灌溉水盐分组成对土壤水盐迁移参数的影响

Effect of salt ion composition of irrigation water on parameters of soil water and salt movement

淡水资源不足和盐渍化是干旱地区农业生产的限制因子。研究水盐迁移参数是水盐调控的重要目标。为此,该研究以甘肃省秦安县兴国镇果园土样为研究对象,采用水平土柱入渗法,探讨不同盐溶液(氯化钠、氯化钠和氯化镁、氯化钠和氯化钙、氯化钠和氯化钾)在矿化度均为3 g/L的条件下对土壤水分扩散率和盐分离子水平迁移的影响。结果表明:不同盐分组成的灌溉水质和含水率对土壤水分扩散率的影响均达极显著水平(P<0.01)。在灌溉水矿化度均为3 g/L的条件下,氯化钠盐溶液传输水分的潜在能力最大,加入一定的复盐对水分的传导起到阻滞作用,阻滞能力的大小是:氯化钙>氯化钾>氯化镁。不同盐分组成的灌溉水对土壤碳酸氢根和硫酸根的水平迁移具有显著的影响(P<0.05),对盐分、钙离子和钠离子水平迁移具有极显著的影响(P<0.01)。入渗距离对土壤pH的影响以及灌溉水盐分组成对土壤钠吸附比的影响均达显著水平(P<0.05)。灌溉水盐分组成对模型参数初始值和终止值有显著的影响,参数初始值和终止值均呈现:氯化钠>氯化钠和氯化镁>氯化钠和氯化钾>氯化钠和氯化钙。因此,从微咸水利用和盐渍化土壤改良的角度考虑,在微咸水灌溉中加入一定量的钙制剂可抑制水分扩散和降低土壤盐分含量;从灌溉方法来看,需从地块的两端轮换灌溉可预防地块一端脱盐而另一端积盐的现象。这一研究结果对于指导干旱、半干旱地区微咸水利用具有重要的科学意义。

Shortage of freshwater resources restricts agricultural production in arid and semiarid region.Irrigation with saline water provides an effective way to make up for the deficiency of freshwater resources.However,it is unknown about influence of irrigation with different salt ion compositions on soil physical and chemical properties.In this study,the effect of different salt ion compositions of irrigation on soil water and salt movement was investigated.The soil samples were collected from orchard calcareous soil in Qin’an County of Gansu Province.The soil electrical conductivity was0.43mS/cm,pH was8.54and soil organic matter was10.52g/kg.A total of4treatments were included:NaCl,NaCl:MgCl2with the ratio of1∶1,NaCl:CaCl2with the ratio of1∶1,NaCl:KCl with the ratio of1∶1.The concentration of all the treatments was3g/L.Soil water diffusivity and salt ions movement along the horizontal distance were studied by the method of horizontal soil column infiltration.Soil pH and sodium adsorption ratio were determined.The Boltzmann function was used for simulation of soil salt movement.The relationship between soil water diffusivity and water content was simulated by an power function.The results showed that the soil water diffusivity capacity at water content of0was the highest in the treatment of NaCl,followed by NaCl:MgCl2,NaCl:KCl and NaCl:CaCl2.The change rate of diffusivity with water content was the highest in the treatment of NaCl:CaCl2followed by the NaCl:KCl,NaCl:MgCl2and NaCl only.The salt ion composition of irrigation water and soil water content both significantly affected the soil water diffusivity(P<0.01).For all the treatments,the soil salt content,calcium ions,potassium ions,sulfate ions and sodium ions all increased with the infiltration distance but the bicarbonate ion decreased with the distance.The obvious trend wasn’t found for the chloride and magnesium ions.Soil pH decreased with infiltration distance for the treatment of NaCl only.The decrease trend of soil pH fluctuated for the other treatments.The soil pH at distance of8and32cm was significantly different(P<0.05).The salt ion composition did not significantly affect the soil pH.The sodium adsorption ratio decreased obviously with the infiltration distance in the treatment of NaCl only.The sodium adsorption ratio in the treatment of NaCl was higher than the other treatments.The sodium adsorption ratio increase trend fluctuated for the other treatments.The salt ion composition of irrigation water significantly affected the sodium adsorption ratio(P<0.05).Based on the Boltzmann function fitness,the initialization value and final value were influenced by the salt ion composition of irrigation water and the treatment NaCl was higher than the other treatments.The center was similar for all the treatments(28.488-28.700).The simulation was well with the determination coefficient higher than0.89.The study indicated that adding calcium ions in irrigation water could inhibit water movement and decrease salt accumulation in the process of irrigation with brackish water.The irrigation at one end of plot was not recommended since it may cause salt accumulation and we suggested to irrigate at both ends of the plot.The study could guide the irrigation with brackish water in arid or semiarid regions.