previous years, prolific yields and higher specific gravities were produced in 1988. At wider spacings, MS700-70 produced a very high percent of oversized tubers. Although N levels produced no significant effects on tuber yield, there was luxury consumption of N in the petioles. Higher N levels decreased the specific gravity of tubers. Post harvest evaluations (Table 5) indicated that nitrogen and spacing levels in the test produced no significant differences in chip color, after cooking darkening and blackspot. Nitrogen and seed costs/revenue per acre analysis (Table 6) indicated that the highest net revenues are obtained at 6” spacings. In summary, both varieties produced no responses to nitrogen rates but showed significant yield increases at 6” spacing. This field had alfalfa in the previous year and it is possible that alfalfa contributed a large share of nitrogen requirements and perhaps in a slow release form to render further applications of N ineffective. Russet Norkotah produced high U.S. No. 1 yields with a smooth appearance and showed excellent potential for count pack fresh market. It has excellent culinary properties and blackspot resistance. MS700-70 produced prolific yields with high specific gravity and good chip color. In Michigan, it is late maturing but has potential as a chipper. Table 1. Russet Norkotah — Management Profile — Montcalm Research Farm — 1988 (118 days). Yield (cwt/a) Yield (cwt/a) Nitrogen (lbs/a) Spacing (inches) U.S. No. 1 Total U.S. No. 1 Percent Size Distribution Percent Size Distribution <4 oz. Percent Size Distribution 4-6 oz. Percent Size Distribution 6-10 oz. Percent Size Distribution >10 oz. Percent Size Distribution Pick Outs Specific Gravity Petiole N % 150 200 100 100 100 200 150 200 150 6 6 6 9 12 9 12 12 9 AVERAGEAVERAGE Nitrogen Effects empty table cell 435 393 388 377 360 358 354 348 327 371 (ns)(ns) 100 150 200 empty table cell 375 empty table cell372 empty table cell366 528 491 479 468 416 419 413 413 407 447 454 449 441 empty table cell Spacing Effects empty table cell6 empty table cell9 empty table cell12 (*) (*) 405 354 352 499 431 414 81 82 86 16 13 11 19 16 17 43 40 38 19 26 31 3 5 3 (ns) 1.069 1.067 1.068 15 17 17 13 12 12 11 11 14 19 23 16 16 15 16 22 14 16 empty table cell 3 3 2 6 1 3 3 5 6 empty table cell 45 32 52 44 38 39 40 35 37 18 25 13 21 34 30 24 35 27 82 80 81 81 87 85 86 84 80 83 empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell 83 83 83 16 19 18 empty table cell empty table cell 3 4 4 empty table cell empty table cell 22 23 30 45 41 35 14 13 13 empty table cell empty table cell 1.069 1.067 1.070 1.068 1.069 1.068 1.068 1.066 1.066 1.067 (ns) 1.069 1.068 1.067 3.08 3.56 2.49 2.70 3.22 3.42 3.38 3.64 3.31 3.20 (*) 2.80 3.25 3.54 (*) 3.04 3.15 3.41 Table 2. Post Harvest Evaluations — Russet Norkotah. Nitrogen Spacing After Cooking Darkening y Percent Blackspot Blackspot Percent Bruisedz Check 100 100 100 150 150 150 200 200 200 6 9 12 6 9 12 6 9 12 1 1 1 1 1 1 1.5 1 1 0 5 0 10 0 0 0 0 0 10 0 5 15 0 0 10 15 10 yRating based on a scale of 1-5; 1 = no darkening, 5 = severe darkening (black) 1 hour after boiling. zTubers removed from 40°F storage and bruised artificially with 10 revolutions in a wooden drum and evaluated after 48 hours. Table 3. Management Profile — Russet Norkotah — Nitrogen and Seed Costs and Revenue/Acre (118 days). N Applied (lbs/a) N + Application Cost ($) Spacing (inches) Seed Cost ($) N + Seed Cost ($) Yield (cwt/a) Gross Revenue ($) NET ($) 150 200 100 100 100 200 150 200 150 38 52 24 24 24 52 38 52 38 6 6 6 9 12 9 12 12 9 261 261 261 174 131 174 131 131 174 299 313 285 198 155 226 169 183 212 435 393 388 377 360 358 354 348 327 2,861.76 2,614.58 2,553.07 2,513.16 2,423.20 2,377.83 2,358.23 2,327.26 2,171.35 2,562.76 2,301.58 2,268.07 2,315.16 2,268.20 2,151.83 2,189.23 2,144.26 1,959.35 Nitrogen 100, 150 and 200 lbs/a applied in 1, 2 and 3 applications, respectively. Nitrogen cost = $0.20/lb. Cost per application = $4.00/a. Seed cost = $7.00/cwt. Revenue on the basis of $6.50/cwt for tubers 2-3 1/4" and $7.00 for >3 1/4". Table 4. MS700-70 — Management Profile — Montcalm Research Farm — 1988 (148 days). Nitrogen (lbs/a) Spacing (inches) Yield (cwt/a) Yield (cwt/a) U.S. No. 1 Total Percent Size Distribution Percent Size Distribution Percent Size Distribution Percent Size Distribution U.S. No. 1 <2" 2-3 1/4" >3 1/4" Percent Size Distribution Pick Outs Specific Gravity Petiole N % 100 200 150 150 200 100 150 200 100 6 6 6 9 9 9 12 12 12 AVERAGE AVERAGE 561 545 533 509 499 495 456 454 445 499 604 600 570 547 524 523 505 496 481 539 93 91 94 93 95 95 90 92 93 93 7 7 5 6 4 5 6 6 5 13 24 26 31 32 30 33 33 25 empty table cell 0 2 1 1 1 0 4 2 2 empty table cell 80 67 68 62 63 65 57 59 68 empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell 1.083 1.078 1.081 1.079 1.077 1.081 1.081 1.077 1.081 1.080 (*) 1.081 1.080 1.078 2.53 3.66 3.11 3.24 3.75 2.56 3.31 3.74 2.39 3.42 (*) 2.49 3.22 3.72 (ns) 3.10 3.16 3.16 Nitrogen Effects empty table cell empty table cell500 empty table cell500 empty table cell499 100 150 200 (ns)(ns) empty table cellSpacing Effects empty table cell6 empty table cell9 empty table cell12 (*)(*) 546 501 452 536 541 540 591 532 494 93 92 92 72 62 63 empty table cell 21 30 29 empty table cell 1 2 2 empty table cell 6 6 4 empty table cell empty table cell 92 94 92 6 5 6 71 63 61 21 31 31 1 1 2 (ns) 1.080 1.079 1.079 Table 5. Post Harvest Evaluations — MS700-70 Nitrogen Spacing Chip Color (lbs/a) (inches) 100 100 100 150 150 150 200 200 200 6 9 12 6 9 12 6 9 12 60 62 58 59 60 63 58 59 60 After Cookingy Darkening Percent Blackspot Percent Blackspot Check Bruisedz 1 1 1 1 1 1 1 1 1 5 0 0 10 5 0 0 0 0 15 30 15 10 40 20 25 30 15 y Rating based on a scale of 1-5; 1 = no darkening, 5 = severe darkening (black) 1 hour after boiling. zTubers removed from 40°F storage and bruised artificially with 10 revolutions in a wooden drum and evaluated after 48 hours. Table 6. Management Profile — MS700-70 — Nitrogen and Seed Costs and Revenue/Acre (148 days). N Applied (lbs/a) N + Application Cost ($) Spacing (inches) Seed Cost ($) N + Seed Cost ($) Yield (cwt/A) Gross Revenue ($) NET ($) 100 200 150 150 200 100 150 200 100 24 52 38 38 52 24 38 52 24 6 6 6 9 9 9 12 12 12 261 261 261 174 174 174 131 131 131 285 313 299 212 226 198 169 183 155 561 545 533 509 499 495 456 454 445 3,648.16 3,363.16 3,621.00 3,308.00 3,556.80 3,257.80 3,391.40 3,179.40 3,319.54 3,093.54 3,307.98 3,109.98 3,037.58 2,868.58 3,047.92 2,864.92 2,967.77 2,812.77 Nitrogen 100, 150 and 200 Ibs/a applied in 1, 2 and 3 applications, respectively. Nitrogen costs = $0.20/lb. Cost per application = $4.00/a. Seed cost = $7.00/cwt. Revenue on the basis of $6.50/cwt for tubers 2-3 1/4" and $7.00 for >3 1/4". Funding Federal Grant EFFECTS OF POTASSIUM RATE AND SOURCE ON YIELD AND QUALITY OF NORCHIP AND MS700-83 G.H. Silva, R.W. Chase and R.B. Kitchen The effects of 2 sources (muriate of potash and potassium sulfate) and 4 levels of K (0, 100, 200 and 300 lbs K20) on specific gravity and culinary properties were investigated in 2 cultivars (Norchip and MS700-83). These 2 varieties were selected because of their chipping potential but their marginal specific gravities are frequently a major limitation in Michigan. The objective was to find out if the specific gravity could be increased with reduced K use or using alternate K sources. All K was applied broadcast with a Gandy applicator before planting. The previous crop was alfalfa. The initial soil test showed 270 lbs K and a pH of 6.0. For a yield goal of 450 cwt/a, the recommendation was to apply another 150 lbs K20/a. Both varieties received 175 lbs N and 50 lbs P205. The treatments were tested in a randomized complete block design with 4 replications. Petioles for nutrient analysis were taken on August 4. The trial was planted on May 6 and harvested on September 22. The results obtained from Norchip and MS700-83 are summarized in Tables 1 and 2, respectively. The data indicated that in both varieties, the highest specific gravities were obtained in treatments where no K was applied. Specific gravity decreased with increasing rates of K, but the decrease observed with muriate source was more profound compared to the sulphate source. In Norchip, the specific gravity at 0 K20 was 1.077, at 300 lbs/a K20 as sulfate was 1.073 and at 300 lbs/a K20 as muriate was 1.070. In MS700-83, the specific gravity at 0 K20 was 1.076, at 300 lbs/a K20 as sulfate it was 1.074 and at 300 lbs/a K20 as muriate, 1.068. There was a significant increase in the uptake of K in the petioles in K treated plots compared to untreated. No significant yield increases were obtained due to higher K applications. Potassium source or rate did not significantly effect the chip color. Post harvest evaluations in Norchip (Table 3) indicated that K rate or source produced no significant differences in after cooking darkening and susceptibility to blackspot. Similar results were obtained with MS700-83 (Table 4) . Although a slightly higher tendency for after cooking darkening with the sulfate source was observed on the first boiling date (December 20), this effect was not evident at the second boiling date (January 4). Based on this study, it appears that using more potassium than the recommendations from a soil test may lead to decreases in specific gravity. With 270 lbs K in the soil before the test, further additions of K resulted in a decrease in specific gravity with no yield response. Most of the K applied to potatoes in Michigan is in the form of muriate. This study confirms the previously reported view that excess chloride could interfere with the efficiency of the plant photosynthetic system. A potential exists to increase dry matter by using an alternative K source such as sulfate if the increase in cost can be justified. This study will be repeated in 1989. Table 1. Effects of Potassium Rate and Source on Yield and Quality of Norchip — Montcalm Research Farm — 1988 (139 days). Yield Yield (cwt/a) (cwt/a) Percent Size Distribution Percent Size Distribution Percent Size Distribution Percent Size Distribution U.S. No. 1 Total U.S. No. 1 <2" 2-3 1/4" >3 1/4" Percent Size Distribution Pick Outs Specific Gravity Chip Color 520 498 473 464 489 460 433 477 464 479 464 475 482 464 481 490 466 80 82 85 84 79 82 78 81 84 81 84 81 81 84 81 81 80 6 7 7 7 7 6 7 7 7 7 7 7 6 7 7 6 7 68 72 74 73 64 69 62 69 73 68 73 68 69 63 69 70 67 12 10 11 11 15 13 16 12 11 13 11 13 12 11 13 11 13 14 11 8 9 14 12 15 12 9 12 9 12 12 9 11 13 12 1.072d 1.073cd 1.073cd 1.077a 1.075b 1.074bc 1.070e 1.073 1.077a 1.073b 1.077a 1.072c 1.075b 1.077a 1.074b l.073bc 1.072c 62 58 65 63 60 60 62 62 63 61 63 63 59 63 63 61 60 Source/K20 KCl/200 K2S04/300 KCl/100 Check K2SO4/lOO K2SO4/200 KCl/300 AVERAGE Check vs. K Check +K Check vs. K 417 408 400 392 384 376 337 388 392 387 Check vs. K Source 392 Check 385 Check vs. K Source KCL Check vs. K 389 source K2SO4 Check vs. K Amount 392 Check K (100) Check vs. K Amount 392 K (200) Check vs. K Amount 397 K (300) Check vs. K Amount 373 Percent Petiole Percent Petiole N K 3.60 3.51 3.46 3.79 3.66 3.40 3.31 3.53 9.3a 9.7a 9.2a 7.6b 9.0a 9.6a 9.7a 9.2 3.79 3.49 7.6b 9.4a 3.79 3.46 3.52 7.6b 9.4a 9.4a 3.79 3.56 3.50 3.41 7.6b 9.1a 9.5a 9.7a le 2. Effects of Potassium Rate and Source on Yield and Quality of MS700-83 — Montcalm Research Farm — 1988 (139 days). Yield (cwt/a) Yield (cwt/a) Percent Size Distribution Percent Size Distribution Percent Size Distribution Percent Size Distribution Percent Size Distribution U.S. No. 1 Total U.S. No. 1 <2" 2-3 1/4" >3 1/4" Pick Outs Specific Gravity Chip Color Percent Percent Petiole Petiole N K 3.16 10.9b 3.30 11.4ab 3.38 9.1c 3.37 10.8b 3.32 11.6ab 12.2a 3.10 3.14 ll.9ab 3.25 11.1 3.38 3.23 9.1b 11.5a 3.38 3.13 3.33 9.1b 11.7a 11.3a 3.38 3.27 3.22 3.21 9.1b 10.9a 11.7a 11.9a rce/K2O /l00 O4/200 ck O4/100 O4/300 /300 /200 AVERAGE ck vs. K Check ck vs. K +K ck vs. K Source Check ck vs. K Source KCL ck vs. K Source K2SO4 ck vs. K Amount Check K (100) ck vs. K Amount K (200) ck vs. K Amount K (300) ck vs. K Amount 514 496 491 485 485 474 435 482 491 482 491 474 488 491 499 465 479 564 547 530 537 533 514 478 529 530 528 530 518 539 530 550 512 523 91 91 92 90 91 92 91 91 92 91 92 91 91 92 91 91 92 8 8 6 9 7 7 7 15 17 18 13 18 14 16 empty table cell 76 74 74 77 73 78 75 1 1 2 1 2 1 2 1.073b 1.074b 1.076a 1.076a 1.074b 1.068d 1.070c 1.073 empty table cell empty table cell empty table cell 6 8 6 7 8 6 9 8 7 74 76 74 76 75 74 77 75 75 18 16 18 15 16 18 14 17 16 2 1 2 1 1 2 1 2 2 1.076a 1.072b 1.076a 1.070b 1.075a 1.076a 1.075ab 1.072bc 1.071c 59 56 59 56 55 59 60 58 59 58 59 59 56 59 58 58 57 Table 3. Post Harvest Evaluations — Norchip. Source/K2O Check KC1/100 KC1/200 KC1/300 K2SO4/100 K2SO4/200 K2SO4/300 After Cooking Darkeningy 12/20/88 Percent Blackspot Percent Blackspot Check Bruised z 1 1 1 1 1 1 1 10 5 10 5 10 10 0 15 50 15 15 40 35 10 yRating based on a scale of 1-5; 1 = no darkening, 5 = severe darkening (black) 1 hour after boiling. zTubers removed from 40°F storage and bruised artificially with 10 revolutions in a wooden drum and evaluated after 48 hours. Table 4. Post Harvest Evaluations — MS700-83. Source/K2O Check KC1/100 KC1/200 KC1/300 K2SO4/100 K2SO4/200 K2SO4/300 After After Cooking Darkening Cooking Darkeningy 12/20/88 1/4/89 y Percent Blackspot Percent Blackspot Check Bruisedz 1.3 1.0 1.3 1.2 1.7 1.7 2.2 1.5 1.5 1.0 1.5 1.0 1.0 1.5 0 5 0 5 5 5 0 10 25 5 10 5 5 15 yRating based on a scale of 1-5; 1 = no darkening, 5 = severe darkening (black) 1 hour after boiling. zTubers removed from 40°F storage and bruised artificially with 10 revolutions in a wooden drum and evaluated after 48 hours. Funding _______MPIC NITROGEN MANAGEMENT STRATEGIES FOR RUSSET BURBANK POTATOES B.C. Joern, M.L. Vitosh, D.A. Hyde, D. Duncan, and B.P. Darling Introduction Nitrate contamination of groundwater from non-point sources has developed into a serious and well publicized environmental issue. The present potato production system is quite susceptible to nitrate leaching because potatoes are a shallow rooted crop grown mainly on coarse-textured soils under irrigation. The relatively high economic value of the crop has historically led to an excessive use of fertilizer nitrogen (N) and irrigation water, which further contributes to the nitrate leaching potential of the potato production system. There is a need to develop N management strategies for potatoes that will improve their N use efficiency and reduce their nitrate leaching potential. The primary objective of this study was to evaluate several N management strategies for their ability to reduce residual N in the soil profile after harvest (thereby reducing nitrate leaching potential) without reducing crop quality or yield. Procedure This study was initiated in 1986 at the Montcalm Research farm on a Montcalm-McBride sandy loam soil. A three year rotation sequence of potatoes-rye-corn-rye was established. The experimental design selected for this study was a randomized complete block with four replications. Six N management practices (combinations of N rates and application times) were used as treatments for this investigation. Russet Burbank was the potato cultivar used. Ammonium sulfate, (NH4)2SO4, was the fertilizer N source applied to the crop. 15N depleted ammonium sulfate was applied on approximately 50 percent of each plot to determine fertilizer N uptake and N use efficiency. Soil samples were taken to a depth of four feet four times during the growing season in the potato experiment. The soil samples were analyzed for nitrate and ammonium so that N movement could be followed through the profile during the growing season. Suction lysimeters were installed in treatment five at a depth of three feet to monitor N levels in the soil water under this high N treatment. In 1988, corn was grown in the 1987 potato area at location 1 without the addition of any fertilizer or irrigation water, to determine the crop’s ability to remove any residual N left in the soil from the previous potato crop. In 1988, potato studies were conducted at the Montcalm Research farm (location 1) and on a producer's field (location 2). 1988 Results The potato yield data for locations 1 and 2 are shown in Tables 1 and 2, respectively. For location 1, total yield and large tuber yields were influenced by the N management treatments. From this data it appears that 120-180 lb of N applied by the end of tuber set (late June) was sufficient for optimum yields. No beneficial effects were observed by splitting the N applications in 1988. The tuber yields at location 2 were much higher than at location 1, but no significant treatment effects were observed due to the large variability in yields within each treatment. Potato tuber quality, as indicated by specific gravity, was not significantly affected by the N treatments at either location. The percent N in petiole samples taken throughout the growing season and percent N in whole plant and tubers at physiological maturity and harvest are presented in Tables 3 and 4 for location 1, and Tables 5 and 6 for location 2. Percent N increased with increasing N fertilization rates in all plant samples except the first petiole sample. Tissue N in the petioles reached their maximum concentrations at the third sample date (2 weeks after the onset of flowering) . The percent N in the tops and tubers at physiological maturity and tubers at harvest was maximized with 120-180 lb of N. The effects of split applications were inconsistent. Data for the percent N derived from the N fertilizer in the plant tissue samples mentioned above are shown in Tables 7 and 8 for location 1, and Tables 9 and 10 for location 2. The percent N derived from the fertilizer increased in all samples with increased N fertilization rates. At location 1, maximum percent uptake of N from the fertilizer occurred with 180 lb N. There did not appear to be any benefits from the split N applications at location 1. The data for location 2 indicate that 120-180 lb N yielded the maximum fertilizer N concentrations in the plant tissue. Maximum N in the plant derived from fertilizer was approximately 40 percent, and no benefits of split N applications were observed. Soil data for the 4 sample dates are presented graphically in Figures 1 through 4 for location 1, and Figures 5 through 8 for location 2. No significant differences were observed between treatments at either location. As expected, there were differences in N concentration with depth at both locations. For location 1, the preplant soil samples showed approximately 5 ppm potassium chloride (KC1) extractable N throughout the profile. A dramatic increase in N concentration, up to 20-30 ppm, was observed for the surface sample at tuber initiation, but below 1.5 feet, the soil was still near the 5ppm N level. By mid-season, the surface sample had decreased to approximately 15-20 ppm, but the N levels in the lower depths were approximately 10 ppm N. The soil sample taken after harvest showed that the soil N concentrations in the lower depths were near their preplant levels. Data for location 2 show approximately 10-15 ppm N in the surface and 5-10 ppm N in the lower part of the profile for the preplant soil sample. A large increase in N, up to near 30 ppm, in the upper profile was again apparent at the second sample date, with the lower depths having N levels slightly above the N levels for the spring sample. The mid-season soil sample showed a decrease in surface N levels to 10- 15 ppm N, but there was no apparent increase in the N levels at the lower depths. The fall sample was very similar to the fall sample at location 1. The N concentrations were at or below those of the spring sample. Summary data showing the N in the profile at each date are presented graphically in Tables 9 and 10 for locations 1 and 2, respectively. The N concentration data for soil water samples collected with suction lysimeters installed at a depth of three feet are located in Table 11. The N concentrations for location 1 were fairly constant at 3-5 ppm N from June through August and then nearly tripled to 13.5 ppm N in September. Nitrogen concentration values for location 2 were much higher from June through August. The average N concentrations for June, July, and August were 42, 31, and 17 ppm. By September the N levels were down to 14 ppm, the same as location 1. The grain yield of corn grown without irrigation water or fertilizer (data not presented) on the 1987 potato site were not significantly influenced by the N management practice for the 1987 potato experiment, and averaged 81 bushels per acre at 15.5 percent moisture. Conclusions From the results of the 1988 investigation, we conclude that 120-180 lb N was sufficient for optimum yields of Russet Burbank potatoes. There did not appear to be any significant beneficial effects of splitting the applications unless some N was applied after the end of tuber set as it seems that N applied before the end of tuber set was taken up more readily by the plant. The soil data indicated that leaching of N below the root zone of the crop was limited in 1988 due to the drought. The large discrepancy in soil water N concentrations between the two locations is not apparent at this time but may partially explain the large yield differences between the two locations. The corn yield data show the N supplying capacity of the soil itself to be approximately 100-120 lb N per acre. The extreme heat and drought experienced during the 1988 growing season must be taken into consideration when analyzing this yield data and the soil N leaching potentials of the different N management treatments. Table 1. The effect of N rate and application time on yield of Russet Burbank potatoes. Location 1. N Fertilization Rate N Fertilization N Fertilization Rate N Fertilization Rate N N Fertilization Rate Total Rate N application N application date date 6-21 lb 5-12lb N per acre N per acre -- -- N application date 7-06 lb N per acre -- N lb N per acre Yield Tuber size distributionOff typecwt per acre Yield Tuber size distribution Under 4 oz. cwt per acre Yield Tuber size distribution 4-10 oz. cwt per acre 167a 186a 185a 195a 178a 173a Yield Tuber size distribution Over 10 oz. cwt per acre 1 b 4ab 5a 6a 7a 5a Yield Tuber size distribution U.S. no. 1 cwt per acre 168a 190a 190a 201a 185a 178a Yield Tuber size distribution Total yield cwt per acre 276 c 311ab 309ab 322a 308ab 297 b Specific Gravity g/cc 1.068a 1.070a 1.070a 1.067a 1.067a 1.068a -- 60 120 -- 60 60 30 Values followed by the same letter were not statistically different at the .05 level of probability. 