"‘ V'v-vav- 3-... .313 ’1‘. (iii. .15.... at. v. 1:. 3.2.1; 3:53:51. :13... ‘31:}. .1 I... . {.02. 33.1%... 2...: S 2 .1, 9.9:: ‘33:)..5 I: 1‘52... 1 531.22.... : .E::.«.:§q..r .n? .1..:.:y7¢. .I it mass 2. LIBRARY J on? Michigan State University This is to certify that the dissertation entitled COVER CROP AND SOIL AMENDMENT EFFECTS ON CARBON SEQUESTRATION IN A SILAGE CORN - SOYBEAN CROPPING SYSTEM presented by Bradley Eric Fronning has been accepted towards fulfillment of the requirements for the Ph.D. degree in Crop and Soil Science Afléfi Major I5rofessor s Signature 42/ x/ 053 I U] Date MSU is an Afiirmative Action/Equal Opportunity Employer PLACE IN RETURN BOX to remove this checkout from your record. To AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE 5/08 KlProj/AccaPres/CIRCIDateDue indd COVER CROP AND SOIL AMENDMENT EFFECTS ON CARBON - SEQUESTRATION IN A SILAGE CORN - SOYBEAN CROPPING SYSTEM By Bradley Eric Fronning A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY CROP & SOIL SCIENCES 2008 ABSTRACT COVER CROP AND SOIL AMENDMENT EFFECTS ON CARBON SEQUESTRATION IN A SOYBEAN - CORN SILAGE CROPPING SYSTEM By Bradley Eric Fronning Decline of soil organic carbon (SOC) in agricultural systems combined with increased awareness of the importance of the terrestrial ecosystem in a global carbon budgets has stimulated evaluations of land management effects on soil C dynamics and storage. Past and present farming practices have led to an estimated loss of 4 d: 1 Mg of carbon from soils of the United States. In this project we investigated the effectiveness of winter rye as a cover crop, fresh manure, and composted manure as potential methods to sequester atmospheric carbon in the soil. This research was repeated over three years at two locations; East Lansing (N 42.43, W 84.28) and Chatham (N 46.29, W 86.76). The two locations allowed for analysis of latitude effects. Compost treatments increased SOC the most at East Lansing followed by manure treatments. There were no differences in SOC accumulation at Chatham. Compost had a lower annual flux of greenhouse gases from the soil under both rotations at East Lansing, compost was also the lowest at Chatham when applied to continuous corn. Compost, manure, compost + rye, and manure + rye all had negative global warming potential (GWP) while rye alone and the untreated were net emitters of GHG at East Lansing. Continuous corn — compost was the only treatment at Chatham that had a negative GWP. ACKNOWLEDGEIVHENTS The author wishes to express his thanks and appreciation to his major adviser, Dr. Kurt Thelen, for his encouragement and support. Dr. Thelen provided the right amount of guidance and direction to help me become a better student and researcher. Special thanks to Drs. Kells, Min, Kravchenko, and Difonzo for their guidance and input on the research and thesis. A special thanks to Dr. Kravchenko for her help with data analysis. Additional thanks to Bill Widdicombe and Keith Dysinger for theirtechnical assistance, humor, and all the fun-filled trips across Michigan. To all the undergraduate assistants that helped on this project, thank you. To my fellow graduate students, I would like to extend sincere thanks for your friendship, help, advice, and the experiences that we all shared together. Time goes by to fast when you are surrounded by good people. Finally, I wish to give my deepest thanks to my parents, Lee and Cindy Fronning, and to my brothers, Rob and Scott, for their continuous guidance, caring, and support throughout my life. Without them, achieving this goal would not have been possible. iii TABLE OF CONTENTS LIST OF TABLES ................................................................................... v CHAPTER 1 COVER CROP AND SOIL AMENDMENT EFFECTS ON SOIL ORGANIC CARBON IN SILAGE CORN — SOYBEAN CROPPING SYSTEMS Introduction ......................................................................................... 1 Material and Methods ............................................................................ 9 Results and Discussion .......................................................................... 13 East Lansing ................................................................................. 13 Chatham ..................................................................................... 20 Latitude effects .............................................................................. 22 Summary .......................................................................................... 23 Conclusions ...................................................................................... 24 Tables............' ................................................................................. 26 Literature Cited .................................................................................. 53 Appendix A: Appendix Tables ................................................................... 53 CHAPTER 2 COVER CROP AND SOIL AMENDMENT EFFECTS ON GREENHOUSE GAS FLUXES IN SILAGE CORN - SOYBEAN CROPPIN G SYSTEMS AT TWO DIFFERENT LATITUDES Introduction ........................................................................................ 59 Material and Methods ........................................................................... 61 ' Results and Discussion .......................................................................... 65 Ancillary measurements ................................................................... 65 Daily GHGFlux ............................................................................ 67 Total Annual Soil GHG Flux .............................................................. 72 Soil C GWP ................................................................................ 74 Residual carbon from organic inputs .................................................... 75 Input GHG flux ............................................................................ 76 Net GWP ..................................................................................... 77 Conclusions ........................................................................................ 78 Tables ................................................................................................ 79 Literature Cited ................................................................................... 96 iv Table 10. ll. 12. 13. 14. LIST OF TABLES Page . Dates of soil sampling, planting, herbicide application, and harvest at East Lansing and Chatham ................................................ 26 Dates of application and analyses of amendments at East Lansing .................... 27 Date of amendment application, rate and analyses at Chatham ........................ 28 ANOVA for bulk density of the 0-5 and 5-25 cm profiles of the corn — soybean — corn rotation (CSC) and soybean - corn - soybean (SCS) rotations ............................................... 28 . Main effect means for the soil bulk densities of the 0-5 and 5-25 cm profiles at East Lansing .......................................................... 29 Interaction means for bulk densities of the 0-5 and 5-25 cm profiles at East Lansing ............................................................................... 30 AN OVA for crop residue carbon inputs and total carbon © inputs for both CSC and SCS ...................................................................... 31 Carbon input from crop residue and total input .......................................... 32 ANOVA for SOC in the 0-5, 5-25, and 0-25 cm profiles of the CSC and SCS rotations ..................................................................... 33 Main effect means for SOC in the .0-5, 5-25, and 0-25 cm profiles as affected by soil amendments and rye cover crop at East Lansing in the CSC and SCS rotations .............................................................. 34 Interaction means for SOC (Mg/ha) in the 0-5, 5-25 and 0-25 cm profiles of the com-soybean and soybean-com rotations at East Lansing from the spring of 2002 to the fall of 2004 ..................................... 35 ANOVA for POM-C for both csc and scs rotations ................................. 36 Main effect means for POM-C in the 0-5, 5-25, and 0-25 cm profiles atEastLansing.................. ................................................................................. 37 Interaction means for POM-C ............................................................. 38 Table Page 15 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. ANOVA for TN in the 0-5, 5-25, and 0-25 cm profiles of the CSC and SCS rotations ...................................................................... 39 Main effect means for TN in the 0-5, 5-25 and 0-25 cm profiles as affected by soil amendments and rye cover crop at East Lansing in the CSC and SCS rotations .............................................................. 40 Interaction means for TN (Mg/ha) in the 0-5, 5-25, and 0-25 cm profiles of com-soybean and soybean-com rotations at East Lansing from the spring of 2002 to the fall of 2004 ............................................... 41 ANOVA for nitrate-N in the 0-5, 5-25, and 0-25 cm profiles of the CSC for SCS rotations ...................................................................... 42 Nitrate-N in the 0-25 cm profile as affected by soil amendments and rye cover crop at East Lansing in the CSC and SCS rotations .................... 43 Interaction means for Nitrate-N (kg/ha) in the 0-5, 5-25, and 0-25 cm profiles of corn-soybean and soybean-com rotations at East Lansing from the spring of 2002 to the fall of 2004 ............................................... 44 ANOVA for phosphorus in the 0-5, 5-25, and 0-25 cm profiles of the CSC and SCS rotations .............................................................. 45 Phosphorus in the 0-25 cm profile as affected by soil amendments . and rye cover crop at East Lansing in the CSC and SCS rotations... .... ............. 46 Interaction means for Bray-P (kg/ha) in the 0-5, 5-25, and 0-25 cm profiles of com-soybean and soybean-com rotations at East Lansing from the spring of 2002 to the fall of 2004 .............. . ................................. 47 Bulk Density of the 0-5 and 5-25 cm profiles at Chatham ............................. 48 Carbon added to the soil from cover crops, amendments, and crop residues at Chatham .............................................................. 48 SOC and nitrogen (kg/ha) in the 0-5, 5-25, and 0-25 cm profiles at Chatham from the spring of 2002 to the fall of 2004 ................................ 49 POM-C fraction of the 0-5 and 5-25 cm soil profiles at Chatham in the spring of 2002 and fall of 2004 .................................................... 50 vi Table Page 28. Nitrate-N and Bray-P (kg/ha) in the 0-5, 5-25, and 0-25 cm profiles 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. at Chatham from the spring of 2002 to the fall of 2004 ................................. 51 Average daily temperatures at East Lansing and Chatham, MI ........................ 52 Total monthly precipitation at East Lansing and Chatham, MI ........................ 52 Dates of soil sampling, planting, herbicide application, and harvest at East Lansing and Chatham ............................................................... 79 Date of manure and compost application, manure rates and analyses at East Lansing ............................................................................... 80 Date of amendment application, rate and analyses at Chatham ........................ 81 GHG flux from all inputs during crop production (adapted from West and Marland 2002; ) .................................................................... 81 Average daily temperatures at East Lansing and Chatham, MI .......................... 82 Total monthly precipitation at East Lansing and Chatham, MI ......................... 82 ANOVA for soil temperature and moisture at East Lansing ............................ 83 Main effect means for soil temperature at East Lansing ................................ 84 Main effect means for soil moisture at East Lansing .................................... 85 Soil temperature and moisture at Chatham ................................................ 86 ANOVA for soil GHG flux at East Lansing .............................................. 87 Main effect means for COz-C flux at East Lansing ..................................... 88 Interaction means for COz-C flux at East Lansing ......................................... 89 Main effect means for NZO-N flux at East Lansing ...................................... 90 Interaction means for N20-N flux at East Lansing ....................................... 91 Main effect means for CH4-C flux at East Lansing ...................................... 92 vii 47. 48. 49. 50. 51. A1. A3. A4. A5. A6. A7. A8. A9. Treatment means for NzO-N, COz-C, and CH4-C at Chatham in 2003 and 2004 ........................................................................... 93 Anova and main effect means for Soil C GWP, Res. C, Soil GHG flux, input GHG flux, and net GWP at East Lansing ........................ 94 Interaction means for Soil C GWP, soil GHG flux, input GHG flux, and net GWP at East Lansing and Chatham ......................... 95 ANOVA and main effect means for specific contribution of COz-C, NZO-N and CH4-C to total annual GHG flux at East Lansing ......................... 96 Means for specific contribution of C02, N20, and CH4 to annual GHG flux at Chatham ............................................................ 96 Winter rye cover crop biomass at East Lansing and Chatham ......................... 53 . Sidedress nitrogen rates at East Lansing and Chatham ................................. 53 Soybean biomass and seed yield at East Lansing and Chatham ........................ 53 Corn silage yield and quality analysis at East Lansing and Chatham .................. 