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AL? ... 235.»..- . ‘ (.... .. .- .‘no... 2 . .W‘.vs.1..oq-u. .. o v. .... _ . . .N ...... ._ .u -r . . .. \ . ...... p . u~ r. ..r 5.» A9,, Dob-.... u.. ..Jcrugn . . r l IHI\HllllllllllHllHHlllllllll’mlllllHIllll‘llllllfllll 1 31293017070 LIBRARY Michigan State University ABSTRACT EFFECTS OF NITROGEN FERTILIZATION ON THE SOD DEVELOPMENT OF KENTUCKY BLUEGRASS (Poa pratensis L. Merion) 0N HOUGHTON MUCK AS MEASURED BY SEVERAL NITROGEN RESPONSES By Kendall R. English It is known that excessive application of nitrogen reduces root and rhizome growth. Roots and rhizomes are necessary for a well-knit sod and rapid root and rhizome knitting is an essential goal of sod production. The problem is in finding a guide to nitrogen fertilization of sod. Using color as a guide for fertilization may cause over- fertilization, resulting in reduced root and rhizome growth. Limiting nitrogen levels will produce a weak, thin and poorly-developed sod. Excessive nitrogen, on the other hand, tends to slow sod development, thereby prolonging maintenance and increasing costs. The purpose of this study was to determine the value of soil nitrate tests and clipping analyses for predicting the nitrogen needs for rapid sod development. To do this, a series of 16 nitrogen treat- ments were used. Merion Kentucky bluegrass (Poa pratensis L.) was seeded in the fall of 1969 at 40 pounds per acre. Factors studied were soil nitrate tests, clipping weights, nitrogen content of the clippings, total soil nitrogen, sod strength, rhizome length and weight, and re- rooting ability of the sod in the greenhouse. Kendall R. English The soil nitrate tests were not sensitive enough to discern among the lower nitrogen rates (0 to 30 pounds nitrogen per acre per month) which would be practical for sod. With high nitrogen rates (120 pounds nitrogen) the variation in values was extreme. As nitrogen was increased clipping weights and nitrogen content in the clippings increased accordingly. The nitrogen content of the clip- pings was especially affected by fertilization and seasonal influences. Sod strength and rhizome growth measurements obtained on July 22 were generally consistent. Higher nitrogen decreased sod strength and rhizomes. Timing of nitrogen application had a significant effect on both variables. The treatment which received 15 pounds nitrogen per month throughout the season gave consistently strong sod as well as those treatments which did not receive nitrogen after late spring. Rerooting ability of the sod was affected by nitrogen application prior to harvest. The higher nitrogen rates reduced rerooting which prolonged establishment. This study did not result in any test that would determine nitro- gen needs but valuable insight was gained into seasonal variations of nitrate levels in the soil, shoot growth and percent nitrogen in the clippings. Other important considerations are rate and time of fertiliza- tion effects on stress conditions. EFFECTS OF NITROGEN FERTILIZATION ON THE SOD DEVELOPMENT OF KENTUCKY BLUEGRASS (Poa pratensis L. Merion) ON HOUGHTON MUCK AS MEASURED BY SEVERAL NITROGEN RESPONSES By 0 Kendall Rl‘English A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Crop and Soil Sciences 1971 TO ROBERT J. KRAUS I dedicate this thesis to Robert J. Kraus, a brother and a friend, for his encouragement. ii ACKNOWLEDGMENTS The author wishes to express sincere appreciation to his major professor, Dr. Paul E. Rieke, for his interest, patience, and untiring encouragement during these investigations. Special recognition is expressed to Dr. B. G. Ellis for his assistance and advice. The author is grateful for the assistance of Betsy Bricker in computer programing, Bill Weaver, and Joel Cooper for their performance in the field and laboratory. Last, but not least, the author wishes to express his sincere gratitude to the Soil Science Department for its financial support. iii TABLE OF CONTENTS ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . LIST OF TABLES O I O O O O O O O O O O I O O O O 0 LIST OF FIGIJRES I O O O O O O O O O O O O O O O O INTRODUfl I ON 0 O O O O O O O O O O O O O O O O O O L ITEMTIJRE REVI EW 0 I O O O O O O C O O O O O O O 0 Organic Soil: Sod Industry: Research: MATERIALS AND METHODS . . . . . . . . . . . . . . . I. II. III. IV. V. VI. VII. Plot location and design . . . . . . . . Establishment . . . . . . . . . . . . . . Nitrogen treatment and application . . . Soil sampling . . . . . . . . . . . . . . Clippings . . . . . . . . . . . . . . . . Sod strength . . . . . . . . . . . . . . Rhizome weight and length . . . . . . . . Laboratory Analyses . . . . . . . . . . . . . . I. II. III. Nitrate analyses of soil samples . . . . Total nitrogen analyses of the clippings Total nitrogen analyses of the soil . . . Greenhouse rerooting experiment . . . . . Statistical methods . . . . . . . . . . . Units of measure . . . . . . . . . . . . RESULTS AND DISCUSSION . . . . . . . . . . . . . I. II. III. IV. V. VI. VII. Nitrate soil test . . . . . . . . . . . . Clipping weights . . . . . . . . . . . . Sod strengths . . . . . . . . . . . . . . Length and weight of rhizomes . . . . . Percent total nitrogen of the clippings . Total nitrogen content of the soil . . . Greenhouse rooting study . . . . . . . iv origin, properties, and management . history, development, and management effects of nitrogen fertilization on turf vii oooxw 14 l4 l4 14 15 16 16 17 18 18 20 21 21 22 22 23 23 30 39 45 48 51 53 SUMMARY . . . . . CONCLUSIONS . . . LIST OF REFERENCES APPENDIX . . . . v 65 69 Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. Table 8. Table 9. Table 10. Table 11. Table 12. Table 13. LIST OF TABLES Pounds of actual nitrogen applied per acre and application dates . . . . . . . . . . . . Nitrate nitrogen in soil, ppm . . . . . . . . Fresh clipping weights for Treatments 1 through 4, pounds per acre . . . . . . . . . Fresh clipping weights for Treatments 5 through 8, pounds per acre . . . . . . . . . Fresh clipping weights for Treatments 9 through 12, pounds per acre . . . . . . . . . Fresh clipping weights for Treatments 13 through 16, pounds per acre . . . . . . . . . Field observations on sod strengths and root and rhizome weights of Merion Kentucky bluegrass grown for sod on Houghton muck . . Percent nitrogen in clippings for Treatments 1 through 5 . . . . . . . . . . . Spectrographic analyses for several elements of clippings for Treatments 1 through 4 on four selected dates . . . . . Percent nitrogen of Houghton muck for four selected dates . . . . . . . . . . . . . Root and clipping weights from the greenhouse rooting study, averages for three replications . . . . . . . . . . . . Accumulative dry clipping weights, pounds per acre, Treatments 1 through 8 . . . . . . . . Accumulative dry clipping weights, pounds per acre, Treatments 9 through 16 . . . . . . . . vi Page 15 24 31 32 33 34 40 51a 52 53 55 69 7O Figure Figure Figure Figure Figures 5 and 6. Figure Figure Figure Figure Figure Figure Figure 10. 11. 12. 13. LIST OF FIGURES Average ppm nitrate nitrogen in soil for Treat- ments 1 through 4 of O, 30, 60, and 120 pounds nitrogen per acre, respectively . . . . . . . Average ppm nitrate nitrogen in soil for Treatments 9 through 12 . . . . . . . . . . . Average ppm nitrate nitrogen in soil for Treatments 13 through 16 . . . . . . . . . . Accumulative fresh clipping weights for Treatments 1 through 5 (O, 30, 60, 120, and 15 pounds nitrogen per acre applied monthly, respectively . . . . . . . . . . . . . . . Accumulative fresh clipping weights for Treatments 9 through 12 and Treatments 13 through 16, respectively . . . . . . . . . . Sod strengths for Treatments 1 through 8 on July 22 and October 15, 1970 . . . . . . . Sod strengths for Treatments 9 through 16 on July 22 and October 15, 1970 . . . . . . . . Length of rhizomes in a 4 1/4 inch plug for Treatments 1 through 8 on July 22, 1970 . . Length of rhizomes in a 4 1/4 inch plug for Treatments 9 through 16 on July 22, 1970 Mg rhizomes in 4 1/4 inch plug for Treatments 1 through 8 on July 22, 1970 . . . . . . . . Mg rhizomes in 4 1/4 inch plug for Treatments 9 through 16 on July 22, 1970 . . . . . . . . Roots produced by 4 1/4 inch plug of sod in 37 days in the greenhouse on a sandy loam soil vii 25 27 28 35 37 41 43 46 47 49 50 54 INTRODUCTION Commercial sod production has grown rapidly in recent years in Michigan. This growth has been primarily due to the demand for sod by our affluent society. Sodding has become an accepted means of establishing a turf. The advantages of sodding over seeding are: an immediate turf is established minimizing dust and mud problems; a quality turf can be established anytime during the growing season; and areas not easily established, such as slopes, are more readily established. Michigan is well suited for sod production with reasonably moder- ate temperatures and extensive organic soil deposits located near metropolitan areas. Initially the bulk of the sod was produced on mineral soil, but most of the recent increase in production has occurred on organic soils. Production on organic soil has increased about ten fold between 1955 and 1965. Organic soils are ideally suited for production being relatively level. Sod produced on organic soil is lighter in weight allowing lower transportation costs. The objective of sod production is to obtain a uniform stand of high quality turfgrass free of weeds, with acceptable color, sufficient maturity, and a root and rhizome system developed to a point where sod can be harvested and handled. The availability of improved Kentucky bluegrass varieties, development of the sod harvester, and utilization of effective pesticides, particularly herbicides, have eliminated many obstacles in producing sod. Although all essential elements must be available to the turfgrass plant in adequate quantities, nitrogen is the most important nutrient which the sod producer controls. Nitrogen