微咸水滴灌条件下沙穴种植的土壤水盐二维空间分布规律

河套灌区重度盐碱土具有结构性差、导水率低的特点,且该地区淡水资源短缺,为提高土壤水入渗性能,合理开发利用微咸水资源,可在滴头下方设置沙穴并利用微咸水灌溉。为探明不同矿化度微咸水滴灌的沙穴种植条件下二维土壤水盐分布规律,采用室内50 cm×50 cm二维土槽模拟试验,设置蒸馏水(0 g/L),2.0,3.0,4.0 g/L 4种不同矿化度处理,试验历时100 h。结果表明:在深度5 cm距滴头两侧15~20 cm及滴头下方25 cm的盐碱土处,土壤含水量较高,沙土土壤含水率随着矿化度的增加而增加,盐碱土土壤含水率随着矿化度的增加呈现先增加后降低的趋势,采用3.0 g/L灌溉水滴灌时,盐碱土含水率最大(变异系数为7.64%),说明利用3.0 g/L微咸水灌溉可有效提高沙穴种植条件下土壤含水率;入渗100 h后盐分主要聚集在滴头下方25~30 cm处,沙穴结构试验中,灌溉水矿化度为4.0 g/L的情况下土壤平均电导率最大(变异系数为50.59%),水平方向盐分淋洗效果优于垂直方向,且灌溉水矿化度越低,淋洗效果越显著,蒸馏水处理脱盐率为13.99%,灌溉水矿化度为2.0,3.0,4.0 g/L时积盐率分别为7.93%,14.57%,30.05%,脱盐半径随矿化度的增大而减小,3.0 g/L与2.0 g/L积盐量差异不显著(P=0.460>0.05),与4.0 g/L处理下积盐量差异显著(P=0.024<0.05)。结合土壤水盐空间分布规律,利用3.0 g/L微咸水可提高盐碱土土壤含水率,控制沙穴种植结构土壤积盐量,提高根系层土壤保水性。

Spatial Distribution of Soil Water and Salt Under Sand Hole Planting with Drip Irrigation of Brackish Water

The heavy saline alkali soil in Hetao irrigation area has the characteristics of poor structure and low water conductivity, and the fresh water resources in this area are in short supply. In order to improve the infiltration performance of soil water and reasonably develop and utilize the brackish water resources, a sand hole can be set under the dripper and the brackish water can be used for irrigation. In order to find out the influence of different salinity and brackish water drip irrigation on the distribution of water and salt in soil under the sand hole planting, this study adopted the indoor simulation test of 50 cm×50 cm two-dimensional soil tank, and set four different salinity treatments of distilled water (0 g/L), 2.0, 3.0 and 4.0 g/L, the experimental duration was 100 hours. The results showed that the soil water content was higher in the saline alkali soil with the depth of 5 cm and at the distance of 15~20 cm from both sides of the dripper and 25 cm below the dripper. The soil water content of the sandy soil increased with the increase of water salinity. The soil water content of the saline alkali soil increased first and then decreased with the increase of the salinity. When using 3.0 g/L water drip irrigation, the water content of the saline alkali soil was the largest (coefficient of variation was 7.64%). Therefore, using 3.0 g/L water irrigation could effectively improve the soil moisture content under sand hole planting; after 100 hours of infiltration, the salt was mainly concentrated at 25~30 cm below the dripper. In the sand hole structure test, when the salinity of irrigation water was 4.0 g/L, the average conductivity of soil was the largest (coefficient of variation was 50.59%). The effect of salt leaching in horizontal direction was better than that in vertical direction, and the lower salinity of irrigation water gave the more significant leaching effect.The desalination rate of distilled water treatment was 13.99%, and the salt accumulation rates were 7.93%, 14.57% and 30.05% for irrigation the salinity of 2.0, 3.0 and 4.0 g/L, respectively. The desalination radius decreased with the increase of the salinity, and the difference between the salt accumulation of 3.0 g/L and 2.0 g/L was not significant (P=0.460 > 0.05), which two were significantly different from that of 4.0 g/L (P=0.024 < 0.05). Combined with the spatial distribution law of soil water and salt, 3.0 g/L brackish water could be used to improve the soil water content of saline alkali soil, control the salt accumulation in sand holes, and improve the soil water conservation of root layer.