Potential Nitrogen Mineralization in and Short-Term Nitrification Potential of Soils from a Permanent Pasture and a Recently Cultivated Grassland

Net potential nitrogen mineralization (PNM) and short-term nitrification potential (SNP) were measured at 3 depths (0–7, 7–14, 14–21 cm) in soils collected from adjoining permanent pasture and reseeded grassland at the Institute of Grassland and Enviromnental Research (IGER), Aberystwyth. Organic-C and total N concentrations varied little with depth in either soil. At the time of sampling in April 1996, NO_3⁻-N of soils (0–21 cm depth) from the reseeded field (6.2 to 18 mg kg⁻¹ soil) were greater than those from the permanent pasture (2.4 to 3.6 mg kg⁻¹). Net PNM was higher in each layer in permanent grassland, though in both pastures it was at a maximum in the top layer (0–7 cm) ana decreased with depth. In contrast to net PNM, the SNP data revealed that reseeded pasture had almost three times higher nitrification activity than the permanent sward. In both soils, however, SNP varied little with depth. The moisture content varied little with depth but was higher in reseeded pasture than the permanent sward.