PHOSPHORUS RUNOFF FROM SMALL AGRICULTURAL CATCHMENTS UNDER DIFFERENT LAND USE INTENSITY

The study was carried out in the hydrologic year 2006 and comprised two small agricultural catchments in the Masurian Lakeland. Both catchments possessed very large water retention potential (presence of buffer zones and surface waters in the catchments) but they differed in the intensity of agricultural production. The study has demonstrated that the concentration of phosphorus in the surface waters flowing from the catchments ranged from 0.12 to 0.43 mg.dm(-1). The catchments were characterised by low indices of water overland flow (0.32-1.67 dm(3).s(-1)-km(-2)), which was a decisive factor shaping the runoff of phosphorus (from 0.013 to 0.060 kg.ha(-1)-year(-1). A subcatchment dewatered by a pipe drain system, which was used for comparison, had a water flow of 3.54 dm(3).s(-1)-km(-2) and exported much more phosphorus with its surface waters (0.39 kg.ha(-1)-year(-1)). The results obtained during our study emphasise an important role played by small landscape water retention elements in both catchments and the efficiency of buffer zones at a contact of water bodies and fields in reducing the runoff of biogenic substances, especially when agricultural production carried out on a given catchment is intensive.