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【Objective】 Many arid and semiarid regions in North and Northwest of China are poor in freshwater but have saline groundwater. Efficient utilization of these saline waters is crucial for agricultural sustainability. This study seeks to experimentally identify the optimal alternation of freshwater and saline water for irrigating arable crops in areas with shallow groundwater. 【Method】 The experiment was conducted at a maize field from May to October in 2022 at an experimental site in Darat Banner, Erdos. It compared four irrigations: irrigating with saline water only (T1), irrigating with saline water twice followed by a freshwater irrigation (T2), irrigating with saline water once followed by one freshwater irrigation (T3), irrigating with freshwater only (CK). In each treatment, we measured water and salt distribution in the soil, as well as yield of the maize. 【Result】 Alternate irrigation significantly influenced soil moisture and salinity. T3 considerably increased root water uptake during the critical growth stage of the crop, manifested by the 0.75% to 1.3% reduction in water content in the 0~40 cm soil layer, and 2.02% to 3.71% increase in water content in the 40~100 cm soil layer. During the irrigation period, there were 58.45% and 63.98% of soils salinized in T2 and T3, respectively. Compared to CK, alternate irrigation reduced crop yield by 10% to 13%, but saved 33% to 50% of freshwater. Grain yield and water use efficiency of T3 were 90.26% and 23.2% higher than that of T1, respectively, despite its 7.2% reduction in grain yield compared to CK. Groundwater recharge during the reproductive period accounted for 21.74% to 25.55% of the water consumed by the maize. 【Conclusion】 Considering the effect of alternate irrigation on distribution of water and salt in soil, as well as the growth and water consumption of the maize, the most suitable irrigation method for maize in the saline soil is alternating saline water and freshwater(T3).

【Objective】 The objective of this study is to investigate the water and salt movement during freeze-thaw period under partial autumn watering conditions in the Hetao Irrigation District. Specifically, the study focuses on comparing the water and salt dynamics between autumn irrigated farmland and non-autumn irrigated farmland (spring irrigated the following year). 【Method】 Field sampling observations and laboratory experiments were conducted to analyze the variations in soil temperature, soil moisture, and soil salinity during the freeze-thaw period under autumn watering and non-autumn watering conditions. 【Result】 After partial autumn irrigation, the temperature gradually decreased from the surface to the deeper layers in autumn irrigated farmland, while it decreased gradually in spring irrigated farmland. During the freezing process, the soil temperature in the 0~60 cm layer of autumn irrigated farmland dropped below 0 ℃ 30 days earlier than in spring irrigated farmland. In the melting process, the temperature in the 0~60 cm layer of autumn irrigated farmland rose above 0 ℃ 10 days later than in spring irrigated farmland. The desalination of the 0~100 cm soil layer in autumn irrigated farmland occurred mainly after autumn watering and during the freezing period, resulting in a desalting percentage of 47.38%. However, spring irrigated fields experienced salt accumulation of 35.68% and 16.87% during the freezing and melting stages, respectively. Throughout the freeze-thaw period, the net salt flux in each layer of both autumn irrigated and spring irrigated fields was negative, but it increased with soil depth. However, in spring irrigated farmland, the net salt flux initially increased and then decreased with increasing soil depth. 【Conclusion】 The water and salt migration patterns during the freeze-thaw period were influenced by the water level differences between autumn irrigated and spring irrigated fields. The time difference between the freezing and melting processes led to salt accumulation in spring irrigated fields before the next year’s spring irrigation. These findings provide valuable insights into the water and salt migration dynamics in irrigated and non-irrigated farmland, as well as the optimal development of autumn irrigation and spring irrigation practices under local autumn watering conditions.