60 -- 60 30 application date 7-1 8 lb N per acre -- -- -- -- -- -- 60 -- 30 30 54a 60a 62a 62a 60a 58a 54a 62a 57a 59a 63a 61a 0 60 120 120 180 120 Table 2. The effect of N rate and application time on yield of Russet Burbank potatoes. Location 2. application date 5-1 7lb N per acre -- Total N lb N per acre YieldTuber size distributionOff typecwt per acre N Fertilization RateN N Fertilization N Fertilization N Fertilization Rate N Fertilization Rate Yield Tuber size distribution Over 10 oz. cwt per acre YieldTuber size distribution U.S. no. 1 cwt per acre YieldTuber size distribution Total yieldcwt per acre Yield Tuber size distribution Under 4 oz. cwt per acre 44a 39a 48a 51a 40a 49a Yield Tuber size distribution 4-10 oz. cwt per acre 219a 213a 214a 237a 219a 221a 120a 141a 177a 162a 167a 196a 5a 14a 13a 25a 31a 40a N application date 7-1 8 lb N per acre Rate N application date 6-24 lb N per acre -- RateN application date 7-06 lb N per acre -- -- -- -- -- -- -- 60 -- -- 60 -- 60 30 30 30 60 120 -- 60 60 30 Values followed by the same letter were not statistically different at the .05 level of probability. 224a 227a 227a 262a 250a 261a 388a 407a 452a 476a 457a 506a 0 60 120 120 180 120 Specific Gravity g/cc 1.072a 1.075a 1.076a 1.077a 1.073a 1.073a Table 3. The effect of N rate and application time on petiole N concentration of Russet Burbank potatoes. Location 1. N fertilization rate N application date 5-1 2lb N per acre -- N fertilization rate N application date 6-21 lb N per acre -- N fertilization rate N application date 7-06 lb N per acre -- N fertilization rate N application date 7-1 8 lb N per acre -- N fertilization rate Total N lb N per acre Tissue N concentration Petiole sample date 7-05 % N Tissue N concentrationPetiole sample date6-21% N Tissue N concentration Petiole sample date 8-01 % N -- -- -- -- -- 60 120 -- 60 60 30 Values followed by the same letter were not statistically different at the .05 level of probability. 60 60 30 -- 60 30 -- -- 30 2.99 c 3.65 b 4.28a 4.54a 4.26a 3.77 b 2.33 c 2.56 c 3.25 b 3.41 b 3.91a 3.41 b 3.36a 3.45a 3.60a 3.63a 3.58a 3.47a 0 60 120 120 180 120 Tissue N concentration Petiole sample date 7-18 % N 3.75 d 4.67 c 5.30 b 5.54ab 5.75a 5.11 b Table 4. The effect of N rate and application time on N concentration in above ground biomass and tubers of Russet Burbank potatoes. Location 1. N fertilization rate N fertilization N fertilization N fertilization rate N N fertilization rate N application date 5-1 2lb N per acre rate N application date 6-21 lb N per acre -- rate N application date 7-06 lb N per acre -- application date 7-1 8 lb N per acre -- -- Total N lb N per acre % N in plant tissue Sample growth stage Physiological maturity Top % N in plant tissue Sample growth stage Physiological s % N maturity Tubers % N % N in plant tissue Sample growth stage Harvest Tubers % N -- -- -- -- -- 60 120 -- 60 60 30 Values followed by the same letter were not statistically significant at the .05 level of probability. 60 60 30 -- 60 30 -- -- 30 1.33 d 1.95 c 2.94a 2.81ab 3.00a 2.51 b 1.49 b 1.50 b 1.56 b 1.76a 1.71a 1.72a 1.53a 1.62a 1.61a 1.67a 1.59a 1.67a 0 60 120 120 180 120 Table 5. The effect of N rate and application time on petiole N concentration of Russet Burbank potatoes. Location 2. N fertilization rate N application date 5-1 7lb N per acre -- N fertilization rate N application date 6-24 lb N per acre -- -- -- N fertilization rate N application date 7-06 lb N per acre N fertilization rate N application date 7-1 8 lb N per acre N fertilization rate Total N lb N per acre Tissue N concentration Petiole sample date 7-05 % N Tissue N concentrationPetiole sample date6-21% N Tissue N concentration Petiole sample date 8-0 1 % N -- -- -- -- -- -- 60 120 60 60 30 Values followed by the same letter were not statistically different at the .05 level of probability. 60 60 30 -- 60 30 30 -- -- 3.39a 3.57a 3.29a 3.21a 3.35a 3.41a 3.33 b 4.70a 4.82a 4.71a 4.71a 4.47a 2.18 d 2.79 c 3.21 c 3.39 bc 4.19a 3.88ab 0 60 120 120 180 120 Tissue N concentration Petiole sample date 7-18 % N 2.89 d 4.08 c 4.59 b 5.10 b 5.80a 5.08 b Table 6. The effect of N rate and application time on N concentration in above ground biomass and tubers of Russet Burbank potatoes. Location 2. N fertilization rate N fertilization N fertilization N fertilization rate N fertilization rate Total N lb N per acre % N in plant tissue Sample growth stage Physiological maturity Top s % N % N in plant tissue Sample growth stage Physiological maturity Tubers % N % N in plant tissue Sample growth stage Harvest Tubers % N N application date 5-1 2lb N per acre -- rate N application date 6-21 lb N per acre -- -- rate N application date 7-06 lb N per acre -- N application date 7-1 8 lb N per acre -- -- -- -- -- -- 60 120 60 60 30 Values followed by the same letter were not statistically significant at the .05 level of probability. 60 60 30 -- 60 30 30 -- -- 1.66 b 1.88 b 2.29a 2.39a 2.64a 2.40a 1.03 c 1.19 bc 1.29ab 1.26ab 1.47a 1.28ab 1.23 b 1.45ab 1.58a 1.50ab 1.53a 1.49ab 0 60 120 120 180 120 Table 7. The effect of N rate and application time on percent N from fertilizer in petioles of Russet Burbank potatoes. Location 1. N fertilization rate N application date 5-1 2lb N per acre -- N fertilization rate N application date 6-21 lb N per acre -- N fertilization rate N application date 7-06 lb N per acre N fertilization rate N application date 7-18 lb N per acre -- N fertilization rate Total N lb N per acre % N from fertilizerPetiole sample date6-21% N % N from fertilizer Petiole sample date 7-05 % N % N from fertilizer Petiole sample date 7-1 8 % N % N from fertilizerPetiole sample date8-01% N e -- -- -- -- -- -- -- 60 120 60 60 30 Values followed by the same letter were not statistically different at the .05 level of probability. 0.0 f 0.0 e 0.0 c 22.2 b 28.4 d 38.2a 41.9a 34.0a 37.7 b 38.9a 30.3 c 39.4a 27.1 0.0 20.9 b 30.2a 18.0 bc 15.3 c 8.9 d 23.0 d 36.9ab 35.7 bc 41.5a 0 60 120 120 180 120 e 31.9 c 60 60 30 -- 60 30 -- -- 30 Table 8. The effect of N rate and application time on percent N from fertilizer in above ground biomass and tubers of Russet Burbank potatoes. Location 1. N fertilization rate N fertilization N fertilization rate N fertilization N fertilization rate N application date 5-12 lb N per acre -- rate N application date 6-21 lb N per acre -- -- rate N application N application date 7-18 date 7-06 lb N per acre lb N per acre -- -- -- Total N lb N per acre % N from fertilizer Sample growth stage Physiological maturity Top % N from fertilizer Sample growth stage Physiological s % N maturity Tubers % N % N from fertilizer Sample growth stage Harvest Tubers % N -- -- -- -- 60 120 60 60 30 Values followed by the same letter were not statistically different at the .05 level of probability. 60 60 30 -- 60 30 30 -- -- 0.0 d 21.4 c 38.3a 32.4 b 39.9a 33.2 b 0.0 d 20.3 c 33.6 b 29.7 b 40.0a 31.2 b 0.0 b 38.5a 33.0a 29.8a 38.2a 32.1a 0 60 120 120 180 120 Table 9. The effect of N rate and application time on percent N from fertilizer in petioles of Russet Burbank potatoes. Location 2. N fertilization rate N application date 5-17 lb N per acre -- N fertilization rate N application date 6-24 lb N per acre -- N fertilization rate N application date 7-06 lb N per acre -- N fertilization rate N application date 7-18 lb N per acre -- N fertilization rate Total N lb N per acre % N from fertilizerPetiole sample date6-21% N % N from fertilizer Petiole % N from fertilizer Petiole sample sample date 7-05 % N date 7-18 % N % N from fertilizerPetiole sample date8-01% N -- -- -- -- 60 -- 120 60 60 30 Values followed by the same letter were not statistically different at the .05 level of probability. 0.0 d 0.0 d 34.9 bc l0.0ab 45.6a 14.9a 11.0a 41.5ab 3.5 cd 34.6 bc 28.0 c 5.8 bc 0.0 d 29.4 c 43.9 b 45.4 b 53.0a 40.6 b 0.0 c 22.2 b 38.2a 34.0a 38.9a 39.4a 0 60 120 120 180 120 -- 60 60 30 -- -- 30 -- 60 30 Table 10. The effect of N rate and application time on percent N from fertilizer in above ground biomass and tubers of Russet Burbank potatoes. Location 2. N fertilization rate N fertilization N fertilization rate N fertilization rate N fertilization rate Total N lb N per acre N application date 7-18 lb N per acre % N from fertilizer Sample growth stage Physiological maturity Top s % N % N from fertilizer Sample growth stage Physiological maturity Tubers % N % N from fertilizer Sample growth stage Harvest Tubers % N N application date 5-1 7lb N per acre -- rate N application date 6-24 lb N per acre -- -- -- N application date 7-06 lb N per acre -- -- -- -- -- -- 60 120 60 60 30 Values followed by the same letter were not statistically different at the .05 level of probability. 60 60 30 -- 60 30 30 -- -- e 0.0 21.4 d 38.3 b 32.4 c 39.9a 33.2 c 0.0 d 19.8 c 39.7a 31.0 b 44.4a 33.9 b 0.0 c 20.3 b 33.6a 29.7a 40.0a 31.2a 0 60 120 120 180 120 Table 11. Average N concentrations in suction lysimeters placed three feet below soil surface. Location 1 2 Month June ppm 4.52 42.05 Month July ppm 4.21 31.38 Month August ppm 5.32 16.92 Month September ppm Month October ppm 13.53 14.12 — — — 13.34 Funding MPIC Nitrogen Management Strategies for Potatoes to Maximize Profit and Minimize Nitrate Leaching: 1988 Results J. T. Ritchie and B. S. Johnson Conventional management practices for potato production in Michigan cause high levels of nitrate leaching that are potentially damaging to the environment. A field experiment was established to investigate the possibility for minimizing nitrate leaching while maintaining adequate tuber yields and quality. Results were used to test the nitrate leaching submodel of SUBSTOR, a model of potato growth and development. Methods The experiment was conducted on McBride sandy loam at the Montcalm Potato Research Farm. Two plots, 10 rows X 50 ft. in length, were planted to Russet Burbank potatoes on May 11. The row spacing and seed spacing within the row were 34 in. and 12 in. , respectively. A treatment consisting of "conventional” nitrogen (N) and irrigation management was compared with a "research” treatment involving reduced N inputs and a modified irrigation schedule. For the conventional treatment fertilizer N was applied at a rate of 200 lb/A including 75 lb/A at planting (500 lb/A of 15-10-15). The input of N was lower for the research treatment as the total amount of N applied was 110 lb/A for the season and 28 lb/A at planting (558 lb/A of 5-10-15). Irrigation amounts for the treatments also differed as the conventional treatment received 9.8 in. of water during the season compared to 6.4 in. for the research treatment. Figure 1 illustrates the timing of the irrigation and fertilizer N applications. Pesticides were applied as needed by the farm manager. Permanently installed drainage lysimeters, one in each plot, were used to monitor soil water drainage and nitrate (N03) leaching on a weekly basis. The lysimeters (4 ft. X 68 in. X 6 ft. deep) intercept water at the 7 ft. soil depth. Drainage depths and N03 leaching were determined by measuring the volume of water collected and sampling it each time for N03 and selected pesticides. Soil samples for ammonium (NH4) and N03 measurement were collected prior to planting, at midseason, and after fall harvest. Samples were obtained from four locations in each plot and at five depths at each location. Sampling depths were at 6 in. increments to a depth of 1 ft. , and at 1-ft. increments to a depth of 4 ft. A complete set of weather data including solar radiation, maximum and minimum temperatures, and rainfall was collected daily and used as inputs to the computer simulation model, SUBSTOR. Tuber and haulm growth rates were determined by periodically measuring tuber and haulm dry weights. Potatoes were harvested on October 6 from 80 ft. of row (227 ft2). Tuber quality was evaluated by measuring the size distribution, and the specific gravity and dry matter content of tubers in the 4 to 10 oz. size class. Results Tuber yields and quality are given in Table 1. Yields were the same for both treatments averaging 244 cwt/A which is slightly greater than the state average potato production of 230 cwt/A in 1988 (Michigan Agricultural Statistics, 1988). Tuber size distribution, specific gravity, and dry matter content were also about the same for each treatment. No. 1's accounted for only 45 percent of the total tuber yield in this experiment. The specific gravity of 1.067 was lower than normal for Russet Burbank suggesting that heat and water stress may have been factors during 1988. Table 1. Tuber yield and quality in terms of size distribution, pick outs, specific gravity and dry matter content. Treatment Conventional Research Yield (cwt/A) Yield ( cwt/A) No. 1 Total 245 112 242 103 Percent Size Distribution No.l 46 43 Percent Size Distribution <4oz 20 22 Percent Size Distribution 4-10oz 42 41 Percent Size Distribution >10oz 4 3 Pick outs 35 35 Spec. Grav. 1.068 1.065 % Dry Matter 17.6 18.0 Important objectives of this experiment were to monitor soil water drainage and N03 leaching and to use these results to test the N03 leaching model of SUBSTOR. Because N03 leaching is dominated by soil water drainage, rain and irrigation strongly influence the extent of N03 leaching that occurs. Figure 2 illustrates cumulative rainfall and precipitation (rainfall + irrigation) at the site during 1988. Rainfall was below normal during 1988 as only 10 in. of rain fell from the beginning of the measurement period (April 13) until vine kill (September 10). Nearly the same amount of rainfall (8 in.) occurred during the next 50-d period ending on November 1. Figure 3 compares measured drainage depths for the two treatments with simulated values produced by SUBSTOR. Due to the dry conditions in 1988 drainage was negligible during the majority of the growing season. About 3.4 in. of water drained through the lysimeter soil in the research treatment during the period April 11 to October 26. Soil water drainage was slightly greater for the conventional treatment as 4.1 in. of drainage water was collected during the same period. For both treatments, most of the drainage occurred after vine kill when plant water uptake ceased and rainfall increased dramatically at the Montcalm Research Farm. Figure 3 also shows that simulated soil water drainage compared favorably with the observed values, especially during the unseasonably wet post harvest period. Measured and simulated loss of N03 from the lysimeter soil is reported in Figure 4. Cumulative N03 leaching was 73 lb/A for the conventional treatment compared to 58 lb/A for the research treatment. These results are consistent with the observation that the two treatments produced the same yields with much different fertilizer N inputs. Assuming a relative constant tuber N content of 0.33 lb/cwt, about 80 lb/A of N (244 cwt/A X 0.33 lb/cwt) should have been removed from the soil for both treatments. The difference between the amount of fertilizer N applied and the amount of N assimilated in tubers is equal to 120 lb/A (200 - 80) for the conventional treatment but only 30 lb/A (110 - 80) for the research treatment. This calculation and the observation that a significant amount of drainage occurred after the last measurement date reported in Figure 4 suggest that the diverse management strategies used in this experiment may cause substantial differences in N03 leaching when considered on an annual basis. The simulated curves in Figure 4 represent the extent of N03 leaching for each treatment as calculated by SUBSTOR. Although the model simulated the drainage process quite well (Figure 3), estimates of N03 loss were lower than the measured values for each treatment. This discrepancy can be accounted for as follows. Because plants extract water and nutrients (e.g., nitrogen) from the soil, the computer simulation model must calculate the growth and development of potatoes reasonably well in order to simulate the soil water and nitrogen dynamics accurately. Figure 5 compares measured haulm weights with simulated values and Figure 6 compares measured and simulated dry matter accumulation in the tubers. These Figures demonstrate that SUBSTOR underestimated haulm growth rate for the research treatment (Figure 5) but overestimated tuber growth for both treatments (Figure 6). Thus, N uptake as calculated by the model was also overestimated leaving little residual soil N03 for leaching. Summary and Future Objectives Treatments consisting of "conventional" and "research" N and irrigation management produced the same yields. Cumulative N03 leaching under conventional management exceeded N03 leaching under the research approach by about 15 lb/A as of the last measurement date in 1988. Differences between these two management strategies may prove to be much greater when considered on an annual basis. This possibility will be evaluated by analyzing the soil samples collected during 1988 for N03 and NH4 and by monitoring drainage and N03 leaching from the lysimeters on a year-around basis. SUBSTOR simulated soil water drainage accurately but underestimated N03 leaching during 1988. The model needs to be refined to more accurately calculate growth and development of the potato for all possible combinations of weather and management variables used as inputs. Those aspects of soil N dynamics affected by plants, especially N uptake, can then be calculated in a manner that will allow SUBSTOR to be used estimate N03 with the desired level of confidence. Fig 1. Timing of irrigation and fertilizer N applications in 1988. Fig 2. Cumulative rainfall (R) and irrigation (I) during 1988 for the two treatments. Fig 3. Measured and simulated soil water drainage during 1988. Fig 4. Measured and simulated nitrate leaching during 1988. Fig 5. Measured and simulated (SIM) haulm dry weight (HDW) accumulation during 1988. Fig 6. Measured and simulated tuber dry weight (TDW) accumulation during 1988. Funding MPIC EFFECT OF INCREASING NITROGEN RATES UPON PRODUCTION OF RUSSET BURBANK POTATOES IN THE UPPER PENINSULA 1988 R. H. LEEP Department of Crop & Soil Sciences Michigan State University This study was continued from previous years to evaluate the effect of nitrogen rates upon the production of russet burbank potato production in the Upper Peninsula. Questions have risen on how much nitrogen credit should be given for the previous legume crop plowed down for green manure and nitrogen. This study was designed to evaluate the effect of increasing nitrogen rates on russet burbank potatoes where alfalfa was the previous crop. PROCEDURE The study was established on the Paul VanDamme Farm in Marquette County on an Onaway sandy loam. The previous crop was alfalfa which was plowed down in the late summer and rye was planted as a winter cover. The treatments were arranged in a randomized complete block experimental design with 4 replications. 1000 pounds of 6-24-24 per acre were applied in the row at planting. Nitrogen consisted of 0, 60, and 120 pounds nitrogen per acre, applied sidedressed as urea, and 60 pounds nitrogen applied sidedressed as sulfur coated urea. This gave a total of 60, 120 and 180 pounds nitrogen per acre for the treatments. Petioles were sampled for nitrogen content on July 26 and September 2. The soil was sampled prior to fertilizer application for total nitrogen content at six inch increments down to 2 feet. The soils were sampled for total nitrogen content for each treatment at harvest to a depth of two feet. The potatoes were planted on May 6 and harvested on September 24. All pesticide applications and cultivations were completed by the farm cooperator as the plots were established within a commercial field of potatoes. RESULTS Yields, percent size distribution, and specific gravity is given in Table 1. There were no significant differences in yield, size distribution or specific gravity due to nitrogen treatment. Petiole nitrogen analysis revealed no significant differences between treatment means on the first sampling date, however, on the second sampling date the 120 pound nitrogen rate of sulfur coated urea and 180 pound nitrogen rate of urea were significantly higher in nitrogen content than the 60 and 120 pound per acre nitrogen urea treatments (Table 2). As observed in previous studies specific gravity decreased slightly with increasing nitrogen rates, however, the differences were not significantly different at the five percent confidence level. Soil analysis has not been completed at this time but will be reported at a later date. RESULTS continued In summary, potato yields and size distribution were not significantly affected by the nitrogen rate or source in this study. Sulfur coated urea at 120 and urea at 180 pounds per acre significantly increased nitrogen content of potato petioles at the second sampling date on September 2. Table 1. Influence of nitrogen upon yield» size distribution and specific gravity on Russet Burbank potatoes grown in the Upper Peninsula. Treatmen t N-Source Urea Urea SC Urea Urea Mean Yield cwt/A Treatmen t Rate lbs/A Total 60 443 462 120 433 120 426 180 empty table cell 441 Yield Cwt/A No. 1 320 317 288 293 Percent Size Distribution No. 1 72 69 66 68 Percent Size Distribution Under 4 oz. 7 5 7 5 Percent Size Distribution 4 to 10 oz. 38 36 38 35 Percent Size Distribution Over 10 oz. 34 33 29 34 Percent Size Distribution Pick Outs 21 26 26 26 Specific Gravity 1.072 1.071 1. 