Objectives The comprehensive effects of organic fertilizer replacing partial chemical fertilizer nitrogen (N) on maize yield, N absorption and utilization, and soil N supply were investigated in thin layer black soil region of Northeast China, in order to clarify the suitable proportion of organic fertilizer replacing chemical fertilizer N and provide a theoretical basis for scientific application of organic fertilizer.

Methods In this study, the field located experiment was conducted in Gongzhuling City in Jilin Province from 2022 to 2024, using maize cultivar ‘Fumin 985’ as the test materials, and the average thickness of the tested black soil layer was 29 cm. The treatments comprised a no nitrogen application (N0) control, a chemical fertilizer only control (NPK), and five organic substitution ratios: 10% (M10%), 20% (M20%), 30% (M30%), 40% (M40%), and 50% (M50%). During the key growth stages of maize, measurements were taken for leaf area index, dry matter and N accumulation. At maturing stage, maize yield and its components were investigated. Soil samples were collected from 0 to 100 cm depth to analyze inorganic N content, with an interval of 20 cm, at these key growth stages.

Results Over the three year period, the average yields under M10%, M20% and M30% treatments were 2.6%−6.4% higher than that of NPK treatment, primarily due to increased kernel number per ear and 100-kernel weight. With the increase of organic fertilizer substitution proportion, the leaf area index, N accumulation and translocation, and the contribution rate of translocated N to grain all showed a trend of firstly increasing and then decreasing. The N recovery efficiency (REN), N agronomic efficiency (AEN), and N partial factor productivity (PFPN) followed the same trend, with the peak values observed at M20% treatment. M10% and M30% treatments did not increase these indicators significantly, whereas M40% and M50% treatments showed a decline, with M50% treatment showing a statistically significant reduction. Compared to NPK treatment, M10%, M20% and M30% treatments significantly boosted the inorganic N contents of 0−20 cm soil from silking stage to maturing stage, while reducing the inorganic N contents and apparent N loss amounts in the 60−100 cm soil layer at maturity. The fitting analysis of the organic substitution proportion against maize yield, N recovery efficiency, and apparent N loss revealed the optimal substitution proportion ganged from 15.6% to 21.1%.

Conclusions In thin-layer black soil region of Northeast China, the substitution proportion of chemical nitrogen fertilizer with organic fertilizer should be maintained within a range of 15.6%−21.1%. This substitution proportion can enhance the soil’s capacity to supply inorganic N during silking to filling stage, promote N uptake from silking to maturing stage, and improve maize yield, N utilization efficiency, and reduce N loss.