has a major influence on turfgrass color and growth. Excessive nitrogen promotes shoot growth at the expense of root and rhizome growth, thus weakening sod. Using color as a guide to nitrogen fertilization may result in excess nitrogen application. On the other hand, the sod may be weak and will not have an acceptable color if little or no nitrogen is used. There is a need for an effective means of determining the amount of nitrogen needed for growth and development of a mature sod. It is the purpose of this investigation to study the effect of nitrogen fertilization on soil nitrate tests, clippings produced, nitrogen content of the clippings, and sod strengths. The ultimate objective is to determine the value of soil nitrate tests and nitrogen content of the clippings in predicting nitrogen needs for sod production on organic soil. LITERATURE REVIEW Organic Soil: origin, properties, and management. Basins, lakes, and river beds provide conditions suitable for the development of organic deposits. Glaciation has left the topography in many areas conducive to the formation of swamps and marshes by impeding drainage (8). This has resulted in leaving the region liberally dotted with organic deposits ranging from a few inches to several feet in depth. Organic soil formation occurs under water or where high ground water levels keep the accumulating organic matter partially saturated. The high water table and ideal climatic conditions produced a highly favorable environment which encouraged the growth of many plants. The plants in endless generations accumulated in the water in which they grew. The water acted as a preservative, by keeping microbial activity to a minimum, thereby delaying decomposition. The result was an accumulation of organic material from preceding generations of vegeta- tion. Michigan had the conditions for organic soil development to occur and its landscape is dotted with such soils. There are 4-1/2 million acres of organic soil in Michigan (11). Some deposits are so small that it is uneconomical to bring them under cultivation, but others are large and many of these are in crop production. An organic soil is one that contains at least 30% organic material to a depth of one foot. Most organic soils in Michigan could be 3 4 described as containing 80% organic material. The materials composing organic soils have been extensively described as accumulations of the plant remains. Plant remains are those parts of a plant which are relatively resistant to rapid decomposition. Two textures, peat and muck, are arbitrarily recognized by those who manage organic soils (8). A.well decomposed organic soil is referred to as a muck while a slightly decomposed soil is a peat. An organic soil may be well decomposed on the surface but underlying layers may be only slightly decomposed peat. Thus, in many instances peat has a layer of muck above it. With the advent of drainage, a peat may be oxidized to muck. Organic soils are classified on vegetative material composition, chemical reaction, depth of the deposit, and the nature of underlying material if the depth of the deposit is less than 42 inches (11). The management of organic soils is quite different than for mineral soils. Artificial drainage is usually needed for crop produc- tion because organic soils were formed under poorly-drained conditions (3). Irrigation is a common practice on organic soils to supplement natural precipitation because of the high productivity of organic soils. The plowing of organic soils is largely for the purpose of covering trash and crop residues rather than for aeration. Organic soils generally need packing rather than loosening (12). It has long been recognized that organic soils are rich in nitrogen (12). Under certain conditions, however, it may be quite unavailable to growing plants. High acidity, high water table and cool soil temperatures result in slow release of nitrogen. The nitrogen is released from organic material decomposition by soil microbes. The microbes convert very complex organic molecules to an inorganic state. This conversion is called mineralization (1). During this process organic nitrogen is changed to ammonia which is in turn rapidly oxidized to nitrite and than nitrate (29). Nitrates tend to accumulate in organic soils during the growing season. The amount of accumulation is dependent on both temperature and moisture conditions of the soil (2, 45). wyler and Delnrche (48) showed that water content of soils indirectly influences nitrogen losses from denitrification by inhibiting oxygen diffusion. As the moisture content increases in the soil the amount of oxygen decreases limiting oxidation of the ammonia. Therefore, the nitrogen-fertilizer need for crops grown on organic soils is very dependent on weather conditions that influence soil temperature and moisture. Nitrates are also subject to leaching, denitrification, and volatilization. Even under ideal conditions for mineralization, nitrates may be removed from the soil. Broadbent and Stojanovic (7) found a 16% loss of tagged nitrogen, applied as nitrate nitrogen, under fully aerobic conditions. The losses increased as oxygen tension decreaSed in the soil. The activity of the microbes is very low when soil temperatures drop below 5 C and very little organic nitrogen is released (1, ll). Throughout the growing season an increase in soluble nitrogen can be expected from the decomposition of organic material because of the greater activity of microbes in response to an increase in soil temperature. The nitrogen content of organic soils ranges from 0.3 to 4.0% with reed-sedge peats being at the higher end (11). The plant composition of the organic deposit affects the nitrogen level in the soil. The carbon-to-nitrogen ratio is significant as well. For microbes to thrive the ratio must be close to 10 to l (24). Soil tests for nitrogen have not proved valuable for evaluating soil nitrogen supplying capacity of soils. Results from nitrogen tests are complicated by the fact that nitrogen availability depends on decomposition of organic matter (42). Sod Industry: history, development, and management. Sod production is the fifth largest agricultural industry in Michigan (23). Only limited research has been conducted on sod produc- tion because of its small acreage until recent years and because it has not been considered an important agricultural commodity. Sod production is not a new industry to Michigan, however. Commercial sod was first available in 1919, limited primarily to sod of high quality (33). During the developing years, a common prac- tice employed for low quality sod was to mow a Kentucky bluegrass pasture closely for two or three months and then harvest the sod. Sod production has now evolved to a point where the sole objective on many farms is to grow and sell quality sod. The period of rapid growth began in the middle 1950's. The primary cause of growth was the affluence of our society which was ready to accept sod as a source of an immediate lawn eliminating the time necessary to establish a lawn from seed. Key factors in the development of the expanding industry were the advent of improved Kentucky bluegrass varieties, development of herbicides and pesticides, and technological advances. Prior to the period of rapid growth, almost all the sod acreage occurred on mineral soils. To meet the need of the expanding industry many farms on organic soils were taken out of vegetable production and placed in sod. Thus, most of the growth of the industry occurred on organic soils, according to Beard g£_al, (4). In just ten years the acreage on organic soils increased from about 2,000 acres in 1955 to over 20,000 acres in 1965 (33). This rapid increase has slowed only recently. Organic soils are better suited to sod production than mineral soils. Rieke and Lucas (34) stated that there are several advantages of organic soils over mineral soils in sod production. It generally takes 12 to 18 months to produce a high quality sod on organic soil; mineral soils often take six months longer (3). Organic soils are free of stones and provide relatively flat areas which facilitate establish- ment. In a comparison of sod grown on organic and mineral soils, Dunn and Engel (14) found no differences in their rerooting ability, although the thin out sod of either soil rooted much faster. King and Beard (18) ranked organic soil higher in root production, but not significantly. A species or variety of turfgrass utilized for sod must be rapid and vigorous in establishment and have a rapid root and rhizome develop- ment (3). Merion Kentucky bluegrass (Poa pratensis L.) dominates the sod industry in Michigan. Rieke and Beard (32) believe that Merion comprises most of the sod acreage because of its vigorous rhizome growth and sod-forming characteristics and its resistance to Helminthosporum leafspot. The objective of sod production is to obtain a uniform stand of turf possessing a root and rhizome system developed to the point where a piece of sod may be harvested and handled without tearing. High quality sod characteristics are: uniformity, good shoot density, acceptable color, freedom from serious weeds or diseases, adequate sod strength for handling, sufficient carbohydrate reserves for rapid re- rooting, and a minimum thatch layer as clarified by Beard 35 a1. (4). Sod production has recently become very competitive because of expanded production and because the economy has restricted the market for commercially-grown sod. Thus, to be competitive, the grower must be extremely aware of his costs. Reducing the time between planting and harvest is one important means of reducing cost; still, he must have a saleable product that is acceptable to the consumer. Schmidt (38) suggested that the more rapidly the root system develops the sooner the crop can be harvested. The root system must be sufficient to hold the sod together during harvest, handling, and lay- ing. The time needed for a sod