PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES Mum on .or before due due. DATERDIUE' DATE DUE DATE DUE a MSU Is An Affirmative Action/Equal Opportunity Institution THE EFFECT OF TILLBGE SYSTEM ON CORN PRODUCTION AND SOIL PROPERTIES ON A KALANRZOO LOAN BY James Allen Bronson 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 1989 (90014110 ABSTRACT THE EFFECT OF TILLAGE SYSTEM ON CORN PRODUCTION AND SOIL PROPERTIES ON A KALAMAZOO LOAN BY James Allen Bronson The effect of tillage system, dairy manure and irrigation on corn (gga gays L.) grain production and soil properties was studied from 1981-1985 in southwestern Michigan. Soil type was primarily Kalamazoo loam (Fine-loamy, mixed, mesic Typic Hapludalfs) with small areas of 0sthemo sandy loam (Coarse-loamy, mixed, mesic Typic Hapludalfs). Three field sites were utilized providing a total of 11 site-years. Moldboard plowing (P), chisel plowing (CP), no-till (NT), no-till with a rye cover crop (CCNT) and various corn—legume intercrops were studied. In 1985 one of the intercrop treatments was changed to ridge till (RT). Comparable grain yields were produced using NT, P, CP, CCNT as long as plant populations were favorable. RT produced highest yields during 1985. Yield variation within years was common. Legume intercrop trials failed to produce satisfactorily. Significant differences related to tillage were found in soil temperature, seedling emergence rate, soil moisture content, percent ground cover and total carbon content of surface soil, bulk density and pore-size distribution. ACKNOWLEDGEMENTS The author wishes to express his great appreciation to his major professor, Dr. A. Earl Erickson. Dr. Erickson’s guidance and support, relating both to academic and professional pursuits has been invaluable. Special thanks is also given to graduate committee members Drs. B.D. Knezek, F.J. Pierce and J.R. Black. The assistance of Patricia S. Michalak for occasional attitude adjustments and help in editing this manuscript is gratefully acknowledged. Thanks also to present and former members of Dr. Erickson's laboratory staff for help in the processing of many of samples. These include, among others, Micheal Schulz, Bradley Johnson, and Bruce MacKellar. Finally, sincere appreciation is expressed to Harold Webster and the staff of the Kellogg Biological Station’s Dairy Center. Without their cooperation this study could not have taken place. iii TABLE OF CONTENTS LIST OF TABLES................ ..... .......................Vi LIST OF FIGURES.........................................viii LIST OF SPECIES CITED....... ..... ........... ......... ......x LIST OF CHEMICALS CITED...................................xi A. INTRODUCTIONOOOOOOOOOO00.0.00...0......OOOOOOOOOOOOOOO..1 B. LITBMTURB REVIEWOOOOOOOOOOOOO000......OOOOOOOOOOOOOOOO.‘ 1. TILLAGE SYSTEMS a. Introduction...................................4 b. Conservation vs. Conventional Tillage..........5 c. No-tillage..... ...... ..........................6 d. Chisel Plowing.................................7 e. Till P1anting......... ....................... ..7 2. INFLUENCE OF TILLAGE ON SOIL PHYSICAL AND BIOLOGICAL FACTORS a. Plant Productivity.............................8 b. Seedling Emergence and Soil Temperature.......13 c. Soil Physical Properties......................17 i. Pore Size Distribution........ ...... .....18 ii. Bulk Density.. ..... . ................ .....19 iii. Organic Matter Content ................. ..22 iv. Soil Moisture Content .................... 23 Ce EXPERIMENT METHODSOOOOOOOOOOOOO...OOOOOOOOOOO00.00.00.025 1. STUDY SITES AND TREATMENTS...... ............... ....25 2. CULTURAL METHODS................ ...... . ..... .......30 3. DATA COLLECTION a. Soil Temperature..............................40 b. Seedling Emergence............................47 c. Crop Residue and Soil Carbon Measurements.....47 d. Soil Moisture........... ..... .................49 e. Soil Physical Properties......................49 f. Plant Populations and Grain Yields............51 iv D. RESULTS AND DISCUSSION.. ............................... 55 1. 2. 3. 4. 5. 6. 7. SEEDLING EMERGENCE RATE............................55 RESIDUE AND SOIL CARBON...... ............ ..... ..... 62 SOIL TEMPERATURE...................................68 SOIL MOISTURE......................................79 SOIL PHYSICAL PROPERTIES. ............... ...........88 PLANT POPULATIONS.................................102 GRAIN YIELDS.................. .......... ..........106 E. CONCLUSIONBOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO0.0.0.00000012‘ PO BIBLIOGMPHYOOOOOOOOOOOOOOOOOOOOOOOOOOO...00.0.0000000127 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. LIST OF TABLES Tillage System and Treatment Labels/Descriptions.....29 Dates of Primary and Secondary Tillage: Site F90.....31 Dates of Primary and Secondary Tillage: Site F84A....31 Dates of Primary and Secondary Tillage: Site F84B....32 Preplant K20 Fertilizer Applications As 0-0-60.......33 Starter Fertilizer and Insecticide Applications ...... 35 Annual Corn Planting Dates............. .............. 35 Nitrogen Fertilizer Schedule: Site F90...... ....... ..37 Nitrogen Fertilizer Schedule: Site F84A ............ ..38 Nitrogen Fertilizer Schedule: Site F848.... ........ ..39 Irrigation Summary: Total Amounts and Events.........41 Monthly Rainfall and Mean High/Low Temperatures......42 Soil Temperature Measurement Schedule................45 Annual Seedling Emergence Count Schedule...... ..... ..48 Soil Moisture Measurement Schedule.. ............ .....50 Intact Soil Core Sampling Schedule...................52 Grain Harvest SChedule. I O O O O O O I O O O O O O O O O O O O 000000 O O I O 53 Mean Percent Ground Cover: Seven Site-Years ........ ..63 Mean Percent Ground Cover: Site F848, 1985 ........... 63 Soil Carbon: Site F90, April 1986; 0-1 cm Depth......66 Soil Carbon: Site F90, April 1986; 1-5 cm Depth......67 Total Porosity In Intact Soil Cores: 0-7.6 cm........89 vi List of Tables, continued. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. Bulk Density In Intact Soil Cores: 0-7.6 cm.........101 Plant Populations At Harvest: Plant Populations At Harvest: Plant Populations At Harvest: Mean Mean Mean Mean Mean Mean Mean Mean Mean Mean Mean Combined Analysis Of Grain Yields: Site F90...... Grain Grain Grain Grain Grain Grain Grain Grain Grain Grain Grain Yields: Yields: Yields: Yields: Yields: Yields: Yields: Yields: Yields: Yields: Yields: Site Site Site Site Site Site Site Site Site Site Site F90, F90, F84A, F90, F84A, F843, F90, F84A, F848, F90, F848, F848, 1983... ....... ..104 F90, 1983.. ......... ..105 F9D, 1985.............107 1981.. ............... ..108 1982.... ..... ..........110 1982. ..... .... ........ 110 1983.. ................ .111 1983... ..... . ........ .111 1983. ...... ... ........ 112 1984.. ............ .....112 1984..................113 1984.. ............. ...113 1985.. ............ .....115 1985....00.000.000.000115 ...116 Combined Analysis Of Grain Yields: Site F848........1l7 Combined Analysis Of Grain Yields: Site F84A........118 Mean Mean Mean Mean Grain Grain Grain Yields: Yields: Yields: Site F90; Years 1981-1985........121 Site F84A; Years 1982-1984 . . . . . . . 122 Site F848; Years 1983-1985.......122 Grain Yields Combined Over All Years & Sites...123 vii 10. 11. 12. 13. 140 15. 160 17. LIST OF FIGURES Plot layout for site F90............. ...... . ......... 26 Plot layout for both F84 experiments.................27 Emergence Counts For F90 Control Plots -- 1982 ....... 56 Emergence Counts For F848 Control Plots -- 1985 ...... 58 Emergence Counts For F90 Man-Irr Plots -- l982.......60 Emergence Counts For F84A Manure Plots -- 1983.. ..... 61 1983 Mean Daily High Soil Temperature at 5.1 cm -- F90/Manure0000000.0000000000000000.00000000000000000069 1983 Mean Daily High Soil Temperature at 10.2 cm -- F90/Manure ....... 00000000000000000000000000000000000070 1984 Mean Daily High Soil Temperature at 5.1 cm -- F84B/ManureO0000000000000000000000000000000000000000071 1984 Mean Daily High Soil Temperature at 10.2 cm -- F84B/Manure ...... .. ..... .............................72 1983 Mean Daily High Soil Temperature at 5.1 cm -- F90/contr01000000000000000000000000000000000000.0000073 1983 Mean Daily High Soil Temperature at 10.2 cm —- F90/Control................. ......... ........... ..... 74 1984 Mean Daily High Soil Temperature at 5.1 cm -- F90/contr01000000000000000000000000.0000000000000000076 1985 Cumulative Degree-Hours in F848 Control at 501 cm Depth0000000000000000000000000000000000000000077 1985 Cumulative Degree-Hours in F848 Control at 1002 cm Depth00000000000000000000000000000000000...0078 Neutron Probe Readings For F84A Control At 30 cm Depth -- 19830000000000000000000000 ...... 00000000000080 Neutron Probe Readings For F848 Control At 15 cm Depth -- 1985.0...0.000.000.0000...0.0.0.0.000.00.00.81 viii List of Figures, continued. 18. 19. 200 21. 22. 23. 24. 25. 26. 27. 280 29. 30. 31. 32. Neutron Probe Readings For F848 Control At 30 cm Depth -- 1985........................................82 Neutron Probe Readings For F848 Manure at 15 cm Depth -- 1985........................................84 Neutron Probe Readings For F848 Manure at 30 cm Depth -- 1985........................................85 Neutron Probe Readings For F848 Manure at 61 cm Depth -- 1985.................................. ...... 86 Neutron Probe Readings For F848 Manure at 76 cm Depth -- 1985........................................87 F90 Pore Size Distribution -- 1982...................91 F90 Pore Size Distribution -- 1983............ ..... ..92 F90 Pore Size Distribution -- 1984.... ..... ..........93 F90 Pore Size Distribution -- 1985...................94 F84A Pore Size Distribution -— 1982........... ....95 F84A Pore Size Distribution -- 1983. ............... 96 F84A Pore Size Distribution -- 1984........... ....97 F848 Pore Size Distribution -- 1983........... ....98 F848 Pore Size Distribution -- 1984........... ....99 F848 Pore Size Distribution -- 1985........... ...100 ix LIST OF SPECIES CITED Alfalfa Corn Earthworms Fungus Grey garden slug Oats Rye Root Rot Soybeans Soybean cyst nematode Wheat Medicago sativa £23 EEYE Family Lumbricidae Pythium graminicola Subr. Deroceras reticulatum Avena sativa Secale cereale Phytophthora sp. Glycine max Heterodera glycines Triticum aestivium Alachlor Atrazine Cyanazine DyfonateR Carbofuran Chlorpyrifos Glyphosate Paraguat LIST OF CHEMICALS CITED 2-chloro-2’,6’-diethyl-N-(methoxymethyl) acetanilide 2-chloro-4-(ethylamino)-6-(isopropy1amino) -s-triazine 2-chloro-4-(cyclopropylamino)-6- (isopropylamino)-s-triazine o-ethyl s-phenylethylphosphonobithioate 2,3-dihydro-2,2-dimethyl-7- benzofuranylmethylcarbamate [0,0-diethyl 0-(3,5,6-trichloro-2- pyridinyl) phosphorothioate] N-(phosphomethyl) glycine 1,1’-dimethyl-4,4’-bipyridinium ion xi INTRODUCTION As the consequences of soil erosion have become understood, development of crop production techniques that control the loss of soil due to the movement of water and wind have become a major focus of agricultural research. For many years those research efforts have been concentrated in row crop production where large interrow areas are left unprotected and especially subject to the processes of erosion. Mulch tillage systems, cover crops, intercrops and specialized tillage and planting equipment have been developed to minimize the degree to which crop production degrades the soil. In Michigan, corn (Egg mayg) is the number one crop in terms of area planted and dollar value. In 1985, 1.11 million hectares of corn were harvested for grain and another 138,000 hectares harvested as silage (Mowry, 1986). Because corn is planted as a row crop, and is therefore especially prone to soil erosion, it is important to know which conservation tillage systems adapt best to corn production. Reduced tillage systems create new management problems; some of which can be overcome and some that cannot. No tillage system is perfect for every soil type and the problems that develop often do so only after a significant period of time. Experiments, therefore, need to 1 be long term to accomplish credible results. Beginning in 1981, a series of experiments was conducted in southwestern Michigan testing a variety of corn production systems. Some of the systems tested were already commonly practiced by growers in the area. Others offered potential benefits in soil protection while at the same time creating special management challenges. The techniques studied provided a complete spectrum of tillage intensity. The studies described here were performed at the Kellogg Biological Station (K88) in northeastern Kalamazoo County, Michigan. The