具有秸秆夹层层状土壤一维垂直入渗水盐分布特征

Distribution Characteristics of One-dimensional Vertical Infiltration Water and Salt in Layered Soil with Subsurface Straw Layer

为了解具有秸秆夹层层状土壤一维垂直入渗水盐分布特征,通过定水头入渗实验装置,在距土表以下20 cm设置一个秸秆夹层,研究了4种秸秆铺设量(0、6 000、12 000、18 000 kg/hm2)和2种秸秆长度(1、10 cm)的秸秆夹层对盐碱土入渗过程土壤水分和盐分分布的影响。结果表明,盐碱土中设置秸秆夹层具有良好的阻水性,累积入渗量和入渗速率明显下降,下渗水流在一定限度内滞留于秸秆层以上,秸秆夹层同时具有减渗性,使下渗水量明显减小;土壤盐分在秸秆夹层以下一定深度范围内出现峰值。秸秆长度影响盐分滞留深度,秸秆长度10 cm处理全盐含量最大值深度较秸秆长度1 cm处理有所下移;秸秆夹层也影响着水分入渗过程中离子的交换与吸附,Cl–入渗后在剖面深度的变化规律与全盐变化规律相同,HCO3–对秸秆夹层的敏感性明显强于SO42–,SO42–对水分依赖性较强,含水量足够大时才能引起它的快速运移。

In this study, a constant head infiltration device was used to investigate the distribution characteristics of onedimensional vertical infiltration water and salt in layered saline and alkaline soil with a subsurface straw layer at a depth of 20 cm below soil surface. Four levels, 0 （CK）, 6 000, 12 000, and 18 000 kg/hm2, of straw amount with 2 levels, 1 and 10 cm, of straw length were set up to investigate their influences on the distribution of infiltration water and salt in saline alkaline soil. The results showed that the subsurface straw layer in saline alkaline soil clearly lowered water infiltration with apparent drops in accumulated infiltration amount and infiltration rate. And infiltration water stopped above the straw layer within certain limits. At the same time, the subsurface straw layer prevented water from going through, resulting in an obvious decrease of water below it. Salt content peaked at a certain depth below the straw layer. And straw length exerted an effect on the depth where salts were stopped with the peak of the total salt content at a deeper position in the 10 cm straw length treatments compared with that in the 1 cm treatments. The subsurface straw layer also impacted the ion exchange and adsorption during water infiltration. The changes of Cl- distribution in the soil profile after infiltration was similar to that of total salt. HCO3- was obviously more sensitive to the subsurface straw layer than SO2- which relied heavily on water and only migrated rapidly when water content was high enough.