To soils of pot, culture experiment, having top-dressed with manures and ammonium sulphate,the rate of liberation of ammonia during hydrolysis in different alkaline mediums was measured by distillation with MgO, CaO and 0.5 N NaOH, and by replacement of N NaOH solution ae room temperature (Conway's diffusion method). Soil samples were taken at intervals of 1,5,10,15,20 and 30 days after fertilization. Variations of nitrogen content in plant leaves at different stage of growth were also determined. Through mathematical analysis from the data involving rate and capacity of the liberation of ammonia in alkaline mediums, the writer endeavors to predict nitrogen supplying status of paddy soils through out the growing season of rice.Except soils recieved stable manures the amount of nitrogen from MgO distillation gives correlation with the V₀ initial rate of liberation of ammonia of N NaOH diffusion method and distillation methods. Figures obtained in MgO distillation are higher than the ammonical nitrogen in soils. The increment is induced by the partial hydrolysis of amides.