Legume cover crop management and organic amendments application: Effects on organic zucchini performance and weed competition

Abstract In organic farming it is crucial to reach the best compromise between yield and sustainability of agronomical strategies. To this end, this two-year study evaluated the effects of legume cover crop management (no cover; vetch grown as green manure; roller crimped vetch) and organic amendments (no fertilizer; compost; animal manure; digestate fertilizer) application on organic transplanted zucchini and weed biomass productions, N dynamics, N balance and competitive interactions. In the first year, the vetch incorporated as green manure treatment showed the highest zucchini yield and weed biomass, as well as the highest crop N uptake reduction in presence of weeds. The roller crimped cover crop showed a decrease in weed biomass by more than 65% compared to green manure, and higher productivity than the no cover treatment. Animal manure and digestate fertilizers showed the highest yield, soil mineral N contents and crop N uptake, even if no variation in competitive ability was recorded. Conversely, the second year showed the potential limits of the roller crimping technique under cooler conditions, implying a reduction in zucchini yield performances and competitive ability. Among the experimental fertilizers, the digestate showed comparable results than commercial fertilizer for yield, but significantly higher than N0 (by 31%) and, when combined to vetch management, also in terms of N balance. This study illustrates the effectiveness of combination of different agronomical strategies to obtain adequate yield and weed impact reduction.