to develop sufficiently has varied from less than six months to two years or more. Turf maintenance practices for sod production should consider root and rhizome growth primarily with less emphasis placed on the above— ground portion of the plant (3). Following establishment fertilization may be restricted to nitrogen if the phosphorus and potassium needs have been satisfied by seedbed fertilization (32). Daniel (10) felt that once a turf is established for sod it should be maintained with a moderate nitrogen fertility until the time of sale approaches. Research: effects of nitrogen fertilization on turf. The importance of nitrogen for turfgrass is well documented. Roberts (35) felt the nitrogen influence on turfgrass growth and quality was greater than any other mineral nutrient used in turf fertilization. Its most direct effect is on the growth of the plant. According to Schmidt (38), nitrogen fertilization enhances photosynthesis and normally stimulates respiration and top growth causing a net reduction of plant carbohydrate reserves. Nitrogen stimulates growth of the upper portion of the plant and it improves the appearance of the turf. Nitrogen deficiency is easily recognized by the chlorotic appearance of the turfgrass plant. Nitrogen requirements depend on many variables including clippings (removed or not removed), soil reaction, soil fertility level, physical condition of the soil, fertilizer characteristics, water program, weather, and the use that will be made of the turf according to Juska and Hanson (17). One of the most important factors in determining the nitrogen fertilizer need is the fertility level of the soil. Grable and Johnson (15) found that soils with a high organic matter content were yielding significantly more perennial ryegrass than soils with low organic matter content. This was probably due to a higher nitrogen fertility level associated with more organic matter. In dealing with an organic soil, the nitrogen fertility requirements may be different than with a mineral soil. Under normal soil conditions, nitrate is the principal source of nitrogen utilized by most higher plants; it is absorbed into the plant, reduced to ammonia and then incorporated into amino acids and proteins for plant growth (39). Ward (46) reported that most grasses prefer- entially absorb nitrogen in the nitrate form but may also absorb ammonium nitrogen. It is well documented that there is an increase in top growth with increased nitrogen. Dotzenko (13) found marked increases in the forage of six forage grasses from nitrogen fertilization. McLean (22) reported 10 that plants grown under variable nitrogen levels produced increased top growth with higher nitrogen rates for 20 agronomic crops including some grasses. Ramage gt El. (30) also had the highest dry matter yield of orchardgrass and reed canarygrass with the highest rate of nitrogen fertilizer. Another important effect of nitrogen fertilization on the turf- grass plant is on root growth. The root system is of primary importance in sod production. Earlier reports (18, 26) show that nitrogen fer- tilizer, particularly at higher rates, stimulates top growth at the expense of root growth. Oswalt g£_§l, (27) found that roots of orchardgrass and bromegrass reached a greater depth when no nitrogen was applied. Long, slender roots result where nitrogen levels were low, whereas nitrogen increased the root diameter and decreased the rate of elongation causing shorter roots (5, 43). Schmidt (38) felt that root growth could be improved with low additions of nitrogen but higher amounts would inhibit root development. Therefore, nitrogen fertilizer has the greatest influence on the development of sod. Too little or no nitrogen leaves a weak, poorly developed turf which is subject to weed invasion reducing sod quality. On the other hand, excessive nitrogen tends to delay development of sod (36). The growth of roots on a Kentucky bluegrass plant is perennial. Stuckey (41) found differences in the type of root regrowth for various grasses. Some species initiate new roots and the old roots die while other species maintained growth of the old roots and initiated few new roots. There are also peak periods of root growth. Stuckey (41) reported that root growth occurred mainly in the spring and fall on most species of grass and that during the summer months no elongation occurred and no new roots appeared. ll Increases in shoot growth and decreases in root growth occur simultaneously. Oswalt g£_a1, (27) found the addition of nitrogen increased the weight of shoots while decreasing the weight of roots, the number of roots, and the rate of root elongation. Harrison (16) reported that high nitrogen caused the plants to stop producing rhi- zomes during the fall with short, cloudy days and many roots and rhizomes died due to a lack of carbohydrate reserves. Madison 23 21, (21) found that increasing nitrogen not only increases yield but also verdure (quantity of green turf) and chlorophyll, while decreased rooting resulted. Upon casual observation, the effect of nitrogen fertilizer is to improve color and stimulate growth but many physiological changes occur as well. Carroll (9) found that high nitrogen fertilization of turf- grasses caused them to be less able to withstand adverse conditions. Dotzenko (13) observed a loss of stand at high rates of nitrogen on six grasses. Pellet gt a1, (28) found that high nitrogen reduced resistance to high temperature stress more than low nitrogen, while phosphorus and potassium had no effect on the Kentucky bluegrass. Turfgrasses fertilized with high rates of nitrogen have compara- tively low carbohydrate reserves and consequently are subject to rapid deterioration during periods of stress. Schmidt (38) found that respiration and top growth have priority over root development in utilizing carbohydrates. Stimulated growth, encouraged by heavy nitrogen, is produced by depleting the carbohydrates and other food reserves. Pellet £5 31, (28) felt that the use of carbohydrates and food reserves for growth makes them unavailable for differentiation processes necessary for increased resistance of plant tissues to unfavorable conditions. 12 It is of interest to consider the nitrogen content of the clippings as affected by various amounts of nitrogen fertilizer. Dotzenko (13) reported a higher percentage total nitrogen in the forage of six grasses with an increase in nitrogen fertilizer applied but a reduced percentage of nitrogen recovered. Volk and Horn (44) found the percentage of nitrogen in bermudagrass was always highest with the higher nitrogen applications, which in general agreed with the visual turf ratings for color. Walker £5 31. (45) found that Italian ryegrass uptake of both fertilizer nitrogen and soil nitrogen increased with the amount of nitrogen applied. Grable and Johnson (15) reported the nitrogen content of ryegrass was increased in every instance by additions of nitrate nitrogen but nitrogen content decreased from the first clipping date to the last because only one application was made at the beginning. Nitrogen fertilization seems to bring on a new flush of growth but as time passes the nitrogen disappears. Mortimer and Ahgren (25) observed that the percentage of nitrogen in herbage of Kentucky bluegrass varied directly with the amount of nitrogen fertilizer applied and that grass with a high nitrogen content is produced only where frequent applica- tions of nitrogen are made throughout the growing season. Nitrogen recovery decreases with amount of nitrogen applied. Grable and Johnson (15) reported that, in field experiments using rye- grass, efficiency decreased with increasing increments of nitrogen in nearly every instance. They also found greater efficiency in the greenhouse, possibly due to the fact that leaching did not occur in the greenhouse. Ramage §£_§l, (30) reported percentage nitrogen recovery decreased with increasing rates of nitrogen applied except for the lowest rate. Scarsbrook (37) studied the efficiency of nitrogen 13 fertilizers and found that ammonium nitrate resulted in the highest nitrogen recovery on bermudagrass. The type of fertilizer is of importance as to its rate of nitrogen release, but Juska and Hanson (17) reported the rates and time of application appeared to be of greater importance in maintaining turf quality than did sources of nitrogen. Overstimulation, following one heavy application of nitrogen, can be more serious than the same amount applied in several applications (17). For the production of a high-quality sod, proper manipulation of nitrogen is needed. Kurtz (19) concluded that 4 pounds of nitrogen per 1000 sq. ft. over a period of three months produced higher-quality sod on a mineral soil than did lower nitrogen rates. This treatment produced the most top growth, initiated the most rhizomes, and had the greatest turf density. Satari (36) in sod production studies on Houghton muck found that nitrogen reduces the production of rhizomes only during the later stages of development. Potassium also played an important role. He showed that root production was highly correlated with rhizome pro- duction and nitrogen reduces the yield of both with increased amounts applied. It can now be understood why nitrogen is the key nutrient in turf- grass growth and development. The manipulation of nitrogen for rapid sod development is an important management variable. Presently, color is the most important guide to nitrogen fertilization. It is rather abstract and may lead to errors. It is purposed that this study will aid the development of a more meaningful technique for nitrogen fertilization of sod. MATERIALS AND METHODS 1. Plot location and design. Field plots were established at the Michigan State University Muck Experimental Research Farm. The soil samples taken from the area were analyzed by the Michigan State University Soil Testing Laboratory. The results of this analysis were pH 6.9; phosphorus and potassium