THE VFrlCT GE CALCIUM-POTASSIUM RATIOS ON 'E‘HE INCEDENCE OF POTATO SCAB “fl-€12,535 F83}! "fl-5E DEGREE 0? P213. MICHEGAN STATE COLLEGE PHIL}? BEAUMONT '1“U'RNER 3.9355 THEQS V WHIIHHIIWIWWIHNIIWHIIHIIWVIHI 3 1293 10$ ,7170 82 LIBRARY Michigan State University This is to certify that the thesis entitled The Effect of Calcium—Potassium Ratios on the Incidence of Potato Scab presented by Philip B . Turner has been accepted towards fulfillment of the requirements for D co t o r‘s_ degree in Phi 1 o_s oghy (RLM Major professor 0—169 MSU LIBRARIES Jansen... RETURNING MATERIALS: Place in book drop to remove this checkout from your record. FINES will be charged if book is returned after the date stamped below. W3: THE EFFECT OF CALCIUM-POTASSIUM RATIOS ON THE INCIDENCE OF POTATO SCAB By Philip Beaumont Turner A THESIS Suhmitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHX Department of Soil Science 1955 Philip Beaumont Turner 1 Three field trials were carried out to ascertain the effect of calciumppotassium ratios upon the scabbiness and yield of potato tubers and the uptake of calcium and potassium by the plants. One field trial was conducted to determine whether application of zinc would reduce scabbing of potatoes. A greenhouse experiment was performed to test the effects of lime placement on yield and scabbing of tubers. The field soil was fiillsdale sandy loam having originally a pH of 6.2 and an exchangeable calcium and potassium content of 3.50 and 0.80 milliequivalents per 100 grams, respectively. Katahdin, Chippewa, and Sebago potato varieties were grown. For the greenhouse study Emmet fine sandy loam with a pH of 6.5 and five percent organic matter was chosen. Chippewa potatoes were used in this eXperiment. In order to obtain descending calcium-potassium ratios, potash was supplied at rates of none to hSO pounds per acre in 50 pound increments. Zinc at rates of none, 12.5, and 25 pounds per acre was superimposed on a potash treatment series. Lime was applied in bands at the nine inch depth and was mixed-throughout the top nine inches of soil which had pre- viously been leached with sulfuric acid to create two pH levels. At intervals throughout the growing season leaf samples were taken from the field plots and analyzed for total cal- cium and potassium, while soil samples taken were analyzed for exchangeable calcium and potassium. :hilip Beaumont Turner The harvested tubers were sorted into four classifications of scabbiness, weighed, and specific gravity of a represen- tative sample from each plot was determined. In 1951, as the calcium-potassium ratio approached one, there were increased yields and reduced scabbiness on Katahdin potatoes. No general trends resulted from lowered calcium-potassium ratios in 1952. Yields increased with the first three in- creases in exchangeable potassium.content of the soil. The picture presented by that year's data did not confirm the initial trends of the 1951 data. The yields, percent scab, and scab index showed that Chippewa and Segabo potatoes did not respond favorably to the addition of potash in 1953. Katahdins showed trends of lowered scab index and increased yields shmilar to those of 1951 but of less magnitude. Zinc did not decrease the percent of scabby tubers, the scab index, or percent heavy scab. No increase in yield re- sulted from the addition of zinc. The potash treatments did significantly increase yields. The greenhouse data showed that lime placed at the nine inch depth did not reduce scabbing nor increase yield at either pH. Chippewas from Emmet fine sandy loam.at pH 5.6 with 1000 pounds per acre of lime mixed throughout the top nine inches of soil were the most scab-free and largest of all the harvested tubers. rni lip Beaumont Turner 3 The exchangeable potassium in the soil and the total potassium in the potato leaves increased in a manner con- sistent with the increments of potash applied. The rela- tionship between the calcium-potassium ratios in leaf and soil smles was evidenced by their similar curves. The addition of as much as 1450 pounds of potash per acre had no adverse effect on the cooking quality of Katahdin potatoes as measured by the specific gravity. ACKNOWLEDGEMENTS The author wishes to express his appreciation to In» James Tyson for continuous advice and assistance :hiplanning and carrying out his program.of graduate research. Helpful suggestions and guidance were willingly given tn'Drs. R. L. Cook, J. F. Davis, R. E. Lucas, K. Lawton, and'all other members of the soil science faculty. Special appreciation is due Dr. Cook for the photographs he made. The writer is grateful for the help of his wife as a laboratory technician and.persona1 secretary. VITA Philip Beaumont Turner candidate for the degree of Doctor of PhilosOphy Finaliexamination, May 16, 1955. 