Abstract
Wheat cultivar “Setokirara” has a high grain yield and a high bread making quality in western Japan. Although the grain yield is increased by heavy application of nitrogen fertilizer, the protein content in grain is often decreased. Nitrogen topdressing at later growth stages increased both the grain yield and the grain nitrogen content. The changes in nitrogen accumulation between vegetative organs and grain during the grain filling period need to be examined to keep the grain yield and grain protein content constantly high. We investigated the effect of topdressing at the spike formation stage (GS31) and that at anthesis (GS65) for “Setokirara”, “Nishinokaori” and “Norin 61” throughout three seasons. Topdressing at the spike formation stage made “Setokirara” accumulate more nitrogen in vegetative organs at anthesis than “Nishinokaori” or “Norin 61”, while grain yield was higher in “Setokirara” than in “Nishinokaori” or “Norin 61”. “Setokirara” showed lower content of grain nitrogen than “Nishinokaori” or “Norin 61” because of less nitrogen absorption from soil after anthesis and higher grain yield. Most of the applied nitrogen was absorbed before anthesis. “Setokirara” needs more nitrogen topdressing at anthesis to achieve higher nitrogen content in grain to increase grain yield.
