设施栽培条件下沼液滴灌水盐调控机制研究

设施栽培条件下利用沼液灌溉可有效增加土壤中的养分，实现农业废弃物资源化，但因沼液含盐量较高，长期灌溉可能造成土壤次生盐渍化，而控盐过程又容易导致过量硝酸盐养分淋失。本项目拟通过控制土壤20cm深度处的土壤水基质势（SMP），探索维持土壤盐分平衡并减少硝酸盐淋失的沼液滴灌水盐调控机制。研究设施栽培条件下沼液滴灌的土壤水盐运移规律，模拟20cm深度处的SMP与土壤盐分运移的关系；明确沼液滴灌的SMP控制阈值与土壤盐分积累、氮素利用和硝酸盐淋失的关系，从而确定降低盐分积累速率并减少硝酸盐淋失的SMP控制阈值；同时，基于作物的耐盐性，探讨淡水淋洗时长（频率）对土壤盐分淋洗效果和硝酸盐运移、分布和淋失的影响，提出淋洗土壤盐分并控制硝酸盐淋失的淡水淋洗方法。本研究可为实现沼液安全高效利用提供科学依据和应用参考。

The field application of digested biogas slurry plays an important role in reducing agricultural effluent and increasing waste recycling. However, in greenhouse, the high salinity of slurry could alleviate soil secondary-salinization, and the nitrate tends to be leached out of rootzone soil following water if the increased soil salinity is leached by irrigation. In this study, drip irrigation based on the soil matric potential (SMP) in the depth of 20 cm will be used to investigate the mechanism of water-salt regulation using digested biogas slurry for controlling soil salinity and reducing nitrate loss. Firstly, the rule of water and salt transportation under drip irrigation will be studied, and based on which, a mathematical model of soil salinity and SMP will be established. Secondly, this study will research the relationships between SMP threshold of drip irrigation and increasement of soil salinity, nitrogen utilization efficiency, and nitrate loss amount, and then a proper SMP threshold value will be tested to slow the rates of nitrate loss and soil salt accumulation. Thirdly, according to the threshold of crop salt tolerance, the effect of freshwater leaching duration on the decrement of soil salinity, nitrate distribution and loss will be also studied, in order to achieve less nitrate loss during leaching. Finally, based on the above, we will develop the mechanism and method of water-salt regulation using drip irrigation with digested biogas slurry, which can improve the theory of water-salt regulation, and guide the practice.