变温度-风速模拟条件下微润灌工况自适应调节机理

Mechanism of Self-adaptive Moistube Irrigation at Different Simulative Temperatures and Wind Speed Factors

通过模拟光照、吹风改变蒸发强度,对比分析了4种蒸发条件(CK、光照(L)、吹风(W)、光照+吹风(LW))下微润灌入渗速率以及湿润体变化特征。结果表明,常温下微润灌累积入渗量与时间呈显著线性相关关系(决定系数R2>0.99),符合Philip入渗模型水平吸渗项入渗规律;微润管出流速率因多孔介质管壁穿透入渗、管周土壤水分入渗分别随时间呈现出初期骤增、线性减小的演变规律;改变上边界条件后各处理蒸发均显著增大,然而入渗速率只随温度增加而提高,吹风带走土表热量,入渗速率反而减小;光照期间,L、LW处理入渗速率分别增长56.56%、29.51%;撤去光照2 h后,LW处理蒸发强度不变,入渗速率骤降5.90%,揭示了微润灌对温度响应的敏感性远高于上边界蒸发。湿润锋运移距离与时间呈显著幂函数关系,温度提高后入渗速率增加促进了湿润锋运移,温差和重力势共同驱动下水分向背离热源方向移动,光照处理中湿润锋水平运移距离D_(horiz)、垂直向下运移距离D_(down)较预测值分别增长75.81%、99.30%。该研究揭示了源于辐射的地温变化在微润灌入渗中的关键驱动效应,有效补充了微润灌在温差、辐射骤变区域的管出流及土壤水分动态运移机理,研究结果可为基于气象数据、作物需水和墒情的微润灌智慧调控模式设计提供理论依据。

The evaporation intensity was changed by simulating light and blowing wind.Comparing the characteristics of moistube irrigation infiltration rate and wetting body changes under four different evaporation conditions(CK,Light(L),Wind(W),Light+Wind(LW)),it was found that the cumulative infiltration of moistube irrigation at room temperature was significantly linearly correlated with time(coefficient of determination R2>0.99),which was consistent with the infiltration law of the horizontal absorption term of the Philip infiltration model.The infiltration rate of moistube outflow showed an initial sudden increase and then linear decrease with time due to the penetration of infiltration through the wall of porous medium and infiltration of soil water around the tube respectively.The evaporation of each treatment was increased significantly after changing the upper boundary conditions.However,the infiltration rate was increased only with the increase of temperature as the infiltration rate even decreased when the wind carried away the heat from the soil surface.During the light period,the infiltration rates of L and LW treatments were increased by 56.56%and 29.51%,respectively.After the withdrawal of light for 2 h,the evaporation intensity of LW treatment remained unchanged,and the infiltration rate plummeted by 5.90%,which revealed that the sensitivity of moistube irrigation to temperature response was much higher than that of evaporation at the upper boundary.The transport distance of wetting fronts showed a significant power function relationship with time and the increase of infiltration rate after the temperature increase promoted the transport of wetting fronts,which was driven by both temperature difference and gravitational potential in the direction of moving away from the heat source.Compared with the prediction,the horizontal migration distance D_(horiz) and vertical downward migration distance D_(down) in the light treatment were increased by 75.81%and 99.30%,respectively.The research result can provide theoretical basis for the design of smart regulation model of moistube irrigation based on meteorological data,crop water demand and moisture conditions.