The Innovation Team of Improvement and Amelioration of Soil Fertility at the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS) revealed the underlying mechanisms of soil organic carbon priming in response to exogenous organic matter input level enand long-term fertilization. This research provides a theoretical basis for better understanding and optimization of carbon accumulation in agricultural soils. The findings have been published in the journal "Science of The Total Environment" entitled "Soil organic carbon priming co-regulated by labile carbon input level and long-term fertilization history".

Management practices, such as exogenous organic matter input and fertilization, have important consequences for soil organic matter (SOM) decomposition via the priming effect (PE), thereby impacting soil fertility and C sequestration. However, it remains largely uncertain on how the labile C input levels interact with long-term fertilization history to control PE intensity.

To clarify this question, soil samples were collected from a 38-year fertilization field experiment (including five treatments: chemical nitrogen fertilizer, N; chemical fertilizer, NPK; manure, M1; 200 % manure, M2; NPK plus M2, NPKM2), with strongly altered soil physiochemical properties (i.e., soil aggregation, organic C and nutrient availability). These soil samples were incubated with three input levels of 13C-glucose (without glucose, control; low, 0.4 % SOC; high, 2.0 % SOC) to clarify the underlying mechanisms of PE. Results showed that the PE significantly increased with glucose input levels, mainly attributed to the decline in N availability and associated enhanced microbial N mining from SOM. Compared to N and NPK treatments, the PE was significantly lower in the manure-amendment treatments, especially for low input level, due to more stable SOM by aggregate protection and higher N and phosphorus availability. These results suggested that manure application could alleviate SOM priming via increased soil C stability and nutrient availability. Collectively, our findings emphasize the importance of long-term fertilization-driven changes in labile C inputs, SOM stability, and nutrient availability in regulating PE and soil C dynamics. This knowledge advances our understanding of the long-term fertilization management for soil C sequestration.

Figure 1, Conceptual diagram of the priming effect (PE) in response to labile carbon input level and long-term fertilization history.

The first author of this paper is Associate Researcher Lei Wu from the IARRP, and the corresponding author is Researcher Wenju Zhang. This research was financially supported by the National Program on National Key Research and Development Program of China, Innovation Program of Chinese Academy of Agricultural Sciences, and Youth Innovation of Chinese Academy of Agricultural Sciences.

Paper link: https://www.sciencedirect.com/science/article/pii/S0048969723048003?via%3Dihub