Organic household wastes as a nitrogen source in leek production

Composted and anaerobically digested organic household wastes were evaluate d as N sources in leek (Allium porrum L.) production in an incubation exper iment without plants and in an outdoor frame with plants. Their N-fertilizi ng values were compared with that of chicken manure. Both experiments were conducted on four soil types (sand, two loams and a clay). After 168 days o f incubation the percentage of inorganic N of total N applied was 40-60% fo r slurry, 15% for compost and 20-30% for chicken manure. Only in treatments with chicken manure was net N mineralization achieved in all four soils at the end of incubation. In the frame experiment, between 5 and 20% of the s lurry N, 1% of the compost N and 6% of the chicken manure N was utilized by the above-ground leek crop. Slurry gave 1-20 Mg ha(-1) higher leek fresh w eight yield than did compost or chicken manure, The highest fresh weight an d N yields were achieved on the finer textured loam. The experiments showed that the amounts of plant-available N from slurry or compost were too smal l to support a leek crop with a high N demand towards the end of the growin g season.