Purpose

Soil salinization and degradation in the arid and semiarid areas are a worldwide phenomenon. Soil capping with capillary barriers is a potential practice to hydraulically isolate contaminated soils, which may improve the soil environment for plant growth. This study aims to investigate the influences of soil capping on crop growth and soil salinization control in the arid area with shallow groundwater tables.

Materials and methods

A one-dimensional agro-eco-hydrological model, LAWSTAC, capable of simulating water and solute transport in layered soil coupled with crop growth, was applied for simulating sunflower growth under field condition in Arid Northwest China. The model was calibrated and validated with the experimental data of 2012 and 2013 crop seasons. The calibrated model was then used to explore how the soil capping consisting of combinations of fine soil (10, 15, 17, 19, and 20 cm thick) and coarse sand (10, 5, 3, 1, and 0 cm thick correspondingly) would influence the soil water and salt dynamics, and seed yield.

Results and discussion

Simulation results by LAWSTAC compared well with the observed soil water content, salt concentration, leaf area index, and seed yield. Further scenario simulations showed that a sand layer in the soil capping could greatly affect the water and salt distribution in the soil above and below the sand layer. Though soil capping could decrease the water storage (WS) in the root zone, it caused no obvious increase in water stress to root uptake for sand thickness of 1–3 cm and also considerably reduced the root zone salt content (SC) in crop season compared with that without soil capping. The average WS during the crop season showed a negative correlation with the thickness of sand layer in the soil capping. The average SC from planting to harvest was significantly lower for thicker sand in the soil capping. To soils with high background salinization, the increase of sand thickness would be helpful for enhancing seed yield, until it reached a critical value.

Conclusions

Coarse soil layer in the soil capping could prevent salt moving into the root zone, while fine soil could supply water to plant once water in coarse soil was low. Thus, in a long run, the soil capping consisting of combinations of fine and coarse soils with certain thicknesses would be an alternative practice for saline soil reclamation and improving crop production in arid area with shallow groundwater tables and soil salinization.

中文翻译：

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利用耦合农业生态水文模型评估分层土壤对水流，溶质运移和作物生长的影响

目的

干旱和半干旱地区的土壤盐碱化和退化是一种全球现象。用毛细管屏障覆盖土壤是水力隔离受污染土壤的一种潜在做法，这可以改善植物生长的土壤环境。本研究旨在调查地下水位较低的干旱地区土壤封盖对作物生长和土壤盐碱化控制的影响。

材料和方法

利用一维农业生态水文模型，能够模拟西北干旱地区田间条件下向日葵的生长，该模型能够模拟层状土壤中的水分和溶质运移并结合作物生长。使用2012年和2013年作物季节的实验数据对模型进行校准和验证。然后，使用校准后的模型来研究土壤封盖如何由细土（10、15、17、19和20厘米厚）和粗沙（分别为10、5、3、1和0厘米厚）的组合组成会影响土壤水分和盐分的动态以及种子的产量。

结果和讨论

LAWSTAC的模拟结果与观察到的土壤含水量，盐分浓度，叶面积指数和种子产量进行了很好的比较。进一步的场景模拟表明，土壤覆盖层中的沙层会极大地影响沙层上方和下方土壤中的水和盐分分布。虽然土壤封盖可以减少根部区域的储水量（WS），但对于1–3 cm的沙土厚度，它不会引起水分胁迫对根系吸收的明显增加，并且还大大降低了作物季节的根部含盐量（SC）与没有覆土的情况相比。作物季节的平均WS与土壤盖层中沙层的厚度呈负相关。对于土壤覆盖层中较厚的沙子，从种植到收获的平均SC显着降低。对于高背景盐化的土壤，

结论

覆盖层中较粗的土壤层可以防止盐分渗入根部区域，而粗土壤中的水分含量低时，细土壤可以为植物供水。因此，从长远来看，由一定厚度的细土壤和粗土壤的组合组成的土壤封盖将是盐渍土壤开垦和通过浅层地下水位和土壤盐碱化提高干旱地区农作物产量的一种替代方法。