Precipitation, runoff and nutrient losses from cultivated Histosols in western Iceland

From May 2001 to June 2002, regular measurements were done on the volume of water runoff from the fields of the Agricultural University of Iceland’s farm at Hvanneyri, western Iceland. Precipitation and other weather factors were continuously monitored. The following components were analysed in the runoff water: total N, ammonia N (NH4-N), oxidized N (TON), phosphate (PO4-P), soluble phosphorus (TSP), K, Ca, Mg, Na, and S. Results show that nutrient runoff varied considerably over the year, highest in winter but low during the summer months. Losses of Ca, Mg, K and Na were relatively high, but N and P runoff was low considering that we are dealing with fertilized organic soils with a high content of soluble P in the top 10 cm and high total N in the whole soil profile. Results showed that major fluctuations and peak runoff events were confined to the winter months. Nutrient losses in relation to field management practices require further studies.