The Innovation Team of Soil Health Care of the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS) has made important progress in the research on soil organic carbon increase and fertility improvement under conservation tillage.

The study revealed the main controlling factors and microbial regulation mechanisms of the soil organic carbon priming effect under long-term conservation tillage. The research results increase understanding of the regulation mechanism of soil organic carbon sequestration and fertility improvement, as well as provide scientific and technological support for regional conservation tillage practice and climate change response.

The research results were published in Soil Biology and Biochemistry (IF 8.546).

Soil organic carbon is an important substance for improving soil quality and maintaining the sustainability of agroecosystems. Long-term tillage managements produce the priming effect by altering exogenous carbon inputs, which strongly affects the stability of soil organic carbon. At present, there is a lack of a clarified discussion of the underlying mechanisms that cause the priming effect under long-term tillage management.

To determine the legacy effects of long-term tillage managements on the priming effect,  quantify the fate of exogenous labile C in contrasting soils, and clarify the underlying mechanisms. Soil samples (Aquic Cambisols and Luvic Phaeozems) from two long-term tillage experimental stations in China (Langfang, Hebei and Gongzhuling, Jilin ) were collected for a 13C-labeled incubation experiment.

The results showed that all treatments produced a positive priming effect after glucose addition due to "microbial co-metabolism". In general, compared with the Cambisols, the Phaeozems with lower microbial nitrogen demand and better soil physical protection produced a lower priming effect. The rotary tillage without straw retention exhibited a higher priming effect than no-tillage with straw retention in the Cambisols, but an opposite result was observed in the Phaeozems. The higher nitrogen availability, microbial carbon use efficiency, and labile carbon retention were the major contributors to the lower priming effect. However, the specific mechanisms regulating the priming effect varied with time. At the early stages, the priming effect was driven by “microbial nitrogen mining”, and the driving force was dominated by “microbial stoichiometric decomposition” at later stages.

Dr. Xiaojun Song, from the Innovation Team of Soil Health Care of the Institute of Agricultural Resources and Regional Planning, is the first author of this article, and research fellow Wu Xueping and research associate Wu Huijun are the co-corresponding authors. This research was funded by the National Key R&D Program and the  Agricultural Science and Technology Innovation Program of the Chinese Academy of Agricultural Sciences.

Citation method and paper link:

Song, X J., Liu, X T., Liang, G P., Li, S P., Li, J Y., Zhang, M N., Zheng, F J., Ding, W T., Wu, X P., Wu, H J., 2022. Positive priming effect explained by microbial nitrogen mining and stoichiometric decomposition at different stages. Soil Biology and Biochemistry 175, 108852. doi:10.1016/j.soilbio.2022.108852

Paper link：https://www.sciencedirect.com/science/article/pii/S0038071722003091