微咸水入渗下施加PAM土壤水盐运移特性研究

土壤改良剂与微咸水灌溉相结合,对于合理开发利用微咸水、改善盐碱土结构及促进作物生长有着重要意义。基于一维垂直土柱积水入渗和水平土柱吸渗试验,研究了微咸水入渗条件下,不同聚丙烯酰胺(polyacrylamide,PAM)施量(0、0.02%、0.04%和0.06%)对盐碱土水盐运移特性的影响。结果表明:(1)微咸水入渗条件下,施加PAM能够降低土壤入渗速率,增加土壤保水性能。(2)施加PAM对Philip及Kostiakov入渗模型参数有显著影响,在PAM施量0.04%时,吸渗率S和经验系数K最小,而经验指数β最大。(3)在PAM施量为0.04%时,土壤饱和体积含水量最大,BrooksCorey模型进气吸力hd增加了15.30%,土壤持水性能显著提高;土壤水分扩散率最小,水分分布最均匀。(4)施加PAM能够显著提高土层的持水效率和微咸水的淋洗效果,在PAM施量为0.04%时,土层持水效率最高,盐分淋洗量最大。

Effects of PAM on Characteristics of Water and Salt Movement in Soil under Brackish Water Infiltration

It is of great significance to use soil amendment in combination with brackish water irrigation in rationalizing the exploitation of brackish water,improving saline soil structure and promoting crop growth. Polyacrylamide(PAM),a kind of organic polymer material,is regarded as an effective soil amendment because of its strong water holding capacity. In this paper,ponding infiltration experiments on one-dimension vertical soil columns and absorbing infiltration experiments on horizontal soil columns were carried out for investigation of effect of PAM application rate(0,0.02%,0.04% and 0.06%)on water and salt movement in soils with brackish water. Results show that(1)PAM reduced soil infiltration rate and enhanced soil water retention capability in the soil under brackish water infiltration,and the soil amended with 0.04% PAM was the highest in soil water retention capability;(2)PAM application significantly affected the parameters of the Philip and Kostiakov infiltration models and the soil amended with 0.04% PAM was the lowest in soil sorption rate S and empirical coefficient K,but the highest in empirical index β;in the Philip model soil permeability rate fell at first and then rose again with increasing PAM amendment rate;and the infiltration rate in the soil amended with 0.04% PAM was 0.547 cm min-0.5,which was the lowest;(3)In the soil amended with 0.04% PAM,the soil saturated volumetric water content reached the maximum;and the intake suction hd increased by 15.30% in the Brooks-Corey model,as compared with the control,which indicates that PAM can enhance soil water-holding capability significantly in soil under brackish water infiltration, minimize soil moisture diffusion rate and make water the most evenly distributed;and(4)PAM amendment significantly improved water-holding capability of the soil and salt leaching efficiency as well. The highest soil holding water capacity and the highest salt leaching rate t was found in the soil amended with 0.04% PAM.