Growth and Grain Yield of Wheat in Relation to Differences in Soil Groups : III. Effects of the additional application of nitrogen or phosphoric-acid on the tiller growth and grain yield

Abstract

This research was conducted with three varieties (Asakazekomugi, Norin 61 and Norin 64) in Red Soil, Thick High-humic Andosol and Light-colored Andosol. In Red Soil the survival and grain yield of tillers was increased in three varieties by the three times of nitrogen topdressing. In Norin 61 and Norin 64 nitrogen topdressing increased extremely the emergence of T_R (tillers that emerged since the middle of the tillering stage, and their survival rate was very low). This higher emergence rate of T_R resulted in rank growth and increased lodging. In Asakazekomugi, nitrogen topdressing did not increase the emergence of T_R and lodging, resulting in higher grain weight per spike. In the two Andosols, the emergence of tillers was increased and the grain yield of T_c (coleoptile tiller), T₁, T₂, and T₃ (tillers in axils of the first, second and third main stem leaves) were increased by the additional application of 50kg/10a P₂O₅. Norin 64 had higher emergence and survival rate in T₁ and higher yield than the other two varieties in Andosols which were phosphoric-acid-deficient soils. Since the T₁ of Asakazekomugi and Norin 61 emerged and were ear-borne by the additional application of 50kg/10a P₂O₅ in Andosols, the varietal difference of grain yield was smaller than control.