54 SOC (%) in the 0-5 and 5-25 cm profiles of com-soybean and soybean-com rotations at East Lansing from the spring of 2002 to the fall of 2004 ............................................................................. 55 TN (%) in the 0-5 and 5-25 cm profiles of com-soybean and soybean-com rotations at East Lansing from the spring of 2002 to the fall of 2004 ............................................................................ 55 SOC and nitrogen (%) in the 0-5 and 5-25 cm profiles at Chatham from the spring of 2002 to the fall of 2004 ............................................... 56 Carbon:nitrogen in the 0-5, 5-25 and 0—25 cm profiles of com-soybean and soybean—com rotations at East Lansing from the spring of 2002 to the fall of 2004 ............................................................................... 57 Carbon:nitrogen in the 0-5, 5-25 and 0-25 cm profiles at Chatham in 2002, 2003 and 2004 ..................................................................... 58 A10. Nitrate-N (mg/kg) in the 0-5 and 5-25 cm profiles of com-soybean and soybean-com rotations at East Lansing from the spring of 2002 to the fall of 2004 ........................................................................... 59 viii A1 1. Bray-P (mg/kg) in the 0-5 and 5-25 cm profiles of com-soybean and soybean-com rotations at East Lansing from the spring of 2002 tothefallof2004................... ........................................................ 59 A12. Nitrate-N and Bray-P in the 0-5 and 5-25 cm profiles at Chatham from the spring of 2002 to the fall of 2004 .............................................. 60 A13. pH of the 0-5 and 5-25 cm profiles at East Lansing .................................... 60 A14. pH of the 0-5 and 5-25 cm profiles at Chatham ........................................ 61 A15. Carbon added to the soil from cover crops, manure or compost amendments and crop residue returned to the system ............................... 62 A16. Nitrate-N (mg/kg) in the 0-15, 15-30, 30-60, and 60-90 cm profiles of com-soybean and soybean-com rotations at East Lansing from the spring of 2002 to the fall of 2004 ...................................................... 63 A17. Bray-P (mg/kg) in the 0-15, 15-30, 30-60 and 60-90 cm profiles of com-soybean and soybean-com rotations at East Lansing from the spring of 2002 to the fall of 2004 ..................................................... 64 A18. ANOVA for nitrate levels in the 0-15, 15-30, 30-60, and 60-90 cm profiles of the CSC and SCS rotations ............................................... 65 A19. Nitrate-N (mg/kg) in the 0-15, 15-30, 30-60 and 60-90 cm profiles of com-soybean and soybean-com rotations at East Lansing from the spring of 2002 to the fall of 2004 ...................................................... 66 A20. ANOVA for phosphorous levels in the 0-15, 15-30, 30-60, and 60-90 cm profiles of the CSC and SCS rotations ............................... 67 A21. Bray-P (mg/kg) in the 0-15, 15-30, 30-60 and 60-90 cm profiles of com-soybean and soybean-com rotations at East Lansing from the spring of 2002 to the fall of 2004 ...................................................... 68 ix CHAPTER 1 COVER CROP AND SOIL AMENDMENT EFFECTS ON SOIL ORGANIC CARBON IN SILAGE CORN — SOYBEAN CROPPING SYSTEMS INTRODUCTION Decline of soil organic carbon (SOC) in agricultural systems combined with increased awareness of the importance of the terrestrial ecosystem in global corn budgets has stimulated evaluations of land management effects on soil C dynamics and storage (Lal et al. 1995). Past and present short sighted farming practices have resulted in loss of an estimated 4i1 x 109 Mg of carbon from soils of the United States, and 78i12 x 109 Mg from the world’s soils, a large fraction of which ended up in the atmosphere (Lal 1999). Soils play a major role in the global carbon budget not only because of the large amount of carbon stored in soil, with estimates ranging from 1395 to 1636x108 Mg (Post et al. 1992 in Torbert et al. 1999; Schlesinger 1984) but also because the annual flux of CO2 to the atmosphere from soil is 10 times the amount of CO2 contributed by fossil fuel usage (Post et a1. 1990). Soil serves as both a source and sink for atmospheric C02, therefore soil and crop management significantly affect the global balance of CO2. There is increasing evidence when soil management or land use is changed to reduce SOC loss or increase input carbon to the soil, loss of SOC can be reversed (J anzen et al. 1998b). Approximately one-third of the atmospheric C02 that has accumulated since pre-industrial times is derived from land use practices that involve soil disturbance and removal of vegetation (Grant et al. 2001). These losses indicate widespread soil degradation. Currently there is much interest in reducing these losses through land use practices that increase the sequestration of carbon in soils. Land use practices that may increase carbon sequestration include a switch to no-tillage (NT), greater cropping frequency (Bremer et al. 1994; Campbell et al. 1995), and application of organic amendments such as manure (Sommerfeldt et al. 1988) although J anzen et al. (1998a) regarded applications of carbon amendments as a carbon transfer rather than a gain. Many of these practices (manure, forage production, and reduced harvest removal) that favor carbon storage appear to interact synergistically with each other, so that increases in SOC under one practice are greater when combined-with other practices (Grant et al. 2001 ). SOC storage is a balance between carbon additions from non-harvested portions of crops and organic amendments, and carbon losses primarily through organic matter decomposition and release of respired C02 to the atmosphere (Huggins et al. 1998). Additions and losses of carbon are regulated by agricultural practices such as crop rotation (Janzen et al. 1992), residue and tillage management (Havlin et a1 1990), and fertilization (Bloom 1982; Paustian et a1. 1992). SOC changes can be attributed to crop species grown, cropping systems (including rotations), residue management practices, fertilizer applications, tillage practices, and other management factors (Havlin et al. 1990). Additional input of organic substances containing high amounts of carbon such as farmyard manure or the incorporation of crop residues will increase SOC content (Dersch and Bohm 2001). Root contributions are important to conserving or increasing SOC (Balesdent and Balabane 1996; Campbell et al. 1991; Solberg et al. 1998). Changes in SOC following implementation of a new management practice are dependent on climate, soil parent material, topography, biotic factors, and time. Conservation of SOC should be a goal in production agriculture to improve soil quality and decrease agricultural CO2 emissions. It is possible to conserve SOC through appropriate choices of cropping, tillage, fertility, and residue management systems. Such management of SOC would decrease agricultural CO2 emissions through reduced SOC decomposition, increased sequestering of atmospheric C, and reduced fossil fuel consumption (Robinson et al. 1996). TILLA GE EFFECTS ON SOC Tillage is used to mix and aerate the soil, and to incorporate soil amendments, cover crops, and crop residues into the soil. Soil incorporation of organic carbon has been associated with improvements in many soil physical, chemical, and biological properties, including improved porosity, microbial activity, and availability of plant nutrients (Logan et al. 1991). However, tillage exposes organic carbon in inter- and intraaggregate zones and that immobilized in microbial cellular tissues to rapid oxidation because of the improved availability of 02 and exposure of more decomposition surfaces (Crasswell and Waring 1972; Reicosky and Lindstrom 1993; Beare et al. 1994; Jastrow et al.1996). Losses of 40% or more of the SOC during a 60 yr period were realized with conventional tillage (Tiessen and Stewart 1983). Several researchers have shown increases in organic matter content, especially in NT systems as larger amounts of residue associated with increased crop yields are returned to the soil (Havlin et al. 1990; Rasmussen et al. 1980). NT cropping system accumulated on average 0.3 Mg/ha carbon annually in the Midwest United States (Franzluebbers and Steiner 2002). Increased carbon storage has frequently been observed in soils under conservation tillage, particularly with NT (Lamb et al. 1985; Unger 1991). Widespread adoption of conservation tillage could result in net increases in carbon sequestration in agricultural lands, reversing the decline caused by intensive tillage practices used for decades (Kern and Johnson 1993). Conversion of land from plow tillage to long-term NT management has a positive influence on the quality of agricultural soil (McCarty and Meisinger 1997; McCarty et al. 1995). Soil properties rapidly change during transition from plow— to NT management with much of the character of NT soil developed within the first 3 yr of NT . treatment (McCarty et al. 1998). Soil under long-term NT is stratified in composition and amount of soil organic matter (SOM). The carbon nitrogen ratio of SOM increased substantially toward the surface of soil under NT management (McCarty and Meisinger, 1997). Various long- term field studies have demonstrated marked stratification of soil organic matter with depth that occurs in soils under NT management as well as the apparent increase in the amount of organic matter in the surface profile of soil. (Blevins et al. 1984). Increased amounts of soil nitrogen and carbon in the top soil under NT was with little doubt due to surface deposition of crop residue, whereas losses of nitrogen and carbon in the 12.5 to 20 cm interval may be attributed to net loss through mineralization (McCarty et al. 1998). NT agriculture, together with leaving crop residue in fields, does have costs. The yield may be lower in poorly drained and compacted soils and in places whre springtime soil warming is slow. Initially, more fertilizer may be required, but as SOC increases, the soil becomes more productive, requiring the same or even less fertilizer. Crop residue left in the fields would not be available for animal feed, energy production, biofuels, or other uses and may increase incidence of pests and pathogens (Lal et al. 2004). Tillage is the most important controlling factor for carbon sequestration in soil; and carbon sequestration will be very slow as long as surface tillage is a part of the management system (Torbert et al. 1999). Increasing conservation tillage to 76% of planted cropland would change agricultural systems from carbon sources to carbon sinks (Kern and Johnson 1993). Of all cultivated land (1379 Mha globally), NT is currently practiced on only 5% of the worlds cropland (Derpsch and Benites 2003 in Lal et a1 2004). Concomitant conversion to cropping systems that conserve, or increase, SOC could also help move agriculture from carbon source to carbon sink (Robinson et al. 1996) ROTATION EFFECTS ON SOC Crop rotations usually increase SOC, when compared with monocultures (Havlin et a1. 1990). Generally, SOC and nitrogen concentrations have decreased for continuous cropping, while rotations maintained or increased SOC and nitrogen concentrations in the surface layer (V arvel 1994). The prevalent cropping system in theCom Belt is an alternating 2 yr rotation of corn and soybean. Although more above ground carbon was returned to the soil with corn (1.4 times more than soybean), total SOC did not differ with crop sequence or depth. Using a two pool model, Huggins et al. (1998) determined the half lives of C4 (corn) and C3 (soybean) carbon in the fast pool were less than 1 yr, while in the slow pool the half life of C3 derived carbon was 34 yr longer than C4 derived carbon. Three cropping systems (fertilizer based-N, manure based-N, and legume based- N) were evaluated over a com-soybean rotation by Drinkwater et al. (1998). Corn, the only C4 crop present, accounted for 74, 48 and 22% of the returned residues in the conventional, legume and manure systems respectively. Maize derived carbon replaced the original SOC deposited by the C3 temperate forests that preceded agriculture in this region. Net carbon levels did not change because the loss of C3 derived carbon was nearly equivalent to the gain of C4 derived carbon. Net gains in soil carbon seen in the legume and manure systems were due to significant increases in C3 derived carbon. Plant species composition and litter quality influenced SOC turnover markedly (Drinkwater et al. 1998). Greater retention for both carbon and nitrogen suggest that use of low carbon-to-nitrogen residues to maintain soil fertility combined with increased temporal diversity restores the biological linkage between carbon and nitrogen cycling in these systems and could lead to improved global carbon and nitrogen balances. Application of these practices in the major maize/soybean growing region in the USA would increase SOC sequestration by 0.13-0.30 x 10'4 g yr'l. This is equal to 1-2% of the estimated annual carbon released into the atmosphere from fossil fuel combustion in the USA (Marland and Boden 1997 in Lal et a1 2004) and is a significant contribution. MANURE EFFECTS ON SOC Beef cattle feedlot manure contains essential nutrients in addition to approximately 15% carbon that can be used to improve soil physical and chemical properties (Eghball 2002). Carbon in manure is likely to have far greater value than the nutrients it contains if applied to a low organic matter or eroded soil. A long-term study in Germany found that more than 100 yr of manure applications increased soil organic matter fractions associated with the fine and medium silt fractions while clay associated fragments were higher in the unfertilized treatment (Schulten and Leinwever 1991). Cattle feedlot manure application increased SOC, total nitrogen (TN), potentially mineralizable nitrogen, soluble phosphorous, and soil microbial biomass, compared with soils receiving no manure (Fraser et al. 1988). Rate of SOC change was directly related