Plastic film mulching has been widely used to improve crop yield and water use efficiency, although the effects of plastic film mulching on water, heat, nitrogen dynamics, and crop growth are rarely presented comprehensively. This study investigated a large number of studies in film mulching fields from the past 10 years (mostly from 2019 to 2023) and summarized the impact of plastic film mulching, progress in modeling with film mulching, and future research directions. The effects of plastic film mulching were intricate and were influenced by film mulching methods, irrigation systems, crop types, crop growth stages, etc. Overall, plastic film mulching showed a positive effect on improving soil water, temperature, and nitrogen status, enhancing crop transpiration and photosynthetic rates, and promoting crop growth and yield, although film mulching may have negative effects, such as increasing rainfall interception, blocking water entering the soil, and reducing net radiation income. The crop yield and water use efficiency could increase by 39.9–84.7% and 45.3–106.4% under various film mulching methods. Coupled models of soil water and heat transport and crop growth under plastic film mulching conditions have been established by considering the effects of plastic film mulching on the upper boundary conditions of soil water and heat, energy budget and distribution processes, and the exchange of latent and sensible heat between soil and atmosphere. The models have good applicability in film mulched farmland of maize, rice, and potato for different regions of China. Further development is needed for soil water, heat, nitrogen migration, and crop growth models under different plastic film mulching methods, and the acquisition of soil and crop indicators under plastic film mulching conditions based on big data support. The study will provide reference for the subsequent development and innovation of plastic film mulching technology.

The Soil–Water–Atmosphere–Plant (SWAP) model does not have a mulching module to simulate the effect of film mulching on soil water, heat dynamics and crop growth. In this study, SWAP model parameters were selected to simulate the soil water–heat process and crop growth, taking into account the effect of film mulching on soil evaporation, temperature, and crop growth, in order to predict the influence of future climate change on crop growth and evapotranspiration (ET). A most suitable scheme for high yield and water use efficiency (WUE) was studied by an experiment conducted in the Shiyang River Basin of Northwest China during 2017 and 2018. The experiment included mulching (M1) and non-mulching (M0) under three drip irrigation treatments, including full (WF), medium (WM), low (WL) water irrigation. Results demonstrated that SWAP simulated soil water storage (SWS) well, soil temperature at various depths, leaf area index (LAI) and aboveground dry biomass (ADB) with the normalized root mean square error (NRMSE) of 16.2%, 7.5%, 16.1% and 16.4%, respectively; and yield, ET, and WUE with the mean relative error (MRE) of 10.5%, 12.4% and 14.8%, respectively, under different treatments on average. The measured and simulated results showed film mulching could increase soil temperature, promote LAI during the early growth period, and ultimately improve ADB, yield and WUE. Among the treatments, M1WM treatment with moderate water deficit and film mulching could achieve the target of more WUE, higher yield, less irrigation water. Changes in atmospheric temperature, precipitation, and CO₂ concentration are of worldwide concern. Three Representative Concentration Pathway (RCP) scenarios (RCP2.6, RCP4.5, RCP8.5) showed a negative effect on LAI, ADB and yield of seed-maize. The yield of seed-maize on an average decreased by 33.2%, 13.9% under the three RCPs scenarios for film mulching and non-mulching, respectively. Predicted yields under film mulching were lower than that under non-mulching for the next 30 years demonstrating that current film mulching management might not be suitable for this area to improve crop production under the future climate scenarios.

