Miljöeffekter av hästhållning

Horse numbers have increased greatly in Sweden in recent decades. The horse sector has great cultural, social and economic value and contributes towards maintaining an open landscape. It is important to develop these positive aspects of horse keeping, but there are also negative aspects that must be rectified in order to avoid potential problems and conflicts for the sector. For example, there is a risk of increased plant nutrient losses from outdoor areas used by horses. On cattle farms, such losses are known to occur mainly from areas of nutrient accumulation. In this screening of N and P levels at horse enterprises, soil samples were collected in early spring from 30 outdoor areas (all-weather yards, paddocks, grazing fields and free range areas) used by horses in central and south-western Sweden. Individual sub-areas represented different land use within each outdoor area. Samples were taken to 50 cm depth and analysed for total N, mineral N, HCl-P (easily and strongly bound P) and AL-P (easily extractable P). Stable managers also answered a questionnaire concerning e.g. feeding, dung clearance from outdoor areas, and the time horses spent in each outdoor area. A general linear mixed model was used to examine correlations between management system and soil variables, and between soil variables. Soil mineral N content was generally comparable to that in semi-intensively grazed leys on cattle farms. However, for individual areas the mineral N content was similar to that in feeding areas and shelters in free-range cattle production. This was also the case for AL-P in many of the areas. The different types of sub-areas had different degrees of nutrient accumulation (mainly of mineral N and AL-P at feeding and defecation areas) or nutrient depletion (of total N at water points). The free-range areas generally had higher AL-P than the grazing fields, partly due to the management system and partly to different duration of use during the year. Three management parameters were particularly important in determining the degree of nutrient accumulation: animal pressure (number of horse-hours per year and unit area), dung clearing frequency and the extent of outdoor feeding. High animal pressure and a high proportion of outdoor feeding showed significant correlations with nutrient accumulation. For defecation areas, this accumulation could be counteracted by frequent dung removal. This report closes with some hands-on recommendations for decreasing the risk of negative environmental effects caused by nutrient accumulation in outdoor areas for horses.