Salt Accumulation and Distribution under Mulched Drip Irrigation

Abstract

【Background and objective】 Mulched drip irrigation can push salt out of the root zone to sustain crop growth, but evaporation from soil outside the mulching film drives the salt to redistribute. Understanding salt accumulation and redistribution under mulched drip irrigation is important to alleviate soil salinization. Taking Xinjiang as an example, the objective of this paper is to experimentally study salt accumulation and redistribution in soil under mulched drip irrigation. 【Method】 The experiment was conducted in a laboratory using repacked sandy soil and loamy soil. For each soil, we compared high evaporation and low evaporation both adjusted by temperature. Salt distribution in the horizontal and vertical directions was measured in each treatment. 【Result】 Regardless of soil type, salt content in the soil surface decreases exponentially along the distance away from the emitter. In the vertical direction, salt content in the soil outside the mulching film is distributed in a “Γ” type, and the salt mainly accumulates in the soil proximal to the surface. Under high evaporation, the average salt content in the surface (0~2 cm) of the sandy soil is 7.3 times that in the subsoil below the depth of 2 cm, while the average salt content in the surface (0~2 cm) of the loamy soil is 8.4 times that in the subsoil below the depth of 2 cm. At low evaporation, the associated salt content in the surface of the sandy and loamy soils is 7.2 times and 7.9 times, respectively, that in the subsoils. Soil evaporation is the main determinant of salt accumulation in the soil surface. Increasing soil moisture content, temperature or evaporation enhances evaporation, leading to an increase in salt accumulation in the soil surface. Because salt solubility drops when soil water content decreases, there is a peak in salt accumulation rate during the evaporation process, which is positively correlated with temperature. 【Conclusion】 The evaporation of soil water leads to salt precipitation around the soil surface. Salt accumulation at the loamy soil surface is higher than that at the sandy soil surface. These results can help design mulched drip irrigation for crops in salt-affected soils.

Keywords

• mulched drip irrigation
• soil texture
• salt accumulation
• accumulate rate