抄録
Nitrogen fertilizer as ammonium sulfate was applied to soybeans [Glycine max (L.) Merrill cv. Bonminori and Enrei] at flowering stage to examine effects of application rate and placement on seed yield and protein yield. Seed yield of "Bonminori" was increased from 306g/m2 to 360g/m2 by the application of supplemental nitrogen in the range of 0gN/m2 to 18gN/m2. The result indicated that higher rate than that at basal application was required for the significant increase (20 to 30 g/m2 of seed yield. When development of roots was poor and seed yield was low without the supplemental nitrogen, the effect of the application on the seed yield was remarkable. In "Enrei", furrow placement of the supplemental nitrogen at one side of plant rows allowed the larger yield response than both-sided furrow placement and also as deep application (40cm deep in soil) did than surface application. Nitrogen content of seeds was also increased with application rates of the supplemental nitrogen in the similar way as seed yield. The increase was mainly due to increase of protein-nitrogen. Ratio of 11S globulin to 7S globulin of seeds was not affected by the increase of protein content caused by the application of the supplemental nitrogen.
