Nitrogen Recovery by Corn from Nitrogen‐15 Labeled Wheat Residues and Intact Roots and Soil

Abstract

Abstract Conservation tillage systems, which maintain crop residues on the soil surface, are becoming more widely used. Crop residues serve as ground cover to reduce soil erosion and act as a sink‐source for plant nutrients. A better understanding of the processes involved in crop residue decomposition and N release in these systems is needed to develop more efficient residue and fertility management practices. A greenhouse study was conducted to determine N availability to corn ( Zea mays L.) from wheat ( Triticum aestivum L.) residues and intact roots and soil as affected by residue placement. Tracer 15 N was used to quantify the N recovered by corn from wheat residues and intact roots and soil. Wheat residues were either surface‐placed or incorporated in a Mexico silt loam (fine, montmorillonitic, mesic Udollic Ochraqualf) in pots with intact wheat roots. Residue placement significantly influenced the amount of 15 N recovered by corn from wheat residues but not from intact roots and soil. Corn 15 N recovery was significantly higher from incorporated residues than from surface residues; however, this was not reflected in the dry weight. Corn dry weight was 12% greater from surface residues than from incorporated residues. Higher yield from surface residues was attributed to a more constant optimum soil water content.