Al-Kaisi, Mahdi (Iowa State Univ., Department of Agronomy, 2104 Agronomy Hall, Ames, IA, 50011; Phone: 515-294-8304; Fax: 515-294-9985; Email: malkaisi@iastate.edu)

Agricultural Production Practices - Effect on Soil Carbon Dynamics and Carbon Dioxide Emission

M.M. Al-Kaisi*, M.A.Licht, X. Yin

Soil carbon change and carbon dioxide emission due to different tillage systems need to be evaluated to encourage the adoption of conservation practices to sustain soil productivity and protect the environment. We hypothesize that soil carbon storage and carbon dioxide emission respond to conservation tillage differently from conventional tillage because of their differential effects on soil properties. This study was conducted from 1998 through 2001 to evaluate tillage effects on soil carbon storage and carbon dioxide emission in Clarion-Nicollet-Webster soil association in a corn [Zea mays L.]-soybean [Glycine max (L.) Merr.] rotation in Iowa. Treatments included no-tillage with and without residue, strip-tillage, deep rip, chisel plow, and moldboard plow. No-tillage with residue and strip-tillage significantly increased total soil organic carbon and mineral fraction carbon at the 0- to 5- and 5- to 10-cm soil depths compared with chisel plow after 3 years of tillage practices. Soil carbon dioxide emission was lower for less intensive tillage treatments compared with moldboard plow, with the greatest differences occurring immediately after tillage operations. Cumulative soil carbon dioxide emission was 19 % to 41% lower for less intensive tillage treatments than moldboard plow, and it was 24% less for no-tillage with residue than without residue during the 480-hour measurement period. Estimated soil mineralizable carbon pool was reduced by 22% to 66% with less intensive tillage treatments compared to moldboard plow. Adopting less intensive tillage systems such as no-tillage, strip-tillage, deep rip, and chisel plow and better crop residue cover are effective in reducing carbon dioxide emission and thus improving soil carbon sequestration in a corn-soybean rotation.