Wilson, Gail (Konza Prairie Biological Station, Division of Biology, Kansas State University, Manhattan, KS, 66506; Phone: 785-532-2892; Email: gwtw@ksu.edu)

Soil Quality and N Dynamics as Affected by Management Practices in Tallgrass Prairie

G.W.T. Wilson *, C. W. Rice

Long-term experimental tallgrass prairie plots, located at Konza Prairie Biological Station in the flinthills of Eastern Kansas, were subjected to 16 y of annual burning, mowing, nitrogen fertilization and untreated control sites to examine effects of these management practices on carbon sequestration and soil quality. These sites are dominated by warm-season C₄ grasses (switchgrass, big bluestem, and indian grass). Annual burning and N addition each increased aboveground productivity of the dominant grasses, and burning generally increased root biomass, in soil collected from 0-5 cm depth. Biomass removal by mowing did not affect aboveground productivity but did reduce root biomass in unburned, unfertilized plots. Microbial biomass C and N were closely correlated with root productivity across these management treatments. Nitrogen fertilization increased both soil organic C and N, and increased the proportion of macroaggregates, with a concomitant decrease in microaggregates. Higher organic C and N were observed in both macro- and microaggregate fractions, as compared to unfertilized controls. Burning (annually, early spring) had no effect on soil C in the surface 5 cm, but decreased soil N and increased macroaggregate formation, as compared to corresponding unburned plots. Mowing (in late June) decreased soil C but did not influence soil aggregate formation. This study indicates that proper management of tallgrass prairie is required to maintain soil quality and utilization of certain management practices may increase a soil’s potential to sequester carbon.