Winter wheat and cotton are the main crops grown on the North China Plain (NCP). Cotton is often transplanted after the winter wheat harvest to solve the competition for cultivated land between winter wheat and cotton, and to ensure that both crops can be harvested on the NCP. However, the root system of transplanted cotton is distorted due to the restrictions of the seedling aperture disk before transplanting. Therefore, the investigation of the deformed root distribution and water uptake in transplanted cotton is essential for simulating soil water movement under different irrigation methods. Thus, a field experiment and a simulation study were conducted during 2013–2015 to explore the deformed roots of transplanted cotton and soil water movement using border irrigation (BI) and surface drip irrigation (SDI). The results showed that SDI was conducive to root growth in the shallow root zone (0–30 cm), and that BI was conducive to root growth in the deeper root zone (below 30 cm). SDI is well suited for producing the optimal soil water distribution pattern for the deformed root system of transplanted cotton, and the root system was more developed under SDI than under BI. Comparisons between experimental data and model simulations showed that the HYDRUS-2D model described the soil water content (SWC) under different irrigation methods well, with root mean square errors (RMSEs) of 0.023 and 0.029 cm³ cm⁻³ and model efficiencies (EFs) of 0.68 and 0.59 for BI and SDI, respectively. Our findings will be very useful for designing an optimal irrigation plan for BI and SDI in transplanted cotton fields, and for promoting the wider use of this planting pattern for cotton transplantation.

An experiment was conducted to create a science-based program of irrigation and fertilizer application for two-year winter wheat under wide ridge and furrow irrigation in the Yellow River irrigation area. The study was performed in a test field located in Zhengzhou, Henan Province, China. A numerical model of soil water and nitrogen transport for winter wheat under wide ridge and furrow irrigation was created using HYDRUS-2D. The behavior of soil water and nitrogen was predicted for different irrigation water and nitrogen treatments and analyzed to identify pathways of nitrogen transport and transformation. The nitrogen balance was calculated for the different water and nitrogen treatments. The coefficients of determination for measured and predicted values of soil water content, nitrate nitrogen, and ammonium nitrogen in both horizontal and vertical directions were all >0.68; the mean absolute error was <0.06; and the root mean square error was <0.1. These values indicate the feasibility of using a numerical model of nitrogen transport for wide ridge and furrow irrigation. The correlation coefficient R² between simulated values of nitrogen uptake and measured values of total crop nitrogen content was 0.88, the RMSE value was 10.58 kg/ha, and the MAE value was 5.9 kg/ha. Nitrogen loss was primarily caused by denitrification, and the quantity of gaseous nitrogen loss was 7.05–38.2% of the nitrogen form. The total quantity of ammonium nitrogen absorbed by winter wheat plant roots in each treatment was 7.6–15.1% of the total amount of nitrate nitrogen absorbed. The maximum nitrogen uptake was 155.53 kg/ha with a yield of 6888.67 kg/ha at a nitrogen application rate of 220 kg/ha and irrigating to 70% field capacity. The UE of the 220 kg/ha and irrigating to 70% field capacity treatment was relatively high, the PFP of the 120 kg/ha and irrigating to 80% field capacity treatment was relatively high, and the nitrogen use efficiency of the 320 kg/ha and irrigating to 60% field capacity treatment was the lowest overall. This study provides a basis for investigating soil water and nitrogen transport mechanisms of winter wheat under wide ridge and furrow irrigation in the Yellow River irrigation area.