In field experiments at six different sites in Sweden, leeks ere fertilized with farmyard and green manures. The sites were both at farms with ecological vegetable production and at research stations of the Swedish University of Agricultural Sciences. Two of the manures were combined with raised beds and mulching with black plastic film and grass/legume material in order to study the effect of these management practices in relation to the effects of the manures on N availability. Net N mineralization was determined by measurements of N uptake in leeks and of changes in mineral N content in the soil.