PROTEIN-PRODUCTION AND NITROGEN-UTILIZATION BY BARLEY CULTIVARS IN RESPONSE TO NITROGEN-FERTILIZER UNDER VARYING MOISTURE CONDITIONS

In a 3-yr field experiment, six barley cultivars - one conventional height malting type, two semidwarf, two conventional height, and one short feed type - were grown at three sites. with six nitrogen application rates ranging from 0 to 200 kg ha-1, to determine the effects of cultivar and N level on N utilization under varying moisture conditions. Nine site-years of data were divided into three levels, low, moderate, and high. based on estimated moisture supply. As moisture level increased, protein concentration of the barley cultivars decreased, while protein yield and total N uptake increased. Cultivars with higher grain yield tended to be lower in protein concentration, but higher in protein yield, total N uptake and N use efficiency than those with lower grain yields. Differences among the cultivars in protein concentration were greater at low than high moisture levels, while differences due to N application were greater at high than low moisture levels. Within the range of N applied, nitrogen use efficiency decreased at high N levels under low and moderate moisture conditions, but was relatively constant at high moisture levels. Protein concentration response to N applications differed slightly among cultivars at all moisture levels, but cultivar by N level interactions in protein yield response only occurred under high moisture conditions. Cultivars respond similarly to N applications in terms of straw N concentration, total N uptake and N use efficiency.