Evaluating the irrigation schedules of greenhouse tomato by simulating soil water balance under drip irrigation.

Irrigation management has become a critical concern in the face of increasing water scarcity and food demand, particularly in the arid and semi-arid regions of the world. However, the effects of climate and soil texture on irrigation schedules remain unclear. In the present study, a two-year trial (2019–2020) was conducted in three greenhouses with different climates and soil textures under drip irrigation. The irrigation schedules were based on the cumulative evaporation (CE) of a 20 cm pan. Three treatments with different amounts of irrigation (I) were set in 2019. Three irrigation frequencies (IF) in combination with three irrigation amounts were set in 2020. A numerical model (HYDRUS-2D) was applied to simulate the soil water balance of greenhouse tomatoes. Tomato yield and irrigation water use efficiency (IWUE) were measured, and the responses of photosynthetic indices to soil water availability (SWA) were quantified. The results indicated that the soil water content (SWC) simulated by HYDRUS-2D was in accordance with the observed data, with average root mean square error (RMSE), mean bias error (MBE), and index agreement (IA) reaching 0.0127 cm3 cm−3, −0.0010 cm3 cm−3, and 0.9275, respectively. Among the four photosynthetic indices, the normalized photosynthetic rate exhibited the highest degree of fit (R2 =0.9678) with SWA (0–20 cm). Increased irrigation frequency (high IF) reduced the deep drainage by 24.6%, 10.5%, and 3.0% in sandy loam, loam, and silty clay soils, respectively. It was concluded that frequent irrigation with low amount can be applied to sandy loamy soil, whereas a lower irrigation frequency and larger single irrigation amount are recommended for silty clay soil. Our study provides theoretical support for irrigation management in semiarid regions with similar climates and soil textures. • HYDRUS-2D was used to simulate soil water dynamics in greenhouse tomato under drip irrigation. • The response of photosynthetic indices to simulated soil water availability in different soil layers was quantified. • Frequent irrigation lowered deep drainage and lateral diffusion, while maintaining higher soil water availability. • Higher frequent irrigation with smaller single amounts were recommended for sandy loam soil than that in silty clay. [ABSTRACT FROM AUTHOR]