10:00 A.M., Room 210, Agriculture Hall Thesis: The Effect-of CalciumpPotassium Ratios on the Incidence of Potato Scab Outline of Studies: Major subject: Soil Science Minor subjects: Chemistry, Business Administration Biographical Items : Born, January 30, 1922, Mapleton, Maine Undergraduate studies, University of Maine, l9h0-19h2 anflal9h6-19h8, Degree of 8.8. in Biochemistry, June, 19 Graduate studies, University of Massachusetts, l9h8-l950, M.S. Degree in Agronomy, June, 1950; Michigan State College, 1950-1955 Experience : Graduate Research Fellow, University of Massachusetts, 19h8-19h9 Graduate Teaching Fellow, University of Massachusetts, 19u9-1950 Vocational Agriculture Instructor, Eaton Rapids Veterans Institute, Eaton Rapids, Michigan, 1951-1953 Plant Manager, Farm.Bureau Services, Inc. Plant Food Division, Kalamazoo, Michigan, 1953-1955 Head, Department of Quality Control and Research, Plant Food Division, Farm Bureau Services, Inc., Lansing, Michigan, 1955 Metuber of the Society of the Sigma Xi, and Soil Science Society of America TABLE INTRODUCTION . . . . . . REVIEW 0? LITERATURE . . . ExmnflMENTAL METHODS . . . Field . . . . . . . . Greenhouse . . . . . . EXPERIMENTAL RESULTS . . . Field . . . . . . . . Greenhouse . . . . . . SUMMARY AND CONCLUSIONS . . LITERATURE CITED . . . . . OF CONTENTS Page TABLE 1. 2. 3. 9. 10. 11. 12. 13. LIST OF TABLES 8011 data 0 O O O O O O O O O O O O O O O O O O O 0 Lime placement . . . . . . Effect of calcium-potassium yield, 1951 . . . . . . . Effect of calcium-potassium and yield, 1952 . . . . . Effect of calcium-potassium and yield, Katahdins, 1953 Effect of calciumppotassium and yield, Chippewas, 1953 Effect of calcium-potassium and yield, Sebagos, 1953 . ratioson potato scab and ratios on potato scab ratios on potato scab O O O O O O O O O O 0 ratios on potato scab ratios on potato scab Rainfall data for the college farm, East Lansing, M10hlgan......... O O O O O O O O O O 0 Effect of increasing amounts of potash on the exchangeable calcium and potassium extracted from Hillsdale sandy loam . . . Effect of increasing amounts of potash on the composition of potato leaves grown on Hillsdale sandy loam . . . . . . . . Exchangeable potassium in Hillsadle sandy loam samples taken during 1951, Effect of various levels of potash on the specific 1952, and 1953 e e e grav1ty Of Katahdin pOtatoes e e e e e e e e e e Effect of zinc applied to Hillsdale sandy loam previously treated with increasing amounts of potash on yield and ecabbiness of potatoes . . . pH values resulting from leaching Emmet fine sandy loam with two different amounts of 6 Normal sulfuric 301d e e e e e e Page 6 1h 16 18 20 21 22 23 29 30 32 35 36 38 LIST OF TABLES (Cont.) Page 15. pH values of Emmet fine sandy loam throughout the growing season . . . . . . . . . . . . . . . . . . 39 16. Scabbiness observed on potatoes from greenhouse lime placement experiment . . . . . . . . . . . . hO LIST OF FIGURES FIGURE 1. 2. 3. Effect of calciumppotassium ratios on scabbiness 0f Katahdin potatoes as measured by scab index . . Effect of calcium-potassium ratios on scabbiness 0f Katahdin, Chippewa, and Sebago potatoes as measured by scab index . . . . . . . . . . . . . . . . . . Effect of calciumppotassium ratios on scabbiness of Katahdin potatoes as measured by percent scab . . Effect of calcium-potassium ratios on scabbiness of Katahdin, Chippewa, and Sebago potatoes as measured by percent scab . . . . . . . . . . . . . A comparison of the milliequivalents of exchangeable potassium in the soil and the milliequivalents of potassium in the potato leaves . . . . . . . . . . A cmmparison of the calcium ratios in the soil to the calcium-potassium ratios in the potato leaves. PAGE 25 26 27 31 33 LIST OF PLATES PLATE Page IA. Potatoes typical of the scab grades used in this Stlldy e e e e e e e e e e e e e e e e e 9 I. Response of Chippewa potatoes in Emmet fine sandy loam with a pH of 5.h after leaching to 1000 pounds of lime per acre placed in a band at a depth or nine inCheS e e e e e e e e e e e 0 1+2 II. Reaponse of Chippewa potatoes in Emmet fine sandy loam with pH of 5.h after leaching to 1000 pounds of lime per acre mixed throughout the top nine inches of soil . . . . . . . . h3 III. Response of Chippewa potatoes in Emmet fine sandy loam with a pH of 5.5 after leaching . uh IV. Response of Chippewa potatoes in Emmet fine sandy loam with a pH of h.8 after leaching to 1000 pounds of lime per acre placed in a band at a depth of nine inches . . . . . . . #5 V. Response of Chippewa potatoes in Emmet fine sandy loam with a pH of h.8 after leaching to 1000 pounds of lime per acre mixed throughout the top nine inches of soil . . . h6 VI. Response of Chippewa potatoes in Emmet fine sandy loam with a pH of h.8 after leaching . h? INTRODUCTION The potato, introduced into Spain during the last half cu’the sixteenth century (16), has had a marked influence on Occidental civilization. Its economic importance was and is considerable in that it furnishes a large portion of the car- tmhydrates consumed in the United States. Losses from.scab have increased in major potato producing areas (25), and re- turns from the crop have been greatly decreased. As a result, all commercial growers are interested in control measures. In 1890 Thaxter (20) described the causitive agent of potato scab and named it 08spora scabies. Gfissow renamed it Actindmyces scabies (8), and it is now classified as Strep- t. Omces scabies as was proposed by Haksman and Henrici (2, 22). From that time numerous investigators have treated the soil ’ and.seed tubers with named and un-named compounds in an effort to conquer the disease. In 19h2 Schroeder and Albrecht (17‘ carried out green- hOuse experiments using artificial soil in which the calcimm- ‘Potassium.ratios were varied. They reported that the incidence of potato scab was decreased by bringing the calcium and Petassium into a 1:1 m.e. ratio. In 1926 Fellows (6) described the relationship between growth inthe potato tuber and potato Scabbiness as follows: 1. Potatoes are susceptible to infection during their growth period. 