Effects of additional fertilizer on the yield and quality of malting barley

To lessen environment-induced variability in grain crude protein content, which determines malting quality, an appropriate technique for applying additional fertilizer is needed. Therefore, we studied the effects of additional fertilizer on the yield and malting quality of three major cultivars of malting barley cultured in Tochigi Prefecture: "Amagi Nijo","Mikamo Golden" and "Sukai Golden". The feasibility of estimating grain crude protein content by growth analysis was also examined. The results indicated that when the total amount of nitrogen fertilizer was held constant application of additional fertilizer at later stages resulted in grain crude protein contents higher than those obtained with the basal fertilizer only. However, late application of additional fertilizer did not increase the yield. On the other hand, when the total amount of fertilizer was increased by additional fertilizer (application of additional fertilizer at the stalk stand stage) remarkable increases in the yield and grain crude protein content were observed. Application of additional fertilizer caused a drop in the quality of malt extract, but only because of the increase in grain crude protein content. When compared on the basis of crude protein content there was no difference between the lot with basal fertilizer only and the lot with separate fertilizer applications. Therefore, malting quality was negatively correlated with crude protein content regardless of the method of fertilizer application. In our test plots, a significant positive correlation was observed between grain crude protein content and the leaf color index 20 days after the stalk stand. From regression analysis of two years' data, it could be concluded that a leaf color index in the range of 43.5-45.0 20 days after the stalk stand was correlated with grain crude protein contents in the range of 10.0-11.0%, which is the appropriate level for malting. However, as there were yearly fluctuations, further examination is needed to establish a reliable high-precision method of prediction.