to carbon input fiom crop residues and amendments (Rasmussen and Parton 1994). Additional input of organic substances containing high amounts of carbon, such as farmyard manure or the incorporation of crop residues will increase organic carbon content in soil (Dersch and Bohm 2001). Despite increased oxidative losses it was estimated that approximately half of the added manure-carbon was retained in the soil at the end of the season (Rochette and Gregorich 1998). Iazurralde et al. (2001) determined that addition of farmyard manure was a key management component leading to SOC increases. Increasing the amount of plant residue carbon returned as manure reduces the level of carbon productivity needed for a fixed carbon input to soil. SOC, phosphorous, and potassium increased with increasing rate of composted beef cattle feedlot manure applied form 1987 to 1990, while increasing rates of synthetic N fertilizer application decreased soil phosphorous and potassium, but had no effect on SOC (Schlegel 1992). Drinkwater et al. (1998) compared manure and conventional systems and found that even though both systems received equal amounts of carbon, the manure system showed a significant increase in carbon stored in soil. Compared with senescent-crop residues, a larger proportion of manure- derived carbon is retained in soil, probably because manure is already partly decomposed and contains a larger proportion of chemically recalcitrant organic compounds (Paustian et al. 1992; Hassink 1992). Manure has the ability to increase SOC even with high- intensity conventional tillage (Anderson et al. 1990). Composting manure is a useful method of producing a stabilized product that can be stored or spread with little odor or fly-breeding potential. The other advantages of composting include killing pathogens and weed seeds, and improving handling characteristics of manure by reducing manure volume and weight (Eghball 2002). Approximately 25 and 36% more carbon remained in the soil after 4 yr of application of manure and compost respectively than the fertilizer treatment. A greater fraction of applied carbon remained in the soil from compost application even though cumulative carbon application rate was less for compost 7.78 Mg/ha then for manure 10.42 Mg/ha when averaged across treatments indicating more stable carbon compounds in compost than in manure. Composting has some disadvantages that include nutrient and C loss during composting, the cost of land, equipment, and labor required for composting, and odor associated with composting (Eghball 2002) Total carbon concentration in the surface soil was generally greater for nitrogen (N) than phosphorous (P) based manure and compost applications, and the differences became greater with years of application, indicating the cumulative effects of manure and compost application (Eghball 2002). Biennial N-based compost treatment resulted in greater soil surface (0-15) carbon and nitrogen concentrations than annual N-based compost in the fourth year, even though similar total amounts of compost were applied for both treatments in 4 yr. This indicates that heavy application of compost every other year may protect the carbon and nitrogen from mineralization, as compared with smaller annual rates (Eghball 2002). All N-based treatments significantly increased SOC in the 0-15 cm soil profile compared to the check while, the only P-based system that increased SOC was the biennial P-based manure system. These results indicate that manure and compost can increase carbon sequestration in the soil, which may have implications for global climate change (Eghball 2002). Application of compost or manure appear to be effective methods to increase SOC however, Schlesinger (1999) argued that manuring is not a valid method for soil carbon sequestration because of the extra land required to produce the manure. COVER CROPS Winter cover crops have shown some potential to reduce soil bulk density, increase water infiltration properties, and change the distribution of soil aggregate-size classes relatively quickly after their introduction into cropping systems (McVay et al.1989; Kuo et al 1997). There were trends for both TOC and TKN levels to be lower in soil from the cereal treatment plots, which indicates that the use of triticale as a cover crop may promote mineralization of SOM (Mendes et al. 1999). Multiple factors influence sequestration of carbon in soils; tillage practices, types of crops produced, productivity of the soil, proper use of soil amendments such as manure and compost, cropping frequency, and latitude. The objectives of this research were to 1) determine the effect of cover crops, manure, and compost on carbon sequestration rates in a silage corn — soybean rotation; 2) evaluate the effect of latitude on carbon sequestration; and 3) develop best management practices to increase carbon sequestration in Michigan soils. MATERIAL AND METHODS Field experiments were conducted near East Lansing (N 42.43, W 84.28) and Chatham (N 46.29, W 86.76), MI over a three year period beginning in the fall of 2001. Soil at East Lansing was a mixture of Aubbeenaubbee-Capac sandy loams (Fine-loamy, mixed, mesic Aerie Ochraqualfs) and Colwood-Brookston loams (F ine-loamy, mixed mesic Typic Argiaquolls and Typic Haplaquolls). Chatham soil was a Trenary fine sandy loam (Coarse-loamy, mixed frigid Alfie Fragiorthods). Experimental design was a randomized complete block with four replications at each location. Treatments were arranged as a 2x3 factorial at East Lansing. Factors consisted of rye vs. no rye, and compost amendment vs manure amendment vs no amendment. Prior to experiment establishment at East Lansing the site was under a corn- soybean rotation with conventional tillage. Corn was planted in 2001, harvested as silage and no-till production practices were implemented when the winter rye cover crop was planted. The site was split into two rotations, com-soybean—corn (CSC) and soybean- com-soybean (SCS). Treatments at East Lansing were; winter rye cover crop (R) alone or in combination with either composted manure (R+C), or fresh manure (R+M), composted manure (C) alone, fresh manure (M) alone, and an untreated check (U) applied to both rotations. The Chatham site was an alfalfa field prior to experiment establishment. The experiment at Chatham consisted of two rotations, continuous silage corn (CC) and a forage soybean-silage corn rotation (SC). A winter rye cover crop was planted after removal of forage soybean in 2002. Treatments consisted of composted manure (C), liquid dairy manure (M), and an untreated check (U) applied to both rotations. Plot size varied between locations with plots at East Lansing 6.1 x 12.2 m with 76 cm wide rows of corn or 38 cm wide rows of soybean and plots at Chatham were 18.3 x 18.3 m wide with 76 cm wide rows of corn or soybean in 19 cm wide rows. Planting dates, and harvest dates can be found in Table 1. Winter rye was terminated approximately two weeks prior to planting with glyphosate (840 g ae/ha) at East Lansing and glufosinate (140 g ai/ha) at Chatham. 10 Biomass samples were collected by harvesting four 0.25m2 quadrats in 2002 per plot and six quadrats in 2003-04 prior to planting. Samples were dried and ground to pass through a 1 m screen and analyzed for total carbon and total nitrogen (TN) content using a Carlo- Erba CN analyzer (Carlo Erba Strumentazione, Milano, Italy). Winter rye kill and harvest dates are located in Table 1. Solid dairy/beef manure and composted manure were applied in the spring and fall of each year through the spring of 2004 at East Lansing. Liquid dairy slurry and solid composted manure were applied in the spring of each year at Chatham. Tables 2 and 3 include the date of application, rates of manure or compost application, and nutrient analyses of manure and compost. Soil Sampling Soil samples were collected using a regular hand soil probe in 2002 and a GeoProbe (Salina, KS 67401) slide hammer type probe in 2003 and 2004. Six soil cores 1.8 cm in diameter were collected from each plot and divided into 0-5 and 5-25 cm deep samples in the spring of 2002. Three soil cores 3.9 cm in diameter were taken per plot in the spring of 2003 and spring and fall of 2004. Samples within a plot were composited to make one bulk sample each for the 0-5 and 5-25 cm depths per plot per sampling. Soil moisture, bulk density, nitrate-nitrogen, phosphorous, SOC, TN, and particulate organic matter carbon (POM-C) content were determined from these samples. Sampling dates can be found in Table 1. Soil samples were weighed before being sieved through a 4 mm screen to remove large rocks and pieces of organic material. A sub-sample of the sieved soil was dried at 65° C to determine soil moisture. Bulk density was calculated by subtracting the weight 11 of the rocks from each sample and multiplying by the percent dry soil then dividing by the total volume of soil collected minus the volume of the rocks. Michigan State University Soil and Plant Tissue testing laboratory protocols were used to determine nitrate-nitrogen and phosphorous concentrations (Frank et al. 1998 and Gelderrnan and Beegle, 1998). A l N KCl solution was used to extract the nitrate- nitrogen from wet soil. Bray P-l methodology was used on air dried samples to determine phosphorous concentrations. A ball mill was used to finely grind a subsample of soil before analysis with a Carlo-Erba CN analyzer for SOC and TN concentration. Carbon in the soil was considered 100% organic since the soil pH was below 7.0 at both locations. SOC and TN data is presented on a mass per unit area basis by multiplying the fraction of SOC by respective measurements of soil bulk density and depth of soil sampled. Particulate organic matter carbon (POM-C) concentration was determined using a modified version of a procedure described by Camberdella et a1 (1992). 10 g of soil was shaken for 15 hours in a 5 g/L solution of sodium hexametaphosphate. Afier shaking, the mixture was washed through a 53 um screen with distilled water to separate the soil into two parts, mineral and particulate matter. The mineral portion was collected, dried, and ground using a mortar and pestle and then analyzed for carbon content using a Carlo Erba CN analyzer. POM-C was calculated by subtracting the mineral associated carbon from the total carbon. Deep core samples to a depth of 0.9 m were collected to monitor nitrate and phosphorous leaching and loading. A Giddings hydraulic probe (Ft. Collins, CO 80522) was used to extract the cores. Two cores were collected per plot and divided into four 12 depths (0-15, 15-30, 30-60, and 60-90 cm). These samples were subjected to the same protocols as described earlier for nitrate-nitrogen and phosphorous concentration determination. Tissue sampling Rye and soybean aboveground residues were harvested and analyzed to determine how much total carbon and nitrogen was being returned to the soil. Root residue contributions were estimated for corn and soybean using published values from the literature (Buyanovsky and Wagner 1986; Bolinder et al. 1999). RESULTS AND DISCUSSION East Lansing Soil bulk density Soil bulk density is an important factor in determining carbon sequestration in soil. Soil organic carbon (SOC) and total nitrogen (TN) levels are easily manipulated with bulk density (McCarty et al. 1998). An increase in SOC or TN percentage doesn’t necessarily mean that SOC or TN increased, if the bulk density decreased the total amount of carbon or nitrogen might have remained the same. Bulk densities were similar among treatments in both the CSC and SCS rotation areas in the spring of 2002 (Table 4). Main effect of rye resulted in lower bulk density of the 0-5cm profile in the CSC rotation in the spring of 2003 than those treatments without rye (Table 5). Treatments containing either compost or manure soil amendments had lower bulk densities than those without in the spring of 2003 and the fall of 2004 in the 0- 5 cm profile of the CSC rotation. Rye decreased the bulk density of the 0-5 cm profile of the SCS rotation by 25% while non-rye treatments decreased bulk density by 18%. 