study sites were characterized by Kalamazoo loam soil (Fine-loamy, mixed, mesic Typic Hapludalfs) with small areas. of‘ Osthemo sandy loam (Coarse-loamy, mixed, mesic Typic Hapludalfs) commonly interspersed. The primary difference between the two soil series is that the Kalamazoo contains a rather dense clay loam B horizon while in the Osthemo the B horizon is sandy loam. These soils, which are common in southwestern Michigan, are well suited for cash grain production with droughtiness the major limitation (Austin, 1979). The goal of the project was to develop an information base which could be used to improve corn production at K88, and elsewhere in the area, by answering the following questions: 1) Which tillage systems produce grain yields commonly expected by growers in the area; 2) What is the impact of a tillage system on soil physical properties such as bulk density, porosity and pore-size distribution? Trends in these parameters could indicate developing soil abnormalities and help pinpoint the need for special management: 3) Does the reduction in soil temperature caused by increasing surface residue significantly affect seedling emergence rate; 4) What will be the effect of tillage system on surface residue buildup and soil organic carbon content: 5) What are the tillage related effects on soil moisture with time and depth; 6) And is it feasible to intercrop corn and a vigorous forage legume in the Northern Corn Belt to provide the ultimate in soil erosion control and benefits of symbiotic nitrogen fixation by the legume? LITERATURE REVIEW Bl. TILLAGE SYSTEMS 81a. INTRODUCTION A brief discussion of the history of tillage in world agriculture is contained in Sprague (1986). He reviews the development of seedbed preparation, beginning in prehistoric times with simple wooden tools used to merely scratch the soil surface, through the development of the moldboard plow in the Middle Ages, to the rapid, mechanically-based opening of the United States’ midcontinent in the early 1900’s. Throughout these times tillage intensity increased as producers sought the goal of an optimum seedbed. Sprague (1986) details the disastrous effects of the increase in tillage intensity in middle America in the 1920’s and 1930's as large areas of farmland were destroyed by water and wind erosion and the subsequent crusade for government intervention. That crusade led to the formation of the Soil Erosion Service (later to become the Soil Conservation Service) in 1933. Some early attempts at pasture renovation using reduced tillage were successful (Cook, 1922; Graber, 1928), but the number of tillage operations and the equipment required made wide use of these practices economically 5 impractical (Sprague, 1986). Two developments in the 1960’s made reduced tillage, including no-tillage, practical on a broad scale. Those innovations were the discovery of broad-spectrum herbicides and improvements in planting equipment which provided proper seed placement in untilled soil (Griffith et al., 1977). Interest in no-till corn (Zea mays L.) production was spurred after studies were initiated in Virginia in 1960 which focused on the effect of tillage intensity on plant growth and grain yield (Jones et a1., 1968). 81b. CONSERVATION V8. CONVENTIONAL TILLAGE Conservation tillage is a generic term meaning different things to different people. It is often used in place of minimum tillage, reduced tillage, mulch tillage and no-till (Mannering and Fenster, 1983), and the wheat (Triticum .aestivum)-fallow system «called stubble-mulch (Crosson, 1981). Crosson (1981) lists several definitions of conservation tillage from a variety of sources. Though these, and other, definitions of conservation tillage vary greatly and often emphasize different primary and secondary tillage operations, they all require the reduction of soil loss by decreasing water runoff and wind erosion relative to conventional tillage. 6 Conventional tillage too, is an ambiguous term. It often relates to the number of tillage operations and the kinds of equipment commonly utilized in a given part of the country. Mannering and Fenster (1983) recommend using the following definition for conventional tillage: "the combined primary and secondary tillage operations performed in preparing a seedbed for a given crop grown in a given geographical area". The decreased soil erosion requirement notwithstanding, this could be a definition of conservation tillage as well. However, because conservation tillage requires that the soil be protected by at least a minimum amount of surface residue and because the moldboard plow buries nearly all residue, the use of the moldboard plow is often considered the difference between conventional and conservation tillage systems (Crosson, 1981). BIO. NO-TILLAGE No-tillage refers to the planting of a crop directly into undisturbed sod or crop residue with the only soil manipulation being that required to ensure proper seed placement. Generally the sod has been chemically killed. (Jones et al., 1968). This system is often described as strip tillage or narrow strip tillage due to the need for some soil manipulation for seed placement. The use of 7 nonpowered fluted coulters, narrow Chisels or angle disks in front of the planting unit allows seed placement in a narrow slot (Mannering and Fenster, 1983). This system is also called sod-planting (Lewis, 1973) and zero-tillage (Free et a1., 1963). 31d. CHISEL PLOWING A chisel plow consists of a heavy frame with cross members to which the shanks are attached. The chisel shanks can be either straight or twisted and range from 6-20 inches in length (Oschwald, 1973). Chisel plowing kills weeds by partially inverting the soil and cutting roots. This action tends to bury a higher percentage of residue as the amount of residue increases, but leaves the soil very rough and loose to provide erosion control (Mannering and Fenster, 1983). Ble. TILL PLANTING Till planting is a system of row cropping where the seedbed sits on top of a ridge. At planting, the top of the existing ridge, along with the previous crop residue, is stripped off and thrown into the valley between the ridges. The seed is then placed in the exposed soil at the top of 8 the ridge by a special planter which performs the whole operation in one pass (Mannering and Fenster, 1983). Cultivation is then utilized for weed control and new ridges are generally formed during the last cultivation (lay-by). The development of this system began at the University of Nebraska in 1956 (Fisher and Lane, 1973). The original goal was to reduce the number of operations and the cost of row crop production under irrigation. The benefits of erosion control were quickly noted as were lower energy and manpower requirements. Weed control, which originally caused major setbacks, is now considered an advantage of the system. According to Fisher and Lane (1973), the adoption of 30 inch rows, the development of preemergence herbicides and increased understanding of the basic function of the system led to this turnabout. 82. INFLUENCE OF TILLAGE ON SOIL PHYSICAL AND BIOLOGICAL FACTORS 323. PLANT PRODUCTIVITY Though many studies comparing tillage systems have shown comparable or increased grain yields when reduced tillage is employed, others have had less favorable results. Soil drainage, soil structure, previous crop and length 9 of growing season are the most likely parameters to influence yields under shallow tillage or no-till systems when weed and insect pests are controlled, according to Griffith et a1. (1977). Indeed, soil type may have the greatest effect on the potential productivity of a given tillage system and the literature on this subject is abundant. For example, Cosper (1983) cites 11 studies designed to detail what he calls the ’soil-tillage relationship’. Other factors which can influence the success of reduced tillage systems include the amount and placement of residue, control of pests, planting date, crop cultivar and management ability of the grower, to name a few. This section will report on some of the research into the major factors affecting grain yields under reduced tillage. According to Triplett and Van Doren (1984), as soil drainage improves the amount of tillage required to maintain yields decreases. Yields from a long term study in Ohio showed significantly greater yields (+10%) from no-till than with plowing on a well drained Wooster silt loam (Van Doren et al., 1976). This was accomplished in 2 of 3 rotations: continuous corn and corn-soybeans (Glycine max). Tillage system was not a significant factor in a corn-oats (Avena sativa)-hay rotation. The same study conducted on a poorly drained Hoytville silty clay loam showed significantly lower yields (-13%) for no-till in continuous corn. Yields were 10 also lower, but not significantly, in the other two rotations. Yield data included in the Van Doren et al. (1976) paper, however, only included years where uniform populations were obtained and weed control was successful. Griffith and Mannering (1984) cite work they conducted in Indiana which shows that no-till yields were reduced on a poorly drained Runnymede loam but were equal or higher on a well drained Tracy sandy loam. This work also shows the positive influence of crop rotation, especially in poorly drained soils. Working on moderately well drained silt loam soils in Kentucky, Herbek et al. (1986) found no-till corn yields (averaged over three years) were greater than for conventional till when planting date was mid-May or later: yields were comparable when corn was planted in late April or early May. Within years, conventional till yields were equal to no-till when precipitation was abundant, but no-till yields were greater in dry years. A study comparing three tillage treatments (no-till, plow-plant, and moldboard plowing with secondary tillage) and three rotations (continuous corn, corn-soybean, corn-oats-hay) was performed in Ohio (Dick and Van Doren, 1985). Each tillage X rotation treatment combination was studied on the following soils: 1) well drained Wooster silt loam with 2.5-4.5% slope: 2) Hoytville silty clay loam with poor surface and internal drainage and high shrink- 11 swell capacity: 3) Crosby silt loam with intermediate drainage characteristics. Results showed that the effect of long-term application of a tillage system was positive for no-till on the well drained, sloping Wooster soil with a 20 year average corn yield increase of 1070 kg ha-l. On the Hoytville soil, continuous no-till decreased corn yields an average of 503 kg ha-l. The yield decrease was greatest for the continuous corn/continuous no-till treatment--880 kg ha-l. Overall grain yields were relatively unaffected by long term tillage application in the intermediate Crosby soil. All crops were similarly affected by tillage. Reduction of no-till yields on the Hoytville soil have been attributed potentially to increased infestations of the fungus Pythium graminicola Subr. in corn and Phytophthora s2; (root rot) in soybeans. Edwards et al. (1988) compared strip tillage and no-till with moldboard plowing in six wheat, corn and/or soybean rotations on a Hartsell fine sandy loam in Alabama. Soybean yields were increased by strip and no tillage when compared with moldboard plowing. Moisture conservation and a reduction in populations of soybean cyst nematode (Heterodera glycines) were cited as reasons. The combination of a two year corn-soybean rotation using either of the conservation tillage systems provided the best soybean yields when averaged over four years. The tillage X rotation interaction was significant for soybean yields in 3 12 of 4 years. Corn yields were significantly increased by crop rotation, versus continuous corn, in 2 of 4 years, but tillage system was significant in only 1 year. The tillage X rotation interaction was never significant for corn. Al-Darby and Lowery (1986) studied no-till, till-plant, chisel plowing and conventional tillage on 3 sites in Wisconsin for 3 years. Two sites were located on Griswold silt loam and the third on a Plainfield loamy sand. Though continuous corn yields did not differ within years, no-till produced a significantly higher grain yield when averaged over 3 years on the Plainfield soil. They noted slowed early season plant growth in the no-till treatments but this did not persist and did not cause reduced yields. Finally, Erbach (1982) evaluated 7 tillage systems in continuous corn and corn-soybean r6tations on poorly drained soils in Iowa. Their results showed that year was more important than tillage system for grain yields. Fall or spring moldboard plowing, till plant and spring disking were the 4 best yielding systems averaged over 