Nutrient physiology of rice cultivation by grass mulching without chemical fertilyzers.

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Further our experimental results for grass mulching on paddy fields without chemical fertilyzers have showed the same yields with ordinary caltivation with chemical fertilyzers. However, it was to be necessary more amount of man-power than ordinary one. We attempted to estabilish the new method of utilization of the principle of grass mulching, which supplied nutrients by the extracted solution from mulching grass submerged in irrigated water at paddy fields; dried grass was accumulated on one place in the corner of paddy field in order to decompose by submerged in warm water, after that, the extracted solution was given by mixing with irrigation water into the paddy field.Reed(Phragnited communis Trinius), bamboo grass(Pleiobastus variegatus Makino) and rye straw (Secale cereale L.) were used as materials of the extracted solution, giving to experimental plots. Rice yields were 501 g/ <m^2> with the reed's extracted solution and a plot of grass mulching of the reed yielded 362 g/ <m^2> . Comparing with those plots, chemical fertilyzers plot, giving the same amount of nitrogen to the reed's extracted solution plot, was 416 g/ <m^2> .Amount of extracted nutritional elements from each grass materials per 1 kg DW showed a range 9 - 17g of nitrogen, about 2g of phosphorous, 14 - 35g of potassium, about 3g of calcium and 7 - 16g silica, respectively, however, those amount could recovered only one third amount of total extracted nutrition due to absorption of soil and denitrification in the process.It was remarkable that the extracted solution from submerged grass seemed to be promoted absorption of silica by rice plants. It was clearly proved by the larger amount of absorption than the giving amount; the extracted solution might be released aviable silica contained in the soil.