考虑根系补偿性吸水的旱区膜下滴灌二维土壤水-作物耦合模型研究

Water shortage is a limiting factor for sustainable agricultural development in the oasis arid region of Northwest China. As a water saving and high yield irrigation technique, mulched drip irrigation is popular in this region. Therefore, quantitative simulation of soil water transport and crop growth processes is very important and significant for solving the water shortage problem in the study area. In this project, the technique combing the field experiment with mathematical model simulation would be used to study the relationship among soil water transport and crop evapotranspiration and yield, to analyze the interaction between root water uptake and crop growth under mulched drip irrigation. In addition, the effect of compensated root water uptake on the crop yield would be quantified in this study. Meanwhile, a two dimensional compensated root water uptake model is to be developed. And then, a two dimensional mathematical model is to be developed on the basis of coupling a two dimensional soil water transport model and crop growth model for the mulched drip irrigation. After that, the field experiment data set will be used to calibrate and validate the coupled model. The response of crop yield to various irrigation scenarios will be analyzed by the calibrated coupled model. Finally, the appropriate irrigation management under mulched drip irrigation for the study area will be established. In summary, this research could promote the studies on the quantitation of the interaction between soil water and crop growth under mulched drip irrigation. Furthermore, it would be useful for the agricultural water management strategies in the arid region.

水资源短缺是制约西北内陆旱区农业可持续发展的重要因素。膜下滴灌作为一种节水高产的灌溉技术在该地区得到了广泛的应用。因此，合理定量描述膜下滴灌条件下土壤水分运动及作物生长过程，对解决研究区水资源短缺问题具有重要意义。本项目采用田间试验与数学模型模拟相结合的研究方法，探讨膜下滴灌条件下水分与作物耗水及产量之间的关系；分析根系吸水与作物生长之间的相互作用关系；定量描述补偿性根系吸水对作物产量的影响；发展二维补偿性动态根系吸水模型；建立适合于膜下滴灌等条件下的基于补偿性动态根系吸水机制的二维土壤水与作物生长耦合模拟模型；率定验证耦合模型的正确性及稳定性；并基于率定后的模型进行膜下滴灌条件下作物产量对灌水的响应分析，提出适合于研究区的膜下滴灌灌水制度。预期结果对定量表征膜下滴灌条件下土壤水分与作物生长之间的相互作用机制具有重要学术意义，同时可为旱区农业节水提供科学依据和决策支持。

为了合理定量描述滴灌等条件下土壤水分运动及作物生长过程，本项目采用盆栽试验与数学模型相结合的方法分析了滴灌条件下水分与作物耗水及产量之间的关系。通过开展确定性的盆栽试验，研究了不同质地（壤土、砂土）、滴灌灌水水平下作物根系生长动态及分布的差异性，揭示了作物补偿性根系吸水与土壤质地及灌水量之间的响应关系；基于根系生长动态建立了补偿性动态根系吸水模型；构建了适合于滴灌、膜下滴灌等条件下的基于补偿性动态根系吸水机制的二维土壤水与作物生长耦合模拟模型；定量描述了补偿性根系吸水对作物产量与耗水的影响。该课题研究结果对定量表征滴灌或膜下滴灌条件下土壤水分与作物生长之间的相互作用机制具有重要学术意义，同时可为旱区农业节水提供科学依据和决策支持。主要研究结论如下：.（1）不同土质条件下，玉米根系分布差异较大，均质壤土和均质砂土下根系分别分布于0~70cm土层和0~30cm土层；均质壤土处理根长密度比均质砂土高69%；均质壤土和均质砂土条件下50%ETc处理根长密度分别比75%ETc处理和100%ETc处理高40.4%~51%和43.4%~53.7%。.（2）均质壤土和均质砂土下玉米产量无显著性差异；均质壤土100%ETc处理和75%ETc处理产量显著高于50%ETc处理55%和22.5%；砂土不同灌水处理之间产量无显著性差异。.（3）基于构建的二维补偿性动态根系吸水模型以及CHAIN-2D模型中的二维土壤水分运动、EPIC模型中的作物模块，开发了考虑根系补偿性吸水的二维土壤水与作物生长耦合模拟模型。.（4）补偿性根系吸水模型中水分亏缺临界指数从0.4增加到1.0时，作物相对产量随水分亏缺指数先增加后减小，变化幅度为3%左右；而相对耗水量随水分亏缺指数增加而减小，减小的幅度达到15%。模型研究结果表明75%ETc和50%ETc处理水分亏缺临界指数分别为0.8和0.9。