Soil microbial diversity in organic and non-organic pasture systems

Authors: ACHARYA, MOHAN - University Of Arkansas; YANG, YICHAO - University Of Arkansas; Ashworth, Amanda; Burke, Joan; LEE, JUNG AE - University Of Arkansas; SHARMA ACHARYA, ROSHANI - University Of Arkansas

Submitted to: PeerJ
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2021
Publication Date: 4/22/2021
Citation: Acharya, M., Yang, Y., Ashworth, A.J., Burke, J.M., Lee, J., Sharma Acharya, R. 2021. Soil microbial diversity in organic and non-organic pasture systems. PeerJ. 9. Article e11184. https://doi.org/10.7717/peerj.11184.
DOI: https://doi.org/10.7717/peerj.11184

Interpretive Summary: The increased use of antibiotics, pesticides, and fertilizers has altered soil biodiversity and has raised concerns about the sustainability of management intensive agriculture. Further, there is a limited understanding of how chemical fertilizers and pesticides affect soil microbial communities. Therefore, the objective of this study is to access soil microbial diversity following 10 years of continuous pasture management (organic or non-organic). Researchers found that organic pasture management promoted greater soil microbial diversity compared to the inorganic pasture system (herbicides and chemical fertilizer applications). Therefore, long-term animal manure (poultry litter and sheep manure) applications improved the soil microbial diversity, which is important for sustainable forage growth, nutrient retention, and pasture resiliency.

Technical Abstract: Understanding the effects of organic pasture management on the soil microbiome is important for sustainable forage production since soil microbiome diversity contributes to improved nutrient cycling, soil structure, plant growth, and environmental resiliency; however, the soil microbiome response to pasture management is largely unknown. This study assessed the soil microbial diversity, richness, and community structure following 10 years of pasture management (organic or non-organic) using Illumina 16S rRNA gene amplicons. Soil samples were collected from 0-15 cm in July and August from 2017-2018. Total soil organic C, N, minerals, and pH were determined. Overall, greater soil bacterial species richness (P = 0.05) occurred in organic relative to non-organic (conventional) systems. Management affected bacterial species richness (Chao1), with greater richness occurring in organic pasture soils and less richness occurring in non-organic systems (P = 0.05). Similarly, management effected bacterial evenness (Simpson’s index), with a more diverse community occurring in organically managed soils relative to non-organic pastures (P = 0.05). Linear discriminant analysis effect size analysis showed statistically significant and biologically consistent differences in bacterial taxa in organic compared with non-organic soils. Therefore, there was a shift in bacterial community structure in organic relative to non-organic soils (P = 0.05). Consequently, pasture management affected soil microbial diversity, with greater diversity occurring in organic than non-organic systems, likely owing to applications of organic poultry litter in organic systems compared to non-organic management (use of inorganic-fertilizers and herbicides). Results indicate that when pastures are converted to organic production systems, soil microbial richness and diversity may increase, thereby resulting in enhanced soil microbiome function in the largest agricultural land use category in the US.