2. The pathogenic organism.enters the host along the phellogen of the cells of the subepidermal layer by way of the middle lamella which be- comes thickened and darkened. Since it is known that calcium pectate is a component of the saddle lamella (15), it is reasonable to expect, in relating the results of these two works, that an unbalanced exchange- able calciumppotassiumtratio in a potato plant might allow deeper, more extensive, and more frequent invasion of the muddle lamella by Streptomyces.gcabie§, The experiments reported in this paper were conducted to determine which of various calciumppotassium.levels on a field soil in situ would decrease scabbing without adversely affecting yield. Incidental to the main objective were 1. 2. Appraisal of the effect of added exchangeable potassium on the potassium and calcium content of the potato leaves. Evaluation of the effect of varying potassium levels on the specific gravity of the potato tubers. Carrying out a greenhouse test to determine the effect on potato scab of lime concentrations at various depths. Investigations of the effect of zinc on Strep- tomyces scabieg in a field plot. REVIEW OF LITERATURE Previous works by Stone and Chapman (19) in Massachusetts; Wheeler, Tower, Hartwell, and Sargent (22) in Rhode Island; and Mwncie, Wheeler, and Tyson (10) in Michigan, and many others were directed toward reduction of potato scabbiness by swans of some inhibitor to the growth of the causal organisms. Hollenweber (21+) and Wingerberg (23) reported that the etiology was not one but many species of the organism. Hence, the various soil remedies were not universally effective (9). In 1896 Wheeler 23,21 (22) reported that lime and wood ashes increased scab incidence on "exceedingly acid" sandy loam» Cook and Houghland's (h) results showed that fertilizers containing calcium, used over a period of years, increased the prevalence of scabby potatoes in Virginia soils with an cmiginal pH of 5.0. Generally, workers have found more scab in limed soil although Blodget and Cowan (3) found that ex- tremely large amounts of lime applied to a soil with pH thud reduced scab lesions on tubers. Starr (18) found no significant relationship between 8cabbiness and the pH of the soil or its content of soluble salts, lume or available phosphorus or potassium. Neverthe- 1938. in 19h2 in a greenhouse trial Schroeder and Albrecht (17) decreased scabbing by bringing the calcium and potassium °°ntent of the soil into an equivalent balance. 3 The use of heavy elements for control of scab in potatoes has had many varied results. Copper sulfate gave some control haNew Jersey and Michigan but failed in Vermont (9). Mercury compounds have given partial to complete control of scab in long Island, New York, Maine, New Jersey, and foreign countries but have failed in many other places (9). KenKnight (9), in his studies on soil Actinomyces in relation to potato scab, stated, ”Zinc alone and in combination with mercuric chloride as soil treatments decreased scabbing." Nelson and Brady (11), in a 19hh greenhouse trial, showed that subsurface placement of lime in Portsmouth sandy loam increased total yield of potatoes and the amount of scab free tubers. EXPERIMENTAL METHODS Field §g;l. The site of the field trials was the college farm at East Lansing, Michigan. The soil type and some of its chemical properties at the beginning of the study (1951) are shown in Table 1. This soil had not been in cultivation for several years and was covered with a sod of blue grass and weeds indigenous to the area. The soil was easy to till and was well adapted to the raising of potatoes. Field Treatmentgfand Procedures. The soil test showed uhe presence of sufficient exchangeable calcium. Therefore, it was decided to add potash fertilizer at ten rates of appli- cation, the highest calculated to bring about a 1:1 calcium, POtassium ratio. The treatments were 1. 0 pounds of K20 per acre 2. 50 pounds of K20 per acre 3. 100 pounds of K20 per acre h. 150 pounds of H20 per acre 5. 200 pounds of K20 per acre 6. 250 pounds of K20 per acre 7. 300 p0unds of K20 per acre 8. 350 pounds of K20 per acre 5 TABLE 1 SOIL DATA w_ l 2 Total Base Soil Type pH on K3 Ca-3 Na3 Mg” Exchange . Capacitys (pct.) (milliequivalents per 100 grams) Hillsdale _ Sandy Loam 6.2 3 0.80 3.50 0.69 0.26 5.9 1 “1 pH determined by glass electrode on a 1:1 soil-water ratio Organic matter determined by dry combustion method (1) Potassium, calcium, and sodium determined by use of Normal ammonium acetate extraction and flame photometer Magnesium determined by colorimetric method of Drosdoff and hearpass (5) Total base exchange determined as follows: Soak a 25-gram.sample over night in distilled water. Leach with 200 m1. of 0.05 Normal H01. Wash with two 200 ml. portions H20 and 100 ml. of 85-90 percent ethyl alcohol. Dry in a 90° C. oven overnight. Using a 1:1.5 soil-water ratio, determine the pH. Add two grams of solid BaCl (crystals). Determine the pH. Titrate potentiomeérically with standard Ba(0H)2 to pH 8.0 by adding 1 ml. increments of Ba(0H)2 to pH 7.0 and then 0.5 m1. increments to pH 8.0. 