覆砂对土壤入渗、蒸发和盐分迁移的影响

探讨覆砂厚度对土壤水分入渗、蒸发、盐分迁移的影响,对新疆干旱区农田抑盐、保水及合理的覆砂制度制定具有重要意义。本文采用定水头法入渗和模拟稳定蒸发条件,研究覆砂厚度对土壤水分入渗、蒸发过程以及盐分迁移的影响。以覆砂厚度为影响因子,在土壤表层设置4个厚度,分别是0(对照)、1.7、3.6、5.7 cm。研究结果表明:(1)覆砂抑制了土壤水分净入渗能力,这一抑制作用随着覆砂厚度增加而减弱;(2)覆砂可以显著抑制土壤蒸发,随着覆砂厚度的增加抑制力增大。在20天蒸发过程中,覆砂处理蒸发呈稳定态势,且累积蒸发量符合线性方程,而对照符合Rose经验公式;(3)覆砂可以改变土壤盐分在剖面中的运移,尤其减弱了盐分的表聚。总之,覆砂显著地抑制了土壤蒸发和盐分表聚,即在覆砂厚1.7 cm上就可达显著效果,但对土壤的净入渗能力具有抑制作用。

Effects of sand mulching on soil infiltration, evaporation, and salt distribution

Soil secondary salinity and fresh water shortage are two major problems limiting crop growth and yield improvement. Therefore, analysis of effects of sand mulching on soil water infiltration, evaporation, and salt transportation is of some great significance to optimizing the method of sand mulching in arid regions. A laboratory simulation experiment was conducted to study processes of soil water infiltration, soil water evaporation, and salt transportation under sand mulchings different in thickness, in the condition of constant water head infiltration and simulating steady evaporation. The sand used in this study varied from 0.2 mm to 2 mm in particle size. The experiment was designed to have four treatments in sand mulching, i e., 0 (control), 1.7, 3.6 and 5.7 cm, in thickness of the sand layer on the surface of soil. Results show that (1) Sand mulching has an obvious inhibitory effect on soil water net infiltration, and the thicker the sand mulching the less the soil water infiltration, namely, the effect increases significantly with the thickness of the sand mulching; (2) Sand mulching dramatically reduces soil water evaporation, and the thicker the sand mulching the less the soil water evaporation, demonstrating a significant positive correlation between soil water evaporation from surface and the thickness of the sand mulching; and it was found that during the 20 days of experiment, the evaporation process in the sand mulching treatment was rather stable, and the soil water cumulative evaporation fitted a linear equation and the Rose empirical equation as well; (3) Sand mulching alters soil salt transportation and distribution in soil profile, especially reducing accumulation on the top-surface soil layer. To sum up, sand mulching significantly inhibits soil water evaporation from soil, and surface accumulation of soil salt. Sand mulching, 1.7 cm or more in thickness, is sufficient to create the effect, but it also affects net infiltration of the soil. To sum up, sand mulching significantly inhibits soil water evaporation from soil, and surface accumulation of soil salt. Sand mulching, 1.7 cm or more in thickness, is sufficient to create the effect, but it also affects net infiltration of the soil.