潜水蒸发条件下不同棉秆隔层埋深对土壤盐分时空分布的影响

Using Cotton Straw Interlayer to Reduce Evaporation and Salt Migration From Groundwater to the Soil Surface

【目的】探寻适宜的棉秆隔层埋深,以降低土壤盐分积累。【方法】以南疆膜下滴灌棉田盐渍化土壤为材料,采用室内土柱试验,开展不同地下水埋深(1.0、1.5 m和2.0 m)与棉秆隔层埋深(15、30、45 cm和60 cm)二因素随机区组试验研究,分析了土壤剖面盐分时空分布规律和积盐过程,通过方差分析和曲线回归明确了地下水埋深、棉秆隔层和潜水累计蒸发量对土壤盐分时空分布特征。【结果】①累计蒸发量和日均蒸发强度均随地下水埋深的增加而减小,1.0、1.5 m和2.0 m地下水埋深日均蒸发强度为1.73、1.12 mm/d和0.49 mm/d。棉秆隔层对土壤水分蒸发起到一定的抑制作用,以棉秆埋深15 cm阻减蒸发作用明显,而棉秆埋深30 cm累计蒸发量和蒸发强度均大于其他棉秆埋深。②潜水蒸发使盐分出现表聚,耕作层0~30 cm盐分表聚量随地下水埋深增加而降低,1.0、1.5 m和2.0 m地下水埋深耕作层0~30 cm日均积盐量分别为0.031、0.012 g/kg和0.004 g/kg。棉秆隔层阻盐作用主要表现在前期,土壤15 cm处设置棉秆隔层对耕作层0~30 cm阻盐效果最好,地下水1.0、1.5 m和2.0 m棉秆埋深15 cm日均积盐量分别是棉秆埋深30、45、60 cm的71.25%、87.15%和90.58%;41.91%、37.85%和34.90%;20.45%、26.63%和33.33%。③土壤积盐量随潜水累计蒸发量增加而增加。耕作层0~30 cm土壤积盐量与累计蒸发量关系可用线性关系描述。【结论】潜水累计蒸发量和蒸发强度随地下水埋深增加均减小;不同地下水埋深棉秆隔层设置在15 cm对耕作层0~30 cm阻盐效果最好;不同秸秆埋设深度均可降低盐分积累。

【Background and objective】Evaporation and its associated salt accumulation on the soil surface is an abiotic stress facing agricultural production in arid and semi-arid regions,and how to alleviate its detrimental impact is a topic that continues to attract interest from both researchers and practitioners.Cutting the capillary connection in soil is one technology and the purpose of this paper is to investigate the feasibility of burying a straw interlayer in soil to slow down evaporation and salt migration from groundwater.【Method】The experiments were conducted in columns filled with saline soil taken from a cotton field that has been watered by film-mulched drip irrigation in southern Xinjiang.The groundwater table was controlled at the depths of 1.0 m,1.5 m and 2.0 m respectively,with a cotton straw interlayer buried at a depth between 15 cm and 60 cm from the soil surface.In each treatment,we measured water evaporation and salt accumulation on the soil surface.【Result】①The cumulative evaporation and daily evaporation rate both decreased as the groundwater table depth increased,with the average daily evaporation rate being 1.73 mm/d,1.12 mm/d and 0.49 mm/d,respectively,when the groundwater table was 1.0 m,1.5 m and 2.0 m deep.The cotton straw layer reduced water evaporation with the reduction depending on its burying depth.The reduction was the highest when its buying depth was 15 cm,and the least when the burying depth was 30 cm.②Salt accumulation in 0~30 cm soil layer decreased as the groundwater depth increased,with daily accumulation rate being 0.031 g/kg/d,0.012 g/kg/d and 0.004 g/kg/d,respectively,when the groundwater table depth was 1.0 m,1.5 m and 2.0 m without the straw layer.The efficacy of the straw layer in reducing evaporation was more noticeable in the early stage of the experiment,and was most effective when being buried at the depth of 15cm.When groundwater table was 1 m,1.5 m and 2.0 m deep,burying the straw 15 cm deep reduced daily slat accumulation in the 0~30 cm of soil by 71.25%,87.15%and 90.58%;41.91%,37.85%and 34.90%;and 20.45%,26.63%and 33.33%,respectively,compared with that buying it at 30 cm,45 cm and 60 cm deep.③The accumulated salt in 0~30 cm soil increased linearly with soil water evaporation.【Conclusion】The accumulated salt on the soil surface and daily evaporation from groundwater both decreased as groundwater depth increased.Regardless of its burying depth,the cotton straw layer reduced groundwater evaporation and salt accumulation in 0~30 cm soil,but it was most effective when being buried at the depth of 15 cm.We also found that the accumulated salt in the 0~30 cm soil increased linearly with water evaporation.