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Winter wheat is the main grain crop in the Yellow River Basin, and optimizing water and nitrogen management can not only improve the yield, but also reduce water and fertilizer waste and environmental pollution. Using two years of winter wheat field trials, the Aquacrop model was calibrated and validated, and 36 different water and nitrogen application scenarios were simulated and analyzed. Among them, the field trials were divided into three N application levels, and three lower limits of water control. The results showed that: (1) the model has good applicability to simulate the growth process of winter wheat in the Yellow River Basin. (2) At a constant level of irrigation or nitrogen application, crop yield initially increased and subsequently decreased with the enhancement of either irrigation or nitrogen application. Finally, through response surface analysis of regression equations, the recommended irrigation volume was determined to be between 296 and 303 mm, and the fertilizer application rate was set between 229 and 261 kg/ha. At these levels, the PFP could achieve over 60% of its maximum. This research provides a theoretical basis for the water-saving, fertilizer-saving and high-yield water and fertilizer management system of winter wheat in the irrigated area of the Yellow River Basin. [ABSTRACT FROM AUTHOR]

Summer maize constitutes a major food crop in the Yellow River Basin. Optimizing nitrogen (N) application management for this crop not only elevates its yield but also reduces N leaching, thereby ensuring food security and lessening agricultural surface pollution. Utilizing two years of summer maize field experiments, the soil water heat carbon and N simulator (WHCNS) was calibrated and validated against empirical measurements. Subsequent analyses employed the calibrated WHCNS to analyze 56 different N management scenarios. These scenarios varied in terms of N application levels, basal N to topdress application ratios, and chase ratios. The entropy-weighted TOPSIS method was utilized for the optimization, considering agronomic, environmental, and economic aspects. The model's calibration accuracy was validated by root mean square errors, relative root mean square errors, and mean errors for soil volumetric water content and soil nitrate N content. The calibration results demonstrated that the new model was capable of simulating the soil hydraulic characteristics, N cycling, and the growth and development of summer maize during the reproductive phase in the Yellow River Basin. Scenario analyses revealed that increasing the N application initially elevated, then stabilized, summer maize yields, whereas the N agronomic efficiency first increased and then decreased. Moreover, reducing the basal N to topdress application ratios and increasing the chase ratios during the tasseling and flowering stages could minimize the nitrate N leaching and optimize both the yield and N fertilizer agronomic utilization. Specifically, the optimal N management for the current year involved applying 170 kg·ha−1 of N with a basal N to the topdress N application ratio of 1:5 and a chase ratio of 1:1 during the tasseling and flowering stages. This study lays the foundation for developing N fertilizer management strategies for summer maize cultivation in the Yellow River Basin. Furthermore, the methodology established here can be adapted for optimizing the management of diverse crops in different geographical regions. [ABSTRACT FROM AUTHOR]

The harmonious development between water resources, the economy, and the environment is the foundation of regional high-quality development, and the three are closely related. Based on a full analysis of the current situation of the lower Yellow River, this paper combines domestic and foreign studies, compares the framework of the relationship between water resources, the economy, and environment systems, selects 30 indicators such as average rainfall, natural population growth rate, PM2.5, etc., and establishes an evaluation model of the coupled coordination of the water resources–economy–environment system of the lower Yellow River, and then uses system dynamics to simulate and predict the degree of coupled coordination in the sub-scenarios. The conclusions are as follows: (1) The level of coordinated development in the water resources–environment system outperforms that of the water resources–economy and economy–environment systems in the cities along the lower Yellow River. (2) The coupling coordination degree of the lower reaches of the Yellow River increases from 0.5849 to 0.8209 during the period of 2006–2020, with an average annual increase of 2.62%. (3) A sub-scenario simulation for the 2006–2020 period indicated that the coordination development of the WEE system is optimal under the scenario 4 model, with the coupling coordination degree expected to reach 0.8928 in 2035, marking the advent of high-quality coordinated development. This study can provide a theoretical basis for the ecological protection and high-quality development of the Yellow River Basin. [ABSTRACT FROM AUTHOR]

Strategic management of nitrogen fertilizers can not only mitigate agricultural nitrogen pollution but also significantly enhance crop yield and nitrogen use efficiency. This study was designed to determine the optimal nitrogen fertilizer management strategy for the Yellow River irrigation area. Leveraging two years of field data related to soil water nitrogen and summer maize growth indices, parameters for the Root Zone Water Quality Model 2 (RZWQM2) were calibrated and validated. Subsequently, various scenarios were generated to simulate the impacts of different nitrogen application rates and basal chasing ratios on summer maize yield, nitrogen agronomic efficiency, nitrogen physiological efficiency, and nitrogen apparent recovery rate. The Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method was employed for a comprehensive evaluation. RZWQM2 can effectively simulate the dynamic changes in soil moisture and nitrogen in the Yellow River irrigation area, and the results indicated that the mean relative error (MRE) between the simulated and observed values varied from 5.77% to 14.09%, and 4.36% to 33.01%, while the root mean square error (RMSE) ranged from 0.016 to 0.037 cm3/cm3, and 0.111 to 1.995 mg/kg. The normalized root mean square error (NRMSE) varied between 6.20% to 14.42% and 5.24% to 17.84%, respectively. The results validate the model's effectiveness in simulating summer maize yields and nitrogen metrics under varying nitrogen fertilizer management practices. A nitrogen application rate of 180–200 kg/hm2 (expressed in terms of pure nitrogen) in the Yellow River irrigation area could adequately meet the requirements for summer maize production. The recommended nitrogen fertilizer management strategy in the Yellow River irrigation area involves applying 200 kg/hm2 of nitrogen in a 1:2:1 ratio during the sowing, trumpeting, and anthesis stages. [ABSTRACT FROM AUTHOR]

(Objective) Bioavailable water and nutrients to crops depend not only on root architecture but also on how water and nitrogen fertilizer are applied. In this paper, we investigated the effects of irrigation and fertilization on water and nitrogen dynamics in soil of a winter wheat field under border irrigation.(Method) The experiment was conducted in a wheat field in Henan province, where changes in water and nitrogen in soil under border irrigation were measured. These data were used to validate the HYDRUS-1D model, and the validated model was then used to elucidate how a change in irrigation and fertilization modulates water and nitrogen dynamics in the root zone of wheat under border irrigation. (Result) The HYDRUS-1D model simulated water and nitrogen dynamics in the root zone well. The coefficient of determination (R2) between the simulated and measured data was greater than 0.84, with its associated RMSE and MAE less than 0.807 and 0.695, respectively. Increasing the low critical soil water content for resuming irrigation moved nitrate in the top 0~20 cm soil layer to 20~100 cm soil layer 1~2 days after the irrigation, but it did not show significant effects on ammonium dynamics in the soil. Increasing nitrogen fertilization increased nitrate and ammonium nitrogen in the 0~60 cm soil layer significantly, especially in the 0~40 cm soil, but reduced water content in the 0~40 cm soil layer. (Conclusion) The HYDRUS-1D model is able to simulate water and nitrogen movement in soil under border irrigation, and the simulated results can help to improve irrigation and fertilization management for wheat production in the studied and similar areas. [ABSTRACT FROM AUTHOR]