067 1.069 305 69 5.5 37 33 25 1.070 Table 2. Influence of nitrogen fertilizer upon petiole nitrogen content in Russet Burbank potatoes grown in the Upper Peninsula. Treatmen Treatmen t N-Source t Rate lbs/A 60 120 120 100 Urea Urea SC Urea Urea *Means followed by the same letter are not significantly different. 3.9 a* 3.8 a 3.8 a 4.0 a Petiole Nitrogen Content (%) Sampling Dat 7-26-88 Petiole Nitrogen Content (%) Sampling Date 9-2-88 2.2 b 2.6 ab 3.0 a 3.0 a LEGUME NITROGEN CONTRIBUTIONS IN LEGUME-POTATO ROTATIONS Funding MPIC T.S. Griffin and O.B. Hesterman Department of Crop and Soil Sciences Michigan State University Nitrogen-fixing legumes have been used in rotational cropping systems for many years. In addition to significant nitrogen (N) contributions to subsequent non-legume crops, the inclusion of legumes in crop rotations may disrupt weed and pest cycles, and improve soil aeration and structure. A renewed interest in legume-based crop rotations has emerged because farmers want to reduce their purchased inputs, diversify their cropping systems, and decrease the potential for environmental contamination from fertilizers and pesticides. Potato production in Michigan typically involves intensive management with high fertilizer (mainly N) and pesticide inputs. Legume-based potato rotations are becoming an attractive alternative to continuous potato or corn-potato cropping sequences. The objectives of this study were: 1. To determine the N contribution from forage legumes to a subsequent potato crop. 2. To evaluate the effect of seeding year legume management (no harvest vs. 2 or 3 harvests) on the N contribution to potatoes. 3. To monitor populations of root-lesion nematode (RLN) and Verticillium fungus, the causative agents of Potato Early Die disease, through the course of the 2-year rotations. 4. To evaluate the effect of rotation crop and N fertilizer rate on tuber quality of the subsequent potato crop. Materials and Methods Two-year crop rotations were established in 1987 at the Montcalm Research Farm (MRF) and at the Kellogg Biological Station (KBS). The rotation crops and legume harvest schemes in the first year were: ’Saranac’ alfalfa, 0 and 3 harvests; ’Mammoth’ red clover, 0 and 3 harvests; ’Viking’ birdsfoot trefoil, 0 and 2 harvests; ’Nitro’ alfalfa, 3 harvests (KBS only); sweetclover, 0 harvests (MRF only); spring seeded hairy vetch, 0 harvests; potatoes + fall seeded hairy vetch; corn; potatoes (’Shepody’ at MRF, ’Atlantic’ at KBS); and fallow. Experimental plots were 24 by 50 feet. In 1987, legumes, potatoes and corn were planted on April 20, May 4 and May 9, respectively. Potato and corn plots were split into subplots and fertilized with 0, 67, 133 and 200 lb N/acre, as ammonium nitrate. Legumes were harvested for hay on July 9, August 10 and October 30. Potatoes and corn (for grain) were harvested on September 4 and October 10, respectively. Plots were sampled for RLN and Verticillium on April 20, July 23 and November 5. Legumes were sampled for dry matter and N production on October 20. In 1988, potatoes (variety ’Shepody’) were planted on all plots on May 9 and May 15 at KBS and MRF, respectively. Plots were split into subplots and fertilized with 0, 67, 133 and 200 lb N/a (67 lb N/a at planting, remainder applied just prior to hilling). Potato vine samples were taken August 20 for biomass and N yield measurements. Tubers were harvested from the center two rows of each four-row plot on September 30 and November 15 at MRF and KBS, respectively. Tubers from Montcalm were evaluated for common scab, Rhizoctonia, growth cracks and specific gravity. Results All results discussed here are from the Montcalm location only. All forage legumes were successfully established in 1987. End-of-season N yields (1987) and plowdown N (May, 1988; includes spring regrowth) are shown in Table 1. The N yield at plowdown, which represents the maximum potential N contribution from the legumes, ranged from 65 to 281 lb N/a. However, only 20-30% of the total N in legumes generally becomes available to the first subsequent crop. Although multiple hay harvests of red clover in the seeding year (3.5 tons/acre) did reduce plowdown N yield somewhat, harvesting alfalfa 3 times in the seeding year (3.8 tons/acre) actually increased total N available for plowdown. This was due to the increased root mass when alfalfa was harvested. Population trends of the root lesion nematode during the 1987 growing season (Table 2) confirm the concerns of some potato growers in Michigan. Nematode populations reached high levels in roots and soil in the legume plots when compared to nematode populations in corn and fallow plots (potato plots were treated with a nematicide; data not shown). Alfalfa, birdsfoot trefoil and red clover supported similar populations. Hairy vetch (an annual crop) supported even higher populations (563 nematodes/g root) than the other legumes, while sweetclover had much lower populations (53 nematodes/g root). Without chemical control for nematodes, the potential increase in nematode population may become an important criterion in the selection of an appropriate legume species for short-term rotations. Yields of ’A’ grade (Table 3) and total tubers (Table 4) demonstrate a substantial benefit from legumes to a subsequent potato crop. Potatoes following legumes either did not respond to N fertilizer applications (as measured by ’A’ grade tuber yield) or decreased as N fertilizer rate increased. This suggests that either potato growth became indeterminate due to excess nitrogen, or that some other factor (e.g., moisture) limited growth. Non-legume treatments either showed linear increases in yield with increased N rates (e.g., following potato or fallow) or a quadratic response, increasing to a maximum yield, then decreasing, following corn. In all rotation sequences except fallow-potato, N inputs (plowdown N + fertilizer N) reached a level where additional fertilizer N either failed to increase tuber yield or decreased tuber yield. For example, tuber yield following alfalfa hay decreased if any fertilizer N was applied, while tuber yield following corn decreased when N fertilizer rate was increased from 134 to 200 lb N/a. The fertilizer response of potatoes following different rotation crops suggests that greater attention should be given to N applications in rotational cropping systems for maximum economic benefit. One method of estimating legume N contributions is the Fertilizer Replacement Value (FRV), defined as the amount of inorganic N required to produce a yield identical to that following a legume without N fertilizer, FRV values at Montcalm in 1988 ranged from 12 (birdsfoot trefoil, 0 harvests) to 115 lb N/a (alfalfa, 3 harvests). For all rotations systems, FRV’s were much lower than plowdown N yield, indicating that N released from slowly-decomposing legume residues is not entirely available to the first subsequent potato crop. Comparison of plowdown N yield and FRV’s also indicates that the benefit of legume-based rotations is not solely a function of the amount of N incorporated. For example, sweetclover contained the highest amount of N at plowdown (281 lb N/a), but the FRV of 62 lb N/a was exceeded by three other legumes. The most likely reason for this relationship is variation in the chemical composition of the incorporated legume material, with more mature, highly lignified residue decomposing to a lesser extent in the soil. Repeated harvests of alfalfa and red clover in 1987 did not decrease the benefit (as measured by the FRV) to the 1988 potato crop. Previously, it was thought that to obtain the maximum benefit from legumes, particularly in short rotation cycles, the legume should not be harvested. This research shows that the producer need not sacrifice income (from hay) to obtain significant N contributions from forage legumes. Although the yield benefits from legume-based rotations are important, tuber quality of the subsequent potato crop must also be considered. In 1988, rotation crop and N fertilizer rate had a significant effect on tuber quality (Table 5). The severity of common scab (measured as the percent of tuber area with scab) increased following red clover hay and potatoes (10.38 and 10.40%, respectively), while tubers following sweetclover exhibited 5.80% coverage of scab. The scab severity is due primarily to previous rotation crop, as severity decreased with increased N fertilizer applications. The incidence of Rhizoctonia or black scurf (as percent of plots showing symptoms) was similar for all rotations crops except hairy vetch. Rhizoctonia was observed in 63% of plots following hairy vetch, compared to 6 to 25% for other rotation crops. Cracking of tubers is generally caused by factors which promote the rapid growth of the tubers, such as excess N. In this study, the percent of tubers with cracks increased following sweetclover and hairy vetch (9.38 and 11.88%, respectively), both of which contained over 200 lb N/a at plowdown. The increase in cracking as fertilizer N rate increased confirms that N influences the severity of cracking, regardless of N source. Conclusions Nitrogen-fixing legumes can significantly reduce the requirements for N fertilizer in potato production. Furthermore, such N contributions can be realized even if the legume is harvested repeatedly during short (2-year) rotation cycles, thereby generating income for the producer. At current N fertilizer price levels, it is doubtful that producers can justify the implementation of legume-based rotations solely for potential N contributions. Definitive evidence is lacking on whether the decomposition of high N-yielding legumes (e.g., sweetclover) can lead to high nitrate levels in soil. This is particularly important on sandy soils, used for potato production, that are more prone to nitrate leaching problems. The selection of legume species based on populations of soil-borne pathogens and their impact on tuber quality also deserves additional attention. Table 1. Nitrogen yield of legumes at Montcalm Research Farm in Fall, 1987 and at plowdown in Spring, 1988. Crop/Harvests Alfalfa/0 Alfalfa/3 Red Clover/0 Red Clover/3 Birdsfoot Trefoil/0 Birdsfoot Trefoil/2 Sweetclover/0 Hairy Vetch/0 Fall, Shootlb N/a 1987 Root Spring 1988 Shoot1 Total at Plowdown2lb N/a lb N/a lb N/a 66 57 137 59 29 26 116 185 71 106 65 95 22 26 106 19 55 55 51 51 17 13 59 --3 192 218 263 205 68 65 281 204 1Spring regrowth in 1988. 2Plowdown N equals 1987 N yield plus 1988 spring regrowth. 3Hairy vetch did not survive winter. Table 2. Soil and root populations of root-lesion nematode (RLN) from July 23, 1987, sampling at Montcalm Research Farm1. Crop/Harvests RLN/l00cc Soil RLN/1.0g Root Alfalfa/0 Alfalfa/3 Red Clover/0 Red Clover/3 Birdsfoot Trefoil/0 Birdsfoot Trefoil/2 Sweetclover/0 Hairy Vetch/0 Corn Fallow LSD (P = 0.05) 23.5 15.0 80.5 34.0 17.8 15.8 7.8 74.5 7.3 35.5 50 1Potato plots treated with nematicide; data not shown. 119.5 409.5 248.8 244.0 251.0 385.4 52.5 563.5 19.8 109.5 350 Table 3. Yield of 'A' grade tubers (4-10 oz.) and fertilizer replacement values (FRV) for 1987 rotation treatments and 1988 nitrogen fertilizer rates at the Montcalm Research Farm. 1987 Crop/Harvests tubers/a 67 133 'A' tubers/a N Fertilizer Applied (lb/acre)0cwt 'A' N Fertilizer Applied (lb/acre) N Fertilizer Applied (lb/acre) N Fertilizer Applied (lb/acre)200cwt Alfalfa/0 Alfalfa/3 Red Clover/0 Red Clover/3 Birdsfoot Trefoil/0 Birdsfoot Trefoil/2 Sweetclover/0 Hairy Vetch/0 Potato Fallow Corn LSD (P=0.05) Between Crops cwt 'A' tubers/a cwt 'A' tubers/a 241 232 242 224 230 220 234 244 261 244 230 222 225 235 235 239 201 204 210 257 259 263 234 211 201 233 194 218 189 202 251 254 217 233 252 219 226 209 210 231 238 227 220 203 FRV 1 (lb N/a) 68 115 35 52 12 13 62 84 57 37 —— 19 empty table cell empty table cell empty table cellempty table cell 11 empty table cellempty table cell LSD (P=0.05) Between N Rates 1 Nitrogen response curve of corn-potato system used as control. FRV equal to inorganic nitrogen input required to produce yield identical to that following legume with no fertilizer applied. empty table cell empty table cell Table 4. Total tuber yield in 1988 for 1987 rotation crops and 1988 N fertilizer rates at the Montcalm Research Farm. N Fertilizer Applied lb/acre 0 N Fertilizer Applied lb/acre N Fertilizer Applied lb/acre 133 67 cwt/a N Fertilizer Applied lb/acre200cwt/a cwt/a 1987 Crop/Harvests Alfalfa/0 Alfalfa/3 Red Clover/0 Red Clover/3 Birdsfoot Trefoil/0 Birdsfoot Trefoil/2 Sweetclover/0 Hairy Vetch/0 Potato Fallow Corn LSD (P = 0.05) Between Crops Between N Rates LSD (P = 0.05) cwt/a 282 305 269 274 247 262 301 287 271 269 236 22 13 310 285 306 277 282 272 328 335 325 316 291 302 292 321 320 309 275 313 282 317 338 335 317 306 290 316 275 287 301 301 349 360 312 empty table cellempty table cellempty table cell empty table cellempty table cellempty table cell Table 5. Effect of rotation crop and N fertilizer rate on the incidence of common scab (SCAB), Rhizoctonia (RHIZ) and growth cracks (CRACK), and on the specific gravity (GRAV) of tubers at Montcalm Research Farm in 1988. Crop/Harvests Alfalfa/0 Alfalfa/3 Red Clover/0 Red Clover/3 Birdsfoot Trefoil/0 Birdsfoot Trefoil/2 Sweetclover Hairy Vetch Potato + Vetch Corn Potato Fallow LSD (P = 0.05) N Fertilizer Rate (lb/a) 0 67 N Fertilizer Rate (lb/a) 134 N Fertilizer Rate (lb/a) N Fertilizer Rate (lb/a) 200 LSD (P = 0.05) SCAB1 RHIZ2 3 CRACK 6.23 7.23 7.69 10.38 7.98 7.16 5.80 7.63 9.53 8.20 10.40 7.00 2.4 10.61 8.43 7.35 5.81 1.4 6.3 8.3 18.8 18.8 8.3 25.0 12.5 62.5 25.0 18.8 18.8 18.8 24.8 10.4 13.2 35.4 21.5 14.3 5.00 6.25 6.88 3.13 6.25 1.25 9.38 11.88 3.75 4.38 5.00 6.88 5.24 2.71 3.75 6.25 10.63 3.03 1Percent of tuber area with scab; 10 tubers/plot evaluated. 2Percent of plots with Rhizoctonia present. 3 Percent of tubers with cracks; 10 tubers/plot evaluated. GRAV 1.080 1.083 1.083 1.083 1.081 1.082 1.082 1.081 1.082 1.082 1.082 1.085 NS 1.080 1.082 1.083 1.083 NS Funding Federal Grant INFLUENCE OF IRRIGATION, NITROGEN AND CALCIUM LEVELS ON SPECIFIC GRAVITY AND INTERNAL DEFECTS OF ATLANTIC AND RUSSET BURBANK POTATOES G.H. Silva, R.W. Chase and R.B. Kitchen Specific gravity and internal defects are two important quality parameters, particularly for processing potatoes. These attributes are largely influenced by environmental and management factors and show wide variations among growers, management levels and seasons. A study was initiated in 1987 to investigate the role of irrigation, nitrogen and supplementary calcium applications in relation to specific gravity and internal defects. This study was continued in 1988 with some modifications based on the 1987 data. A split-split plot design with four replications was used to evaluate 2 irrigation levels (irrigation scheduling and over-irrigation), 2 nitrogen levels (125/200 for Atlantic and 150/225 for Russet Burbank) and 4 calcium treatments [750 gypsum/a applied: (a) at planting, (b) at hilling, (c) split at planting and hilling and (d) untreated]. Supplementary calcium applications were specifically directed towards controlling internal brown spot (IBS). Most of the literature points towards localized calcium deficiency in the tubers as a cause of this disorder. In light of its relative immobility within the plant, calcium was placed in close proximity to the developing tubers. The 2 varieties, Atlantic and Russet Burbank, were planted in 2 separate experiments. A drip irrigation system was Installed to facilitate application of different quantities of water to the treatments. Irrigation scheduling treatment was based on Michigan State University irrigation scheduling system. Accordingly, this treatment received 10.7 inches of irrigation water during the season. Over-irrigation treatment was applied one month before harvest and received an excess of 5.5 inches during this period in 7 separate irrigations. The trial was planted on May 5. The previous crop was alfalfa. Initial soil test showed a pH of 5.6 and a calcium level of 730 lbs/a. The fertilizers applied were 500 lbs/a 5-10-15 with planter and a topdressing of 25 lbs N/a for Atlantic and 50 lbs N/a for Russet Burbank as urea on June 15. For those treatments receiving the higher level of N, a second topdressing of 75 lbs N/a was applied on July 6. Petiole samples for nutrient analysis were taken on August 4. The trial was harvested on September 27. Following harvest, 100 tubers (25 from each replication) were cut to determine the frequency of IBS and hollow heart. Tuber peel samples were taken from each treatment and sent to MSU Soil Testing Laboratory for analysis. The results obtained with Atlantic and Russet Burbank are summarized in Tables 1 and 2, respectively. In both varieties, over-irrigation resulted in decreased specific gravity and slightly higher yields. Higher nitrogen level decreased specific gravity of Russet Burbank more than in Atlantic. Although both varieties showed significantly higher N uptake at higher N application rate, there was no response in tuber yield. There was a tendency for hollow heart to increase with over-irrigation. In Atlantic, calcium treated plots showed a decrease in the occurrence of IBS from 21% for untreated to an average of 14% for the 3 calcium treatments. Calcium applied to the furrow at planting had the lowest frequency (11%) of IBS. In Russet Burbank, the occurrence of IBS in all treatments was very low compared to Atlantic. It is evident that gypsum applications reduced the frequency but did not eliminate the problem of IBS nor did it reduce IBS to an acceptable level. More soluble forms of calcium need to be tested to enhance the uptake of calcium by the tubers. Preliminary investigations of Dr. R. Hammerschmidt have shown that increased calcium levels in the tuber is helpful in resisting some of the storage diseases such as soft rot. In both varieties, calcium treatments produced no significant effects on tuber yield, specific gravity and hollow heart. Post harvest evaluations showed that irrigation, nitrogen and calcium treatments produced no significant effects on chip color of Atlantic (Table 1). Furthermore, these treatments did not appear to have significant effects on after cooking darkening and blackspot susceptibility (Tables 3 and 4). The results from irrigation treatments point towards an important management strategy to improve specific gravity. Traditionally, Michigan receives excess rainfall late in the growing season and it is not uncommon for this rain to occur on a day when the crop was irrigated. It appears that holding back on irrigation, particularly in the last month before harvest would lead to increased dry matter and reduced hollow heart. Equally important is to avoid a delay of harvest in order to avoid periods of excess water after the crop has matured and the vines are dead. Table 1. Dry Matter and Internal Defects — Atlantic — Montcalm Research Farm — 1988 (141 days). Treatment Tuber Yield Tuber Yield U.S. No. 1 Total Percent Percent Specific Gravity Chip Color Petiole N HH Percent IBS Irrigation scheduling Over-irrigation Nitrogen: 125 lbs 200 lbs Nitrogen: Calcium: (1) 0 (2) 750(P) Calcium: (3) 750(P+H) Calcium: (4) 750(H) Calcium: 431 466 445 453 451 458 443 446 486 521 498 509 507 513 496 499 1.086a 1.081b 1.084 1.083 1.084 1.084 1.083 1.083 64 62 61 63 60 64 63 63 2.9 2.8 2.5b 3.2a 2.9 2.7 2.9 2.8 8 14 10 12 13 10 11 10 13 17 14 16 21a 11b 13b 16ab Table 2. Dry Matter and Internal Defects — Russet Burbank — Montcalm Research Farm — 1988 (142 days). Tuber Yield Tuber Yield (cwt/a) (cwt/a) Percent Perc ent Treatment U.S. No. 1 Total Specific Gravity Petiole N HH IBS Percent Irrigation Scheduling Over-irrigation Nitrogen: 150 lbs 225 lbs Nitrogen: Calcium: (1) 0 Calcium: (2) 750(P) (3) 750(P+H) Calcium: (4) 750(H) Calcium: 280 301 284 297 292 293 286 275 399 432 403 432 417 428 421 417 1.078a 1.073b 1.077a 1.074b 1.077 1.075 1.075 1.076 3.7 3.6 3.4b 3.8a 3.6 3.6 3.7 3.5 3 6 3 6 6 4 3 6 5 7 6 7 9 5 5 6 Table 3. Post Harvest Evaluations — Atlantic. Treatment After Cooking Darkeningy Irrigation scheduling Over-irrigation Nitrogen: 125 lbs 220 lbs Nitrogen: Calcium: (1) 0 (2) 750(P) Calcium: (3) 750(P+H) Calcium: (4) 750(H) Calcium: 1.3 1.2 1.2 1.3 1.1 1.4 1.1 1.4 Percent Blackspot Percent Blackspot Bruisedz Check 4 3 3 4 5 3 4 3 45 49 53 48 48 52 52 50 yRating based on a scale of 1-5; 1 = no darkening, 5 = severe darkening (black) 1 hour after boiling. zTubers removed from 40°F storage and bruised artificially with 10 revolutions in a wooden drum and evaluated after 48 hours. Table 4. Post Harvest Evaluations — Russet Burbank. Treatment After Cooking Darkeningy Percent Blackspot Percent Blackspot Check Bruisedz Irrigation scheduling Over-irrigation Nitrogen: 150 lbs Nitrogen: 225 lbs Calcium: (1) 0 Calcium: (2) 750(P) (3) 750(P+H) Calcium: (4) 750(H) Calcium: 1 1 1 1 1 1 1 1 4 3 3 4 4 1 4 5 34 41 40 35 38 31 44 36 yRating based on a scale of 1-5; 1 = no darkening, 5 = severe darkening (black) 1 hour after boiling. zTubers removed from 40°F storage and bruised artificially with 10 revolutions in a wooden drum and evaluated after 48 hours. Funding MPIC CONTROL OF INTERNAL BROWN SPOT (HEAT NECROSIS) OF POTATOES Departments of Botany and Plant Pathology R. Hammerschmidt and R.W. Chase and of Crop and Soil Sciences Internal brown spot (IBS) presents a major problem in the production of high quaility potatoes. This problem is particulary evident with the variety Atlantic. Since Calcium deficiency and heat stress have been associated with this disorder, we have evaluated the influence of additional calcium and an antitranspirant treatment on the expression of IBS. PROCEDURE A location on the farm of W.J. Lennard and Sons, Smaria, was chosen for this study because of a history of IBS in this location. The variety Atlantic was used. Two planting dates were also used (April 15 and May 15). At each planting date plots were set out to receive the antitranspirant (AT) or no AT in combination with four calcium applications. At harvest, the tubers were scored for IBS. Since calcium has been showed to decrease soft rot expression, samples of tubers were also infected with Erwinia carotovora subsp. carotovora to determine if there were any changes in the expression of this disease. RESULTS Due to little obvious differences in plant growth, the tubers from both planting dates were analyzed as a single group. Application of Calcium did have a significant effect on reducing the amount of IBS. However, it should be pointed out that an acceptable level of control was not obtained (Table 1). The calcium treatments also reduced the severity of soft rot in the no AT plots. No effect was observed on the plots treated with the AT (Table 2). Tuber Yield and Internal Defects in Potato Variety Atlantic Monroe County, MI 1988 Treatment Yield(cwt/a) US#1 Yield(cwt/a) Total US#1 Sp.Gr. IBS% First Planting Second Planting Anti-transpirant (-) Antitranspirant (+) Calcium 1(0 lbs) 2(750 1bs,P) Calcium Calcium 3(750 1bs,H) 4(750 1bs,P+H) Calcium 275 284 270 289 296 278 276 269 339 353 332 359 360 343 344 336 81 80 81 81 82 81 80 80 1.073 1.074 1.073 1.074 1.074 1.073 1.074 1.074 29 31 31 29 40 a 24 c 31 b 26 bc Chip Color 55 b 60 a 58 57 58 59 57 57 Higher percentage of chip defects in the first planting due to severe stem end browning. Frequency of hollow heart being very low, data was not analysed. TABLE 2 EFFECT OF CALCIUM AND ANTITRANSPIRANT ON SOFT ROT DEVELOPMENT TREATMENT WEIGHT OF DECAYED TISSUE (G) WEIGHT OF DECAYED TISSUE (G) 0 Ca 750 lb Ca (P) 750 lb Ca (H) SPLIT APPLICATION *AT=Antitranspirant NO AT* 1.79 1.45 1.60 1.46 AT* 1.87 1.93 1.83 1.89 Funding: Federal Grant Annual Report Improved Production and Utilization Technology for Michigan Potatoes USDA Project ORD. NO. 38543 and 40818 Soil Management through Tillage for Improved Quality and Yield of Potatoes and Erosion Control F. J. Pierce, C. G. Burpee, and R. W. Chase Crop and Soil Sciences Department Quality improvement of potatoes represents the major objective of potato growers in Michigan. A major factor affecting potato quality is the physical condition of the soil in the zone of rooting and tuber development. Wind and water erosion are serious problems on the sandy and organic soils which dominate potato acreage in Michigan. Conventional practices for potato production in Michigan use cover crops for overwinter protection of soil and limit plowing to spring primary tillage followed directly by planting to avoid excessive tillage and soil structure degradation. Michigan farmers, therefore, are well aware of the potential limitations of poor soil physical conditions and soil erosion. However, the potential for serious problems related to poor soil physical condition and erosion remain. Excessive traffic, often with heavy axle loads repeated over several years, has created compact soil conditions below the depth of normal tillage and degraded soil structure in the tillage zone. Soil erosion potential in Michigan from wind and water is highest during the period from tillage and planting to hilling or canopy closure when the soil is bare and unprotected. Tillage systems, designed to fracture soil in a zone in-the-row (zone tillage) and leave the interrow undisturbed with a cover of standing rye as protection against wind and water erosion, were evaluated in field experiments in 1985, 1986 and 1987. In 1985, zone tillage treatments tended to improve yield and quality of Russet Burbank potatoes although the 35.4 cwt/acre increase was not significant. In 1986, zone tillage treatments significantly increased yield of Russet Burbank potatoes up to 77.7 cwt/acre with a corresponding trend for improved quality. Related experiments in 1986 showed significant differences in size distribution due to seed spacing. In 1987, the effects of zone tillage on soil properties, plant development in Russet Burbanks and varietal response to zone tillage were evaluated in more detail. When plant spacing in the row was 14 inches, there were no differences in yield due to tillage. When planted at 10 inch plant spacing, Russet Burbank yields were significantly increased in both zone tillage treatments, 446.0 cwt/acre and 425.0 cwt/acre for the paratill and Bush Hog Ro-till treatments, respectively, versus 376 cwt/acre for the conventional tillage treatment. Specific gravity was low, averaged 1.067 g/cm3 overall, and was not affected by tillage. It would appear that zone tillage is beneficial to Russet Burbanks only when sufficient plant populations are present in the field. Root length density was significantly increased in the zone tillage treatments and increased just above the plow layer in the conventional tillage treatment. Yields of the Shepody variety were not affected by tillage although the paratill treatment resulted in significantly lower No. 1 potatoes than either the conventional or Bush Hog treatments. Yields of two round white potato varieties, Onaway and Atlantic, were significantly lower in the paratill treatments than the Bush Hog or conventional tillage treatments. These results suggest that the zone tillage offers a significant advantage over conventional plow systems for improved yield and quality of potatoes, for erosion control, and improved trafficability. However, questions remain about varietal response to zone tillage and seed spacing, zone tillage effects on plant development of the Russet Burbank variety, and the impact of plant residues on early growth and development in Russet Burbank potatoes. The objectives of this research for 1988 were (1) to develop and evaluate alternatives to existing tillage systems on sandy soils that improve tuber quality and yield and reduce the potential for wind and water erosion, (2) evaluate zone tillage and seed spacing effects on yield and quality of selected potato varieties, (3) to determine the impact of the physical environment induced by tillage on potato growth and development, and (4) to determine the effects of crop residues on potato growth and development. Methods/Procedures: Three field experiments were conducted in 1988 as described below: A. Effect of zone tillage on growth and development of irrigated Russet Burbank potatoes. Russet Burbank potatoes were grown under five tillage treatments replicated five times in a randomized complete block design. Tillage treatments included: conventional tillage (spring disk and moldboard plowing followed immediately by planting) and zone tillage, accomplished with the use of a Bush Hog Ro-till in the fall or spring and a paratill in the spring either pre- or post-planting (note, only final yields taken on this treatment). Russet Burbank potatoes were hand planted at 10 inch seed spacings. Whole plant samples were taken for above and below-ground biomass (including root weight and tuber numbers, weight and size distribution) determination from ten feet-of-row three times during the growing season at approximately three week intervals beginning at early bloom stage. Petiole samples were taken for nutrient analysis at early bloom stage. Roots were measured bi-weekly to weekly using mini­ rhizotron techniques on .4 inch increments to a depth of three feet and mechanically three times during the growing season at 3 inch intervals to 17 inch depth. Tuber yield and quality were measured by harvesting 2 rows 50 feet long from each plot and determining size distribution, specific gravity and incidence of hollow heart. Soil moisture was monitored throughout the growing season using tensiometers and a neutron probe and used to schedule irrigation. B. Effect of zone tillage on growth and development of non-irrigated Russet Burbank potatoes. Russet Burbank potatoes were grown under conventional and zone tillage (paratill) in five replications in a randomized complete block design. Russet Burbank potatoes were hand planted at 10 and 14 inch seed spacings. Whole plant samples were taken for above and below-ground biomass (including root weight and tuber numbers, weight and size distribution) determination from ten feet-of-row three times during the growing season at approximately three week intervals beginning at early bloom stage. Petiole samples were taken for nutrient analysis at early bloom stage. Roots were measured mechanically once during the growing season at 3 inch intervals to 17.75 inch depth. Tuber yield and quality were measured by harvesting 20 feet long from each plot and determining size distribution and specific gravity. C. Zone tillage and seeding rate effects on selected potato varieties. Four varieties - Russet Burbank, Shepody, Atlantic, and Onaway - were grown in conventional tillage and two zone tillage (spring Bush Hog and paratill) tillage treatments at plant spacings of 10 and 14 inch for the Russet Burbank and Shepody varieties and at 6 and 8 inch for the Onaway and Atlantic varieties. All cultural practices such as fertilizer and pest control followed recommended practices for each variety. At harvest, size distribution, specific gravity and incidence of hollow heart were measured on potatoes harvested from two 50 foot rows for each tillage, variety, and seeding rate treatment. Results: Zone Tillage Effects on Soil Physical Properties The effects of zone tillage on the physical properties of the McBride soil are shown in Figures 1 and 2. Intact soil cores for bulk density determination were sampled directly in the potato row which corresponds to the zone of maximum loosening in the zone tillage treatments. Figure 1 plots a histogram of bulk density for each tillage treatment for the 0-3, 4-7 and 9-12 inch depths. Bulk density was not significantly affected by tillage system in the 0-3 and 4-7 inch soil depths. However, bulk density was reduced by zone tillage in the 9-12 inch depth from 1.78 g/cm3 to approximately 1.6 g/cm3. All zone tillage treatments were significantly different from conventinoal tillage at this depth. The fall paratill treatment (PTF) was significantly lower in bulk density than the spring paratill (PTS) and the spring Bush Hog (BHS) treatments indicating improved loosening of soil when zone tillage is done in the fall under drier moisture conditions. Penetration resistance of the soil was measured using a cone pentrometer at the same time soil cores were sampled for bulk density determination. Cone index is plotted versus soil depth from the top of the potato hill for each tillage treatment in Figure 2. The higher the cone index the higher the soil strength. The major point of the graph in Figure 2 is the dramatic increase in soil strength (higher cone index) between 25 and 30 cm (10 - 12 inches) depth below the hill. By 30 cm (12 inches), the soil strength was too hard for the penetrometer to penetrate the soil. This soil then has a compact layer at approximately 10 to 12 inches characterized by high bulk density and high soil strength, both of which will limit root growth and penetration. The cone index below 30 cm (12 inches) in the zone tillage treatments is at reasonable levels for root growth indicating that zone tillage has at least temporarily removed the soil compaction problem in this soil. Zone Tillage Effects on Potato Development and Yield In the irrigated study, yields of Russet Burbank potatoes (Table 1) were significantly lower in conventional tillage (347.9 cwt/acre) than Bush Hog fall (361.3 cwt/acre), Bush Hog spring (374.6 cwt/acre), or paratill spring pre-plant (373.7 cwt/acre). Yields of paratill post­ plant were significantly lower than all tillage treatments (331.8 cwt/acre) indicating tillage after planting may be detrimental to yield but this practice of post-tillage needs further evaluation. Specific gravities of Russet Burbanks was significantly higher in the Bush Hog spring (BHS) treatment than fall Bush Hog (BHF) and the conventional tillage (Conv) treatment. The whole plant biomass (Table 2) showed zone tillage treatments produced larger tubers than conventional tillage. Dry weight ratios of tubers to above-ground biomass were higher for the zone tillage treatments early in the season but lower than conventional tillage in the mid to late season. Root data for 1988 are being processed at this time. In the non-irrigated study, record drought conditions resulted in plant stress and low tuber production in Russet Burbank potatoes during the major portion of the growing season. Potatoes produced in the non­ irrigated plots were small, deformed and unmarketable. However, significant differences in growth and development were measured due to tillage and seed spacing. Conventionally tilled potatoes and those at the 14 in seed spacing were bigger and had more tubers at the plant sampling dates, being significantly different at the early and mid-season sampling dates only (Table 3). At harvest, zone tillage produced significantly fewer tubers but a higher yield than conventional tillage (Table 4). Plants at the lower seeding rate (14 inch seed spacing) were larger and produced more tubers at the three whole plant sampling dates. However, there were no significant differences in potato yield due to seed spacing. Yield and quality of Russet Burbank, Shepody, Onaway, and Atlantic potatoes as affected by tillage and seed spacing are given in Tables 5, 6, 7, and 8 respectively. Yield differences in varieties due to tillage were found only in the Shepody variety where the yield of No 1 potatoes was reduced in the paratill treatment (PTS). This reduction was also observed in the Shepody variety in 1987. Specific gravities were also significantly higher in conventional tillage than zone tillage for the Shepody variety. This would indicate that zone tillage, in the form used in these studies, is not well suited to the production of Shepody potatoes. Yield data for the Russet Burbank variety does not agree with results from experiment A and may be due to canopy effects of different varieties in adjacent plots. At harvest time, it did appear that plants in adjacent rows influenced yields. It seems clear from these data that variety trials with two rows are confounded by edge effects and do not allow for a rigorous assessment of tillage effects on yields. Plot size should be increased in the future so that each variety has guard rows bordering the two harvest rows. Seeding rate increased yield and quality of the Onaway variety but had little effect on the other varieties. Specific gravity of Onaways was signficantly higher (1.071 versus 1.069 g/cm3) at the 6 inch seed spacing than the 8 inch seed spacing. Figure 1. Effect of Zone Tillage on bulk density Figure 2. Penetration resistance (cone index, KPa) of a McBride sandy loam as affected by tillage. Table 1. Yield and quality of Russet Burbank Potatoes as affected by tillage in 1988. <4 ozcwt/acreSize Class Size Class 4-6 ozcwt/acre Size Class Size Class >10 oz 6-10 ozcwt/acre Pick Outs Pick Outs <10 ozcwt/acre >10 ozcwt/acreTotalcwt/acre 84.7a 83.9a 75.8a 77.6a 72.3a 113.3a 104.4ab 108.8a 101.7ab 88.3b cwt/acre 12.5a 20.5a 17.84a 25.0a 21.4a 70.4a 84.7a 73.1a 84.7a 62.4a 49.1a 56.2a 61.5a 50.0a 58.0a 16.9b 25.9ab 24.1ab 27.7ab 29.4a 347.9bc 374.6a 361.3ab 373.7a 330.9c Tillage Conv. BHS BHF PTS PTP empty table cell Hollow Heart Plant Population Yield/ Plant #l’s #l’s% Specific Gravity #/10 plants/acre lbs cwt/acre Conv. BHS BHF PTS PTP 0.4a 0.4a 0.2a 0.4a 0.0a 18247ab 18186ab 18432a 17848b 18125ab 1.92c 2.07ab 1.96bc 2.09a 1.83c 197.1a 208.7a 199.8a 210.5a 172.2b 56.5a 55.5ab 55.2ab 56.3a 51.8b 1.066b 1.069a 1.066b 1.067ab 1.067ab Table 2. Tuber wet weights and above ground biomass dry weights of Russet Burbank potatoes as affected by tillage at three sampling dates in 1988. empty table cell Sampling Dates Sampling Sampling Dates 7/6 Above ground Biomas 7/6 Tuberslbs/10 ft row Sampling Dates s lbs/10 ft row 7/25 Tuber Dates 7-25 Above ground Biomas Sampling Dates 8/19Tubers lbs/10 ft row Sampling Dates 8/19 Above ground Biomas s lbs/10 ft row Conv BHF BHS PPS 8.3 7.6 6.5 6.3 1.4 1.5 1.2 1.2 s lbs/10 ft row 16.8 14.1 15.5 15.0 slbs/10 ft row 1.7 1.5 1.9 1.7 23.3 24.4 24.6 24.4 1.2 1.4 1.30 1.4 Table 3. Dry tuber(T) and aboveground biomass per plant(A) of nonirrigated Russet Burbank potatoes as affected by tillage and seeding rates. 7/14 Sampling Date Sampling Date 8/2 T Sampling Toz/plantSampling Date7/14 Aoz/plant oz/plant Sampling Date8/24 T oz/plant Sampling Date8/24 Aoz/plant 9/15 Sampling Date Harvest Tubersoz/plant Tillage Seeding Rate (in) CT BHS CT BHS 10 14 10 14 .648a .875b .648a .809b .809a 1.069b .582a .680b 1.102a 1.166a 0.875a 0.777a Date 8/2 Aoz/plant 1.232a 1.394b 1.069a 1.458b 1.976a 2.592a 1.750a 2.333a 0.972a 1.523b 0.907a 1.491b 1.782a 2.494b 2.333a 3.078b LSD (.05) for tillage empty table cell NS .270 .166 NS NS NS .062 Table 4. Yield of non-irrigated Russet Burbank potatoes as affected by tillage and seeding rate. Till Seed Rate (in) CT CT BHS BHS 10 14 10 14 Seed Size (oz) <.07ozcwt/acre Seed Size (oz).07-2.0ozcwt/acre Seed Size (oz) Seed Size (oz) Seed Size (oz)6-8ozcwt/acre 2.0-4oz 4-6ozcwt/acre Seed Size (oz)Totalcwt/acre Harvest Yield cwt/acre cwt/acre 49.1a 41.9b 48.2a 37.5 16.1a 18.7a 23.2a 25.0 4.5 5.3 9.8 11.6 0.0a 1.8a 4.5b 7.1b 2.7 1.8 1.8 2.7 69.6a 67.8a 85.6a 81.2a 106.0a 102.0a 129.1a 122.7a Table 5. Yield and quality of Russet Burbank as affected by tillage and Seed Class (oz) 4-6 cwt/acre Seed Class (oz) 6-10 cwt/acre Seed Pick Outs <10 cwt/acre Pick Outs >10 cwt/acre Total cwt/acre 10 14 10 14 10 14 108.8 71.4 72.3 73.1 78.5 62.4 99.0 88.3 87.4 84.7 85.6 77.6 Class (oz) >10 cwt/acre 9.8 14.3 8.9 8.9 8.9 11.6 83.8 91.0 74.0 95.4 75.8 83.0 44.6 50.8 68.7 56.2 47.3 49.0 13.4 20.5 12.5 13.4 18.7 24.9 358.6 335.4 324.7 333.6 314.9 309.5 seeding rate. Seeding Rate in Seed Class (oz)<4cwt/acre Tillage Conv. Conv. BHS BHS PTS PTS Hollow Heart #/10 0 0 0.3 0.3 0.3 0.3 Plant Population Plants/acre 17739 12877 17740 13032 18263 13078 Yield/ Plant lbs 2.00 2.60 1.81 2.60 1.70 2.40 #l’s cwt/acre 192.7 192.7 170.4 110.0 170.4 173.0 #1's % 53.6 57.5 52.5 57.0 53.9 55.6 Specific Gravity 1.066 1.066 1.066 1.065 1.068 1.064 Table 6. Yield and quality of Shepody potatoes as affected by tillage and seeding rate. Tillage Conv. Conv. BHS BHS PTS PTS Hollow Heart #/10 0.8 0.8 0.5 0 0.3 0.5 Seeding Rate (in) >10oz <4 ozcwt/acre4-6ozcwt/acre6-10ozcwt/acre Pick outs outs Pick <10ozcwt/acre >10ozcwt/acre Totalcwt/acre 10 14 10 14 10 14 33.9 25.0 35.7 29.4 26.8 26.8 Plant Populations plants/acre 17740 12893 17970 12970 18355 12816 cwt/acre 77.6 84.7 73.1 75.6 52.6 75.6 94.6 88.3 80.3 80.3 86.5 70.5 62.4 53.5 62.4 62.4 57.1 45.5 55.3 40.1 50.0 45.5 52.1 41.0 28.5 25.9 31.2 32.1 28.5 37.5 351.4 316.7 332.7 326.5 307.7 296.1 Yield/ Plant lbs 2.01 2.51 1.90 2.51 1.70 2.29 #l’s cwt/acre 234.6 226.6 215.9 218.5 196.2 190.9 #l’s % 66.4 71.5 65.0 67.0 63.6 64.0 Specific Gravity 1.072a 1.073a 1.069b 1.071b 1.069b 1.071b Table 7. Yield and quality of Onaway potatoes as affected by tillage and seeding rate. Tillage Conv. Conv. BHS BHS PTS PTS empty table cell Conv. Conv. BHS BHS PTS PTS Seed Spacing in Seed Seed Class Pick <2cwt/acre Seed Class (in) Class (in) (in) 2-3.3 cwt/acre >3.3 cwt/acre outs <3.3 cwt/acre Pick outs >3. 3 cwt/acre Total Yieldcwt/acre 6 8 6 8 6 8 25.8 21.4 25.8 25.8 27.6 22.3 320.2 294.3 306.8 296.1 299.7 278.3 15.1 14.3 14.3 20.5 18.7 24.1 Plant Population plants/acre 29079 21617 28817 20663 28232 21048 Yield/ Plant lbs 1.323 1.610 1.191 1.698 1.323 1.610 #l’s cwt/acre 335.4 308.6 321.1 316.7 318.4 302.4 8.0 8.0 8.0 9.8 12.5 24.1 #1 % 90.7 91.1 90.3 89.9 88.2 89.9 .9 .9 .9 .9 1.8 .9 369.3 339.0 355.0 352.3 360.3 337.2 Specific Gravity 1.071a 1.069b 1.070a 1.069b 1.071a 1.069b Table 8. Yield and quality of Atlantic potatoes as affected by tillage and seeding rate. Tillage Seed Spacing in Size Class (in) 2-3. Size Class Size Class (in) <2cwt/acre 3cwt/acre (in) Pick Outs Pick Outs <3.3 >3.3cwt/acreTotalcwt/acre Conv. Conv. BHS BHS PTS PTS >3.3 cwt/acre cwt/acre 35.7 31.2 33.9 33.9 30.3 26.8 302.4 304.2 306.8 300.6 303.8 291.7 21.4 25.9 16.0 20.5 20.5 25.9 15.1 11.6 16.0 8.9 18.7 22.3 6 8 6 8 6 8 Conv. Conv empty table cellHollow Heart #/10 2.0 0.8 1.5 0.8 1.3 2.0 PTS PTS BHS BHS Plant Population Plant/acre 28817 21002 27740 20694 28002 20817 Yield/ Plant lbs 1.301 1.808 1.301 1.808 1.301 1.808 #1 cwt/acre 323.8 330.0 322.9 322.0 323.8 317.5 #1 % 86.0 88.4 86.7 88.2 86.6 85.8 1.8 .9 .9 .9 .9 2.7 376.4 372.8 372.8 364.8 373.7 369.3 Specific Gravity 1.084 1.086 1.086 1.086 1.085 1.087 Funding: MPIC COLORADO POTATO BEETLE MANAGEMENT E. Grafius, B. Bishop, P. Ioannidis, and P. Rattlingourd Department of Entomology Michigan State University Summary: Research in 1988 included: 1) analysis of inheritance of insecticide resistance. 