13 Cover crop and soil amendments did not affect soil bulk density in the 5-25 cm profile in either rotation; however the interaction of the two main effects did influence the bulk density in the fall of 2004 in the CSC rotation (Tables 4 and 6). The untreated resulted in a lower bulk density than R and M but was not significantly lower than the other treatments. Carbon Crop residues can be a significant tool to increase SOC; this study investigated silage corn and soybean which generally return little carbon back to the soil since the majority (95%) of the corn stover is removed during harvest and soybean residue is relatively low in quantity and decomposes quickly. Several studies have noted that carbon inputs from roots are probably underestimated due to the difficulty of measuring rhizodeposition of carbon and turnover of root biomass before maturity (Barber 1979; Buyanovsky et al. 1987). There were few differences observed in the amount of carbon from crop residues returned to the soil (Table 7). Treatments including either compost or rye returned more crop residue to the soil than other treatments (Table 8). Total crop residue returned over three growing seasons was similar among all treatments. The SC S rotation returned 26.7 Mg/ha compared to 22.0 Mg/ha from the CSC rotation when averaged across treatments. Total carbon inputs were significantly affected by both the soil amendment and rye cover crop factors. Total carbon input over three growing seasons was greatest with manure followed by compost and rye treatments. Manure application at East Lansing resulted in 21.6 Mg/ha of carbon being added to the soil surface in both rotations over the three years (Table 2). The majority of that carbon was added in 2002 (59%) when beef 14 feedlot manure with woodchip bedding was used (43% C). Compost treatments added 16.29 Mg/ha of carbon at East Lansing (Table 2). Rye did not affect total carbon levels in the 0-5 or 5-25 cm profiles in either rotation (Table 9). Mendes et al. (1999) realized a trend for SOC levels to be consistently lower in soil removed from a cereal crop, indicating the use of triticale as a cover crop may promote mineralization of organic matter. Rye is a cereal crop so it is possible that it may also promote organic matter mineralization. Application of soil amendments did influence total carbon levels in the 0-5 and 0- 25 cm profiles of the CSC rotation (Table 9). Compost increased total SOC more than manure which increased SOC more than no amendment in the 0-5 cm profile of the CSC rotation (Table 10). Total profile SOC increased by 43% with compost compared to 26% with manure and a 3% loss with no amendment. Soil amendments had a significant impact on SOC in the 0-5 and 0-25 cm profiles of the SCS rotation in the spring and fall of 2004 (Table 9). Compost increased SOC more than manure or no amendment in the 0-5 cm profile in the spring of 2004 (Table 10). This disagrees with work done by Rochette and Gregorich (1998) who found that stockpiled manure increased SOC more than rotted (partially composted) manure when incorporated to a depth of 20 cm. However, Eghball (2002) reported a greater fraction of carbon remained in the soil after compost application than manure. Compost and manure both increased SOC more than no amendment in the 0-25 cm profile in the spring and fall of 2004. The interaction of the two factors was significant for some sampling dates in the ‘ 0-5 cm profile in the SCS rotation (Table 9). R+C had significantly more SOC in the 15 spring of 2003 than all other treatments (Table 11). R and U both resulted in less SOC in the fall of 2004 than all other treatments. Since these treatments had the smallest amounts of carbon returned back to the surface it makes sense that they would have the smallest increase in SOC. The lack of significance among treatments in the 5-25 cm profile is not surprising. No differences in SOC in the 5-15 cm profile were evident after 4 and 8 yr of NT (Wood et a1. 1991; Ortega et al. 2002). Wright and Hons (2004) did observe differences in the 5- 15 cm profile for some treatments after 20 yr. Rate of soil carbon sequestration will reach a peak in 5 to 10 yr, then decline to near zero in 15 to 20 yr afier a change to NT practices (West and Post 2002). Little to no increase in SOC in the first 2 to 5 yr after changing management practices will be observed but will be followed by a large increase in the next 5 to 10 yr (Franzluebbers and Arshad 1996; Lal et al. 1998) Global analysis of soil organic carbon sequestration rates by West and Post (2002) found that little or no change occurred between 20 and 30 cm. Particulate organic matter POM is the most reactive fraction of organic matter to production practices (Koutika et al. 2001). This fraction of organic matter is the easiest to detect changes in carbon content in over a short period of time which was essential for this research since it was conducted over a three year period. Substantial changes to other organic matter fiactions would be hard to measure in such a short time period. Data is reported in kg/ha of POM-C. Cover crop did not affect POM-C in either rotation (Table 12). Soil amendment had a significant effect on POM-C in the 0-5 and 0- 25 cm profiles of the CSC rotation in the fall of 2004, on the change in POM-C for the 0- 16 5 cm profile and on the 0-25 cm profile of the SCS rotation. The same trend was present for both rotations with POM-C being influenced most by compost then manure then no amendment (Table 13). There was a significant interaction between the main effects in the fall of 2004 in the SCS rotation (Table 12). R+C had the highest amount of POM-C followed by C, R and U had the lowest levels of POM-C (Table 14). Total nitrogen Total nitrogen (TN) in the 0-5, 5-25, and 0-25 cm profiles in the CSC rotation was affected by soil amendments (Table 15). Compost generally resulted in higher TN than manure or no arnendement in the 0-5 and 0-25 cm profiles (Table 16). Soil amendments affected TN in the 0-5 cm profile of the SCS rotation in the spring of 2004 and in the 0- 25 cm profile in the spring and fall of 2004. Compost increased TN more than the other treatments in most instances. There was a significant interaction between the cover crop and soil amendment factors in 2003, fall of 2004, and in the change in TN in the 0-5 cm profile in the SCS rotation (Table 15). R+C had more TN than all treatments in 2003, while R and U had less TN than all other treatments (Table 17). All treatments except U were similar to R+C in the fall of 2004 and in percent change of TN. Nitrate and phosphorous Application of manure and compost not only is a viable method of increasing SOC but also provides nutrients such as nitrogen, phosphorous, and potassium (Eghball 2002). Nitrogen and phosphorous are nutrients essential for plant growth and development but can also be considered pollutants. Nitrates can leach through the soil profile and into the groundwater where they can accumulate to potentially dangerous 17 levels (El-Hout and Blackmer 1990). Phosphorous is more of a surface water concern where it can cause eutrophication (Carpenter et al. 1,998). Phosphorous generally doesn’t leach through the soil profile unless the soil becomes saturated with phosphorous. With the high application rates of manure and compost in these studies it was important to ' monitor nitrate and phosphorous levels throughout the soil profile. Nitrate-N levels were monitored in the 0-5, 5-25, and 0-25 cm profiles similar to SOC and TN. Cover crop and soil amendment factors were significant in both rotations (Table 18). Rye significantly reduced the amount of nitrate in all of the soil profiles in 2002 in both the CSC and "SCS rotations (Table 19). Rye also decreased nitrate-N levels in 2003 in the SCS rotation. An interesting observation was that nitrate-N levels increased by 27 and 34% over the three growing seasons in the rye treatments and decreased by 22 and 33% in the non-rye treatments in the CSC and SCS rotations respectively. Soil amendments affected nitrate-N levels in the 0-5 and 0-25 cm profiles of the SCS rotation (Table 18). Manure resulted in the highest nitrate-N levels in the spring of 2004 in both the 0-5 and 0-25 cm profiles (Table 19). In 2003 compost had higher nitrate-N than the other treatments. A significant interaction‘between the cover crop and soil amendment occurred in 2003 for all profiles in the CSC rotation (Table 18). Compost alone had the highest level of nitrate-N in all three profiles followed by U (Table 20). The compost applied April 8, 2003 had a C:N ratio of 13.9 which was the lowest of any compost applied. This may have led to more nitrate-N being transported into the soil solution and away from the 18 compost. Rye cover crop also had approximately 50% of the nitrate-N has the treatments that did not include rye. Soil samples were taken before the manure and compost was applied in the spring of 2002; also the rye cover crop was planted in October of 2001 so there was a lot of fresh vegetative growth before soil sampling was completed. This would explain the lower nitrate-N levels under rye treatments in 2002. Soybean were grown in 2003 in the CSC rotation and being a legume they have the ability to ‘fix’ nitrogen in the root nodules which may be lost to the soil through exudation or decomposition. However if nitrogen is available soybean will utilize that nitrogen first before ‘fixing’ nitrogen. This may explain why there was a significant interaction in the spring of 2004 in the CSC rotation. Why the manure treatments were so high in the spring of 2004 under the SCS rotation is not known. The observation that rye treatments increased nitrate-N over the three growing seasons is more difficult to explain. This could be explained by the fact that the spring 2002 samples were collected after allowing the rye cover crop to grow for approximately 6 months after harvesting silage com; the fall 2004 samples were collected shortly after soybean harvest. Therefore, in 2002 rye had the chance to use any available nitrate in the soil while in the fall of 2004 there would not have been a sink for the nitrate left in the soil or that being released by the decomposition of soybean residues. These results are similar to those of Sanchez et al. (2004) who found that wheat reduced nitrate leaching after soybean by drying the soil and immobilizing the nitrogen from the soybean residue. Soil amendments significantly affected soil phosphorous levels in the 0-5 and 0- 25 cm profiles of the CSC rotation and the 0-25 cm profile of the SCS rotation every year 19 except for 2002 (Table 21). Compost resulted in higher phosphorous levels than the other treatments every year (Table 22). Rye had minimal effect on the accumulation of phosphorous in either the 0-5 or 5-25 cm profiles (Table 22). There was a significant interaction between the cover crop and soil amendment factors in 2003, fall of 2004, and in the percent change of phosphorous in the 0-5 cm profile of the SCS rotation (Table 21). R+C and C had the highest levels of phosphorous in 2003 and fall of 2004 (Table 23). Phosphorous levels in the 0-5 cm profile increased by 35% with R+C between the spring of 2002 and fall of 2004. Chatham Soil bulk density Bulk densities at Chatham were not different among treatments in the 0-5 or 5-25 cm profiles at any sampling (Table 24). All treatments resulted in increased bulk densities in the 0-5 cm profile and there were no differences in the percent change between 2002 and fall 2004. Bulk density of the 5-25 cm profile appears to be affected by rotation, COM and CC-C decreased bulk density while SC-M and SC-C increased bulk density. Carbon Total crop residue carbon returned ranged from 1.46 to 3.39 Mg/ha. SC-C returned more crop residue carbon than all other treatments except SC-M (Table 25). Significantly more carbon was returned in the SC than the CC rotation. Rye cover crop added approximately 0.13 Mg/ha of carbon in 2003 to the system (Table 25). However, it is difficult to determine the impact the winter rye cover crop had on SOC since it was 20 used in conjunction with forage soybeans. Liquid dairy slurry manure added 8.73 Mg C/ha and compost added 6.04 Mg C/ha to the soil surface (Table 25). SOC levels at Chatham were not different at any sampling date or any portion of the profile (Table 26). CC-U was the only treatment that did not result in increased SOC in the 0-5 cm profile. Rates of change of SOC were also similar among treatments for both depths and the total soil profile. Though there were no differences there were some interesting results. SOC in the 0-5 cm profile of the CC increased by 6.06 Mg C/ha more than SC between 2002 and 2004 even though SC-M addedl.39 Mg C/ha more to the system than CC-M. CC-C and SC-C resulted in 64% and 79% increases in SOC. A surprising result occurred between CC-U and SC-U, CC-U loss 0.71 Mg C/ha while SC-U gained 9.27 Mg/ha. Total carbon additions for these treatments were 1.55 Mg C/ha for CC-U and 3.17 Mg C/ha for SC-U so the large difference is not accounted for there (Table 25). Crop rotation does increase carbon sequestration rates compared to monocultures however, it is hard to believe that it could have this big of an impact. An interesting observation in the 5-25 and 0-25 profile was that SC-M and SC-C increased soil carbon more than COM and CC-U. This supports previous research that crop rotations are better than monocultures at sequestering carbon. Total nitrogen No differences in TN were evident at any time in any profile (Table 26). CC-U loss 3% of the original total N during the course of the experiment. This result is not very surprising considering that the only N added to this system was in the form of 28% UAN during sidedressing. 21 Particulate organic matter POM-C was initially 20 to 27% of the total SOC in the 0-5 cm profile at Chatham (Table 27). In the fall of 2004 that had increased to 29 to 46% of the SOC was associated with the POM fraction. However, there were no differences among treatments. In the 5- 25 cm profile POM-C ranged from 4 to 14% and 28 to 32% in 2002 and the fall of 2004, respectively. Similar to the 0-5 cm profile there were no differences among treatments. Nitrate and phosphorous A Nitrate-N levels in both the 0-5 and 5-25 cm profiles at Chatham were generally stable throughout the experiment (Table 28). Differences among treatments were observed in the fall of 2004 for the 0-5 cm profile and in the spring and fall of 2004 for the 5-25 cm profile. Addition of compost resulted in higher nitrate-N levels than all other treatments in the fall of 2004. All treatments resulted in increased nitrate-N levels over the three growing seasons for both the 0-5 and 5-25 cm profiles. Phosphorous levels in the 0-5 cm profile were similar among treatments until the fall of 2004 when SC-C and CC-C had higher phosphorous levels than all other treatments (Table 28). CC-C and SC-C increased phosphorous levels by 859% and 693%, respectively. SC—M had more initial phosphorous than CC-C in 2002 but in the fall of 2004 they had similar levels. SC-C had the highest level of phosphorous in the fall of 2004 and was similar to CC-C and SC-M. Total phosphorous levels and percent change of phosphorous were highest with SC-C and CC-C. All other treatments were similar to each other. Latitude effects 22 SOC levels are often related to climatic patterns, generally increasing from south to north due to cooler temperatures and lower decomposition rates, and from west to east due to precipitation (Kern and Johnson 1993; and Paustian et al. 1997). Chatham (N 46.29, W 86.76) is significantly farther north than East Lansing (N 42.43, W 84.28), so the expectation would be that carbon would be sequestered at a faster rate in Chatham than East Lansing. Average monthly temperatures and total monthly precipitation for East Lansing and Chatham can be found in Tables 29 and 30. Temperatures at Chatham were generally 3 °C cooler than at East Lansing. Total precipitation was more variable throughout the three years, however looking at the 30 yr averages Chatham usually receives more precipitation during the year as a result of lake effect storms. NT continuous corn at Chatham with no amendments realized a 23% increase in SOC while the CSC and SCS with no amendments at East Lansing resulted in carbon losses of 4 and 2% respectively. Less crop residue was applied at Chatham so the efficiency of converting crop residues into SOC is higher at Chatham than East Lansing. Summary Rye, compost, and manure all lowered bulk density at some point during the experiment at East Lansing. Bulk densities for the 0-5 cm profile increased at Chatham for all treatments. Rye doesn’t appear to provide enough residual carbon to increase carbon sequestration over NT alone at East Lansing. The addition of either compost or manure dramatically increased the amount of SOC measured. Compost treatments resulted in higher carbon levels than manure treatments at East Lansing. No differences were observed among treatments at Chatham for SOC levels in any profile. 