Water and nitrogen are crucial for producing spring maize. Currently, irrigation and fertilization systems often rely on a single indicator, resulting in inefficient practices. This study aims to determine an optimal nitrogen application rate for shallow buried drip irrigation (SBDI) to balance growth characteristics, yield (Y), water use efficiency (WUE), and soil nitrogen levels. In a typical semi-arid region of Northeast China, we conducted controlled experiments from 2022 to 2023, adopting a two-factor quadratic saturation D-optimal design method to study the effects of different irrigation amounts (145.40, 271.70, 348.20, and 436.20 mm) and nitrogen fertilizer application amounts (34.80, 185.90, 277.40, and 382.80 kg·hm⁻²) on spring maize. The results indicate that increasing both irrigation and nitrogen application rates can enhance dry matter accumulation (DMA) from 15.17% to 32.70%. The impact of irrigation and fertilization on the net photosynthetic rate (Pn) of spring maize was greater for the irrigation applications than the nitrogen applications, particularly at 9:00 a.m. and 13:00 p.m. and slightly less so at 11:00 a.m. and 15:00 p.m. Concurrently, there were significant increases in total nitrogen (TN1 by 20.85% in the 0–20 cm soil layer; TN2 by 33.33% in the 20–40 cm soil layer) and alkali-hydrolyzed nitrogen (AHN1 by 14.65% at 0–20 cm; AHN2 by 28.86% at 20–40 cm). Y improved from 12.02% to 44.09%, and WUE increased from 20.08% to 140.07%. The optimal water and fertilizer management mode for spring maize SBDI in semi-arid areas was determined through comprehensive analysis using the TOPSIS entropy weight method. When the irrigation amount is 436.20 mm, and the nitrogen fertilizer application amount is 277.40 kg·hm⁻², it can significantly promote the DMA, Y, WUE, photosynthetic characteristics, and soil nitrogen content of spring maize. This study provides a theoretical basis for the practical application of SBDI water–fertilizer coupling for spring maize.

The current design of irrigation and fertilization systems often depends on a single index, leading to irrational systems due to the lack of a comprehensive multi-index evaluation. The aim of this study is to optimize the irrigation and nitrogen fertilizer application levels of spring maize using the TOPSIS method, in order to achieve a balance between growth characteristics, yield, water use efficiency, and soil nitrogen content. In the typical semi-arid region of Northeast China, through precise control experiments from 2022 to 2023, we adopted a two factor quadratic saturation D-optimal design method to study the effects of different irrigation amounts (145.40, 271.70, 348.20, 436.20 mm) and nitrogen fertilizer application amounts (34.80, 185.90, 277.40, 382.80 kg·hm-2) on spring maize. Results indicate that increasing both irrigation and nitrogen application rates can enhance dry matter accumulation by 15.17% to 32.70%. The impact of irrigation and fertilization on the net photosynthetic rate (Pn) of spring maize was found to be greater for irrigation amount than nitrogen application, particularly at 9:00 am and 13:00 pm, and slightly less so at 11:00 am and 15:00 pm. Concurrently, there was a significant increase in total nitrogen (TN1 by 20.85% for 0-20 cm soil layer, TN2 by 33.33% for 20-40 cm soil layer) and alkali-hydrolyzed nitrogen (AHN1 by 14.65% for 0-20 cm, AHN2 by 28.86% for 20-40 cm). Yields improved by 12.02% to 44.09%, and water use efficiency (WUE) saw an increase ranging from 20.08% to 140.07%. The optimal water and fertilizer management mode for spring maize SBDI (shallow buried drip irrigation) in semi-arid areas was determined through comprehensive analysis using TOPSIS entropy weight method. When the irrigation amount is 436.20 mm and the nitrogen fertilizer application amount is 277.40 kg·hm-2, it can significantly promote the accumulation of dry matter, yield, water use efficiency, photosynthetic characteristics, and soil nitrogen content of spring maize. This study provides a theoretical basis for the practical application of SBDI water fertilizer coupling technology for spring maize.