2) preliminary investigations of the effect of different potato cultivars on larval growth and survival. 3) development of an insecticide-resistance test kit for use by growers, and 4) evaluation and registration of new insecticides for Colorado potato beetle control. 1) Results indicate that resistance to both Guthion and Furadan is inherited as dominant genes. Both resistance genes are also probably carried on autosomal (non-sex) chromosomes. Resistance genes appear to already exist in nature at very low levels (approximately .001%). 2) Growth and survival of beetle larvae is influenced by the particular potato cultivar they feed on. The degree of insecticide resistance may also affect the probability of larval survival on different cultivars, with insecticide-resistant larvae more likely to survive to pupation. 3) Resistance tests of beetle populations collected from Michigan potato fields show that approximately half of all populations tested are resistant to Furadan that resistance to Imidan may be very widespread, and that moderate to high levels of Asana resistance are present in many populations. 4) Some of the new insecticides evaluated in 1988 were: Trident (a bacterial spore preparation), and Trigard (an insect growth regulator). Practical applications: The dominant inheritance of resistance indicates that resistance can increase very rapidly in the field. Since resistance to Guthion, Furadan and Asana usually result from different mechanisms, alternation of these chemicals will help slow resistance development. PBO (piperonyl butoxide) is effective as a synergist for Guthion (and other organophosphates, such as Imidan) and for some types of Asana resistance. PBO was widely used in the field in 1988 and was very effective. New labels were obtained in 1988 for PBO, Rotenone & PBO, and M-l (a new bacterial product). Emergency labeling was obtained for Kryocide/cryolite in 1988 and will be pursued again in 1989. Results from petri dish test kits indicate that roughly half of the fields tested had very high levels of Furadan resistance. Asana and Imidan resistance was also widespread. 1) Inheritance of Insecticide Resistance in Colorado Potato Beetle Studies were conducted to determine: the mode of inheritance of resistance to different insecticides (i.e., the extent of dominance or recessiveness), whether the resistance genes are associated with sex-linked or autosomal chromosomes, and whether resistance is controlled by one gene or is polygenic. Guthion (an organophosphate) and Furadan (a carbamate) were used in the studies. These insecticides are widely used in Colorado potato beetle control programs. In Michigan they have been effective, although there are some instances where beetles have developed more than a 500-fold resistance to these insecticides (Table 1). TABLE 1. RESISTANCE LEVELS OF DIFFERENT STRAINS OF COLORADO POTATO BEETLES. INSECTICIDE BEETLE STRAIN Guthion Long Island (Resistant) Long Island (Resistant) Furadan Guthion Montcalm (Resistant) Montcalm (Resistant) Furadan Guthion Furadan Vestaburg (Susceptible) Vestaburg (Susceptible) LD50 (µg/beetle) 556 >200 18.4 93.9 1.24 0.18 RESISTANCE RATIOb 448 — 14.8 521 - — a LD50 = That dose of the insecticide that kills 50% of the beetles. b Resistance ratio = LD50 of the resistant strain / LD50 of the susceptible strain The Colorado potato beetle strains used in these studies were originally collected from field populations, and later selected in the laboratory. VESTABURG SUSCEPTIBLE STRAIN (S): This strain is of Michigan origin and has been under continuous culture in our laboratory for about two years. LONG ISLAND STRAIN (R): This field collected strain was heterogeneous resistant to Guthion when it was collected two years ago. After repeated backcrossing, selection at 80 % mortality, and intercrossing for five generations, a (RR) homozygote has been produced. This gave rise to a steeper log probit-dose line. This is clearly demonstrated by comparing the slopes and the X2 values in the following regression evaluations. After the selections, b=3.01 (steeper slope) and X2 = 0.625 (very small)-strong indication for homogeneity. Before selection: Heterogeneous (SS, RS, RR) y=1.80 +1.18x (X2=7.14 D.F. 5), LD50= 489µg/beetle After selection: Homogeneous (RR) y=-3.26+3.01x, (X 2=0.625 D.F 5) LD50 =556 ug/beetle MONTCALM-C STRAIN (R TO FURADAN) This strain has been selected four times. Before the selection the beetles were heterogeneous susceptible with LD50 = 0.63 ug/beetle. The first selection was made by spraying the field with Furadan 4F at the recommended field rate. Approximately 40 to 50 larvae, out of an original 300,000 survived (99.9% selection), and were returned to the laboratory. Progeny from these original larvae have been selected four times with Furadan (80% mortality selection). In an extremely short time the beetles showed a steep dose-mortality line, and an 147-fold increase in resistance to Furadan (Table 2). These results support the preadaptive theory for development of resistance. Resistant genes preexist in the field in very low frequencies. Selection must act on the supply of genetic variants already in the population at the time the selection program begins, not on mutations that occur during the process of selection. The speed by which resistance to Furadan has occurred is characteristic of monogenic inheritance, compared with polygenic inheritance, which takes more time to develop. It is interesting that selection with Furadan also gives cross-resistance to Guthion. TABLE 2. INCREASE IN RESISTANCE OF THE MONTCALM STRAIN OF CPB TO FURADAN AND GUTHION DURING FOUR GENERATIONS OF SELECTION WITH FURADAN GENERATION FURADAN Before Selection Selection (in field) (mortality = 99.9%—larvae) Selection (in lab) (mortality = 80%—adults) Selection (in lab) (mortality = 80%—adults) P F1 F2 F3 0.6 34.8 93.9 > 100.0 LD50(µg/beetle) LD50(µg/beetle) GUTHION -.- 1.4 9.2 18.1 The two resistant strains include major resistance genes isolated from field collected populations that already have had extensive exposure to the specific pesticide. At this time the levels of resistance are very high and ranges of the dosage-mortality lines for the R and S strains are not overlapping. The successful identification of resistant genotypes and phenotypes depends, to a large extent, on the proper choice of a sensitive bioassay method. The FAO standard bioassay techniques for Colorado potato beetle were used. Insecticide toxicity was estimated by topical application, applying 2 microliters of a solution of technical compound in acetone. Probit analysis was used to estimate the LD50's (amount of the insecticide that kills 50% of the population). The beetles were maintained, and the tests conducted, at 25 °C. Mortality was estimated after 3 days. The mass-cross technique, with about 20 pairs of beetles, was used. The reciprocal crosses between strains susceptible and resistant to Guthion gave almost identical results for the Fl progeny, confirming that resistance to Guthion is inherited as incompletely dominant, and appears to be carried on autosomal (non-sex) chromosomes (Figure 1). VESTABURG FEMALES (SUSCEPTIBLE) X LONG ISLAND MALES (RESISTANT) VESTABURG MALES (SUSCEPTIBLE) X LONG ISLAND FEMALES (RESISTANT) FIGURE 1. LEVELS OF RESISTANCE TO GUTHION IN OFFSPRING (Fl) AND PARENTS OF A CROSS OF SUSCEPTIBLE (VESTABURG STRAIN) AND RESISTANT (LONG ISLAND-LI STRAIN) COLORADO POTATO BEETLES. We repeated the crosses and applied a synergist, piperonyl butoxide (a specific inhibitor of mixed-function oxidase enzymes), with the Guthion to the Fl progeny. We got very good synergistic ratios, almost returning the resistant Fl progeny to the susceptible level (Figure 2). VESTABURG (SUSCEPTIBLE) MALES X LONG ISLAND (RESISTANT) FEMALES FIGURE 2. LEVELS OF RESISTANCE TO GUTHION ALONE, AND TO A COMBINATION OF GUTHION AND PBO IN OFFSPRING (Fl) OF A CROSS OF SUSCEPTIBLE (VESTABURG STRAIN) AND RESISTANT (LONG ISLAND STRAIN) COLORADO POTATO BEETLES. Extensive synergistic and physiological studies using both the Long Island and Macomb County resistant strains of beetle have shown that mixed-function oxidases are the main mechanism responsible for Guthion resistance. Reciprocal crosses between carbofuran-selected resistant beetle strains (Montcalm), and the Vestaburg susceptible strain showed that Furadan resistance was incompletely dominant, and appeared to autosomal (Figure 3). Our work on Furadan resistance is under progress and we expect to complete very soon the studies involving backcrossing and analysis of the F2 progeny. This will give us a more precise picture of the inheritance of Furadan resistance. MONTCALM FEMALES (RESISTANT) X VESTABURG MALES (RESISTANT) VESTABURG FEMALES (SUSCEPTIBLE) X MONTCALM MALES (RESISTANT) FIGURE 3. LEVELS OF RESISTANCE TO FURADAN IN OFFSPRING (Fl) AND PARENTS OF A CROSS OF SUSCEPTIBLE (VESTABURG STRAIN) AND RESISTANT (MONTCALM STRAIN) COLORADO POTATO BEETLES. From the practical standpoint, accumulation of knowledge of formal genetics of resistance in the Colorado potato beetle will provide essential background on recommendations for control, and the design of an appropriate integrated pest management program for this very serious pest. 2) Effect of Potato Cultivar on Larval Growth and Survival Rate The growth and survival of Colorado potato beetle larvae when fed on three different potato cultivars were compared. Both insecticide-resistant and susceptible strains of beetle were used to assess whether there is a relationship between resistance to insecticides and to plant chemicals present in potato foliage. Larvae were kept in petri dishes, fed daily on freshly-excised potato foliage, and weighed every day or two. Survival rates of resistant beetle larvae were higher on the cultivar Conestoga than on Onaway or Superior (Figure 4). Survival of the insecticide-suceptible strain of Colorado potato beetle was very poor on all cultivars (Figure 5). FIGURE 4. DAILY SURVIVAL OF INSECTICIDE-RESISTANT COLORADO POTATO BEETLE LARVAE (JP STRAIN) WHEN FED ON THREE DIFFERENT POTATO CULTIVARS. FIGURE 5. PERCENT SURVIVAL OF INSECTICIDE-SUSCEPTIBLE COLORADO POTATO BEETLE LARVAE (ANTRIM STRAIN) AFTER FEEDING FOR 10 DAYS ON THREE DIFFERENT POTATO CULTIVARS. Beetle larvae fed on the potato cultivar Superior were heavier than larvae fed on Onaway or Conestoga cultivars early in the larval period (Figure 6). Weights of beetle larvae fed on the Onaway cultivar were, at first, comparable to those of larvae fed on other cultivars, and then increased dramatically in comparison. Larvae fed Conestoga grew at a moderate rate for the first four days, and never grew very rapidly. Comparison of growth rates of susceptible and resistant strains of beetle were not directly possible because of the poor survival rates of the susceptible strains. However, the susceptible individuals that did survive attained the heaviest prepupal weights. Survival rate, therefore, may not be related to mature larval weight. FIGURE 6 WEIGHT OF INSECTICIDE-RESISTANT COLORADO POTATO BEETLE LARVAE WHEN FED ON THREE DIFFERENT POTATO CULTIVARS. In sum, both survival rate and growth rate of beetle larvae appear to be affected by potato cultivar. Although the low survival rate of insecticide-susceptible beetles prevents definitive conclusions, the resistance status of the beetle does appear to influence at least survival on different potato cultivars. Future plans for this work include comparisons of rates of larval growth, feeding, and survival between russet-type potatoes and small white potatoes, and comparisons between white varieities and colored varieties. The results of these and future studies will be useful in the future for developing Colorado potato beetle management recommendations and for consideration in future potato variety development. 3) Development of an Insecticide-Resistance Test Kit Test "kits" to enable growers to test Colorado potato beetles for resistance prior to insecticide application were developed and distributed in 1988. Each "kit" included separate tests to detect resistance to Furadan, Imidan (results also an indicator of Guthion resistance), Asana, and an Asana and piperonyl butoxide (PBO) combination. Each resistance test was composed of a petri dish containing a filter paper that had been dipped into a discriminating concentration of the insecticide (i.e., the insecticide concentration that killed susceptible beetles, but not resistant ones), and subsequently dried. When placed in the petri dish, adult beetles walked over the insecticide-treated filter paper and picked up the dried residue on their tarsi. Although some of the insecticide may have been ingested when the beetles groomed their tarsi, the primary method of insecticide exposure was through direct contact. Discriminating concentrations for each insecticide were determined by preliminary tests using laboratory and field-collected beetle populations of known resistance levels. For each insecticide, both resistant and suceptible strains were tested in petri dishes containing filter papers treated with a range of different concentrations of the insecticide. The range of concentrations usually included the field rate of the insecticide (assuming 30 gallons per acre application rate), but the discriminating concentration was not necessarily the same as the field application rate (beetles in the petri dish test were constantly exposed to the insecticide residue, unlike the situation in the field). In addition to resistance tests for the four insecticides listed above, each resistance test "kit" contained a thermometer (since temperature affects insecticide toxicity, this was to help growers keep the tests within the required temperature range of 70 - 80 °F), a 3-part carbonless form to record data and background information, a self-addressed, stamped envelope for mailing back the data, and instructions. Growers were instructed to collect beetles from their field, maintain them for about 24 hours on potato foliage, then add 20 beetles to each petri dish and record mortality 24 hours later. The instruction sheet explained how to interpret test results in terms of insecticide recommendations. Approximately 200 test kits were distributed to growers, to pest-control consultants, to extension agents, and to chemical company representatives during the summer of 1988. We received results from 51 of these tests. These results show that the vast majority of beetle populations tested were either very suceptible, or almost totally resistant to Furadan 4F (Figure 7). Only one population (out of 51 tested) showed mixed levels of resistance. This result agrees with our previous finding that resistance to Furadan can develop very rapidly in beetle populations. FIGURE 7. FIELD POPULATIONS OF COLORADO POTATO BEETLE TESTED WITH FURADAN 4F RESISTANCE TEST (8.0 G AI/L) Additional results show that resistance to Imidan may be very widespread in Michigan beetle populations (Figure 8). Of the 31 populations tested, only one showed a mortality of greater than 50% . FIGURE 8. FIELD POPULATIONS OF COLORADO POTATO BEETLE TESTED WITH IMIDAN 50 WP RESISTANCE TEST (1.6 G AI/L) Most field populations exhibited moderate to high levels of resistance to Asana (Figure 9), although a few of the populations were very susceptible. The addition of the mixed-function oxidase inhibitor, piperonyl butoxide (PBO) increased the suceptibility of most beetle populations to Asana. For a few populations, however, the addition of PBO had little effect. FIGURE 9. FIELD POPULATIONS OF COLORADO POTATO BEETLE TESTED WITH ASANA 1.9 EC RESISTANCE TEST (0.9 G AI/L) AND ASANA 1.9 EC & PBO 8 EC RESISTANCE TEST. The resistance test kit has proved valuable in two ways. First, the kit has provided growers, and others involved in Colorado potato beetle control, with an easy-to-use tool to help identify effective insecticides prior to application, and to assess reasons for control failure (for example, insecticide resistance vs poor spray coverage). Second, data generated from the use of this test has helped us document the extent and distrubution of insecticide resistance in Michigan beetle populations. Future development plans for the insecticide resistance test "kits" include additional insecticides, and field demonstrations. We plan to include more chemicals in the kit, especially an organochlorine insecticide (Thiodan) and an Imidan and PBO combination (To assess furthur the extent of and mechanism of Imidan resistance in Michigan beetle populations). Complete kits will be available early in the 1989 season so growers' insecticide decisions can be based on a knowledge of the resistance status of their particular beetles. In addition, we are planning field demonstrations in the summer of 1989. The purpose of these demonstrations will be to show the relationship between test kit results, and field effectiveness of an insecticide. 4) Evaluation and Registration of New Insecticides Insecticide-evaluation trials in 1988 were conducted at the MSU Montcalm Potato Research Farm in Entrican, MI. Trials included: evaluation of systemic insecticides, evaluation of foliar sprays to control first generation larvae, and evaluation of foliar sprays to control summer adults. Potatoes were planted on May 13,1988. Plots were 3 rows wide (34" row spacing) and 40 ft (foliar spray plots) or 50 ft (systemic insecticide plots) long. All plots received normal fungicide and herbicide treatments, and approximately weekly irrigation beginning June 6. Insects were counted on 2 randomly-selected plants from the center row of each plot several times throughout the season. Foliar sprays to control first generation larvae were applied on June 17, June 23, and July 1. Foliar sprays to control summer adults were applied on July 19 and July 26. Potatoes from the center row of each plot (except summer adult plots) were harvested and weighed on October 5. All systemic insecticides, except Thimet when applied as a sidedress at hilling, reduced the number of Colorado potato beetle larvae per plant (Figure 10). Since Thimet applied in furrow resulted in good control of Colorado potato beetle, the hot dry conditions characteristic of the Michigan growing season during 1988 probably prevented Thimet, when it was applied as a sidedress at hilling, from moving through the soil and becoming incorporated into the plant. The best control was given by Temik. FIGURE 10. NUMBER OF LARGE COLORADO POTATO BEETLE LARVAE PER PLANT ON 2 SAMPLING DATES IN 1988 FOR DIFFERENT SYSTEMIC INSECTICIDE TREATMENTS All foliar sprays reduced the number of first generation large Colorado potato beetle larvae per plant (Figure 11). The best control was given by: Imidan, a combination of a pyrethroid (Capture or Asana) and PBO, and the growth regulator Trigard. There were no significant differences in the number of beetles per plant among foliar treatments applied to control summer adults. FIGURE 11. NUMBER OF LARGE COLORADO POTATO BEETLE LARVAE PER PLANT ON 2 SAMPLING DATES IN 1988 FOR DIFFERENT FOLIAR INSECTICIDE TREATMENTS In addition to testing new insecticides in 1988, data from previous years research was used to obtain a section 18 emergency registration was obtained for Kryocide (cryolite). Also, M-l was, for the first time, registered for use on potatoes in Michigan. Funding Federal RESEARCH REPORT ON ARS/USDA COOPERATIVE AGREEMENT FOR SCAB RESEARCH R. Hammerschmidt, D. Douches, M.L. Lacy, L. Hanson, K. Ludlam F. Spooner and C. Wallace Research has been carried out on the scab disease with the following objectives: 1.Identify resistance to the scab disease that may be used in breeding potatoes for scab resistance. Determine the nature of the inheritance and the mechanism of scab resistance 2. Identify factors that are linked to the pathogenic ability of the scab pathogen that may be of help in understanding the development of the disease, the identification of the pathogen and in the mechanism of survival of the pathogen in the absence of the potato. 