Patterns of Soil Nitrogen Release in Paddy Fields of Warm Regions in Japan and Diagnosis of Fertilizer Application : III. Evaluation of amount of soil nitrogen supplied from paddy fields in relation to rice yield

[摘要] It was investigated whether the amount of ammonification could be used as an index of soil analysis for fertilizer application, which was related with the amount of soil nitrogen supplied from paddy fields. The amount of ammonificaton was shown by the amount of ammonium nitrogen released by incubation of the air-dried soils at 30°C in 4 weeks. The amount of ammonification of the top soils in the Tikugo basin was compared with the amount of soil nitrogen absorbed by rice plants, which was estimated from the nitrogen accumulated in the rice plant grown with no nitrogen fertilizer. The amount of ammonification was expressed as kg per 10a by using the depth and the volume weight of topsoil. The amount of ammonification obtained by indoor experiment was found to be correlated with the amount of soil nitrogen absorbed by rice plants. The rate of the latter to the former was 42% in 'Nishihomare' and 40% in 'Hinohikari' on the average of the experimental fields, and there was little difference of between fine textured soils and coarse textured soils. Based on the above results, it was concluded that the amount of ammonification could be used to estimate the rice yeild and to determine the optimum rate of fertilizer application.

[学科分类] 农业科学（综合）

[关键词] Ammonification;アンモニア化成;Nitrogen uptake;水田土壌;Paddy soils;施肥量;Rate of Fertilizer application;窒素吸収量;Soil nitrogen;地力窒素