|Layese, Meg - UNIVERSITY OF MINNESOTA|
Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 23, 2000
Publication Date: N/A
Interpretive Summary: Tillage and crop residue management to influence carbon storage in US croplands can have a major impact on global warming, but long-term field experiments are needed to project carbon storage amounts and controlling conditions. In this 13-year field experiment with continuous corn, it was shown that nitrogen fertilization, corn residue (stover) management, and tillage system all significantly influenced the carbon cycle and carbon storage in the soil of a semi-humid climate in the northern portion of the Corn Belt. This information will be assembled and used by an ARS Task Force to provide an advisory on the potential reduction of atmospheric carbon dioxide related to cropland agriculture.
Technical Abstract: Long-term field experiments are among the best means to predict soil management impacts on soil C storage. Soil organic C (SOC) and natural abundance **13C (delta**13C) were sensitive to tillage, crop residue and nitrogen (N) management during 13 years of continuous corn (Zea mays L.). Contents of SOC in the 0- to 15-cm layer in tilled [moldboard (MB) and chisel (CH)] plots decreased slightly with years of corn cropping after an alfalfa/oat and pasture history irrespective of protocol for stover return. Amounts of SOC in no-till (NT) plots with stover removed remained nearly unchanged at 95 Mg ha**-1 with time, while that with stover returned increased about 14 percent. The delta**13C values increased steadily with years of cropping in all treatments; the NT with residues returned had the highest increase. The N fertilization effects on SOC and delta**13C were most evident when residue was returned to NT plots. In the 15- to 30-cm depth, SOC storage decreased and delta**13C values increased with years of cropping under NT, especially when stover was removed. There was no consistent temporal trend in SOC storage and delta**13C values in the 15- to 30-cm depth when plots received annual tillage. The amount of corn residue retained in SOC storage was influenced by all three management factors. Corn-derived SOC in both the 0- to 15-cm and the 15- to 30-cm layers of the NT system was largest with 200 kg N ha**-1 and crop residue return. The MB and CH tillage systems did not influence soil storage of corn-derived SOC. The corn-derived SOC as a fraction of SOC after 13 years fell into three ranges: 0.05 for NT with stover removed, 0.15 for NT with stover returned, and 0.09 to 0.10 for treatments with annual tillage.