A field experiment was conducted for the purpose of examining the effects of different combinations of water and fertilizer applications on the water consumption and yields of alfalfa under subsurface drip irrigation (SDI). The results showed that the jointing and branching stages were the key stages for alfalfa water requirement. The water consumption had varied greatly (from 130 to 170 mm) during the growth period of each alfalfa crop. The water consumption during the whole growth period was approximately 500 mm, and the maximum water consumption intensity was 3.64 mm·d^-1. The overall changes in water consumption and yields during the growth period of the alfalfa displayed trends of first increasing and then decreasing. The sensitivities of the yields to water changes were much higher than that of fertilizer. The water use efficiency (WUE) of the alfalfa was determined to range from 1.68 to 3.20 kg·m^-3, and the rate of growth had ranged from 4.85% to 51.77%. The WUE and rate of growth of the alfalfa indicated the following trend: second crop > third crop > first crop. The results of frequency analysis based on the water‐nitrogen‐yield regression equation are the following: irrigation amounts of 142~165 mm and nitrogen application of 61~80 kg·hm^-2 have a 95% probability of obtaining a hay yield of alfalfa of more than 11903 kg·hm^-2. These results suggest that SDI is a promising irrigation method, which can increase the WUE and hay yield of alfalfa under the condition of SDI within an appropriate amount of water and nitrogen fertilizer, and too low or too high water and nitrogen fertilizer will adversely affect the WUE and hay yield of alfalfa.

Water stress (drought and waterlogging) is one highly important factor affecting food security in China. Investigating the effects of soil moisture stress on the morphological and physiological characteristics of maize seedlings is crucial for ensuring food production. The use of spectral monitoring to observe crop phenotypic traits and assess crop health has become a focal point in field crop research. However, studies exploring the contribution of crop phenotypic and physiological data to the Normalized Difference Vegetation Index (NDVI) are still limited. In this study, a 35-day pot experiment was conducted with seven soil moisture gradients: 50%, 60%, 70%, 80% (control group, CK), 90%, 100%, and 110% treatment. In order to investigate the effects of soil moisture stress on seedling phenotypes, antioxidant enzyme activities, and NDVI, an ASD FieldSpec 4 Hi-Res NG portable spectrometer was used to collect spectral data from maize (Zea mays L. B73) leaves. The contributions of maize phenotypic and physiological traits to NDVI were also examined. The results indicated that (1) the 50% and 110% treatments significantly affected maize seedling phenotypes compared to the CK group; (2) the activities of superoxide dismutase (SOD) and peroxidase (POD) in the leaves increased under water stress, while the activities of glutathione peroxidase (GSH-PX) and ascorbate peroxidase (APX) decreased; (3) soil moisture stress (drought and waterlogging) reduced photosynthetic pigments, chlorophyll content (SPAD), and NDVI, with inhibitory effects intensifying as the stress level increased; (4) Redundancy analysis showed that antioxidant enzymes explained 69.87% of the variation in seedling height, leaf area, and NDVI. Soil moisture stress, chlorophyll, and SPAD explained 58.14% of the variation in these parameters. The results demonstrated that maize seedlings were highly sensitive to soil moisture changes, and the SPAD value contributed significantly to NDVI (p < 0.01). This study provides valuable insights for future research in precision agriculture management

Mulch drip irrigation (MDI) technology can effectively solve the problem of insufficient temperature accumulation during the pre-fertility period and facilitate the efficient supplementation of water and fertilizer during the fertility period in spring corn planting. Moreover, this local MDI technology also has impacts on the farmland environment. To investigate the effect of drip irrigation technology on the water and salt environment of farmland, a field study on corn cultivation was carried out at West Liaohe Plain. In addition, the water and salt dynamics of the farmland were simulated using HYDRUS-2D for mulch drip irrigation (MDI), shallowly buried drip irrigation (SBDI), and sprinkler irrigation (SI), with variable rainfall and initial salt content. The results showed that the distribution of and variation in water and salt in the soil were similar under MDI and SBDI. The change near the drip tape was mainly affected by irrigation, while the water and salt in the soil between drip tapes were correlated with irrigation and rainfall. The amount of salt in the topsoil (5 cm) increased with a decrease in rainfall. With an initial EC = 480 μs/cm (soil salt content 0.1%), the salinity of the topsoil under MDI was significantly higher than that under SBDI and SI within two years. The topsoil salinity was similar for all three irrigation technologies with increasing operating life, reaching a relatively stable state, and much lower than the salinity determination threshold of 480 μs/cm. Given the current conditions of rainfall, soil, buried depth, and mineralization in the West Liaohe Plain, the risk of secondary salinization is minimal if irrigation management is reasonable. This study provides data to support the application of drip irrigation technology in the Western Liaohe Plain.

