Effectiveness of living mulch strategies for winter organic cauliflower (Brassica oleracea L. var. botrytis) production in Central and Southern Italy

In crop rotations, cover crops planted either before or concurrent with a main crop and maintained as a living ground cover (living mulch, LM) may provide many beneficial ecosystem services, and can be defined as agro-ecological service crops' (ASC). The objective of this research was to study the suitability of burr medic (Medicago polymorpha L. var. anglona) as an LM for organic cauliflower (Brassica oleracea L. var. botrytis) production in a Mediterranean environment. Two LM sowing times (early sowing - sowing concurrent with cauliflower transplanting versus late sowing - 3 weeks later) compared with a no living mulch control (LM-CT) were investigated in central Italy (Experiment 1), along with a comparison between two local cauliflower cultivars and a hybrid. In Southern Italy (Experiment 2), crop performance under two LM sowing times [20 days before cauliflower transplanting versus concurrent sowing (CS)] compared with a no LM-CT , with organic fertilizers and amendments allowed in organic farming as subplots, was assessed. In Experiment 1, no competition was observed between the late-sown ASC and the cash crop. An increase in crop nitrogen (N) uptake and weed mitigation was also determined in this treatment. There was a mixed response when comparing cultivar and LM interactions, with the hybrid cultivar in the late-sown LM producing the greatest yield. In Experiment 2, weather conditions had the greatest effect on crop response. However, an inverse trend between growth of the cash crop and the LM crop was observed in the CS treatment. A positive effect of LM introduction was found, particularly in altering the competitive relationship for N between the cash crop and weeds. In addition, yield results showed that, in LM systems, commercial organic fertilizers could be replaced with locally available organic fertilizers and amendments without any yield penalty. The effectiveness of LM strategies will thus depend on several factors: type of LM, cultivar of vegetable, weather, soils, length of growing season and ability to plant the cash crop into the LM. Initial research suggests the potential for burr medic as a LM for Mediterranean winter vegetable systems, but additional research is needed to ensure the viability of LM systems for longer periods of time.