9. #00 pounds of K 0 per acre 2 10. hSO pounds of K20 per acre These treatments were replicated three times in a randomized design. The area was divided into two equal fields, designated as fields A and 3;. Each individual plot within these fields nmasured 10.5 by 30 feet and contained three rows of potatoes. There‘were three guard rows on the east and west borders of the entire experimental area. On May S, 1951, half of the potash was broadcast on each plot in fields A and g. The remainder was applied on May 19 after the soil had been plowed and fitted. Katahdin seed was then planted in field A without further fertilization. A blaxmwt application of urea and phosphoric acid was made on June 9. Samples of soil from field A were obtained on July 28, August 5, and November 12, 1951. Leaf samples were taken July 1h, July 2k, and August h. The crop was harvested on oetober h. Tubers from the center 25 feet of the middle row of each individual plot were used in this study. They were graded into four classifications of scabbiness as follows: 1. Clean - no scab _ 2. Light - one or two slight lesions per tuber 3. Medium - several lesions per tuber, none extremely deep h. Heavy - many lesions per tuber, with or without deep scab A.photograph showing potatoes typical of these grades is pre- sented in Plate IA. To correlate yield with scabbing, tubers were weighed according to the above classifications. The specific gravity (nfa representative sample from each plot was ascertained at storage time . The number two size scabby potatoes were saved for the next year's seed. Field B was planted on May 15, 1952 without further application of potash fertilizer. Phosphoric acid and urea were applied on May 30. Soil samples were taken from field B on July 12, and August 28. Leaf samples were taken on July 19, August 2, and August 17. On October 8 the tubers were harvested, sorted, weighed, and specific gravity determinations made as in the Previous year." In 1953 two separate field tests were carried out. Be- fOre planting, potash was added to field A for the purpose of making the exchangeable potassium content of at least three treated plots equal to or greater than the exchangeable cal- clumcontent. The following amounts were used: 1. 50 pounds of K20 per acre 2. 55 pounds of K20 per acre 3. 175 pounds of K20 per acre h. 200 pounds of K20 per acre ..,. kg. m Plate IA. Potatoes typical of the scab grades used in this study 1. 2. 3. h. Clean - no scab Light - one or two slight lesions . per tuber Medium « several lesions per tuber, none extrelely deep Heavy - many lesions per tuber with or without deep scabs 10 5. 2&0 pounds of K20 per acre 6. 250 pounds of K20 per acre 7. 270 pounds of K20 per acre 8. 310 pounds of K20 per acre 9. 350 pounds of K20 per acre 10. 1,000 pounds of K20 per acre This field had been planted to oats, followed by rye which Imd.been plowed down in the spring. On May 19 and 20 field A was planted so that each plot contained one row each of the Katahdin, Chippewa, and Sebago varieties. Zinc was applied to field B so that each of the three replications in the calciumppotassium treatment series re- ceived 0, 12.5, or 25 pounds of zinc per acre. This field "as planted at the same time as field A, but only Katahdin seed was used. Soil samples were taken from field A on July 18, August 28, and November 6 and leaf samples on July 11 and August 8. Harr'vesting from each row and grading were done on October 23. Specific gravity was not determined. No soil or leaf samples were removed from field B. A 25; I'Oot section from the center row of each plot was harvested on oetober 23. Grading and weighing were carried out as in pre- Vious years. Specific gravity was not determined. The methods of reporting scabbiness follow. ll 1. The percent scab was derived by dividing the total yield from each treatment into the total pounds of tubers which had been graded light, medium, and heavy in scabbiness and multiplying the quotient by 100. 2. The percent heavy_ggab refers to the percent of the total yield from each treatment which was classified as heavy in scabbiness. 3. The scab index is a weighted index which was derived for each treatment by multiplying the total pounds of tubers graded light, medium, and heavy by one, two, and three, respectively. These three products were added, and the sum was divided by the total weight of the tubers har- vested from the three replications. Yields resulting from each treatment are reported as 13319 mg; which was.calculated by adding the pounds from each repli- cEtion, dividing this sum by three and multiplying by 10 to I‘emove the decimal point. In order to indicate freedom from scabbiness, the percent Eggjs. No. l was determined by dividing the total yield from each treatment into the pounds of potatoes which had been graded clean and light. To show the correlation between percent U. S. 