Evapotranspiration dynamics and their environmental drivers in a rainfed rice-wheat cropping system of a hilly region...

Agriculture in hilly regions holds significant potential but is often undervalued in the context of food production due to the distinct terrain, microclimate, and subsistence farming practices. This study explores long-term water and energy fluxes across the years 2017-2021, over a rainfed rice-wheat system using the eddy covariance technique to evaluate evapotranspiration (ET) dynamics. Seasonal variation in ET during rice and wheat growing seasons closely follows the daily magnitude of available net energy, relative canopy cover and the supply of soil moisture. The total ET during the rice and wheat growing seasons ranged from 319.39-403.82 mm and 341.81-458.29 mm, respectively, with maximum daily ET values of 7.21 mm day^-1 for rice and 6.79 mm day^-1 for wheat. Path analysis was used to examine the direct and indirect effects of environmental and biophysical factors on ET, including net radiation (Rn), air temperature (Tair), vapor pressure deficit (VPD), soil water content (SWC), stomatal conductance (Gs), and leaf area index (LAI). VPD was the dominant driver of ET during the rice season, while both VPD and Rn significantly influenced ET during the wheat season. Gs was also a key factor, with stronger control during the wheat season. Notably, VPD had a negative impact on ET through Gs in both seasons. Overall, this study highlights how ET ET in rainfed rice-wheat systems interacts with environmental and biophysical factors, providing insights into crop-water relations and land-atmosphere interactions.