太行山前平原40年冬小麦作物系数变化及影响因素研究

Changes in and influencing factors of crop coefficient of winter wheat during the past 40 years on the Taihang Piedmont Plain

作物系数是计算作物需水量的基本参数,准确确定作物系数在优化灌溉管理方面有重要作用。作物系数随作物生长及环境条件发生变化,研究作物系数如何受生产条件和气象条件变化的影响,可为准确确定作物系数提供依据。本研究基于中国科学院栾城农业生态系统试验站1980—2020年40余年间冬小麦在充分灌溉条件下的实际蒸散量,研究冬小麦作物系数的变化规律;并利用最近3年的试验数据,明确现代生产水平下影响冬小麦作物系数的主导因素。结果表明,1980—2020年间冬小麦在充分供水条件下的实际蒸散量及参考作物蒸散量多年平均值分别为434.7 mm和550.8 mm,参考作物蒸散量年际相对稳定,冬小麦实际蒸散量增加17.6%。作物系数多年平均值为0.80,其中1980—1990年、1991—2000年、2001—2010年和2011—2020年平均分别为0.76、0.80、0.81和0.84;40年间冬小麦产量增加42.4%,作物系数增加11.6%,作物产量提升是作物系数升高的主要原因。本研究表明在现状生产条件下,叶面积指数、生物量是影响作物系数的重要因素,在叶面积指数较高的情况下作物系数主要受饱和水汽压差及环境温度的影响,2017—2020年冬小麦3个生育期作物系数分别是0.79、0.86和0.79;生育期蒸散量均值为442.3 mm,主要生育期3年平均作物系数分别为播种—越冬前0.70、越冬期间0.42、返青—拔节期0.76、拔节—抽穗期1.18、抽穗—灌浆期1.39、成熟期0.96。本研究结果显示作物系数并不是稳定不变的,而是受作物生产力和大气蒸散力的影响。因此,在利用作物系数和参考作物蒸散量评价作物需水量时,需要综合考虑上述因素。

The crop coefficient(Kc)is defined as actual evapotranspiration(ET)under sufficient water supply divided by the reference crop ET(ET0),which can be calculated using meteorological factors.The Kc is used as a basic parameter to calculate the crop water requirements.The accurate determination of Kc plays an important role in optimizing irrigation management.The Kc changes with crop growth and environmental conditions.The purpose of this study was to assess how Kc varied with crop production and weather conditions by using a long-term field experiment of field management measures of winter wheat.The actual ET of winter wheat under sufficient irrigation and ET0 derived from daily meteorological parameters at Luancheng Agro-ecosystem Experimental Station of the Chinese Academy of Sciences from 1980 to 2020 were used to calculate the seasonal Kc.Additionally,the dominant factors affecting the Kc of winter wheat under the current production conditions were identified from experimental data of three recent years(2017–2020).The results showed that for winter wheat with sufficient water supply from 1980 to 2020,the average ET and ET0 were 434.7 mm and 550.8 mm,respectively.The ET0 was relatively stable,and the ET increased by 17.6%.The average Kc was 0.80 during the past four decades,with an average value of 0.76 in 1980–1990,0.80 in 1991–2000,0.81 in 2001–2010,and 0.84 in 2011–2020,indicating a continuously increasing trend.In the past four decades,the yield of winter wheat had increased by 42.4%,and Kc had increased by 11.6%.The increase in ET was the main reason for the increase in Kc.The ET during the past four decades increased with increasing crop production,and with a relatively stable ET0,the Kc increased.Therefore,the Kc varied with changes in crop grain production,which was related to biomass production and canopy size.Under the current growing conditions,leaf area index and biomass were important factors that affected Kc.When the leaf area index reached a certain level,Kc was mainly affected by the atmospheric evaporation potential determined by the saturated water vapor pressure difference and atmospheric temperature.The Kc during the recent three years was 0.79 for 2017–2018,0.86 for 2018–2019,and 0.79 for 2019–2020.The average ET was 442.3 mm during the three years,and the average Kc at different growing stages of winter wheat were 0.70 from sowing to winter dormancy,0.42 during winter dormancy,0.76 from recovery to jointing,1.18 from jointing to heading,1.39 during heading to grainfill,and 0.96 during maturity.Thus,the water requirements for winter wheat after winter dormancy increased sharply and reached the highest values during the heading to earlier grain-filling stages.The results from this study indicate that Kc varies with changes in the crop growing conditions and should not be taken as a constant value.Kc developed during three recent seasons in this study could be used to determine the crop water requirements for irrigation scheduling under the current growing conditions.