【作者】 杨德军；

【导师】 张土乔； Zhang Kefeng； Greenwood D J；

【作者基本信息】 浙江大学 ， 市政工程， 2009， 博士

【摘要】 开展对土壤-作物-大气系统（简称SPAC系统）土壤水动力学和水肥优化使用决策支持系统的研究,可以提高水资源尤其是农业用水效率,降低农作物成本,提高农药和化肥的利用率,有效地缓解过量农药和化肥进入地表或地下水体导致的环境污染问题。本文采取了理论分析、数值模拟和算例验证相结合的方法对以下几个问题进行研究和探讨。1.通过引入生长折减系数等理论,完善了过量施肥导致土壤中过量氮存在、产生的负渗透压抑制作物生长的理论,进一步发展了EU-ROTATE_N模型。实例验证表明:新研发的模块相对较合理,能够对多种作物在施肥条件下作物干重和作物上部（除须根）的含氮量进行一定的模拟,并能有效地反映过量施肥导致土壤负渗透压的影响效果。2.通过引入相关的根系生长动力学模型、根长密度分布函数以及蒸发和蒸腾计算模型等理论,与二维有限元程序SWMS₂D相耦合,发展了模拟SPAC系统的土壤水动力学有限元模型。实例验证表明:降雨对土层含水率分布的影响随着深度的增加而减小;蒸腾量和蒸发量的模拟结果较为可靠;根长密度分布具有一定的阶段性。3.通过改进上下边界条件,发展了裸地条件下土壤水动力学IRE模型（即积分型的Richards方程解法）。降雨数值试验结果表明:新模型的模拟结果介于FEM和Green Ampt模型模拟结果之间,更符合实际情况;蒸发试验结果表明:模拟结果与实验数据基本吻合,克服了FEM模型不稳定等不足;现场试验结果表明:累积入渗量、累积蒸发量和下边界累积排水量的模拟结果与FEM模拟结果基本吻合;土壤含水率分布接近FEM的计算结果和实验数据,其主要差别出现在顶层6cm的土体内。4.由于外界条件的复杂性和土体性质的多样性,土体在一定外界条件下的响应问题难以得到定量化描述。通过对欧洲5种典型土体进行100天的蒸发数值试验,在含水率分布和蒸发总量等数据上进行对比,探讨了欧洲5种典型土体的响应规律,为实际应用提供了一定的参考价值。5.针对EU-ROTATE_N模型中以CASCADE方法为核心的水模块参数难确定,预测结果不够准确等问题,通过引入裸地条件下改进的IRE模型,与现有的EU-ROTATE_N模型进行耦合,发展了有植被条件下土壤水动力学IRE模型,进一步发展了EU-ROTATE_N决策支持系统,实例验证表明:不同深度处土壤含水率随时间的变化与试验数据基本吻合,根长及根长密度模拟结果与实验值吻合,蒸腾量和蒸发量的模拟结果较为可靠,土壤中含氮量模拟结果较吻合。更多还原

【Abstract】 The study of soil hydrodynamics and the model-based decision support systems for optimizing resource use is of great importance.Optimum use of resource can enhance the use efficiency of water,pesticide and fertilizer in agriculture,reduce the crop production cost,and minimize the environmental consequences.In this study,a systematic method was employed to develop such models for optimizing water and nitrogen fertilizer use in crop production.The main findings of the study are summarized as follows.1.A growth reduction coefficient was introduced in the EU-Rotate_N model to consider the negative osmotic effect caused by excessive application of nitrogen fertilizer on crop growth.Results show that the newly-developed module works well. It gives overall good descriptions of crop dry weight（excluding fibrous roots） reduction by mineral N in the soil over a range of crops.2.By incorporating a recently developed root growth module,and an approach of estimating evapotranspiration into a two-dimensional finite element method model SWMS₂D for soil water movement,we developed a new model for water dynamics in the soil-plant-atmosphere continuum system.The model was validated against the measurements from field experiments.It was found that the root module was able to reproduce the root distribution patterns measured at intervals;the effect of rainfall on soil water content down the profile decreased with the depth,and the simulated soil evaporation and crop transpiration were reasonable.3.We further developed an Integrated-Richards-Equation（IRE） based hydrodynamic model for bare soils by extending the conditions imposed on the top and lower boundaries.The application of the model to a case of rainfall infiltration revealed that the simulated results were between those by the FEM and by Green Ampt method.The model was also validated data from an evaporation experiment. Good agreement was obtained between simulation and measurement.The robustness of the model was also domenstrated in reproducing data from a field evaporation experiment.Good agreement was obtained in the amounts of cumulative infiltration, cumulative evaporation and cumulative drainage at the lower boundary between the simulated results by the model and the FEM model.The differences,mainly limited to the top 6 cm soil column,might be due to the diffusivity used in IRE model and the conductivity used in the FEM model.4.The responses of soil to different external conditions cannot easily be quantified because of the complexity in external conditions and the soil.In this study, simulations were carried out for 5 different European soils near saturation subject to a high evaporation and free drainage for 100 days.Comparisons including water content distribution and evaporation amount were made.The results could be used for the practical purposes.5.To improve the accuracy of hydrological simulations by the cascade type of algorithm in the EU-ROTATE_N model,the newly developed IRE model,which is able to consider water transfer in various processes in the SPAC system,was incorporated into the EU-ROTATE_N decision support system.The improved model was tested in the wheat-soil system.Good agreement was obtained for water content down the soil profile at different time internals between simulation and measurement. Simulated results of soil evaporation,crop transpiration and the mineral nitrogen content in the soil were reasonable.This suggests that generally the model gives good predictions of water and nitrogen transfers in the crop-soil system,and thus has the potential to be used in practice.更多还原