NITROGEN AND PLANTING DATE EFFECTS ON LOW-PROTEIN SPRING BARLEY

Grain protein of barley (Hordeum vulgare L.) produced for malting often is greater than the industry's acceptable standards of 135 and 130 g kg(-1) for six-rowed and two-rowed barley, respectively. Environmental 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 traits of two experimental barley genotypes inherently low in grain protein with two barley cultivars currently grown in the U.S. Midwest. Agronomic 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 significantly increased grain protein, grain yield, soluble wort N, DP, and alpha-amylase activity, and decreased kernel weight, kernel plumpness, and fine-grind malt extract. Significant genotypes differences were observed for all traits. The N x genotype interaction was significant for all agronomic traits, soluble wort N, and DP. The standard cultivars had greater than the acceptable grain protein when fertilized with 150 or 200 kg N ha(-1). Delaying planting significantly decreased grain yield and fine-grind malt extract, Grain protein of the low-protein genotypes was within the Limit desired by the malting and brewing industry at all N rates and planting dates. Thus, protein levels acceptable to maltsters can be obtained for low-protein barley genotypes when excessive N is available and growing conditions are unfavorable.