A recent research by the Fertilizer and Fertilization Technology Innovation Team at the Institute of Agricultural Resources and Regional Planning (IARRP) at the Chinese Academy of Agricultural Sciences (CAAS), has unveiled that long-term cultivation and use of green manure can decrease the biodegradability of soil carbon. The findings were published in Resources, Environment and Sustainability.

Building farmland soil organic carbon (SOC) stocks is essential for maintaining soil fertility and supporting sustainable agriculture. While inorganic fertilizers primarily contribute to the accumulation of labile carbon, organic inputs such as green manure supply diverse organic compounds that stimulate humification through microbial processes, helping form more stable carbon pools. Dissolved organic matter (DOM)—the most reactive carbon fraction—plays a central role in carbon cycling and microbial metabolism, yet its molecular transformation pathways and influence on carbon persistence remain poorly understood. Drawing on a 35-year long-term fertilization experiment in the drylands of northwest China, researchers applied Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) combined with molecular network analysis to investigate DOM molecular transformations under green manure and cattle manure treatments. Results showed that green manure significantly enhanced DOM content and molecular stability in the 0–40 cm soil layer—comparable to cattle manure—by increasing molecular weight, aromatization, and humification, thereby reducing biodegradability. In deeper layers (40–100 cm), green manure further improved chemical diversity. Long-term application also promoted the transformation of lignin-like compounds into tannins and condensed aromatics, accelerating the accumulation of stable carbon fractions.

These results demonstrate that long-term green manuring drives DOM molecular structures toward more stable forms, effectively strengthening soil carbon sequestration potential.

The study was first-authored by Dr. Shi Siwei (postdoctoral fellow, IARRP-CAAS), with Prof. Cao Weidong (IARRP-CAAS) as the corresponding author. It was supported by the State Key Laboratory of Efficient Utilization of Arid and Semi-arid Arable Land in Northern China, the National Key R&D Program of China (2021YFD1700200), the CAAS Science and Technology Innovation Project (ASTIP), and the National Modern Agricultural Industry Technology System (Green Manure, CARS-22).

Citation:

Shi, S.W., Chang, D.N., Liang, T., Gao, S.J., Zhou, G.P., Cao, W.D., 2025. Long-term organic fertilization decreases soil carbon biodegradability by mediating molecular transformation of dissolved organic matter. Resources, Environment and Sustainability, 22, 100261.

Article link: https://doi.org/10.1016/j.resenv.2025.100261