Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2004
Publication Date: 7/1/2004
Citation: Allmaras, R.R., Clapp, C.E., Linden, D.R. 2004. Corn-residue transformations into root and soil carbon as related to nitrogen, tillage, and stover management. Soil Science Society of America Journal. 68:1366-1375. 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. Significant changes in total soil organic carbon stored within the top 30 cm of soil occurred only because of the larger carbon retention under no-till management. Findings on the soil organic carbon storage under corn as related to tillage and residues provide valuable information to environmental scientists, engineers and consultants concerning present global carbon budgets.
Technical Abstract: Soil organic carbon (SOC) is sensitive to management schemes of tillage, residue (stover) harvest, and N fertilization. Most of these estimates use long term field trials but a major problem is to estimate SOC responses to the unharvestable root, root exudates, and crown. Most often a shoot-to-root-ratio is used, and these are empirical. Natural C isotope abundance (¿13C) and total C, measured in paired (stover harvest and stover returned) corn (Zea mays L.) plots was used to estimate corn-derived SOC changes as a function of C produced by the corn crop. The contribution of the non-harvested biomass (crown, roots, root exudates) to the SOC pool was estimated using these paired plots of stover harvested and returned as with grain harvest. This estimate was tested in 3 tillage treatments by 2 nitrogen fertilizations by 2 residue managements. After 13 years of continuous corn, a no-tillage system retained 24% of the available source C in the SOC pool in the top 30-cm of soil, while moldboard and chisel plow tillage retained 11 and 14%, respectively. The C from non-harvested corn biomass was equivalent to about 1.6 times that of the C in stover. Under no-tillage, the returned stover residue contributed significantly to the build-up of SOC in the near surface soil while under both tilled systems this contribution was more uniformly distributed in the upper 30 cm. Significant changes in total SOC stored within the top 30 cm of soil occurred only because of the larger C retention under no-till. Annual C returns required to maintain SOC under any tillage system are nearly equal to the C harvested in grain (5 Mg ha-1 yr-1).