基于染色示踪的膜下滴灌棉田水盐运移规律

Water Flow and Salt Transport in Cotton Field of Mulched Drip-Irrigation Using Dye Tracer

采用亮蓝FCF染色示踪剂,研究膜下滴灌条件的水盐运移规律;分别在灌溉前、灌溉中和灌溉后等不同时间段共开挖13个时刻的剖面,观察膜下滴灌湿润面的运移情况;以10cm间隔的网格,用MP406土壤水分探测器原位测定3120个点的土壤体积含水率,同时取1430份土样,利用1:5土水比浸提法测定土壤盐分;并利用WATCHDOG气象站监测研究区气象要素.结果表明:染色示踪能直观表征土壤水盐运动轨迹;膜下滴灌条件下,垂直滴灌带方向土壤水流呈点源入渗特征、沿滴灌带方向近似呈线源入渗特征;现行灌溉模式下,壤质砂土湿润锋横向运移速率约为8cm/h;滴灌对滴头附近土体有一定洗盐效果,未覆膜区域地表土体出现盐分积累;灌水时间越长,湿润锋越深,横向扩展速率接近无作物小区(8cm/h);从土壤水合理利用角度考虑,满足研究区一膜一带四行的种植模式和土质的单次合理灌水量应为29.4～69.8mm.

Brilliant Blue FCF was used to trace water flow in cotton field of mulched drip-irrigation using brackish water.13 cross sections were dug before irrigation,during irrigation and after irrigation,respectively,for observation of the movement of wetting front.The soil moistures were in-situ measured at 3 120 points by using MP406 moisture probe and 1 430 soil samples were sampled to analyze soil salinity by extracting soil water with 1:5 of soil to water,while cross sections were divided as each grid 10 cm×10 cm.The meteorology data were measured by WATCHDOG.The results show that the dye tracer can trace soil water flow and salinity transport obviously.There are two infiltrating states for soil water and salinity transport characters in field under film mulched drip-irrigation:point source infiltrating in the direction vertical to drip irrigation pipe and approximate line source infiltrating along with drip irrigation pipe.The velocity of soil wetting front movement was 8cm/h under the present irrigation.The soil salinity near the dripper was leached by irrigation water;however,the salt accumulated in the surface soil without film mulch.The wetting front extended with the irrigation time,and the spreading distance was similar to that with no plants.For efficient use of soil water,the reasonable irrigation quota for the present planting pattern of one film,one irrigation pipe and four row cottons was 29.4-69.8 mm in the study area.