Growth and Yield Response of Soft White Common Spring Wheat (SWCSW) Varieties under Different Nitrogen Fertilizations and Plant Growth Regulators Applications

Abstract

Application of plant growth regulators (PGRs) is often reported beneficial in wheat to achieve various targets including lodging resistance. However, research evidence on the application of PGRs in Soft White Common Spring Wheat (SWCSW) varieties is limited particularly in Columbia Basin. Therefore, our objectives were to evaluate the effects of PGRs on SWCSW varieties exposed to different nitrogen (N) application levels. Two widely grown SWCSW varieties, Louise and Diva were planted for two growing seasons using split plot design with four replications. Crop growth (stem height and diameter), yield and yield attributes (grain numbers per head, head numbers per fit, grain weight), quality characteristics (test weight, protein content) and lodging score were recorded following the application of PGRs at tillering (GS21-26), stem elongation (GS30-32), and flag leaf emergence (GS37-39) stages combined with high N fertilization. No lodging was observed during first season whereas it was witnessed during second season, and we observed a variable but positive response particularly under application of CC-C, TE, CC-BC and CC-AB. An increase in stem diameter and reduction in stem height were observed under PGR application which indirectly contributed to stem strength and reduced lodging. Although impact of PGRs application on grain numbers, head numbers grain yield and grain weight were non-significant and variable, we observed an improved performance of these attributes such as higher grain yield was observed under application of CC-B and CC-BC. The grain yield of Louise and Diva was similar at low and high N input. These results indicate that application of 168 kg N ha-1 is sufficient for an acceptable grain productivity and to gain agronomic returns. As we observed a significant seasonal impact and variations in the performance of SWCSW varieties, future research should consider long term evaluations to evaluate the impacts of PGRs on soft white common spring wheat varieties.