ESTIMATING NITROGEN REQUIREMENTS FOR IRRIGATED MALTING BARLEY

The production of marketable malting barley requires careful N management to meet the quality standards set by the malting industry. Nine field trials were conducted over an eight-year period at four locations to develop N fertilization guidelines for irrigated malting barley. Residual soil NO3-N (0 to 60 cm) ranged from 15 to 103 kg N/ha. Nitrogen fertilizer was applied preplant as either urea or NH4NO3 at rates ranging from 0 to 269 kg N/ha. Maximum yields were obtained when the sum of residual plus applied N (available N) was above 110 kg N/ha. However, the percentage of plump kernels generally fell below acceptable levels (85%) when available N exceeded 135 kg N/ha. Grain protein exceeded acceptable levels (12%) when available N was above 210 kg N/ha. Stem NO3-N sufficiency levels were determined from high-yielding barley with acceptable quality parameters. At the three-leaf stage, the barley stem NO3-N sufficiency level was approximately 6,000 .mu.g/g and decreased to about 1,000 .mu.g/g at the eight-leaf stage.