Estimating and partitioning maize evapotranspiration as affected by salinity using weighing lysimeters and the SIMDualKc model

Water scarcity and saline stress are primary threats for water use and agricultural production in arid and semi-arid regions, such as the Hetao Irrigation District , China. The current study, using irrigation with saline water , developed through three seasons (2017–2019) of field experimental surveillance of mulched maize water use in two cropped weighing lysimeters . Measurements included crop characteristics (height, LAI, dates of development stages), soil and water salinity , and daily actual crop evapotranspiration (ET c act ). Deficit surface irrigation was scheduled in 2017 and 2018 seasons, while in 2019 drip irrigation was used aimed at satisfying crop water requirements . Both approaches aimed at improving irrigation management while controlling impacts of salinity. The collected information was used to parameterize and calibrate the soil water balance model SIMDualKc. The model uses the FAO56 dual crop coefficient approach and considers the combined effect of water and salinity stresses due to salinity of both soil and irrigation water. Results show that the SIMDualKc model adequately simulates the dynamics of the observed ET c act throughout the three growing seasons. The goodness-of-fit indicators show highly appropriate model fitting of observed ET c act with low RMSE of 0.42 mm d -1 for the calibration and 0.53 mm d -1 for validation. The calibrated standard basal crop coefficients (K cb ) of maize for the initial, mid, and end stages were respectively 0.15, 1.15 and 0.25, which agree with those recently proposed by Pereira et al. (2021). Due to the impacts of both water and salt stress in 2017 and 2018, ET c act was much below the potential value ET c , ranging 64–83%, while in 2019 that percentage increased to 92% due to avoiding water stress by then. The average K cb mid act range 0.58–1.06, therefore lower than K cb mid , with the lower values occuring in the lysimeter that was irrigated with a large deficit. The irrigation scheduling practiced was assessed using water use and productivity indicators, which have shown the advantage in using drip irrigation with small time intervals between irrigations. Moreover, the current study and the calibrated model provide for adopting irrigation management practices that may save water and control salinity. • Weighing lysimeters provide for accurate measurement of evapotranspiration fluxes. • A couple of them were used to follow daily crop ET as affected by soil and water salinity. • Observations were used to calibrate and validate the model SIMDualKc for maize. • Results for deficit basin irrigation show ET and yields decreased by water and salt stress. • When drip irrigation was used without water deficit water productivity increased.