5 years. Fall chisel plowing, slot planting and slot planting on ridges all yielded lower and were significantly lower than fall moldboard plowing. Harvest plant populations were not significantly affected by tillage system when averaged over 5 years despite significant variation in 4 of the 5 years. Reasons for within-year differences were not obvious but may have been related to interactions between planter 13 performance, weather and tillage. Low corn yields were often, but not always, associated with low plant populations. B2b. SEEDLING EMERGENCE AND SOIL TEMPERATURE Soil temperature is very important to seed germination and plant growth rate (Lehenbauer, 1914: Coffman, 1923). Lehenbauer, in greenhouse experiments, found a positive, roughly linear relationship between temperature and growth rate of corn seedlings from 10 to 30°C and a negative linear function above 31.7OC when soil and air temperatures were kept equal. No growth occurred below 10°C or above 43.9°c. McCalla and Duley (1946) applied straw mulch to field plots where corn was growing. Weekly mean maximum soil temperature at a depth of one inch was depressed, versus unmulched control plots, by up to 10°C and 13°C for 4.5 and 17.9 Mg ha-1 mulching rates, respectively. The mulch however acted as insulation at night by keeping one inch soil temperatures 1-2°C above unmulched soil. The widest difference between soil temperature in mulched plots and air temperature occurred on clear days at 1300-1400 hours. In a greenhouse experiment, dry weight of plants at equal height varied linearly with the soil temperature at 14 which they were grown (Willis et al., 1957). A concurrent field study concluded that increasing soil temperature increased emergence rate, caused more rapid plant growth and hastened the onset of maturity. Willis and his colleagues also determined that a soil temperature of 24°C at a depth of 10.2 cm appeared to be the optimum for corn grown in their Iowa study. The depression of soil temperatures due to surface residue generally has less effect on the growing crop in southern states than in northern regions. This is because root zone soil temperatures are often near optimum for crop growth in the south and small decreases have little impact on plants, while in the north temperatures are usually lower and can be at or near the critical temperature for growth (van Wijk et al., 1959). In the south it is not uncommon for lowering of soil temperatures by crop residue to improve growth, as soil temperatures can easily rise into the negative-response part of the growth curve described by Lehenbauer. Burrows and Larson (1962) grew corn with 0, 2.2, 4.5, 9.0, and 17.9 Mg ha.1 of corn stalks added as residue to determine the effects of soil temperature on plant growth. They concluded that lowered soil temperatures were the major cause of reduced crop growth and that dry weights and heights of pdants decreased as mulching level increased. Early season corn growth rate was decreased with as little 15 as 2.2 Mg ha"1 of chopped corn stalk residue. Each 1 of mulch, up to 9.0 Mg ha-l, lowered additional 2.2 Mg ha- soil temperature another 0.400 at a depth of 10.2 cm. When corn plants are small, interactions between tillage method and planting direction can influence soil temperature significantly. Burrows (1963) compared ridge planting, 'listing' tillage (corn planted at the bottom of the furrow), and conventional tillage, each with rows planted either east-west (EW) or north-south (NS). In-row soil temperatures were found to be as follows: EW ridge-planting > NS ridge—planting > EW conventional > NS conventional > listing tillage with no directional differences. In 23 location-years of field trials at nine sites (including Iowa, Georgia and New York), Allmaras et al., (1964) found a 1.2°C and 1.3°C depression in 10.2 cm soil temperatures 0-3 and 3-6 weeks after planting, respectively, when 6.7 Mg ha.1 of oat straw was applied as mulch. This decrease in temperature in southern locations generally produced positive or no response in crop growth, while in the north a negative response was often noted. On average, early season growth rate of corn and soil temperature at seed depth are related, but these parameters are not necessarily related to grain yield or season-ending dry matter production. They do, however, influence rate of maturity which has two important ramifications: higher 16 potential of frost damage due to a longer growing season: and a tendency to have higher grain moisture content at harvest which increases drying costs to the grower (Olson and Schoeberl, 1970). The pattern of soil temperature variance with tillage method is similar with a wide range of soil types. Soil temperatures were measured in five soil types in northern, southern and eastern Indiana by Griffith et al. (1973). The soils ranged from a Tracy sandy loam to a Pewamo silty clay loam. Eight tillage systems were compared in 1969 and 1970. Temperatures were coolest with chisel plowing, no-till with a fluted coulter, and strip-rotary planting in 20 cm strips. Of the systems tested, these left the most surface residue. A Manitoba study compared five tillage methods for their effect on soil temperature (Wall and Stobbe, 1984). Tillage systems compared were conventional tillage-fall (CTF), conventional tillage-spring (CTS), rotovated strip tillage with 10 cm strips (RTS), zero tillage using fluted coulters (ZTF) and zero tillage with straight coulters (ZTS). Again, tillage had a major impact on soil temperature with the daily maximum generally affected more than the minimum. Treatment effects were noted to a depth of 20 cm though the greatest differences were in the upper 5 cm. Shape of the coulters in the zero tillage options had little influence on temperature. CTS had the highest daily maximum temperature of all methods. CTF resulted in 17 decreased maximum temperatures but had increased minimums at 5 cm when compared to CTS. CTF showed increased early season moisture content near the soil surface and this, coupled with an improved seed bed using fall tillage, improved emergence and time to silking. Soil temperatures in the first two months of the season were comparable in CTS and rotovated strip tillage. 82c. SOIL PHYSICAL PROPERTIES The relationship of soil physical properties to crop production are complex and interrelated. Many physical properties affect the erodibility of a soil. According to Letey (1985) there are four soil physical properties which directly affect plant growth: water content, oxygen content, temperature and mechanical resistance. Of these, water content directly affects the other three. The other commonly measured physical properties such as bulk density, pore size distribution, texture and aggregation all have indirect influence on pdant growth by directly impacting water content, aeration, temperature and mechanical resistance. 18 826.1. PORE SIZE DISTRIBUTION Pore size distribution is calculated by developing a moisture characteristic curve which assumes soil water content is a function of matric potential (dgh) where dgh = 2y(cos a)/r Eq. (1) where d = density of water, g = gravity, h = hydrostatic suction, y = surface tension of water and a = contact angle, one can solve for r (the effective pore radius) at different matric potentials (dgh). Equation (1) is based on the principle of capillary rise and is therefore only applicable to pore sizes where these forces act (pore sizes <3 mm or a matric potential of <-0.1 kPa) (Hamblin, 1985). This theory assumes that the capillaries, or soil pores, are tube-like in shape and that the contact angle is always zero (Danielson and Sutherland, 1986). Soil pores, however, may be irregular in shape and size, resulting in erroneous lab analysis of soil for ‘total porosity' or’ pore size distribution. In many laboratory analyses the sample size, or soil core, is often smaller than the structural unit being studied. This is particularly so in the vertical direction where the sample core may be shorter than the length of many pores thus leading to a bias toward smaller pore sizes. .According to Letey (1985) pore size distribution affects the relationship between water and both mechanical resistance and aeration and is therefore 19 important to the viability of root systems. The interaction of management and pore size distribution is complex, and causes inconsistent predictive information on specific tillage systems (Hamblin, 1985). Some studies have found a decrease in porosity in the size range of 50-500 microns (-60 to -600 kPa of matric potential) in no-till soil versus a moldboard plowed soil (Douglas, 1980). Others have found increased porosity in this pore size range primarily due to increased invertebrate activity. Ehlers (1975) found the number of earthworm (Familiy Lumbricidae) channels was increased for no-till versus conventional tillage. At a depth of 20 cm nearly twice the number and volume of channels were found in the no-till treatment, while within 2 cm of the surface about 4 times more were found under no-till. Most of the shallow channels actually reached the surface and helped to improve water infiltration. B26.ii. BULK DENSITY Like pore size distribution, bulk density has an indirect impact on plant productivity by affecting the relationship of water content with aeration and mechanical resistance. Higher bulk density increases the intensity of the effect of aeration and mechanical resistance on plant 20 growth. Ietey (1985) proposes the term non-limiting water range (NLWR) as the actual water available to plant roots, as opposed to the common range bounded by the permanent wilting point and field capacity. High bulk density increases the probability that mechanical resistance will inhibit root growth and, therefore, access to soil water. In this case, mechanical resistance could become limiting at a moisture content greater than what wouLd be considered normal based on the permanent wilting point measurement. Thus the NLWR is narrowed indirectly by high bulk density. Mannering et al. (1975) compared surface bulk densities averaged over five soils in a long-term tillage study at Purdue University. Bulk density, two to three weeks after planting of row crops, was slightly higher in the till plant system than with moldboard plowing. NT had much higher bulk densities. There was no indication of persistence of these variations, however. Working with a Chalmers silty clay loam, Costamagna et al. (1982) compared fall moldboard plowing, spring field cultivating and spring disking for corn production. They found no significant tillage-related differences in bulk density to a depth of 25 cm, nor were there differences between June and August samplings within any of the three tillage systems. Blevins et al. (1983) 'measured no significant difference in bulk density between no-tillage and 21 conventional tillage after 10 years of study on a Maury silt loam (0-7.5 cm and 7.5-15 cm). They also measured no differences on a Johnson silt loam in Western Kentucky (0-7.5 cm). Blevins et al. (1983) cite two studies where no-tillage increased bulk density versus chisel plowing or moldboard plowing, however, there was no evidence that the increase affected yield. Hill and Cruse (1985) found no significant effect of tillage on bulk density on two Iowa mollisols: a Canisteo clay loam and a Nicollet loam. They compared fall moldboard plowing, spring disking and no-till on the Canisteo soil and fall moldboard plowing, fall chisel plowing and slot-planting on ridges on the Nicollet soil. Invertebrate activity may improve bulk density if intense tillage does not interfere. Lal (1976) found 4-5 times more earthworm activity under a no-till system: bulk density and surface crusting decreased, thus improving infiltration. Variation in the effect of tillage system on bulk density is common across agro-climatic zones, and is closely related to soil type and climatic conditions (Blevins et al., 1984). 