可降解地膜覆盖对旱区盐渍化滴灌农田水热盐的影响机制及模拟研究

The drip irrigation under mulch have develop rapidly in recent years, and played an important roles in saving water, controlling salinity and increasing crop production, however, plastic film mulch residual bring about large plastic pollution, and seriously influence water and fertilization use efficiency and agriculture sustainable development.Because the biodegradable agricultural mulch film can be completely decomposed in to CO2 and H2O by bacteria, it had been widely applied. But its water, heat and salt movement mechanism has not clear. The project study on the movement and simulation of soil water, heat and salt casued by biodegradable mulch film in the arid and salinized area. The effect of biodegradable mulch film on farmland microbial communities, soil structure, soil physical property, hydraulic parameters, crop growth, evapotranspiration and water, heat and salt will be continuously monitored. The evapotranspiration model will be reformed by considering the variant of soil and crop radiation absorption, and the model of soil water, salt movement will be improvement by considering the variant of hydraulic parameters based on Hydrus model, and the soil water, heat, salt would be simulated by the model under different situations, and the optimal irrigation program and application pattern of biodegradable agricultural mulch film would be proposed for a successful spread of biodegradable film and agricultural sustainable development.

近年来膜下滴灌呈现了跨越式发展，对节水、控盐、增产等都起到了重要作用，但塑料农膜残留问题日益严峻，严重影响了水肥高效利用及农业可持续发展。生物降解地膜能被微生物完全分解成CO2和H2O，有效解决了农膜残留的污染问题，已被广泛应用，但其影响农田水热盐影响机理尚不明确，配套灌溉技术不成熟。本项目针对滴灌农田中可降解地膜的降解性和微渗透性影响农田水热盐迁移及模拟等的新问题开展研究，通过对不同降解速度可降解地膜在不同阶段对滴灌农田微生物、酶活性、土壤结构、物理性质、水力参数以及作物生长指标、农田蒸散、水热盐变化等连续监测的基础上，分析其灌溉效应，考虑地膜降解所导致的反射率等变化对作物、土壤辐射吸收影响建立蒸散模型，在Hydrus模型基础上考虑水力参数动态变化建立其滴灌农田水热盐运移模型并对不同情景进行模拟，以期建立滴灌农田可降解地膜覆膜下的覆膜模式及灌溉制度，为农业可持续发展奠定基础。

随之水资源短缺加剧，膜下滴灌由于节水、控盐、增产效果明显，得到了大规模发展，但是塑料地膜残留问题是制约农业可持续发展的重要因素。而降解地膜由于能在自然条件下分解为CO2 和 H2O，是今后解决农膜残留的主要措施。然而降解地膜覆盖条件下农田水热盐氮过程尚不清楚，配套灌水施肥技术模式不成熟。本项目通过4年的田间、室内试验和数值模拟,探索了降解地膜降解特征；降解地膜覆盖对作物生长及耗水量的影响；降解地膜覆盖对土壤温度的影响；降解地膜覆盖对水氮及交互效应的影响；基于Hydrus构建降解地膜覆盖滴灌农田水分迁移模型；降解地膜覆盖对土壤水、盐的影响；降解地膜覆盖农田节水高效灌溉制度。主要成果如下：（1）降解膜在降解诱导期内破损率与塑料地膜相近，随着生育期推进降解和破损明显大于塑料地膜，拉伸强度也低于塑料地膜，试验结束后地膜破损率可达50%左右。（2）降解地膜覆盖在破损前覆盖效果与塑料地膜一致，在破损后期耗水量大于塑料地膜，但是产量与塑料地膜覆盖无统计学差异。（3）基于红外热成像技术获得地表瞬时温度大小顺序为黑膜处理>白膜处理>无膜处理，在作物生长后期降解膜由于破损从而地温相对较低。（4）可降解膜覆盖下灌水量、施氮量及水氮耦合效应均对玉米的产量及其构成因素、WUE和 PFPN有显著影响，影响程度为灌水量＞施氮量＞水氮耦合。（5）将降解膜覆盖区设定为变流量边界，将其建立与破损相关，基于Hydrus软件构建降解膜覆盖滴灌农田土壤水分运移模型。（6）在生育后期降解地膜主要影响0~20cm，尤其是0~10cm土层的土壤含水率，但降解膜能提高雨水利用率。降解膜覆盖在作物生育期内0~40 cm土层EC值与塑料膜覆盖无显著差异，但都明显低于无膜处理，覆膜能较好的控制土壤上层（0~40 cm）盐分。（7）通过二元回归方程及AquaCrop模型模拟得到了适合该地区的灌溉水量和施肥量。综上，本项目从降解膜的降解特性，对作物生长，对作物耗水的影响， 对土壤水、热、氮、盐的影响，并构建了Hydrus模型模拟，优化出降解膜覆盖下滴灌农田节水灌溉制度，为农业可持续发展奠定基础。