A grass-clover ley may serve to build soil fertility. However, destruction of the sward may result in a high mineral N content in the soil profile in autumn. We have therefore investigated if non-inversion tillage is feasible for destruction of a grass-clover sward. We also examined how mode and timing of destruction would affect the N availability as reflected by total N uptake of the subsequent main crop leek (Allium porrum) and the residual mineral N. Early destruction in March appeared to be the least favorable option due to the highest residual mineral N content at values of total plant biomass and N uptake not higher than those obtained after late destruction of a repetitively mulched grass-clover sward. Non-inversion tillage proved to be successful for destruction of a grass-clover sward. It did not lower total plant biomass and N uptake by leek when compared to mouldboard ploughing. Grass-clover management history and time of destruction were decisive for the N availability.