22 B26.iii. ORGANIC MATTER CONTENT Cultivation enhances soil organic matter degradation by increasing chemical and microbial oxidation. Reduced tillage jpractices at least partially counteract the inevitable soil degradation (Hamblin, 1985). Bauer and Black (1981) measured soil organic carbon (SOC) in fields from three textural groups on the Great Plains which had been stubble mulched for 25 years. They compared these results with conventionally tilled fields. Stubble mulching improved SOC content by 44% in sandy soils and 13% in fine texture soils. SOC was not affected by tillage in the medium textured soil. When averaged over the three textural groups, stubble ‘mulching significantly improved SOC content. Within soil texture groups, variation in SOC content appeared closely tied to reduced soil erosion under stubble mulching. Costamagna et al. (1982) measured soil organic matter (SOM) content (0-5 cm) on an Indiana Chalmers silty clay loam. They compared spring field cultivation followed by two diskings, spring shallow disking prior to planting, and fall moldboard plowing for seven years of corn production. After 7 years, spring field cultivation (4.68% SOM) and spring disking (4.89% SOM) produced significantly higher SOM contents than moldboard plowing (3.79% SOM). After ten years of corn production, a Kentucky soil 23 under no-till had twice the SOM content (0—5 cm) than conventional tillage (Blevins et al., 1983). The same study also showed positive effects of nitrogen fertilizer (N): Under no-till, annual applications of N (84 kg ha-l) increased SOM (0-5 cm) an average of 1.12% versus nonfertilized treatments. Applications of N did not stop the decrease in SOM under moldboard plowing. In their review of conservation tillage, Blevins et al. (1984) cite work showing the positive influence of surface residue on SOM and its positive influence on infiltration. BZO.iV. SOIL MOISTURE CONTENT As a soil begins to dry, the mulching effect of surface residue will slow evaporation losses (Bond and Willis, 1969) and this can lead to increased water storage over the course of a growing season (Larson et al., 1978). Loss of water due to runoff is also reduced as tillage intensity is decreased (Laflen et al., 1978) which can also increase total soil water storage. Jones et al. (1968) observed increased soil moisture content in corn planted in killed grass sod in 3 silt loam soils in Virginia. A surface mulch in no-till corn (with killed rye cover) on a Maury silt loam in Kentucky resulted in greater water 24 use efficiency through increases in soil shading and infiltration and decreases in runoff and evaporation. Soil moisture was greatest earLy in the growing season under no-till versus moldboard plowing. The difference was less after canopy closure apparently due to increasing plant uptake at this point in the season. Blevins et al. (1983) concluded that no-till should help carry a corn crop through short-term droughts. Al-Darby' and Lowery (1986) found increased soil moisture content in the surface 25 cm of a Griswold silt loam in all three years of a Wisconsin study, and in two of three years on a Plainfield loamy sand, when no-till and conventional tillage were compared. Measurements were made in corn at pollination. Chisel plowing and till-plant had intermediate moisture contents on the Griswold soil. In the review by Griffith et al. (1977) several studies were cited which show increased moisture conservation under no-till and reduced tillage systems. They concluded that conservation tillage systems produce increased soil moisture storage if at least 50% of the soil surface remains covered with crop residue. EXPERIMENTAL METHODS C1. STUDY SITES AND TREATMENTS This study was comprised of 3 field sites. The site designations and years of study were F90 (1981-85), F84A (1982-84), and F848 (1983-85). Site designations correspond to KBS field numbers. F84A and F848 were adjacent sites in field #84. This field had been strip cropped prior to the beginning of the study and, according to the historical labelling, site F84A was located in strips C and E, while site F848 was located in strips 8 and D. Plot size in F90 was 4.5 by 16.8 m (Figure 1) and 9.1 by 15.2 m in both F84 studies (Figure 2). Table l decribes the tillage systems (and their labels) that were studied. Problems with the legume intercrop trials forced several changes in those particular treatments over the course of the experiment.1 Treatment designations 1 Because many problems developed in this part of the study, including several complete crop failures, and because a master's thesis project (Schulz, 1986) which detailed many of these problems ran concurrently with our study, the legume intercrop objective will be virtually ignored in this paper. Some results will be presented where they are available. 25 26 /// Irrigated S No-Till in Alfalfa C No-Till with Rye Cover Crop CP Chisel Plower N No-Till P Plowed Figure 1. Plot layout for site F90 27 vusosm a vososm Humane mo uu>osu was as assenoz e mmfimws< as Hosanoz m HHHs-oz z Ho>oo use nus: Hflesloz u woumwfiuuH ounce: .musmsfiuoaxo «mm soon now uaoama uOHm .N ouswfim 28 for those plots were changed when necessary to reflect the use of a different forage legume or implementation of a completely new tillage system. These designations are noted in Table 1. Irrigation and manure treatment labels are also described in Table 1. Each treatment was replicated four times at each site. Data from this investigation was generally analyzed as a split-split-plot with irrigation as the main treatment, manure as the subtreatment and tillage system as the sub-subtreatment. In some years soil moisture was measured only in the nonirrigated subtreatments. In this case data was analyzed as a split block with manure as the main plot and tillage systems as the subplot. For cases such as the soil core collections and hourly soil temperatures measurements, where only one treatment was sampled, the randomized block with sampling was the model used. Error bars on all graphs in this paper are based on analysis using the Least Significant Difference test (LSD) at 'the significance level of 0.05, except where otherwise noted on the graph. Where error bars are missing either the LSD was not significant or a non-significant F test precluded LSD analysis. (pers. com. C.E. Cress; Steel and Torrie, 1980; Gomez and Gomez, 1984). For the sake of brevity only statistical comparisons between tillage system will be discussed in this thesis. 29 Table 1. Tillage system and treatment labels/descriptions. CCNT No-till with fall seeded rye cover crop CP Chisel Plowing NT No-till with all cover killed Plow (P) Moldboard Plowing RCNT Red clover or Hairy Vetch intercrop SNT Alfalfa intercrop (Till-Plant in 1985) RT Ridge Tillage Treatments Control (C) No manure and no irrigation Manure (M) 22-27 Mg ha dairy manure annually Irr (I) Irrigation through solid-set system Man-Irr (MI) Both manure and irrigation applied 30 C2. CULTURAL METHODS Manure applications were made to the appropriate plots in the early spring each year using manure from the KBS dairy Operation. The manure included significant amounts of straw. Rate of application was approximate but ranged from 22-27 Mg ha.1 of dry matter. Moldboard plowing was performed with a 3 by 41 cm bottom Model 82 Massey-Ferguson mounted plow. Plowing depth varied some with operator but was in the range of 15 to 20 cm. Depth of chisel plowing was 20 to 25 cm and was accomplished with a Glencoe ’Soil Saver’. This implement features straight disks in front of twisted chisel shanks. Secondary tillage was usually performed with a disc harrow. In 1981-83, a 4.3 m John Deere pull-type disk harrow (model unknown) was used, while after 1983 a 1.8 m Massey Ferguson mounted disk harrow was availabLe. On occasion a 6.1 n: Glencoe ’Soil Finisher’ was utilized for secondary tillage. When necessary to smooth rough spots before planting a 2.4 m Model 213 Pittsburgh mounted drag harrow was used. Tables 2 to 4 list dates of primary and secondary tillage for F90, F84A and F848, respectively. Table 5 lists the date and amount of preplant broadcast applications of potassium (K) fertilizer for each year and study site. All applications were made with commercial size broadcast spreaders set as recommended so application rates 31 Table 2. Dates of primary and secondary tillage: Site F90. Moldboard Plow Chisel Plow Year Primary Secondary Primary Secondary 1981 3OAPR 4MAY 20APR 4MAY 1982 29APR 29APR 3DEC81 29APR 1983 5MAY 9MAY 6MAY 9MAY 1984 25APR 3MAY 2MAY 3MAY 1985 19APR 1MAY NOV84 18APR Table 3. Dates of primary and secondary tillage: Site F84A. Moldboard Plow Chisel Plow Year Primary Secondary Primary Secondary 1982 29APR 29APR 29APR 29APR 1983 27APR 9MAY 27APR 9MAY 1984 29APR 3MAY 25APR 3MAY 32 Table 4. Dates of primary and secondary tillage: Site F848. Moldboard Plow Chisel Plow Year Primary Secondary Primary Secondary 1983 27APR 9MAY 6MAY 9MAY 1984 29APR 3MAY 25APR 3MAY 1985 18APR 1MAY NOV84 1MAY 33 Table 5. Preplant K O fertilizer applications as 0-0-60. 2 kg ha.-1 Year Trts F90 F84A F843 1981 A11$ 101 -- ’- 1982 NM 168 168 '- MAN -- 78 ’- 1983 NM -- 56 '- 1984 C 168 -‘ ’- I 224 “ ‘- NI -- 112 -‘ IRR -- 168 -- 1985 C 56 -- '- I 168 -- -- §All plots also received 112 kg ha"1 of 8-32-16 broadcast *preplant in 1981. Treatment Designations: C=Control. M=Manure. = Irrigated. NM=All plots not receiving manure. MAN=All plots that received manure. NI=All non-irrigated plots. IRR=All irrigated plots. 34 are approximations. All K applications were based on soil samples collected in the early spring and analyzed by MSU’s Soil Testing Lab (warncke et al., 1985; Warncke et al., 1987). Buffalo slot-type planters were used for all planting. A Buffalo model #4500-AAS was used from 1981-1984. In 1985 an improved version of that planter (model #5030) was used. The Model 5030 featured Kinze plateless seed units and an improved planter drive system which reduced variation in seeding rate caused by slippage of drive wheels in differing soil conditions, which was a problem with the older model. In all cases row spacing was 76 cm. Granular starter fertilizer formulations were applied. with the model #4500-AAS and liquid starter was used with the #5030. Table 6 lists the formulation and rate of starter fertilizer applied each year and also includes information about the granular insecticide applications made at pdanting time. Table 7 includes the annual corn planting dates for each site. Herbicide applications varied from year to year to fit current weed control needs. Rates were set using the annual "Weed Control Guide for Field Crops" from the Cooperative Extension Service (Bulletin E-0434) or through discussions with experienced university personnel. CP, P, NT and CCNT generally received tank mixes of atrazine, cyanazine and alachlor. NT, CCNT and RT also had paraquat added to the 35 Table 6. Starter fertilizer and insecticide applications. Year Fertilizer Insecticide 1981* 112 kg ha:i 8-32-16 11 kg ha:i Furadan 106 1982 112 kg ha_1 10-40-30 9 kg ha_1 Lorsban 156 1983 112 kg ha_1 8-40-10 6 kg ha_1 Dyfonate 20G 1984 112 kg ha_1 8-40-10 9 kg ha_l Lorsban 15G 1985 37 L ha 9-18-9 6 kg ha Dyfonate 206 Fertilizer and insecticide rates and formulations were the same for all study sites within a given year. # Table 7. Annual corn planting dates. Year F90 F84A F843 1981 4MAY -- -- 1982 3MAY 3MAY -- 1983 11MAY 13MAY 13MAY 1984 7MAY 3MAY 3MAY 36 tank mix if it was necessary for control of early emerging weeds. Glyphosate or paraquat was used to kill the rye (Secale cereale) cover crop in CCNT, depending on size of the rye. Herbicide applications varied widely in SNT and RCNT while attempting to find a suitable technique for legume suppression. Nitrogen (N) fertilizer was applied each year after crop emergence using the ammonium nitrate formulation 34-0-0. Rates varied generally based on a reasonable yield goal and the number of years of continuous corn on the site. In 1981-82 split applications were made based on field tissue tests conducted periodically on each plot. This was discontinued after finding few tillage related differences in tissue tests. Tables 8-10 show the dates of application and total N applied to each study site. In 1983 application 1 . increments but was not of N was split into 22.6 kg ha- based on tissue tests. Broadcast applications were made by hand-dispersing known amounts of fertilizer uniformly over each plot. Band applications were made using sprinkling cans and walking at a calibrated speed while the dry fertilizer dropped into the center of the inter-row (pers. com. M.L. Vitosh). Irrigation was applied to the appropriate plots in each study using solid-set sprinkler systems. Application amounts were 3.8 cm/week (minus rainfall) in 1981-1982 and after 1982 were based on either evaporation pan data or 37 Table 8. Nitrogen fertilizer schedule: Site F90. Year Date Tillage Treatment Rate‘ 1981 23JUN All All 56 13JUL SNT All 28 NT All 28 CCNT A11 28 17JUL All All 28 23-24JUL All All 28 3-4AUG All All 28 1982 10JUN A11 A11 56s 19-20JUL All All 56 1983 27APR All All 224$ 1984 29JUN All All 112 1985 23MAY All All 168 $Values in kg ha.1 actual N in form of NH N03. N applied in 28 percent liquid form using a knife applicator. 