滴灌流量对土壤水盐运移及再分布的作用规律研究

通过室内土箱模拟试验,对不同滴头流量处理的土壤水盐运移及再分布规律进行了研究,结果显示:两滴头交汇界面处的湿润锋依滴头流量不同而呈椭圆形或圆形;大滴头流量促进了水分的水平运动,水平扩散速率明显大于垂直入渗速率;随着滴头流量的减小,水平和垂直方向的入渗距离逐渐接近;土壤湿润体体积与总灌水量有关,而与滴头流量并无显著相关;根据湿润锋的运动,给出了试验用土大田建议滴头流量;滴灌结束后,水盐经历了一个非常重要的再分布过程,经过再分布,土壤水盐进一步向深层运移,促进了上层土壤的淡化,小滴头流量的淋盐效果明显好于大滴头流量;土壤盐分的运移在前3天的再分布中最为活跃;试验得出了保证作物生长需要和淋盐需要的每滴头灌溉水量,对实践具有一定的指导意义。

MOVEMENT AND REDISTRIBUTION OF WATER AND SALT IN RELATION TOEMITTER DISCHARGE RATE

A study on movement and redistribution of water and salt in soil in relation to emitter discharge rate was conducted through indoor simulation tests in soil columns.Results show that depending on emitter discharge rate,the wetted front at the meeting interface of waters from two emitters appeared to be either elliptical or circular.High emitter discharge rates accelerated horizontal movement of the water,resulting in greater horizontal dispersion rate than vertical infiltration rate.With decreased emitter discharge rate,the distance of horizontal infiltration approached to that of vertical infiltration.Wetted soil volume was related to total quantity of the irrigation water rather than emitter discharge rate.Based on the rules of wetted front movement,a proper emitter discharge rate was suggested for field practice.At the end of drip irrigation,water and salt had experienced important redistribution processes.The movement of water and salt to deeper soil layers promoted desalination of the upper soil layer. The effect was markedly better with low emitter discharge rates than high emitter discharge rates.The movement of salt was the most active onthe first three days of redistribution.A proper water volume per emitter that satisfies both the demand of a crop for growth and the need of the soil for salt leaching was worked out through the experiment,whichis sure of certain practical significance.