01746nas a2200133   4500008004100000245007600041210006900117300001500186490000700201520126500208100001801473700001701491856010401508       1996                        eng d00aDenitrification in soil profiles beneath grassland and cultivated soils0 aDenitrification in soil profiles beneath grassland and cultivate  a1822 -18280 v603 aThe denitrification potential of subsoils and aquifers must be characterized to assess the ultimate fate of soil N. This experiment was conducted to study changes in the subsurface distribution and activity of denitrifying bacteria as a result of cultivation. We examined soil profiles for their capacity (N addition) and potential (N + C addition) to denitrify as well as for denitrifying bacterial numbers in a Reading silt loam (fine, mixed, mesic Typic Argiudoll) soil under grassland and cultivation. Denitrifying enzyme activity was undetectable throughout the subsurface of soil profiles at both sites. Overall, the cultivated site had significantly higher NO−3 concentrations, denitrifier populations, and denitrification potential. Denitrifying bacteria were stratified in the vadose zone at the prairie site, with lowest numbers and lowest denitrification potential occurring at the interface of the water table. Although C addition enhanced denitrification at this site, the profile was not nearly as limited by C as that of the cultivated site. The results demonstrated that increased N inputs and cultivation during approximately 50 yr changed the denitrifying population and denitrification potential in the vadose and saturated zones of soils.1 aSotomayor, D.1 aRice, C., W.  uhttp://knz.lternet.edu/content/denitrification-soil-profiles-beneath-grassland-and-cultivated-soils