对田间农业节水水平评价方法的探讨

Discussion on method for evaluation of field water-saving level

文中归纳了各种反映农业节水水平的指标体系，分析了各指标之间存在的内在联系，并以数学解析方法，描述了主要指标之间的数学关系式及基本线型。通过推求灌溉水的水分生产率一边际产量关系曲线（Z1曲线）的最大值，确定符合农业节水要求的产量闽值下限和定额闽值下限，即基准产量和参考定额；以Z1曲线为基础，叠加节灌粮食产量～产量期望值关系曲线（Z2曲线）形成Z曲线，通过推求其极值，确定符合农业节水要求的定额阈值上限和产量阈值上限，即基准定额和参考产量。根据这种方法，可以将复杂问题简单化，通过定量计算，对一个区域进行定性节水水平评价。

Various index systems of agricultural water-saving levels are summarized herein; for which an analysis is made on the inherent relations among all the indexes, and then the mathematical relationships with the basic linetypes among the main indexes are described with mathematical analytical method. Through calculating the maximum value of the relationship curve between the water productivity - the marginal yield （ Z1 curve） of irrigation water, both the lower limit of the yield threshold and the lower limit of the quota threshold, i.e. the basic yield and the basic quota, conformed with the requirement of agricultural water-saving are determined. Furthermore, based on the Zl curve, the Z curve is formed by adding the relationship curve of the grain yield from the water saving irrigation - the expected value of the yield （Z2 curve）, thus, the lower limit of the yield threshold and the lower limit of the quota threshold, i.e. the basic quota and the reference yield, conformed with the requirement of agricultural water-saving are determine through the calculation of its extreme value. With this method, the qualitative evaluation on the watersaving level of a region can be made by solving a complicated problem through a simplified way on the basis of the quantitative calculation concerned.