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 NH₄NO₃ 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 NH₄NO₃ 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 NH₄NO₃ 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 NH₄NO₃ Poultry litter also increased PCM and MBC compared with NH₄NO₃ 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 CO₂ levels, and improve soil and environmental quality. Copyright © 2008. American Society of Agronomy, Crop Science Society of America, Soil Science Society . American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America