Submitted to: Soil and Water Conservation Society Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 11/15/2002
Publication Date: 12/3/2002
Citation: Halvorson, A.D. 2002. Carbon as a potential commodity: irrigated cropland. Colorado Chapter of the Soil and Water Conservation Society Proceedings. CD-ROM. Interpretive Summary:
Technical Abstract: Tillage, soil fertility, and crop rotation play a key role in soil carbon (C) sequestration. Intensive tillage practices generally used to manage crop residues and prepare a seedbed under irrigated conditions results in loss of soil organic C (SOC). Converting to a no-till (NT) system reduces SOC losses from wind and water erosion and improves soil C sequestration. A NT irrigated cropping system is expected to increase the amount of soil C sequestered by reducing the loss of residue C that occurs when tillage mixes the crop residue with the soil where microbes readily decompose the residue. Tillage, N fertility level, and crop rotation effects on the quantity of residue C returned to the soil in irrigated cropping systems is discussed. Increasing N level generally increases the amount of crop residue returned to the soil. Since the C content of most crop residues is relatively constant at about 40 to 45% C, increasing N level increases the amount of residue C returned to the soil. The quantity of crop residue returned to the soil varies with the crop grown. Corn had the greatest amount of above-ground residue C and onion the least residue amount of the crops investigated. Rate of residue decomposition will vary with the C/N ratio of the residue, with high C/N ratio residues decomposing at a slow rate. Corn cobs had C/N ratios of 90 to 120 while stalk residue had C/N ratios of 50 to 60; thus, corn cobs are visible for several years. The C/N ratio of crop residues generally decreases as N availability increases. Information presented can assist producers, crop consultants, NRCS, and others in estimating C inputs from crop residues in irrigated crop rotations.