Jensen模型敏感指数出现负值的原因及解决方法

Reasons and Solutions of Negative Values of Sensitive Indexes of Jensen’s Model

对于作物水分生产函数的Jensen模型 ,其敏感指数出现负值的现象是不合理的。从模型的适用范围和其敏感指数估计值的随机波动性两个方面分析了敏感指数出现负值的原因 ,并提出了解决方法 :(1)利用适用范围内的数据来建立Jensen模型 ;(2 )作物生育阶段不宜划分过多 ,一般以 4～ 6个为宜 ;(3)试验处理数可在 9～ 14范围内确定 ;(4 )合理设计试验方案 ,尽量使信息矩阵的行列式值取最大 ;(5 )通过选择土壤空间变异性较小的地块作为试验小区 ,提高灌水均匀度 。

It is not reasonable that sensitive indexes of Jensen’s mode as the crop-water production function are negative.The reasons of negative values of Jensen's model were studied in two aspeccts,the application field and the randomicity.The solutions should be:(1) data used to establish the model must be in the application field of Jensen's model; (2) it is feasible that the number of growth stages of crop is restricted to 4～6; (3) it is suggested that the number of the experiment treatments is 9～14; (4) the experiment scheme should be reasonable, that is, the determinant value of the information matrix must be as large as possible; (5)the experiment precision should be increased through selecting uniform experiment area, improving irrigation uniformity and increasing observation sites.