时段划分对冬小麦作物水模型影响的研究

引入逻辑斯蒂函数描述水分敏感指数随时间的变化过程,对Jensen模型(模型一)进行了改进,使得改进后的作物水模型(模型二)的参数固定为4个,避免了模型一参数随时段数增加而增加的缺陷。采用山西水利职业技术学院试验基地2007年和2008年冬小麦田间试验资料,将冬小麦全生育期等间隔地划分为23、21、19、17、……、3共11个时段,利用非线性规划的方法求得了相应的模型参数,进行了比较分析。结果表明,采用模型一时,相对腾发量划分的时段数以5左右为宜,不宜超过7;采用模型二时,则不受时段数的限制;模型二的修正复相关系数Ra随时段数的增加略有增大的趋势,均在0.84以上,F值均在16以上,大于F0.001=12.56,达到极显著水平,能够用于模拟供水对产量的影响;模型二的标准误随时段数的增加上下波动,变化于0.100~0.108之间,小于模型一的标准误,模拟精度高于模型一;采用模型二模拟产量时宜尽量使用较大时段数的参数,且腾发量划分的时段数与参数的时段数应尽可能一致。

Effect of Period Division on Model of Crop Response to Water

Period division effected the application and solution of model of crop response to water significantly.In this paper,a logistic function described the variation of moisture sensitivity index with time was introduced.The model of crop response to water was modified based on the logistic function and Jensen-model(model-1).The modified model(model-2) has four parameters and avoided the parameters increasing with time in model-1.Based on the experiment data obtained in 2007 and 2008,parameters were solved with nonlinear programming by period division(it was 23,21,19,17,…,3) in growing period of winter wheat.The results showed that the number of periods was about 5,and not beyond 7 for model-1.The number of periods was not limited for model-2.The multiple correlation coefficient Ra was increased with the number of periods increasing.The Ra of model-2 was beyond 0.84 and the value of F was beyond 16(F0.001=12.56),indicating that the model-2 performs well in simulating the effect of water supply on production.The value of square-error was fluctuated with the number of periods increasing,and ranged from 0.100 to 0.108,indicating that the simulation accuracy of model-2 was higher than model-1.It was proposed to select parameters of bigger number of period for simulating production in model-2,and the number of period of evapotranspiration and parameters should be as consistent as possible.