Response of Native Short Grass Prairie and Conservation Reserve Program Grassland Soil Microbial Communities to Feedyard Cattle Manure Applications.

This study documents the effect of annual (both fall and spring) applications of three rates of N (50, 125, and 200 kg/ha) in the form of feedyard cattle manure on grassland ecosystems and on soil microbial composition.  Replicate treatments (n=4) of feedyard cattle manure N applications plus checks were made to native short grass prairie and old world bluestem grass ecosystems starting in the spring of 2000 and continued until the fall of 2006.  A significant increase in biomass in response to N application was first observed in 2004 and continued through the last biomass sampling in 2007.  Soil samples for microbial community composition at three depth ranges (0-2.5, 5.0-7.5, and 30.0 to 32.5 cm) were obtained in November of 2008.  Microbial composition was investigated using 16S DGGE-PCR and clone library methods that targeted Proteobacteria, Bacteriodetes, and Firmicutes.  Differences in microbial community composition were observed between both native range and old world bluestem grass communities and between N applications.