23 POM-C was influenced by soil amendments at East Lansing, with POM-C increasing most with compost then manure then no amendment. No differences were observed in POM-C at Chatham. Compost generally resulted in higher TN at East Lansing than manure or no amendment. There were no differences among treatments at Chatham. Cover crop rye decreased nitrate-N levels in 2002 and 2003 at East Lansing. In the fall of 2004 nitrate-N was actually higher under rye than under no rye. Compost and manure increased nitrate- N at both Chatham and East Lansing. Compost resulted in higher phosphorous levels at both Chatham and East Lansing. . Latitude does appear to have a significant affect on carbon sequestration. Treatments at Chatham were more efficient at sequestering carbon then treatments at East Lansing. Soil at Chatham was a fine sandy loam while soil at East Lansing was a mix of sandy loam and learn. Though the soil is classified as a sandy loam at Chatham it seems to have a much higher sand content than the soil at East Lansing. Heavy soils showed the highest level of organic matter (loamy clay), followed by medium textured soils (sandy learn), and light soils (loamy sand) contained the lowest organic carbon stock (Dersch and Bohm 2001). Fine textured soils retained more crop residue carbon, and the turnover of this carbon in these soils appeared to be slower than in soils with coarse textures (Liang et al.1998). Conclusions Rye cover crop does not add enough carbon to the system to be used by itself. Compost and manure can increase SOC significantly depending on type of amendment and location. However the use of these amendments needs to be monitored carefully to 24 avoid leaching and loading of nitrates and phosphorous. Rye cover crop used in conjunction with either compost or manure will help control the leaching and loading of these nutrients. Sequestration rates were affected by latitude as expected. There is little added benefit to using a cover crop or applying compost or manure at Chatham. NT alone accounted for 23% of the carbon sequestered over the three growing seasons. 25 Tables Table 1. Dates of soil sampling, planting, herbicide application, and harvest at East Lansing and Chatham. East Lansing Chatham 2002 2003 2004 2002 2003 2004 Soil sampling Spring 0-25 19/4* 21/5 9/4 14/5 5/5 23/4 Fall 0-25 - - 9/1 1 - - '8/11 Spring deep - 22/5 19/6 - - - Fall deep 6/1 1 10/11 - - - - PSNT 28/6 27/6 1/7 - - - Planting Corn 23/5 5/22 5/13 6/12 5/20 5/17 Soybean 23/5 5/22 5/13 6/6 - 5/29 Cover crop 1/10/01 8/10/02 4/10/03 — 10/9/02 - Herbicide application Bumdown 5/5 8/5 3/5 - 30/4 - Harvest Silage 12/9 17/9 14/9 3/10 7/ 10 11/10 Soybean 28/9 1 1/10 8/10 5/9 - 14/9 Cover crop 8/5 9/5 5/5 - 5/5 - * Dates expressed as day, month, year 26 msccofimosm £25 ”mcoumm>2nn< can» £308 5% we 33298 $st _.. w.o_ N03 QC 9%. mtmm 3.3 86m moan ma .mm ode vm. _ m vow m 36m 053 3.3 3‘. fl m vowm Stem soda 33h 056 @340 omdo vmdm 26m $43 ea. K mean we. K 3.? $6 :5 and $6 $55 and ommd Rmd mmmd coed :6 Ed mmd and mnmd memo Rod mwod Sad 336 $6 mud on; cod hmfio wood vomd vwmd acmd 236 m2: 5.: od— Ro._£< m2 m2 m2 m2 m2 m- .3 m2 8; $4 a- a: a? a3 a3 m2 m2 m2 m2 m2 m- of 8. $4 of a- as on. was a: _ 8; a? 43 N3 m2 m2 m2 m2 m2 o- ”E ”2 Sn ”3 a- 52 m3 m3 m3 m2 m2 m2 m2 m2 a- Rs a2 43 as; m- as G; of 8; a- ”2 N3 was was as seem dale. aaoom 3cm mloom mica. so m3 4 m2 m2 m2 m2 3. NS 42 a... e: a- 9: m2 2: NE m2 m2 m2 m2 m2 2. a: «S a: m: mm- m2 2: a: 4: am- an a: a: m2 m2 m2 m2 9.86 m2 2- an; a: a? S; 3- a2 5 am; m3 m 23 m2 86 m2 a- can an. a? was 2- m2 9: a: a: 8. 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M. .x. neon .x. .5.» 8.9 9.0 .38 .58 mloom % wso alga 38 1'88 alga law .8 3m .5 m-.. .5. mafia:— .mmm a $an .5 m~-m 23 We on. .5 825% £5 .8 2.8.: 5583.: .0 03m... 30 Table 7. ANOVA for crop residue carbon inputs and total carbon (C) inputs for both CSC and SCS. CSC C inputs Factor 2002 2003 2004 Total Crop residue Cover crop NS NS * NS Amendment NS NS * NS Interaction NS NS NS NS Total C input Cover crop *** NS *** *** Amendment *** *4“! *** *IIIIII Interaction NS NS NS NS SCS Crop residue Cover crop NS NS NS NS Amendment NS ** NS NS Interaction NS NS NS NS Total C input Cover crop *** *** NS *** Amendment *Iklll *** *** *** Interaction NS NS NS NS * = P<0.05 * * = P<0.01 * * * = P<0.001 31 Table 8. Carbon input from crop residue and total input Crop residue input Total carbon input In. 2.002. 2M3. 20.0.4. .1le .2002. .2001 2.003. Total CSC kg C/ha Comp 1050 1940 810 3790 1 1200 9090 3370 23660 Man 1000 ' 1670 720 3400 14210 8030 3500 25470 None 1070 2020 740 3820 1450 2140 860 4450 LSD NS NS 50 NS 180 260 60 380 None 1010 2010 730 3740 8490 63 70 2400 17270 Rye 1070 1750 790 3600 9410 6470 2760 18640 LSD NS NS 40 NS 150 NS 50 310 SCS Comp 1840 980 1710 4530 11910 8110 4330 24580 Man 1710 990 1880 4320 14800 7050 4680 26560 None 1620 960 1940 4510 1960 1150 2130 5210 LSD NS 130 NS NS 310 140 380 840 None 1680 860 1840 43 90 9170 5230 3520 17960 Rye 1760 ' 890 1850 4520 9950 5640 3910 19610 LSD NS NS NS NS 290 120 NS 720 32 Table 9. ANOVA for SOC in the 0-5, 5-25, and 0-25 cm profiles of the CSC and SCS rotations CSC Profile (cm) Factor 2002 2003 Spring 2004 Fall 2004 Chg 0-5 Cover crop NS NS NS NS NS Amendment NS *** *IIUII *IIIIII *** Interaction NS NS NS NS NS 5-25 Cover crop NS NS NS NS NS Amendment NS NS NS NS NS Interaction NS NS NS NS NS 0-25 Cover crop NS NS NS NS NS Amendment NS * NS *** *** Interaction NS NS NS NS NS SCS 0-5 Cover crop NS * * NS NS NS Amendment NS *IIIIII *** *** *** Interaction NS * NS *** ** 5-25 Cover crop NS NS NS NS NS Amendment NS NS NS NS NS Interaction NS NS NS NS NS 0-25 Cover crop NS NS NS NS NS Amendment NS NS ** *** NS Interaction NS NS NS NS NS * = P<0.05 * * = P<0.01 * ** = P<0.001 33 53.3.88 8... w. 5.68.8.5 .. m2 m2 m7. m7. m2 m2 m7. m7. m2 m7. 8 88m 88m 88... 88.. o 888 8.8 8.8 89.8 .8 8...... 8o: 28... 888 w 8.8. 888 8.8 88 m2 88 88 m2 m2 m2 m2 m2 m2 m2 . 888 .88 88M 88.. o 888 .88 8.8 288 8 88m 88m 88m 88.. o 888 8:8 288 888 8.. 88.. .88 .8... 88m 2 888 888 888 888 m2 m2 m2 m7. m2 m2 m2 m2 m2 m2 a. 088 88m 88m 88.. .. .88 888 8.8 888 8 88m .88 8.8 88.. o. 888 888 888 888 a 88 m2 88 m2 m2 m7. m2 m2 m7. m- 88.8 8o... 8...: 88m 8 82.8 .88 888 8.8 8 8...... 88m 88... 88... o. 888 .88 888 888 a. 88... 888 8...... 8.8 ... .58 888 888 888 8 98... 8 9...... .5 8....8 8.8 '88 ll88 «a .Ivo8 8.8 1'58 SIN :5 8-.. so 88 m2 m2 m7. .8... m2 8 88. 88 8o. . 8 8 m8 coon. coon omww comb .8 .8. . 2m. .58. m2 m 88 28 88 8: 98 womom. co.” cema o.~8 .... 88. 8... 88.. 28 m2 m2 m2 m7. m2 .8 88. 88. 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E+M U+M 8N8. Om..— D 2+”— 0 E O+m .m We ad... .voom we :8 on. o. moom mo macaw on. 88.. 9.855 88.8w .8 88:88 58-53.38 8.8 583.38 -88 8 88.8... so 8-.. 88 8-8 .8-.. 2.. ... .8582. 008 a. 8:82: 8882... ... n8.88 35 Table 12. ANOVA for POM-C for both CSC and SCS rotations. CSC Profile (cm) MI. 2002 EalLZQQA Chg 0-5 Cover crop NS NS NS Amendment NS *** NS Interaction NS NS NS 5-25 Cover crop NS NS NS Amendment NS NS NS Interaction NS NS NS 0-25 Cover crop NS NS NS Amendment NS *** NS Interaction NS NS NS SCS O-S Cover crop NS NS NS ‘ Amendment NS *** *** Interaction NS *** NS 5-25 Cover crop NS NS NS Amendment NS NS NS Interaction NS NS NS 0-25 Cover crop NS NS NS Amendment NS *** NS Interaction NS NS NS * = P<0.05 ** = P<0.01 *** = P<0.001 36 Table 13. Main effect means for POM-C in the 0-5, 5-25, and 0-25 cm profiles at East Lansing Rot. In. CSC Comp Man None LSD None Rye LSD SCS Comp Man None LSD None Rye LSD 0-5 5-25 0-25 2002 2004 Chg 2002 2004 Chg 2002 2004 Chg_ ----kg/ha---- --%-- ----kg/ha---- --%-- ----kg/ha---- --%-- 580 8930 1160 3460 4270 57 3820 1320 154 0 940 4770 594 3240 4200 177 4180 8970 200 950 1230 90 4420 2160 63 5360 3380 14 NS 1050 NS NS NS NS NS 1380 NS 670 4990 630 3050 3650 150 3440 8630 148 970 4960 600 4360 3440 47 5470 8400 97 NS NS NS NS NS NS NS NS NS 750 9620 1334 2130 5200 234 2880 1480 592 0 780 4690 667 1230 3410 416 1900 8100 455 740 1490 147 1630 3190 225 2360 4690 134 NS 940* 350 NS NS NS NS 2310 NS 710 4710 720 1510 3840 339 2150 8550 418 800 5820 712 1810 4030 244 2610 9840 369 NS NS NS NS NS NS NS NS NS * Interaction is significant 37 Table 14. Interaction means for POM-C In. 0-5 R R+C M C R+M U LSD 5 -25 R R+C M C R+M U LSD Total R R+C M C R+M U LSD C86: 2002 Fall 2004 C_hg --------- kgflukmnmw- -«96~ 1060 1290 21 800 8220 1080 830 4170 494 350 9630 1240 1050 5380 695 830 1160 158 NS NS NS 5700 1940 7 3480 4760 101 2570 4780 321 3430 3790 13 3910 3620 34 3130 2370 119 NS NS NS 6770 3230 -13 4690 12980 134 3400 8940 230 2950 13420 173 4960 9000 170 3960 3530 41 NS NS NS SC}; 2002 Fall 2004 Chg ........ kg/ha------- --%-- 820 1420 88 860 11990 1545 840 5330 832 630 7250 223 710 4050 503 660 1560 205 NS 1890 NS 1140 3460 282 2430 5080 240 590 3270 622 1830 5330 228 1870 3560 210 2120 2930 167 NS NS NS 1950 1880 164 3300 17030 715 1220 8600 682 2460 12580 469 2580 7610 229 2780 4490 105 NS NS NS 38 Table 15. ANOVA for TN in the 0-5, 5-25, and 0-25 cm profiles of the CSC and SCS rotations CSC W) .Eacmr. 2002 2003 Spring 2004 Fall 2004 Chg 0-5 Cover crop NS NS NS NS NS Amendment NS ##III ** *** *IHIK Interaction NS NS NS NS NS 5-25 Cover crop NS NS NS NS NS Amendment NS NS NS NS * Interaction NS NS NS NS NS 0-25 Cover crop NS NS NS NS NS Amendment NS NS * * * * * Interaction NS NS NS NS NS SCS 0-5 Cover crop NS * NS NS NS Amendment NS ** *** *8“? think Interaction NS * NS * * * 5-25 Cover crop NS NS NS NS NS Amendment NS NS NS NS NS Interaction NS NS NS NS NS 0-25 Cover crop NS NS NS NS NS Amendment NS NS * * * "' * NS Interaction NS NS NS NS NS * = P<0.05 ** = P<0.01 * * * = P<0.001 39 “gummcwfi 8? mm 8:832: .. m2 m2 m2 m2 m2 m2 m2 m2 . m2 m2 m2 *3 m2 a3 .6 2% 22 8% N- 82 2.8 as E 30 E $6 9% 64m _- Sam 2% 2a m- 88 28 8: 8 86 OS 2: c2 282 m2 can 2a m2 m2 m2 m2 m2 *3 .2: ca .5: m2 a3 2- 8mm $8 8% S- 38 8M: 28 _ cm o: 26 em 6:62 4 23 8mm 83 _- $8 38 3mm 3 8x 26 c8 9% 52 3 8mm 8mm 88 N 8mm 88 23 § 8: ca o2 _ Em 9:8 wow m2 m2 m2 m2 m2 m2 m2 m2 m2 m2 m2 m2 m2 93 m- can cm: 23 M2- 88 88 8mm 2 86 8” ca Sm 6Q m- a: 24m $8 2- 88 23m 2% mm 86 con 25 SW 6:62 w 80 m2 m2 2 m2 m2 m2 2 em as 0: m2 a3 2. 2mm 82 82 mm- 2:: 8mm 8: a- 8m 86 as com 682 o- 8% 8: 88 t- 88 8mm 8: we 36 2:. cow 8“ 82 h cam 86m $3 6- ES 8% 8% E o _ 2 82 o: _ 8m 9:8 . 08 .x. 23 .x. 936.. .x. 2&4. aglmgomggmfiaomflqflladfigfidgfiggadH :6 3o so 3m 56 no .5 .3252 mom was Umu 05 3 mafia?— Hmmm E no.5 b>oo 9C 23 $589885 :8 3 380% mu 8an So mmé Ea m~-m .mé 05 E E 8m 9808 Soho :82 .2 2an 40 Table 17. Interaction means for TN (Mg/ha) in the 0-5, 5-25, and 0-25 cm profiles of com-soybean and soybean-corn rotations at East Lansing from the spring of 2002 to the fall of 2004. CSC SCS In 2002 2003 2004 2004F Chg 2002 2003 2004 2004F Chg 0—5 ------------ Mg/ha --%-- -------------- Mg/ha --%-- R 0.57 0.6 0.67 0.51 -8 0.52 0.62 0.50 0.97 98 R+C 0.57 1.17 1.09 1.38 149 0.56 1.35 1.01 1.67 208 M 0.52 0.78 0.74 0.84 65 0.54 0.75 0.66 0.92 74 C 0.56 1.10 0.91 1.64 192 0.58 0.97 0.84 1.23 113 R+M 0.6 0.83 0.81 0.98 69 0.55 0.85 0.67 1.27 136 U 0.55 0.82 0.62 0.49 -10 0.55 0.63 0.45 0.54 -1 LSD NS NS NS NS NS NS 0.22 NS 0.83 182 5-25 R 2.50 - 2.21 1.93 -23 2.27 - 1.92 2.11 -8 R+C 2.37 - 2.20 2.17 -9 2.27 - 2.16 2.36 9 M 2.18 - 2.27 1.95 -11 2.33 - 2.05 2.43 7 C 2.61 - 2.73 2.38 -8 2.46 - 2.12 2.31 -6 R+M 2.62 - 2.44 2.09 -22 2.46 - 2.12 2.26 -9 U 2.43 - 2.45 1.83 -27 2.46 - 1.85 2.04 -18 LSD NS - NS NS NS NS NS NS NS Total R 3.06 - 2.81 2.58 -15 2.79 - 2.54 2.61 -7 R+C 2.94 - 3.37 3.26 11 2.83 - 3.52 3.37 23 M 2.69 - 3.05 2.69 0 2.86 - 2.80 3.08 10 C 3.17 - 3.83 3.29 5 3.04 - 3.09 3.15 4 R+M 3.22 - 3.27 2.90 -1 1 3.01 - 2.97 2.93 -3 U 2.97 - 3.36 2.45 -19 3.00 - 2.53 2.49 -17 LSD NS - NS NS NS NS - NS NS NS 41 Table 18. ANOVA for nitrate-N in the 0-5, 5-25, and 0-25 cm profiles of the CSC and SCS rotations CSC Profile (cm) Factor 2002 2003 Spring 2004 $112004 Chg 0-5 Cover crop *** *** NS NS NS Amendment NS *** NS NS NS Interaction NS ** NS NS NS 5-25 Cover crop *** *** NS NS NS Amendment NS ** NS NS NS Interaction NS * NS NS NS 0-25 Cover crop *** *** NS NS NS Amendment NS *** NS NS NS Interaction NS * NS NS NS SCS 0-5 Cover crop *** NS NS NS *** Amendment NS NS *** NS NS Interaction NS NS NS NS NS 5-25 Cover crop *** *** NS NS *** Amendment NS NS NS NS NS Interaction NS NS NS NS NS 0-25 Cover crop *** *** NS NS *** Amendment NS * *** NS NS Interaction NS NS NS NS NS * = P<0.05 * * = P<0.01 * * * = P<0.001 42 “585%? 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NO. .O. mm. :6. 6\6 80%. 6\6 680R a “..6OON VOON MOON NOON w..0 6:6OON fiodN. dOdN- NOON Eu mN-m So m-O Om. 2-0m 0-0m 3-0m 2-00 0-00 D00 .....- 8666660 .6 6..-.6... :6 6N-6 666 6-6 2.. ..6 66.6666. 6.66. .6N 6.66-.- 48 62 62 62 67. 62 66 66.6 66.6 66.6 N66 66 66.6 66.6 66.6 .6.6 .6 66.6 66.6 6..6 66.6 66 6N.6 .6.6 66.6 66.6 66 N66 A .6.6 66.6 66.6 6. 