中文摘要：

为准确估算和区分黄土高原旱作春玉米蒸散（evapotranspiration,ET）,该文基于实测叶面积指数（leaf area index,LAI）动态估算基础作物系数,利用LAI修正土壤蒸发系数,并基于修正后的双作物系数法估算和区分黄土高原地区旱作春玉米ET,并以2012、2013年寿阳站基于涡度相关系统和微型蒸渗仪实测的春玉米ET和土壤蒸发（soil evaporation）对修正后的双作物系数法的适用性进行评估。结果表明：修正后的双作物系数法能够较为准确的估算春玉米ET,2012年春玉米全生育期ET估算值、实测值分别为365.3、372.6 mm,2013年分别为385.6、369.4 mm;2012年全生育期改进双作物系数法决定系数、均方根误差、模型效率系数和平均绝对误差分别为0.824、0.561 mm/d、0.817和0.449 mm/d,2013分别为0.870、0.381 mm/d、0.871和0.332 mm/d;同时,修正后的双作物系数法可对春玉米各生育期ET进行准确区分,土壤蒸发估算值与实测值有较好的一致性,2012年全生育期估算和实测土壤蒸发分别为0.98和0.99 mm/d,分别占ET的38.12%和37.08%;2013年估算和实测土壤蒸发分别为0.86和0.89 mm/d,分别占ET的33.59%和35.90%。因此,修正后的双作物系数法能够较为准确地估算和区分黄土高原地区旱作春玉米ET。该研究可为黄土高原区农田水分精准管理提供科学指导。

英文摘要：

Evapotranspiration（ET） is vital to energy and water balance in agriculture, and accurate estimation and partition of ET is needed for crop water productivity improvement. In this study, a modified approach of FAO-56 dual coefficients of crop was developed for estimating and partitioning maize ET. Daily basal crop coefficient was dynamically calculated by introducing a canopy cover coefficient which could be simply described as a function of leaf area index（LAI）. Daily evaporation coefficient was also calculated by modified canopy cover that was computed by LAI. A field experiment was conducted from May to September during 2012 and 2013 in a rainfed farmland on the Loess Plateau of North China, and daily spring maize ET and soil evaporation were measured by eddy covariance system and micro-lysimeters to validate the modified approach of dual coefficients of crop. The results indicated that the LAI and the maximum plant height in 2012 were slightly larger than those in 2013, with the LAI ranging from 0 to 4.52 m^2/m^2 in 2012 and from 0 to 3.97 m^2/m^2 in 2013, the maximum plant height of 2.98 m in 2012 and 2.97 m in 2013, respectively. Due to large frequency of wetting by rainfall and small canopy cover in initial stage, daily evaporation coefficient fluctuated significantly; then daily evaporation coefficient decreased with the increase of canopy cover in development and mid stages, and increased in late stage. In contrast to daily evaporation coefficient, the change trend of daily basal crop coefficient was relatively small in initial stage; then daily basal crop coefficient increased with the increase of LAI in development and mid stages, and decreased in late stage. Simulated maize ET values in initial, development, mid, late and whole growing season were 47.0, 81.1, 172.7, 64.6 and 365.3 mm in 2012, and 25.1, 78.5, 211.5, 70.5 and 385.6 mm in 2013, respectively, which were in good agreement with the measured ET, with the coefficient of determination（R^2） of 0.824, root mean square error（RMSE）