| The application of drip irrigation under film mulching can effectively improve crop yield and water use efficiency.Since fields with border irrigation,furrow irrigation and other traditional irrigation are replaced with drip irrigation under film mulching,various physical characteristics of the surface such as reflectance,absorption,emissivity and roughness are changed which can affect the energy distribution and water cycle of farmland.In this study,Bowen ratio energy balance method was used to study the water and heat fluxes transfer variation and evapotranspiration simulation in drip irrigated sweet potato field with film mulching in Shandong.The main results are as follows:(1)The applicability of Bowen ratio energy balance method for drip irrigated sweet potato field with film mulching was verified in Shandong.The R2,MAE,RMSE and IA of evaportranspiration between the Bowen ratio energy balance method and the water balance method in two years were 0.79,0.34 mm/d,0.67 mm/d and 0.92,respectively,which indicated the accuracy of the data measured by the Bowen ratio system was high and the Bowen ratio method could be applied to the study of water and heat fluxes in drip irrigated sweet potato field with film mulching in Shandong.(2)The water and heat fluxex transfer law and its response to environmental factors in the drip irrigated sweet potato filed with film mulching were analyzed.The diurnal variation of water and heat fluxex during the entire growth period of drip irrigated sweet potato filed with film mulching showed a single peak curve characteristic of high fluxes at daytime and low fiuxes at nighttime.The latent heat showed a trend of increasing first and then decreasing throughout the entire growth period,while the sensible heat flux showed a trend of decreasing first and then gradually increasing.In 2021,latent heat flux were sensible heat flux and soil heat flux accounted for 69.12%,25.14%,and 6.57%of the energy expenditure during the whole reproductive period,respectively,while in 2022,they were 60.89%,27.39%and 11.90%,respectively.After rainfall and irrigation,the latent heat flux of drip irrigated sweet potato filed with film mulching would increase significantly,the impact of rainfall was greater than that of irrigation and the impact of rainfall was greater in the early growth stage of fertility than in the late growth stage of fertility.(3)The simulation of evapotranspiration in drip irrigated sweet potato filed with film mulching was explored considering the R2,MAE,RMSE and IA,the SW model could best reflect the change pattern of evapotranspiration,followed by the double crop coefficient method and finally the single crop coefficient method.The R2,MAE,RMSE,and IA between the evapotranspiration estimated by the SW model and the Bowen ratio energy balance method were 0.79,0.29mm/d,0.69mm/d,and 0.92 in 2021,and 0.77,0.26mm/d,0.67mm/d,and 0.93 in 2022,respectively.(4)The R2,MAE,RMSE and IA of soil evaporation between the micro evapotranspirator and SW model were 0.67,0.09 mm/d,0.12mm/d and 0.82 in 2021,and 0.64,0.03 mm/d,0.08 mm/d and 0.82 in 2022,respectively.The SW model could be used to estimate E and T separately for drip irrigated sweet potato filed with mulching in Shandong.(5)Compare with Bowen ratio energy balance method,the SW model underestimated the evapotranspiration by 8.66%and 8.54%,the single crop coefficient method by 3.66%and 7.98%,and the double crop coefficient method overestimated the evapotranspiration by 7.43%and 10.37%in 2021 and 2022,respectively.(6)The mean value of the base coefficient(Kcb)of drip irrigated sweet potato field with film mulching showed an increase before decreasing with values of 0.15,1.07 and 0.45 in the early,middle and late growth stages,respectively.The mean value of the soil evaporation coefficient(Ke)showed a decrease before increasing with values of 0.33,0.10 and 0.28 in the early,middle and late growth stages,respectively. |
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