3. Evaluate cultural practices that may influence the expression of the scab disease. The following is a summary of the research that has been carried out to meet these objectives and to find a long-term solution to the scab problem. DISEASE RESISTANCE RESEARCH During the summer of 1987, named and numbered potato varieties were screened for scab resistance at a site on the MSU Soils Research Farm in East Lansing. The results of this trial is given in table 1. Several lines were shown to have some resistance to the disease based on a low number of infected tubers. A greenhouse screen was developed to help augment the screening process. In this screen, greenhouse potting mixture is mixed with a slurry of the pathogen. The mixture is placed into pots and seed pieces are planted in the soil mixture. After emergence of the plants, the pots are watered from the bottom to maintain the dryer conditions in the tuber zone needed for good infection. The results of two trials are presented in tables 2 and 3. This assay is relatively rapid and has the potential to allow screening of a large number of plants with a very uniform inoculum level. We are now working to develop a screen for plants at the seedling stage. Genetic studies are being carried out to determine the heritability of scab resistance using the greenouse screen. A diallel mating design using tetrapioid genotypes, is currently being used to determine the heritability of resistance. Haploid plants will be extracted from the tetrapioid clones that are being identified as having a high degree of resistance. These lines will be used to determine how many genes control resistance. We have prepared part of the greenhouse for photoperiod control. This will allow us to screen wild species of potato, which have a strict photoperiod requirement for tuberization, for resistance to scab. Identifying resistance in these wild species could provide valuable new sources of scab resistance. We have initiated studies on the biochemical and physiological basis for resistance to potato scab. We have been determining the levels of the antibiotic phenolic compound, chlorogenic acid, in the epidermis and periderm of young tubers. We have found that there is a correlation between the content of chlorogenic acid and the level of resistance to scab (Table 4). The correlation is not completely without exception, and this may represent the fact that scab resistance may be composed of several components. Understanding the mechanisms of resistance will enable us to use biochemical markers to help select for resistant varieties. This information may also be of great help in improving the control strategies. Understanding how resistance works may enable us to enhance the expression of resistance by genetic means or even cultural practices. Scanning electron microscopy of young tubers being infected by S. scabies has been used to try to determine when infections do take place and if there are any obvious differences between resistant and susceptible varieties. For this work, the varieties Shepody (susceptible) and Krantz (resistant) were used. The surface of young (ca. 0.5 inches in diameter), infected tubers were observed via SEM. The apex of the tuber and the zone where stomata differentiate into lenticels appear to be the areas where most infections take place in the susceptible variety. The part of the tuber where the periderm is beginning to suberize and the lenticels are maturing did not appear to harbor any infections. In the resistant variety, the stomata appeared to close in response to the presence of the pathogen (thus physically blocking its invasion). The colonization of lenticels in the area where stomates are differentiated into young stomates was found to be reduced when compared to the susceptible plants. Although these results are very preliminary, they do support the role of a preformed toxic compound in resistance as well as physical barriers in preventing invasion of the young tuber tissue. STUDIES ON THE BIOLOGY OF THE PATHOGEN Understanding the biology and physiology of the pathogen is needed to aid the development of resistant varieties as well as in finding better means to identify the pathogen (unfortunately, when grown in culture, the pathogen looks vary much like non-pathogenic. Streptomycetes) . This work is also carried out to determine if the pathogen may exist in different forms that have different levels of virulence on potatoes. Twenty-four single spore isolates of Streptomyces were collected form disease tubers from several locations in the state. The isolates were tested for pathogenicity on three varieties of potato (monona, atlantic and shepody). The isolates were also tested for their ability to produce pigments on peptone-yeast-iron agar, growth on various carbohydrates and their ability to degrade pectin. The latter was done since the invasion of tuber tissue by the pathogen appears to require the degradation of pectin in the tuber tissue by the pathogen. One trial was also run directly comparing several pathogenic isolates for differences in pathogenicity on the same variety. Many, but not all of the isolates from scab lesions were pathogenic. We found that there was a good correlation between the ability of an isolate to cause scab disease and its ability to produce pigments on PYI media. We found an even better correlation between the ability of the pathogenic isolates to use sucrose as a carbon source. The non-pathogens grew very poorly, or not at all, on this sugar. This observation is of interest, since sugars are tranlocated to the tuber in the form of sucrose before they are converted to starch. Although it is too early to draw firm conclusions, the ability to use sucrose may help explain why the pathogen may try to infect the tuber as it develops. These results will be of use in developing a screen for pathogenic isolates as well as in the understanding of how the pathogen initiates disease. Pathogenic variability was also observed. Simultaneous comparison of eleven pathogenic isolates on the Atlantic variety showed that symptoms ranged from superficial scabs through severe pitting (Table 5). Development of more virulent isolates of the pathogen may explain, in part, why some varieties (e.g. Onaway) are exhibiting more scab than previously observed. Since variation does appear to occur, we have begun to study the genetics of virulnce and pathogenicity. Using DNA isolated from several isolates of S. scabies and non-pathogenic Streptomycetes, we have carried out restriction enzyme digestions of the DNA. Analysis of the digested DNA by agarose gel electrophoresis has shown that there are some major differences between the pathogens and saprophytic non­ pathogens. The pathogens, however, appear to show similar patterns. These results suggest that we can easily distinguish pathogens from non-pathogens at the molecular level. This work will also help us determine which genes make the pathogen a pathogen and not a saprophyte, how virulence may change and if pathogenicity can be transferred from the pathogen to a saprophyte. EFFECT OF SELECTED CULTURAL PRACTICES ON SCAB Over the last sveral years, we have shown that the use of the acid forming N source, ammonium sulfate, and use of proper soil moisture during tuber initiation and expansion leads to the expression of less scab on the tubers. During the last year, an experiment to examine the effect of the preceding crop on sdcab development. Due to timing, plots were seeded with various crops one month before planting potatoes. Just prior to planting potatoes, these cover crops were plowed into the soil. Even this short period of growth markedly influenced the xpression of thedisease. The most severe scab was observed in the plots where red clover had been planted. In decreasing severity from red clover was corn, fallow control, rye, alfalfa and oriental mustard. The latter crop was included since it is known that toxic compounds in mustards can decrease the population of some soil pathogens as well as the potential use of another mustard, canola, as a cash crop in michigan. Similar severity with red clover was observed in the legume rotation plots we analyzed for Hesterman and Griffin. This is also in agreement with other studies on rotation and scab disease as well as observations by growers. The results are presented in Table 6. Current work also involves trying to determine why some of these crops enhance the level of scab while others appear to lessen the severity. CONCLUSIONS The work carried out thus,far has been a combined effort from several approaches to attempt to find a solution to the scab problem. We have identified sveral good sources of resistance that may be useful in the breeding program. We have also made some progress into understanding the nature of disease resistance and the mechanism of infection and pathogenicity by S. scabies. We have also demonstrated that certain crops that precede potatoes can have a positive or negative influence on the severity of scab in the following potato crop. This is the first major effort to try to control scab by the simultaneous study of a number of factors that are important in this disease and its development. At present we can recommend that scab severity can be reduced through the use of several measures when used together: these include maintainting soil moisture levels below 50 cb from emergence until 6-8 weeks after emergence, the use of ammonium sulfate as the N source, using the most resistant variety of potato availabe, and using a rye cover crop. It is very clear that red clover should not be a part of the rotation. Alternate legumes, such as alflafa, appear to be better with regard to scab severity. 1987 FIELD EVALUATION FOR SCAB RESISTANCE TABLE 1 VARIETY NY 7 2 D195-24 TND22-5 BR7093-24 TC 582-1 D191-2 ND 2109-7 A7691-1 A7411-2 NY 79 A 79141-3 NY 81 WNC 521-12 WNC 672-2 NY 71 CO 81103-1 NORGOLD RUSSET WIS 848 MS 401-2 MS 402-6 HILITE RUSSET NORCHIP SANGRE SHEPODY RUSSET NORKOTAH LAO0-38 ERAMOSA A79341-3 MS 401-3 SAGINAW GOLD MS 401-1 MS 402-7 KRANTZ ONAWAY MS 401-8 ATLANTIC MS 401-4 MS 716-15 A 76147-2 MICHIGOLD MN 10874 MS 401-7 MS 700-83 MS 702-80 ROSEGOLD MS 401-6 MS 401-5 NORKING RUSSET MS 402-8 % TUBERS 0 SCAB %TUBERS 5%SCAB 53 60 45 46 100 73 45 57 83 42 89 41 53 56 58 46 65 72 72 76 95 26 82 60 75 63 62 68 58 75 25 41 88 96 71 73 83 69 84 68 67 96 71 70 80 81 65 83 86 empty table cell 84 95 80 92 96 100 100 94 90 97 100 92 100 96 94 94 100 100 97 100 94 100 76 100 93 99 94 94 80 86 93 100 100 98 95 100 97 100 100 98 100 100 98 92 100 88 97 100 85 85 40 48 85 97 100 100 76 60 98 100 96 MS 402-2 CONESTOGA 95 WIS 855 80 100 MS 402-4 88 FL 657 100 A7414-4CP 100 ND 1859-4 100 ND671-4R 100 SH-1 88 AF236-1 100 MS 402-1 100 A76147-2 (THE FOLLOWING ARE ONE OBSERVATION ONLY) 100 9972-2B 85 B0045-6 100 AF875-16 100 BO237-1 72 BO178-14 82 B9792-8B 100 B0238-4 100 AF875-17 100 CS7639-1 63 B0256-15 100 B9792-15B 100 B0032-40 100 5470 100 D43 100 5452 100 W231 100 W879 76 W760 100 AF465-2 100 ALLAGASH RUSSET 100 MN2331 100 B9569-2 100 MN12838 100 MN82328 100 TOLAAS 100 ATD63-7 100 ATD63-2 80 25 60 17 16 30 60 60 75 25 30 83 86 100 57 82 33 33 79 13 67 75 67 95 95 84 96 GREENHOUSE SCREEN FOR RESISTANCE TABLE 2 VARIETY * RATING COMMENTS ** KRANTZ NY71 716-15 W855 SAG.GOLD LA01-38 MONONA RIDEAU 702-80 ATLANTIC NDD 277-2 SUPERIOR PUNGO MICHIGOLD 700-83 NY81 ONTARIO NORCHIP ND651-9 *Average per cent coverage of tubers **Most severe type of scab noted on tubers 0.0 11.0 18.0 3.6 4.3 9.3 15.2 0.6 1.7 4.4 17.0 2.0 8.0 17.3 8.3 9.3 1.0 10.3 25.0 NONE PITTING SURFACE SURFACE SURFACE SURFACE SURFACE SUPERFICIAL SUPERFICIAL PITTING PITTING SUPERFICIAL SURFACE PITTING PITTING SURFACE SUPERFICIAL SURFACE SURFACE TABLE 3 GREENHOUSE SCAB RESISTANCE SCREEN VARIETY LESION TYPE MONONA Y245.7 LEMHI PUNGO NOOKSAK SAG.GOLD. ONAWAY ONTARIO RIDEAU MICHIGOLD SUPERIOR 716-15 LA01-38 84S10 ND860-2 W5337.3 702-80 700-83 NORCHIP NDD277-2 COMMON, SURFACE NONE NONE COMMON, SURFACE COMMON, SURFACE RAISED LESIONS COMMON, SURFACE SUPERFICIAL SURFACE COMMON (IF PRESENT) RAISED SUPERFICIAL SURFACE RAISED, PITTED RAISED VERY SMALL, SUPERFICIAL PITTED PITTED NONE COMMON, SURFACE COMMON, SURFACE RAISED Of these varieties tested, Y245.7, Lemhi and 84S10 have the highest level of resistance. Superior, Rideau, and Ontario fall into the next group. Onaway, 702-80 (from past experience) are in the last group. All of the others are susceptible. RELATIVE CHLOROGENIC ACID CONTENT OF TUBER TABLE 4 APICAL TISSUE VARIETY CGA VALUE * LEMHI RUSSET RIDEAU MICHIGOLD ONAWAY ATLANTIC MS 700-83 *A320/MG FR WT 0.225 0.243 0.121 0.070 0.076 0.048 TABLE 5 EFFECT OF ISOLATE ON SCAB SEVERITY ON ATLANTIC LESION TYPE ISOLATE SEVERITY + 3S CON2 ONAWAY925 RPF RP DP2 F945 CON1 ATLANTIC DPW FIELD2 + ++ + + + + + + + + + + + + + + + + + + + + + + + + + + + SUPERFICIAL SURFACE SURFACE PITTED SURFACE/PITTED PITTED PITTED PITTED PITTED PITTED PITTED EFFECT OF PRE-PLANTING COVER CROPS ON SCAB INCIDENCE IN TABLE 6 ATLANTIC POTATOES COVER CROP * SCAB RATING ** RED CLOVER (7lb/A) CORN (7 lb/A) FALLOW CONTROL RYE (20 lb/A) ALFALFA (7 lb/A) ORIENTAL MUSTARD (20 LB/A 12.9A 11.4AB 9.1 BC 8.9 BC 7.9 C 6.8 C *A11 plots seeded to rye the previous fall. Cover crops were planted on May 14 following plowing in of. rye. Covers were plowed in on June 14 and immediately planted to potatoes. **0=no scab, 1=1-4%, 5=5-9%, 10=10-20%, 25=20-25% or above. INFLUENCE OF ENVIRONMENTAL FACTORS ON WOUND HEALING OF POTATO TUBERS IN RELATION TO STORAGE DISEASES Funding Federal Grant INVESTIGATORS: R. HAMMERSCHMIDT AND A.C. CAMERON OBJECTIVES: A. Evaluate the effect of elevated CO2 on the development of soft and dry rot diseases. B. Determine the effect of elevated CO2 levels on the expression of suberization-related enzymes and other biochemical changes in wounded tuber tissue. C. Evaluate changes in disease development by Erwinia carotovora and Fusarium solani 'coeruleum' as a function of time in storage. D. Examine the effect of preharvest, in-field treatments, on the wound healing ability and susceptibility of tuber tissue. E. Examine the influence of temperature on the rapidity of suberization in relation to disease resistance development. F. Examine the reaction of selected varieties to dry and soft rot infections. JUSTIFICATION Improper wound repair can lead to economic losses due to shrinkage (water loss) of the tuber and pathogen mediated decay. Wounds and bruises that occur during harvesting and handling can act as the sites for water loss and pathogen entry if these injuries are not properly suberized. Since the suberization process is known to produce an effective barrier to both water loss and infection, understanding the biology of this process in relation to the storage environment as well as to pre-harvest treatments of the plants is needed to improve the storability of the tubers. Our current knowledge in all of the objective areas is incomplete. PROCEDURES Biochemical and chemical methods Suberization studies were carried out using 2.1 cm diameter X 1.0 cm thick slices of tuber tissue prepared from surface sterilized tuber tissue. The slices were placed into chambers (20'C) and humididfied air or humidified air containing 4% CO2 were passed through at a constant flow rate. Samples were taken at daily intervals for the measurement of suberization or for the assay of suberization related enzyme activity. Suberization was measure by the thioglycolic acid assay detailed in the last report. Two enzymes believed to be involved in suberization (an acidic cell wall peroxidase [PO] and the cytoplasmic enzyme phenylalanine ammonia lyase [PAL]) were measured out of buffer extracts of acetone powder preparations of tuber tissue. The enzymes were both assayed spectrophotometrically or via isozyme staining in polyacrylamide gels (PO only). Infection and suberization studies Infection of wounds by Fusarium solani 'coeruleum' (Fsc) was monitored in relation to temperature and rate of wound healing. Wounded surfaces of tuber tissue were inoculated with a spore suspension of Fsc at intervals after wounding and holding at 18'C, after wounding and holding at 5'C, and various combinations of time and temperatures. Whole tubers were screened for resistance to soft and dry rots by injection of the tubers with a spore suspension of Fsc or with a cell suspension of Erwinia carotovora (Ec).For general screening, the tubers were held in air (Fsc screen) or under near anaerobic conditions (Ec screen). In some experiments, the whole tubers were placed in sealed containers through which humidified air or humidified air containing 4% CO2 were passed. Field treatments of plants which are thought to have positive effects of the storability of potato included calcium applications and foliar sprays with Metalaxyl. Tubers from calcium treated plants were obtained from R.W. Chase and G. Silva. These tubers were used in the types of assays described above. Studies on the effect of storage duration on disease development were carried out on whole tubers at monthly intervals for 9 months from the date of storage. Tubers were incoulated as described above for Ec and Fsc. RESULTS AND DISCUSSION Effect of elevated CO2 levels on soft rot and dry rot development Four per cent CO2 was found to increase the severity of soft rot development when compared to disease development in air. Tubers, which had been in storage less than four months, exhibited large spreading decay areas by four days after inoculation when incubated in 4% CO2. Soft rot inoculated tubers incubated in air showed little or no decay. Tubers that had been stored over six months were equally susceptible to soft rot regardless of the atmosphere. These results are in agreement with other observations that show the ability to heal wound and resist infection declines while in storage. Preliminary studies on older tubers incoculated with Fsc also showed no differential response to CO2 vs. air. These results support our previous findings that elevated CO2 in a storage, such as that generated by respiration during suberization, can promote development of soft rot. Effect of elevated CO2 levels on expression of suberization related enzyme induction Incubation of wounded tuber tissue in 4% CO2 was previously shown to inhibit the rate of suberization as shown by suberin deposition and other factors. Two enzymes needed for the synthesis of suberin were studied to evaluate the effect of CO2 on the regulation of suberization. PAL activity was found to be delayed in time of induction and the magnitude of the induction by alowing the tissues to incubate in the presence of CO2. The induction of the suberization specific peroxidase, the last enzymatic step in the synthesis of the major part of suberin, was delayed in the presence of CO2 as was the magnitude of induction. This is being pursued further as this particular enzyme appears to be a key factor in suberization rates. These studies have shown that the slowing of suberization by CO2 can be traced back, in part, to the expression of two enzymes that are involved in the synthesis of the suberin polymer. Effect of storage duration on disease expression Tubers of the Atlantic and Russet Burbank varieties were shown to gradually increase in the level of susceptibility over a period of six months with greater increases in the loss of resistance to infection between 7 and 9 months. Wound repair rates also slowed during storage, with the greatest decline in rate occurring after six months in storage. This work has demonstrated that the tubers, while in storage, gradually lose their ability to defend against disease and to induce the process of suberization when wounded. Effect of in-field treatments and genetic background on wound healing and disease response These experiments are in progress at the time of writing. Preliminary evidence suggests that additional calcium in the tubers will increase their resistance to soft rot decay. Similarly, metalaxyl appears to increase the resistance to infection by Fusarium through mechanisms not directly related to fungicidal activity of metalaxyl. This work suggests that in- field treatment of the plants may improve the storage characteristics of the tubers. Influence of temperature on suberization and disease development rates Inoculation of wounded tuber tissues at 18'C with Fsc has demonstrated that suberization is complete enough to effectively protect the tissue from infection by 4 days after wounding. Shifting the tubers from 18'C to 5'C prior to four days at 18'C also prevents infection but also greatly slows suberization. Decay, however, will proceed if the infected tissue is returned to the higher tissue. Infection of tissue at 5’C also results in little to no infection if the tissues are held at 5'C. Transfer of the infected tissues incubated initially at 5'C to the higher temperature after sevral weeks at 5'C will also allow disease to proceed agressively. These results suggest that although rapid lowering of the temperature will stop development of the disease, more disease may develop when the tubers are warmed to more ambient temperatures due, in part, to a slowing of the wound healing mechanisms. Funding Federal Grant What Consumers Want in Fresh Potatoes...Know-How Producers Can Use to Increase Market Share and Profitability Investigator: Mary D. Zehner, Department of Agricultural Economics Objectives: While the overall goal of the study was to suggest how the Michigan potato industry might best recover its share of the fresh potato market, specific objectives included: * Identify how Michigan white potatoes are positioned in the minds of consumers; i.e., positive and negative perceptions. * Discover underlying reasons for consumers' purchase patterns. * Learn what, if any, consumer needs exists which could provide the Michigan fresh potato industry with new opportunities to regain market share. Justification: The fresh fruit and vegetable industry in the U.S. has been experiencing significant growth during the last decade due to consumers' changing lifestyles and a desire for more healthful, natural foods. However, Michigan potatoes have not benefited from the increase "fresh" demand to the extent they could have. Today's consumers are increasingly demanding higher and higher quality merchandise in smaller packages or in bulk displays from which they can select any number items. Why do Idaho potatoes consistently command a higher price than their Michigan counterparts? Are Michigan producers of potatoes providing a less