Mineral nitrogen occurring at the depth of 60-90 cm of the soil profile, which is unavailable to the main root mass of grassland plants and arable land crops and which is located in this layer due to leaching to deeper soil layers, can pose a serious threat to water quality. This study attempted to evaluate Nmin content in grassland soils depending on soil type, land use, and farming intensity (i.e. livestock density). Regardless of observation period and natural factors evaluated, both land use and grassland use had a significant effect on mineral nitrogen content in the 60-90 cm soil layer. The lowest nitrogen content was shown in grassland mineral soils, whereas the cultivation of both maize and mixed cereals promoted greater accumulation of this nutrient in the soil profile at the depth of 60-90 cm. Mineral nitrogen content also depended on the use of grassland ecosystems. In mineral soils, the highest amounts of Nmin were found in hay grasslands, whereas in organic soils - in hay and pasture grasslands. The lowest amounts of nitrogen in the investigated soil layer were observed in alternate grasslands. It was also revealed that strong significant correlations exist between livestock density and the content of mineral nitrogen in the 60-90 cm soil layer. Calculated regression equation describing those relationships can help the farmer to plan sustainable fertilisation depending on livestock density of his farm.