were adequate for sod. Individual plot size was 9 feet by 15 feet. Sixteen treatments were applied with three replications for each treatment in a randomized block design. II. Establishment. The plot area was plowed to a depth of 12 inches, followed by discing and leveling operations for a firm, smooth seedbed. A Brillion cultipacker-seeder was used to seed Merion Kentucky bluegrass (Poa pratensis L.) at 40 pounds per acre on August 29, 1969. III. Nitrogen treatment and application. Ammonium nitrate (33.5% N) was used as the nitrogen source. All fertilizer applications were weighed in the laboratory and applied by hand to control application rates carefully. A long plywood board was used as a guide for the boundaries to prevent any overlapping. The nitrogen treatments utilized are given in Table l. Seedbed nitrogen treatments were applied to the soil surface immediately after seeding l4 15 and were raked in with a light hand raking. Treatments 9 through 12 did not receive nitrogen until after the seedlings were established on October 6, 1969. The first nitrogen treatments in the spring were applied May 1, 1970 when drainage and weather conditions allowed. Subsequent applica— tions were approximately a month apart except for September when frequent rains prevented application before September 30. Table 1. Pounds of actual nitrogen applied per acre and application dates. Total Treatment 1969 May 1 June 5 June 30 Aug 4 Sept 30 for 1970 l 0* 0 0 0 0 0 0 2 30* 30 30 30 30 30 150 3 60* 60 60 60 60 60 300 4 120* 120 120 120 120 120 600 5 0* 15 15 15 15 15 75 6 30* 15 15 15 15 15 75 7 60* 15 15 15 15 15 75 8 120* 15 15 15 15 15 75 9 0** 30 30 30 0 0 90 10 30** 30 30 30 30 30 150 ll 60** 30 30 30 60 60 210 12 120** 30 30 30 120 120 330 13 30* 30 30 0 0 0 60 14 30* 30 30 30 30 30 150 15 30* 30 30 60 60 60 240 16 30* 30 30 120 120 120 420 *Ammonium nitrate in seedbed August 29, 1969. **Topdress application of ammonium nitrate October 6, 1969. IV. Soil sampling. Soil samples were taken during the 1970 growing season on a bi— weekly interval from all plots. A stainless steel soil probe was 16 used to take eight cores at random from each plot. Since most of the turfgrass roots are located within four inches of the soil surface, it was decided to sample to that depth. All surface vegetation was removed from the cores to facilitate handling in the laboratory. The samples were collected in one-pint plastic freezer bags to prevent loss of moisture or nitrates. The samples were stored in a cold room at 3 C until extraction could be performed. V. Clippings. Mowing commenced May 18, 1970 continuing at twice-seweek intervals except when weather conditions prevented mowing and during August when growth was especially slow. Mowing was done after the dew had evap— orated and the turf was essentially dry. An l8-inch, reel-type mower with a catcher attachment was used to collect the clippings from an area 18 inches wide and 13.5 feet long in the middle of each plot. The entire plot area was mowed with a 5-gang, reel-type mower after comple- tion of the sampling. Mowing height was 1 1/2 inches. The harvested clippings were placed in a paper sack. The sacks were taken immediately to the laboratory for weighing for fresh weight determinations. They were placed in a forced air drying oven at 65 C for one week. The clipping samples were again weighed for dry weight and were stored for analyses. VI. Sod strength. Sod strength is a physical measurement which relates well to the development of roots and rhizomes. The more roots and rhizomes present, the greater the sod strength. An apparatus was developed at Michigan State University to measure sod strength (31). The preparation of a 17 sample involves cutting a strip of sod (16 inches wide) with a sod cutter. The sod strip is then cut into three-foot lengths. The apparatus is composed of a stationary and a movable platform, each 18 inches in length. There are hinged tops for each platform which can be clamped to the bottom part. The sod piece is laid across the platforms and clamped down with the hinged tops to prevent slippage. Once the sod piece is secured in place, the movable platform is pulled with a uniformly increasing force until the sod tears apart. The force required to tear the sod is measured by inserting a spring scale (capacity 0 to 200 pounds) between the movable platform and a wench. The sod strength is measured by recording the highest value reached on the scale before tearing occurs. The sod is all cut to the same depth, approximately three-fourths inch. Three sod pieces were tested for each plot. The sod strength measurements were performed on July 22, 1970 and October 15, 1970. The sod strip was cut along the south end of the plots for the first measurement and along the north end for the second measurement. VII. Rhizome weight and length. Samples were taken for rhizome measurements immediately following sod strength determinations on July 22. Samples were obtained with a 4 l/4-inch diameter golf course cupcutter. The depth of the plug was sufficient to remove all rhizomes. Three plugs were taken from each plot a short distance from the sod pieces used for sod strength measurements. To facilitate separation of the rhizomes, a water hose was used to remove most of the soil from each plug. The rhizomes, which are larger 18 and whiter than the roots, were removed, dried in an oven at 40 C and weighed. The dry rhizomes were measured by stretching each rhizome along a ruler and recording its length. Laboratory Analyses I. Nitrate analyses of soil samples. The stored soil samples were removed within 48 hours after field sampling for extraction. The soil sample was mixed as thoroughly as possible in the plastic bag. A subsample of 25 to 35 gm was taken for moisture determination. The subsample was placed in a moisture can and weighed. The can and subsample were placed in a drying oven at 60 C for two days. The subsample was again weighed and all the weights recorded. Two subsamples of between 5 and 10 gm were taken for nitrate analyses. Each subsample was placed in a 125 ml Erlenmeyer flask and 50 ml of saturated calcium sulfate solution was added. These were shaken on a rotary shaker at 200 rpm for 30 minutes. The mixture was filtered through No. 3 Qualitative Whatman filter paper. The extract was collected in 2 oz round glass bottles. These bottles of extractant were returned to the cold room for storage until nitrate analysis could be made. An attempt was made to keep the storage period at a minimum. Two nitrate analyses were made on each subsample. Nitrate deter- minations were made using the procedure by Lowe and Hamilton (20) as automated by B. G. Ellis. The nitrate analyses required that the enzyme, nitrate reductase, reduce nitrate to nitrite which can be deter- mined colorimetically. l9 Nitrate reductase is found in the bacteroids of soybean nodules. Soybean nodules were harvested from soybeans grown in the greenhouse and later from soybeans in the field. The nodules are removed from the soy— beans and washed. Washing to clean and remove all soil particles was done using cold distilled water. The nodules were blotted dry with cheesecloth and ground with a cold mortar and pestle in K-succinate (0-1 M) buffer (5 mls per gram of nodules). For more complete grinding a Waring blender was later used to grind the nodules. The slurry was squeezed through four layers of cheesecloth. The liquid was centrifuged at 5,000 G for five minutes or more. The red- colored supernatant was discarded. The solid portion was resuspended in the same amount of K-succinate buffer and recentrifuged. This was repeated until all the red color disappeared. The last resuspended solution was frozen. The greatest difficulty was to ascertain the activity for nitrate reductase. Use of standard solutions on each series of analyses not only provided the standard curve but insured nitrate reductase activity. It was found that repeated refreezing of bacteroid suspension was limited to one or two times before activity was lost. The frozen life of nitrate reductase was limited to one or two months without loss of activity. As the summer proceeded, soil nitrates increased so smaller soil subsamples were used to reduce the need for dilution of the extractant. Potassium nitrate was used as the source of nitrate for the standard solutions. The standard curve ranged from 0 to 4.0 ppm nitrate nitrogen. After color was developed, percent transmission was measured on a colorimeter. The following formula was used in calculating ppm nitrate nitrogen in the extract: 20 ppm NO3-N = (1:)19g %A + log %X) (Conc B - Conc A) (log %B - log %A) where A and B are results for 0 and 4 ppm standard sOlutions. Correction was made for percent moisture and the number of grams used in the sub- samples using the formula: ppm NO3-N/gm soil = (50) (gms dry soil+l) (ppm NO3-N) (gms wet soil - gms dry soil+l) (Wt subsample) The value 50 represents the 50 ml of saturated calcium sulfate used in extraction. II. Total nitrogen analyses of the clippings. Because of the large number of clipping samples only the first five treatments for all clipping dates were analyzed. A modified semi~micro Kjeldahl method (6) was used. Those samples larger than 20 gm were mixed and subdivided until the subsamples were between 10 and 20 gm. All samples and subsamples were ground in a Wiley Mill to pass a 40—mesh screen. Approximately two hundredths of a gm of plant material was weighed for each sample and placed in a micro-Kjeldahl flask. Two ml of dis- tilled water were added and the mixture was allowed to stand for 30 minutes. For digestion of the sample, two tenths of a gm of potassium sulfate—catalyst mixture and two ml of concentrated sulfuric acid were added. This was heated cautiously on a digestion stand until frothing stapped and water was removed. It was sometimes necessary to use hydrogen peroxide to wash particles down the sides of the Kjeldahl flask during