Analysis of Nitrogen Accumulation and Use in Bread and Durum Wheat

Abstract

Since a significant portion of applied soil N is lost by leaching and denitrification, it is desirable to breed crop cultivars with improved N use efficiency. This study was undertaken to determine the influence of soil N supply on genotypic variation for preanthesis and postanthesis shoot N accumulation, the effect of preanthesis N and grain N yield on postanthesis N accumulation, and N use efficiency. A set of 12 bread (Triticum aestivum L.) and two durum (T. turgidum L. var durum Desf.) wheat genotypes was studied over three planting dates in 2 yr with three N levels within each planting date on a Ramona type A sandy loam (coarse fine‐loamy, mixed thermic Typic Haploxeralf). Differences among genotypes for shoot N accumulation before and after anthesis became obvious at the highest soil N level. At this level, some genotypes either stopped accumulating or showed a net loss of shoot N between anthesis and maturity, which appeared to be associated with superior preanthesis N accumulation capacity and reduced grain N yield of such genotypes. Uptake efficiency (total shoot N/soil N supply) became slightly more important than utilization efficiency (grain yield/total shoot N) in determining N use efficiency (grain yield/soil N supply) with increasing soil N supply. Nitrogen harvest index (grain N yield/total shoot N) fully explained the reduced contribution of utilization efficiency at higher soil N levels. We suggest that bread wheat genotypes G4843 and ‘Anza’ should be crossed in an attempt to recombine the superior N accumulation capacity of the former with the superior grain yield of the latter to develop a cultivar with improved N use efficiency.