合鴨水稲作水田の窒素収支

概要

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In spite of the non-fertilizer application, many farmers have maintained stable rice production with aigamo-paddy cultivation. But, there is no scientific research supporting it. In the present study, a nitrogen balance sheet was prepared to evaluate the capacity of aigamo-paddy cultivation. Input factors, such as rainfall, irrigation water, biological nitrogen fixation in the bulk soil, and excretions from aigamo (a hybrid of duck and wild-duck), and output factors, such as grains, shoots and roots of rice crops, were determined in 2000 and 2001 at an aigamo-paddy field located at Keisen, Fukuoka Prefecture which had been cultivated since 1988. The nitrogen balance was negative, meaning that the output was higher than input, in both years. This indicates that the soil nitrogen should be depleted by repeated rice cropping. However, the soil nitrogen content increased during rice growing, contrary to the result predicted from the nitrogen balance. Factors responsible for the soil nitrogen increase were not completely identified. Judging from the nitrogen balance, continuous rice cultivation in the aigamo-paddy field is not sustainable without intermittent addition of organic residues or leaving the field fallow at fixed intervals.
社団法人日本土壌肥料学会の論文
2003-02-05