Short-term and long-term effects of vegetable, fruit and garden waste compost applications in an arable crop rotation in Flanders

Substantial amounts of VFG-compost are produced annually in Flanders. Our objective was to analyse the effects of VFG-compost applications in a common crop rotation. Data from a long-term (1997 - present) field trial were analysed. Simulations with the RothC-model were performed to get a better insight into the dynamics of the underlying soil organic matter. VFG-compost applications (15 t.ha(-1) 3-yearly up to 45 t.ha(-1) yearly) can replace a substantial part of the mineral nitrogen fertilisation. Nitrogen recovery rates ranged from 6 to 22 %. Plots fertilised according to the nitrogen advice had comparable yields, whether this advice had been provided (partially) through VFG-compost or not. Long-term VFG applications resulted in carbon accumulation in the top soil. The RothC-model gave a good prediction of the carbon change with low to moderate VFG applications, but tended to overestimate the carbon change with high applications. The simulation results indicated that the carbon accumulation was mainly due to an increase of the more resistant carbon fractions. In the long term, compost applications increased the nitrogen supplying capacity of the soil, as illustrated by the gradual increase of the mineral nitrogen stocks in spring over the years. VFG-compost applications had a positive effect both on crop yields and soil organic matter. The RothC-model was used to simulate long-term effects, but its calibration should be improved for long-term compost applications.