Abstract
Elucidating the succession of soil microbial communities and microbial functions at key plant growth stages is a major goal of microbial ecology research. In this study, we investigated the succession of soil bacteria during four fertilizer treatments (control, NPK, NPK + pig manure, and NPK + straw) and at three crucial rice growth stages (tillering, heading, and ripening) in paddy soil from a rice-wheat cropping system over a 10-year period. The results showed that the bacterial community and function composition of the control treatment was significantly different from that of the other treatments with NPK fertilizers, and S1 from others stages (ANOSIM, p < 0.05). The application of pig manure could reduce the effects of applying NPK fertilizers on bacterial communities in heading and ripening stages, but the effects of straw returning is not obvious. Variance partitioning analyses (VPA) suggested that pH, OM, and AK appeared to be key factors responsible for the microbial community changes observed in all the treatments or stages. The correlation results showed the bacterial families different between S1 and other stages such as Micromonosporaceae, Nocardioidaceae, Gaiellaceae, and Anaerolineaceae etc., were correlated with bacterial KEGG metabolic pathways. In addition, the topological of the soil bacterial community network with more nodes, links and higher Maximal degree at the heading stage and maintained relatively similar topological structures at the heading and ripening stages. However, the topological of the functional networks at the ripening stage were a small yet complicated co-occurring network with 209 nodes, 789 links, higher Average connectivity (avgK), and Maximal degree. These results suggest an obvious succession of soil bacteria and bacterial function at the key rice growth stages, but the topological of functional network structure of bacteria changes a little in the early and middle stages of rice, while its changes significantly in the ripening stage of rice growth.
Highlights
The rice-wheat cropping system is the main grain production system in the Yangtze River Basin in China (Wang et al, 2016a), and soil acidification, continuous cropping obstacles and soil-borne diseases are the major issues affecting ricewheat production in this area
The objectives of this study were to (1) understand the effects of fertilizers and rice growth stages on the soil bacterial community structure and bacterial metabolic functions, (2) explore the key soil environmental variables that strongly affected the succession of the bacterial community during the paddy stages in a rice-wheat cropping system, and (3) understand the variations between the topological shift of the soil bacterial networks and that of the metabolic functional networks during the rice growth stages
The influence of the rice growth stages was mainly reflected in the Principal coordinate analysis (PCoA) axis2
Summary
The rice-wheat cropping system is the main grain production system in the Yangtze River Basin in China (Wang et al, 2016a), and soil acidification, continuous cropping obstacles and soil-borne diseases are the major issues affecting ricewheat production in this area. Fertilization can significantly change the community structure of soil microorganisms. Several studies using different methods for testing diversity reported that the soil bacterial and functional gene communities show obvious differences among different plant growth stages (Noll et al, 2005; Rui et al, 2009; Krause et al, 2010; Edwards et al, 2015; Li et al, 2016; Wang et al, 2016a). It is essential to explore the internal dynamics among soil bacteria, the functional gene community, and the fertilizer and plant growth stage, which are important factors that influence the ecosystem function and sustainability of the cropping system
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