Controlling phosphorous (P) loads from rice fields is important for the conservation of aquatic ecosystems, in part because P is relatively concentrated at its sources. Recently, winter flooding, by which irrigation water is maintained in rice fields during winter, has attracted much attention as a farming strategy for environmental conservation and biodiversity maintenance. However, the effects of winter flooding on nutrient cycles have received little research attention. We evaluated the effects of winter flooding on P loads in rice fields by performing laboratory experiments with soils from rice fields with/without winter flooding. These incubation experiments showed that total and soluble reactive P concentrations in surface solutions are decreased by winter flooding. This decrease may follow co-precipitation of P with iron, which may be dissolved from winter flooded soil and rapidly precipitates in solution. Periphyton, which may increase during winter flooding, may not contribute to this decrease because puddling resets periphyton quantities on surface soils. P loads from rice fields with winter flooding over 16 days after fertilization could be reduced by an average of 26% compared with those without winter flooding, indicating that winter flooding is a valuable strategy for reducing P loads in spring when high P loads occur.

中文翻译：

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冬季洪水对稻田磷动态的影响

控制稻田中的磷负荷对保护水生生态系统很重要，部分原因是磷相对集中在其来源。近来，作为冬季保护环境和维持生物多样性的一种农业策略，冬季洪水在稻田中保持灌溉水受到了广泛的关注。但是，冬季洪水对养分循环的影响很少受到研究关注。我们通过对有/无冬季洪水的稻田土壤进行实验室实验，评估了冬季洪水对稻田磷负荷的影响。这些温育实验表明，冬季洪水会降低表面溶液中总的和可溶性的反应性P浓度。减少可能是由于P与铁共沉淀，可能从冬季被淹没的土壤中溶解并在溶液中迅速沉淀。在冬季洪水期间可能会增加的附生植物，可能不会造成这种减少，因为水坑使表层土壤的附生植物数量复位。施肥后16天有冬季洪水的稻田的磷负荷比没有冬季洪水的稻田平均降低了26％，这表明冬季灌溉是降低春季高磷负荷时P负荷的重要策略。