内蒙古河套灌区春玉米作物系数试验研究

Experimental Study on Crop Coefficient of Spring Maize in Hetao Irrigation District of Inner Mongolia

作物系数曲线是估算作物生长季耗水量变化的重要参数。基于2013年4 9月内蒙古巴彦淖尔市临河区田间水分试验和1994—2013年气象站观测资料,利用水量平衡法反求春玉米作物系数,分析生长季内的变化规律,建立动态模拟方程,并与联合国粮农组织(FAO)分段直线法结果进行比较,提出胁迫条件下作物系数的叶面积修正方法。结果表明:玉米作物系数随发育进程可用三项式曲线描述,变化趋势与产量水平无关,但随产量增高而变幅增大;以出苗后相对积温为时间变量建立模拟方程效果较好,决定系数(R^2)均在0.92以上;模拟计算出各站点最大(1.30~1.48)和平均(0.831~0.919)作物系数,与FAO分段直线法计算的典型值和区间值基本一致,生长中期平均相对误差为3.4%~7.2%;提出利用相对叶面积指数修正作物系数的计算方法;通过2014年实例检验,土壤水分模拟值与实测值的平均相对误差为6.3%,相对误差小于15%的占95.8%。

The crop coefficient curve is an important parameter for estimating the change of water consumption in growing season,and it plays an important role in water management,such as the simulation of evapotranspiration,irrigation forecasting and irrigation decision-making.Previous crop coefficient studies mainly concentrate on the average value of growth period,while rarely focus on daily changes.A crop coefficient simulation method is in need to improve spring maze irrigation forecasting business in Hetao area.Based on the field moisture test data and meteorological station historical observations,the crop coefficient of spring maize is calculated with water balance method,and a dynamic simulation equation is established considering the variation during growing season.It＇s then evaluated using results of the United Nations Food and Agriculture Organization（FAO） piecewise linear method,and daily rolling estimation of crop evapotranspiration is achieved.At the same time,the leaf area correction method is put forward to estimate the soil moisture content under the water stress,which can provide basis for the development of maize irrigation forecast.Results show that the crop coefficient of spring maize can be described by three curves of the development process,and the change trend of crop coefficient has nothing to do with the output level,but the variation range increases with the increase of output.Considering heat index can reduce the influence of geographical factors on crop coefficient,the simulation equation of maize coefficient are established based on relative accumulative temperature as time variable after emergence,and the decision coefficient are all above 0.92.The maximum（1.30—1.48） and average（0.831 — 0.919） maize coefficients of each site are calculated by simulation,results are basically the same as the 3 typical values and interval values got by FAO segmentation method,and the range of averaged relative error during growth period is 3.4%—7.2%.Through the analysis,it is concluded that K_c and relative leaf area index are better described by exponential function,and the calculation method of the standard leaf area index is proposed,which can calculate the crop coefficient in any production condition.The simulated soil moisture is consistent with the measured value with average relative error of 6.3%,and less than 15%for 95.8%circumstance,indicating good application prospects.As the soil moisture supply below 1 m is not considered yet,the model should be improved in the future to explore the calculation method of the lower layer water supply.