Estimation of Evapotranspiration and Crop Coefficient of Rain-Fed Tea Plants under a Subtropical Climate

Crop coefficient (K-c) is one of the most significant parameters for crop water demand prediction and irrigation scheduling. However, there is a lack of knowledge about water vapor and K-c in tea plantation ecosystems. This study explored and determined the actual evapotranspiration (ETc) and K-c of two cultivars of tea (Camellia sinensis), clone variety Baiye1 (BY1) and Longjing43 (LJ43), based on lysimeter data. An estimation was made for both for ETc and adjusted ETc, and the corresponding K-c and adjusted K-c. The results showed that the adjusted ETc and K-c values revealed a minor fluctuation when compared to the ETc and K-c values during the experimental period, which indicated that the adjusted ETc and K-c values were more precise and practical to field conditions. The average adjusted K-c values were 0.71 (range of 0.43-1.02) for BY1 and 0.84 (range of 0.48-1.22) for LJ43. Additionally, heavy pruning can decrease ETc and K-c values, possibly due to the lower level of LAI after pruning. Moreover, it is clearly manifested that BY1 consistently had lower ETc and K-c values than those of LJ43 because of plant growth status differences between BY1 and LJ43. Overall, our study proposed a reliable reference of K-c in tea plantation, and illuminated the effects of pruning and plant growth differences on K-c, which could provide a strong basis for precise irrigation in tea plantations in a subtropical climate.