Plant parasitic nematodes may cause massive yield reductions in organic farming. Long rotations, often high amounts of weeds and a high frequency of legumes favour parasitic nematodes with a broad host range such as Meloidogyne spp. und Pratylenchus spp. The EU- Projekt OSCAR (Optimizing Subsidiary Crop Applications in Rotations) aims at improving soil conservation through minimum tillage combined with living mulches, cover crops and the use of suppressive composts. An experiment was set up with a rotation of 2-year grass-clover mix followed by wheat and then potatoes. Experimental factors were tillage, cover crops, and compost application. Until now Nematodes were sampled before and after wheat and before potatoes. Population dynamics over time were more affected by the time of the year than by the treatments applied. Sampling will continue will be presented Pratylenchus, Meloidogyne und Helicotylechus/Rotylenchus increased in the first year in all treatments. In the first half of the second year it appears that Meloidogyne has increased with no obvious effect of the treatments so far