'NO. l.and yield, yield index U. S. No._; was determined by n“Iltiplying percent U. S. No. l and yield index. 12 Laboratory_Procedure§. Twenty-five grams of air dry seived soil from each sample was leached with 200 cc. of 1 Normal ammonium acetate (12). Exchangeable calcium.and potassium in parts per million were determined on an aliquot of the extract by means of a Perkin-Elmer flame photometer, nmdel 52A, using an acetylene gas flame. The internal standard nmthod was employed. The calcium-potassium ratios were cal- culated from.averages of milliequivalents per 100 grams found in samples taken from the three replications on different dates. The leaves were dried at 600 C. and ground in a Wiley null. One gram samples of'the material were wet ashed (13) tWmeans of sulfuric acid, nitric acid, and perchloric acid; made up to standard volume; and analyzed for calcium.and P°tassium_content in the flame phoiometer Greenhouse Soil. Emmet fine sandy loam having an original pH of 6.5 and containing approximately five percent organic matter was used in 1951 e Treatments and Procedures. Twelve pots were each filled ‘flth 12 kilograms of the soil. Six individual pots were leached with 150 cc. of 6 Normal sulfuric acid solution. The Immaining six were leached with 185 cc. of 6 Normal sulfuric acid solution each. After being allowed to stand overnight, 13 every pot was flushed with three quarts distilled water. In order to apply the treatments, the above soils vwre repotted in the same 12 pots. Lhme at the rate of 1,000 pounds per acre was placed in a band at the nine inch level in pots 1, 2, 7, and 8. One thousand pounds of lime per acre was mixed throughout the top nine inches of soil in pots 3, h, 9, and 10. Pots 5, 6, 11, and 12 received no lime (Table 2). Soil moisture was maintained at a uniform level. On March 13, 1951 U. S. number two Chippewa potatoes of equal size were planted and fertilized with 1000 pounds or 3-12-12 per acre. Each pot was inoculated with the same amount of a solution of §. scabies made by washing potato peel, that contained scab lesions. Plants were thinned to a uniform.three stalks per pot on April h. The crop was harvested, sorted, and stored on June 5. The classifications of scabbiness used for the field grown tubers were employed here also. r11]. )115)... 3.1.19.4...3W... Auuwfiwwl r - L [ TABLE 2 LIME PLACEMENT Lime 1000 pounds per acre at 9 inch depth - band 1000 pounds per acre throughout top 9 inches 110116 1 CP CaC03 was used. Treated with 150 cc. 6 N H230“. pots 1 and 2 pots 3 and h pots 5 and 6 Treated with .185 cc. 6 N HZSoh pots 7 and 8 pots 9 and 10 pots 11 and 12 EXPERIMEN TAL RESULTS Field The presentation of data is such that it is comparable between treatments and years. The reporting of percent U.S. No. 1's and the yield index were devised to express the economic aspect of the experiment, whereas the percent of scab and heavy scab are included to present the actual vari- ations in scabbiness, disregarding amount of yield. The scab index shows the interrelationship between the three de- grees of scabbing and yields under each treatment. The exchangeable calcium and potassium content of soil samples, the yield index, the scab index, the percent U. S. No. 1's, the percent scab, the calcium and potassium in leaf samples, and specific gravity of potatoes were evaluated by analyses of variance at the 5% level. In 1951 increasing levels of potash produced a general trend-of scab reduction as indicated in Table 3 and Figures 1 and 3. This trend was accompanied by increased total yield, more U. S. No. 1's, and a lowered scab index. Although there were inconsistencies from one level of potassium to the next, as in the work of Schroeder and Albrecht (17), the statistical “817818 showed that the data are significant. The largest appliC‘vation of potash did not bring about the expected 1:1 15 16 .HH owed so endow on hag thHosaEnop o>ono on» no mcofipacauoa 0:.0 mma .m.z mm Am0.00 .0.m.q s0:.0 00.0 0: 0.000 0.00s 000 0:.a 0H 0m0.0 0m.m 0m 0.Ham 0.00 0am 0m.a 0 mam.0 00.m a: 0.3mm 0.00 0am m0.H 0 Hma.0 00.0 as 0.00m 0.~0 0am a0.m a m00.0 00.0 as 0.0:m 0.50 0am 0H.m o 00H.a ms.0 00 m.ema ~.00 04H 05.0 0 050.0 00.0 :0 0.00s m.eo Hos as.: m 0sa.0 0H.0 00 m.00a 0.00 Hmm «0.: : am0.a 00.0 H0 0.0HH s.m0 ems ~0.m m 0am.0 m:.a ea m.eo 0.~0 m0” :m.a a seam NopsH h>som seem H.oz .m.D .H.oz .m.D wooSH Haom one sobadz noon psoosom psoosom sauna eats» psoosom aflofi» ca xuao snosuaosa t 1 1 if) $3 .24me oza 930 09.3.3 20 momma spammsaomuzbaoqg so Emma m mam: 17 ratio but did produce the lowest scab index, the greatest yield, and the fewest scabby potatoes. From this year's re- sults, it would appear that Schroeder and Albrecht's theory that balanced exchangeable calcium and potassium will cause a decrease of scab incidence is valid. Potato plants grown on treatments 1, 2, and 3 showed varying degrees of potassium deficiency. Hillsdale soil is known to be low in available potassium and phosphorus. Hence, low potash applications with relatively normal applications of nitrogen and phosphorus would be expected to bring on the observed potassium deficiencies. Table h‘and Figures 1 and 3 give the results of the 1952 trials and indicate that decreased calcium-potassium ratios had no significant effect on.the total yields nor amount of U- S. No. 1's, but the percent scab showed a difference be- tween treatment 2 and all others except treatment 8. The Scab index showed no significant difference between treatments. The greatest yield and the largest quantity of U. S. No. 1‘s Were produced in the plots which received LL00 pounds of potash Per acre. It will be noted that the ratios of exchangeable calcium and potassium in the soil did not follow the treatments applied 30 closely as in 1951. This may be explained partly by the fact that plant roots sorb nutrients in ratios dissimilar to that of the cations on the exchange complex. 