棚内微咸水覆膜滴灌下带间土壤水盐分布特征模拟

Simulation of Soil Water and Salt Distribution Characteristics within Area between Drip Tapes under Mulched Brackish Water Drip Irrigation in Greenhouses

微咸水覆膜滴灌在发挥节水效益的同时应避免土壤盐分的积聚,在缺乏大水淋洗的设施大棚内,覆膜对土表局部蒸发的抑制伴随滴灌湿润体的交汇,加剧了滴灌带带间水盐分布的不规则性,导致土壤积盐的潜在风险增加。针对上述问题,以布设形式为“两膜两行”的覆膜滴灌田间小区为试验对象,通过HYDRUS模型构建了不同滴头流量(0.5~3.0 L/h)及膜间裸地间距(0~50 cm)组合情景下的二维土壤剖面模拟域,并针对滴头处的带间区域进行水盐动态分布的模拟研究。结果表明,所建模型能较为精确地描述带间剖面内水盐的分布状况,且模拟精度随与滴头水平距离的减小而提升。当膜间裸地间距从50 cm缩小至0 cm时,带间剖面土壤的平均含水率从25.12 cm^(3)/cm^(3)上升至28.76 cm^(3)/cm^(3),平均土壤盐分质量浓度从9.53 g/L下降至6.25 g/L;滴头流量对带间区域内土壤水盐含量的影响程度相对较低,流量0.5、3.0 L/h下土壤体积含水率及盐分质量浓度的最大差异仅分别为0.14 cm^(3)/cm^(3)和0.22 g/L,且均出现在膜间裸地间距为50 cm的情景下。经多轮灌水蒸发后,带外区积聚的盐分将向带间区扩散,并随膜间裸地间距的减小,土壤含盐量最低值的水平位置将从滴头处向带间区推移。研究成果可为设施大棚环境下选取适宜的低盐作物栽种位置提供理论依据。

Film-mulched drip irrigation with brackish water should avoid soil salt accumulation to maximize the benefits of water-saving.However,soil leaching by rainfall or flood irrigation is lack under greenhouses condition,the partial inhibition of surface evaporation by film mulching combined with the wetted volume intersection due to double-point source drip irrigation exacerbates the irregularity of water and salt distribution in the area between drip tapes(ABDT),which is not conducive to the effective implementation of salt control measures.Therefore,taking the field experimental plot of mulched drip irrigation with the layout of“two films and two rows”as the research object,and using the HYDRUS-2D model to simulate the dynamic distributions of soil water and salt in ABDT based on the two-dimensional simulation domains considering different drip discharge fluxes(0.5~3.0L/h)and bare soil spacing between films(0~50cm).The results indicated that the established model can accurately describe the water and salt distribution in ABDT,and reducing the horizontal distance from the emitter could obtain a high simulation accuracy.As the bare land between the films was decreased from 50cm to 0cm,the average moisture content of the soil in ABDT was increased from 25.12cm^(3)/cm^(3)to 28.76cm^(3)/cm^(3),and the average soil solute concentration in ABDT was decreased from 9.53g/L to 6.25g/L.The effect of drip discharge fluxes on soil water-salt distribution in ABDT was relatively low,the maximum differences in soil volume moisture content and salt mass concentration between treatments with discharge fluxes of 0.5h/L and 3.0h/L were only 0.14cm^(3)/cm^(3)and 0.22g/L,respectively,and both occurred in the bare soil spacing between films of 50cm.Additionally,after long-term dry-wet alternation,salt accumulated on the outside of the drip belt might diffuse inward to ABDT,and with the decrease of bare soil spacing between films,the horizontal position of the lowest soil salinity would move from the location of dripper to ABDT.Findings of this research can provide a theoretical basis for selecting suitable low-salinity planting locations for crop cultivation in greenhouse condition.