38 Table 9. Nitrogen fertilizer schedule: Site F84A. Year Date Tillage Treatment Rate’ 1982 9-10JUN All All 56$ 8-12JUL CCNT All 56$ SNT All 56$ RCNT All 56$ NT All 56$ 23-26JUL All All 56 1983 22-23JUN All All 56 13-15JUN All All 56 30JUN All Irr,Man-Irr 56 1984 2JUL All All 112 $Values in kg ha-1 actual N in form of NH N03. N applied in 28 percent liquid form using a knife applicator. 39 Table 10. Nitrogen fertilizer schedule: Site F848. Year Date Tillage Treatment Rate’ 1983 22-23JUN All All 50 13-15JUL All All 50 30JUN All Irr,Man-Irr 50 1984 2JUL All All 150 1985 20MAY All All 150 i ............................................. Values in kg ha-1 actual N in form of NH4N03. 4O computerized irrigation scheduling programs. Table 11 lists the annual amounts of irrigation water applied. In 1982 F84A was not irrigated as planned due to failure of the supply well. Irrigation requirements depend heavily on weather conditions, therefore mean monthly high and low temperatures and mean monthly rainfall totals are listed in Table 12 for the months April to October for each year of the project. C3. DATA COLLECTION C38. SOIL TEMPERATURE Soil temperature becomes an important concern in the northern Corn Belt as tillage intensity is reduced and surface residue builds up. It is a primary factor in seedling emergence rate and can therefore impact total germination. Soil temperature was measured each year in one or two sites in as many treatments as labor or equipment would permit. Table 13 lists by year, the site, treatments and depths involved in soil temperature measurements. All temperatures were measured in the row. In 1981 and 1982 dial thermometers with rigid metal probes were used to collect three temperatures in each treatment. These were given ample time to equilibrate at each placement. In an attempt. to reduce, equilibration 'time, Fisher' digital 41 Table 11. Irrigation summary: Total amounts and events. Year F90 F84A F848 1981 19.7 (6)3 -- -- 1982 20.8 (6) at -- 1983 23.9 (7) 22.7 (7) 22.7 (7) 1984 26.1 (7) 30.6 (8) 30.6 (8) 1985 10.9 (3) -- 11.5 (3) $ Values in parenthesis are total irrigation events for year. **Irrigation unavailable due to inadequate pump capacity. 42 Table 12. Monthly rainfall and mean high/low temperatures. 1981 °c cm Month High Low Rain May 20.7 7.2 8.7 June 26.3 14.8 10.8 July 28.7 16.3 4.3 August 27.7 15.2 9.3 September 21.6 10.9 17.4 October 14.8 3.4 8.2 1982 °c . cm Month High Low Rain May 24.6 11.9 10.2 June 23.8 11.9 10.5 July 28.3 16.8 10.8 August 26.9 14.4 . 5 5 September 22.9 11.7 3.5 October 18.7 5.8 2 9 43 Table 12, continued. 1983 °c . cm Month High Low Rain May 18.9 6.7 13.8 June 27.2 13.3 4.9 July 31.1 18.3 7.3 August 30.0 17.8 7.3 September 25.0 11.7 11.0 October 16.6 6.1 5.7 1984 oC. cm Month High Low Rain May 18.3 6.1 11.6 June 28.3 15.0 0.7 July 28.3 15.6 . 8 August 30.0 16.7 2 September 22.2 11.1 15. October 18.3 8.9 8 44 Table 12, continued. 1985 °c . cm Month High Low Rain May 23.4 9.8 11.9 June 24.8 12.4 4.5 July 28.6 16.0 11.7 August 26.1 15.1 10.7 September 24.1 13.4 5.6 October 18.2 6.9 12.9 45 Table 13. Soil temperature measurement schedule. Time of Day Year Site Tillage Trtmt$ Depths or - (cm) Interval 1981 F90 All All 5.1 800, 1400 1982 F90 All All 10.2 1400 F84A All All 10.2 1400 1983 F84A All C M 5.1,10.4 1400 (Reps 3-4 only) F84A CCNT, P I 5.1,10.4 Hourly (Rep 3 only) 1984 F84A CCNT, P I 5.1,10.4,30.5 Hourly (Rep 3 only) 1985 F848 CCNT, P I 5.1,10.2 Hourly (Rep 3 only) Treatment designations: C=Control: M=Manure; I=Irr. 46 thermometers were tried in 1982. The probes on these thermometers were not rigid enough to penetrate no-till soil and they had to be discarded in favor of the rigid dial thermometers. Beginning in 1983 copper-constantin thermocouples were placed in appropriate treatments and soil. temperature was recorded using a Model 516 ’Polycorder’ programmable datalogger from Omnidata International, Inc. The Polycorder, with its programming and storage capabilities, allowed the collection of hourly soil temperatures on selected treatments. The ’Time of Day’ column in Table 13 refers to the starting time for measurement of early morning or mid-afternoon soil temperature. These times were chosen to find approximate daily high and low soil temperatures in each treatment. 47 C3b. SEEDLING EMERGENCE Seedling emergence was determined each year on at least one site by marking off sections of two rows in selected treatments and counting emerged plants until totals leveled out. A plant was counted as emerged if it could be seen through residue in the row. Residue was not moved to look for seedlings. Table 14 lists by year, the sites, treatments and row length counted to determine emergence rate. It also shows the beginning and ending dates of counting. C36. CROP RESIDUE AND SOIL CARBON MEASUREMENTS Ground cover measurements were made in the years 1983 to 1985 by taking photographs of a known area, projecting the photos on a grid and determining percent cover by a line-intersect method (pers. com. J.V. Mannering). Three photographs were taken in each plot each year and analyzed for dead residue, living cover and bare soil. Photographs were taken within about 4 weeks of planting before corn plants were large enough to cause interference with the photographs. On April 28, 1986, soil samples were collected in F90 to determine total carbon content after 5 full years under the various tillage regimes. A punch probe was used to take Table 14. 48 Annual seedling emergence count schedule. Rows Length (meters) F90 F90 F84A F84A F84B F84B All All All All All All All All All All All 08JUN 17JUN 17JUN 08JUN 08JUN 3OMAY 49 several samples in each plot which were then composited. Samples were taken for depths of 0-1 cm and 1-5 cm. All treatments of the CCNT, NT, P and CP were sampled. TwO composite samples per plot were analyzed by the Michigan State University Soil Testing Lab using a modified Walkley-Black method. C36. SOIL MOISTURE Soil moisture was measured in all years by using a neutron moisture probe. A Campbell-Pacific Nuclear Model 503DR with an Americium/Beryllium neutron source was used for these measurements. Aluminum pipes, 5.1 cm in diameter, were used as access tubes. Table 15 shows by year, the site, treatments and depths measured. Also listed are the first and last dates of measurement and the total number of measurements made each year. This varied somewhat primarily depending on available labor. In all cases there was one access tube per plot. C38. SOIL PHYSICAL PROPERTIES Each year beginning 1982 a series of undisturbed soil cores (7.6 cm diameter X 7.6 cm high) were collected to 50 Table 15. Soil moisture measurement schedule. Year Site Till Trts Depths Begin (cm) 1981 F90 All C,M 31,61,91 6JUN I,MI 31,61 6JUN 1983 F84A All C,M 31,61,91 30JUN I,MI 31,61 30JUN 1984 F84A All C,M 15,31,46,61,76 24MAY :gT>-- I 15,31,46,61,76 24MAY 1985 F848 A11 C,M 15,31,46,61,76 24MAY N; >-- I 15,31,46,61,76 28MAY § .......................................................... MI=Man-Irr. End Total Days 23SEP 13 23SEP 13 31AUG 8 31AUG 8 30AUG 10 21AUG 12 21AUG 12 22JUL 9 Treatment designations: C=Control: M=Manure; I=Irr; 51 determine bulk density, total porosity and pore size distribution. Table 16 lists which sites and treatments were sampled each year and the number of cores taken per plot. Due to laboratory constraints only the NT and P tillage systems were sampled until 1985, when CP was also sampled. For the same reasons, only the surface soil was sampled to a depth of 7.6 cm. Bulk density was measured using the core method as described by Blake and Hartge (1986). Cores were generally analyzed at tensions of -0.98, -1.96, -2.94, -3.92, -5.88, -9.81, -32.66 and -98.07 kPa (-10, -20, -30, -40, -60, -100, -333 and -1000 cm water) using a tension table or pressure cooker apparatus. Cores were dried in a forced air oven at 105°C. for greater than 24 hours for bulk density and total porosity determinations. C3f. PLANT POPULATIONS AND GRAIN YIELDS Prior to grain harvest selected rows of each plot were cut to a suitable length and all plants in each row were counted to determine final population. Table 17 lists by year, the site, harvest date, the number of rows cut per treatment and their length. When the crop was fully mature a Gleaner A2 combine with a built-in tank scale was used to harvest eadh plot. Sufficient time was allowed for the machine to clean out at the end of each plot. Weight of 52 Table 16. Intact soil core sampling schedule. Year Date Site T111 Trt’ Cores/plot 1982 23JUN F90 P,NT C 5 22JUN F84A P,NT C 5 1983 Late July F90 P,NT C 5 F84A P,NT C 5 F848 P,NT C 5 1984 Late July F90 P,NT C 5 F84A P,NT C 5 F848 P,NT C 5 1985 18JUN F90 P,NT,CP C 5 18JUN F84B P,NT,CP C 5 i .................................................... Treatment designation: C=Control. 53 Table 17. Grain harvest schedule. Year Site Date Number Length of rows of rows (meters) 1981 F90 10NOV 2 12.2 1982 F90 280CT 2 12.2 F84A 29OCT 3 12.2 1983 F90 18OCT 2 12.2 F84A & B 24OCT 3 9.1 1984 F90 220CT 2 12.2 F84A & B 29OCT 3 12.2 1985 F90 29NOV 2 12.2 F84B 14NOV 3 12.2 54 grain harvested was recorded and a subsample collected from eadh treatment for determination of grain moisture content. A Burrows Model 700 Moisture Computer was used for grain moisture measurement. RESULTS AND DISCUSSION D1. SEEDLING EMERGENCE RATE Seed germination and seedling emergence are primarily affected by soil temperature and soil moisture. One of the concerns of reduced tillage systems in the northern Corn Belt is that the mulch effect of surface residue will keep the soil too cool for quick germination and emergence. This can cause reduced stands and an effectively shorter growing season. Generally speaking emergence rates during all 5 years of this study tended to show the expected pattern; that is the less surface residue the more quickly seedlings emerged. Figure 3 is a clear example as significant tillage related differences in number of plants emerged per meter of row existed throughout the measurement period in the F90 Control treatment in 1982. Emergence was not complete in the SNT and CCNT tillage systems until 19 days after planting. In some years the differences were not always as great, especially in warm and dry springs, and in other cases emergence rates were primarily affected by factors other than surface residue and cool soil temperatures. As Erbach (1982) reasoned, planter interactions with soil conditions were very important. It is difficult to get 55 56 Nmmw II 9.20 65:00 0mm toe 3:300 mocomtoEm .n 059... 300 «@233 F Nmzaa F «02:30 «3(sz NQ><2NN «Grim P «95.28 _ . E . _ _ .0 E a no...“ ... do 4 hzm o ...zuu U S m >01 I even neaucuad .9 MM WflflH .9 .ou MOJ )0 5.191qu 0'9: Jed siuold 57 seed planted at exactly the same depth across all the tillage systems. Unless soil moisture content was nearly perfect, planting depth was sometimes less in the untilled plots than in CP and P. Therefore, in P and CP, seedlings occasionally grew a greater distance before emerging, thus appearing to emerge somewhat slower relative to NT, CCNT, etc. Not only was depth of planting hard to regulate but so was coverage of the seed slot by the planter, especially when conditions were dry or residue was very dense. Soil in tilled treatments was much more easily replaced over the seed slot than in the untilled systems. This had the same effect as the planting depth problem with seeds in the various no-till systems being closer to the surface and the seedlings emerging faster. An example where seed placement probably had an impact on emergence is shown in Figure 4, where corn in the NT emerged significantly faster than in P and CP. Also notable is the very rapid emergence of corn in the RT. This was the first year that the RT method was included in the study, taking the place of the SNT-legume intercrop. It was necessary to use a second, specially equipped Buffalo planter to plant the RT. The very high emergence rate curve for the RT was caused by failure to adjust the seeding rate to the lower, nonirrigated population when the RT/Control and Manure treatments were planted. In spite of this, 58 mm? II 9.20 6.380 mew“. :2 3:300 mocomLoEm ..V 059... 30m 228 >65 228 >522 :38 r L _ _ _ .6 304a * was“: O #20: + no 4 5 6 .9 #200 D .8 « >0: I even ucaucoud ? [17 i .on MOJ )0 51919111 ('9 19d s1uo)d 59 because the curve already leveled off by May 13, it is obvious that corn in the RT emerged rapidly. Another factor which complicated the interpretation of emergence rate data was a high infestation of Deroceras reticulatum (grey slug) in some years of the study. These pests occurred primarily in CCNT and NT plots with high amounts of residue. They were especially prevalent in Manure and Man-Irr treatments of the no-till systems. For example in 1982 (F90) an outbreak occurred which caused severe damage to emerging seedlings in manured treatments of CCNT and NT. Figure 5 indicates that corn in NT and CCNT emerged much slower than in other systems, when in fact some of the difference can be attributed to seedling mortality caused by feeding slugs. The addition of manure tended to sharpen the tillage-related differences in seedling emergence rates. Figure 6 shows emergence rate curves for Manured plots in F84A (1983) where corn in P and CP emerged significantly faster than the residue covered NT and CCNT and the heavily shaded intercropping systems of SNT and RCNT. Patterns such as this were comm0n throughout the study. Manure and Man-Irr treatments in F90 (1981 and 1982) and F848 (1984) all had equally clear variation. 