灌溉排水耦合调控稻田水分转化关系

该文利用装配有地下水位自动控制系统的蒸渗仪,分析节水灌溉与旱地控制排水技术耦合调控对于稻田水分转化关系的影响。结果表明,灌排耦合调控在小幅减少水稻产量的同时,显著减少了稻田灌溉水量、地下排水量及水稻蒸发蒸腾量,最终显著增加了水稻水分生产效率。与常规灌排稻田相比,灌排耦合调控稻田水稻产量减少1.9%,灌溉水量、地下排水量及水稻蒸发蒸腾量分别显著减少41.7%、49.9%及24.9%,水分生产效率增加30.5%。随着控灌稻田排水控制限的提高,稻田灌溉水量、地下排水量及水稻蒸发蒸腾量减少,水稻产量保持稳定,使得水稻水分生产效率进一步增加。提高控灌稻田的排水控制限,减缓了稻田土壤水分的衰退速度,并增加稻田地下水位低于排水控制限的比例,稻田灌溉次数与发生地下排水的时段均减少,使得控灌稻田灌溉水量与地下排水量下降,两者综合作用下控灌稻田水稻蒸发蒸腾量减少。在采用控制灌溉模式的基础上,适当提高稻田排水控制限,可以较好地实现水稻生产中水分的高效利用,研究结果可为优化稻田水管理模式提供依据。

Regulation and control of water transformation through coupling irrigation and drainage in paddy field

The effect of controlled irrigation and drainage on water transformation for paddy field was investigated by controlling root zone soil water content and water table depth using a lysimeter equipped with an automatic water table control system. Four treatments that combined irrigation and drainage managements were implemented: controlled irrigation (CI) + controlled water table depth 1 (CWT1), CI + controlled water table depth 2 (CWT2), CI + controlled water table depth 3 (CWT3) and flooding irrigation (FI) + CWT1. Experiments were conducted in 12 drainage type plots with a mobile shelter and gallery. Each plot had a size of 2.5 m × 2 m and a depth of 1.3 m. Each plot was individually irrigated and drained using a pipe installed with a water meter and a tube installed at 1.2 m below the soil surface, respectively. Subsurface drainage was conducted based on the water table control by using an automatic water table control system, which was installed on each drain tube in the gallery. The soil moisture was measured daily by a Trease system (6050X3) when no pond water remained in the paddy field. The pond water depths in the paddy field were measured daily using a vertical ruler. A water table observation well was installed in the field outside the plot. The actual field water table depths were measured daily after the re-greening stage. One water table observation tube was mounted on the drain tube in each plot. The water table depths of each plot were measured daily after the re-greening stage using a vertical ruler. A water meter installed on the pipe of each plot recorded the irrigation volumes. The water leakage volumes were measured using a tipping bucket gauge. The results showed that irrigation water, subsurface drainage water, and evapotranspiration in paddy field reduced significantly under controlled irrigation and drainage, 41.7%, 49.9% and 24.9% lower than those under conventional irrigation and drainage management, respectively, and meanwhile, rice yield reduced slightly. Therefore, water production efficiency increased significantly under controlled irrigation and drainage. Rice yield and water production efficiency under controlled irrigation and drainage were 1.9% lower and 35.5% higher than those under conventional irrigation and drainage management, respectively. Increases in water table control levels resulted in less irrigation water, subsurface drainage water and evapotranspiration and steady rice yield for paddy field under controlled irrigation. Therefore, water production efficiency under controlled irrigation increased with the increase in water table control levels. The increases in water table control levels reduced irrigation water by lengthening the duration of soil moisture depleted to the lower threshold for irrigation. The proportion of water table levels lower than the control levels increased as the increase in water table control levels, which shortened the duration of subsurface drainage and reduced subsurface drainage water. The effect of irrigation water on evapotranspiration was higher than that of subsurface drainage water. Therefore, the reduction in irrigation water accompanied by the increase in water table control levels reduced evapotranspiration in paddy field. The application of increasing water table control level to a suitable level in paddy field under controlled irrigation can effectively realize high water use efficiency.