Abstract
In warm regions of Japan, methods of nitrogen fertilizer application and the effect of organic matter application were studied for direct sowing culture of the high-yielding rice variety"Akenohoshi"on well-drained paddy field. Grain yield of Akenohoshi attained the maximum value by dressing 16 to 18 kg of nitrogen per 10a. As to the methods of nitrogen application, dressing at the beginning of irrigation, dressing at the neck-node differentiation stage, which resulted in the higher yield in spite of the lower percentage of ripened grains. The yield of Akenohoshi was approximately 700 kg per 10a and it was 15% higher than that of Nakateshinsenbon (a common local variety). In addition, the yield was obviously enhanced by the successive application of rice straw and rice straw compost, especially straw compost gave higher yield. The yield of Akenohoshi ranged from 740 to 833 kg per 10a for four years, from 1984 to 1987. The effect of organic matter for Nakateshinsenbon was not so remarkable as Akenohoshi, which suggests that it is to one of the characteristics of Akenohoshi than by Nakateshinsenbon irrespective of organic matter application. The difference of nitrogen absorption between Akenohoshi than by Nakateshinsenbon irrespective of organic matter application. The difference of nitrogen absorption between Akenohoshi and Nakateshinsenbon was much enlarged in the plot with rice straw compost. Production efficiency for brown rice by the unit of absorbed nitrogen was distinctly higher in Akenohoshi. Seven hundred to eight hundred kilograms of grain yields were obtained at the number of forty to fifty thousands of spikelets per m^2, respectively. Percentage of ripened grains was 80 in this case. It is the standard number of spikelets in obtaining the targeted yield of Akenohoshi. It was pointed out that the yield of Akenohoshi was always higher compared with that of a local variety, Nakateshinsenbon, under direct sowing culture in well-drained field. Moreover, the effect of organic matter application on Akenohoshi was prominent.
