Nitrogen forms in reseeded Kansas farmland.

Abstract

A study of mineral Nitrogen forms (ammonium and nitrate) in a native prairie and reseeded old fields was conducted from January 1986 through December 1986. All study sites were located on the Kenoma soil series. Samples were taken from each site monthly and analyzed using the microdiffusion procedure of Keeney and Nelson (1982). The most probable number of Nitrosonmonas and Total Plate Count were also determined for each sample. A nitrification potential experiment was conducted in which there was minimal disturbance to the soil and vegetation. Results from the microdiffusion tests indicated less than 1.0 ppm of ammonium or nitrate to be present in each of the study sites. The most probable number of Nitrosomonas was also low at all sites, though a decreasing trend from the most recently reseeded site to the native prairie was found. With the addition of ammonium, the amount of nitrate and number of Nitrosomonas increased only slightly. An increase in ammonium was detected, possibly due to mineralization of organic nitrogen. Overall biomass production was much lower in the control prairie site than that of a similar prairie which had not been heavily grazed. This suggests that grazing could be influencing the productivity and the nitrogen pool present. However, the low level of nitrogen present and small population of Nitrosomonas on all sites suggest the climax prairie grasses are affecting the forms of nitrogen.