Non-synthetic fertilization and no-till farming are practices that have increased considerably over the past decade as a way to reconcile food production with reducing the impacts on natural resources. Additionally, soil microbial communities play a significant role in cycling amended nutrients and subsequently building and maintaining healthy and resilient food and water systems. We need to better understand how management practices in the topsoil can affect the structure and composition of microbial communities in the soil. Specifically, we evaluated the impact of manure amendment and tillage practices (chisel plow and no-till) on the bacterial communities in different soil depths and in leachate. Our objective was to identify shifts in bacterial communities in soil columns over 108 days after swine manure application, as well as in non-manured soil. Intact soil columns were collected from plots maintained under chisel plow or no-till with corn and soybean rotation. Six simulated rainfalls were applied during the experiment and drainage water from the columns was sampled. Soil columns were destructively sampled to collect samples representative of two depths. DNA was extracted, and targeted 16S-rRNA gene sequencing was used to characterize microbial community structure.
Results/Conclusions
Multivariate analyses showed that the overall variation of the microbial community was mainly explained by the soil layers (top and bottom of soil column). Soil management history (chisel plow and no-till) or the addition of manure were the next factors which explained the most variance of microbial communities, suggesting that soil management significantly shapes the differentiation of bacterial communities. These effects were most noticeable in the lower layer of the soil profile, especially with the addition of manure. We detected important temporal variations in the structure and composition of the topsoil microbiomes, which were not significant in the bottom layers. Leachate characterization showed clear changes between bacterial communities from manured and non-manured samples, which were significantly different in soils from varying management histories. Network analysis of the microbiomes showed that leachate from manured soils has specifically greater dominant interactions with topsoil microbiota, whereas leachate from non-manured soils showed higher modularity throughout the soil profile. Our results suggest that the manure application and soil tillage are highly capable of altering the composition and structure of the bacterial community above and below ground and directly and distinctly affect the microbial composition of drainage waters from agricultural systems.