S. Lucas-SARE: Effects of organic amendments on aggregation and microbial community dynamics in soils

This project will evaluate the effects of soil amendments on aggregate formation, microbial residue accumulation, and microbial community dynamics in soils with different textures. Experimental soils will have their aggregate structure destroyed by being forced through a 250IJm sieve. They will then be amended with either rye, rye-vetch, farmyard manure, com posted manure, or no-amendment and incubated over 60 days. Soils will be destructively sampled on days 5, 10, 15, 25, 40, and 60 and analyzed for macroaggregate formation and accumulation of the amino sugars glucosamine and muramic acid. These amino sugars are microbial residues that will be used to characterize the relative contributions of fungi and bacteria to aggregation processes. Changes in microbial community structure will also be assessed through analysis of microbial fatty acids on days 0, 15, and 60. Relationships between amendment type, soil type, microbial parameters, and aggregate formation through time will be investigated. The hypothesis being tested is that, relative to other amendments, amendments that stimulate greater fungal activity will also promote greater macroaggregate formation. Anticipated outcomes of this work will provide information on soil management practices that stimulate soil structural enhancement by promoting a favorable microbial community. This information would be useful to those interested in maximizing the agronomic benefits associated with building and sustaining good soil structure.