The competition mechanisms between crop species for water and nutrients, especially nitrate (NO3-N), in intercropping ecosystems are still poorly understood. Therefore, an experiment involving high (300 kg ha-1 for corn and 250 kg ha-1 for tomato), medium (210 kg ha-1 for corn and 175 kg ha-1 for tomato), and low (150 kg ha-1 for corn and 125 kg ha-1 for tomato) N-fertilizer applications (HF, MF, LF, respectively) was conducted in the corn and tomato intercropping ecosystem during 2014 (a calibration period for modeling) and 2015 (a validation period for modeling). The modified HYDRUS-2D code was used to analyze soil NO3-N concentrations (SNC) in the middle between corn rows (Pc), between corn and tomato rows (Pb), and between tomato rows (Pt), NO3-N exchange in the horizontal direction between different regions, NO3-N leaching from the corn, the bare, and the tomato region, and N uptake by crops. Simulated SNCs were in good agreement with measurements, with RMSE, NSE, and MRE of 0.01-0.06 mg cm-3, 0.75-0.98, and 8.7-19.1%, respectively, during the validation period (2015). Average SNCs in the 0-40 cm soil layer were different between Pc, Pt, and Pb. Intensive NO3-N exchange in the horizontal direction occurred during the second stage (Day After Sowing [DAS] 37-113 in 2014; DAS 29-120 in 2015). NO3-N exchange between the corn and bare regions was lower than between the tomato and bare regions due to smaller concentration gradients. However, in the vertical direction, NO3-N leaching from the corn region in both years was 4.1 and 8.8 times larger, respectively, than from the tomato region under HF since NO3-N mainly moved from the tomato region to the corn region. Our results reveal the competition between corn and tomato for N and provide a rationale for formulating and optimizing different fertilizer regimes for different crops in the intercropping ecosystem.

Drip irrigation under plastic film mulching with applications of the N-fertilizer is an excellent agricultural strategy, resulting in saving irrigation water, improving N use efficiency, and increasing crop yield. However, the film residue and nitrate-nitrogen (NO3-N) losses are the leading cause of non-point pollution in agricultural fields. To promote the development of sustainable agriculture, the HYDRUS (2D/3D) model was first calibrated and then validated using experimental data from 2016 and 2017, respectively, collected in the drip-irrigated sandy field with plastic film mulching (PFM), biodegradable film mulching (BFM), and no film mulching (NFM). Additionally, the NO3-N spatial and temporal distributions, uptake, leaching, and use efficiency (NUE) under PFM, BFM, and NFM with 280 kg ha−1 of the N-fertilizer (the local recommendation) were evaluated using both observed and simulated data. These factors were also assessed under BFM with 210 (75 % of the recommended value) and 140 kg ha-1 (50 % of the recommended value) of the N-fertilizer. The results of numerical simulations were in good agreement with observations, with the RMSE, R2, and NSE during verification being 0.01-0.08 mg cm-3, 0.62-0.87, and 0.68-0.94, respectively. When the same amount of the N-fertilizer (280 kg ha−1) was applied in each treatment, there were no apparent differences in NO3-N concentrations in the soil profile, cumulative NO3-N uptake by corn (CNU), and cumulative NO3-N leaching (CNL) in the 100-cm soil depth between the BFM280 and PFM280 scenarios (the subscript indicates the amount of the N-fertilizer) during the early growing season (Day After Sowing [DAS] of 0–78 in 2016 and DAS of 0–92 in 2017). However, CNU and CNL were higher, and the NO3-N concentrations in the upper soil layer (0−40 cm soil layer) lower in these two scenarios than in the NFM280 scenario. The NO3-N concentrations in the topsoil layer (the 0−20 cm soil layer) in the BFM280 scenario were 3.9 % higher than in the PFM280 scenario during DAS 93–154 in 2017 due to the disintegration of the biodegradable film and 26.3 % lower during DAS 79–155 in 2016 because of intensive rainfall. Additionally, the highest NUE (50.9 kg kg-1, the average value for two years) was found when 75 % of the recommended N-fertilizer (210 kg ha−1) was applied. Therefore, an application of 210 kg ha−1 of the N-fertilizer in the BFM scenario can be recommended for sandy farmland to avoid plastic pollution, increase NUE, and effectively promote the development of sustainable agriculture.

Intercropping and drip irrigation with plastic mulch are two agricultural practices used worldwide. Coupling of these two practices may further increase crop yields and land and water use efficiencies when an optimal spatial distribution of soil water contents (SWC), soil temperatures, and plant roots is achieved. However, this coupling causes the distribution of SWCs, soil temperatures, and plant roots to be more complex than when only one of these agricultural practices are used. The objective of this study thus was to investigate the effects of different irrigation treatments on spatial distributions of SWCs, soil temperatures, and root growth in a drip-irrigated intercropping field with plastic mulch. Three field experiments with different irrigation treatments (high T1, moderate T2, and low T3) were conducted to evaluate the spatial distribution of SWCs, soil temperatures, and plant roots with respect to dripper lines and plant locations. There were significant differences (p