土壤—作物系统水碳氮过程耦合模型构建及在水氮管理中的应用

发布时间：2018-06-30 19:21

本文选题：土壤水分运动 + 碳氮循环　；参考：《中国农业大学》2017年博士论文

【摘要】：长期以来我国粮食增产过多依赖水肥资源的大量投入,不仅增加了粮食生产成本,而且加大环境污染风险。因此,定量描述农田生态系统中土壤水分动态、氮素去向和作物生长过程,对水氮资源高效利用、作物生产决策和环境保护具有十分重要的意义。本文在借鉴国内外土壤水分溶质运移、碳氮循环及作物模型理论方法的基础上,构建了一个适合我国气候环境条件及农业管理特点的土壤-作物系统水碳氮过程耦合模型WHCNS(soil water heat carbon and nitrogen simulation),并应用田间数据检验了该模型在我国高度集约化农田生产系统中的适用性,对当前的水肥管理措施进行了优化,全文主要结论如下:构建的WHCNS模型以天为步长,土壤水分入渗和再分布过程分别采用Green-Ampt模型和Richard's方程来描述。土壤氮素运移使用对流-弥散方程来描述,源汇项中考虑氮素循环的各个过程(有机质矿化、尿素水解、氨挥发、硝化、反硝化和作物吸收等),有机质周转模块直接来源于Daisy模型。作物模型可选择复杂的PS123模型或者简单的EPIC模型。为了验证该模型的模拟效果,采用国外公开的数据集,对本模型进行了校验,并将本模型的模拟结果与国外的14个系统模型的模拟结果进行了对比,发现本模型的综合表现在所有模型中处于前三位。将PEST(Parameter ESTimation)参数自动优化程序与WHCNS模型进行了完全耦合,实现了土壤水力学参数、氮素转化参数和作物遗传参数的自动寻优,也可进行灵敏度分析,从而大大节约了模型校验时间。模型参数敏感度分析结果表明,作物参数的敏感度最高(其中生长发育积温和最大比叶面积最敏感),其次是土壤水力学参数(其中饱和含水率最敏感),而氮素转化参数最低。全局敏感度分析结果与PEST参数敏感度分析结果类似,但研究发现作物水氮胁迫会影响模型参数的敏感度和参数间的交互作用,水氮胁迫越大,参数对硝酸盐淋失的敏感度越小,但参数间交互作用表现更强烈。应用内蒙古阿拉善荒漠绿洲地区砂质土壤春玉米的田间系统观测数据对WHCNS模型进行了校验,结果表明该模型能够很好地模拟高浓度硝酸盐地下水灌溉条件下的硝酸盐淋失和春玉米生长过程。对不同水肥组合情景下的水分动态、氮素去向和作物产量进行了模拟分析,基于作物高产、水肥资源高效和硝酸盐淋失最少的多目标,筛选了适合当地的最优水肥方案。结果表明,当保持灌水5次,每次灌水约105 mmm时能达到较高产量同时大大减少了硝态氮的淋洗。为了能够模拟水稻覆膜旱作复杂条件下的水热运移过程,对WHCNS模型的土壤水热运移模块进行了改进,并应用在我国湖北丘陵区的水稻覆膜旱作试验数据,对改进的模型进行了校验,并且与原模型的模拟结果进行了对比。结果表明,改进后的模型较好地模拟了覆膜条件下土壤热传导、水分运动和作物生长过程。模型大大提高了水稻生育前期的生物学指标的模拟精度。并且发现,当根层土壤水分保持在田间持水量80%的水分管理结合施用化肥75 kg N hm-2并配合有机肥料75 kg N hm-2的措施不仅产量最高,而且显著提高水分利用效率,是水稻覆膜早作体系值得推广的一种水肥管理模式。在模型发展方面,将DRAINMOD模型的排水模块与WHCNS模型进行了耦合,提高了WHCNS模型模拟暗管排水条件下农田的水分运动、氮素去向和作物生长过程的能力。应用国外长期的农田暗管排水试验数据对该模型进行了校验。结果表明,耦合的模型较好地模拟了土壤水储量、作物干物质重、作物产量、作物吸氮量、暗管排水量和氮损失量,且暗管排水和氮素损失量的模拟精度随时间尺度(日、月、年)增加而提高。情景分析表明,当玉米季的施肥量控制在100～120 kg N hm-2的范围内时,可将暗管排出的硝酸盐浓度控制在10 mg L-1以下,同时可维持现有的玉米产量。
[Abstract]:For a long time, the excessive increase of grain production in China relies heavily on water and fertilizer resources, which not only increases the cost of grain production, but also increases the risk of environmental pollution. Therefore, it describes the dynamics of soil moisture in the farmland ecosystem, the process of nitrogen removal and crop growth, the efficient utilization of water and nitrogen resources, the decision of crop production and the environmental protection of ten. Based on the theory and method of soil water solute transport, carbon and nitrogen cycle and crop model, a coupling model of soil crop system water carbon and nitrogen process (soil water heat carbon and nitrogen simulation), which is suitable for China's climate and environmental conditions and agricultural management, is built on the basis of the domestic and foreign soil water solute transport, carbon nitrogen cycle and crop model theory, and the application of WHCNS (water heat carbon and nitrogen simulation) is applied. The field data test the applicability of the model in the highly intensive farmland production system in China and optimize the current management measures of water and fertilizer. The main conclusions are as follows: the constructed WHCNS model takes the days as the step, and the soil water infiltration and redistribution process is described by the Green-Ampt model and the Richard's equation respectively. The migration uses the convection diffusion equation to describe the process of nitrogen cycling in the source sink term (organic matter mineralization, urea hydrolysis, ammonia volatilization, nitrification, denitrification and crop absorption). The organic matter turnover module is directly derived from the Daisy model. The crop model can choose the complex PS123 model or the simple EPIC model. The simulation results are checked by foreign data sets, and the simulation results of the model are compared with the simulation results of the 14 system models abroad. It is found that the comprehensive performance of this model is in the first three bits in all models. The PEST (Parameter ESTimation) parameter optimization program and the WHCNS model are added into the model. Fully coupled, the soil hydraulics parameters, nitrogen