农田水位调控下水稻旱涝交替胁迫机理、稻田氮磷流失规律及节水控污灌排模式

This research will take water level as a controlled index to characterize the alternate drought-waterlogging stress on rice in paddy fields. Experiments about the alternate drought-waterlogging stress at different rice growth stage (tillering, jointing and booting, heading and flowering, and milky stage) will be conducted on the lysimeters, soil columns and field plots, to measure rice growing index and nitrogen and phosphorus concentration of water in paddy fields. Through combining the field observation, theoretic analysis, and mathematical calculation, the research aims to study mechanism of alternate droughts and floods stress on rice under various designed field water level, to find out the field water level threshold where alternate droughts and floods have stress on rice growth during different stages, to establish a rice product-water level interaction model, and finally to validate the model. Based on variations of nitrogen and phosphorus concentration in field surface water and underground water during irrigation and after raining, we are planning to predict nitrogen and phosphorus loss amount in paddy fields, and to establish simulation model for nitrogen and phosphorus loss. In order to fulfill the targets of water-saving, drainage-reducing, pollution controlling and high product, we will optimize the field water level index of water-saving irrigation and drainage-control in different rice growing stages based on the rice product-water level interaction model. Furthermore, irrigation and drainage mode for water-saving and pollution control in paddy fields will be developed. This research will provide scientific foundation for optimizing irrigation-drainage management and the construction of ecological irrigation district with water-saving and pollution control in paddy field areas of south China.

以农田水位作为水稻旱涝交替胁迫调控指标，在蒸渗测坑、土柱和田间小区内分别进行水稻4个生育阶段（分蘖期、拔节孕穗期、抽穗开花期、乳熟期）的农田水位调控下旱涝交替胁迫试验，观测水稻生长发育指标和稻田水氮磷浓度变化情况。通过试验观测、理论分析、数值计算相结合的方法，研究农田水位调控下水稻旱涝交替胁迫机理，提出水稻各生育阶段旱涝交替胁迫的农田水位阈值，构建水稻产量-水位响应模型，并验证模型的合理性；根据灌溉和雨后农田水位调控下稻田地表水、地下水氮磷浓度变化规律，预测稻田氮磷流失量，构建稻田氮磷流失量模拟模型；依据水稻产量-水位响应模型、稻田氮磷流失量模拟模型，以节水、减排、控污、高产为目标，优化水稻各生育阶段节水灌溉和控制排水的农田水位适宜指标，提出水稻节水、控污灌排模式，为优化南方稻作区灌溉排水管理策略、建设节水、控污型生态灌区提供科学依据。

水稻控制灌排技术作为南方稻作区的核心灌排技术，综合考虑了节水灌溉与控制排水的协同效应，对实现南方稻作区的节水、减排、控污、高产具有重要意义。以农田水位作为灌排的调控指标，采用测坑试验、数据分析和数值模拟相结合的研究手段，探求了控制灌排条件下旱涝交替胁迫水稻生理生长响应机理，构建了水稻水位生产函数，模拟了控制灌排水稻生长，分析了农田水位调控下稻田地表水、地下水氮磷浓度变化规律及其机理，提出了节水高产减排控污的水稻控制灌排模式。主要研究内容和结论如下：分蘖期单个生育期、分蘖期与拔节孕穗期连续两个生育期旱涝交替胁迫使水稻产量分别显著（P<0.05）降低，其它单个生育期和连续两个生育期影响不显著（P≥0.05）；分蘖期旱涝交替胁迫对后期水稻光合作用产生超补偿效应，但抑制了后期水稻蒸腾作用，拔节孕穗期先旱后涝胁迫对后期水稻光合作用和蒸腾作用产生超补偿效应，抽穗开花期和乳熟期旱涝交替胁迫均抑制了后期水稻光合作用和蒸腾作用；考虑控制灌排对稻田土壤温度的影响，基于建立的土壤温度模型对CERES-Rice模型进行了改进，改进模型能够较为准确地模拟控制灌排水稻生长；当水分胁迫由旱转涝时，淹水初期稻田水中铵态氮（NH4+-N）、硝态氮（NO3--N）和总磷（TP）浓度显著增加，这个时期地表和地下排水应该引起注意；轻旱控制灌排技术并不导致水稻减产，且稻田灌溉定额能够降低11.89%(P<0.05)，同时由于排水峰值和排水次数明显减少，总磷、铵态氮、硝态氮稻田表面径流流失负荷分别降低54.58%、36.29%和60.10% (P<0.05)，但在雨量较多的年份会增加渗漏量，从而造成总磷、铵态氮淋失负荷升高；应用基于序关系分析法和熵值法组合权重的TOPSIS理想解法对水稻灌排方案进行优选决策，结果表明轻旱控制灌排在保证粮食生产量的前提下具有良好的节水减排控污效果。