YIELD RESPONSE OF SEMIDWARF AND CONVENTIONAL HEIGHT BARLEY CULTIVARS TO NITROGEN-FERTILIZER UNDER VARYING MOISTURE CONDITIONS

A 3-yr field experiment was conducted to evaluate the response of semidwarf and conventional height barley cultivars to N fertility. Six spring barley cultivars (one conventional height malting type, and two semidwarf, two conventional height, and one short feed type) were grown at three sites with nitrogen applications ranging from 0 to 200 kg ha-1. The 9 site-years of data were divided into three classes, low, moderate, and high, based on estimated moisture supply. Under low moisture conditions, grain yield response to applied N was low, but yield increased with applications to 200 kg ha-1. Under moderate conditions, grain yield response to applied N was greater, but yield did not increase above 80 kg ha-1 of fertilizer N. No interaction was observed between barley cultivar and grain yield response to nitrogen under low or moderate moisture supply, although yields of Virden were higher than those of the other cultivars at most nitrogen levels. Under high moisture conditions, the feed barley cultivars showed a higher grain yield response to applied N than did the malting barley cultivar, Bonanza. The short-strawed cultivar, Heartland had a greater increase in yield with N application than the other cultivars. With a high moisture supply, yield of Bonanza did not increase with fertilizer N applications above 120 kg ha-1, while yield of the other cultivars was still increasing with application of 200 kg N ha-1. Differences among cultivars in grain response to N application were largely due to differences in the harvest index.