考虑地面灌水技术制约的灌溉制度优化

制定作物灌溉制度不仅要考虑补充根层土壤水分以满足作物需求，还应考虑灌水方法对灌水量的限制。为研究我国华北地区地面灌溉条件下冬小麦－夏玉米连作的节水灌溉制度，在河北省雄县进行了连续3年不同灌水处理试验，用水量平衡模型ISAREG对各处理进行数值模拟，从而验证了选定的模型和参数。采用该模型模拟了不同水文年冬小麦－夏玉米连作的多种灌溉制度，对各方案的灌水次数、灌水量、降雨和灌溉水量损失以及作物产量等因素进行了对比，并对现行灌溉制度进行了评价。结果显示：雄县现行灌溉定额大大超过了灌溉需水量，主要原因是地面灌水技术的制约，如田面不平、进地流量过小或畦块过大等，造成难以控制小水量灌溉。为研究既能满足作物基本需水要求，又使灌溉水量损失最小的最佳灌水定额，用模拟地面灌溉水流运动的SRFR模型模拟不同生长阶段的灌溉，得到了每次灌溉时不同流量条件下的最小灌水量，以及灌水效率与灌水量的关系，据此提出了与灌水技术改进措施相结合的不同水文年的灌溉制度优化方案。

Optimization of irrigation scheduling considering constraints of surface irrigation technology

Irrigation scheduling should be determined by considering both the crop requirements and the constraints of the irrigation method. In order to research the irrigation scheduling that is appropriate for wheat-maize crop sequence in the North China Plain, different treatments of irrigation experiments were performed in three consecutive years in Xiongxian, Hebei Province. All treatments of the experiments were simulated by the soil water balance model ISAREG. The simulation results showed that the parameters were calibrated and the model was validated well. Several alternative irrigation strategies were simulated with the model for the years corresponding to different probabilities of irrigation requirements. The irrigation times, application depths, water losses both from irrigation and rainfall, and crop yields were compared. The current irrigation scheduling was evaluated. The comparison results show that the current application volumes largely exceed the irrigation requirements. Main reasons were the constraints of the surface irrigation technology, such as uneven basin surface, relative small inflow rate and large basin sizes, which caused difficulty to control the irrigation in a small water volume. In order to get the appropriate application depth for each irrigation that can not only meet the basic crop water requirement, but also lead to minimum water losses, the surface irrigation model SRFR was used to simulate the irrigationships in different crop growing periods. From the simulations, the minimum net irrigation depth and the relationships between the application efficiency and the low-quarter infiltration depth were obtained for each irrigation and different inflow rates. Based on above results, the improved irrigation schedulings for average, dry and severe dry years were proposed by combining improvement of irrigation methods.