Shifts in the composition and potential functions of soil microbial communities responding to a no-tillage practice and bagasse mulching on a sugarcane plantation

Abstract

This study examined the effect of conversion from a conventional tillage (CT) to a no-tillage (NT) practice and of bagasse mulching (M) on soil microbial community composition and potential functions, using phospholipid fatty acid (PLFA) analysis and shotgun metagenome sequencing. Our results showed that both the NT and the M treatment increased microbial PLFAs. The shotgun sequencing results suggested that the functional profiles are more resistant to agricultural managements than to community compositions, which supports the hypothesis of the functional redundancy of soil microbial communities. However, some metabolism-related sequences were significantly affected by different treatments. The percentage of sequences related to metabolism of carbohydrates, especially saccharide groups, was significantly higher in the CT soils than in NT and M soils, which may be linked to lower carbon (C) availability in CT soils. Compared with CT, the NT had higher alpha diversity and more sequences related to DNA metabolism, which may be associated with higher nutrient availability. On the other hand, the M treatment decreased the percentages of sequences related to the metabolism of amino acids and derivatives, which may be due to the limited nitrogen (N) because of the high C/N ratio of bagasse. We also observed interaction effects of the NT and M treatments; although both the NT and M treatments increased the relative abundance of Proteobacteria, this variable in NT + M soils was not higher than in each single treatment. Overall, our findings suggest that the microbial communities change their composition and functionality in response to the NT and M treatments, and these shifts have the potential to affect important soil processes that sustain crop productivity, such as C sequestration and major nutrient cycles.