The Effects of Drip-irrigation Amount on Soil Salinity in Film-mulched Corn Field in Hetao Irrigation District

Abstract

【Objective】 Hetao Irrigation District is one of the largest irrigation districts in China. Its irrigation relies on Yellow River water. As the available river water for the district continually dwindles, drip irrigation has been increasingly used to improve irrigation water use efficiency. This paper is to study the impact of drip irrigation combined with mulching on dynamics of soil salt in corn fields. 【Method】 The experiment was conducted in a field with the Jintian No. 8 variety used as the model plant. It compared two drip irrigation amounts: 76 mm (F1) and 60 mm (F2), and the intra-rows were mulched with plastic film. In each treatment, we measured the changes in soil moisture and salt content at different soil depths, and the measured data were used to calibrate the HYDRUS-2D. The calibrated model was used to study the response of soil water and soil salt to other irrigation amounts: 81 mm (W1), 135 mm (W2), 171 mm (W3) and 204 mm (W4). 【Result】 During growth period of the corn, the total salt content in the 0~100 cm soil layer and the salt in soil outside the mulched zone were lower in F1 than in F2, while the temporal change in salt in the soil underneath the film was not distinguishable between F1 and F2. During the growth period, the time-trending of the salt in soil underneath the film was approximately the same for F1 and F2. After harvesting, F1 and F2 desalinated the 0~100 cm soil layer by 50.1% and 10.8%, respectively, of which the associated desalinization of the soil underneath the film was 44.7% and 148.5% respectively. Before the autumn irrigation, F1 and F2 increased the total salt in the 0~100 cm and 0~60 cm soil layers; F1 reduced the total salt in the 0~100 cm of soil and reduced the increase of salt in soil underside the film, compared to F2. There is a good agreement between measured and simulated water content ant soil salinity, indicating that the parameters and the model correctly capture the soil properties and water and salt flow in the soil. When the irrigation amount was 162 mm, salinity of the 0~20 cm soil was low after the irrigation and it took more time for the salt to re-accumulate in this soil layer. When the irrigation amount was reduced to 108 mm, salinity of the 0~40 cm of soil after the irrigation remained high. 【Conclusion】 The drip irrigation water volume of 171 mm and 204 mm not only reduces salinity of the root zone (0 to 40 cm ), but also removes the salt from the root zone to soil outside the mulched zone - the non-root zone. Our results have practical implications for managing mulched drip-irrigated corn in Hetao Irrigation District.

Keywords

• salinized soil
• soil moisture
• mulched drip irrigation
• hydrus-2d