title: Carbon supply and storage in tilled and nontilled soils as influenced by cover crops and nitrogen fertilization.
abstract: Soil carbon (C) sequestration in tilled and nontilled areas can be influenced by crop management practices due to differences in plant C inputs and their rate of mineralization. We examined the influence of four cover crops {legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye (Secale cereale L.)], biculture of legume and nonlegume (vetch and rye), and no cover crops (or winter weeds)} and three nitrogen (N) fertilization rates (0, 60 to 65, and 120 to 130 kg N ha(-1)) on C inputs from cover crops, cotton (Gossypium hirsutum L.), and sorghum [Sorghum bicolor (L.) Moench)], and soil organic carbon (SOC) at the 0- to 120-cm depth in tilled and nontilled areas. A field experiment was conducted on Dothan sandy loam (fine-loamy, siliceous, thermic Plinthic Paleudults) from 1999 to 2002 in central Georgia. Total C inputs to the soil from cover crops, cotton, and sorghum from 2000 to 2002 ranged from 6.8 to 22.8 Mg ha(-1). The SOC at 0 to 10 cm fluctuated with C input from October 1999 to November 2002 and was greater from cover crops than from weeds in no-tilled plots. In contrast, SOC values at 10 to 30 cm in no-tilled and at 0 to 60 cm in chisel-tilled plots were greater for biculture than for weeds. As a result, C at 0 to 30 cm was sequestered at rates of 267, 33, -133, and -967 kg C ha(-1) yr(-1) for biculture, rye, vetch, and weeds, respectively, in the no-tilled plot. In strip-tilled and chisel-tilled plots, SOC at 0 to 30 cm decreased at rates of 233 to 1233 kg C ha(-1) yr(-1). The SOC at 0 to 30 cm increased more in cover crops with 120 to 130 kg N ha(-1) yr(-1) than in weeds with 0 kg N ha(-1) yr(-1), regardless of tillage. In the subtropical humid region of the southeastern United States, cover crops and N fertilization can increase the amount of C input and storage in tilled and nontilled soils, and hairy vetch and rye biculture was more effective in sequestering C than monocultures or no cover crop.
authors.affiliation: USDA-ARS-NPARL, Sidney, MT 59270, USA. usainju@sidney.ars.usda.gov
authors.forename: Upendra M
authors.initials: UM
authors.lastname: Sainju
authors.forename: Bharat P
authors.initials: BP
authors.lastname: Singh
authors.forename: Wayne F
authors.initials: WF
authors.lastname: Whitehead
authors.forename: Shirley
authors.initials: S
authors.lastname: Wang
mesh_terms: D000383:Agriculture / Q000379:methods; D002244:Carbon / Q000378:metabolism*; D018556:Crops, Agricultural / Q000254:growth & development*; D004784:Environmental Monitoring; D005308:Fertilizers; D005845:Georgia; D009584:Nitrogen / Q000378:metabolism*; D009930:Organic Chemicals / Q000737:chemistry / Q000378:metabolism*; D012987:Soil / Q000032:analysis*; D013997:Time Factors
chemical_list: D005308:Fertilizers; D009930:Organic Chemicals; D012987:Soil; D002244:Carbon; D009584:Nitrogen