Evapotranspiration characteristics of mulched drip-irrigated sunflower farmland in arid region

Mulched drip-irrigation is a burgeoning water-saving irrigation mode in the arid region of Northwest China. It is of great significance to understand and optimize mulched drip irrigation in arid region by analyzing the characteristics of evapotranspiration in mulched drip-irrigated farmland and comparing it with ordinarily irrigated farmland. Using the oasis sunflower farmland in the Sangong River basin on the northern slope of the Tianshan Mountain in Xinjiang as the study area, the farmland evapotranspiration characteristics during the sunflower growth period in 2016 were analyzed using the Bowen ratio-energy balance method, geographical detector, and path analysis method. Furthermore, these characteristics were compared to those of ordinarily irrigated farmlands. The results showed that:1) for mulched drip-irrigated farmland, the average daily evapotranspiration was highest at the flowering stage, followed by the maturity stage, and lowest in the seedling stage. With the growth of crops, the correlation between net radiative flux and daily evapotranspiration gradually decreased. The change trends of average daily evapotranspiration were the same as those of ordinarily irrigated farmland, whereas the average daily evapotranspiration of mulched drip-irrigated farmland was lower than that of ordinarily irrigated farmland at each stage. 2) Regarding the intraday flux in mulched drip-irrigated farmland, the net radiative flux peak was highest at the flowering stage, followed by that at the mature stage, and the minimum appeared at the seedling stage. In terms of turbulent flux, the latent heat flux was equivalent to the sensible heat flux at the seedling stage. Post the flowering period, the latent heat flux was significantly higher than the sensible heat flux, and this characteristic was the opposite at the mature stage. For the ordinarily irrigated farmland, the latent heat flux was higher than the sensible heat flux in all three crop growth stages. 3) The relationship between evapotranspiration and meteorological factors calculated by path analysis showed that temperature, humidity, and wind speed were the dominant factors influencing evapotranspiration. The lower limit of humidity determined the minimum evapotranspiration. The upper limit of wind speed and temperature determined the maximum evapotranspiration. The influence of wind direction was not significant on evapotranspiration. Sunflower farmland using mulched drip-irrigation has unique evapotranspiration features compared with ordinarily irrigated farmland, the amount of water saving exceeds 300 mm during the entire growth period.