60 Nmm— II 303 t_l:oz can toe 3:300 00:09.95. .m 0.39... 300 32:33 P «@233 F 32:30 Norse mu N0><2NN N933 P «93.8 _ _ _ _ _ 11 L t . o ...z 6 rant ... do 4 ...2w 0 ...200 D .n m >0: I even caducenn DUI! ..OF T MI .9 .ou MOJ )0 smpw 0'9: Jed s1uo|d 61 nmmp II 30.0 03:02 <33 toe 3:300 00:090.:m .0 0:39... 300 232: 2333 >338 238 _ _ h _ .o 30.5 i no 4 hzm O E o .9 ...20m + #200 D .8 an >0: I even unnucanu .on .3. T1 .00 M01 )0 8.19le ('9 Jed SWDId 62 D2. RESIDUE AND SOIL CARBON Table 18 shows values for crop residue, living plant material and bare soil as percent of total ground cover for each treatment of four of the tillage regimes as determined from photographs taken each spring during the years 1983 to 1985. These values are combined means of all sites which had been in corn for at least one full year thus giving time for each cultural system to have full impact on ground cover. A total of 7 site-years, or 84 photographs, make up each mean. The value for CCNT however excludes results from F84B in 1985. At the time those photographs were taken the rye cover, though it had been sprayed, had not yet died and was recorded as living cover (Table 19). The value for CCNT in Table 18 is therefore based on 6 site-years or 18 photographs. The combined ground cover data shows that, when manure was not applied to CP, the amount of residue left on the soil surface after planting is not necessarily great. Indeed, according to some definitions (Conserv. Tillage Inf. Center, 1984), there was not enough cover to qualify as a conservation tillage method. Applications of manure to CP did improve the percent of cover as residue to significant levels and irrigation also appears to have provided a slight increase over nonirrigated treatments. Moldboard plowing, though not perfectly efficient, left 87% to 92% of the soil 63 Mean percent ground cover: Seven site-years. 45 5 50 52 5 43 30 4 66 5 6 89 8 5 87 5 4 91 92 3 5 92 2 6 74 3 23 78 3 9 94 2 4 84 3 13 Table 18. TILL |RES CP 21 3 PLOW 4 4 NT 74 4 CCNT 80 3 # Ground cover types: RES=Dead plant residue or manure: LC= *Living plant material; BS=Bare soil. Values for CCNT exclude 1985 measurements from F84B. Mean percent ground cover: Site F848, 1985. 31 4 65 55 6 39 26 4 70 6 9 85 6 4 90 7 3 90 98 2 0 98 2 0 91 2 7 11 88 1 12 87 1 6 90 4 98 2 0 98 2 0 93 4 3 44 13 43 52 4 44 30 7 63 Table 19. TILL |RES CP 6 3 PLOW 3 4 NT 74 2 CCNT 10 84 RCNT 98 2 RIDGE 16 7 # Ground cover types: RES=Dead plant residue or manure; LC= Living plant material: BS=Bare soil. 64 surface bare. In NT residue percentages jumped dramati- cally especially where manure was applied. NT/Control and Irrigated had values of 74% as crop residue while Manure and Man-Irr reached 92%. CCNT was an equally effective treatment for producing ground cover. In CCNT treatments including manure, about 90% of the soil surface was covered with residue. In the CCNT/Control and Irrigated treatments the rye cover crop improved ground cover as residue by 6% to 10% over the corresponding treatments in NT. It is clear from the ground cover data that no-till systems should provide significant protection against wind and water erosion by creating a fairly complete layer of surface residue. Where manure is also applied, residue cover reaches levels of about 90%. In non-manure systems, a rye cover crop (CCNT) can provide an additional ten percent ground cover over NT. In 1981 and 1982 some attempt was made to qualitatively measure soil loss under Control treatments of each tillage system in F90 using a system of weirs and catchments. Soil loss under NT and CCNT was greatly reduced relative to GP and P on a slope of approximately three percent. Under an alfalfa (Medicaqo sativa) intercrop (SNT) soil loss was essentially stopped. Soil samples from F90 in April 1986 show the long-term impact of tillage system on the accumulation of organic matter as measured by total carbon content. Where no tillage had been performed for five years carbon contents 65 were higher than in continually tilled soil in all treatments. The data reflects not only the buildup of residue from the corn crop but also the rye cover crop in the CCNT and the additions of manure where it was applied. Soil samples from the 0-1 cm depth, indicate that CCNT and NT generally had significantly higher carbon content than P and CP in Manure and Man-Irr treatments (Table 20). In the non-manured treatments carbon content is more than twice as great in NT soil as P, but the differences are not significant. Carbon content at a depth of 1-5 cm was affected somewhat less by tillage system (Table 21). Though CCNT and CP still tended to have higher values than P and NT the differences were largely nonsignificant. 66 Table 20. Soil carbon: Site F90, April 1986; 0-1 cm depth. Treatment -1 9 k9 Tillage Control Manure Irr1g Man-Irr CCNT 16.6a’ 24.7a 15.9a 30.8a NT 13.0a 20.0ab 11.7a 27.8a CP 11.0a 14.9bc 9.4a 14.8b P 7.3a 9.7c 7.0a 12.3b Means within columns followed by a common letter do not differ significantly at the 5% level as determined by the Duncan’s Multiple Range Test. # 67 Table 21. Soil carbon: Site F90, April 1986; 1-5 cm depth. Treatment -1 9 kg Tillage Control Manure Irr1g Man-Irr CCNT 10.0a# 11.2a 11.9a 13.7a NT 9.9a 11.0a 7.8a 11.3a CP 11.0a 11.2a 8.1a 13.6a P 7.6a 10.7a 7.3a 12.0a Means within columns followed by a common letter do not differ significantly at the 5% level as determined by the Duncan’s Multiple Range Test. # 68 D3. SOIL TEMPERATURE In 1981 and 1982 soil temperature was measured using dial thermometers with rigid metal probes. The automatic data logging system employed after 1982 is considered to have provided more reliable information, so data from those years will be discussed here. When daily high soil temperatures for the NT and P systems are compared, it is found that manure on untilled soil kept daily high temperatures at depths of 5.1 cm and 10.2 cm lower relative to Plowed soil on each of the days it was measured. In 1983 mid-afternoon soil temperatures measured in NT/ and P/Ma‘nure plots were significantly different 35 percent of the time at 5.1 cm and 29 percent of the time at 10.2 cm, Figures 7 and 8, respectively. In 1984 NT/Manure had significantly lower' mid-afternoon soil temperatures at 5.1 cm on 31 percent of the days temperature was measured (Figure 9) and 19 percent of the time at a depth of 10.2 cm (Figure 10). In 1983 soil temperature in NT/ and P/Controls differed significantLy 59 percent of the time at 5.1 cm (Figure 11) and 24 percent at 10.2 cm (Figure 12). However, in 1984 soil temperatures were much less variable in Control plots with only two significantly different measurements at 10.2 cm. At 5.1 cm, NT and P soil temperatures were significantly different 19 percent of the time and only 69 0:3:02\om....ll£003 Eo Tm 0.0 0:30:00E3 :00 :9: xzoo :00: nmmp S 0:39... OHUO 233.. 22.50 ><2 Fm ><2+N bin— >12: _ . . . P . ..6 W . 9 D 3 U j H mop W O E O H d ... o ... H o 9 ... o I J O O O O .. mw D 0 ... . l. O * * * . n ... ... ... \.I H0 H ... .ou nu . 9 . H r m . w e v .3 s . 0 C ... ...Z 0 304m * . ..on 7O 0:3:02\ommll£000 E0 NE 30 0:30:0qu0. :00 :2: >203 :00: fine .w 332... 300 23...: 23:0 >135 >13: >§ow P h p — _ _ .n W H a D H I u .9 1 . H . H I m .. w. . 1 d o 9 * 9 9 * * 0 . IJ ... *0... ... ... ..mw m. 0 ... m ... ... H . a . ) .ON 0 . 9 . 5 . m . 9 ....“ s r 3 . C E o . 30.... ... .on 71 0:3:02\m¢mmll5003 E0 To 0.0 0:30.800E3 :00 :9: .900 :00: .82 .m 0.59.1 GHUO 232: 2336 >§ON ><2 Pm ><2 3... ><2+N ><10— r h h h — _ In W . a D r U H H .2 m. e w m e e ... .e. a a H e T .m ... ... 0 J 0 mew @ ...... ... .9 m. @ ... . n o ... . J * ... * H . a 1 mm .ON a r m . J r % ... 1mm s . O r C #2 a r 30.... ... . [on 75 after May 23 (Figure 13). The reason for less significant variation in 1984 can probably be attributed to two factors. First, the gap between diurnal maximum and minimum atmospheric temperatures tended to be greater in 1983, especially in early to mid May. Low temperatures tended to be several degrees cooler in 1983 than in 1984. Secondly, the measurement site in 1983 was F90 which was in its third year of corn production while site F84B was second year corn in 1984. An extra year of residue buildup on F90 may have contributed to the larger frequency of lower temperatures for NT's in 1983. Hourly soil temperatures were measured in one rep of CCNT/ and P/Controls from 1983—85. In 1983 and 1984 several large gaps existed in the data due to datalogger problems. In 1985 continuous readings were collected for more than 6 weeks allowing calculations of cumulative degree-hours throughout the period of seedling emergence. Figure 14 shows daily accumulation of degree-hours at a depth of 5.1 cm based on a sample of 2 thermocouples per plot. The difference in total accumulation of 601 degree-hours was not significant (P<0.05). The small sample size was probably the major cause of the nonsignificance. At 10.2 cm, where there were three thermocouples per plot, the Plowed soil accumulated 479 more degree-hours than the CCNT. This difference was significant (P<0.05) as shown in Figure 15. 76 _o€oo\m¢m.._||£%v :8 E 9 232852. =8 £2; £2. :82 £2 .2 22E 8.00 22.2 22.3 >523 £28 5.2? >528 _ _ _ _ _ .m H .e. ..2 h 6 r H ... ... .2 a . G 6 fl * . 0 I H ... ... o m a e .ou * v e . G 0 .umN o ... ... ... . * won ...2 0 . 304.". * h .3 (‘3 399.1690) elnioJaduJal uoaw 77 Show So fin #0 .9550 m¢mu E mtaoslootmoo «>32:an mm? .1 8:2... 300 ZDBN 232.; , 2:30 ><2nN >36 P >330 ><1No b _ b b _ h h I can He a I a n D* u* oum* on** no** u n ** o * on * unnonouooonounnnononnon * * ** ******** ************** 29E * too a u can rooop roomp ..OOON . comm . coon . Donn SJnoH-anfiaq emolnumg 78 Lamb Eo NA: “0 .9350 m¢mu E mtaoclootmoo 028.:an mm? .9 959... Boo ZDBN 232.. F 2330 >522. ><2No _ _ _ - — _ _ D * DDUDDDDDDDUDDDDDDDDDDDD *********************** 304n— * ...200 D 10 I com .02: rcom— . OOON I comm - oocn r Donn SJnoH—eeraq 9Ano|num3 79 D4. BOIL MOIBTURE Spatial variability of soil horizons was an important factor in the precision and interpretation of the neutron probe readings from all three study sites. This was especially true in and below the clay loam B horizon. The thickness and texture of the B horizon changed rapidly from point to point in all three study sites causing varying water holding capacities. This heterogeneity is indicated by coefficients of variation (CV) which tended to increase substantially as the depth of readings increased. Nonetheless improved soil. moisture. conservation. under no-till systems was commonly observed throughout this study. In 1983 (F84A) readings began at a depth of 30 cm and, as Figure 16 shows, soil moisture content in the F84A Control treatment was significantly greater in NT and CCNT than in the P and CP sytems throughout the latter part of the growing season. In 1984 (F84A) and 1985 (F843), when readings began at 15 cm, tillage-related differences in soil moisture content were also common in the Control treatment. Measurements from F843 (1985) show significant moisture conservation in zero-till and ridge till systems at both 15 cm (Figure 17) and 30 cm (Figure 18) especially in the second half of the growing season. The impact of surface residue in reducing soil moisture evaporation is evident in all these cases. 80 nmmellfiooo E0 on yo _obcoo (+9. to“— 3:52.: 305 cobaoz 6.. 9.39... 