NITROGEN AND PLANTING DATE EFFECTS ON LOW-PROTEIN SPRING BARLEY

Grain protein of barley (Hordeum vulgare L.) produced for malting ofte n is greater than the industry's acceptable standards of 135 and 130 g kg(-1) for six-rowed and two-rowed barley, respectively. Environmenta l conditions such as low rainfall and high temperatures after anthesis often cause increased grain protein. This study was conducted at four dryland environments in North Dakota over 2 yr to compare the effects of N fertilization and planting date on agronomic and malt quality tr aits of two experimental barley genotypes inherently low in grain prot ein with two barley cultivars currently grown in the U.S. Midwest. Agr onomic traits evaluated were grain protein, grain yield, kernel weight , and kernel plumpness. Malt quality traits evaluated were fine-grind extract, soluble wort protein, diastatic power (DP), and alpha-amylase activity. Nitrogen rates ranged from 0 to 200 kg ha(-1). Nitrogen sig nificantly increased grain protein, grain yield, soluble wort N, DP, a nd alpha-amylase activity, and decreased kernel weight, kernel plumpne ss, and fine-grind malt extract. Significant genotypes differences wer e observed for all traits. The N x genotype interaction was significan t for all agronomic traits, soluble wort N, and DP. The standard culti vars had greater than the acceptable grain protein when fertilized wit h 150 or 200 kg N ha(-1). Delaying planting significantly decreased gr ain yield and fine-grind malt extract, Grain protein of the low-protei n genotypes was within the Limit desired by the malting and brewing in dustry at all N rates and planting dates. Thus, protein levels accepta ble to maltsters can be obtained for low-protein barley genotypes when excessive N is available and growing conditions are unfavorable.