Peanut Residue Carbon and Nitrogen Mineralization under Simulated Conventional and Conservation Tillage

Abstract

Core Ideas Recommendations of 22 to 67 kg N ha−1 credit after peanut are not substantiated. Decomposition of peanut residue in North Carolina and Alabama fit double exponential decay equations. Nitrogen credit to wheat was 14 to 24 kg N ha−1, but to cotton was 2 to 10 kg N ha−1. Nitrogen credits differ by location and placement of residue. Nitrogen credits should be specified to which crop they are applied. Residue management is an important aspect of cropping systems. Availability of plant residue N to succeeding crops depends on N mineralization rates. Cooperative Extension currently recommends 22 to 67 kg N ha−1 credit to subsequent crops following peanut (Arachis hypogaea L.), but these recommendations are not supported in the literature, nor do they specify if the credit is applied to a subsequent winter or spring crop. The objective of this study was to assess N release rates from residues of three peanut cultivars (NC V‐11, GA 02‐C, and ANorden) at two placements (surface and 10‐cm deep) and two locations representing northern and southern extremes of U.S. commercial peanut production (North Carolina and Alabama). Litterbags containing the equivalent of 3.5 Mg ha−1 were placed in a completely randomized design at both locations with four replications and retrieved periodically up to 335 d after application. Results were fit to single or double exponential decay models. Based on empirical models, the N credit to a subsequent winter wheat (Triticum aestivum L.) crop was estimated at 14 to 19 kg N ha−1 when peanut residues were buried after harvest, and 19 to 24 kg N ha−1 when on the soil surface. When N credits were applied to a subsequent cotton (Gossypium hirsutum L.) crop, they were reduced to 2 to 9 kg N ha−1 (buried) and 6 to 10 kg N ha−1 (surface). Current recommendations are higher than the results obtained in this study suggest and warrant re‐examination.