Lower nitrogen supply gave better fruit quality in organic apples

The use of scab resistant apple varieties is the best way to prevent infections of apple scab (Venturia inaequalis). In 1995 the then 10 most promising resistant apple varieties for Denmark where planted at Research Centre Årslev, Denmark in an organic production system. Tree different cover crops where established in the allyways. Weed cleaning in the tree row was done mechanically and the trees were kept unfertilised. The annual shoot growth, nutrients in leaf sample, mineralised nitrogen in soil, content of water in the upper 50 cm soil, fruit yield and fruit quality were assessed. The best fruit quality due to colour, pest and disease damage was obtained in trees grown in permanent grass alley way system which gave a nitrogen sypply in the lower end of the optimum range. The resistance to apple scab was broken in most varieties. The varieties: 'Florina', 'Vanda', 'Redfree' and 'Retina' were less infected by apple scab