Groundwater resources serve as the primary source of water in the agro-pastoral ecotone of northern China, where scarcity of water resources constrains the development of agriculture and animal husbandry. As a typical rainfed agricultural area, the agro-pastoral ecotone in Inner Mongolia is entirely dependent on groundwater for agricultural irrigation. Due to the substantial groundwater consumption of irrigated farmland, groundwater levels have been progressively declining. To obtain a sustainable irrigation pattern that significantly conserves water, this study faces the challenge of unclear water transport relationships among water, soil, and crops, undefined water cycle mechanism in typical irrigation units, and water use efficiency, which was not assessed. Therefore, this paper, based on in situ experimental observations and daily meteorological data in 2022–2023, utilized the DSSAT model to explore the growth processes of potato, oat, alfalfa, and sunflower, the soil water dynamics, the water balance, and water use efficiency, analyzed over a typical irrigation area. The results indicated that the simulation accuracy of the DSSAT model was ARE < 10%, nRMSE/% < 10%, and R² ≥ 0.85. The consumption of the soil moisture during the rapid growth stage for the potatoes, oats, alfalfa, and sunflower was 7–13% more than that during the other periods, and the yield was 67,170, 3345, 6529, and 4020 kg/ha, respectively. The soil evaporation of oat, potato, alfalfa, and sunflower accounted for 18–22%, 78–82%; 57–68%, and 32–43%, and transpiration accounted for 40–44%, 56–60%, 45–47%, and 53–55% of ETa (333.8 mm–369.2 mm, 375.2 mm–414.2 mm, 415.7 mm–453.7 mm, and 355.0 mm–385.6 mm), respectively. It was advised that irrigation water could be appropriately reduced to decrease ineffective water consumption. The water use efficiency and irrigation water use efficiency for potatoes was at the maximum amount, ranging from 16.22 to 16.62 kg/m³ and 8.61 to 10.81 kg/m³, respectively, followed by alfalfa, sunflowers, and oats. For the perspective of water productivity, it was recommended that potatoes could be extensively cultivated, alfalfa planted appropriately, and oats and sunflowers planted less. The findings of this study provided a theoretical basis for efficient water resource use in the agro-pastoral ecotone of Northern China.

The impact of different combinations of water–nitrogen coupling on maize yield and the environment needs investigation. Low, medium, and high levels of irrigation and N application gradients were studied through field experiments to elucidate the suitable water–nitrogen coupling zone for spring maize in the West Liaohe Plain during three hydrological year patterns under drip irrigation with plastic film. The effects of different water–nitrogen couplings on maize yield, water- and nitrogen-use efficiencies (WUE and NUE), and post-harvest soil alkali-hydrolyzable N residues were studied under integrated drip irrigation by varying the application rates of water and fertilizer. A multi-objective optimization of water–nitrogen coupling zones was performed by integrating maize yield, harvest index, WUE, and soil environmental effects. Results show that with an increase in irrigation and N application rate, the residual amount of alkali-hydrolyzable N increased slowly within a certain range. Upon exceeding a certain amount, residual N increased rapidly, and more N entered the soil environment. The NUE of moderate water–nitrogen coupling treatment was high, with lower environmental risk of residual alkali-hydrolyzable N. Moderate irrigation yielded the highest harvest index in the normal hydrological year. Irrigation rate had a higher impact on yield compared to nitrogen application, because of drip irrigation under plastic film. An appropriate irrigation amount results in a higher WUE and the application of N application must be adjusted according to the rainfall in a particular year. This study highlights the need for structuring water–nitrogen coupling zones specifically for different hydrological years.

Biodegradable mulches have the same temperature- and moisture-preservation effects as ordinary plastic mulches before degradation. After degradation, rainwater enters the soil through the damaged parts, improving precipitation utilization. Under drip irrigation with mulching, this study explores precipitation utilization of biodegradable mulches under different precipitation intensities and the effects of different biodegradable mulches on the yield and water use efficiency (WUE) of spring maize in the West Liaohe Plain, China. In this paper, in situ field observation experiments were conducted for three consecutive years from 2016 to 2018. Three types of white degradable mulch films were set up, with induction periods of 60 d (WM60), 80 d (WM80), and 100 d (WM100). Three types of black degradable mulch films were also used, with induction periods of 60 d (BM60), 80 d (BM80), and 100 d (BM100). Precipitation utilization, yield, and WUE under biodegradable mulches were studied, with ordinary plastic mulches (PM) and bare land (CK) set as controls. The results showed that as precipitation increased, the effective infiltration of precipitation decreased first and then increased. When precipitation reached 89.21 mm, plastic film mulching no longer affected precipitation utilization. Under the same precipitation intensity, the precipitation effective infiltration ratio increased as the damage to the biodegradable film increased. Still, the intensity of this increase gradually decreased as the damage increased. The highest yield and WUE were observed for the degradable mulch film with an induction period of 60 days in years with normal rainfall and for the degradable mulch film with an induction period of 100 days in dry years. In the West Liaohe Plain, maize planted under film receives drip irrigation. We recommend that growers select a degradable mulch film with a degradation rate of 36.64% and an induction period of approximately 60 days in years with normal rainfall, and a degradable mulch film with an induction period of 100 days in dry years.