Soil bacterial biodiversity is driven by long-term pasture management, poultry litter, and cattle manure inputs

Authors: YANG, YICHAO - University Of Arkansas; Ashworth, Amanda; DEBRUYN, JENNIFER - University Of Tennessee; WILLETT, CAMMY - University Of Arkansas; Durso, Lisa; Cook, Kimberly - Kim; Moore, Philip; Owens, Phillip

Submitted to: PeerJ
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/5/2019
Publication Date: 10/1/2019
Citation: Yang, Y., Ashworth, A.J., Debruyn, J.M., Willett, C., Durso, L.M., Cook, K.L., Moore Jr, P.A., Owens, P.R. 2019. Soil bacterial biodiversity is driven by long-term pasture management, poultry litter, and cattle manure inputs. PeerJ. 7:e7839. https://doi.org/10.7717/peerj.7839.
DOI: https://doi.org/10.7717/peerj.7839

Interpretive Summary: Land application of poultry litter is an effective and common way of recycling nutrients back to the land. Conservation pasture management may also reduce nutrient losses and improve soil diversity. However, the impact of poultry litter and pasture management on soil microbial communities is still unknown. Without understanding changes in soil microbial diversity, it is difficult to maintain soil health and recycle nutrients in pasture systems. It is also critical to investigate if soil microbial diversity is changed under long-term pasture management and land applications of poultry manure. This manuscript focuses on characterizing the soil microbiome and evaluates changes based on 13-years of pasture management and land application of poultry litter. Overall, increased grazing pressure and poultry litter applications was linked to increased soil biodiversity. These study results may be useful in predicting how soil microbe communities respond to management and nutrients, which ultimately impacts water quality and plant growth and production.

Technical Abstract: Soil microorganisms are important for maintaining soil health, decomposing organic matter, and recycling nutrients in pasture systems. However, the impact of long-term conservation pasture management on soil microbial communities remains unclear. Therefore, understanding soil microbiome responses and the impact of conservation pasture management, is an important component of maintaining soil health, fertility, and potentially increasing forage yield on the largest agricultural land-use in the US. The aim of this study was to identify soil microbiota and evaluate soil microbiome community differences based on 13-years of pasture management [hayed, continuously grazed, and rotationally grazed with a fenced, un-grazed and unfertilized buffer strip (control)]. Since 2004, all pastures received broiler litter at an annual rate of 5.6 Mg ha-1. Soil samples were collected at a 0-15 cm depth from 2016-2017 and bacterial communities characterized using Illumina high-throughput 16S rRNA gene amplicon sequencing. Overall, pasture management influenced soil microbial community structure, as well as year effects on it (P<0.05). Soils receiving no poultry litter or cattle manure had the lowest microbial abundance, which corresponded to lower soil fertility. Continuously grazed systems had the highest (P<0.05) soil community richness. Consequently, increased grazing pressure may increase soil diversity, owing to continuous manure deposition, which is rich in microflora and nutrients. Another possibility is that the stressed plants excrete compounds in the rhizosphere that provide substrates that encourage the growth of different types of bacteria. These results suggest conservation pasture management (e.g. rotationally grazed systems) may not result in improved microbial diversity, albeit, filter strips were effective at reducing nutrients and bacterial movement as evident by low diversity and fertility in these areas. Overall, animal inputs (litter or manure) may directly drive phylogenetic community structure and be a source of increased diversity in soil microbiome communities.