Potential of low-protein genotypes for nitrogen management in malting barley production

Nitrogen (N) levels in the soil and N fertilization are among the major factors that affect grain protein concentration (GPC) in malting barley (Hordeum vulgare L.). The use of inherently low protein cultivars might be an advantage in conditions of excessive soil N or in situations where N is applied to maximize yield. In the present study, eight malting barley genotypes were grown under dryland and irrigated conditions to compare their response to four rates of nitrogen (N) application (0, 30, 60 and 120 kg/ha). The trials were carried out in 1998 and 1999 at a site in the Wimmera region of Victoria, Australia, which has a Mediterranean-type environment. Seasonal differences accounted for a large proportion of the observed variation in GPC, but had little influence on variation in grain yield. Nitrogen application significantly increased grain yield and GPC, and decreased kernel weight and plumpness. The rate of response for grain protein was higher under dryland than irrigated conditions, but the genotype-by-nitrogen interaction was not significant under both conditions. To further characterize genotypic response, the method of pattern analysis was used to identify groups of genotypes showing a similar pattern in their response to N application and to relate the patterns to available knowledge about the inherent GPC of their grains. The eight genotypes were clustered into three entry groups, corresponding to low, moderate and high-protein genotypes. There was little difference among groups in the rate of response to N application. However, the genotype group with inherently low GPC maintained the lower protein over those with higher grain protein at the different rates of N application. Under dryland conditions, the low-protein genotypes tended to have less plump kernels with increasing rates of N application than the respective high-protein group.