Abstract
Crop coefficient (Kc) 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 Kc in tea plantation ecosystems. This study explored and determined the actual evapotranspiration (ETc) and Kc 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 Kc and adjusted Kc. The results showed that the adjusted ETc and Kc values revealed a minor fluctuation when compared to the ETc and Kc values during the experimental period, which indicated that the adjusted ETc and Kc values were more precise and practical to field conditions. The average adjusted Kc 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 Kc values, possibly due to the lower level of LAI after pruning. Moreover, it is clearly manifested that BY1 consistently had lower ETc and Kc values than those of LJ43 because of plant growth status differences between BY1 and LJ43. Overall, our study proposed a reliable reference of Kc in tea plantation, and illuminated the effects of pruning and plant growth differences on Kc, which could provide a strong basis for precise irrigation in tea plantations in a subtropical climate.
Highlights
The total annual rainfall amount in 2019 was 1565 mm, 42% of which was evenly distributed during February to June, but more frequent and extreme rainfall events happened during July to December
Given that the runoff amount could not be estimated in our study, and considering that runoff only occurs in heavy rainfall situations, a linear plus platform model was applied to determine the relationship between cumulative rainfall and drainage, and the critical amount of rainfall was successfully estimated in our study
The linear plus platform model was applied to analyze the relationship between cumulative rainfall and lysimeter drainage, and critical cumulative rainfall values (78.02 mm for BY1 and 90.98 mm for LJ43) were obtained to estimate ETc and Kc via the water balance equation when the cumulative rainfall was more than the critical value
Summary
To meet the water demand of tea tree growth, the temporal distribution of rainfall over the year is more vital [2,3,4]. Droughts usually cause irreparable yield losses, as well as prematurely aged tea plants [5,6,7,8,9], while heavy rainfall, on the other hand, can cause water logging, runoff, topsoil erosion, and deep percolation of critical soil nutrients [10]. In subtropical regions of China, where most tea plants are cultivated, the monthly rainfall always unevenly distributes, with frequent droughts in autumn and excessive rainfall in summer [11]. Irrigation, as a countermeasure to the droughts, is of great importance to tea plant growth
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