Incorporating green manure is a vital strategy for optimizing cropping systems and improving soil quality. However, it is unclear whether the effects of different types of green manure on subsequent cotton yield and soil fertility improvement are uniform. This study evaluated the effects of three green manure incorporation treatments over a two-year cropping cycle (Chinese violet-cotton-Chinese violet-cotton (T1), rapeseed-cotton-rapeseed-cotton (T2), and ryegrass-cotton-hairy vetch-cotton (T3)) on cotton yield and yield components. These treatments were also compared with the winter fallow-cotton (T0) to analyze differences in soil nutrients and net ecological–economic benefits. No significant differences in cotton yield or yield components were observed among the green manure incorporation treatments. However, averaged across two years, T1 produced a seed cotton yield 8.1% higher than T2 and 3.9% higher than T3. T2 and T3 significantly enhanced soil alkali-hydrolyzed nitrogen, organic matter, and total humus content compared to T0. Notably, T3 increased these parameters by 18.7, 23.9, and 26.8%, respectively. Additionally, T3 achieved the highest net ecological–economic benefit, exceeding T0 by $405/ha. This study highlights the potential of green manure to enhance soil fertility and ecological–economic sustainability in cotton fields. Further research is required to evaluate its long-term benefits and broader implications for sustainable agriculture.

Choosing the proper fertilizer regime for a crop in a given location remains challenging to increase yield, profitability, environmental growth protection, and sustainability. However, the nutrient demand characteristics of cotton in the North China Plain are different at various growth stages. Therefore, we choose the local superior cotton variety (Lumian 532) with high yield as the material, in the present study, we assessed the cotton yield, biomass accumulation and distribution, nitrogen absorption and utilization efficiency, and other parameters by setting four nitrogen allocation ratios (3:5:2, 0:10:0, 3:7:0, and 0:7:3) when the nitrogen application rates were 0, 150, 220, and 300 kg hm⁻². The results showed that when the nitrogen application rate was 300 kg hm⁻², the growth index, biomass, nitrogen content, and yield of Lumian 532 were the highest, while the nitrogen partial productivity (12.2 and 12.8) was the lowest. When the nitrogen application rate was 220 kg hm⁻² and the nitrogen allocation ratio was 3:5:2, the agronomic nitrogen use efficiency (3.2 and 3.5) and nitrogen physiological (24.8 and 25.0) was achieved. When the nitrogen application rate was 150 kg hm⁻², the nitrogen partial productivity (20.6 and 20.9) was the highest. In conclusion, the biomass accumulation and distribution, nitrogen use efficiency, yield, and yield composition of Lumian 532 could be effectively regulated by appropriate nitrogen application rate and nitrogen allocation ratio. Therefore, to optimize the yield and improve the nitrogen use efficiency, the optimal nitrogen application rate of Lumian 532 was 220 kg hm⁻², and the optimal nitrogen allocation ratio was 3:5:2 in the North China Plain. The results provided practical basis for nutrient demand, cotton yield and ecological protection in different growth stages of cotton in North China Plain.