SPRING SOIL WATER, PRECIPITATION, AND NITROGEN FERTILIZER: EFFECT ON BARLEY GRAIN PROTEIN CONTENT AND NITROGEN YIELD

Abstract

Available soil water before seeding (Ws), growing season precipitation (GSP), and fertilizer N level (N) were used to describe the protein content and N yield of barley grain. The regression models were developed from 5 yr of field data where various Ws levels were achieved by fall irrigation or by covering plots with PVC sheet to exclude fall and winter precipitation and snowmelt. Protein content was increased greatly by N rates especially when Ws was low (< 100 mm). Protein contents of 15–19% were obtained with 100–180 kg N/ha and Ws less than 100 mm. Although protein content could only be maintained below the maximum level for malting barley by restricting N rates to 20–50 kg/ha if Ws was less than 100 mm, N rates greater than 100 kg/ha could be used if Ws was high (> 150 mm). The protein content was relatively insensitive to GSP levels in this study. Although N yield in the barley grain ranged from negligible levels to more than 100 kg/ha, the incremental N yield was generally less than 30% of the rate of fertilizer N applied.