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

Abstract

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. Th e 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 aft er application. Results were fi t 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 aft er 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.

Peanut residues supply minimal plant‐available nitrogen on a major soil series in the USA peanut basin

“…Peanut residue placement did not affect C and N mineralization dynamics in residue‐amended soils, which agrees with findings from other laboratory incubations involving peanut residues (Balkcom et al., ; Smith & Sharpley, ) but contradicts reports from field studies showing that incorporated peanut residues mineralized C and N more rapidly than surface residues (Mulvaney et al., ; Sakonnakhon et al., ). These discrepancies may be due in part to different O 2 levels between laboratory and field environments.…”

“…Mulvaney et al. () estimated that peanut residues loaded at 3.5 Mg ha −1 would mineralize 40.5–57.3 kg N ha −1 (66%–81% of total residue N), from the same varieties and soil series used in the present study, over a 252‐day period under field conditions in Alabama, and that a large proportion of mineralized N would be released within the first 30 days of application. Comparing these findings to results from the present study reveals that a substantial portion of N mineralized from peanut residues is not accounted for in soil inorganic N measurements.…”

“…Findings from this study highlight the large discrepancy between estimates of N mineralization that are based on chemical extractions from peanut residue‐amended soils and estimates that are made by direct measurements of mass loss from peanut residues (Balkcom et al., ; Jani et al., ; Mulvaney et al., ). Mulvaney et al.…”

“…Peanut ( Arachis hypogaea L.) is a globally important cash crop that provides the additional benefit of contributing to soil nitrogen (N) pools by engaging in biological N fixation. Depending on cultivar and irrigation regime, peanut biomass can accumulate 46–183 kg N ha −1 (Meso, Balkcom, Wood, & Adams, ; Pimratch et al., ; Sharma & Behera, ), a portion of which is mineralized during subsequent crops (Mulvaney, Balkcom, Wood, & Jordan, ). Although peanut residues may contain substantial amounts of N, previous studies in the south‐eastern USA have suggested that N contributions from peanut residue to subsequent crops are negligible.…”

“…Previous studies focusing on N mineralization from incorporated and surface‐applied peanut residues have not considered residue components separately (Jani et al., ; Mulvaney et al., ; Sakonnakhon et al., ). Thippayarugs et al.…”