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Fig. 6. A comparison of the calcium- potassium ratios in the soil to the calcium-potassium ratios in the potato leaves. \ ‘ 9. \ \ -\ \ Leaf, 1951 O — o \ Leaf, 1952. 0- -------- '0 \\ Leaf. 1953 0— — ——-9 8. ‘ . Soil. 1951'9— _ 1 E1 \ Soil, 19521------__‘_i \ 5611, 1953 9.— ._ _x \ \ \ \\ . \\ \\ caICiUM‘Potassium Ratios \ \ \\ ‘ Leaf and Soil \ \ \o\ Tile/100 grams 6. \ \ \ \ \ \ \ \\ \ \ \ \ \ '1. \\ \ 5. \ \ ‘ \ \ \ \ \ \ ‘ \ \ \ \\\\ 4' \ \ W \ \ \ . A \ A \ \ M\ 3. \ \ \ x 8- \ \ \D/ “~o\““o‘ K\ \\\ \\ “‘~o\\ 1 \\ _ \\ KN-ki \ 230 \\ \\\\‘x------K--_--"‘——-.-X“\ \O \()\ \H —— ‘K N. \“X k ‘ \ l w“ \ \ \O \ Treatment Numbers \K 2.. 3. 4. 5. g 7, 8. 9, 10. 3h ratio in potato leaves similar to the exchangeable calcium- potassium ratio in the soil. The effect of added potash on dry matter content of the harvested tubers as measured by a hydrometer is shown in Table 12. The results of this test showed that no significant change in specific gravity was brought about by the increasing amounts of potash. These potatoes were of fair cooking quality as judged on the basis of their specific gravity (7). The effects of applying zinc in 1953 to soil which had received the ten potash treatments in 1951 are shown in Table 13. The results show that zinc caused no significant Changes in the yield nor the percent of U. S. No. 1's. The percent of U. S. No. l's did not increase as the amount of I Zinc was increased nor as the amount of potash was increased. Therefore, the interaction of potash and zinc on the soil and/or the causative agent appears to have been ineffectual in reducing scabbiness. The analysis of variance shows that the potash treatments caused a significant increase in potato Yie 1ds3as is seen in Table 13. (The additions of zinc caused no visible effects in the vegetative plant nor in the har- Ve s ted tubers . TABLE.12 35 EFFECT OF VARIOUS LEVELS OF PUTASH ON THE SPECIFIC GRAVITYa OF KATAHDIN POTATOES 1:239:81... 1951 1952 0 1,0737b 1.0657 50 1.0733 1.0600 100 1.0703 1.0680 150 1.0733 1.0683 200 1.0723 1.0690 250 1.0680 1.0660 300 1.0680 1.0683 350 1.0700 1.0663 “00 1.0687 1.0670 050 1.0683 1.0627 ‘1 a Using an 8-pound sample with a hydrometer b The average of samples from all three replications TABLE 13 36 EFFECT OF ZINC APPLIED TO HILLSDALE SANDY LOAM PREVIOUSLY TREATED WITH INCREASING AMOUNTS OF POTASH ON YIELD _—_L E AND SCABBINESS OF POTATOES Potash Zinc Treatments 1':- eatment’ _0__1bs. Zn/A 12.5 lbs. 331A 25 lbs. 291A 1.1.2121 031-1131: 92-1-1122: A“: 1 67 09.3 88 68.2 100 88.0 2 65 70.6 110 66.6 103 70.9 3 155 67.7 119 80.0 105 56.1 0 138 09.3 180 59.9 190 78.8 5 170 68.2 105 67.3 150 60.2 6 199 85.3 136 56.8 209 73.5 7 130 79.8 195 70.7 220 85.6 8 188 59.0 206 71.6 200 78.8 9 197 53.7 190 72.3 200 73.8 10 195 67.6 228 56.9 202 77.1 Zn L.S.D. N.S. N.S. (0.05) K20 L.s.D. 50.5 N.S. (0.05) 1 Pounds per plot were multiplied by ten to remove the de c imal point . 2 The percent of the total yield that were graded as c 1 ean and light 37 Greenhouse The addition of 1000 pounds of lime per acre throughout the top nine inches of leached Emmet fine sandy loam caused the pH to increase to some extent (Tables 10 and 15). Placing 1000 pounds of lime per acre in a band at the nine inch deprth.brought about no appreciable change in soil pH. These methods of lime placement caused no significant change in sod51 pH throughout the growing season (Table 15). Final pH Values shown in Table 15 indicate that mixing lime throughout the top nine inches of soil resulted in a higher soil pH than dixi placing lime in a band at the nine inch depth. Actual size photographs showing a sample representative 01' the tubers from each pH level and each treatment are presented. Comparing Plates 1, II, and III which show tubers P81 sed at the higher pH level (approximately 5.0), it can be seen that the largest and cleanest (See also Table 16) POtatoes were produced when lime was mixed throughout the top 111110 inches of soil (Plate II). Tubers of inferior size were I'aised in the soil which received no lime (Plate 111). Plate shows that cultures with deeply placed lime produced one large tllber which had medium scabbiness and several small tubers 1‘ ariging from medium to clean. Potatoes shown in Plates IV, V, and VI were those raised at the lower pH level (approximately 0.8). These were of similar scabbiness and size and showed that the methods of applying lime had exerted no beneficial effect. I 38 TABLE 10 pH VALUES RESULTING FROM LEACHING EHMET FINE SANDY LOAN WITH Two DIFFERENT AMOUNTS 0F 6 NORMAL SULFURIC ACID ‘ Pot- Original le 6 N H250“ pH after Leaching Number February 27 (cc.) March 1 l 6.5 150 5.0 2 6.5 " 5.0 3 6.5 " 5.11 0 6.5 " 5.0 S 6.5 " 5.6 6 6.5 “ 5.11 7~ 6.2 185 0.8 8 ' 6.2 " 0.8 9 6.3 ". 