Effect of the Late-stage Intensive Nitrogen Fertilization on Growth, Yield and Grain Protein Content of the Wheat Cultivar ‘Fukuhonoka’ for Japanese Noodles in Okayama Prefecture

Abstract

The effects of late-stage intensive nitrogen fertilization (LSINF) on growth, yield, and grain protein content (GPC) of Japanese wheat cultivar ‘Fukuhonoka’ were investigated in Okayama Prefecture, Japan. Our results showed that LSINF at the jointing stage (i.e., GS31) with the same total nitrogen fertilizer amount as the conventional fertilization resulted in up to 10% increase in yield compared to the conventional fertilization. Although GPC on the LSINF was higher than that of the conventional fertilization, it did not reach the standard value of 9.7% or higher for Japanese noodles. Therefore, we applied additional nitrogen at the flag leaf extraction stage (i.e., GS38). The spike number, aerial part weight, and harvest index increased depending on the amount of additional nitrogen applied. The additional application of nitrogen at GS38 maintained SPAD value of the uppermost expanded leaf at a high level during a month after heading time. As a result, the grain yield further increased as compared with that without additional nitrogen application. Additional nitrogen application also resulted in the grain protein content of the standard value of 9.7% or higher. Intensive nitrogen fertilization at GS31 and GS38 resulted in high yield and appropriate GPC of ‘Fukuhonoka’ in Okayama Prefecture, Japan.