transformation parameters and crop genetic parameters were automatically optimized, and the sensitivity analysis could be carried out. The model calibration time was greatly saved. The sensitivity analysis of model parameters showed that the sensitivity of crop parameters was the highest (among which the growth temperature and the maximum specific leaf area were the most sensitive). The second is the soil hydraulics parameters (the saturated water content is most sensitive), and the nitrogen conversion parameter is the lowest. The global sensitivity analysis results are similar to the PEST parameter sensitivity analysis results. However, the study found that water and nitrogen stress of crops will affect the sensitivity of model parameters and intercross interaction between parameters, the greater the water and nitrogen stress, the parameters of nitrate leaching are lost. The smaller the sensitivity is, the interaction between the parameters is more intense. The field system observation data of the sandy soil spring maize in Alashan desert oasis, Inner Mongolia, is used to verify the WHCNS model. The results show that the model can well simulate the nitrate leaching and the growth of spring maize under the condition of high concentration nitrate groundwater irrigation. Process. The water dynamics, nitrogen direction and crop yield under different water and fertilizer combinations were simulated. Based on the multi target of high yield of crops, high efficiency of water and fertilizer and the least leaching of nitrate, the optimum water and fertilizer scheme suitable for the local area was screened. The results showed that the high yield could be reached when irrigation was kept 5 times and the irrigation was about 105 MMM each time. At the same time, the leaching of nitrate nitrogen was greatly reduced. In order to simulate the water and heat migration process under the complex condition of rice mulching, the Soil Hydrothermal transport module of the WHCNS model was improved and applied to the rice mulching experiment data of rice mulching in the hilly area of Hubei. The improved model was verified and the model was simulated with the original model. The results were compared. The results showed that the improved model well simulated the soil heat conduction, water movement and crop growth process under the condition of film mulching. The model greatly improved the simulation precision of the biological indexes of the early growth of rice. And it was found that the water management combined application of soil moisture in the root layer was 80% in the field water holding capacity. The chemical fertilizer 75 kg N hm-2 and the organic fertilizer 75 kg N hm-2 not only have the highest yield, but also significantly improve the water use efficiency. It is a water and fertilizer management model which is worth popularizing in the early rice mulching system of rice. In the development of the model, the drainage module of the DRAINMOD model is coupled with the WHCNS mould, and the WHCNS model is improved. The water movement of farmland, the removal of nitrogen and the ability of the crop growth process under the condition of drainage. The model was verified by a long period of foreign field dark pipe drainage test data. The results showed that the coupled model well simulated the soil water reserves, crop dry matter weight, crop yield, crop nitrogen uptake, dark pipe drainage and nitrogen loss. The simulation accuracy of the drainage and nitrogen loss is increased with the time scale (day, month, year). The scenario analysis shows that the nitrate concentration in the dark tube can be controlled below 10 mg L-1 when the fertilizer amount of the corn season is controlled in the range of 100~120 kg N hm-2, and the existing corn yield can be maintained at the same time.
【学位授予单位】：中国农业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S154.4

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