Soil carbon and nitrogen sequestration as affected by long-term tillage, cropping systems, and nitrogen fertilizer sources

Disposal of poultry litter, a widely available organic manure in the southeastern USA because of a largescale poultry industry, is a major concern because of its contamination in surfaceand groundwater through N leaching and P runoff. Application of poultry litter in no-tilled intensive cropping system could increase soil C and N sequestration compared with the conventional-tilled system with inorganic N fertilization and reduce environmental contamination. We evaluated the 10-year effects of tillage, cropping systems, and N fertilizer sources on crop residue (stems + leaves) production and soil bulk density, organic C (SOC), and total N (STN) at the 0–20 cm depth in Decatur silt loam (clayey, kaolinitic, thermic, and Typic Paleudults) in northern AL, 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 NH4NO3, and 100 and 200 kg N ha 1 from poultry litter) in randomized complete block with three replications. Rye was grown as winter cover crop and corn as residual crop without tillage and fertilization. Mean crop residue returned to the soil from 1997 to 2005was greater in rye/cotton–rye/cotton–corn than in cotton–cotton– corn and greater with NH4NO3 than with poultry litter at 100 kg N ha . While SOC and STN concentrations at 10–20 cm after 10 years were not influenced by treatments, SOC and STN contents at 0– 20 cm were greater with poultry litter than with NH4NO3 in NT and CT. These resulted in a C sequestration rate of 510 kg C ha 1 year 1 and N sequestration rates of 41–49 kg N ha 1 year 1 with poultry litter comparedwith 120 to 147 kg C ha 1 year 1 and 23 to 3 kg N ha 1 year , respectively, with NH4NO3. Cropping and fertilization sequestered C at 730 kg C ha 1 year 1 and N at 67 kg N ha 1 year 1 compared with fallow and no-fertilization in NT. Tillage and cropping system did not influence SOC and STN. Long-term poultry litter application or continuous cropping can sequester C and N in the soil compared with inorganic N fertilization or fallow, thereby increasing soil quality and productivity and reducing the potentials for N leaching and greenhouse gas emission. Published by Elsevier B.V.