Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/1998
Publication Date: N/A
Interpretive Summary: Nutrients are released to the environment as crop residues decompose. Availability of these nutrients to subsequent crops depends on the rate of release (leaching and decomposition), immobilization by soil microorganisms and length of time before the next crop is planted. In the southern High Plains, where fallow cropping systems and irrigation are the predominant practices, differences between nutrient management may be necessary for optimum use of nutrients released from crop residues. This study evaluated biomass loss and N, P, and K release from alfalfa, corn, grain sorghum, spring wheat and winter wheat residues on the soil surface in irrigated and non-irrigated treatments. Nutrient release was similar under irrigated and nonirrigated conditions. Losses of N and P were slow taking nearly one year to release 70 to 80% while loss of K was rapid and nearly complete within 4 months for all residues. Similar release of nutrients in irrigated and nonirrigated conditions indicate that different nutrient management strategies would be needed primarily due to the long fallow period for nonirrigated areas. However the amounts of nutrients released represented only 10 to 30 % of the amounts needed for subsequent crop production and should be considered in nutrient applications.
Technical Abstract: Residue management retains crop residues on the soil surface where decomposition rates are slower than for incorporated residues. Understanding nutrient loss from surface residues is important for improving nutrient use by subsequent crops. Quantities of N, P, and K remaining in surface residues of alfalfa, corn, grain sorghum, spring and winter wheat were measured from 9/91 to 8/92. Irrigated and non-irrigated plots were used to determine water regime impacts. Water regime did not influence mass loss, N or P dynamics but did affect K loss. Loss of N occurred during the first month followed by N immobilization for all residues except alfalfa, which had net mineralization. P dynamics indicated net mineralization from alfalfa, immobilization into corn and winter wheat, and little change for spring wheat, and grain sorghum. Potassium decreased rapidly, with the rate being 2 to 3 times faster from alfalfa than for other residues. Intermediate irrigation had a greater effect on K loss than did frequent and non-irrigated treatments; due to wetting and drying frequency. Immobilization and slow mineralization of N and P from nonlegume residues could limit availability to a subsequent crop, but this would not be the case for K.