Site-Specific Evaluation of Canopy Resistance Models for Estimating Evapotranspiration over a Drip-Irrigated Potato Crop in Southern Chile under Water-Limited Conditions

The evapotranspiration (ET) process is an essential component in many agricultural water management systems, and its estimation is even more determinant when crops are grown under waterlimited environments. The traditional canopy resistance (r(c)) approaches were evaluated to simulate potato evapotranspiration (ETcp) using the original Penman-Monteith equation under different irrigation levels. A field study was carried out on a drip-irrigated potato crop (var. Puyehue INIA) located in the Research Center Carillanca (INIA), La Araucania Region, Chile (38 degrees 41' S, 72 degrees 24' W, 188 m above sea level) during the 2018/2019 and 2019/2020 growing seasons. The different irrigation levels were full irrigation (IL1), 75% of IL1 (IL2), and 60% of IL1 (IL3). The soil water content, morphological, physiological, meteorological, and micrometeorological variables were measured to calculate the different r(c) approaches and estimate ET for both growing evaluated seasons. The final values of estimated ETcp were compared to the soil water balance method (ETcpWB). The use of amphistomatous (LA) and hypostomatous (LH) r(c) approaches are the best alternative to estimate the ETcp on potato crops. The best estimation of ET was found for ETcpLA with an overestimation of 0.6% for IL1, 7.0% for IL2, and 13.0% for IL3, while for ETcpLH with underestimations of 12.0, 11.0 and 31.0% for IL1, IL2, and IL3, respectively. The lowest average values of root mean square error (RMSE), mean absolute error (MAE), and index of agreement (d) were observed for ETcpLA in both IL1 and IL2 conditions, with values of 4.4 and 3.2 mm, 3.2 and 2.5 mm, and 0.82 and 0.87, respectively. More investigation is necessary on the plasticity of the morphological features of potato leaves and canopy geometry, as the stomatal water vapor flowing on the canopy surface could be affected, which is a key factor in the canopy resistance model for accurate ET estimation under soil-water-limited conditions.

Automated summary

Evapotranspiration is an important component of agricultural water management systems, especially in water-limited environments. Evaluating different canopy resistance methods, it was found that the amphistomatous and hypostomatous approaches are the best options for estimating potato evapotranspiration. The ETcpLA method provided accurate estimates compared to the soil water balance method for different irrigation levels.