基于大型蒸渗仪和遗传算法的受旱玉米蒸发蒸腾量估算

Estimation of Maize Evapotranspiration under Drought Stress Based on Large-scale Lysimeter and Genetic Algorithm

受旱胁迫下作物蒸发蒸腾量估算重要且复杂,依托新马桥农水综合试验站6台大型称重式蒸渗仪开展玉米受旱胁迫专项试验,对不同受旱胁迫下玉米蒸发蒸腾量特征进行分析,在双作物系数法估算无受旱胁迫下玉米蒸发蒸腾量的基础上,采用遗传算法优化率定基础作物系数Kcbini、Kcbmid、Kcbend和作物系数上限Kcmax,同时基于试验站实测太阳辐射数据采用遗传算法优化率定了Angstrom公式经验参数a、b,进而优化了参考作物蒸发蒸腾量(ET0)的计算结果,并以此基础运用双作物系数法估算受旱胁迫下玉米蒸发蒸腾量。结果表明:营养生长中前期轻微的水分亏缺可能会刺激玉米适应性机能,复水后各项生理功能恢复正常;水分亏缺加重时不仅会使玉米当期的蒸发蒸腾量减少,而且会产生累积效应,将这种胁迫影响传递到之后的生育阶段;相同受旱胁迫强度对玉米生殖生长阶段影响更为明显,且易造成永久胁迫;Kcbini、Kcbmid、Kcbend、Kcmax的率定结果分别为0.150、1.090、0.152和1.400,在此基础上运用双作物系数法估算无受旱胁迫下玉米全生育期蒸发蒸腾量的均方根误差RMSE和平均绝对误差MAE分别为1.39 mm和0.97 mm,比对应的FAO-56推荐值估算结果小6.74%和8.23%,受旱胁迫下玉米计算的2个处理全生育期RMSE、MAE和MRE均值分别为1.60 mm、1.18 mm和6.73%,整体估算效果虽然没有无受旱胁迫下的好,但仍优于FAO-56推荐值的估算结果。因此,基于双作物系数法和遗传算法的受旱胁迫下玉米蒸发蒸腾量估算合理可靠,该研究可为区域制定适宜灌溉制度和降低农业旱灾损失风险提供理论依据。

Due to the importance and complexity of crop evapotranspiration estimation under drought stress,maize drought stress special experiment was conducted based on six large-scale weighing lysimeters at Xinmaqiao Irrigation Experimental Station,the empirical parameters a and b of the Angstrom formula were optimized based on the measured solar radiation data from the experimental station,and the calculation results of the reference crop evapotranspiration were optimized,and then the characteristics of maize evapotranspiration under different drought stress scenarios were analyzed,moreover the maize evapotranspiration under drought stress was estimated by using basic crop coefficients,including K cb ini,K cb mid,and K cb end and upper limit of crop coefficient K c max,which were calibrated by genetic algorithm in the process of estimating maize evapotranspiration under no drought stress based on dual crop coefficient approach.The results showed that early mild water deficit may stimulate the adaptability function of maize,and normal physiological function of that would return after re-watering;water deficit would not only decrease current evapotranspiration of maize,but also generate the cumulative effect,which transferred stress influence to later growth stages;the same drought stress intensity had a more obvious effect on the reproductive growth stage of maize,and it may cause permanent stress;the calibration results of K cb ini,K cb mid,K cb end and K c max were 0.150,1.090,0.152 and 1.400,respectively,and the root mean square error(RMSE)and mean absolute error(MAE)of estimated evapotranspiration results under no drought stress in whole growth period using these crop coefficients were 1.39 mm and 0.97 mm,respectively,which were 6.74%and 8.23%less than those of estimated results based on FAO 56 recommended approach,the means of RMSE,MAE and MRE of estimated evapotranspiration results under two different drought stress scenarios were 1.60 mm,1.18 mm and 6.73%,respectively.Therefore,the estimation of maize evapotranspiration under drought stress based on dual crop coefficient approach and genetic algorithm were reasonable and reliable,and this research would provide theoretical foundation for formulating suitable irrigation system and reducing risk of agricultural drought loss.