Core Ideas: Our method can estimate groundwater recharge through multiple contrasting lithological layers. Both human activities and natural aquifer character impact groundwater flow and transport. Geomembrane liners can effectively control the leakage from Yongding River. The ecological restoration of Yongding River can alleviate the local water deficit. Reclaimed water was discharged into the Yongding River channels as ecological water. Pollutants from such water may leak into the underlying aquifer and put the groundwater environment at risk. River leakage estimation under different possible river lining conditions and the established groundwater flow and reactive solute transport model were jointly applied to investigate the impact of the ecological restoration of the Yongding River on the local groundwater environment. Scenario‐based investigations were conducted since the channel reconstruction in 2009. The results show that the seepage from the Yongding River without liners can greatly raise the groundwater level. Leakage through liners constructed with geomembranes can effectively control the seepage of water and the spread of solutes in the aquifer. From June 2009 to December 2010, the leakage amount has been only 1.65 × 10 ⁴ m ³ , and the unconfined aquifer shows a negative budget of 4.55 × 10 ⁷ m ³ . The spreading extent of flow and potential pollutants increases with the amount of leakage from the river. Water management strategies, such as the South‐to‐North Water Diversion Project and Yongding River restoration could help alleviate the water deficit of the Yongding River alluvium fan (YRAF) by reducing groundwater exploitation and increasing groundwater recharge. The necessity of the maintenance of riverbed liners and control of the water quality of Yongding River were highlighted by the scenario analysis. The methods applied in this study could be used for reference in the other polluted rivers, especially with liner installation.

Drip irrigation under mulch is a widely used technique in the arid region of northwest China. The partially mulched soil and the bare strips between mulched areas may complicate the migration of water, salt, and heat in soils, and cause lateral salt accumulation on bare soil surfaces. For investigating hydrothermal dynamics and salt distribution patterns under such circumstances, tank experiments with drip irrigation under plastic film on partially mulched soil were conducted under two intensities of drip irrigation (i.e., low (W1) and high (W2)) with the same total irrigation amount. The spatial distributions of soil water, temperature, and electrical conductivity were monitored accordingly. The two-dimensional (2D) model of soil water, salt, and heat transport under drip irrigation and partially mulched soil conditions was established using HYDRUS-2D, and kinetic adsorption during salt migration was considered. The results of the experiments showed that the uneven distribution of the hydrothermal state led to the accumulation of salt on the un-mulched soil surface. Water migrated from where the dripper was located, and heat accumulated mainly in the mulched soil. HYDRUS-2D matched reasonably well with the observed data, with an ${\mathrm{R}}^2$ higher than 0.54. Under the partially mulched conditions, lower intensity of drip irrigation (W1) show higher desalination efficiency in root zones, with less even lateral salt distribution. Scenario simulations further demonstrated that a larger total irrigation amount would result in a larger desalination zone, and drip irrigations with appropriate incremental intensity could improve salt leaching in the root zone with increased lateral migration of water.

Purpose: Soil salinization and degradation in the arid and semiarid areas are a worldwide phenomenon. Soil capping with capillary barriers is a potential practice to hydraulically isolate contaminated soils, which may improve the soil environment for plant growth. This study aims to investigate the influences of soil capping on crop growth and soil salinization control in the arid area with shallow groundwater tables.Materials and methods: A one-dimensional agro-eco-hydrological model, LAWSTAC, capable of simulating water and solute transport in layered soil coupled with crop growth, was applied for simulating sunflower growth under field condition in Arid Northwest China. The model was calibrated and validated with the experimental data of 2012 and 2013 crop seasons. The calibrated model was then used to explore how the soil capping consisting of combinations of fine soil (10, 15, 17, 19, and 20 cm thick) and coarse sand (10, 5, 3, 1, and 0 cm thick correspondingly) would influence the soil water and salt dynamics, and seed yield.Results and discussion: Simulation results by LAWSTAC compared well with the observed soil water content, salt concentration, leaf area index, and seed yield. Further scenario simulations showed that a sand layer in the soil capping could greatly affect the water and salt distribution in the soil above and below the sand layer. Though soil capping could decrease the water storage (WS) in the root zone, it caused no obvious increase in water stress to root uptake for sand thickness of 1–3 cm and also considerably reduced the root zone salt content (SC) in crop season compared with that without soil capping. The average WS during the crop season showed a negative correlation with the thickness of sand layer in the soil capping. The average SC from planting to harvest was significantly lower for thicker sand in the soil capping. To soils with high background salinization, the increase of sand thickness would be helpful for enhancing seed yield, until it reached a critical value.Conclusions: Coarse soil layer in the soil capping could prevent salt moving into the root zone, while fine soil could supply water to plant once water in coarse soil was low. Thus, in a long run, the soil capping consisting of combinations of fine and coarse soils with certain thicknesses would be an alternative practice for saline soil reclamation and improving crop production in arid area with shallow groundwater tables and soil salinization.