咸水膜下滴灌频率对土壤表层水盐环境的影响

为了更好地指导干旱区农业生产,利用地下咸水进行了膜下滴灌频率试验,设3种滴灌频率,即1次/24 h(T1)、1次/48 h(T2)和1次/72 h(T3),探讨了相同灌水量下不同滴灌频率对土壤表层水盐环境的影响。结果表明,(1)T2处理浅层土壤含水率高于T1和T3处理0.5%~1.0%,且试验后期形成面积和深度均大于T1和T3处理的;(2)土壤电导率在整个试验过程中呈增加趋势,T2处理土壤电导率增长幅度相对较小,土壤返盐程度较小;(3)土壤p H值在试验中期增大,试验后期减小,表层土壤p H值达8.5左右;(4)土壤表层各盐分离子量在试验期间的增加程度远小于土壤结冻期;土壤表层重碳酸根离子量在试验后期超过120.0 mg/kg,土壤总碱度增大,土壤存在碱化趋势。因此,滴灌频率1次/48 h可为作物提供比较适宜的土壤表层水盐环境,可作为民勤绿洲咸水滴灌频率参考值;同时,使用咸水滴灌后,绿洲土壤存在明显碱化趋势,因此还需采取其他灌排措施减弱土壤次生盐渍化。

The Impact of Frequency of Surface Drip Irrigation with Saline Water on Salt Accumulation on Mulched Soil Surface

How to use saline water for irrigation is an important issue in agriculture production in arid regions,and this paper investigated the effect of the frequency of drip irrigation with saline water on salt accumulation in the proximityof mulched soil surface.Three treatments were examined,irrigation after each 24 h (T1),after each 48 h (T2) and after each 72 h (T3).The results showed that:① The moisture content at soil surface in T2 was 0.5％～1.0％ higher than that under T1 and T3,and the area and depth of the wetting area in the soil under T2 was also larger than that under T1 and T3 at the late stage of the experiment;②Overall,the electrical conductivity (EC) in all treatments increased during the experiment,but the change of EC in T2 was slow compared with T1 and T3,indicating less salt accumulation;③ pH increased in the halfway of the experiment,and then decreased at the late stage with a value approximately 8.5.④The variation of the contents of salt ions during the experiment was low under frozen condition,and at the late stage of the experiment the content of HCO-3 was more than 120.0 mg/kg.The soil total alkalinity increased during the experiment.In summary,T2 appears to be the most appropriate method for irrigation using saline water in Minqin Oasis.However,care needs to be taken as our experiments revealed that irrigation using saline waters is likely to make soil alkaline.Thus,an appropriate irrigation and drainage combination is required to avoid secondary saline-alkalization in using saline water for irrigation.