秸秆排水体埋深对盐渍土水盐分布的影响及排水抑盐效果

为探究秸秆排水体对盐渍土水盐运移的影响及其排水排盐效果,通过室内土柱试验,研究在淡水(CK)和微咸水灌水情况下秸秆排水体埋深为40和60 cm时供试土壤的水盐分布状况。结果表明,入渗阶段,湿润锋与入渗时间呈幂函数关系,累积入渗量与入渗时间则可采用Kostiakov模型进行拟合;蒸发阶段,秸秆排水体对埋设深度以下的土体具有明显的保水作用,40 cm埋深的处理在40~70 cm土层范围以及60 cm埋深的处理在50~70 cm土层范围土壤水分变化的相对变化量均0;秸秆排水体有利于保持灌水后土壤的脱盐状态,40 cm埋深处理和60 cm埋深处理比无埋设的对照处理分别减少了19.61%和15.68%的盐分变化量;秸秆体的排水排盐效果与灌水矿化度和秸秆排水体埋深密切相关,灌溉水矿化度适当的增加和秸秆体的埋设加深将有利于排水效果的提升,低灌溉水矿化度结合秸秆体深埋具有更好的排盐效果。该研究为微咸水灌溉及盐渍土的开发利用提供依据和参考。

Effect of straw draining piece depth in soil on water-salt distribution in saline soil and its drainage-salt inhibiting performance

Abstract: To explore the drainage performance of straw draining piece and the soil water-salt movement in saline soil, a soil column experiment was established at an indoor laboratory in Hohai University. The soil water salt distribution under the irrigation condition of different salinity of brackish water with the straw draining pieces buried in 40 and 60 cm depth in the soil was investigated. A cylinder drainage body of 40 cm in height and 15 cm in diameter was made using rice straws, enveloped in 5 cm thick non-woven fabric and bound into shape using a plastic cord. The irrigation water was available in 3 gradients by design (0, 3 and 5 g/L) for better simulating a saline soil irrigation area. Irrigation amount of each treatment was 35 L to simulate the waterlogging soil condition. The soil column simulated a soil having an initial salinity of 5 g/kg. The groundwater depth was maintained at 80 cm by connecting to an external Mariotte''s bottle and the groundwater salt content was set at 5 g/L. The test was conducted to determine, in the irrigation process, the wetting front distance and cumulative infiltration. Soil salinity and moisture (by mass) in different soil layers at 1 and 25 d after irrigation were determined. Relative change of soil moisture variation after 25 d of irrigation was calculated to reveal the ability of inhibiting soil evaporation or leakage of straw piece. In the drainage process, the drainage, salt removal, drainage efficiency and salt removal efficiency were then estimated from these measurements. The results showed that the infiltration duration and the wetting front distance conformed to a power function, the infiltration rates of soils with straw draining piece could be simply fitted by Kostiakov equation. Straw piece had the ability to inhibit soil moisture variation and groundwater reverse osmosis effect, the relative change of soil moisture variation in the soil with the straw piece was above 0 both in the treatment with 40 or 60 cm burial depth. Straw piece also helped keep the desalination state after irrigation and reduce the salt accumulation, and the treatments with 40 cm and 60 cm burial depth could reduce the salinity variation by 19.61% and 15.68%, respectively, compared to the treatments of CK. When the brackish water was used to irrigate, the salinity of irrigation water and the depth of straw piece buried both had impact on the effect of drainage and desalination. Increasing the salinity of irrigation water or burying straw pieces deeper could improve the performance of drainage, decreasing the salinity of water combined with straw piece deeper buried body could show better desalting effect. The research provides a new way of straw utilization in field and also a reliable technique for the development and utilization of brackish water irrigation and saline soil.