Improved construction and applicability analysis of stomatal conductance model for cotton under drip irrigation in...

Traditional plant stomatal conductance (g_sw) models have limited applicability. An urgent need exists to develop a g_sw model suitable for cotton grown under drip irrigation in Changji, Xinjiang, and to investigate the mechanisms underlying the effects of irrigation variations on leaf g_sw.

This 2-year field study selected three g_sw models (Ball-Woodrow-Berry [BWB], Ball-Berry-Leuning [BBL], and unified stomatal optimization [USO]) and three optimization factors (water potential response function f[θ]), leaf temperature difference [ΔT], and temperature response function f[T]) to optimize, refine, and validate the most suitable g_sw model for cotton grown under plastic film drip irrigation.

Results revealed that the USO model exhibited the highest simulation accuracy, followed by the BBL and BWB models. Among the three models, the USO model incorporating ΔT, f(θ), and f(T) was the most accurate improved model. Compared to the BBL and BWB models, its 2-year R² values increased by 3.77%-49.75% and 1.94%-55.98%, respectively, 0.35%-38.10%, and 8.99%-45.21%, respectively. Furthermore, treatments with higher lower irrigation limits (F2B2 and F2B3) exhibited superior simulation accuracy compared to other irrigation deficit treatments, making them more suitable for the application of the improved model.

Overall, accurate estimation of g_sw requires the model to account for f(θ), ΔT, and f(T). Under conditions where soil moisture is maintained at 70% of field capacity, this improved model shows more precise simulation results. For cotton in the study region, the USO model incorporating ΔT&f(θ)&f(T) is recommended for simulating g_sw.