Differences in maize yield and its response to nitrogen fertilizer application under different soil nitrogen fertility levels in the Huang-Huai-Hai Plain

Objectives This study aimed to investigate the yield differences caused by soil nitrogen (N) fertility levels and N fertilization across the main maize-producing areas of the Huang-Huai-Hai Plain. The findings will provide a theoretical foundation and technical support for enhancing maize production and optimizing N fertilizer management.

Methods Using maize, N fertilizer, N application rate, and yield as keywords, we collected the experimental data on maize N fertilization conducted in the Huang-Huai-Hai Plain from 2000 to 2024 from both Chinese and English databases, including CNKI, VIP, Wanfang, Web of Science, and Google Scholar. The maize yield under no N application was defined as the soil native N-derived yield, and the soil N fertility levels were classified into four categories based on the soil native N-derived yield levels: <6 t/hm², 6−8 t/hm², 8−10 t/hm² and >10 t/hm². The yield difference among different soil N fertility levels, the N fertilizer-induced yield increase rate, contribution rate of N fertilizer to yield, and N fertilizer use efficiency were analyzed. The boundary line fitting method was employed to analyze the relationship between soil native N-derived yield and N-applied yield of maize, and the impact of soil N fertility levels on the gaps between predicted and actual yields. The effects of soil N fertility levels on the stability and sustainability of maize yields were also evaluated.

Results Across the Huang-Huai-Hai Plain, the soil native N-derived yield, N-applied yield, and N fertilizer-induced yield increase rate averaged 8.07 t/hm², 10.06 t/hm², and 28.19%, respectively. The proportion of maize yield obtained from the basic soil N supply that was below 8 t/hm² was 52.12%. As soil N fertility levels increased from <6 t/hm² to >10 t/hm², the N-applied yield increased significantly from 8.37 t/hm² to 12.78 t/hm², while the yield increase rate decreased markedly from 58.03% to 14.41%. Over the 25-year period, soil native N and N fertilizer contributed an average of 81.46% and 19.80% to maize yield, respectively. The average partial factor productivity and agronomic efficiency of N fertilizer were 51.55 kg/kg and 9.93 kg/kg, respectively. The soil N fertility level did not significantly impact the partial factor productivity of N, while the N agronomic efficiency showed a significant decline with increasing soil N fertility levels. Using the boundary line method, the predicted maximum yield of maize in the Huang-Huai-Hai Plain was 15.25 t/hm². As soil N fertility levels increased from <6 t/hm² to >10 t/hm², the gap between the predicted and actual yields decreased from 6.88 t/hm² to 2.47 t/hm², the yield stability index decreased from 0.22 to 0.11, and the yield sustainability index increased from 0.53 to 0.71.

Conclusions  In the Huang-Huai-Hai Plain, the proportion of areas with soil native N-derived yield below 8 t/hm² is as high as 52.12%. The maize yield gap between the highest and lowest soil N fertility levels reaches 9.99 t/hm², while the yield gap caused by N fertilizer application is 11.61 t/hm². The higher the soil N fertility level, the higher the contribution rate of soil N to maize yield, and the better the yield stability and sustainability. Therefore, improving the basic soil N fertility level is a crucial measure to enhance nutrient use efficiency of maize and achieve a win-win situation in both economic and environmental benefits in the Huang-Huai-Hai Plain.