Wheat Nitrogen Use Efficiency in a Bed Planting System in Northwest Mexico

Abstract

Wheat (Triticum aestivum L.) in the Yaqui Valley, northwest Mexico, is planted as a winter crop using a raised‐bed, furrow‐irrigated system and high fertilizer N rates. Wheat residues are usually burned before planting maize (Zea mays L.) as a summer crop. The N use of wheat planted following conventional tillage using a raised‐bed system (CTB) incorporating both wheat and maize residues was compared with wheat planted using permanent raised beds (PB) under four residue management treatments: all straw (wheat and maize) left as stubble, straw partly removed (maize residues removed; wheat residues retained), all straw removed, and all straw burned. Each wheat plot was split into seven N fertilizer (Nf) treatments: five applied at planting (0, 75, 150, 225, and 300 kg ha−1) and two at the 1st node stage (150 and 300 kg ha−1). Maize received a uniform Nf application of 150 kg ha−1. The N use efficiency of wheat with 150 kg Nf ha−1 at the 1st node stage was superior to basal applications at the same rate. Permanent bed–all straw left as stubble and PB–all straw burned had the highest average wheat grain yields (5.57 and 5.52 Mg ha−1, respectively), N use efficiency (28.2 and 29.1 kg grain kg−1 of N supply, respectively), and total N uptake (133 and 137 kg ha−1, respectively). Total N uptake for 150 and 300 kg Nf ha−1 at the 1st node stage was 14 and 8% greater, respectively than at planting. In most tillage–straw treatments, 21% of the difference in wheat grain yields was due to the N supply component at low N rates; at high N rates, 97% was due to N use efficiency.