Phosphorus loss from grassland soils : implications of land management for the quality of receiving waters.

Heathwaite, A. Louise and Griffiths, P. and Haygarth, P. M. and Jarvis, S. C. and Parkinson, R. J. (1997) Phosphorus loss from grassland soils : implications of land management for the quality of receiving waters. In: Freshwater contamination :. IAHS Publications, Wallingford, pp. 177-186. ISBN 0901502201

Abstract

Transfer of P from grassland soil to water was studied using two complementary field experiments. In the first of these, P transfer in surface runoff from grassland soils receiving different amendments of fertilizer and manures, under controlled rainfall conditions, was considered. In the second experiment, 1 ha-sized grazed plot lysimeters were used to separate different hydrological pathways into surface and artificially drained pathways. It was found that fertilizer and manure additions were both direct sources of P transfer, and that discrete single storm events were important in this process. On the grazed plot lysimeters, annual P export is estimated to be in the region of 2-3 kg P ha" 1 year 1, but is reduced by about 30% in the presence of artificial drainage. Although soluble ( < 0 . 45 um) inorganic forms of P dominate P loss from grassland, organic and particulate forms are also significant, especially in subsurface hydrological pathways. It is suggested that P transfer from grassland soils is definitely not solely related to soil P status, rather it reflects interaction of climate, hydrology, fertilizer management, grazing management and farm waste management. Although more research is needed before full control strategies can be suggested, the strategic timing of fertilizer and manure amendments at times of the year to avoid runoff may be appropriate in sensitive catchments.