digestion. The samples were then steam distilled on a distillation apparatus. The distillant was caught in a 50 ml Erlenmeyer flask containing 5 ml of 21 boric acid-indicator solution. Approximately 15 ml of distillant was caught in 3 to 5 minutes. This was titrated against a standardized solution of sulfuric acid until the first gray color appeared. The following equation was used to calculate the percent nitrogen: % N = (T-B) (N) (l400)/S Where T is ml of acid used for titrating the sample, B is ml of acid used in titrating the blank, N is the normality of the sulfuric acid, and S is the sample weight in mg. III. Total nitrogen analysis of the soil. Total nitrogen is usually of little value in determining nitrogen availability to plants. Therefore, soil samples from the first five treatments were run for four selected dates. It was decided that if there was any useful information in the total nitrogen analysis of the soil it would appear in these samples. The procedure of analysis was similar to that used for the clippings except approximately one-tenth of a gm of soil was used. Greenhouse Rerooting Experiment In an effort to determine the effect of nitrogen treatment on re- rooting of sod, a rooting study was done in the greenhouse. When the October 15 sod strength measurements were made, a 4 l/4-inch plug was taken from each piece of sod (3/4 inch depth). These were transplanted in one-quart cottage cheese containers located in the greenhouse. A loamy sand soil was screened and fertilized to add one pound nitrogen and four pounds each of K O and P20 per 1000 square feet with 2 5 6—24—24. Eleven hundred gm of the fertilized soil was placed in each 22 container. Two hundred ml of distilled water was added to each pot. The plugs were placed in firm contact with the moistened soil and another 100 ml of distilled water was added immediately afterwards. At each watering all pots were brought up to a standard weight to reduce vari- ability in watering. Each pot was clipped on November 3 and November 20. Clippings were dried in a forced air oven (65 C) and weighed. The experiment was treated for powdery mildew November 3 with sulfur. The experiment was terminated November 23, 1970. The sod plugs were removed and all the original sod was separated from the underlying soil with scissors. The roots were removed from the soil by washing over a 4-mesh screen. The roots were removed from the screen with tweezers and placed in coin envelopes. They were dried in a drying oven (40 C) and weighed. Statistical Methods An analysis of variance was compiled on each date for all data and each treatment for all dates. If the F test for treatment means was significant, then the least significant difference was examined at the 5% level (40). Units of Measure The units of measure are expressed in the English system except for very small values which are stated in the metric system. The English system is used for easy interpretation by those involved in sod produc- tion. The following can be used for converting metric units to the English system: pounds = grams x (l/453.59) inches - centimeters x (l/2.54) RESULTS AND DISCUSSION I. Nitrate soil test. The results of the nitrate soil tests are presented in Table 2 and summarized in Figures 1, 2, and 3. The data for Treatments 1 through 4 are represented graphically in Figure 1. Treatment 1 did not receive any nitrogen fertilizer for the entire experiment and is referred to as the check. The nitrate level of the check, in general, increased during the season. The lowest was on May 14, being 4.4 ppm nitrate nitrogen in the soil, and the highest on October 27 with 36.6 ppm. The increase in nitrates during the season for the check is probably due to nitrogen release from the soil by microbial activity, nitrogen additions by rainfall, and the decomposi- tion of clippings returned by mowing. Treatment 2 (30 pounds nitrogen per acre per month) varied little from the check being significantly higher on only two dates. Treatment 3 (60 pounds nitrogen per month) did vary from the check with the largest increases occurring one week after fertilizer application. The nitrate levels for Treatment 3 approached those of the check at three weeks after fertilization. The increase of nitrates following fertilizer application in Treatment 3 was greater after each subsequent fertilizer application. Treatment 4 (120 pounds nitrogen per month) was highly erratic with sharp increases in nitrates following fertilizer applica- tion and steep declines before the next fertilization, but values were 23 24 Hmopm N. anHmnm :Hnuommo H5 moHH» bee. Ndmnmmm om w HmeHomnHoom ow mono moo nnmmnamon. HummnBoSH Zo. bWNI—J oouoxm Ho HH HM Hm H» Hm Hm Hmo. .om Umnm om mmabpwom VIN» mIHH N¢.N w~.m mu.» Mum.m mlmb > x I S l ’ uIIIlIII. a \, \ x N” ~oc N” F. G 0 R T m 2:. 03 7 N” m: M" P. P. ~m U>Hm > on o. we. mo. mom HMO cocoon oHnHommb won mono. Hmmvmnnwdmwx. >Hnozm Hnmwnmnm mono om mmnnHHHnmn mvaHomnHon. 26 always significantly higher than the check. The nitrate nitrogen levels for Treatment 4 generally increased during the season as with other treatments. It is apparent that there are large losses of nitrates in the heavily-fertilized plots. These losses cannot be specifically deter- mined by this study but may be due to leaching, immobilization, or gaseous loss of nitrogen. Treatments 5 through 8 received 15 pounds of nitrogen per month after the initial seedbed application. There were only small differ- ences between these treatments and the check. Treatments 9 through 12 received 30 pounds nitrogen per month for the first three fertilizer applications, then on August 4 the treatments were changed to 0, 30, 60, and 120 pounds of nitrogen, respectively. Figure 2 presents the data in graphic form for these treatments. The differences between these treatments were small and similar to nitrate levels for Treatment 2 until the change in fertilization rates. Immedi— ately following the August 4 applications there was a significant increase in the nitrate level of Treatment 12, while Treatments 9, 10, and 11 varied little. Treatment 12 remained significantly higher for the rest of the season. The September 30 application of nitrogen pro- duced another sharp increase in nitrate levels in Treatment 12 as was observed with Treatment 4, but not of the same magnitude. Nitrate levels for Treatment 11 also increased significantly following the September 30 fertilizer application, while differences between Treatments 9 and 10 remained nonsignificant. Treatments 13 through 16 are summarized in Figure 3. They received 30 pounds of nitrogen fertilizer per month for the first two applications in 1970, then on June 30 they were changed to 0, 30, 60, and 120 pounds 27 2:. r II . II o .L I ......... do \/ 0 x / c. IIIIIII I _. x / x / x / N IIIII S x / |.. . x / :3 l x / N” xx / L. x / G xx / O x / R xx / _.I I. xx // N" :3 r x / 3 x 0 x N v \\// \ \\\\\\\ \\ / x \\\\\\\\\\\\\\\ M “O I \ //x_\ \\\\\\\.\.\.\. . .|.IuII. .\\.\.. . \\ P \\ AJ\.H?\I\L\. [PL . .ulll‘ r r _1 r 1L . m\. «\d w\. m\_ w\_ _o\; U>4m wwmcum N. >Hno£m Hbmfiomno mono om moaneweumfl mwuHHnmnHon. How mHHmn nrwmm mvvaomnHoSm ammo uo coaumm anHommn won mono mow MPH nnmmnaoanm man now whom «to ammo o. mo. ac. moo Hno cocoon Dunnommn won mono. Homumnnedmwx. 28 II. In. .w I. I ........ .g 0 Q. NCO .I lllllllll ._m \/ N” x / ..I \ / IIIII .m x / “N xx / G \ / 0 xx / \ R \ x T xx .. 2:. u \ \ / N" x \\x / x\ \\ 0 mo \\\// \ \\\\\\\\ ......... N . \ /,\ \\.\.......‘..-...... ..- 1 P . b» b w L _ m\_ a\_ u\; a\_ m\_ _c\. Ulpa.m mwmcnm w. >nnoam Humeomnm nHBm om mmHnHHHNmH mvvanmnwoo. How mHHmn nso ovuwwomnwosm SmHm mo possum :HnHommo won mono mom mHH nnmmnamsnm woo woo Hmmn nerm swam 0. mo. mo. moo HNo voodoo anHomoo won mono. Homvmnnp> 027:..40 Imumu m>_._.<...:2:uu< .A%Ho>wuooommu .hHSusoB wofiaoom ouom Hoe ammonuan monsoo ma can .ONH .ow .om .oV m awaousu H muamaummua you munwfios wGHoAHHo ammum m>aumasaauo< .¢ ouamfim 36 benefitted growth by producing 6373 pounds of fresh clippings per acre. Treatment 2 produced a significant increase over the check and Treat- ment 5 with more than four tons per acre of fresh clippings. The yields for Treatments 3 and 4 increased significantly as well with production of about 11 and 18 tons per acre, respectively. Treatments 2, 3, 4, and 5 exhibited very apparent plateaus beginning late July. The check also had this plateau but it is not as obvious because of the very small increases that it had both before and after the plateau. This leveling off of growth occurred during the hottest and driest part of the season which resulted in environmental stress upon the turfgrass plants. Although the plots were irrigated as deemed necessary to prevent wilt, the stress condition cannot be attributed to either moisture or high temperature stress alone. It is interesting to note that the length of time of the depressed growth was shorter for the higher nitrogen rates. Apparently nitrogen increased the rate of recovery of the turf from the stress condition. There were no significant differences between clipping weights for Treatments 5 through 8 (Table 4) indicating there was no residual influence of the fall nitrogen applications on growth the following season. This supports the soil nitrate observations. This small amount of nitrogen fertilizer (15 pounds per month) did stimulate substantial growth over the check. There is an obvious plateau in growth during the environmental stress period of late July and August as occurred with other treatments. Growth resumed shortly after the stress period, although the rate of recovery was slow. Total production of fresh material was more than 3 tons per acre for each treatment. Clipping weights for Treatments 9 through 12 are presented in Table 5 and Figure 5. Early in the season there were significant 37 12 10 P Figure 5 8|- “ 11 m 1’ c2 41", -< I’./’ 5 ' 10 m / m / 0- f "’ ' 9 Z 4- p’d’ /_—' O I’ |- ’z :5 :r: 2" 0 E 1 3: I I I I I I 9 6/1 7/1 &/1 9/1 10/1 11/1 0. //" 1' Figure6 / "" / U / 15 8- / i / “‘ / c: L“ l 14 6- / u: > I F I < ’- ,_ —‘ .