Tillage and cover crop effects on weed management and community changes in organic tomato cropping system

The adoption of no-till practices in organic horticultural production has been challenged by an ineffective cover crop management and absence of season-long weed control. The objectives of our research were to determine the effects of tillage, cover crop residues management and weed control approaches on weed abundance, season-long suppression, diversity and weed community changes in tomato cropping system. The trial was conducted during 2015-2016 season under Mediterranean conditions (Pisa, Italy). The results showed the success of the combination of roller/crimper and flaming in inhibiting the re-growth of the clover(Trifolium squarrosum L.) and preparing a dead mulch in no-till plots (NT).However, weeds were able to re-grow shortly after transplanting in these plots and no decrease in weed abundance, as total weed cover, by the dead mulch was registered further in the seasonal though the clover controlled initially 70% of weed abundance. Among the weed species present, the dead mulch enhanced selectively the emergence of Artemisia vulgaris L. and Daucus carota L. When used as green manure in conventionally tilled plots (CT), the clover had no residual effect on weeds. Compared with CT, the soil cover of weeds in NT was 40% higher. Likewise, weed biomass at harvest time in NT was much more than CT and the resulting competition was highly noticeable on tomato plant biomass. Regarding weed diversity, NT increased weed species richness and induced changes in the weed flora during the season. It was well shown that no-till practices are challenging in fields with high weed seed bank and perennial weed species. In some conditions, a dead mulch may offer also the ideal growth conditions mainly of nutrients and humidity for some weed species. Effective cover crop suppression strategies are possible in organic conservation systems while good stands of high biomass at the right sowing and killing time remain crucial for a longer weed management