9.8 .39;me 390350 nomfiaw—o 3322.5 _ p . . _ . . p — ...O.O 5.: ... E o no a #28 n_ . ..o \. .Nd /-\ /-\ HW/WF H c y rnd (fix/6x) iueiuoo aJnlSpUJ nos 81 mDOFIILuQOU E0 0F #0 _Ob.COO m¢mh_ 50% mmcfivom... ODOLQ COT—H.302 .Nuw OLJOE mum Kunm— _ . mmm 532.2. P goo mom—4:10P . r . now 233.. _ + b mow «>33 P u — ... coo moon; + 5 o 30.... ... no 4 58 o r to . n6 (fix/6x) iueiuoo eJnlS!OLU uos 82 mmm—llfiaoo E0 on go .9300 m¢mu to; mucfioou onota cobaoz .mw 830E 8.00 now Emma mom Snap new 333. new 533.. now P>25 micron range than NT and not also have significantly more total porosity. CP was sampled for pore-size distribution only in 1985 and for no pore-size category did CP significantly vary from Plowed soil at probability levels of 0.01 or 0.05. Figures 23-32 present pore-size distributions for all 10 samplings. These graphs show pore sizes >25 microns summed together, with the exception of 1982 where the -5.88 kPa tension was missing from the analysis. The pore size distribution analyses which included the -5.88 kPa tension (1983-1985) show that, in all cases, NT had less than 10% porosity in the >25 micron range. Samples from P approached a low of 10% in 1983 and 1984 when cores were taken in July. Table 23 lists the mean bulk densities determined from intact soil cores taken from each site from 1982 to 1985. The June samples of 1982 and 1985 all produced significant differences in bulk density between P and NT. In 1983 and 1984, when samples were taken in July, the bulk density of P had increased relative to the June samplings of 1982 and 1985. Consequently only 2 of 6 samplings produced significant differences in bulk densities in 1983 and 1984. As above, the CP was sampled only in 1985 and was comparable 91 um? I. 8:3.me 6% 88 om... .mm 839.. AmcotoEc moN.m Boa .6 mocow. n. ..v 0 To. F 0.79 a: .E n. ...z m ...z n. ...z n. .J I fill. .00 —|I—- . m. H Lo m .3. S «M... ) w :0 C. . / .No w C. ( H Lrl fi . .3... «0.0 cm:— 883 00.0 00.. 88 [Md 92 mm? In 8:3.sz 6% 88 om. cum 8:9... Amcotottv mow? Boa .6 omcom mév nulm... 0? E m E m E a . ..I ll .00 I. d 3 m . o s m... r ) m C. . / .No w C. ( .nd 93 $2 In 8.39%... «um 88 om... .mm 839.. Amcotoftv mow? Soc .0 3:3. 0. «v nulm... ...z n. ...z .filll n. ...z nun m no.0 004 It . 0.0 . —.0 .. Nd (Q w/E w) Kigsomd 0.3 ' 1 V///////////////////////// III—NI I P NT OP >25 mm q d d 0.2 ‘ 0.0 0.1 ($3 w/C w) Kigsmod P NT OF P NT OP <4.4 4.4-25 Range of pore sizes (microns) Figure 26. F90 pore size distribution —- 1985 95 S? i 8.59%... mum 88 <8... .R 8:9... Amcotofc mo~.m 20a .8 macaw. n. —v n ..lmé m¢lmw 0+5 ...2 n. ...z n. ...z a ...z n. ll ] . N.0 ( S.‘ w/Q w) Kigsmod «0.0 and it: .. 0.0 96 mm... .... 8.59%... £9 88 in... .mu 8:9. Amco.o.Ev mo~.m Son .6 omcom m. Fv mulm. F DNA ._.2 n. ...z n. ...z n. ..IIJ 0.0 d a 3 m 0 .0 m... ) m C. . / no m C. x I(\ o«.0 004 a 0.0 97 $2 i 8.39%... 0% 88 <3: .mm 8:9... Amco..o.Ev mofim 0.0.. .5 mocom m. Fv lem. F 0N5 ...z m ...z n. ...z n. .1Il a 0.0 r F.O F «.0 ( 2 w/Q UJ) Kigsomd . n.0 98 32 i 8:8.me £8 88 mew... .0... $8.... Amco..o.EV mo~.m 20a Fo mocom m. Fv anm. F man ...2 n. ...z m ._.z n. .J - . 0.0 d :9 m 0 S (M... r ) m C. / . «.0 w C. ( . n.0 99 9mm. i 8.8.8... 3.. .8. me... .3. .89... Amco..o.Ev mo~.m Boa ..o omcom 0. Fv mulm. F mun ...z n. ...z n. ._.z n. .i w 0.0 I d .... m . o s W. ) m C . / .3... .N0 m C. ( _.i H «0.0 004 It! 00 . 0 004 it 3* u ”.0 100 mm... i 8.8%... MwN.m 88 me... .Nm 2.6... Amco..o.Ev mofim 9.0.. ..o 09.6w. .v..vv 0Nl¢..v mNn no .5 n— ...0 ...z n. H (2 LU/c LU) Mismod .... ... ... . I .88... u ”.0 101 Table 23. Bulk density in intact soil cores: 0—7.6 cm. Year Tillage 1982 1983 1984 1985 3 -3 m m Location F90 Plow l.33b$ 1.58a 1.43a 1.37b No-tillage 1.58a 1.60a 1.51a 1.56a Chisel plow NA NA NA 1.37b p level 0.05** 0.01 Location F84A Plow 1.30b 1.383 1.35b NA No-tillage 1.53a 1.51a 1.51a NA p level 0.01 0.05 Location F84B Plow NA 1.47a 1.41b 1.36b No-tillage NA 1.54a 1.56a 1.55a Chisel plow NA NA NA 1.33b p level 0.01 0.01 $NA=site not sampled. **Means followed by the same letter do not differ signifi- cantly at the level given following each column. Mean separation by LSD. 102 to the moldboard plowed soil. Generally, the bulk density of NT plots was quite high with values often near 1.60 g/cm3. Samples from P showed favorable bulk densities when sampled in June and, in most cases, in July as well. One exception was in F90 in July 1983 when mean bulk density of P was 1.58 g/cm3 and nearly equal to NT. D6. PLANT POPULATIONS Plant population as determined at harvest was one of the more variable factors measured. The causes of this variability were essentially the same as those detailed previously in the Seedling Emergence Rate section. Planter-soil interactions influencing seed placement and coverage, invertebrate pest problems, and the expected influences of treatment induced ground cover distribution all had a major impact on harvested plant populations. Achieving optimum plant stands was a problem throughout this project, especially with the corn planter used from 1981 to 1984. The Model #4500-AAS Buffalo corn planter used during that period was extremely difficult to calibrate and had an inferior drive system which was susceptible to slippage and clogging with residue so that seed was probably not always distributed equally in all tillage systems. Clogged seed units adversely affected seed placement and 103 seed-soil contact. These factors led to uneven stands and high seed mortality. For example in F90, where all treatments were planted each year at the rate of 73,900 seeds ha-l, the average plant count at harvest for all years excluding 1983 was only 53,300 plants ha"l giving an apparent seed mortality of approximately 28%. Though seed placement was no doubt a factor, it is likely that not as much seed was planted as calibrations indicated. In 1983 a planter calibration error led to higher than desired populations in all three study sites. Time was allowed for thinning of plants only in F90. Table 24 shows the harvested plant populations in F843 as affected by tillage system. Generally populations ranged from 81,500 to 93,900 plants ha-l. Plant counts in F84A yielded similar results. In F90, where thinning was performed, populations averaged a uniform 70,400 to 74,100 plants ha-l. Plant populations in F90 from 1981 show that even when stands were nominal in some treatments wide variation across a site was still common (Table 25). The mean plant population, averaged over all treatments, was 60,900 plants -1 1 ha for NT and 52,300 plants ha- for P. Despite this difference there was no significant variation in grain yield between these systems. Populations in CP however were very low and variable ranging from a mean of 29,400 plants ha-1 1 for the non-manured treatments to 46,100 plants ha- in the Table 24. Plant populations at harvest: F848, 1983. Treatment -l plants ha Tillage Control Manure Irrig Man-Irr NT 81500as 93900a 86SOOab 91400a CCNT 79000a 86500a 88900ab 81500a Plow 84000a 81500a 86500ab 840006 CP 76600a 84000a 79000b 86500a RCNT 88900a 88900a 93900a 96300a § .............................................. 104 Means within columns followed by a common letter do not differ significantly at the 5% level as determined by the Duncan’s Multiple Range Test. 105 Table 25. Plant populations at harvest: F90, 1981. Tillage Control NT 64200as CCNT 61800a Plow 52600a CP 27900b SNT 53100a $ Treatment -1 plants ha Manure Irrig 56800ab 62500a 57600ab 60500a 52600ab 51400a 46400b 30900b 61300a 62500a 60000ab 55600ab 52600ab 45700b 60000a Means within columns followed by a common letter do not differ significantly at the 5% level as determined by the Duncan’s Multiple Range Test. 106 treatments with manure applied. The most likely explanation is that the planter drive system was slipping in the less dense, tilled soil of CP and P causing fewer seeds to be planted. There also appeared to be some surface crusting in the CP which inhibited emergence. As Table 26 shows, uniform stands of desirable density were also achieved at times during this study. At site F90 in 1985 there were no significant differences between tillage systems in any of the four treatments. D7. GRAIN YIELDS Grain yields of SNT and RCNT were extremely poor during most of the years of this study. In fact, these treatments were often abandoned at midseason as complete crop failures. The discussion will therefore focus on CP, P, NT, CCNT and, for 1985, the RT system. All grain yield data available, including SNT and RCNT, will be presented. Grain yields from F90 in 1981 (Table 27) were the highest of any obtained. Following alfalfa in rotation and generally optimum plant populations were the primary reasons for this. FTecipitation was light and poorly dispersed during the period from mid—June to mid-July or non-irrigated yields may have been even higher. Treatment means of 12,730 1 1 kg ha- for NT/Irrigated and 12,605 kg ha- for P/Man-Irr 107 Table 26. Plant populations at harvest: F90, 1985. Treatment -1 plants ha Tillage Control Manure Irrig Man-Irr CCNT 605003$ 583003 561003 590003 Plow 576003 538003 551003 546003 NT 573003 590003 588003 580003 CP 556003 563003 553003 578003 § .............................................. Means within columns followed by a common letter do not differ significantly at the 5% level as determined by the Duncan’s Multiple Range Test. 108 Table 27. Mean grain yields: Site F90, 1981. Treatment kg ha-1 Tillage Control Manure Irr1g Man-Irr CCNT 74623b$ 85293 118523 109123 Plow 84033 89053 121033 126053 NT 80903 87173 127303 117893 CP 5518b 84663 8090b 111003 SNT 69613b 88423 117893 119783 Means within columns followed by a common letter do not differ significantly at the 5% level as determined by the Duncan’s Multiple Range Test. 109 were exceptional. Poor stand was likely the cause of the low yield in CP/Control. Dryland yields in 1982 were higher at site F90 than in 1981 (Table 28). A season-long, uniform rainfall pattern overcame any yield depressing effect of second-year corn. Yields were generally down in the irrigated treatments. CP yielded much better in 1982, regardless of treatment, due to desirable plant populations. First-year corn yields in F84A were not as high as first-year yields in F90 but were respectable, especially for Control and Manure treatments (Table 29). This was again due to favorable rainfall patterns. As discussed above, 1983 .was the year where a miscalibrated planter caused very high populations at all sites. It was also a year where the months of June to August were drier than normal. Consequently, irrigated treatments yielded significantly higher than nonirrigated in all cases. No significant differences between tillage methods were measured in F90 or F84A (Tables 30-31). Within treatments, mean yields for P were generally the lowest and, in the case of F84B (Table 32), the difference was often significant. In 1984 the weather was generally hot and, especially in the months of June and August, dry. This probably had a negative impact on all grain yields (Tables 33-35). Significant tillage-related differences in grain yields were 110 Table 28. Mean grain yields: Site F90, 1982. Treatment kg ha'1 Tillage Control Manure Irrig Man-Irr CCNT 9156as 6585a 9532ab 7901b Plow 9532a 10532a 11162a 12103a NT 9971a 9657a 10723a 10723a CP 9532a 10723a 11037a 11413a RCNT 4954b 4954b 7274b 8090b § .............................................. Means within columns followed by a common letter do not differ significantly at the 5% level as determined by the Duncan’s Multiple Range Test. Table 29. Mean grain yields: Site F84A, 1982. Treatment kg ha-1 Tillage Control Manure Irrig Man-Irr CCNT 84033bs 88423 88423b 99083 Plow 9344a 8717a 8968ab 9218a NT 87173b 85293 91563b 95323 CP 92813 94073 96573 100343 SNT 7400b 82783 7713b 85293 RCNT 86543b 82153 97833 97833 § .............................................. Means within columns followed by a common letter do not differ significantly at the 5% level as determined by the Duncan’s Multiple Range Test. 111 Table 30. Mean grain yields: Site F90, 1983. Treatment kg ha'1 Tillage Control Manure Irrig Man-Irr CCNT 633433 65853 89053 89683 Plow 49543 57073 95323 91563 NT 64593 63963 100343 95953 CP 53393 67733 91563 95323 § .............................................. Means within columns followed by a common letter do not differ significantly at the 5% level as determined by the Duncan's Multiple Range Test. Table 31. Mean grain yields: Site F84A, 1983. Treatment kg ha'1 Tillage Control Manure Irrig Man-Irr CCNT 70243$ 65853 100973 96573 Plow 58323 58953 92813 93443 NT 67103 64593 97203 94693 CP 62713 63963 93443 93443 § .............................................. Means within columns followed by a common letter do not differ significantly at the 5% level as determined by the Duncan's Multiple Range Test. 112 Table 32. Mean grain yields: Site F848, 1983. Treatment kg ha-1 Tillage Control Manure Irrig Man-Irr CCNT 627133 73373 99713 97203b Plow 3637b 4891b 8090b 8591b NT 62083 61463b 103473 92813b CP 66473 65853 104733 105983 RCNT 50173b 58323b 102843 98453b Means within columns followed by a common letter do not differ significantly at the 5% level as determined by the Duncan’s Multiple Range Test. Table 33. Mean grain yields: Site F90, 1984. Treatment kg ha-1 Tillage Control Manure Irrig Man-Irr CCNT 31983s 35123 5518b 5957b Plow 30103 35123 79643 90933 NT 29473 35123 64593b 6459b CP 34493 3637a 7462a 8152a Means within columns followed by a common letter do not differ significantly at the 5% level as determined by the Duncan’s Multiple Range Test. 113 Table 34. Mean grain yields: Site F84A, 1984. Treatment kg ha’1 Tillage Control Manure Irr1g Man-Irr CCNT 31363s 37633 64593 74003 Plow 28853 29473 74003 75883 NT 33243 30733 63343 67103 CP 32613 36373 72743 76513 Means within columns followed by a common letter do not differ significantly at the 5% level as determined by the Duncan’s Multiple Range Test. $ Table 35. Mean grain yields: Site F84B, 1984. Treatment kg ha-1 Tillage Control Manure Irrig Man-Irr CCNT 2947a$ 3574a 7024a 6835a Plow 31363 28853 69613 81523 NT 27593 29473 78393 72743 CP 33243 50173 77763 82153 Means within columns followed by a common letter do not differ significantly at the 5% level as determined by the Duncan’s Multiple Range Test. 114 found only in the irrigated treatments of F90. 