The increasing number of horses, especially in urban areas has made the phosphorus (P) load of exercise areas (paddocks) more and more obvious but there has been a lack of information regarding how to assess this load and what can be done to lower it. In the surface soil (1-2 cm) of areas that are affected by horse manure, like paddocks, we measured very high extractable P contents. When testing soils from these areas using a rainfall simulator we found a close correlation between the extractable soil P in the surface soil and the dissolved reactive P in runoff water. In a runoff treatment test trial we used ferric sulphate to treat paddock runoff water. The chemical dosage was carried out using a tube doser placed in a well. After ferric sulphate treatment the runoff was discharged into a sedimentation pond and then filtered in a sandbed. The chemical treatment was performed during one year and the reduction of the dissolved P and total P in the runoff was 95 % and 81 %, respectively. Our Agri-Environmental Programme has not been successful in reducing the total P status in our agriculturally loaded lakes. We suggest that the cost-effective chemical treatment of waters from the high P equine areas should be included in the programme. Also in other countries in the Baltic Sea catchment area reductions of P contents in waters from equine areas should be carried out
