Objective The effects of exogenous nutrients on the forest soil environment and crop nutrient transformation were explored based on rubber and Amomum villosum intercropping system.

Method Four treatments were set up in combination with the gradient fertilization experiment: no fertilizer(CK), farmyard manure(M), chemical fertilizer(F), organic fertilizer + compound fertilizer(O+C), and nutrient inputs were carried out for two consecutive years. The change of soil carbon and nitrogen storage and main factors influencing nutrient absorption efficiency of A. villosum under exogenous nutrients were analyzed.

Result Under natural growth conditions, the soil carbon and nitrogen storage of CK treatment decreased by 4.08% and 3.57%, the above-ground part carbon and nitrogen storage increased significantly by 32.03% and 40.20%, and the underground part carbon and nitrogen storage by 35.47% and 42.58% from 2017 to 2019, respectively. The input of exogenous nutrients accelerated crop nutrient absorption and soil carbon and nitrogen solidification. Compared to CK, it was found M, F and O+C treatments improved total biomass by 5.52%, 9.61% and 11.89%, meanwhile, M and O+C treatments improved soil carbon storage by 6.96%and 8.14% and soil nitrogen storage by 3.15% and 3.43% in 2019, respectively, with significant differences. O+C treatment had the most obvious impact on the conversion and absorption of soil nutrients, and the outputs of soil carbon and nitrogen were showed as O+C > F > M > CK, and the amounts of soil carbon and nitrogen solidification were showed as O+C > M > F > CK.

Conclusion The analysis results show that the long-term understory intercropping of A. villosum will cause the inherent soil carbon and nitrogen storage consumption of the rubber plantation, and exogenous nutrients can effectively increase soil carbon and nitrogen storage and nutrients absorption efficiency and maintain the balance of soil carbon and nitrogen storage. In particular, organic matter plays a positive role in protecting ecological benefits and maintaining sustainable development of soil fertility.