Objectives The black soil region of Northeast China is regard as the granary of China. However, due to the intensive agricultural production activities in the past decades, the crop yields of this region fluctuated, and soil fertility decline is appeared over time. We investigated the effects of fertilization regimes on the maize and soybean yields of the region, and the main impact factors, to provide a scientific basis for the efficient and sustainable crop production.

Methods A total of 558 sets of matched pairs of data were collected from 88 published articles in that the field experiments were conducted in the black soil region of Northeast China across 1990−2024. Meta-analysis method was used to study the maize and soybean yield effects of chemical fertilizers, organic materials, and organic and inorganic combined application, and the influence factors through regression and random forests analysis.

Results Fertilization generally increased the yields of maize and soybean by 24.1%−74.5% and 14.7%−30.7%, respectively. The yield increment by chemical fertilizer application alone was 73.6% for maize and 28.7% for soybean, while those by organic material application alone were 22.3% and 14.2%, and those by combination of inorganic and organic fertilizers were 26.5% and 16.4%. The maize and soybean yields kept increasing with the rise of N application rates and became stable at N application rate reaching 210−480 kg/hm² and 120−450 kg/hm², respectively. The optimum N application rate for soybean, regardless nitrogen fertilizer types, was always lower than that of maize. The optimum N application rate of chemical fertilizer alone was lower than that of organic material alone, and their combined application for the same crop. The yield responses of maize and soybean also enhanced with elongation of fertilization years. Both the maize and soybean yield effects of fertilization were positively correlated to annual average temperature, initial soil pH, and available nutrient contents, but negatively correlated to the initial soil organic C (SOC) content and C/N ratio.

Conclusions The soils in the black soil region of Northeast China are generally high in initial pH, low in initial SOC content and C/N, the maize and soybean production rely heavily on fertilization, especially the application of chemical fertilizers. Therefore, rational fertilization should comprehensively consider fertilizer types, rate and time, as well as the local climate and soil physicochemical properties, so that to acquire efficient crop production and improved soil fertility.