- 3 4 14—‘13 E! [I !‘J”p"'—r 3 / A U L, 2 < n / 1 , - I, I I I I, I 6/1 7/1 3/1 9/1 10/1 11/1 [JA'IE Figures 5 and 6. Accumulative fresh clipping weights for Treatments 9 through 12 and Treatments 13 through 16, respectively. 38 differences in clipping weights due to the fall topdressing treatments but these differences disappeared after May. In June the increases in growth were about the same for all treatments until mid-August. Clipping weights for Treatment 9 diminished during the stress period and top growth did not resume except for a small increase in mid- September. Clipping weights for Treatment 10 which were slightly above Treatment 11 prior to the stress period dropped below the growth rate of the latter following the resumption of growth. Treatment 11 resumed ‘growth shortly before Treatment 10 and sustained growth at a more rapid rate to the end of the season. The resumption of growth occurred most rapidly with Treatment 12. Its rate of growth was greater than the others with a total production of more than 10 tons of fresh material per acre. Data for Treatments 13 through 16 are presented in Table 6 and Figure 6. These treatments were changed June 30. Growth for Treatment 13 leveled off prior to the stress period in late July and had only a slight increase in growth in mid-September. Total production of fresh material was less than Treatment 9 because it did not receive the June 30 application of nitrogen. The growth rates for these four treatments are similar until July 1 except for Treatment 13 which was lower. There is no difference in growth observed between Treatments l4 and 15 before the stress period, then was slowed by the environmental stress. Following the stress period there was an unequal resumption of growth. Unlike the previous treatments the highest rate of nitrogen did not cause growth recovery first. Treatment 15 was the first to resume growth while Treatment 16, which had assumed rapid growth prior to the stress period was slow to regain this growth rate. This delay may be due to physiological changes that occurred during rapid growth prior to 39 the environmental stress period. The growth was less than for Treat- ment 12 which received less nitrogen. Although Treatments 13 through 16 received changed nitrogen applications one month before Treatments 9 through 12, soil nitrate tests and clipping results do not reflect these changes as rapidly as would be expected (See Figures 3 and 6). The amount of clipping weights is a direct result of the amount of nitrogen applied. The check plot which did not receive nitrogen had the lowest production of clippings. But Treatments 5 through 8 which had a total of 75 pounds nitrogen fertilizer per acre in five applications did not produce more clippings than Treatment 13 which had a total of 60 pounds nitrogen per acre in two applications early in the season. Those treatments receiving more than one half of their total nitrogen fer- tilizer after late July did not produce as many clippings as those plots receiving a more equal distribution of their nitrogen fertilizer. This occurred, most likely, as a result of the reduced growth rate for all treatments during the stress period. Treatment 4 which received a total of 600 pounds of nitrogen, the highest rate, produced the most clippings. III. Sod strengths. The results of the sod strength measurements on July 22 and October 15 are given in Table 7 and summarized in Figures 7 and 8. The sod strengths on July 22 for the first four treatments show a signifi- cant increase in sod strength by increasing nitrogen from none to 30 pounds per acre per month. The check had a sod strength of 109 pounds, while Treatment 2 was 123 pounds. Treatment 3 decreased sod strength significantly compared to Treatment 2 and was about equal to the check. Treatment 4, the high nitrogen treatment, significantly decreased the sod 40 amopm up meHm oommudmnwoum 0: won mnnmnmnwm moo moon mom Hrpnosm smHmrnm om zmHHoS Nonn:nww owcmmnmmm macaw mos mom on mocmrnos snow. HummnamSn 20. mod mnHosmn: wrwnoam» Hmomns erNoBm» Smwmon wwHNoBm Smemrn VINN HOIHm wrwnoam Hoomn: CE 33 A95 33 H wow wow m~.m oo.o H.mum N HNw Hwo mN.N HHo.m H.pmu w How mu wo.u b~.u H.wo b am mu Hm.u Hw.m H.0u u Ham Hmm mw.H we.» H.mm m Hmm Hmm mm.m HHN.© H.om u Ham Hmo mo.o Hmo.o H.0m m Hwo HVH mm.o Hmo.m H.0m e Hug ppm NO.» Hmm.> H.mo Ho HNm Hum mw.H H>~.o H.u~ HH way How mu.» mN.N H.mm Hm HHo Hwo Nu.~ wo.w H.bb Hw Hwy Ham Hbm.m NNH.N H.mw H» me HHu pm.o ow.w H.9m Hm Hum ow mp.» Hob.~ H.uu Hm Hmm Hp» mm.o mm.m H.mb Hmo A.omv m.m HH.m w~.w mm.m sucwx MN oommnom How mothmcm owsowuwouuomom .moumw wouomHom Hoom so .m oHnma 53 Table 10, Percent nitrogen of Houghton muck for four selected dates. Date of Sampling Treatment No. 4-24 7-6 8-11 10-7 1 2.8 2.9 2.8 2.8 2 2.8 2.9 2.8 2.8 3 2.8 2.9 2.8 2.8 4 2.9 3.0 2.8 2.9 5 2.0 2.9 2.7 2.7 lsd .05 ns ns ns ns There are no differences in nitrogen content, ranging from 2.7 to 3.0 percent with no variation due to treatment of date of sampling. These results would be expected for a reed-sedge peat. VII. Greenhouse rooting study. The results of the rerooting study in the greenhouse are given in Table 10 and summarized in Figure 13. Sod plugs were transplanted on October 16, 1960 and grown for 37 days. There was no difference in root production between Treatments 1, 5, and 2 (0, 15, and 30 pounds nitrogen per month, respectively). Increasing the nitrogen to 60 or 120 pounds (Treatments 3 and 4) caused significant reductions in roots, however, The results of Treatments 5 through 8 Show no significant differences with only small, nonsignificant increases over the check. Root production was also significantly decreased by the higher nitrogen applications on Treatments 11 and 12 compared to 9 and 10. In Treatments 13 through 16, 13 was significantly higher in root pro- duction than all other treatments, while Treatments 14, 15, and 16 had low root production. Again, this points out that Treatment 14 was not comparable to other treatments receiving the same nitrogen fertilization program. Although correlation data were not determined, the root 54 L l L j11 L 1'2 L 13] L 14 hs E he 20 40 6b I0 100 120 Figure 13. MG ROOTg/POT Roots produced by 4 1/4 inch plug of sod in 37 days in the greenhouse on a sandy loam soil. 55 production increases related rather well to increases in sod strengths taken in October just prior to the start of the greenhouse study. Table 11. Root and clipping weights from the greenhouse rooting study, averages for three replications."' ‘ " " ’ " ‘> Treatment No. Roots Greenhouse clippings (mg) (mg) (mg) 1 70.1 340 515 2 73.0 774 674 3 22.1 846 557 4 28.3 711 490 5 77.6 601 550 6 87.2 607 573 7 92.3 722 659 8 77.0 664 561 9 82.9 579 554 10 73.0 799 611 11 43.2 910 669 12 43.3 905 522 13 121.7 633 580 14 52.6 790 600 15 46.2 742 598 16 38.6 716 614 __l§d .05 25.1 66 55 The greenhouse clipping results were somewhat consistent with clip- ping weights in the field studies. In general, those treatments receiving higher nitrogen applications produced significantly more top growth on the first clipping date. The clippings were reduced for those treatments which received the highest nitrogen rate (120 pounds nitrogen per month) compared to other treatments. On the second clipping date this trend was even more marked. Those treatments receiving the inter- mediate nitrogen rates prior to the greenhouse study had increased 56 clipping weights relative to the higher nitrogen treatments. Those treatments that had received high rates of nitrogen were spending most of their energy in the production of shoots while the lower nitrogen rates enhanced rerooting of the turf. SUMMARY The principal objective of this study was to aid the sod grower in determining the nitrogen fertilizer need for rapidly producing a high quality sod on organic soils. Ammonium nitrate was applied at different levels and dates. These treatments were evaluated using sod strength, rhizome length and weight, clipping weights, and rerooting ability. Nitrate nitrogen level in the soil and nitrogen content of the clippings were determined to examine their usefulness as adequate means for pre- dicting nitrogen needs for sod. I. Nitrate soil test. The results of the nitrate soil tests indicated that this is not an effective tool for predicting nitrogenfertilizer needs of turf in sod production. There was very little difference in soil nitrate levels between treatments receiving 0, 15, 30, and in some instances 60 pounds nitrogen per acre per month. Although significant differences could be attained with 120 pounds nitrogen per month, the data were quite variable depending on the length of time after application. However, this rate of application would be excessive for practical sod production practices. The data does show that there was a general increase in the nitrate level of the soil during the season. The increases in nitrates were the result of soil decomposition by microbial activity, nitrogen in rainfall, and nitrogen recycled by the return of the clippings. Another important 57 58 observation was the large loss of nitrates from the soil within three weeks after nitrogen was applied at rates of 60 and 120 pounds nitrogen per acre per month. The increase to 60 and 120 pounds of nitrogen per month during the season significantly increased the nitrate level of the soil. This not only increased the nitrate levels but also increased yield of clippings. The study also showed some residual carryover between monthly applica- tions for the 120 pounds nitrogen per acre rate because the nitrate level stayed significantly higher than those treatments receiving lower monthly applications of nitrogen even though marked declines were ob- served. The heavy rate of 120 pounds nitrogen per acre applied in the fall was not detected by the nitrate soil test the following spring. The nitrogen fertilizer that the turfgrass does not use in the fall is lost before growth is resumed the next year. The 15 and 30 pounds nitrogen per acre per month treatments pro- duced the strongest sod. The nitrate soil test is of little value since the nitrate levels in the soil were not consistently different from the check for these treatments. 