排水循环灌溉驱动的稻田水磷迁移与调控机制

Cyclic irrigation of drainage water is considered an effective water management practice for supplemental irrigation and reducing phosphorus loss. Little is known about water and phosphorus losses and use efficiency under cyclic irrigation of drainage water and as influenced by fertilization in paddy fields that much phosphorus losses from because of frequent irrigation and drainage. So the study should be conducted to determine the pathways of water and phosphorus transfer, and the effect of fertilization and cyclic irrigation ratio on phosphorus purification. Based on the field experiment and the balance of water and phosphorus, we are going to discuss the impacts of cyclic irrigation of drainage water on crop yields and phosphorus losses; the mechanism of water saving and controlling phosphorus losses and the pathways of water and phosphorus transfer under cyclic irrigation of drainage water; and the effect of fertilization and cyclic irrigation ratio on phosphorus purification under cyclic irrigation of drainage water. This research results will help improve understand water and phosphorus cycling in field scale, mitigate nonpoint source pollution, and select the proper irrigation schedule and fertilizer application level for cyclic irrigation of drainage water.

排水循环灌溉具有减少农田磷素流失和补充灌溉的潜力；然而在大量土壤磷素随频繁灌溉排水流失的水稻生长区，缺少排水循环灌溉对稻田水磷流失和作物生长影响的系统研究，尤其罕见考虑排水循环灌溉增加磷素输入量的稻田优化施肥研究。本项目拟紧密围绕排水循环灌溉驱动下稻田水磷输移机制和提高稻田磷净化效率的水肥调控机制两个关键科学问题，采用田间观测试验和质量平衡理论分析相结合的方法，探讨排水循环灌溉对稻田作物生长和不同形态磷素流失的影响，揭示排水循环灌溉驱动的节水减污机制和量化田间尺度的水磷迁移途径，提出改善稻田磷素净化效率的水肥调控机制。预期研究成果对认知田间尺度水磷运移与转化规律，减少稻田磷素流失造成的农业面源污染，制定科学合理的排水循环灌溉制度与施肥水平等具有重要的学术价值和实际意义。

农业旱涝灾害与面源污染严重影响我国粮食作物生产和地表水环境质量。排水循环灌溉具有补充灌溉和减少农田排水磷流失面源污染的潜力，然而在大量土壤磷素随频繁灌溉排水流失的水稻生长区罕见相关研究。采用田间观测试验、模型模拟和理论分析相结合的方法，本研究探明了排水循环灌溉对作物生长和水磷流失的影响，量化了排水循环灌溉的稻田水磷输移途径，提出了增强稻田磷净化的排水循环灌溉调控方式。.基于田间试验研究发现，在水稻种植区实施排水循环灌溉不会降低作物产量或增加再排水中不同形态磷素含量。排水循环灌溉引入稻田的磷素主要被土壤吸附到表层土壤中，表现为稻田表土Olsen-P含量随排水循环灌溉水中磷含量的增加而增加，并随距进水口距离的增加而减少，引入的磷素对水稻作物吸磷量的影响不明显。.模型研究方面，改进了SCS模型，构建了排水循环灌溉驱动的水循环模型，量化了单因子和多因子影响的水输移过程及其节水减排效应。排水循环灌溉的节水减排效应受灌排面积比RID、塘堰容积率PV、初始蓄水率PSi及塘堰容积PS的影响。补充灌溉率主要受RID、PV和PSi的影响，三者间存在交互效应且平均贡献比例近似4:3:1。补灌率随着PV和PSi的增加而提高，随着RID的增加而减小。减排率主要受PV、RID和PSi的影响，前两者的平均贡献占比分别为70%和10%，增加PV和RID可提高减排率，降低PSi亦提高减排率。基于潜在初损和有效降雨影响系数形成日有效雨量的递推关系，将前期产流条件概化成前期日降雨量对降雨初损的影响函数后改进的SCS模型显著提高了径流预测精度。.排水循环灌溉创造了适宜于循环水磷被土壤吸附或作物吸收的有利条件以强化稻田的磷净化效应。改变参数PV、RID和PSi的取值不同程度地减少了排水量与磷素流失量且增加了水磷的再利用量。在8月水稻需肥高峰期进行排水循环灌溉或延长灌溉水流程，明显改善排水循环灌溉下稻田的磷素去除效率。