Spring Wheat Response to Enhanced Ammonium Supply: I. Dry Matter and Nitrogen Content

Abstract

AbstractSpring wheat (Triticum aestivum L.) grain dry matter (DM) has been increased in previous greenhouse experiments through the use of a nitrification inhibitor (NI), which provides an enhanced ammonium supply (EAS). The objective of this research was to determine, under greenhouse conditions, the effect of EAS on the accumulation and partitioning of DM and N at several stages of plant development and on the yield components (heads plant−1, kernels head−1, and kernel weight). Enhanced NH4 supply increased plant DM at 18 d after plant emergence, boot stage, 7 d after anthesis, and maturity. Enhanced NH4 supply did not alter the relative partitioning of DM among leaf, stem, and grain at any stage of development. Effects of EAS on plant and grain DM at maturity increased with increasing N rate. At the highest N rates, grain DM was increased 18 and 6% in two experiments. Nitrogen and moisture stress appeared to alter grain DM response to EAS. Increased grain DM was associated with an increased number of heads plant−1. Kernels head−1 were decreased with EAS, but kernel weight was not affected. Consequently, EAS increased heads plant−1 more than grain DM. At growth stages prior to maturity, EAS increased plant N uptake. At maturity, plant N uptake was slightly and inconsistently affected by EAS; however, the proportion of plant N in the grain was increased by EAS. This indicated a greater translocation of N from the stem to the grain with EAS. In general, increased spring wheat grain DM is associated with proportional increases in plant DM throughout plant development, but not necessarily with proportional increases in plant N uptake. Heads plant−1 is the only yield component increased positively by EAS and thus warrants further research.