Impact of organic fertilizer substitution and biochar amendment on net greenhouse gas budget in a tea plantation

Tailoring agricultural practices to enhance the soil carbon (C) stock is seen as a promising mitigation tactic to offset greenhouse gas (GHG) emissions in croplands. Tea plantations are not only the important part of economic industry but also one of the crucial agricultural sources of non-carbon dioxide emissions. Although many studies have measured GHG emissions from tea plantations, it remains unknown about the effect of knowledge-based mitigation options on the entire C budget from Chinese rapidly expanding tea plantations. Thus, we carried out a 2-year field trial to provide an insight into the influence of organic fertilizer substitution for synthetic fertilizer and biochar amendment on net ecosystem carbon budget (NECB), net greenhouse gas budget (NGB), and yield-scaled greenhouse gas intensity (GHGI) from a subtropical tea plantation. Results showed that when averaged a 2-year experimental period, both full organic substitution and biochar amendment contributed significantly to the increment in NECB, mainly due to the enhanced soil organic C content in the tea field. Compared with the conventional farm practice, the application of full organic substitution can induce a 52% decrease in both NGB and GHGI. Regardless of fertilizer type, both NGB and GHGI were negative and 2.4 times lower in the treatments with biochar amendment relative to the control. In addition to their roles in maintaining soil health and alleviating soil acidification, our results suggest that organic fertilizer substitution and biochar addition may achieve low carbon development for tea plantations. Our findings will inform efforts to implement and evaluate these tailored mitigation options in tea plantations at a national scale.