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ARS Home » Plains Area » Bushland, Texas » Conservation and Production Research Laboratory » Livestock Nutrient Management Research » Research » Publications at this Location » Publication #206520
Title: The influence of feedlot pen surface layers on microbial community structure and diversity.

Author
item Rice, William
item MASON, AMBER - EA ENGRING, SCI & TECH
item Cole, Noel
item Clark, Ray

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 2/1/2007
Publication Date: 9/16/2007
Citation: Rice, W.C., Mason, A., Cole, N.A., Clark, R.N. 2007. The influence of feedlot pen surface layers on microbial community structure and diversity. In: Proceedings of the ASABE International Symposium on Air Quality and Waste Management for Agriculture, September 16-19, 2007, Broomfield, Colorado. 2007 CD-ROM.

Interpretive Summary: This paper describes an investigation into the types and varieties of bacteria and fungi that are present in the soil profile of a beef cattle confined animal feeding operation. In this study we describe the influence that various feedlot soil profile layers have on the structure and diversity of microbial communities. We characterized the microbial communities associated with these four feedlot layers. A suite of DNA markers were used in PCR assays that target the ribosomal DNA of bacteria (16S) and fungi (18S) was used to evaluate the microbial communities associated with the feedlot layers. We also describe the influence of these four feedlot layers on the bacterial community that is responsible for the oxidation of ammonia to nitrate. Two sets of bacteria working together are responsible for the oxidation on ammonia to nitrite – the ammonia oxidizing bacteria (AOB) of the Betaproteobacteria and the oxidation of nitrite to nitrate – the nitrite oxidizing bacteria (NOB) of the Alphaproteobacteria. We determined that different groups of AOB were found to be associated with these feedlot layers which imply a microbial ecosystem that was uniquely influenced by the physical and chemical properties of these feedlot layers. Both AOB and NOB communities are present in all of the feedyard pen surface layers for nitrification of ammonia to occur. The wet-pack layer showed a marked reduction in both fungal diversity and evenness. A feedlot pen surface may be viewed as microbiological island that has evolved from its original soil, pastureland and cropland ecosystem.

Technical Abstract: The biological and chemical characteristics of feedyard pen surfaces have the potential to affect environmental conditions with respect to air and water quality. Little is known about feedyard pen surface chemistry and biology, especially that of the underlying microbial community structure. The feedlot surface profile can be described as four layers: the unconsolidated (or loose surface), dry-pack, wet-pack, and soil layer. These layers were characterized with respect to: dry matter, pH, electrical conductivity, NO3-N, NH4-N, and total N and C over a four season interval (Mason, 2004). A significant number of interactions were observed between these feedlot layers. Mason (2004) observed that NO3-N concentration was greater in the soil layer than in the manure layers whereas NH4-N concentration was greatest in the wet-pack layer. A net effect is that an established beef cattle feedyard with altered chemical, physical and microbial properties can significantly influence the distribution of N in its various forms. This in turn may influence the distribution of microorganisms intimately involved in the cycling of N such as the ammonia-oxidizing bacteria (AOB) found within the Betaproteobacteria and the nitrite-oxidizing bacteria (NOB) found in the Alphaproteobacteria division. In this study, we characterized the microbial communities associated with these four feedlot layers. A suite of PCR primers (that target 16S and 18S rDNA) was used to evaluate the microbial communities associated with the feedlot layers. We describe the influence that these feedlot layers have on bacterial and fungal community structure and diversity. The influence of the feedlot layers on microbial community structure observed in the spatial grouping of DNA fingerprint patterns and as assessed by two indices of diversity. More importantly we also describe how these feedlot layers have affected both the AOB and NOB community structure and diversity. Different lineages of AOB were found to be associated with these feedlot layers which imply a microbial ecosystem that is uniquely influenced by the physical and chemical properties of these feedlot layers. Both AOB and NOB communities are present in all feedyard pen surface layers for nitrification of ammonia to occur. The wet-pack layer showed a marked reduction in both fungal diversity and evenness. A feedlot pen surface may be viewed as microbiological island that has evolved from its original soil, pastureland and cropland ecosystem.