11. Fresh clipping weights. The data for the fresh clipping weights showed that increased rates of nitrogen application increased the top growth of the turfgrass. The amount of clippings was very small without nitrogen fertilizer with a total of only 1400 pounds per acre produced mostly in the early part of the season. The production of clippings for the 15, 30, 60 and 120 pounds nitrogen per month was approximately 3, 4 1/2, 11, and 18 tons per acre, respectively. 59 The timing of nitrogen fertilization had an important effect on the amount of clippings produced as well as the turfgrass plants' ability to withstand environmental stress. The application of fertilizer early in the season resulted in increased clippings. The even applica— tion of fertilizer throughout the season (Treatment 5) produced less clippings than heavy applications of a similar amount of nitrogen in the early part of the season (Treatment 9). The growth of the turfgrass can be effectively changed by altering the nitrogen fertilization. Increasing the nitrogen applied during the season had the effect of increasing top growth while altering sod development. An increase from 30 to 60 or 120 pounds of nitrogen effectively reduced the sod development. For growth, nitrogen fertilizer must be continuously supplied to the turfgrass and discontinuance re- duces the top growth of the plant while the plant makes effective use of growth materials for root and rhizome development. The increase in nitrogen for Treatment 16 applied just prior to the environmental stress period was more detrimental than a continuous supply of nitrogen even at the highest rate (Treatment 4). Topdressing nitrogen in the fall (October 6) did have an effect on clippings produced the following spring (Treatments 9 through 12) but seedbed applications (August 29) produced no differences in growth (Treatments 5 through 8). This occurred even though soil tests did not show these differences. III. Sod strength. Sod strength measurements showed that the amount of nitrogen sup— plied continuously or a change in amount of nitrogen can effectively alter ’ 60 sod strengths. The treatment which received 15 pounds nitrogen per month consistently had the greatest sod strength and a well developed root and rhizome system. In addition, Treatment 13 which received two 30 pound nitrogen applications in May and June had a sod strength in October equal to that of the lS-pound treatments. Although the difference on July 22 between the check and the 60 pounds nitrogen per month was not significant there was a very important difference in the appearance of the turfgrass. The check was very chlorotic, had slow growth and was subject to weed invasion while the 60 pounds nitrogen per month treatment was much more acceptable in appearance and had the ability to compete with weeds. Nitrogen generally improved the appearance of the turfgrass. It was evident from October 15 sod strength measurements that this improvement in appearance was at the expense of developing sod strength. The excessive rate of 120 pounds per month had the lowest sod strength on both dates although it appeared to be a high quality turf. The sod strength can be effectively changed by altering the nitro- gen fertilizer rate. In general sod strength can be improved by with- holding nitrogen after the sod is well established which is evident from Treatment 13. Increasing the nitrogen decreased sod strength once turf was established as shown by Treatments ll, 12, 15 and 16. However, it does take some time to effectively change the sod strength because Treatments 13 through 16 did not show any differences on July 22, three weeks after nitrogen rates were changed. III. Length and weight of rhizomes. Nitrogen efffects rhizome development as well as sod strength. Rhizomes aid in holding the sod together. Generally, the higher nitrogen 61 treatments resulted in lower rhizome production (both length and weight) although some nitrogen was apparently needed for optimum rhizome growth. This was evidenced by the larger rhizome values for Treatment 2 (30 pounds nitrogen per month) compared to the check. An interesting exception to this observation was the greater rhizome growth for Treat- ment 8 compared to Treatment 5. Both received 15 pounds nitrogen per month during 1970 but differed in the higher rate of seedbed nitrogen for Treatment 8. Timing of nitrogen application also significantly affects rhizome growth as suggested by the extremely high rhizome production by Treat- ment 13 compared to Treatments 10 or 14. IV. Nitrogen content of the clippings. The percent nitrogen in the clippings indicated that treatments receiving higher nitrogen fertilizer resulted in more nitrogen in the plant as would be expected. The results also showed that the amount of nitrogen in the soil which is available to the plant decreased from the time of one application to the next. This was reflected in both soil nitrate tests and nitrogen in the clippings. The nitrogen content in clippings for the check increased during the season, supporting the soil nitrate test observations. The variability in nitrogen content during the season and in response to fertilization may be significant. The nitrogen content of clippings from Treatment 2 (30 pounds nitrogen per month), for example, varied from as low as 2.8 to as high as 4.4%. This extreme occurred between the July 30 and August 6 sampling dates in response to a nitrogen treatment. The ranges were even wider for the higher nitrogen 62 treatments. An increase in frequency of nitrogen application would reduce the differences that occurred within a treatment. V. Total nitrogen in the soil. The results showed that total nitrogen is not an important factor in determining the nitrogen available to the turfgrass plant. There was no difference in total nitrogen of the soil, regardless of season or rate of nitrogen applied. VI. Rerooting study in greenhouse. The results of this study showed that there were differences in the rerooting ability of the sod depending on previous nitrogen fertilizer application. There was little difference between the low nitrogen rates but those treatments receiving 60 and 120 pounds of nitrogen per month significantly reduced rerooting ability of the turfgrass plant. The longer these high rates were applied the slower the rerooting ability of the plant. Obviously the nitrogen fertilization program on the sod farm has a significant effect on the ability of the sod to reestablish on the new site. CONCLUSIONS 1. The use of the nitrate soil test for predicting the nitrogen needs of the turfgrass plant for sod is not yet practical. It is impossible to determine differences in nitrate levels between no nitro- gen and low rates applied. This is especially true for the relatively low nitrogen rates which can be practically used by the sod grower. The results for higher nitrogen applications are widely variable and of no use to the sod producer. It is apparent that loss of nitrates from the soil and additions of nitrogen to the soil complicate the use of the nitrate soil test. 2. The clipping weights showed that there was an increase in top growth with increased nitrogen fertilizer. It was evident that nitrogen treatment had an influence on the ability of the turfgrass plant to recover from environmental stress. The addition of increased nitrogen prior to the stress period delayed turf recovery. 3. The application of between 15 and 30 pounds nitrogen per acre per month produced the highest quality sod. The root system developed best under these rates and the ability of the turf to compete with weeds was improved over the check. Although the sod did not have as attractive an appearance as higher nitrogen treatments, it was stronger and had more rhizomes. Sod strength and rhizome growth can deteriorate in just a few months with heavy nitrogen applications. 4. In general, the increase in rhizome length and weight corre— sponded to an increase in sod strength. Lower nitrogen rates tended to result in larger rhizomes than higher rates. 63 64 5. Timing of nitrogen application has an influence on sod develop- ment. Discontinuing nitrogen application during summer resulted in a very strong sod. 6. The percent nitrogen in the clippings increased with increasing rates of nitrogen applied. Between applications there was a steady decline on the nitrogen content of the clippings receiving nitrogen. The turfgrass that did not receive any nitrogen showed an increase in nitrogen content as the season progressed which was consistent with soil nitrate test observations. The amount of nitrogen in the clippings varied widely in response to seasonal and fertilization effects. 7. The total nitrogen content of the soil does not provide any useful information concerning the nitrogen-supplying power of the soil.. There were no differences in the total nitrogen content of the soil due to nitrogen applications. 8. The rerooting ability of the turfgrass plant depended on pre- vious nitrogen applied. The high rates of nitrogen produced less roots than the check or lower rates. Discontinuing nitrogen applications for one to two months prior to sodding may improve the rerooting ability of the sod. 10. ll. 12. 13. LIST OF REFERENCES Alexander, M. 1967. Introduction to Soil Microbiology. John Wiley & Sons, Inc. pp. 248-292. Avnimelech, Yoram. 1971. Nitrate transformation in peat. Soil Sci. 111:113-118. Beard, J. B. and P. E. Rieke. 1969. Turfgrass Science. Amer. Soc. Agron. Agronomy Monograph No. 14. pp. 442-461. Beard, J. B., P. E. Rieke, and J. W. King. 1969. Sod production of Kentucky bluegrass. Proc. lst Inter. Turf Res. Conf. pp. 509-513. Bosemark, Nils Olof. 1954. The influence of nitrogen in root development. Physiol. Plantarum. 