Effects of Seeding Rate and Nitrogen Application Rate on Grain Yield and Protein Content of the Bread Wheat Cultivar ‘Minaminokaori’ in Southwestern Japan

摘要

We examined the effects of seeding rate, 50 or 150 seeds m-2, nitrogen (N) application rate at active tillering and jointing, 4 and 2 g N m-2, respectively, or none, and N application rate at anthesis, 0, 2, 4, or 6 g N m-2, on grain yield and protein content of a bread wheat cultivar, ‘Minaminokaori’, during the 2004–2005 crop season in southwestern Japan. Grain yield was similar at a seeding rate of 50 and 150 seeds m-2. It was higher when 4 and 2 g N m-2 were applied at active tillering and jointing, respectively (4–2N), than when no N was applied at these stages (0–0N). However, it was not influenced by N application rate at anthesis. Grain protein content was similar at 50 and 150 seeds m-2. It was higher in 4–2N than in 0–0N. It was the highest when 6 g N m-2 was applied at anthesis, followed by 4, 2, and 0 g N m-2. The SPAD value at anthesis was higher at 50 than 150 seeds m-2, but leaf area index (LAI) at anthesis was similar at 50 and 150 seeds m-2 and protein content of grain was nearly the same at 50 and 150 seeds m-2 irrespective of N application rate at anthesis. LAI and the SPAD value were higher in 4–2N than in 0–0N and the protein content of grain was also higher in 4–2N than in 0–0N irrespective of N application rate at anthesis. Therefore, both LAI and the SPAD value may be important traits related to the N application rate at anthesis suitable for yielding wheat grain with a high protein content.