基于HYDRUS-1D模型的河套灌区典型夹砂层耕地水分利用分析

为研究夹砂层耕地水分利用规律，以河套灌区典型夹砂层土壤耕地为研究对象，利用在春玉米生育期田间监测数据，应用土壤水分运动数值模型，探究对夹砂层土壤田间蒸散发、作物耗水及深层土壤水分的补给与深层渗漏规律。选择2种土壤的夹砂层埋深梯度S1（40～95 cm）、S2（60～110 cm），设置了3个灌水水平W1（252.5 mm）、W2（315.85 mm）、W3（378.75 mm）开展田间试验，同不含夹砂层处理B作对照，并应用HYDRUS-1D模型模拟春玉米生育期田间蒸散发，土壤水分深层渗漏及地下水补给耕层水量与根系吸水量，与不含夹砂层处理对比分析夹砂层对田间水分利用影响。结果表明：随着砂层埋深增加，棵间蒸发损失减小，叶面蒸腾水量增加；不含夹砂层处理玉米田间毛管向上补给水量较浅埋砂层与深埋砂层处理分别大57.01%、118.53%，灌水量为315.85 mm时含夹砂层处理的土壤水分深层渗漏最小；玉米生育期内根系吸水量随砂层埋深的增加而减少，不含夹砂层处理根系吸水量最大。浅埋砂层与深埋砂层处理分别为蒸散量的55.51%、61.31%，不含夹砂层处理为66.69%；暂时性亏缺水量从大到小依次为：S2、S1、B，水分从大到小依次为：B、S2、S1。综合考虑夹砂层土壤水分迁移、作物水分利用规律，建议在夹砂层耕地春玉米灌溉根据砂层分布因地制宜定灌溉制度，当夹砂层埋深在40～110 cm范围时，推荐春玉米在生育期灌溉定额为315.85 mm。该研究结果可为河套灌区含有夹砂层农田灌溉制度的制定提供理论指导。

Water use analysis of cultivated land with typical sand layers in Hetao Irrigation District of Inner Mongolia using HYDRUS-1D model

Abstract: Extensive sand layers are widely distributed over the impact plain of the Yellow River, particularly for Hetao Irrigation Areas in Inner Mongolia of western China. The migration of water and salt under the soil sand layer has posed a great influence on soil water utilization, soil salinization control, and crop growth. In this study, a numerical model of soil water movement was proposed to investigate the field evapotranspiration, crop water consumption, water supply, and deep soil water leakage in the sand layer using the data of field monitoring and laboratory experiments during the growth period of spring maize. Taking the cultivated land of the typical sand layer in the Hetao Irrigation Area as the research object and planting crop as spring corn, two gradients of buried depth were selected: S1 (40-95 cm) and S2 (60-110 cm) of the sand layer in the soils. Three irrigation levels were also set to carry out the field experiment, and then to compare with BWI without sand layer, including W1 (252.5 mm), W2 (315.85 mm), and W3 (378.75 mm). A HYDRUS-1D model was selected to simulate the field evapotranspiration during the growth period of spring maize, deep seepage of soil water, groundwater recharge, and root water absorption. In addition, the temporary water deficit and water productivity were calculated during the whole growth period. Water use in the cultivated land with sand layer was then compared with that without sand layer. The results showed that the soil evaporation loss between grains decreased, whereas, the leaf transpiration water increased, with the increase of buried depth of the sand layer. Specifically, the soil layer above the sand layer was thicker, the soil water storage was larger, the surface soil moisture content was higher, and the soil negative pressure was lower when the buried depth of the sand layer was larger. As such, the deep soil water was less replenished upward through the capillary action. At the same time, there was less leakage to the deep layer below the sand layer after irrigation. Furthermore, the upstream water supply of maize in the field without sand layer increased by 57.01% and 118.53%, respectively, compared with the treatment of shallow (40-95 cm), and deep sand layer (60-110 cm). More importantly, the deep-water leakage of soil under the treatment of sand layer was the least, when the irrigation amount was 315.85mm. Correspondingly, the water absorption of maize roots decreased with the increase in the buried depth of the sand layer, where the largest was found without sand layer during the growth period. Specifically, the shallow (40-95 cm) and deep sand layer (60-110 cm) treatment were 55.51% and 61.31% of evapotranspiration, respectively, whereas, the treatment without sand layer was 66.69%. The irrigation system can be determined for spring maize in the sand layer, according to the sand layer distribution and local conditions. Particularly, the recommended irrigation quota of spring corn can be 315.85 mm during the growth period, when the sand layer was similar to the S1WI and S2WI treatment. The recommendation can be attributed to avoiding the leakage loss of irrigation water in the deep soil water of the farmland with the sand layer. The findings can also provide important theoretical guidance for the formulation of a farmland irrigation system with the sand layer in the Hetao Irrigation District.