Experimental and numerical investigations on soil–water dynamics in Moistube irrigation under dynamically regulated working pressure heads: scenario simulations under maize cultivation.

• Adjusting water head in Moistube can regulate tube discharge and soil water dynamics. • HYDRUS well simulates water dynamics under varying WPH by treating Moistube as clay. • Raising or lowering WPH accelerates or decelerates wetting front advance. • Scenario of dynamically regulated WPH maintains fit SWC and reduces deep percolation. • Moistube discharge characteristic self-adapts to rainfall and crop evapotranspiration. Moistube irrigation (MTI) accurately delivers moisture to root zone through subsurface nanotube irrigators. How to dynamically adjust the working pressure head (WPH) considering crop evapotranspiration remains unstudied. Here, the Moistube discharge characteristics, wetting front (WF) morphology, and soil water content (SWC) distribution under adjusted WPH (0 → 1, 0 → 2, 1 → 2, 1 → 0, 2 → 0 and 2 → 1 m) were experimentally investigated. HYDRUS 2D model was employed to reproduce the soil water dynamics and validated against the experimental data. Maize growth scenarios under regulated WPH for three representative regions (Nanjing, Hami, and Siping in China) with typical hydrological years were performed. The relatively long-term Moistube discharge, SWC, and deep percolation were analyzed. Results demonstrated that flexible WPH adjustment regulated Moistube discharge, the advance velocity of WF, and SWC within the wetting patterns. With increased (or decreased) WPH, the Moistube discharge rate precipitously raised (or descended) to values positively correlated with WPHs. WPHs of 0, 1, and 2 m corresponded to discharge rates of 0.63–0.76, 2.15–3.34, and 5.53–6.41 cm2 h−1, respectively. WF also noticeably accelerated (or decelerated) as WPH, meanwhile SWC within the wetting pattern increased (or decreased). Upon WPH increase, the elevated SWC intensified the deviation (δ) of wetting body centroid from Moistube. HYDRUS 2D model accurately reproduced the Moistube discharge rate and WF advance (R 2 ≥ 0.90, NSE ≥ 0.70, RSR close to 0), corroborating the feasibility of treating Moistube as a heavy clay. Surprisingly, the Moistube discharge rate obeyed exponential decreasing trend over time after WPH increased but abnormally displayed restrained trends followed by rebounding after WPH decreased. SWC and the deviation of wetting body centroid from Moistube exhibited discrepancies in absolute values but consistencies in trends between the observed and simulated data. Scenario analyses of maize cultivation revealed that regulating WPH accurately replenished crop evapotranspiration and maintained appropriate SWC environments. Regulated WPH in MTI was efficacious in reducing deep percolation and suitable for arid regions. These results could contribute to intelligent MTI by automatically maintaining a balance between Moistube discharge and crop water requirements. [ABSTRACT FROM AUTHOR]