66.6 6N.6 6..6 66.6 62 62 62 67. 62 .6 66.6 6N.6 .6.6 66.6 6N 66.6 66.6 66.6 66.6 .N 66.6 66.6 66.6 N66 6 66.6 .6.6 NN.6 6N.6 6N 66.6 66.6 66.6 66.6 6N ...6 66.6 66.6 6N.6 62 67. 62 62 62 N6 66N 66.. 66.. 66.. 66 6N.N 66.. 66.. .6.. 66 6..N 66.. 66.. 6N.. 66. 66N .6.N 66.. 66.. 66 6N.N 6N.N 66.. 66.. 6- 66.. 66.. 66.. 66.. --66-- .6.-..66. 660 .6666N 666N 666N N66N demo-£2 OZ OZ OZ OZ OZ Ov ON..6O .6.N-NO ONON VOOO Om OO.NO O0.0N O0.0N O0.00 NN N0.00 O. .ON OYON NOOO ON ON.ON OTON NOON OO.NO NO EONO Om.ON .6N-.6N VONO ON O0.0N OO. .N O..ON O0.00 OZ OZ OZ OZ OZ .O ...NO OO.O.6 ONOO NO. ..6 Ow O..OO O..mm .N.OO NO...6 O. Omdm O0.00 O0.00 NOOO O. N0.00 mmém OOOO ON.O.6 Om ON.OO OO.NO ...NO m..m .6.6. OO. .O OO. . m NN.OO NN.O.6 OZ OZ OZ OZ OZ .N m . .NN O0.0. ON.ON N0.0. ON O. .NN OYON .6.6-O. ONO. OO NO..6N NOON O0.0. ONO. OO OOON NO. .N ON.ON O0.0. 6O O0.0N .0.0N m..N. .N.O. .6- N0.0. OOON O0.0. ON.O. --66-- 6&6: 30 a vOON mOON NOON con-.60 OO. 2-00 0-00 D-0O 2-00 0-00 300 SEN DO. 2-00 0-00 D10O 3.00 0-00 3-00 6.N-6. DO. 2-0m 0-00 3-0m 3.00 0-00 3-00 6.-O .666N ..6 ..66 2.. 6. N66N ..6 666.66 2.. 6.66 6.66.660 .6 66.66... .66 6N-6 .666 .6N-6 .6-6 6... 616.662.5666... .666 006 .6N 6.66... 49 Table 27. POM-C fraction of the 0-5 and 5-25 cm soil profiles at Chatham in the spring of 2002 and fall of 2004. 0-5 cm 5-25 cm 0-25 cm _T_rt 2002 2004 (Lg 2002 2004 th 2002 2004 Chg ------ kg/ha------- --%-- ------kg/ha------- --%-- ------kg/ha------- --%-- CC-U 4010 6090 -1 1 4690 16920 755 1 1300 20530 51 CC—C 3640 1 1430 219 4840 21350 955 8590 32780 400 CC-M 3430 8720 146 7560 13070 198 10820 21790 189 SC-U 3200 8830 179 5310 1 1220 687 8520 20050 182 SC-C 3130 12620 487 . 3390 18180 680 6140 30800 382 SC-M 4990 7480 53 1570 14230 830 6540 21710 255 LSD l 180 NS NS NS NS NS NS NS NS 50 VN ONO OZ OZ ON. NN NNOO N. ON OONN .ON. .N. 0.0V NO.N VOO. OOO. VN NO.N NNON NOV. ONN. ON .VON OOON ON .N N .O. OO. ONOO VNON N.ON OOV. ON OOON OONN OO.N NOO. OV VOO OZ OZ .O. NN .NO. OOO. NOV. OOV. ON OOON ON. . ONN. VOO . O- OO O . NON. NNO NVV. ..- NO.. V.V. ONO. VOO. OV .NN. OOO. NOO. .NN. O- 0.0. .ON. NOV. OOO. .NO 0.0NO OZ OZ OZ VON 0.00N. O.N .O. O.NN 0.00 OOO O.NO .N 0.000 V.N V.NO ON. O.NON O. .VO. O.NO 0.0N .O. O.VNO 0.0VV. 0.00 O..O OON 0.00.N O.NOO O.NO V.NN O O. 0.000 O.NOO. ..ON ..NN 1.x.-- 6566. wa0 LVOON VOON OOON NOON ...65 OZ ONO0.0 OZ OZ OZ OO OOO O.N ON. . .N OO. NOV .ON VO. NNN O. VON OON ON. .ON NN OOO .O. VON OON OO . OOV .ON .ON .ON O. OON O . N NON ONN OZ 0.0000 0.00 OZ OZ .O OON OO. OV. OV. V. . NNO ON. O. . OO. N OO. .V. NO. ON. NN ONN OO. OO. OO. OO. OOO OO. NV. .N. O. ON. OV. NV. OO. OZ 0.0 OZ OZ OZ NN NO NO 0.0 NO OON O.V. ..O 0.0 O-O NO V.O 0.0 O .O O .O VO 0.0 ..O O.V N.N NO. O... NO V.O 0.0 O. 0.0 0.0 0.0 0.0 --66-- 6566.. w..0 mVOON VOoiN OOON NOON 2-86-£2 GO. E-0O 0-00 D-0O 3.00 0-00 D00 BEN GO. 2-0m 0-00 D-0O 2-00 0-00 3-00 6.N-O 6.66 .6.-06 0-06 2-06 2-00 0-00 2-00 6-6 6H .666N ..6 ..66 2.. 6. N66N 66 66.666 6... .666 ...6.6660 .6 66.66... so 6N-6 666 .6N-6 .6-6 2.. 6. .656... 6.6666. 6..6 2-6.66.2 .6N 6.666 51 Table 29. Average daily temperatures at East Lansing and Chatham, MI. East Lansing Chatham“ Month 2002 2003 2004 30 yr Am 2002 2003 2004 30 yr Avg °C January 08 -8.0 -8.4 -5.7 -5.9 -11.2 -4.4 -9.0 February -1.1 -6.9 -4.8 -4.6 -5.7 -13.3 -6.6 -8.0 March -0.5 0.6 3.7 0.8 -7.9 6.4 -2.1 -3.5 April 9.0 7.8 9.5 8.1 2.3 1.8 3.0 4.1 May 1 1.2 12.6 14.8 14.2 7.4 9.9 9.2 10.6 June 20.5 17.3 18.0 19.4 16.7 16.5 14.3 15.4 July 22.8 20.9 20.3 21.5 20.9 18.3 16.3 18.6 August 21.1 21.3 18.4 20.6 18.3 19.1 15.5 17.9 September 18.6 16.0 17.9 16.7 15.5 15.9 16.3 13.5 October 8.3 9.2 10.1 10.6 3.3 7.3 7.8 8.3 November 2.5 5.1 4.4 3.7 -3.4 0.5 2.1 0.8 December -2.8 -0.8 -2.5 -2.8 -5.4 -3.6 -4.8 -5.8 * Temperatures for 2002 and January-June 2003 at Chatham are from the NWS at Marquette, 30 miles NW of Chatham. Table 30. Total monthly precipitation at East Lansing and Chatham, MI. East Lansig Chatham” Month 2002. .2001 20.04. 30 yr ALg 2002 2003 2004 30 E Avg mm January 10.4 6.1 6.9 35.6 27.9 17.8 35.3 50.0 February 38.9 10.4 12.3 30.7 135.9 49.0 61.7 42.4 March 41.2 38.3 69.3 53.1 144.8 85.1 80.3 49.5 April 55.6 78.5 14.0 71.4 129.5 88.6 53.1 62.5 May 120.9 103.6 205.0 69.3 79.5 156.7 111.8 80.0 June 53.9 37.3 89.2 89.9 96.8 41.1 48.0 91.7 July 95.0 35.8 101.6 76.7 86.1 70.1 79.8 90.4 August 35.6 46.2 87.1 79.2 78.0 27.9 117.1 90.4 September 13.2 65.5 26.7 63.5 145.0 139.4 39.4 105.7 October 31.5 46.7 49.0 55.9 129.5 82.8 130.1 82.3 November 34.5 1 18.4 80.8 56.4 53.3 60.5 50.6 78.7 December 25.9 37.3 38.6 46.5 14.2 32.5 95.8 60.2 * Temperatures for 2002 and J anuary-June 2003 at Chatham are from the NWS at Marquette, 30 miles NW of Chatham. 52 Literature Cited Anderson, S.H., C.J. Gantzer, and J .R. Brown. 1990. Soil physical properties after 100 years of continuous cultivation. J. Soil Water Conserv. 45:117-121. Balesdent, J, and M. Balabane. 1996. 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SSSAJ 68:507-513. 58 CHAPTER 2 COVER CROP AND SOIL AMENDMENT EFFECTS ON GREENHOUSE GAS FLUXES IN SILAGE CORN — SOYBEAN CROPPING SYSTEMS AT TWO DIFFERENT LATITUDES INTRODUCTION Mitigating the accumulation of greenhouse gases (GHG) in the atmosphere is essential to the protection of the Earth’s climate. Accumulation of GHG in the atmosphere may lead to global warming causing climate change around the world. Temperate regions may move farther north and south of the equator causing significant changes in the ability of certain areas to produce agricultural crops. Agriculture has played a major role in the increase of GHG carbon dioxide (CO2), nitrous oxide (N20) and methane (CH4). N20 and CH4 have approximately 300 and 20 times the global warming potential of C02 on a mole to mole basis (CAST 2004; Izaurralde et al. 2004). However, C02 has been the main focus for greenhouse gas mitigation due to the increase in atmospheric concentration from 280 ppm to 370 ppm since the mid-18005. and therefore has the greatest effect on global warming. C02 and N20 flux increases after tillage events and CH4 is a main byproduct of livestock production, specifically cattle. Agriculture affects atmospheric CO2 concentrations through consumption of fossil fuels, clearing of forested lands for food production (Wallace et al. 1990) and alteration of SOC levels by agricultural management practices. Population increases and industrial expansion have also resulted in increased atmospheric C02 concentration (Warneck 1988; Holland1978). N20 emissions are largely attributed to nitrification and denitrification of N added to the soil to maintain crop productivity (Rochette et al. 2004). Agricultural activities such as rice 59 cultivation and livestock are major contributors to CH4 emissions however, soils generally act as a sink. Short sighted farming practices have resulted in loss of an estimated 421:1 x 109 Mg of carbon from soils of the United States, and 78i12 x 109 Mg from the world’s soils, a large fraction of which ended up in the atmosphere (Lal 1999). Soils play a major role in the global carbon budget not only because of the large amount of carbon stored in soil, with estimates ranging from 1395 to 1636x108 Mg (Post et al. 1992; Schlesinger 1984) but also because the annual flux of CO2 to the atmosphere from soil is 10 times the amount of CO2 contributed by fossil fuel usage (Post et al. 1990). Soils can serve as both a source and sink for atmospheric C02, therefore soil and crop management can affect the global balance of CO2 (CAST 2004). Approximately one-third of the atmospheric CO2 that has accumulated since pre- industrial times is derived from land use practices that involve soil disturbance and removal of vegetation. Storage of soil organic carbon (SOC) is a balance between carbon additions from non-harvested portions of crops and organic amendments, and carbon losses, primarily through organic matter decomposition and release of respired C02 to the atmosphere (Huggins et al. 1998). Additions and losses of carbon are regulated by agricultural practices such as crop rotation (Janzen et al. 1992), residue and tillage management (Havlin et al 1990), and fertilization (Bloom 1982; Paustian et al. 1992). Agriculture plays a major role in the global fluxes of GHG and has been promoted as a partial means for slowing further increases in radiative forcing through the potential for soil carbon sequestration in cropping systems under reduced tillage (Paustian 1995; Lal et a1. 1999) and organic management regimes (Drinkwater et al. 1998). Conservation of SOC should be a 60 goal in production agriculture to decrease agricultural GHG emissions. It is possible to conserve SOC through appropriate choices of tillage, fertility, residue management, and cropping systems. Such management of SOC should decrease agricultural CO2 emissions through reduced SOC decomposition, increased sequestration of atmospheric GHG, and reduced fossil fuel consumptions (Robinson et al. 1996). The objectives of this study were to investigate the effect of rye cover crop, composted manure, and fresh manure on GHG emissions in no-till cropping systems consisting of corn and soybean rotations and determine the best management practices utilizing a whole accounting process for GHG. MATERIAL AND METHODS Field experiments were conducted near East Lansing (N 42.43, W 84.28) and Chatham (N 46.29, W 86.76), MI over a three year period beginning in the fall of 2001. Soil at East Lansing was a mixture of Aubbeenaubbee-Capac sandy loams (Fine-loamy, mixed, mesic Aeric Ochraqualfs) and Colwood-Brookston loams (Fine-loamy, mixed mesic Typic Argiaquolls and Typic Haplaquolls). Chatham soil was a Trenary fine sandy loam (Coarse-loamy, mixed frigid Alfic Fragiorthods). Experimental design was a randomized complete block with four replications at each location. Treatments were arranged as a 2x3 factorial at East Lansing. Factors consisted of rye vs. no rye, and compost amendment vs manure amendment vs no amendment. Prior to experiment establishment at East Lansing the site was under a com- soybean rotation with conventional tillage. Corn was planted in 2001, harvested as silage and no-till production practices were implemented when the winter rye cover crop was planted. The site was split into two rotations, com-soybean-com (CSC) and soybean- 61 com-soybean (SCS). Treatments at East Lansing were; winter rye cover crop (R) alone or in combination with either composted manure (R+C), or fresh manure (R+M), composted manure (C) alone, fresh manure (M) alone, and an untreated check (U) applied to both rotations. The Chatham site was an alfalfa field prior to experiment establishment. The experiment at Chatham consisted of two rotations, continuous silage corn (CC) and a forage soybean—silage corn rotation (SC). A winter rye cover crop was planted after removal of forage soybean in 2002. Treatments consisted of composted manure (C), liquid dairy manure (M), and an untreated check (U) applied to both rotations. Plot size varied between locations; plots at East Lansing were 6.1 x 12.2 m with 76 cm wide rows of corn or 38 cm wide rows of soybean and plots at Chatham were 18.3 x 18.3 m wide with 76 cm wide rows of corn or soybean in 19 cm wide rows. Planting dates, and harvest dates can be found in Table 31. Winter rye was terminated approximately two weeks prior to planting with glyphosate (840 g ae/ha) at East Lansing and glufosinate (140 g ai/ha) at Chatham. Solid beef manure and composted manure were applied in the spring and fall of each year through the spring of 2004 at East Lansing (Table 32). Liquid dairy slurry and solid composted manure were applied in the spring of each year at Chatham (Table 33). Greenhouse gas flux from the soil was determined using semi-pennanent sampling chambers placed in each plot. Chambers were polyvinyl chloride (PVC) rings 25 cm in diameter and 10 cm in height with a beveled edge on the bottom to ease placement. Chambers were inserted about 5 cm into the soil. A PVC cap with a 90° plastic elbow in the center and a 10 cm piece of plastic tubing was placed over the 62 sampling chamber before sampling. A 10 cm wide strip of latex glued to the outside of the cap was folded down around the sampling chamber during sampling. A butyl-rubber O-ring was used to seal the latex strip tight against the chamber and to help hold the cap in place. A three-way stopcock permanently attached to the tubing allowed for mixing of the headspace atmosphere in the chamber. A disposable 20 mL polypropylene syringe attached to the stopcock was used to draw air from the headspace atmosphere. The syringe was filled then the air was injected back to mix the atmosphere; this was repeated a total of three times before collecting any samples. After mixing this atmosphere 20 ml of air was withdrawn and injected into a 10 ml exetainer which had a 25 gauge needle placed in the rubber septum to allow for excess air to be forced out. This flushed any air trapped in the vial when capped out. This was repeated three times before removing the needle from the septum and filling the exetainer until pressurized. Gas samples were collected at random times throughout the growing seasons in 2002, 2003, and 2004 (Table 31). Samples were to be collected at scheduled times but due to technical problems with the analytical equipment samples were collected when possible and not all samples collected were analyzed. Samples were collected afier the cap was placed on the sampling chamber and at approximately 48 minute intervals up until 144 minutes afier placing the cap. Gas samples were analyzed using a HP5 890 Series 11 gas chromatogrpah (Hewlett PackardPalo Alto, CA 94304). CH4 was analyzed with a flame ionization detector (300 degrees C), while N20 was analyzed with a 63Ni electron capture detector (350 degrees C). CO2 was analyzed using an infrared gas analyzer. Gases for both CH4 and N20 were separated on a Poropak Q column (1.8 m, 63 80/100 mesh) at 80 degrees C. Carrier gas for CH4 was nitrogen, while