desirable product and/or packaging from the consumers' point of view? Competitors in other states have been continually upgrading the quality aspects of their products. Their product lines and packaging have been extended to meet consumers' demands for variety. Over time, this has enabled them to capture a greater share of the household and institutional markets. Michigan producers need to know what product characteristics and packaging options are most important to consumers, and then make appropriate changes. Methodology: Four focus groups were held with consumers of fresh potatoes, two with heavy users and two with light users. In this study, a heavy user was defined as someone who purchased ten or more pounds of fresh potatoes in an average month. A light user was defined as someone who purchased less than ten pounds of fresh potatoes in an average month. Respondents were recruited by telephone. Selected participants were adults most responsible for menu planning and meal preparation in their households. The groups were recruited to include a representation of age, employment patterns, household income and race. One heavy user and one light user focus group were held in Lansing and then duplicated in Detroit. The sessions were conducted by Bonnie J. Knutson, PhD. and were audio taped. The groups began at 5:30 and 7:30 p.m. and lasted between one and one- and-a-half hours. Members of Michigan Potato Industry Commission observed the sessions from behind a one way mirror. Focus group interviewing consists of bringing together a small group of people, normally 8 to 10 at a time. Then let them talk about a topic, idea product or concept. The unique advantage of focus group interviewing is the dialogue between participants. Members of the group listen and react to each other. Focus group interviews are not projectable in the statistical sense. They provide a base for designing a quantitative study. Conclusions and Recommendations: Findings from the four focus groups clearly demonstrate that there is no one single target market for Michigan potatoes. Instead, a wide spectrum of opportunities exist to address the varying needs and wants of consumers. While the question of how to most effectively address the specific interests of each segment needs to be further investigated, this study suggests that there are several common threads which can be utilized through all strategies. The Positive Image of Michigan Potatoes Promotion of fresh Michigan potatoes should incorporate the three aspects which consumers view as the product’s strengths. First, potatoes, in general are associated with "home, hearth and good food." National trends point to a return to the home (sometimes called "cocooning”) fueled by the baby boom generation being in the family formation stage. Additionally, interest in American and regional cuisines, freshness of food products and food as an art is on the rise. The Michigan potato industry should build on the homey image with the Michigan potato’s positive position of high price-value and good all-purpose product. Recent successful examples of similar efforts for other food product are Kellogg’s Corn Flakes (’’Taste corn flakes again for the very first time”) and Campbell’s Soups (’’Soup is good food”). The Need and Desire for Information Secondly there is an opportunity for an intensive educational program for consumers. People not only need, but want information that will teach them: More and new ways to prepare potatoes that stress (1) variety, (2) ease and convenience (time) in the preparation process, and (3) utilizing the microwave for more than just baking. Methods of storing potatoes in the home to prolong freshness and shelf life, including where to best store and the advantages and disadvantages of various locations. How to retain/enhance the nutritional value and the desireable taste characteristics without have to add on what consumers clearly recognize as high-calorie, low nutrition items. The part that greening of potatoes plays in the entire ground-to-table process. In this regard, the industry might also consider developing a more "market-friendly" term to identify the greening process. When many people think about vegetation greening, it is usually in a positive light, i.e., the trees are getting green, the tomatoes and apples are getting ripe (losing their green). But in the potato industry, greening is a negative process. This may cause confusion in the consumers' minds. Therefore, while the industry may continue to use and understand the term, a more effective name may be desirable in the marketplace. The most effective vehicles for informational materials seem to be at the point-of- purchase locations. Most participants indicated that small tear off sheets/cards placed places by the potatoes would be good. Some information if presented clearly and attractively could also be placed on the (paper) bag or on a paper insert in the bag. All educational materials must, of course, invite attention by suggesting that reading will be quick, easy and valuable. Improved Bagging Alternatives Thirdly, the Michigan potato industry should investigate the need for increasing bagging alternatives. Of particular appeal to light users would be the availability of a smaller (three pound) bag. In addition, development of a better potato bag should be explored. Characteristics of a superior bag would include (1) expanded visibility of all contents, (2) enhancement of the products shelf life and freshness and (3) prevention of any dirt present on the potatoes from escaping. Funding MPIC and PPG THE INFLUENCE OF CHLOROPROPHAM (CIPC) ON POTATO CARBOHYDRATES DURING COMMERCIAL PRODUCTION AND STORAGE J.N. Cash, N.K. Sinha and R.W. Chase Michigan State University Good sprout inhibition, in stored potatoes, can be achieved with proper Chloropropham (CIPC) application. CIPC influences many aspects of tuber metabolism, although, its effects on potato carbohydrates ‘has not been fully investigated. This effort was directed at determining changes in glucose, fructose, sucrose and fried chip color of CIPC treated Atlantic potatoes during storage. Atlantic potatoes were grown at the Montcalm Research Farm (Montcalm County, Michigan) and harvested late in September 1987. Potatoes given regular irrigation (approx. 9 in. of irrigation water), over the course of the growing season, were compared to highly irrigated (approx. 14 in. of irrigation water) potatoes during the study. Thirty pound samples from both regular and high irrigation treatments were placed in double mesh bags and buried three feet deep in a commercial storage bin at the Wayne Lennard & Son's Farm in Samaria, Michigan along with 15,000 hundred weight of Atlantic potatoes. Samples were arranged in the bin to give four replicates, with seven bags per replication. Five pound bags of Russet Burbanks, to be used only for CIPC analysis, were also buried with the Atlantic potato samples. After filling into the storage bin, potatoes were held for three weeks at environmental temperatures to allow for suberization. Potatoes were then treated with CIPC and storage was maintained at 50°F (10°C) and 90% relative humidity for the duration of storage. Sampling was done 24 hours prior to CIPC application and 2, 30, 60 and 150 days after CIPC application. At each sampling, 4-5 tubers were analyzed for glucose, fructose and sucrose using a YSI Model 27 analyzer. Color of the processed potato chips, prepared from 4-5 tubers, was determined at each sample time, using an Agtron Colorimeter. Specific gravity was determined by a standard weight in water method (PC/SFA Procedure) and CIPC analyses were done by PPG Industries, Inc. (Barberton, OH). SUGAR ANALYSIS Figures 1 and 2 show glucose, fructose and sucrose changes of the Atlantic samples during storage. The glucose content in both regular and high irrigation was very low at the outset and remained almost unchanged throughout the study. However, the sucrose content increased by almost 25% during storage of both treatments. The fructose content, which was moderate at the time of storage in both treatments, decreased by 36% for the regular irrigation treatment and 26% for the high irrigation treatment. The sucrose content was higher in the regular irrigation samples than in the high irrigation tubers. The changes in glucose do not appear to be significant in this study. However, the concentration of fructose and sucrose was consistently higher. Further study is required to determine if increased fructose and sucrose concentration is due to stress during storage or specifically due to CIPC application. The accumulation of sugars (especially the reducing sugars, glucose and fructose) in chipping potatoes, can result in dark colored chips and a loss in chip quality. Reducing sugars react with amino acids to produce undesirable dark compounds during cooking. It is these dark compounds which produce an unacceptable darkening of chips during frying. COLOR & SPECIFIC GRAVITY Table 1 shows the chip color and specific gravity values obtained. Color of chips made from the tuber samples reflected the low to moderate reducing sugar concentration. The regular irrigation samples gave excellent to acceptable chip color. High irrigation samples also gave acceptable chip color except in one case. The average specific gravity over the storage period was slightly higher for regular irrigation (1.087) than for high irrigation (1.083) samples but the treatments were not different. CIPC RESIDUES Comparisons of 1986 and 1987 CIPC residues, as determined by PPG Industries, are shown in Table 2. It can be seen that the beginning residue levels varied somewhat between the two years. The initial concentration was almost twice as high in 1986 as in 1987. By 30 days of storage residues were approximately the same for both years and continued to be comparable at 150 days. However, active sprouting had begun by 120 days of storage in 1986 but sprouting was not present at 150 days of storage in 1987. TABLE 1. AGTRON CHIP COLOR ANO SPECIFIC GRAVITY OF ATLANTIC POTATOES IN STORAGE, LENNARD FARM, 1987 SAMPLE TIME AGTRON1 SPECIFIC GRAVITY2 AGTRON SPECIFIC GRAVITY REGULAR IRRIGATION REGULAR IRRIGATION HIGH IRRIGATION HIGH IRRIGATION 24 Hours Before CIPC 62 3 2 Days After CIPC 30 Days After CIPC 60 Days After CIPC 150 Days After CIPC 56 56 64 62 1.086 1.087 1.086 1.086 1.088 55 56 53 66 60 1.084 1.085 1.082 1.081 1.084 1 Agtron Color > 60 = Excellent; 56-60 = Acceptable; 50-55 = Marginal 2 All specific gravity values are averages of 3 samples 3 Average of 3 values TABLE 2. COMPARISON OF CIPC RESIDUES FROM 1986 AND 1987 ATLANTIC POTATOES IN STORAGE, LENNARD FARM DAYS AFTER CIPC APPLICATION 1987 1986 REGULAR IRRIGATION 1987 HIGH IRRIGATION REGULAR IRRIGATION 2 30 60 150 6.0 PPM 1 4.6 PPM 4.1 PPM 1.8 PPM 5.6 PPM 3.9 PPM 2.8 PPM 1.6 PPM 11.0 PPM 4.1 PPM 3.5 PPM 1.5 PPM 1 Average of 4 values Figure 1. Carbohydrate Content of Atlantic Potatoes in Storage, Lennard Farm, 1987. Figure 2. Carbohydrate Content of Atlantic Potatoes in Storage, Lennard Farm, 1987. Funding _______MPIC Bisulfite Alternatives for Fresh, Peeled Potatoes J.N. Cash, C.R. Santerre, and T.F. Leach Michigan State University For many years, bi sulfites have been used to reduce enzymatic browning and extend the shelf life of many processed food products. However, bi sulfites have recently been implicated as harmful compounds for certain individuals with steroid-dependent asthma. Because of this, current and pending legislation is attempting to protect sensitive individuals by restricting the use of sulfiting agents and requiring warning labels on treated foods. Legislation may soon prevent commercial potato processors from treating whole, peeled and refrigerated potatoes with bisulfites. This action would seriously affect processors who depend on these compounds for control of product quality. Ascorbic acid is an acceptable reducing agent for the prevention of enzymatic browning in fruits and vegetables although it does not exert the same kind of long term control as the bisulfites. Recently, researchers have substituted L-ascorbic acid with the less expensive isomer, D-araboascorbic acid (erythorbic acid), in the commercial processing of frozen apple slices. Research has also shown that combinations of ascorbic, citric and sorbic acid can be used in conjunction with oxygen impermeable packaging to prolong shelf life of horticultural products. The objectives of this study were to identify alternatives to bisulfite treatment which a) maintain product quality; and b) can be implemented with existing commercial processing equipment. Whole, abrasion-peeled Russet Burbank potatoes were collected for three trials from a commercial processing line at Pellerito Foods, Inc. Potatoes were treated as follows: Treatment I: Dipped in water for 2 min., drained packaged in water and metal clipped in Cryovac B540 plastic bags. Treatment II: Dipped in water for 2 min., drained, packaged in a solution of 0.2% sorbic acid (potassium salt) + 0.2% citric acid (+ 0.25% calcium chloride was added during Trial 2 & 3 only) and sealed in plastic bags. Treatment III: Dipped in a solution of 3% araboascorbic acid (erythorbic acid) + 2% sodium chloride + 0.25% sodium acid pyrophosphate (Na2H2P2O7) for 2 min., drained, packaged in 0.2% sorbic acid (potassium salt) + 0.2% citric acid (+ 0.25% calcium chloride in Trial 2 & 3 only) and metal clipped in plastic bags. Treatment IV: Dipped in a 2000 ppm bisulfite solution (sodium metabisulfite) for 1.5 min., drained and metal clipped in plastic bags. Potatoes were transported to Michigan State University and placed in cold storage (39°F; 3.8°C) for evaluation of color and microbial load. Color was measured using the Hunter Color Difference Meter (Model D25-2) standardized with a white tile (LL=92.3; aL= -1.2; bL=0.5). Reflectance measurements were made on slices taken from the surface of two potatoes from each treatment. Microbial analyses were done using a plate count method. Prepared plates were held at 86°F (30°C) for 24 hours to check for contamination and then inoculated with samples taken from whole peeled potatoes. These swab samples were spread on the surface of the plates, which were incubated at 86°C (30°C) for 48 hours, after which counts were determined using Quebec Colony Counter. Texture analyses were done using a Food Technology Co., TR-5 Texture Recorder. Weighed equatorial slices from peeled potatoes (1.3 cm thickness) were sheared horizontally in a 10 blade shear-extrusion attachment. Sensory evaluations were conducted using a triangle test taste panel. Russet Burbank potatoes were removed from cold storage (45°F); 7.2°C), abrasion-peeled and dipped in; (1) water for 2 min., or (2) 3% erythorbic acid + 2% sodium chloride + 0.25% sodium acid pyrophosphate for 2 min., drained, and held in 0.2% sorbic acid (potassium salt) + 0.25% citric acid for 10 days. Potatoes were diced and placed in approximately 5 L boiling water in a steam heated kettle and cooked for 15 min, drained, and mashed. Sensory evaluations were performed in the Michigan State University, Food Science, Sensory Evaluation Facility. Warm (80°F; 26.6°C) samples (approx. 100 g) were presented to twenty-seven untrained, college-aged men and women panelists in three small dishes identified by three random digit codes. Panelists were requested to choose the odd sample based on flavor and texture, and then requested to give consents. Panelists were also requested to note if the flavor and texture differences detected were objectionable. No information was provided to panelists regarding potato treatments. The data was statistically analyzed using standard statistical methods and statistical tables which were developed for the sensory tests performed. The color of non-sulfited potatoes was acceptable during the 18 day storage interval for trials 1 & 2 (Table 1 & 2). Potatoes packaged in solutions maintained lightness and were comparable to sulfited potatoes. Potatoes dipped in the erythorbic acid mixture (Treatment III) appeared to be lighter than sulfited potatoes which acquired a yellow tint. Potatoes from all treatments in trial 3, were subjectively determined to have acceptable color after 18 days of storage. Earlier attempts to control enzymatic browning by dipping potatoes in an erythorbic acid mixture and packing without solution in oxygen-barrier bags following an air evacuation and flush with carbon dioxide or nitrogen were unsuccessful. This may have been caused by a low vacuum or by a poor plastic bag seal. Regardless, incorporation of a packaging system in a commercial facility would be expensive and a significant expense would be added to processed products due to the cost of oxygen-barrier bags. Also, the modified atmosphere package may provide an acceptable growth environment for anaerobic microbial pathogens. Results from this study, indicated that a significant improvement in color was achieved when potatoes were packaged in solution without oxygen-barrier bags being used. During the preparation of potatoes for sensory evaluation, it was observed that potatoes dipped in the erythorbic and citric acid mixtures prior to cooking remained very light, whereas, the potatoes dipped in water turned grey. The grey metallic tint is due to an "after-cooking" darkening which requires iron cations. For the antioxidant treated potatoes, the iron is chelated by sodium acid pyrophosphate and citric acid and the darkening reaction is inhibited. In addition, the antioxidant solutions reduce the enzymatic browning reactions which occur during the initial warming of the potatoes. The microbial load for potatoes packaged in the citric acid mixture (Treatments II & III) were generally lower at 6 days of storage than water packed or bisulfite treated. The elevated microbial load for Treatment I indicates that spoilage renders the product unacceptable long before the color changes. A strong aroma was observed due to spoilage for all the Treatment I samples by 6 days of storage. The sulfited potatoes (Treatment IV) did not have a strong spoilage aroma until 9 days of storage during the 3 trials. Commercial processors expect sulfited potatoes to maintain acceptable quality for 5 to 7 days prior to further processing. The lower microbial loads for Treatments II & III compared to Treatments I & IV, appear to be due to the acidification and microbial static properties of citric acid and sorbic acid, respectively. Incorporation of further additives may further extend the shelf life of refrigerated potatoes. Sensory analysis of mashed potatoes indicated that only 8 out of 27 panelists were able to correctly identify the odd sample. Statistically, this means that no apparent differences (p=0.05) for texture and flavor were detected between potatoes dipped in water and potatoes dipped in erythorbic acid and citric acid mixtures. Only one panelist who correctly selected the odd sample noted an objectionable flavor while one other panelist noted an objectionable texture. In this work, potatoes were packaged in 30 pound plastic pails. The citric/sorbic acid solution needed to fill the pail added 10-15 pounds to the shipping weight. This is a major consideration in light of shipping and handling charges. However, it is felt that the amount of solution can be drastically reduced without increasing enzymatic browning. Further work is needed to determine the minimum amount of packing solution required. The alternatives to bisulfite suggested here have several advantages. First there is greater consumer perception of safety for potatoes treated with the erythorbic acid and citric acid mixtures as compared to sulfiting agents. Second, the procedure for treating potatoes with erythorbic acid dip permits the reuse of the solution. It is likely that this solution will need to be recharged with erythorbic acid during the course of a processing day because oxidation of erythorbic acid during processing of potatoes reduces the effectiveness of the antioxidant to 'scavange oxygen' and reduce the o-quinone product of enzymatic browning. Third, the proposed system increases the storage life of potatoes by several days. The storage life of potatoes from Treatment II & III was between 6 and 9 days based on microbial spoilage. Fourth, this process can be implemented with existing equipment and processing procedure. Packaging systems preently in use would require minimal modifications for packing potatoes in solution. Table 1. Mean Hunter Color Measurements (L L- value a) for Trial 1. Storage Time (Days; n=3) Storage Time (Days; n=3) Treatment Day 3 Storage Time (Days; n=3) Day 6 Day 9 Storage Time (Days; n=3)Day 12 Storage Time (Days; n=3)Day 18 I b II c III d IV e 62. 