考虑残留氮对非稳定流场硝态氮淋失贡献的传递函数模型 Ⅱ.农田应用

Transfer function model to simulate nitrate leaching in soil from applied and indigenous nitrate under transient water flow Ⅱ. field application

应用田间冬小麦-夏玉米生长条件下土壤硝态氮淋失动态的试验资料,对所提出的可估计表施和残留氮对土壤非稳定流场中硝态氮淋失贡献的传递函数模型进行了检验。首先,对所选定的农田中的两个土壤剖面,估算了硝态氮和氯离子的中值与均值迁移时间,然后,利用我们的模型,使用其中一个土壤剖面标定硝态氮和氯离子运移的概率密度函数的参数,接着,应用标定后的传递函数模型,模拟了另一个土壤剖面的硝态氮淋失浓度和累积淋失量动态,并分别估算了表施和残留氮占硝态氮总淋失量的分数。结果表明:提出的传递函数模型在农田条件下对土壤硝态氮累积淋失量模拟的相对误差为14 89%。

Transfer function model(TFM) proposed by Jury(1990), which could be used to simulate the flux concentration of conservative solute under transient water flow, was improved by introducing a corrector of probability density function and was used to distinguish the nitrate leaching from applied N and soil residual nitrate. The modified TFM was tested on a field experiment, which was conducted under the growing condition of winter wheat and summer maize. Firstly, the mean travel time and the median travel time in two specified sites were estimated. Secondly, the parameters of travel distance pdf of NO-3-N and Cl- were calibrated under steady state water flow, and the calibrated parameters were used to simulate dynamics of nitrate flux concentration and cumulative leaching amount in the other profile, in which soil water movement was regarded as transient water flow. The leaching fraction of applied N of total applied fertilizer N and that of total leaching amount were modeled, and it was shown that these two fractions were too small and most of the leaching nitrate was soil residual nitrate. Good agreement between simulated and measured data was obtained, and the relative error of simulated cumulative leached quantity of nitrate was 1489%.