carrier gas for N20 was argon/methane (90/10). Soil temperature at the 10 cm depth was measured each time a gas sample was collected and soil moisture to a depth of 15 cm was measured when the first and last samples are collected. Soil moisture was measured using a TRIME® TDR (MESA Systems, Medfield, MA 02052) moisture meter which measured moisture on a volume/volume basis. Three measurements were taken within 0.6 m of the canister and averaged. Height of the sampling chamber plus the cap was measured on four sides to determine the volume of the headspace. GHG flux was calculated using the following equation: F =(C/ T)*((V*M)/(A* Vmoi)) Where (C/ T) is rate of change of chamber concentration of gas X, V is the chamber volume, M is the molecular weight of gas X, A is the soil area covered by the chamber, Vmol is the volume of a mole of gas X. This equation provides umol of gas X/min/cm2 which was converted to g gas X/day/ha. Annual flux rate was calculated by averaging the measured daily flux rates and multiplying by 180 d for East Lansing and 132 d for Chatham. Growing season was determined to be the time between the 30 y average last spring freeze (-2°C) and first fall freeze. In this step N20-N and CH4-C were converted to C02 equivalents using 20 yr time horizon factors of 275 for N20 and 62 for CH4 (CAST 2004). Global warming calculation for soil carbon accumulation was determined using the following equation: X g C02/m2/yr=(((x| kg C/m2 — x2 kg C/m2)/x3)*(4400 g C02/12 kg c» where x. = soil C in treatment X in the fall of 2004 64 x2 = soil C in the Untreated in the fall of 2004 x3 = period of accumulation in years GWP for inputs were obtained from values published by West and Marland (2002) and IPCC (1997). Values take into account fuel for production and transportation of seed, chemical, and fertilizer. Flux fiom manure production was calculated using 47 kg methane head-1 y-l and original manure before composting was calculated at a rate of 118 kg head-1 y-l. The difference between the manure and compost-manure is that the manure came from beef while the compost-manure came fi'om dairy cows. CO2 and total carbon loss during the composting procedure was calculated and included in the flux rate. GWP values for inputs included in this study can be found in Table 34. Net GWP for treatments were calculated with the following eqution: Net GWP = Soil C GWP + Soil GHG flux + Input GHG flux — (Residue carbon - mineralized carbon) The residue carbon — mineralized carbon is to adjust for residue carbon added to the system but that is not part of the SOC or released as GHG. In some treatments large portions of the applied carbon still remain on the soil surface and therefore should not be counted against the GWP of the treatment. By subtracting the mineralized carbon from the residue carbon it was possible to determine the amount of carbon left on the surface. RESULTS AND DISCUSSION Ancillary measurements Average daily temperatures at East Lansing and Chatham during the growing seasons were i 3 °C of the 30 yr average (Table 35). Total monthly precipitation 65 compared to the 30 yr averages at East Lansing and Chatham during the growing seasons were more variable (Table 36). Soil temperature was significantly affected by cover crop and soil amendment treatment in 2003 and 2004 at East Lansing though all treatments were within 2 °C of each other at every sampling (Tables 37 and 38). When cover crop was significant the rye treatments had higher soil temperature than the non-rye treatments. Compost and manure generally had lower soil temperatures than the no amendment treatment. There were differences between compost and manure also however, there was no distinguishable pattern. The lower soil temperatures of the amended treatments were probably due to the insulating affect of the material. The application of the organic material produced a buffer zone between the soil surface and the sun protecting the soil from direct sunlight therefore decreasing the ability of the sunlight to heat the soil. It is possible that lower soil temperatures in the amended treatments may have slowed mineralization of organic matter but it is hard to estimate since the temperatures were only different by a couple of degrees at most. Soil moisture was also significantly affected by cover crop and amendment treatments at East Lansing (Table 37). Manure, compost and rye usually had higher soil moisture content than treatments without either soil amendment or rye cover crop (Table 39). A similar argument to the one made above about the protection the amendments provide the soil from the sun can be made here. Keeping the soil cool will result in less evaporation of water from the soil surface. The organic matter in the amendments is also much better at retaining water than the soil so when it rains more is absorbed in those treatments than the treatments without amendments. The same could be said for the rye 66 cover crop. The root biomass of the terminated rye cover crop may provide additional soil moisture by absorbing water during precipitation events and holding it in the soil profile longer. Soil temperature and moisture at Chatham were also different among treatments (Table 40). Similar to the results at East Lansing, treatments containing compost and manure had lower soil temperatures and higher soil moistures. Daily GHG Flux Daily flux rates of N20, C02, and CH4 were significantly affected by the application of soil amendments, cover crop, or the interaction of the soil amendment and cover crop at certain sampling dates at East Lansing in 2003 and 2004 (Table 41). Soil amendment significantly affected C02-C flux on five of seven sampling dates in 2003 for both rotations and on five of six and four of six sampling dates for the CSC and SCS rotations, respectively in 2004 (Table 41 ). Manure emitted more C02-C than either compost or no amendment in both rotations when soil amendment was significant (Table 12). Emissions from compost were lower or similar to the no amendment treatment in the CSC rotation both years except for June 7, 2004 and in the SCS rotation in 2003. In 2004 in the SCS rotation compost had higher emission rates of C02-C than no amendment except on August 11. These data suggest that the use of compost in place of manure would be beneficial due to the large differences in C02-C emissions. The reason for this large difference is due to the prior decomposition of the manure during the composting procedure. During composting the majority of easily degraded organic matter is decomposed leaving more recalcitrant organic matter. Therefore it could be expected that fresh manure applied to 67 the field would have a much higher C02-C flux than compost. Hao et al. (2004) found that composting straw bedded manure resulted in a loss of 52.8% total carbon during the process and actually released more C02-C to the atmosphere than the initial total carbon content of the manure. This will be discussed in more detail in the TOTAL ANNUAL GHG FLUX section. Cover crop significantly affected C02-C flux on two and five of the thirteen sample dates in the CSC and SCS rotations, respectively (Table 41). The rye cover crop treatment increased C02-C flux compared to non-rye treatments (Table 42). Soil temperatures tended to be warmer under the rye cover crop however on the sampling dates with significant differences between the two levels of the cover crop soil temperature was not significantly different. Results from the 19 April 2003 sampling were the most surprising since the rye cover crop was alive in the sampling chamber during the sampling. It was expected that the rye would utilize the C02 in the chamber for photosynthesis and cause a reduction not an increase in C02 concentration. Higher C02-C flux was not surprising from 18 May 2003 through the remainder of the season due to the availability of the rye cover crop biomass for decomposition after being terminated. Significant interaction between soil amendments and cover crop occurred on 3 May and 18 May 2003 in both rotations and on 27 July 2004 in the CSC rotation (Table 11). Rye plus manure (RM) resulted in the highest C02-C flux in both rotations on 3 May and 18 May 2003 followed by the rye alone treatment (Table 43). Compost (C) and Untreated (U) had the lowest level of C02-C flux on as expected due to the smaller 68 concentration of easily decomposable carbon in those treatments. Similar to results from 2003, RM had the highest C02-C flux on 27 July 2004 in the CSC rotation. Multiple soil N sources can result in N20 production and emission including mineral fertilizers, manure, crop residues, and biological fixation by legumes (Bremner 1997). N20 is naturally produced in soils as an intermediate during microbial nitrification (Bremner and Blackmer 1981) and denitrification (Dejwiche 1981). N20-N was affected by soil amendment on three of seven sampling dates in 2003 and one sampling date in 2004 in the CSC rotation, and on four of seven samplings dates in 2003 and four of six sampling dates in 2004 for the SCS rotation (Table 41). Nitrification and denitrification of N that is added to the soil to sustain crop productivity are responsible for the majority of N20 emissions (Rochette et al. 2004). When soil amendment was significant, manure had higher N20-N emissions than no amendment except for on 18 May and 9 October 2003 in the SCS rotation (Table 44). Manure and compost had similar N20-N emissions on most sampling dates. Manure emitted 12.7 g N20-N ha'l day'1 more than compost on April 19, 2003 in the CSC rotation while in the SCS rotation the difference was only 2.7 g N20-N ha"l day". This large difference is probably best explained by the previous crop. 2003 was the second year of the three year rotation so the previous crop in the CSC rotation was com and in the SCS rotation was soybean. Mineralization of soybean root biomass probably contributed to the higher N20-N emissions from SCS rotation in early April. According to Rochette et al. (2004) N20 emissions after soybean harvest and early in the following growing season indicated that soybean crop residues can induce significant N20 69 production in soils. Manure and compost were applied on 8 April 2003 (Table 31) which may have also contributed to the high levels of N20-N released. Cover crop treatment affected N20-N emission on 3 May 2003 in the SCS rotation with rye significantly reducing N20-N emissions (Tables 41 and 44). Rye cover crop tended to have lower N20-N emissions in April and May, higher emissions in June, and similar emissions in July through October to non-rye treatments. Lower emiSsions in April and May were probably due to the use of available soil nitrogen by the rye while growing. The spike in June was likely due to e mineralization of the rye biomass after being terminated resulting in a release of N20-N. Rye cover crop actually resulted in mitigation of N20-N on 24 April 2004 in the SCS rotation. Interaction between cover crop and soil amendment occurred on 3 May 2003 and 24 April 2004 in the CSC rotation (Table 41). Manure had the highest flux of 39.0 g N20-N ha" day'1 on 3 May 2003 followed by compost (13.7 g) both of these were significantly different than the other treatments (Table 45). The addition of rye cover crop to the manure and compost treatments reduced N20-N emissions by 95 and 97% respectively, on 3 May 2003. When the rye cover crop was growing it generally reduced N20-N emissions though not always significantly. This was probably due to utilization of the available soil nitrogen before it could be denitrified. Sanchez et al. (2004) reported that winter wheat may have reduced N03-N leaching losses during the winter and and spring by drying the soil and immobilizing mineralized N from soybean residues. N20 emissions were usually highest in the treatments that were the coldest and wettest corresponding to work by McKenney et al. (1993) who found that denitrification losses were higher with no-till compared to conventional till due to higher soil moisture. 