7:497-501. Bremner, J. M. 1964. Methods of Soil Analysis. Amer. Soc. Agron. Monograph No. 9. Academic Press, New York. pp. 1215-1216 and pp. 1171-1175. Broadbent, F. E. and B. R. Stojanovic. 1952. The effect of partial pressure of oxygen on some soil nitrogen transforma- tions. Soil Sci. Soc. Amer. Proc. 16:359-363. Buckman, H. O. and N. C. Brady. 1960. The Nature and Properties of Soils. The Macmillan Company, New York. pp. 334-356. Carroll, J. C. 1954. Effects of drought, temperature and nitrogen on turf grasses. Plant Physiol. 18:19-36. Daniel, W. H. 1962. Principles and practices of sod production. Proc. Midwest Reg. Turf Foundation Turf. Conf. pp. 71-73. Davis, J. F. and R. E. Lucas. 1959. Organic Soils (Their Formation, Distribution, Utilization and Management). Mich. State Agric. Exp. Sta. Special Bull. 425. Dawson, J. E. 1936. Organic Soils. Advances in Agron. Vol. VIII. Amer. Soc. Agron. Academic Press, Inc., Pub. New York. Dotzenko, A. D. 1961. Effect of different nitrogen levels on the yield, total nitrogen content, and nitrogen recovery of six grasses grown under irrigation. Agron. J. 53:131-133. 65 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 66 Dunn, J. H. and R. E. Engel. 1970. Rooting ability of Merion Kentucky bluegrass sod grown on mineral and muck soil. Agron. J. 62:517-520. Grable, A. R. and D. D. Johnson. 1960. Efficiency of recovery of applied nitrate nitrogen by perennial ryegrass from different soils. Soil Sci. Soc. Amer. Proc. 24:503-507. Harrison, C. M. 1934. Response of Kentucky bluegrass to variation in temperature, light, cutting and fertilizing. Plant Physiol. 9:83-106. Juska, F. V. and A. A. Hanson. 1967. Effect of nitrogen sources, rates, and time of application on the performance of Kentucky bluegrass turf. Amer. Soc. Hort. Sci. 90:413-419. King, J. W. and J. B. Beard. 1967. Soil and management factors affecting the rooting capability of organic and mineral grown sod. Amer. Soc. Agron. Abstr. p. 53. Kurtz, K. W. 1967. Effect of nitrogen fertilization on the establishment, density, and strength of Merion Kentucky bluegrass sod grown on a mineral soil. Thesis for M.S. degree at Western Mich. Univ. Lowe, R. H. and J. L. Hamilton. 1967. Rapid method for deter- mination of nitrate in plant and soil extracts. J. Food Chem. 15:359-361. Madison, J. H. 1962. Turfgrass Ecology. Effects of mowing, irrigation, and nitrogen treatments of Agrostis palustris Huds., Seaside and Agrostis tenuis Sibth., "Highland" on population, yield, rooting, and cover. Agron. J. 54:407-412. McLean, E. 0. 1957. Plant growth and uptake of nutrients as influenced by levels of nitrogen. Soil Sci. Soc. Amer. Proc. 21:219-222. Michigan Agricultural Statistics. July 1971. Michigan Department of Agriculture. Miller, C. E., L. M. Turk, and H. D. Foth. 1965. Fundamentals of Soil Science. John Wiley & Sons, Inc. pp. 201-203. Mortimer, G. B. and H. L. Ahlgren. 1936. Influence of fertiliza- tion, irrigation, and stage and height of cutting on yield and composition of Kentucky bluegrass (Poa pratensis L.). J. Amer. Soc. Agron. 28:515-533. Musser, H. B. and J. M. Duich. 1958. Response of creeping bent- grass putting green to urea-form compounds and other nitrogenous fertilizers. Agron. J. 50:881-884. Oswalt, D. L., A. R. Bertand, and M. R. Teel. 1959. Influence of nitrogen fertilization and clipping on grass roots. Soil Sci. Soc. Amer. Proc. 23:228-230. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 67 Pellet, H. M. and E. C. Roberts. 1963. Effects of mineral nutri- tion on high temperature induced growth retardation of Kentucky bluegrass. Agron. J. 55:473-476. Puustjarvi, V. 1970. Mobilization of nitrogen in peat culture. Peat and Plant News 3:35-42. Ramage, C. H., C. Eby, R. E. Mather, and E. R. Purvis. 1958. Yield and chemical composition of grasses fertilized heavily with nitrogen. Agron. J. 50:59-62. Rieke, P. E. 1968. A technique to measure sod strength for use in sod production studies. Amer. Soc. Agron. Abstr., p. 60. Rieke, P. E. and J. B. Beard. 1969. Factors in sod production of Kentucky bluegrass. Proc. lst Inter. Turf. Conf., pp. 514-521. Rieke, P. E., J. B. Beard, and R. E. Lucas. 1968. Grass sod pro- duction on organic soils in Michigan. 3rd Inter. Peat Cong. pp. 350-354. Rieke, P. E. and R. E. Lucas. 1967. Sod for turf. Weeds, Trees, and Turf 6(10:14-17). Roberts. E. C. 1966. Nitrogen-growth relationships in turfgrass. Amer. Soc. Agron. Abstr., p. 36. Satari, Achmad M. 1967. Effects of various rates and combinations of nitrogen, phosphorus, potassium and cutting heights on the development of rhizome, root, total available carbohydrate and foliage composition of Poa pratensis L. Merion grown on Houghton muck. Thesis for Ph.D. Michigan State University. Scarsbrook, C. E. 1970. Regression of nitrogen uptake on nitrogen added from four sources applied to grass. Agron. J. 62: 618-620. Schmidt, R. E. 1967. Growing a vigorous, strong, root system on cool season turfgrass. Weeds, Trees, and Turf 6(7:22—23). Schmidt, R. E. 1969. Nitrogen nutrition of turfgrasses. Proc. lst Inter. Turf Res. Conf. pp. 191-195. Steel, R. G. and J. H. Torrie. 1960. Principles and procedures of Statistics. McGraw-Hill Book Company, Inc. Stuckey, Irene H. 1941. Seasonal growth of grass roots. Amer. Tisdale, S. L. and W. L. Nelson. 1966. Soil Fertility and Fertilizers. The Macmillan Company, New York. 2nd Ed. Troughton, Arthur. 1957. The underground organs of herbage grasses. Commonwealth Bureau of Pastures and Field Crops, Hurley, Berkshire Bull. 44. 44. 45. 46. 47. 48. 68 Volk, G. M. and G. C. Horn. 1965. Response of Tifgreen bermuda- grass to soluble and slowly available nitrogen sources as measured by visual ratings and turf weights. Proc. Univ. Fla. Turf Management Conf. 13:147-152. Walker, T. M., A. F. Adams, and H. D. Orchiston. 1956. Fate of labeled nitrate and ammonium nitrogen when applied to grass and clover grown separately and together. Soil Sci. 81: 339-351. Ward, C. H. and R. E. Blaser. 1961. Effect of nitrogen fertilizer on emergence and seedling growth of forage plants and subse- quent production. Agron. J. 53:115-120. Wolcott, A. R., F. Maciak, L. N. Shepherd, and R. E. Lucas. 1960. Effects of telone on nitrogen transformations and on growth of celery in organic soil. Down to Earth (summer) pp. 1-5. Wyler, J. and C. C. Delwiche. 1954. Investigations on the de- nitrifying process in soils. Plant and Soil 5:155-169. APPENDIX 69 Table 12. Accumulative dry clipping weights, pounds per acre, Treatments 1 through 8. Treatment No. Dagg 1 2 3 4 5 6 7 8 5-18 101 342 715 934 316 376 398 411 5-23 158 506 1091 1402 486 581 600 602 5-26 200 602 1253 1645 603 718 707 714 5-28 215 638 1328 1743 644 771 754 758 6-4 251 736 1531 2119 733 955 856 864 6-9 270 818 1693 2380 813 1045 941 941 6-11 284 869 1797 2516 853 1094 988 983 6-16 298 1000 2035 2792 921 1183 1070 1048 6-19 307 1059 2155 2985 956 1238 1109 1079 6-22 314 1130 2285 3167 990 1296 1143 1110 6-25 323 1176 2390 3297 1015 1333 1174 1135 6-29 331 1221 2489 3466 1043 1373 1203 1158 7-2 334 1262 2593 3625 1063 1404 1224 1182 7-6 337 1322 2772 3856 1093 1454 1261 1214 7-9 339 1363 2877 4033 1109 1478 1281 1231 7-13 344 1435 3043 4315 1146 1526 1320 1264 7-16 349 1481 3152 4506 1180 1563 1351 1290 7-21 353 1537 3259 4718 1204 1589 1376 1314 7-25 357 1570 3342 4894 1222 1610 1395 1333 7-30 357 1573 3361 4966 1223 1611 1395 1334 8-6 357 1578 3396 5065 1224 1612 1396 1334 8-13 358 1592 3517 5262 1226 1613 1398 1336 8-20 358 1617 3690 5578 1229 1616 1401 1340 8-26 361 1656 3867 5910 1241 1624 1410 1350 9-1 363 1696 4016 6157 1252 1635 1423 1361 9-4 367 1735 4115 6328 1278 1655 1442 1382 9-8 375 1790 4238 6514 1310 1688 1476 1408 9-11 391 1901 4408 6733 1382 1757 1546 1480 9-16 405 1971 4539 6929 1431 1812 1598 1530 9-21 419 2066 4709 7146 1496 1877 1662 1600 10-1 438 2213 4992 7524 1608 1991 1772 1707 10-6 442 2286 5125 7702 1659 2042 1824 1756 10-15 447 2392 5286 7878 1725 2113 1899 1824 10r27uhu 461 ”.12516 “1.5542 , 8233 1789 2174 1975 1895 1916 ~~11-12~-v~463~~- 2555' "5676‘--~8447" " 1807 2195 1990 jfii‘ fi‘w‘ww‘VYV“ wwwwfiyj 70 Table 13. Accumulative dry clipping weights, pounds per acre, Treatments 9 through 16. Treatment No. Date 9 10 11 12 "" l3 ' ‘14 ' '15 16 5—18 212 527 462 523 337 469 541 513 5-23 371 749 708 852 514 685 834 742 5—26 481 876 841 1046 602 ’ 820 963 888 5—28 524 920 897 1115 641 877 1026 941 6—4 617 1052 1019 1261 760 1007 1170 1065 6-9 725 1164 1120 1377 860 1135 1312 1183 6-11 782 1230 1177 1448 921 1214 1392 1262 6-16 950 1391 1309 1612 1053 1385 1562 1416 6-19 1035 1472 1389 1703 1116 1482 1644 1494 6—22 1115 1556 1463 1783 1177 1581 1738 1590 6—25 1168 1622 1509 1834 1238 1642 1793 1643 6-29 1227 1689 1566 1895 1295 1708 1853 1705 7-2 1286 1745 1615 1946 1340 3763 1905 1759 7-6 1386 1850 1688 2081 1395 1856 1997 1897 7—9 1448 1913 1742 2163 1434 1912 2099 1977 7-13 1557 2041 1828 2235 1486 2003 2199 2126 7-16 1637 2111 1895 2294 1521 2074 2271 2236 7-21 1705 2160 1951 2335 1550 2137 2334 2329 7-25 1755 2200 1992 2376 1577 2183 2381 2402 7-30 1759 2203 1996 2379 1578 2185 2385 2410 8-6 1765 2207 2001 2386 1580 2191 2393 2437 8—13 1770 2221 2043 2483 1582 2209 2443 2573 8-20 1775 2244 2138 2756 1586 2248 2557 2856 8—26 1808 2276 2255 3086 1594 2270 2717 3159 9-1 1819 2309 2355 3318 1607 2314 2835 3359 9-4 1843 2347 2431 3464 1628 2353 2908 3503 9-8 1876 2406 2530 3614 1659 2418 3015 3650 9-11 1944 2506 2675 3812 1720 2519 3169 3830 9-16 1996 2583 2784 3959 1769 2601 3287 3981 9-21 2062 2682 2921 4152 1829 2709 3435 4159 10-1 2170 2840 3145 4456 1922 2882 3679 4459 10-6 2201 2920 3289 4616 1951 2972 3819 4606 10-15 2245 3029 3458 4796 1989 3091 3997 4774 10-27 2295 3162 3670 5050 2053 3207 4230 5049 ‘11-12‘ 2306 ' 3213 3786 5173 2066 3258 4353 5207 ICHIGRN STQTE UNIV. 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