1985 was the wettest growing season experienced during this study with 38.8 cm of rainfall from May through August. Yields at site F90 were very good in the nonirrigated treatments but there were significant tillage effects (Table 36) . Irrigated and Man-Irr treatment means were more uniform but lower than most other years; no doubt showing the impact of five years of continuous corn. Essentially the same results were obtained in F84B, however yields were low in the Control treatments due to some very poor stands (Table 37). RT was the highest yielding tillage system in all treatments. The major objective of this study was to see which of the reduced tillage systems would, over several years, produce grain yields that growers are accustomed to obtaining on this particular soil using conventional tillage. The intercrop systems performed poorly due mainly to competition between the corn and legume crops for water and light and severe problems with weed control. However, the other systems; P, CP, NT and CCNT, performed comparably when viewed over the duration of this study. A combined analysis of variance was performed using CP, P, NT and CCNT because data was available for all site-years for only these systems. The analysis was by site and combined over years. The results of that analysis are shown in Tables 38-40 for sites F90, F848 and F84A, respectively. 115 Table 36. Mean grain yields: Site F90, 1985. Treatment kg ha-1 Tillage Control Manure Irr1g Man-Irr CCNT 9156a$ 8591a 82153 8654a Plow 77133b 79643 85293 89683 NT 80903b 88423 90933 82783 CP 7212b 94073 79013 89683 Means within columns followed by a common letter do not differ significantly at the 5% level as determined by the Duncan’s Multiple Range Test. Table 37. Mean grain yields: Site F848, 1985. Treatment kg ha'1 Tillage Control Manure Irrig Man-Irr CCNT 5581bcs 7086b 80893 79013 Plow 5393bc 6898b 8089a 8968a NT 6647b 7086b 80893 82783 CP 48290 7525b 70863 87793 RT 82783 92183 85913 89683 Means within columns followed by a common letter do not differ significantly at the 5% level as determined by the Duncan's Multiple Range Test. 116 Table 38. Combined analysis of grain yields: Site F90. Source DF’ MSs F Year 4 59750 4.98 * Rep(Year) 15 672 -- Irrig 1 109113 9.11 * Year*Irrig 4 10145 12.78 *** Irrig*Rep(Year) 15 884 -- Manure 1 3571 1.14 Ye3r*M3nure 4 517 0.76 Irrig*Manure 1 810 0.70 Year*Irrig*Manure 4 290 0.61 Irr*Man*Rep(Year) 30 488 -- T111 3 2741 0.47 Year*Till 12 2418 3.53 ** Irrig*Till 3 1613 5.36 ** Manure*Till 3 2668 4.63 ** Year*Manure*Till 12 577 1.91 Year*Irrig*Till 12 301 1.56 Year*Irr*Man*Till 15 193 0.93 Irr*Man*Till*Rep(Year) 180 207 -- 1‘DF=Degrees of freedom. sMS=Mean Square. *** = F test significant at 1% level. ** = F test significant at 5% level. *= F test significant at 10% level. 117 Table 39. Combined analysis for grain yields: Site F84B. Source DF‘ MSs F Year 2 26079 3.12 Rep(Year) 9 634 -- Irrig 1 127051 15.64 * Ye3r*Irrig 2 6544 5.82 ** Irrig*Rep(Year) 9 1344 -- Manure 1 3701 1.29 Year*Manure 2 1009 7.59 * Irrig*Manure 1 1349 21.08 ** Year*Irrig*Manure 2 64 0.26 Irr*Man*Rep(Year) 18 255 -- Till 3 1732 0.65 Year*Till 6 1800 8.53 ** Irrig*Till 3 439 3.09 Manure*Till 3 817 3.42 * Year*Manure*Till 6 239 1.68 Year*Irrig*Till 6 142 0.84 Year*Irr*Man*Till 9 170 0.96 Irr*Man*Till*Rep(Year) 10 177 -- ‘DF=Degrees of freedom. sMS=Mean Square. *** = F test significant at 1% level. ** F test significant at 5% level. * F test significant at 10% level. 118 Table 40. Combine analysis for grain yields: Site F84A. Source DF’ MSs F Year 2 68768 5.25 Rep(Year) 9 1220 -- Irrig 1 76241 6.06 Year*Irrig 2 12583 17.19 *** Irrig*Rep(Year) 9 951 -- Manure l 239 0.85 Year*Manure 2 244 1.11 Irrig*Manure 1 188 1.92 Year*Irrig*Manure 2 98 0.32 Irr*Man*Rep(Year) 18 448 -- Till 3 286 2.58 Year*Till 6 248 0.69 Irrig*Till 3 153 0.65 Manure*Till 3 90 0.63 Year*Manure*Till 6 144 0.61 Year*Irrig*Till 6 236 10.73 *** Year*Irr*Man*Till 9 22 0.14 Irr*Man*Till*Rep(Year) 108 161 -- # $ DF=Degrees of freedom. akin! ** * MS=Mean Square. F test significant at 1% level. F test significant at 5% level. F test significant at 10% level. 119 The tillage main effect was never found to be significant in any of the three sites. The Year*Tillage interaction was significant (P < 0.05) in F90 and F84B. In F90 the Irrigation*Tillage and Manure*Tillage interactions were also significant at the I>‘< 0.05 level. What this means is that tillage itself was not a significant factor in determining grain yields but that, in some cases at least, individual tillage systems were reacting differently depending' upon the year, manure applications and/or irrigation inputs. The main effect of Manure was not significant for any of the sites. Irrigation was significant in F90 and F848 but only at the I><< 0.10 level. In F84A irrigation was applied only in two of the three years due to pump problems in the initial season and this likely the major reason for lack of significance at this site. Not suprisingly the Year*Irrigation interaction was significant for all sites. The improvement of grain yields under irrigation, relative to nonirrigated treatments, is dependent on the amount of rainfall received in a given year and therefore it would be expected that this interaction would be significant if a variety of weather conditions had been encountered. Because of the significance of several of the interaction terms involving 'Year' it is not appropriate to average treatment means over years for mean separation analysis, however for discussion purposes that information 120 is still useful. Table 41 lists grain yield treatment means for F90 averaged over 5 years. Tables 42-43 contain the same for F84A and F84B, respectively, both averaged over three years. Table 44 lists treatment means averaged over all years and sites. Each of these means is determined from a sample size of 44. None of the four tillage systems stand out as superior. Though occasionally significant variations in yields occurred between the tillage systems within years, total grain production over years did not vary much between these four basic tillage systems. The key appears to be obtaining good plant populations and controlling pests, primarily slugs, in the zero-till systems, and weeds. 121 Table 41. Mean grain yields: Site F90; Years 1981-1985. Treatment kg ha'1 Tillage Control Manure Irr1g Man-Irr CCNT 7086 6773 8842 8466 Plow 6710 7337 9845 10410 NT 7086 7713 9845 9407 122 Table 42. Mean grain yields: Site F84A; Years 1982-1984. Treatment kg ha-1 Tillage Control Manure Irrig Man-Irr CCNT 6208 6396 8466 8905 Plow 6020 5895 8717 8842 NT 6271 6020 8278 8591 CP 6271 6522 8717 9030 Table 43. Mean grain yields: Site F84B. Years 1983-1985. Treatment kg ha“1 Tillage Control Manure Irr1g Man-Irr CCNT 4954 6020 8340 8152 Plow 4076 4891 7776 8591 NT 5205 5393 8779 8340 CP 4954 6334 8466 9156 123 Table 44. Mean grain yields combined over sites and years. Treatment kg ha-1 Tillage Control Manure Irrig Man-Irr CCNT 6271 6459 8591 8529 Plow 5832 6271 8968 9469 NT 6334 6647 9156 8905 CONCLUSIONS In five years this study developed a great deal of information pertaining to the effect of reduced tillage on corn production on a Kalamazoo loam soil. Competitive grain yields can be achieved on Kalamazoo- OSthemo soils with the following tillage systems: CP, NT, CCNT and P. The key to high production appears to be the assurance of optimum plant populations. Soil conditions at planting and correct planter adjustment are critical. RT has been studied for only one year but looks very promising and warrants further investigation. The legume intercrop systems, SNT and RCNT, were very difficult to manage and were not successful. Weed control, and interspecific competition for light and moisture were the main reasons for this failure. Some specific conclusions can be drawn from the yield data on the relative effectiveness of irrigation and manure: 1) Irrigation improved yield in the range of 1880 to 3140 kg ha"1 during a period of years where a variety of rainfall patterns were experienced; 2) Based on the combined site—year' averages in 'Table 35, manure applications increased yields within tillage systems from 190-1130 kg ha-1 in nonirrigated corn; 3) For irrigated systems (Irrig vs. Man-Irr), yield was not increased for CCNT and NT when manure was applied. This was likely due in part to 124 125 increased invertebrate pest pressure, especially Deroceras reticulatum early in the growing season, caused by heavy residue and moist conditions; 4) For CP and P yield was increased an average of 500-750 kg ha"1 when manure was applied to irrigated plots. An economic analysis of the yield increases due to irrigation may be useful. After experiencing a variety of rainfall patterns it appears that average yield increases for some of the treatment combinations may not justify the cost of irrigation over the long term. This is especially likely when manure is available as a management option on zero tillage systems. The often less than optimum plant populations experienced at times during the study may have had negative impact on irrigated grain yields also. Measurements of the extent of ground cover showed that residue buildup in no-till systems should provide significant protection from erosion on moderate slopes. Qualitative measurements of soil loss on a sloping area of F90 bear this out. When manure is applied to no-till systems about 90% ground cover is attained after planting. The differential residue buildup between tillage systems resulted in significantly different soil carbon contents in the top centimeter with CCNT and NT higher than P regardless of manure and irrigation treatment. Irrigation also affected carbon content of the top centimeter in NT and CCNT. 126 Some concern may be warranted about high surface bulk density levels and low amounts of large pores (>25 microns) in the NT and, in some cases, P. These parameters are such that aeration could become limiting in periods of high soil moisture content. Long term trends in soil physical properties have not appeared, however our soil sampling schedule was not intensive. Soil temperature was lower at depths of 5.1 and 10.2 cm when tillage was reduced. This often appeared to slow seedling emergence by several days but this condition was not lasting and did not appear to affect grain production. Soil moisture was positively affected by surface residue in reduced tillage systems to a depth of about 30 cm. Lower evaporation from no-till systems often appeared to reduce the need for plants to withdraw water from depths of 61-76 cm. This study has provided some good background information on the effects of a variety of tillage methods on corn production on the well-drained Kalamazoo loam. Finally it shows that conservation tillage methods can work very well on this soil and should be adopted wherever possible. BIBLIOGRAPHY BIBLIOGRAPHY Al-Darby, A;M. and B. Lowery. 1986. Evaluation of corn growth and productivity with three conservation tillage systems. Agron J. 78:901-907. Allmaras, R. R., W. C. Burrows, and W. E. Larson. 1964. Early growth of corn as affected by soil temperature. Soil Sci. Soc. Am. Proc. 28:271-275. Austin, F.R. 1979. Soil Survey of Kalamazoo County, Michigan. United States Department of Agriculture, Soil Conservation Service. Bauer, A. and A.L. Black. 1981. Soil carbon, nitrogen and bulk density comparisons in two cropland tillage systems after 25 years and in virgin grasslands. Soil Sci. Soc. Am. 45:1166-1170. Blake, G.R. and K.H. Hartge. 1986. Bulk density. A. Klute (ed.) 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The effect of tillage on soil temperature and corn (Zea mays L.) growth in Manitoba. Can. J. Plant Sci. 64:59-67. "I111111111111111‘TS