7O CH4-C emissions were influenced by soil amendments on 14 June 2003 in the SCS rotation and on 27 July 2004 in both rotations (Table 41). Agricultural soils generally act as a sink for CH4-C except under anaerobic conditions (CAST 2004). Therefore it is interesting that manure resulted in emissions of 0.7 g CH4-C ha'l (lay'l on 14 June 2003 in the SCS rotation and 1.3 and 0.2 g on 27 July 2004 in the CSC and SCS rotations, respectively (Table 16). Compost emitted 0.7 g CH4-C ha'l clay'l on July 27, 2004 in the SCS rotation. These emissions appear to be resulting from the soil amendment because when no amendment was applied atmospheric CH4-C concentration was mitigated. Soil moisture was 27 to 29% volume:volume (Table 49) so anaerobic conditions were not present to account for the CH4-C emissions. C02-C flux at Chatham was only different among treatments on 10 June and 14 September 2004 (Table 47). There was no obvious pattern to the differences among treatments on these two sampling dates; SC-M had the highest flux of C02-C on 10 June while SC-C had the highest flux on 14 September. Both were greater than the untreated and compost treatments. N20-N emissions differed among treatments on 3 July 2003, 15 July and 14 September 2004 (Table 47). Similar to C02-C no distinct pattern to the differences were evident. SC-M was highest on 3 July 2003, CC-M on 15 July 2004, and CC-C on 14 September 2004. The higher flux from SC-M in 2003 could be caused by the mineralization of the forage soybean roots from the 2002 crop as discussed earlier. CH4-C emissions were significantly different on 10 June and 15 July 2004 (Table 47). Mitigation of CH4-C was greatest with SC-U on 10 June and SC-C on 15 July. All 71 treatments mitigated CH4-C on 10 June while CC-U and CC-M emitted CH4-C on 15 July. TOTAL ANNUAL SOIL GHG FLUX Total annual soil GHG flux is the sum of all three greenhouse gases in CO2 equivalents emitted or mitigated over the period of a growing season. The growing season at East Lansing was calculated to be 180 days while at Chatham it was determined to be 132 days. Growing season length was determined by counting the days between the last spring freeze and the first fall freeze East Lansing Soil amendment had a significant effect on annual soil GHG flux (Table 48). Manure had the highest emission rate of 2678 g C02 m'2 y'I and was significantly greater than no amendment (1335 g) and compost (1099 g) in the CSC rotation (Table 48). Compost and no amendment treatments were not significantly different from each other. The same trend was present in the SCS rotation however; compost was significantly less than no amendment. Soil amendments significantly differed in the amounts of each gas they contributed toward the annual soil GHG flux in both rotations (Table 50). The proportion of the total annual C02 equivelent flux in the CSC rotation from CO2 was 93.19% with compost which was significantly less than that from manure and no amendment. Compost released significantly more N20 than either manure or no amendment. This contradicts the findings of Castellanos and Prattt (1981) who reported that during the composting process manure-N was stabilized through microbial assimilation and 72 humification resulting in a considerably slower rate of mineralization. Also, GHG were measured as soon as possible however, it is possible that the measured N20 flux is represented here smaller than the actual flux due to the inability to measure the large fluxes for N20 associated with soil thawing (Goodroad et al. 1984 and Christensen and Tiedje 1990). Trends in treatment differences for each gas were the same between rotations. Rye cover crop significantly increased GHG flux compared to no cover crop in both rotations (Table 48). Rye cover crop resulted in more C02 being released and less N20 than no cover crop. As discussed earlier the higher rate of C02 evolution is due to the decomposition of the rye biomass. Utilization of soil nitrogen by the rye cover crop during the fall and spring when N20 emissions are highest (Rochette et al. 2004) is the reason for no cover crop to have higher N20 emissions. Chatham Total annual soil GHG flux was lowest with CC-C which was significantly less than CC-M, SC-C, and SC-M (Table 49). SC-M had the highest GHG flux at 1876 g C02 rn'2 yr". SC rotation treatments had significantly higher GHG emissions than either the CC-U or CC-C treatments. It is possible that the inclusion of soybean in the rotation could increase the emission of N20 compared to continuous corn. Also as seen at East Lansing the inclusion of rye cover crop increased C02 emission compared to no cover crop. Soil GHG flux derived from the three gases was significantly different among treatments for CO2 and N20 (Table 51). SC-U released the most C02 which was significantly greater than CC-C, CC-M, and SC-C. An interesting result was that the 73 Untreated treatments in both rotations emitted the most C02. Considering the only additional carbon in these treatments was crop residue it was an unexpected result. However, when soil temperatures are considered the Untreated treatments generally had warmer temperatures than either the compost or manure treatments within the same rotation. These higher temperatures would have been conducive to increased decomposition of SOC. Proportion of the total annual GHG flux from N20 was highest with CC-M. SC- U and SC-M were significantly less than CC-M which could have been expected. At East Lansing rye cover crop decreased N20 emissions and the SC rotation at Chatham includes a rye cover crop. Also the manure at Chatham was liquid slurry so the nitrogen in the manure would have been more easily taken up by the cover crop shortly after application. Surprisingly, the total annual flux rates were pretty similar between locations. It was believed that Chatham would have a smaller flux of GHG than East Lansing. When averaged across treatments and rotations the total annual GHG flux at East Lansing was 1632 g C02 rn'2 y'lcompared to 1533 g C02 rn’2 y'l. However, when converted to a daily basis because of the difference in growing season lengths, the daily flux at Chatham (11.61 g CO2 m'2 d") exceeds that of East Lansing (9.07 g C02 111'2 d'l). Due to the shorter growing season Chatham has a lower annual flux rate but that does not mean that it is more suited for carbon sequestration than East Lansing. SOIL C GWP Soil carbon content changes were presented and discussed in the previous chapter. The means are presented here again as a function of the Untreated allowing for the 74 comparison of the soil amendments and cover crop effects to the effect of normal no-till practices (Table 48). Calculation of soil C GWP is simply made by subtracting the baseline soil C content from the ending soil C content, dividing by the period of accumulation, and converting the amount of carbon into its equivalent mass as CO2. Two different baselines were available to use with this experiment; 1) the initial spring 2002 carbon levels, or 2) the fall 2004 carbon level of the untreated. We chose to use the fall 2004 carbon level of the untreated as the baseline as this would allow us to compare the effect of the treatments to straight no-till instead of comparing all the treatments to conventionally tilled carbon levels from 2002. Soil amendments had a significant effect on Soil C GWP (Table 48). All treatments resulted in a potential to mitigate global warming in the CSC rotation (Table 48). Compost had the most significant affect with a mitigation potential of 2212 g C02-C m'2 y'1 which was greater than manure (1248 g) and no amendment (37 g). Similar to the CSC rotation, compost had the greatest effect on potential for mitigation in the SCS rotation followed by manure; however, no amendment resulted in carbon loss not gain. Cover CI'Op had no effect on soil C GWP in either rotation (Table 48). Soil C GWP seems to be greater in the CSC rotation than the SCS rotation, possibly due to more recalcitrant carbon in the corn residues compared to the soybean residue. All treatments appear to have the potential to mitigate global warming though there were no differences among treatments. Treatments containing compost had the highest potential of global warming mitigation. This result is not surprising since the compost treatment returns the most carbon to the system of any of the treatments. Residual carbon fiom organic inputs 75 Carbon applied as compost, manure, crop residue, or rye cover crop biomass can either be mineralized into SOC, decomposed into CO2, or remains on the soil surface in the form it was applied in. To accurately account for GHG mitigation, all of the carbon applied in the treatments needs to be accounted for. This was accomplished by subtracting the known amount of carbon incorporated into SOC (Fall 2004 SOC - Spring 2002 SOC) from the amount of carbon applied. With the mineralized portion of the applied carbon accounted for the decomposed portion needs to be removed, that is done by subtracting the annual soil GHG flux rate leaving the amount of carbon remaining as residue in the applied form which is used as a credit against global warming. Residual carbon minus the mineralized portion of the applied carbon is presented in Table 48. Soil amendment and cover crop both had significant effects on residual carbon levels. Manure resulted in the highest level of residual carbon remaining after removing the mineralized portion. All treatments had carbon remaining on the soil surface before subtracting the annual soil GHG flux. Results at Chatham differed from East Lansing in that more carbon was sequestered in the soil than was applied with the treatments therefore no residual carbon credit was given (Table 49). It is believed that the large amount of carbon sequestered in the soil at Chatham is due to the experimental site being an alfalfa period for a significant amount of time prior to the experiment. Alfalfa produces large amounts of root biomass which when mineralized would greatly affect the SOC content. Input GHG flux Average total annual input GHG flux for both rotations is in Table 48. The difference between rotations at East Lansing is due to two years of corn in the CSC 76 rotation, and the additional nitrogen fertilizer required for the corn crop. The high flux rate from compost is due to CO2 loss during the composting procedure. CO2 loss from composting was calculated by comparing total carbon levels before and after composting. Average loss of carbon during composting was 947.5 kg CO2 eq. Mg'l compost dry matter which is more than double the loss of C02 during composting reported by Hao et al. (2001 and 2004). This is still an underestimation of CO2 loss from composting since these calculations did not include the fuel used when the compost was periodically mixed. Net GWP Soil amendment and cover crop had significant impacts on net GWP (Table 48). Compost and manure resulted in similar mitigation potentials ranging between 708 and 1159 g CO2 m'2 y'I in the CSC and SCS rotations when residual carbon on the surface was accounted for. Compost and manure went from mitigating global warming to increasing the GWP when residual carbon is removed from the equation. Without credit for residual carbon, manure emits significantly more CO2 equivalents than compost. The addition of a rye cover crop significantly increased GWP of those treatments, mostly due to increased GHG flux from the soil. No significant differences were observed among treatments at Chatham for net GWP (Table 49). Compost did provide mitigation potential. Unlike East Lansing the compost was not actively mixed so the additional input GHG flux from that process is not missing here. However, there is still some GHG not accounted for from the composting process which would increase the GWP of the compost treatments. 77 CONCLUSIONS Compost treatments appear to have the most significant effect on soil carbon GWP while emitting less than half of the soil GHG flux than manure. Net GWP of compost was similar to that of manure though due to the high flux of GHG from the composting process. GHG emissions from soil though smaller during November through March compared to April through October still occur and should be included to be as accurate as possible when making decisions about best management practices. These questions need to be answered and included in the whole accounting process before recommending the use of compost or any other methods as a mitigation strategy of GHG. 78 Table 31. Dates of soil sampling, planting, herbicide application, and harvest at East Lansing and Chatham. East Lansing Chatham 2002 2003 2004 2002 2003 2004 Soil sampling Spring 0-25 19/4d 21/5 9/4 14/5 5/5 23/4 Fall 0-25 - - 9/1 1 - - 8/11 Spring deep - 22/5 19/6 - - - Planting Corn 23/5 22/5 13/5 12/6 20/5 17/5 Soybean 23/5 22/5 13/5 6/6 - 29/5 Cover crop 1/10/01 8/10/02 4/10/03 - 10/9/02 - Herbicide application Bumdown 5/5 8/5 3/5 - 30/4 - Gas sampling 1 8/68 19/4 24/4 3/7a 15/5 28/4 19/7a 3/5 7/6° 13/8a 29/5 9/6c 18/8" 18/5 14/6a 3/9b 13/6 24/68 1 1/9b 1/6 26/6 3/10b 7/7 15/7 14/6 12/7 28/8 27/7 16/7’r 27/7 11/8 25/8 11/8 14/9 9/10 25/8 Harvest Silage 12/9 17/9 14/9 3/ 10 7/ 10 11/10 Soy 28/9 11/10 8/10 5/9 - 14/9 Cover crop 8/ 5 9/5 5/5 - 5/5 - a Samples were collected but not analyzed b Samples were collected, analyzed, but not included in analysis cLarge gap between samplings is due to mechanical problems with gas chromatograph dDates expressed as day, month, year 79 machonmmonm £95 "m:o_§>o.fin< so» .558 58 mm @8855 $89 «.2 mg. a: an 32 5.: 8.? 3mm 3% one: new: $2 3.3 2% 3.2. 3.: 3% RE 3% 33m 2% £3 3% 43m _ gm 3% 8. K S? 8. E SN 3° 5. ”no $5 :3 $2 88 RS 22 2:3 :6 :5 «no ”2 Q2 83 E; 23 Sod 335 $6 mg 02 was 55 we: $3 $2 83 33 m2: 3.: 2: EN 8.: 8.8 an: 8.2 NS; 5. SEN SEN swim $4.8 Spa 852 84$ 34.8 3.3 898 new: 25% SEE SE» News. 83% 23% 85$ 8% 3.25 .SEE Hag—ado 9:532 26 mum—om 2:362 Eamfiom .mosm :omobmz 5530 2mm wEmqu “mam 8 members 28 83.. 8:58 .cozmozqmm “89:8 can 2:52: we 6:5 .mm 2an 80 Table 33. Date of amendment application, rate and analyses at Chatham Mflure Compost 15/5/02al 6/5/03 2004 17/5/02 6/5/03 7/5/04 Mg/ha Rate 8.220 3.870 5.670 41.770 8.980 8.980 0/. Carbon 2.96 2.25 1.54 7.91 20.28 10.24 Nitrogen 0.256 0.224 0.239 0.516 0.543 0.429 Phos. 0.055 0.037 0.038 0.152 0.173 0.109 Potasium 0.213 0.173 0.120 0.160 0.449 0.129 Moisture 93.74 96.81 94.95 70.18 65.87 78.0 Solids 6.26 3.19 5.05 29.82 34.13 22.0 C:N 11.56 10.04 6.44 15.33 37.35 23.87 aDates expressed as day, month, year Abbreviations: Phos, phosphorous Table 34. GHG flux from all inputs during crop production (adapted from West and Marland 2002 ) Crop Plantinga Seed Spraying(x2) Fertilizer Harvest g CO2 m'z Corn 0.679 2.15 1.96 1.24 1.65 Soybean 0.679 2.03 1.96 1.65 Rye 0.679 1.93 Amendment Application 2002 2003 2004 g C02 m' EL Manure 0.52 10.4b 9.9 4.1 EL Compost 0.52 2113.0b 1405.2 663.3 CH Manure 0.52 2.1 0.9 1.0 CH Compost 0.52 10.4 2.6 1.7 3 Includes fuel used for production and transportation of all products b Calculated using average values obtained from MWPS-l 8 (1985), and IPCC (1997) 81 Table 35. Average daily temperatures at East Lansigg and Chatham, MI. Month January February March April May June July August September October November December East Lansing Chathama 2002 2003 2004 30 yr Avg 2002 2003 2004 30 yr Avg °C -O.8 -8.0 -8.4 -5.7 -5.9 -l 1.2 -4.4 -9.0 -l .1 -6.9 -4.8 -4.6 ~5.7 ~13.3 -6.6 -8.0 -O.5 0.6 3.7 0.8 -7.9 -6.4 -2.1 -3.5 9.0 7.8 9.5 8.1 2.3 1.8 3.0 4.1 11.2 12.6 14.8 14.2 7.4 9.9 9.2 10.6 20.5 17.3 18.0 19.4 16.7 16.5 14.3 15.4 22.8 20.9 20.3 21.5 20.9 18.3 16.3 18.6 21.1 21.3 18.4 20.6 18.3 19.1 15.5 17.9 18.6 16.0 17.9 16.7 15.5 15.9 16.3 13.5 8.3 9.2 10.1 10.6 3.3 7.3 7.8 8.3 2.5 5.1 4.4 3.7 -3.4 0.5 2.1 0.8 -2.8 -0.8 -2.5 -2.8 -5.4 -3.6 -4.8 -5.8 8‘ Temperatures for 2002 and J anuary-J une 2003 at Chatham are from the NWS at Marquette, 30 miles NW of Chatham. Table 36. Total monthly precipitation at East Lansing and Chatham, MI. 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