0.8 .10 6.3 "' 0.8 11 6.3 " 0.8 12 6.3 " 0.8 pH was detenmined by use of a glass electrode and a Beckman pH meter, model H-2, using a 1:1 soil-water ratio. 39 TABLE 15 pH VALUES OF EMMET FINE SANDY LOAM THROUGHOUT THE GROWING SEASON P’t Limel Placement pH after Liming "Mb” March 5 March 28 June 5 1 1000 lbs./A at 9 in. 5.0 5.5 5.0 2 1000 lbs./A at 9 in. 5.0 5.3 5.0 .3 1000 lbs./A through top 9 in. 505 So“ 506 (4. 1000 lbs./A through t0p 9 in. 5.7 5.6 5.6 5 none 506 501(- Sol). 6 none ' 5.11 5.3 5-3 7 1000 lbs./A at 9 in. 0.7 0.6 0.6 8 1000 lbs./A at 9 in. 5.0 0.9 0.6 9 1000 lbs./A through top 9 111. 5.0 500 “.09 10 1000 1b8./A through top 9 in. 5.0 5.0 0.9 11 none (4.06 LL06 . (4.6 12 none 0.6 0.6 0.6 CP calcium carbonate was used. 00 TABLE 16 SCABBINESS OBSERVED ON POTATOES FROM GREENHOUSE LIME PLACEMENT EXPERIMENT Pot Number Description of the Tubers 18 Clean to lightly scabby 2a Mostly clean with one tuber having medium.1esions 3b Clean to lightly scabby 0b Clean 5c Clean 6° Light scab in 3 tubers 7(1 Light scab in 2 tubers 8d Medium scab in 1 tuber e Most tubers showed medium scab; 2 with deep lesions 10° Mostly medium scab; 1 clean tuber l],f Medium scab in 2 tubers; others clean 12‘. Light scab in l tuber; remainder clean ‘ See Plate I d See Plate 1v ‘b See Plate II ° See Plate V c f See Plate III See Plate VI V "4-...- 'TM. 01 The effect of pH on scabbing and tuber size is shown by the fact that both methods of adding lime produced the largest potatoes which were nearly scab-free. The best potatoes were raised in soil at pH 5.6 with the addition of 1000 pounds of lime per acre mixed throughout the top nine inches of soil. It is known that potatoes require calcium in large amounts. Thus it was theorized that subplacement of lime would supply calcium to the roots without coming in con- tact with the growing tubers. It is possible that the mixing of lime throughout the top nine inches of soil at pH 5.0 produced a nutritive balance favoring crop growth and in a manner thought to be beneficial by Schroeder and Albrecht (17). PLATE I. Response of Chippewa potatoes in Emmet fine sandy loam with a pH of 5.0 after leaching to 1000 pounds of lime per acre placed in a band at a depth of nine inches. Pets 1 and 2. PLATE II. Reaponse of Chippewa potatoes in Emmet fine sandy learn with a pH of 5.0 after leaching to 1000 pounds of line per acre mixed throughout the top nine inches of soil. Pets 3 and 0. 1+3 PLATE III. Response of Chippewa potatoes in Emmet fine sandy loam with a pH of 5.5 after leaching. Pets 5 and 6. PLATE IV. 11.5 Response of Chippewa potatoes in Brunet fine sandy loam with a pH of 0.8 after leaching to 1000 pounds of line per acre placed in a band at a depth of nine inches. Pets 7 and 8. PLATE V. 06 Response of Chippewa potatoes in Emmet fine sandy loam with a pH of 0.8 after leaching to 1000 pounds of lime per acre mixed throughout the top nine inches of soil. Pets 9 and 10. 07 PLATE VI. Response of Chippewa potatoes in Emmet fine sandy loam with a pH of 0.8 after leaching. Pets 11 and 12. SUMMARY AND CONCLUSIONS Field studies on potato scab as affected by lowering calciur potassium ratios were conducted at the college farm in East Lansing, Michigan in 1951, 1952, and 1953. Zinc treatments of the soil were included in the 1953 experiments. Lime placement trials were performed in a 1951 greenhouse In 1951, in an effort to obtain a 1:1 calcium-potassium 'balance, 10 potash treatments were applied to two areas of IHillsdale sandy loam in two increments. Katahdin potatoes ‘were planted on one of the areas in 1951. The resulting data show that decreasing calcium-potassium ratios led to increasing yields with a lowered scab index. The second area was planted to Katahdins in 1952 without :further potash treatment. The yields and scabbiness were not (sonsistently affected by lowered calciumppotassiwm ratios. In 1953 three varieties of potatoes, Katahdin, Chippewa, and Sebago, were grown on the original area to which had been applied additional amounts of potash in an effort to bring Elbout a calcium-potassium ratio of 1:1. The results of this firear's trials point out that Katahdins had significantly less scab with lowered calcium-potassium ratios than did Esebagos and Chippewas. 08 Eb”,- aru.