Self-sustaining nitrogen supply system in long-term unfertilized paddy-field

化肥和有机肥是作物可持续生产的关键。然而，日本的一些稻田农民成功地实现了30多年不施肥的高产。为了阐明这一机制，比较了东北地区6个稻田的氮平衡，营养生长期的分蘖活动是调节稻田氮平衡的关键因素。高产稻田由于土壤分解活性强，对矿化氮的供应能力强于低产田。

Fertilization including both chemical and organic forms is essential for sustainable crop production. However, several paddy field farmers in Japan successfully attain high yield without any fertilization for more than 30 years. To clarify this mechanism, six paddy rice fields in Tohoku region were compared in terms of nitrogen balance.Tillering activity during vegetative growth stage was a key component in regulating rice field. High-yield paddy fields had higher ability to supply mineralized nitrogen resulting from high soil decomposing activity than low-yield fields.