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Title: Soil microbial community dynamics as influenced by composted dairy manure, soil properties and landscape position

item Watts, Dexter
item Torbert, Henry - Allen
item Prior, Stephen - Steve

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2010
Publication Date: 10/1/2010
Citation: Watts, D.B., Torbert III, H.A., Feng, Y., Prior, S.A. 2010. Soil microbial community dynamics as influenced by composted dairy manure, soil properties and landscape position. Soil Science. 175(10):474-486.

Interpretive Summary: Microbes are responsible for supplying the soil with plant available nutrients when using manure as a fertilizer source. Thus, a study was conducted to evaluate how soil microbes are affected by manure addition, season and differences in slope and soil types. Addition of dairy compost increased the activity of the microbes compared to soil without dairy compost. Soil microbes were more active in the summer season compared to the winter season. Slope and soil-type affected microbial activity with the loam soil located in a depressed area having the greatest impact on microbial activity. A sandy loam soil located at the top of the slope had the least amount of activity. An evaluation of the microbial community (change in the type of microbes) showed that a change in the type of microbe also occurred. When land managers are using manure as a source of plant nutrients, season and slope of a field and soil type should be considered.

Technical Abstract: Understanding factors that affect plant growth, whether it is manure addition, season, or soil-type and landscape variability may also impact soil microbial activity, biomass and community structure. Thus an in situ study was conducted to evaluate microbiological properties of three different soil types and landscape positions located in close proximity to each other during the summer and winter months. The three Coastal Plain soils investigated were Bama (Sandy loam), Lynchburg (Loam) and Goldsboro (Loam). Dairy composted manure was incorporated into in situ soil cores at a rate of 350 kg N ha-1 and compared to unamended controls. Soil microbial biomass N, dehydrogenase enzyme activity, and PLFA analysis were evaluated to assess the microbial properties. Addition of dairy composted manure greatly impacted the soil microbial properties. An increase in microbial activity and immobilization of N was observed with the addition of manure, suggesting that a shift in microbial dynamics had occurred due to the changes in available substrate. This was most evident during summer months, suggesting that warmer temperatures stimulated microbial activity. Landscape and soil type was also shown to affect microbial properties. The Lynchburg soil, a loam soil located in a depressed area, was shown to have the highest microbial biomass and microbial activity. The phospholipid ester-linked fatty acid (PLFA) profiles indicated that a shift in microbial communities occurred between season, manure application, and soil landscape position. Therefore, microbial properties could be a useful tool for providing insight into the long-term sustainability of the soil.