“ . ' a! 09 In comparing the scab indices of the Katahdins in 1951, 1952, and 1953, it was found that there was a significant dif- ference between years (L.S.D. 0.36). The least scab occurred in 1953 e The use of zinc as a controlling factor for reducing scab was tried on the second area in 1953. No beneficial action was exerted by the addition of 12.5 or 25 pounds of zinc per acre. From the greenhouse study carried out in 1951 on Emmet fine sandy loam with two pH levels, limed, lime-banded, and r I no lime, the lower pH did not result in the least scabbiness. The best yield and the potatoes freest from scab were raised in the soil having the higher pH (5.6) in which 1000 pounds of lime per acre had been mixed throughout the top nine inches of soil. The results of this trial agree with the tvork of Rich (l0), Starr (18), and others who have found little correlation between scab and soil pH. They do not agree with the findings of Nelson and Brady (ll). Katahdin leaf samples and soil samples were taken from 8.11 field plots, except those treated with zinc, in 1951, 3J952 and 1953. There was a general trend_of decreasing exp changeable calcium content in the soil from the first to the last year because no lime was added. Within years, the added Emotash caused no significant difference in the exchangeable (Balcium content of the soil. However, as would be expected, the potassium content of the leaves correlated with the 50 addition of the potash to the soil. The calcium in the leaves and soil showed no significant differences because of treatment. There was a reciprocal relationship between calcium and potassium uptake by the leaves in 1953. Determinations on Katahdins grown in 1951 and 1952 in- dicated that potash levels up to 050 pounds per acre did not significantly lower the specific gravity of the tubers. The cooked potatoes were of medium mealiness, as was indicated by the hydrometer. From the data presented here, it can be concluded that: l. The addition of potash did not uniformly de- crease the percent of scab but generally caused a lowered scab index for Katahdin potatoes within each year. 2. Increasing the exchangeable potassium content of the soil resulted in an increased growth response. 3. There is a difference in varietal susceptibility ‘to scab and in response to the scab decreasing effects of Ilowered calcium-potassium ratios. 0. Addition of lime to a soil may result in increased tniber growth without enhancing the effect of'§. scabies. 5. Zinc at rates of 12.5 and 25 pounds per acre <11d.not suppress the growth of §. scabies as measured by the percent of scabby potatoes. 6. The dry matter content of Katahdin potatoes was Ilot adversely affected by high applications of potash in this eXperiment . 1. 2. 3. 0. 9. 10. Ill. 1L2. 51 LITERATURE CITED Association of Official Agricultural Chemists. Official and tentative methods of analysis. Washington, D. 0. Ed. 6:3—0, 1905. . Bessey, E. A. Morphology and Taxonomy of Fungi. The Blakiston Company, Philadelphia, p. 585, 1950. Blodgett, F. M. and E. K. Cowan. Relative effect of calcium and acidity of the soil on the occurrence of potato scab. Amer. Potato Jour. 12:265-278. 1935. Cook, H. T. and C. V. C. Houghland. Severity of potato scab in relation to the use of neutralized and one-third neutralized fertilizers. Amer. Potato Jour. 19:201-208, 1902. Drosdoff, M. and D. C. Nearpass. Magnesium - qualitative micro-determination in plant tissue and soil extracts. Indus. and Engin. Chem. Analyt. Ed. 20:673-670, 1908. Fellows, H. Relation.of growth in potato tuber to the potato scab disease. Jour. Agr. Res. 32:757-781, 1926. Hardenburg, E. V. Potato Production. Comstock Publishing Co., Inc., Ithaca, New York, Appendix, 1909. Heald, F. D. Manual of Plant Diseases, 2nd. Ed. Mc-Graw Hill Book Company, Inc., New York, pp. 375-383, 1933. KenKnight, Glenn. Studies on soil Actinomyces in relation to potato scab and its control. Mich. State 0011. Agr. Exp. Sta. Tech. Bul. 178, 1901. Muncie, J. H., H. C. Moore, J. Tyson, and E. J. Wheeler. The effect of sulfur and acid fertilizer on incidence of potato scab. Amer. Potato Jour. 21:293-300, 1900. Nelson, W. L. and N. C. Brady. Effect of subsurface appli- cation of lime on yield, scab, and nutrient uptake of Irish potatoes. Soil Sci. Soc. Amer. Proc. 8:313-316, 1900. Peech, M., L. T. Alexander, L. A. Dean, and J. F. Reed. Methods of soil analysis for soil—fertility investiga- tions. U. S. D. A. circular 757. l3. 10. 15. 16. 17. 18. 19. 20. 21. 22. 23. 20. 25. 52 Piper, C. 3. Soil and Plant Analysis, lst Ed. Inter- science Publishers, Inc., New York, pp. 168-176, 1900. Rich, A. E. Some factors affecting the yield and grade of Green Mountain potatoes in Rhode Island. R. 1.. Agr. Exp. Sta. Bul. 297, 1905. Reed, H. S. The value of certain nutritive elements to the plant cell. Annals of Bot. 21:501-503, 1907. Salaman, R. N. The History and Social Influence of the Potato. Cambridge University Press, England, 1909. Schroeder, R. A. and Wm. A. Albrecht. Plant nutrition and «the hydrogen ion: II. potato scab. Soil Sci. 53:081-089, 1902. Starr, G. H. Effect of moisture and other factors on potato scab. Amer. Potato Jour. 20:279-287. 1903. Stone, G. E. and G. H. Chapman. Experiments relating to the control of potato scab. Mass. Agr. Exp. Sta. Ann. Report part I, 1913. Thaxter, R. The potato scab. Conn. Agr. Exp. Sta. Bul. 105:3-h, 1890e Waksman, S. A. and A. T. Henrici. Nomenclature and classification of the Actinomycetes. Jour. Bact. 06: 33 7’3LI'1 , 19143 e Wheeler, H. J., J. D. Towar, B. L. Hartwell, and c. L. Sargent. Potato scab. R. I. Agr. Exp. Sta. Buls. 26, 1893; 339 18953 MO. 1896. Hingerberg, F. Studien fiber den gew8hnlichen Kartoffel- schorf und seine Erreger. Kuhn-Arch. 33:293-295, 1933. Hollenweber, H. H. Der Kartoffelschorf. Arb. d. ‘ Forschungsinst. f. Kartoffelbau 2:1-102, 1920. Yearbook of Agriculture. Science in Farming, U. S. D. A., Uashington, pp. 327-332, 1907. Date Due -ff. I r f "f P! SIN 4' Hug“. ’ - .2 ‘4 “it o u~ ‘;‘ m Demco-293 «wimmmm