title: Tillage, cropping systems, and nitrogen fertilizer source effects on soil carbon sequestration and fractions.
abstract: Quantification of soil carbon (C) cycling as influenced by management practices is needed for C sequestration and soil quality improvement. We evaluated the 10-yr effects of tillage, cropping system, and N source on crop residue and soil C fractions at 0- to 20-cm depth in Decatur silt loam (clayey, kaolinitic, thermic, Typic Paleudults) in northern Alabama, USA. Treatments were incomplete factorial combinations of three tillage practices (no-till [NT], mulch till [MT], and conventional till [CT]), two cropping systems (cotton [Gossypium hirsutum L.]-cotton-corn [Zea mays L.] and rye [Secale cereale L.]/cotton-rye/cotton-corn), and two N fertilization sources and rates (0 and 100 kg N ha(-1) from NH(4)NO(3) and 100 and 200 kg N ha(-1) from poultry litter). Carbon fractions were soil organic C (SOC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). Crop residue varied among treatments and years and total residue from 1997 to 2005 was greater in rye/cotton-rye/cotton-corn than in cotton-cotton-corn and greater with NH(4)NO(3) than with poultry litter at 100 kg N ha(-1). The SOC content at 0 to 20 cm after 10 yr was greater with poultry litter than with NH(4)NO(3) in NT and CT, resulting in a C sequestration rate of 510 kg C ha(-1) yr(-1) with poultry litter compared with -120 to 147 kg C ha(-1) yr(-1) with NH(4)NO(3). Poultry litter also increased PCM and MBC compared with NH(4)NO(3). Cropping increased SOC, POC, and PCM compared with fallow in NT. Long-term poultry litter application or continuous cropping increased soil C storage and microbial biomass and activity compared with inorganic N fertilization or fallow, indicating that these management practices can sequester C, offset atmospheric CO(2) levels, and improve soil and environmental quality.
authors.affiliation: Northern Plains Agricultural Research Laboratory, U.S. Department of Agriculture-Agricultural Research Service, 1500 N. Central Avenue, Sidney, MT 59270, USA. upendra.sainju@ars.usda.gov
authors.forename: Upendra M
authors.initials: UM
authors.lastname: Sainju
authors.forename: Zachary N
authors.initials: ZN
authors.lastname: Senwo
authors.forename: Ermson Z
authors.initials: EZ
authors.lastname: Nyakatawa
authors.forename: Irenus A
authors.initials: IA
authors.lastname: Tazisong
authors.forename: K Chandra
authors.initials: KC
authors.lastname: Reddy
mesh_terms: D018533:Biomass; D002244:Carbon / Q000737:chemistry*; D018556:Crops, Agricultural; D005308:Fertilizers; D003368:Gossypium; D009584:Nitrogen / Q000737:chemistry*; D012434:Secale; D003313:Zea mays
chemical_list: D005308:Fertilizers; D002244:Carbon; D009584:Nitrogen