Carbohydrate metabolism bacteria positive effect determines the increasing soil organic carbon during long-term straw fertilization returning

Abstract

In the context of global efforts to reduce carbon (C) emissions, several studies have examined the effects of agricultural practices such as straw returning and fertilization on C sequestration by microorganisms. However, our understanding of the specific microbial groups and their roles in long-term C increase remains limited. In this study, a 36-year (1984–2020) farmland experiment was conducted to investigate the impact of bacterial C metabolism on the augmentation of organic C in a Typic Hapludoll (Mollisol) in the black soil region of Jilin Province, Northeast China. Our results demonstrated a noteworthy increase in the diversity of microorganisms in the farmland as a result of long-term straw returning and application of mixed chemical fertilizers. However, by examining the functions of microorganisms involved in C metabolism, it was observed that the effects of fertilization on C metabolism were relatively consistent. This consistency was attributed to a deterministic competitive exclusion process, which minimized the differences between treatment groups. On the other hand, the influence of straw addition on C metabolism appeared to follow a more random pattern. These changes in microbial activity were closely linked to the downregulation of core metabolic pathways related to C metabolism. Notably, long-term fertilization had a negative impact on soil organic C levels, while long-term straw returning plus fertilization resulted in a positive increase in soil organic C. These findings have important implications for enhancing soil organic C and grain yield in the regions with typical black soil.