中文摘要：

作物系数是计算作物需水量的重要参数。本研究依据2008年野外水分试验资料,利用水量平衡法计算了内蒙古典型草原区的作物系数,分析了其在生长期内的变化规律,建立了典型草原作物系数与返青后年日数和大于0℃积温的模拟方程,可用3次多项式拟合;基于FAO分段直线法确定出作物系数典型值,分别为：初始生长期0.43,生长中期1.02,生长后期0.90,并与推荐值进行了比较;同时,提出了利用LAI修正胁迫条件下典型草原区作物系数的方法。通过模拟计算土壤水分与实测结果基本接近,平均相对误差为6.2%~13.6%。

英文摘要：

Based on data of field water experiments on typical steppe of Inner Mongolia in 2008,a crop coefficient of the typical steppe was calculated from analysis of the water amount balance,and changing regularity during the growing season.Simulation equations of the crop coefficient built with number of days after grass revival in a year and accumulated temperature above 0℃,showed that simulation using a cubic polynomial expression was appropriate and correlation coefficients were all over 0.94.Typical values of crop coefficients were defined with a linear section method of FAO,and they were 0.43 in the initial growing period,1.02 in the medium growing period and 0.90 in the final stage.A method of revising the crop coefficient of typical steppe under stress conditions was put forward with leaf area index（LAI）.The crop coefficient given in this article was suitable for typical steppe in Inner Mongolia,because simulating calculation of soil water was mostly close to the results of actual observations with mean relative simulation errors of 6.2%-13.6%.