科尔沁沙地青贮玉米蒸散量的估算与分析

Estimate and analysis of silage maize evapotranspiration in Horqin Sandy Land

为准确估算科尔沁沙地青贮玉米实际蒸散量的变化规律,选用ASCE Penman-Monteith(ASCE-PM)模型计算参考作物蒸散发(ET0);利用双作物系数模型模拟土壤含水率与对应实测值进行统计分析,根据均方根误差、一致性指数、平均绝对误差和Nash-Sutcliffe效率指数4个指标以及回归系数和决定性系数对双作物系数模型进行率定和验证,然后模拟青贮玉米的作物系数,与ASCE-PM模型结合后模拟青贮玉米的蒸散发、棵间土壤蒸发和作物蒸腾规律,并分析其影响因素。结果表明:双作物系数模型准确地模拟土壤含水率和棵间土壤蒸发的变化过程,率定各阶段基础作物系数为0.25、0.9和0.5。棵间土壤蒸发先由播种时峰值下降到较低水平,于收割前有所回升;蒸腾速率除刚出苗和收割前呈单峰变化外大部分时段呈双峰变化,日内变化规律大体为中午高,早晚低,自出苗之日起生长中期后半段处于较高水平,之后逐渐减弱。青贮玉米蒸散量与太阳辐射线性关系最为显著(R=0.643),与气温、空气湿度和风速的相关性依次次之。ASCE-PM模型空气动力项5 d尺度贡献率为27.94%~77.66%,且随风速同增减。综上所述,ASCE-PM模型结合双作物系数可较好估算科尔沁沙地青贮玉米的实际蒸散量,以及棵间土壤蒸发和作物蒸腾量。

This study aimed to accurately estimate the evapotranspiration of silage maize in Horqin sandy land.In this paper,ASCE Penman-Monteith（ ASCE-PM） models was used to estimate the reference evapotranspiration（ ET0）,and we compared the simulated soil moisture content by SIMdual_K_c model and the corresponding measured values. The root-mean-square-error（ RMSE）,consistency index（ d）,average absolute error（ AAE）,Nash-Sutcliffe efficiency index（ E） were chosen as three evaluation indicators combining the regression coefficient（ b） and the decisive coefficient（ R2） to rate and verify SIMdual_K_c model,and then simulated silage maize crop factor crop,simulating evapotranspirationof silage maize,soil evaporation and crop transpiration combined with ASCE-PM model and analyzed their influencing factors. The results illustrated that SIMdual_K_c model accurately simulated the soil water content and the soil evaporation change,and the basic crop coefficients were 0. 25,0. 9 and 0. 5 respectively at each stage. During the growing season,the soil evaporation decreased from the peak value to the lower level before sowing,and recovered before harvest; the transpiration rate was bimodal at most of the time except for emergence and harvest,and the law of daily variation was generally high and low at noon. Transpiration rate from the date of emergence to the second half of the growing medium term was in a high level,then gradually weakened. The linear relationship between the actual evapotranspiration of silage maize and the solar radiation was significant（ R = 0. 643）,the correlation with the actual evapotranspiration of silage maize was from high tolow,followed by temperature,air humidity and wind speed. The contribution rate of aerodynamics 5 d scale of ASCE-PM model was 27. 94% - 77. 66%,and the contribution rate of model aerodynamic items increased and decreased with wind speed. In conclusion,the ASCE-PM model combined with the double-crop coefficient could estimate the actual evapotranspiration of silage maize and the soil evaporation and silage maize transpiration in Horqin sandy.