BERAS Work Package 2

Organic farming is often considered as one solution to reduce eutrophication of the Baltic Sea. However, the efficiency of organic agriculture in reducing nutrient leakage from primary food production to the aquatic environment is still questioned. The most crucial part of organic agriculture for reducing nutrient leakage is nutrient manage-ment in the crop rotation. Nutrient balance studies showed that ecological recycling agri-culture (ERA) had lower nutrient surplus and thus, lower potential of leakage (this report and Granstedt and others, 2004). However, direct measurements of nutrient leakage in ecological agriculture are scarce. Bergström and Kirchmann, 2000 reviewed the available literature on nitrogen leakage in organic agriculture and concluded that organic agriculture seems to have lower nitrogen leaching per hectare than conventional systems but differences were small and they were sensitive for small changes in either production system. The nitrogen leakage per mass of produced crops was higher in organic agriculture. They summarized, that nitrogen leakage is more a question of nitrogen ma-nagement, e.g. crops and crop rotation, than of production system. They believed that a decrease of nitrogen leakage can be achieved by opti-mizing the conventional system. However, Bergström and Kirchmann, 2000 did not consider differences of different organic systems. ERA is a nutrient extensive system based on an animal density adjusted to the own fodder production on each farm unit, which has a potential of low N-leakage (Granstedt and others, 2004). In this report we quantify nitrogen and phosphorus leakage on three ERA farms in the BERAS project. The study is based on direct measurements of nitrogen and phosphorus concentration in drainage water and water flow measurements. The results are compared with calculated standard leakage as reported to the HELCOM PLC-4 repor