Soil Microbial Community Dynamics as Influenced by Soil Properties and Landscape Position

Factors that affect plant growth, whether it is manure addition, season, or soil-type and landscape variability may provide insight on how to better manage agricultural fields through the evaluation of soil microbial activity, biomass and community structure. Thus, an in situ study was conducted to evaluate microbiological properties from three different soil types and landscape positions located in close proximity of 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. Microbial properties were determined by microbial biomass N, dehydrogenase enzyme activity, and PLFA analysis. Dairy-composted manure addition greatly affected the microbial properties of the soil. 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 the available substrate. This was most evident during summer months, which suggests that warmer temperatures stimulated the microbial activities. Landscape and soil- type was also shown to affect microbial properties. The Lynchburg soil, a loam soil located in a depressed area of the field, was shown to have the highest microbial biomass and microbial activity. Canonical discriminate analysis (CDA) of the phospholipid ester- linked fatty acid (PLFA) profiles was utilized to confirm the results of microbial properties. This analysis indicated that a shift in microbial communities as indicated by PLFA profiles occurred between season, manure application, and soil landscape. Therefore, microbial properties could be a useful tool for providing insight into the long-term sustainability of the soil