3 66.4 65.0 64.1 65.5 68.5 67.5 66.4 62.4 67.0 67.0 62.9 65.7 68.9 66.2 65.1 66.9 69.0 68.8 66.2 a Hunter L L-values range from 0=black to 100=white b Potatoes dipped in H2O and packaged in H2O c Potatoes dipped in H2O and packaged in citric acid and sorbic acid. d Potatoes dipped in erythorbic acid, sodium acid pyrophosphate and sodium chloride, then packaged in citric acid and sorbic acid. e Potatoes dipped in bisulfite, drained and packaged. Table 2. Mean Hunter Color Measurements (L L-value a) for Trial 2. Treatment Storage Time (Days; n=3)Day 3 Day 6 Day 9 Storage Time (Days; n=3)Day 12 Storage Time (Days; n=3)Day 18 Storage Time (Days; n=3) Storage Time (Days; n=3) I b II c III d IV e 61.1 65.2 66.2 64.5 60.7 65.0 65.1 64.3 59.2 63.8 63.3 64.3 60.1 64.0 63.5 62.4 62.8 65.8 64.6 62.9 a Hunter L L-values range from 0=black to 100=white. b Potatoes dipped in H2O and packaged in H2O. c Potatoes dipped in H2O and packaged in citric acid and sorbic acid and calcium chloride. d Potatoes dipped in erythorbic acid, sodium acid pyrophosphate and sodium chloride, then packaged in citric acid and sorbic acid. e Potatoes dipped in bisulfite, drained and packaged. Table 3. Microbiological Load (CFU a/cm2) for Trials 1 & 2. Treatment Storage Time (Trial 1)Day 6 Storage Time (Trial 1) Day 12 Storage Time (Trial 2)Day 6 Storage Time (Trial 2) Day 12 I b II c III d IV e 1.4 x 10 5 3.4 x 10 5 3.4 x 10 5 <10 2 <10 2 4.5 x 10 3 <10 2 3.7 x 10 3 9.2 x 10 6 <10 2 <10 2 4.1 x 10 4 10 6 10 6 10 6 10 6 a CFU - Colony Forming Units. b Potatoes dipped in H2O and packaged in H2O c Potatoes dipped in H2O and packaged in citric acid and sorbic acid and calcium chloride. d Potatoes dipped in erythorbic acid, sodium acid pyrophosphate and sodium chloride, then packaged in citric acid and sorbic acid. e Potatoes dipped in bisulfite, drained and packaged. Table 4. Microbiological Load (CFU a/cm2) for Trial 3. Storage Storage Time (Days; n=3) Storage Time Treatment Time (Days; n=3)Day 3 Day 6 (Days; n=3) Day 9 Storage Time (Days; n=3)Day 12 I b II c III d IV e 6.6 x 10 4 2.7 x 10 5 > 10 6 < 10 2 < 10 2 < 10 3 < 10 3 3.8 x 10 5 5.3 x 10 3 3.8 x 10 3 > 10 6 > 10 6 > 10 6 > 10 6 > 10 6 > 10 6 a CFU - Colony Forming Units. b Potatoes dipped in H2O and packaged in H2O. c Potatoes dipped in H2O and packaged in citric acid and sorbic acid and calcium chloride. d Potatoes dipped in erythorbic acid, sodium acid pyrophosphate and sodium chloride, then packaged in citric acid and sorbic acid. e Potatoes dipped in bisulfite, drained and packaged. POTATO STORAGE RESEARCH — PHASE C (THIRD YEAR) Funding Federal Grant INVESTIGATORS Roger Brook And Todd Forbush OBJECTIVE The general goal of this project is to develop and validate an improved MSU Simulated Storage system in which the environmental conditions can be controlled, monitored, and replicated to study potatoes over an extended storage season. Specific objectives of this year’s research include: • to expand the instrumentation of the MSU Simulated Storage to include monitoring of carbon dioxide and oxygen levels at several points in the storage, • to continue monitoring of the MSU Simulated Storages for environmental effects on potato quality at several airflow levels, and to compare this data with the results of related ongoing research on potato quality, • to evaluate existing simulation models of potato storage as compared to the current MSU Simulated Storages for their usefulness in evaluating storage options and management practices. METHODS/PROCEDURES Storage System Three Simulated Storages were placed within a commercial potato storage facility at Sandyland Fanns Inc. (Howard City MI). The storage system has been described in more detail in previous re ports and in technical research papers.1 The bins were reduced in size to result in 64 ft2 cross- sectional area. This gave a storage capacity of roughly 360 cwt per bin. A floor plan of the facility is shown in Figure 1. Ventilation System Each Simulated Storage is equipped with a ventilation system which is independent of the other storages. Bins #1 and #2 are equipped with ventilation systems designed at 1.5 and 3.0 cfm/cwt, respectively. Bin #3 is equipped with a variable speed fan that is capable of delivering up to 3 cfm/cwt. The intake air is drawn from the attic of the commercial building. It is distributed to the three Simulated Storages through a common "fresh air manifold" so that these bins have access to the same intake air. In previous years, the ventilation systems of the Simulated Storages exhausted into the commercial bin via pressure louvers. The ventilation system was modified by the addition of an exhaust air duct. This duct reduced the effect of the pressure in the commercial bin on the exhausting of fresh air. Additional modifications to the exhaust system were made on November 10, 1987, which involved the addition of a small exhaust fan to each bin. The fans were controlled by the signal for fresh air from the computer, and were run any time the bins required fresh air. Control System The ventilation system was controlled using a 1056 FANCOM environmental control computer developed in The Netherlands by FANCOM Computers Inc. (commercially available at Techmark Inc., Lansing MI).2 The fans ran to correct pile temperature differentials and any time fresh air was required. In bins #1 and #2 with single speed fans, the fan came on full speed if any air movement was requested by die computer. In bin #3 with the variable speed fan, the computer determined the volume of air required to resolve the temperature problems. Data Collection Changes to the data collection system included the following items: • expanding the gas sampling to include the sensing of four gas levels within each bin; • ability to determine the amount of oxygen and the amount of carbon dioxide, present within the pile during the storage season; • additional relative humidity sensors (aspirated wet bulb/dry bulb psychrometer) to determine the humidity of the air above the pile; • increase the resolution of the in-pile temperature sensors from 0.5 C to 0.1 C; • change room temperature control to read from the relative humidity sensor above the pile (this change eliminated the problem of 3 quick response experienced when controlling via the plenum temperature); • install air volume sensors in the fresh air and recirculation air louvers to determine the amount of air moving, and the source of the air. Potato Samples Sample bags (25 lb.) were placed within each of the Simulated Storages at levels of 4 ft., 8 ft., and 12 ft. from the floor of the storage (4 bags per level). Upon removal from storage, these samples were evaluated for weight loss and for changes in sugar content during storage. Each bin was also evaluated by Frito-Lay (Allen Parie, MI) at the time of removal for its value to the potato chipping industry. RESULTS AND DISCUSSION scheme was to lower the desired temperature 1 °F per week until the potatoes reached a temperature of 50°F, or until marketing them. The relative humidity of the storage was maintained as close to 92% RH as possible with a small humidifier in the main air plenum of each bin. Condensation was noted on the surface of Bin #1 on December 29,1987. The humidifier was then turned off, but the fan was left to the control of the computer until January 4,1988, when the fan was put on continuous circulation. The bin was marketed on January 27,1988. Bin #2 was marketed on February 16,1988. Bin #3 was marketed on February 23,1988. Management of Storages The potatoes for the Simulated Storages were harvested on October 5,1987. Potato variability into storage was reduced by filling the three Simulated Storages from one field in one day. The pulp temperature of the potatoes was 50.5 °F. The potato piles were allowed to rise in temperature without ventilation to 60 °F. This took between 5 and 8 days; bins #1 and #2 took five days, and bin #3 took 8 days. When the potatoes had obtained the 60 °F temperature level, the ventilation system was programmed to maintain this temperature for "pre-conditioning". The potatoes were treated with CIPC sprout inhibitor on November 13,1987, to reduce the possibility of sprouting in long term storage. The pile temperature was held at 60°F until November 16,1987. Then, the management TABLE 1: Fan time operation analysis for the Simulated Storages, 1987-1988 storage season. Bin Number Time, days Airflow, cfm/cwt Fan Time Fan Operation An analysis of data from the storage season yielded the data in Table 1 for air volume and reason for fan operation. The length of season varied for each bin because of staggered unloading. The data shows that the fan in the high airflow volume bin (bin #2) ran nearly the same amount of time as the low airflow volume bin (bin #1). This resulted in just over twice the total volume of air, since the specific volume of air flow was twice as large. The average operation period for the maintenance of uniform pile temperature ranged from 6.4 hr. for bin #2 to 20 hr. for bin #1 (around December 29, 1987). The increased operation time in bin #1 was due to increased fan operation to counteract the 2 134 3.0 3 142 1.4X 2352 69 1 114 1.5 1077 39 1381 43 46 68 2.4 2.3XX 85 15 92 146 6.4 5.4 43 57 126 238 12.0 3.5 64 36 hours % Fan Time Number of Cycles pile temperature diff fresh air required Number of Cycles Cycle Time, hr Cycle Reason, % pile temperature diff fresh air required Cycle Time, hr pile temperature diff fresh air required Cycle Reason, % x Variable airflow, value is average airflow for season xx Season until Dec. 29 only natural convection which occurred within the pile during extended periods without ventilation. If this period of operation for bin #1 is taken out of the season, the average period for maintenance was 2.3 hr. per cycle. The high cycle time for correction of pile temperature for the high airflow bin (5.4 hr. forbin #2) may have resulted from a temperature fluctuation within the pile from the "blast" of cool air used to cool the pile. Such a "blast" would then require additional ventilation to complete the required temperature correction. The fans cycled 68,146, and 238 times for temperature correction throughout the season. On the average, the fans cycled 1,1.8 and 2.6 times per day, with periods without ventilation ranging from a few hours to nearly a week. The reason for the increased cycling in bin #3 (variable airflow) may have been the low airflow that was used. On the average the airflow was 1.4 cfm/cwt, with volumes as high as 3 cfm/cwt. Long periods of low volume air (.0 cfm/cwt) were recorded for pile temperature maintenance ventilation. This would suggest that the influences may need to be changed to increase the volume of airflow for different problems. In bin #2, the high airflow rate may have resulted in the high frequency of fan cycling. High airflow rates cause sudden changes, which may over compensate for small troubles. Environment Control Table 2 presents the data for temperature and relative humidity control in the Simulated Storages. The data show an adequate control of pile temperature in all three bins, as compared to the criteria of an allowed temperature differential within the pile of 1.1°F, and allowed control range on average temperature of 0.5°F. The average temperatures for bins #1, #2 and #3 are shown in Figure 2. Representative temperature and airflow data for bin #2 are shown in Figure 3. Representative carbon dioxide, oxygen and airflow data for bin #3 are shown in Figure 4. The data also show good control of the relative humidity within less than 5% (Bins #1 and #3) and 7.5% (Bin #2) of the desired value of 92%, as measured by an aspirated psychrometer. Potato Quality Table 3 presents the data generated by Frito-Lay on the usefulness of the potatoes from the Simulated Storages for sale as chipping potatoes, plus the weight loss observed for the sample bags within the pile. Note that the higher solids in bin #3 correlated roughly with the increased weight loss observed. Table 4 presents the results of the sugar analysis before harvest, and for the sample bags within the pile. The percent glucose readings before harvest suggest that some reducing sugars must be burned off in storage before acceptable chip colors are obtained. Chip color was initially TABLE 2: Temperature and relative humidity control for the simulated storage bins during the 1987- 1988 storage season. Bin Difference between highest and lowest measured pile temperatures #2 #3 #1 Average difference, °F 1.2 Lowest difference, °F Difference between highest and lowest measured pile temperatures 0.0 Difference between highest and lowest measured pile temperatures Highest difference, °F 2.9 1.1 0.0 1.8 Difference between desired and measured pile temperature 0.4 0.0 1.3 Difference between desired and measured relative humidity 3.6 0.0 14.0 Average difference, °F Lowest difference, °F Difference between desired and measured pile temperature Highest difference, °F Difference between desired and measured pile temperature Average difference, % Difference between desired and measured relative humidity Lowest difference, % Highest difference, % Difference between desired and measured relative humidity 1.5 0.0 3.5 0.3 0.0 1.8 6.4 0.0 14.0 0.4 0.0 2.5 3.3 0.0 11.0 unacceptable. However, as time progressed from the October 5 loading data into early November, the chip color problem cleared up. This would suggest that potato respiration cleared the pool of glucose (reducing sugar). • Fixed lnlet Conditions of: • 60°F, 65 % RH, with 0.75 cfm/cwt ventilation • 60°F, 65 % RH, with 1.5 cfm/cwt ventilation • 60°F, 65 % RH, with 3.0 cfm/cwt ventilation • 60°F, 80 % RH, with 0.75 cfm/cwt ventilation • 60°F, 80 % RH, with 1.5 cfm/cwt ventilation • 60°F, 80 % RH, with 3.0 cfm/cwt ventilation COMPUTER SIMULATION Methods and Procedures A computer simulation model3 which predicts heat generation and condensation due to tuber surface temperature differences, was modified and used for this study. The temperature difference problem studied was that of having 6.5 ft. of 70°F potatoes in the lower portion of the pile, and 6.5 ft of 50°F potatoes in the upper half of the pile. This condition could occur when a bin has been partially filled one day, and then opened on the next day to continue filling. The problem with this condition is the possibility of condensation forming on the cooler potatoes due to the warm, moist air rising from the warmer potatoes. The resulting condensation could cause spoilage of potatoes along the temperature interface. The ventilation management schemes investigated were as follows: • No Ventilation • Complete Recirculation with 1.5 cfm/cwt ventilation The tubers were subjected to specific inlet conditions. The temperature value was chosen as the mean temperature of the two lots of potatoes, and the humidity and ventilation rate were varied. These conditions were chosen to agree with the typical fall weather conditions in Michigan. Results and Discussion Weight Loss The simulation results suggests that the weight loss percentage increases with the ventilation rate. However this is a function of the water on the tuber surface. The amount of water removed from within the tuber is negligible until the surface moisture is removed. Therefore, the longer the tubers are covered with moisture, the lower the weight loss will be. The lowest predicted weight loss was with the recirculation run. However, this type of ventilation did not remove moisture satisfactorily, as explained below. The weight loss values or the 0.75 cfm/cwt, 65% RH and the 1.5 cfm/cwt, 80% RH were predicted to be similar. TABLE 3: Frito-Lay cook tests and weight loss for samples from simulated storages, 1987-1988 storage season. Pile Level Bin #1 12’ 4’ 8’ 63 16.5 0 5.3 63 15.9 0 6.7 62 16.2 0 4.4 Color Bin #1 % Solids Bin #1 Appearance Bin #1 % Weight Loss Bin #2 Bin #3 Color Bin #2 % Solids Bin #2 Appearance Bin #2 % Weight Loss Color Bin #3 % Solids Bin #3 Appearance Bin #3 % Weight Loss 63 17.4 3 7.8 63 18.8 2 9.2 63 16.5 0 7.9 60 18.0 0 10.4 62 17.8 1 8.0 63 17.4 0 8.2 Condensation Running the ventilation system in a complete recirculation mode slowly moved the condensation layer through the top of the pile, and placed this moisture into the lower regions of the pile. Thus, condensation at all levels of the pile was predicted. Once the air that is present in a tightly sealed building is at the saturation point, additional water cannot be absorbed by the air. This pattern is expected to continue until some moisture is removed from the structure, or the air is heated to a sufficient level to absorb this moisture. This may occur by heat generation within the pile. However these high temperatures would detrimental to the tuber in terms of soft rot infestation. From this simulation, the tubers were subjected to specific inlet conditions. The temperature value was chosen as the mean temperature of the two lots of potatoes, and the humidity and ventilation rate were varied. As the ventilation rate was increased, the time required to remove surface condensation decreased (see Table 5). Increasing the ventilation from 0.75 cfm/cwt to 1.5 cfm/cwt decreased the time to remove the surface condensation by 44%. The increase from 1.5 to 3.0 cfm/cwt decreased the time for removal of condensation by 56%. The effect of decreasing inlet relative humidity was to decrease the time required to remove the surface moisture. At the 1.5 cfm/cwt a decrease of the inlet relative humidity from 80% to 65 % decreased the time required to remove surface condensation by 56%. Temperature The simulation results suggest that the time required to obtain a uniform temperature gradient (+_2°O within the potato pile is 20 to 30 hours for both the 1.5 and 3.0 cfm/cwt ventilation rates at both relative humidity levels (see Table 5). The uniform pile temperature was not obtained within the same limits with the low ventilation rate, or recirculation simulations. TABLE 4: Sugar content analysis for samples from Simulated Storages, 1987-1988 storage season. Date or location Pre-harvest samples Glucose Sucrose Sample No. 1 2 3 4 5* 6 7 8 56 B65 52 59 B60 B73 57 B77 B79 0.04 0.05 0.05 0.05 0.04 0.05 0.05 0.06 0.010 0.006 0.016 0.010 0.006 0.006 0.022 0.027 0.027 Bin#l 8-15-87 Pre-harvest samples 8-25-87 Pre-harvest samples 8-29-87 Pre-harvest samples 9-08-87 Pre-harvest samples 9-16-87 Pre-harvest samples 9-18-87 10-02-87 Pre-harvest samples 10-07-87 Pre-harvest samples 4’ 8’ Bin#l 12’_______________ _____ Bin#l Bin #2 4’ Bin #2 8’ Bin #2 12'_______________ 4’ Bin #3 8’ Bin #3 12’ Bin #3 * Vine kill Total Sugars 0.56 0.27 0.20 0.50 0.44 0.44 0.52 0.85 0.09 0.06 0.10 0.16 0.10 0.10 0.58 0.63 0.43 0.52 0.22 0.15 0.45 0.40 0.39 0.47 0.79 0.08 0.06 0.08 0.15 0.10 0.09 0.56 0.61 0.41 • If cool potatoes are placed in contact with warm potatoes, run the fans at 1.5 cfm/cwt. Set the inlet air at the average of the pulp temperatures of the two lots and 80% RH. • Observe the top of the pile, when condensation contact with warm potatoes when filling a potato storage bin. Management Suggestions The following management suggestions are made with the results of the above simulations in mind: • Avoid the condition of placing cool potatoes in The temperature change within any single layer of the pile over a period of time was also calculated (see Table 5). A sudden decrease in temperature may cause the potato respiration to decrease, therefore causing an imbalance of the sugar content in the potato. If this imbalance continues to exist into the storage season, the potatoes may be unsuitable for the process industry. The largest temperature decrease took place within the 1.5 ft. depth of the recirculation simulation, where the potato temperature decreased 16.2°F (70 °F to 53.8°F) in 10 hours. This type of temperature stress could be expected to reduce respiration rate, which may result in reducing sugar build-up within the tuber. The temperature decrease was not as sever in the 80 % RH simulations with ventilation temperature set at 60°F. This was due to a reduction in evaporative surface cooling in the tubers from a lower vapor pressure differential. TABLE 5: Time requirements and temperature change information for different siumlation con- ditions. empty table cell (a water Him on the lower side of the potato tubers) appears, continue ventilation until it is removed, then return to normal management practices. • Market these potatoes as soon as possible. Time to Remove Condensation Time to Uniform Temperature Maximum Temperature Change Recirculation 65%, 0.75 cfm/cwt 80%, 0.75 cfm/cwt 65%, 1.5 cfm/cwt 80%, 1.5 cfm/cwt 65%, 3.0 cfm/cwt 80%, 3.0 cfm/cwt 280 100 160 40 90 - 20 40 100 300 110 30 30 30 20 16.4(70-53.6) 10.8(70-59.2) 10.6(70-59.4) 11.7(70-58.3) 10.8(70-59.2) 12.4(70-57.6) 11.3(70-58.7) 1 Trade names are used in the paper solely to provide specific information. Mention of a trade name does not constitute a warranty of the product by Michigan State University or the United States Department of Agriculture or an endorsement of the product to the exclusion of other products not mentioned. 2 For more details on the control system, see the following: Forbush, T.D., Cargill, B.F. and Brook, R.C. Sensing, monitoring and controlling potato storage environments - a progress report. Tech. Paper 87-4067. ASAE, St. Joseph, MI 3 For more details on the computer simulation model, see the following: Lerew, L. E., 1978. Development of a temperature- weight loss model for bulk stored potatoes. Unpubl. Ph.D. thesis, Michigan State Univ., E. Lansing MI F I G U R E 1 : F l o o r p l a n o f t h e S i m u l a t e d S t o r a g e r e s e a r c h f a c i l i t y ( s c a l e 1 : 1 0 ) F I G U R E 2 ; A v e r a g e p o t a t o p i l e t e m p e r a t u r e f o r t h e 1 9 8 7 - 1 9 8 8 s t o r a g e s e a s o n . s e a s o n . F I G U R E 3 : R e p r e s e n t a t i v e t e m p e r a t u r e a n d a i r f l o w d a t a f o r b i n # 2 f o r t h e 1 9 8 7 - 1 9 8 8 s t o r a g e 1 9 8 8 s t o r a g e s e a s o n . F I G U R E 4 : R e p r e s e n t a t i v e o x y g e n , c a r b o n d i o x i d e a n d a i r f l o w d a t a o f o r b i n # 2 f o r t h e 1 9 8 7 - MICHIGAN POTATO INDUSTRY COMMISSION 13109 Schavey Road, Suite 7 DeWitt, Michigan 48820 Bulk Rate U.S. Postage PAID Lansing, Mich. Permit No. 979