Sarah Kemmitt

Effects of Soil Management from Fallow to Grassland on Soil Microbial and Organic Carbon Dynamics

Permanent 60 year fallow, arable and grassland soils from the Highfield Ley-Arable Experiment at Rothamsted Research, UK were used to investigate if extremes in soil management affected soil microbial biomass, microbial activity and microbial diversity. They were incubated under laboratory conditions, with and without amendment with a labile (yeast extract) and recalcitrant substrate (ryegrass). Microbial biomass ATP concentrations were not significantly different between the soils, with or without substrate addition. The biomasses in the three soils also mineralised the two substrates similarly and microbial biosynthesis efficiency (measured as biomass C and ATP) was similar. However, Phospholipid Fatty Acid (PLFA) analysis revealed that microbial community structure, with and without substrates, differed significantly between soils. Therefore substrate type drives soil microbial ecosystem response much more than does soil microbial biodiversity.