Evaluating strategies for hedgerow implantation with native species in semi- arid agricultural areas. Implications for CAP environmental measures: a case study in southern Spain

In this work, vegetation growth was measured in hedgerows composed of trees, shrubs and bushes one year after planting in an experimental agricultural field in southern Spain. Seventeen hedgerows (4×20 m) were planted with different management strategies, resulting from combining: pre-planting tillage or no-tillage; deficit irrigation or rainfed; use of anti-weed mesh or not, and use of grow tubes or not. Hedgerow implantation costs were also calculated. Our results suggested that for semi-arid Mediterranean regions a straightforward strategy based on pre-planting tillage, rainfed conditions and without mulching and grow tubes, seems to work well, resulting in high survival rates (around 90%) and plant growth (0.32 m ² yr ⁻¹ increased canopy cover), with one of the lowest hedgerow implantation costs (€16.5 m ⁻¹ , for the current year). Deficit irrigation only resulted in a slight increase in plant survival (9.4% on average). Using plastic mulch resulted in higher plant growth but had higher implantation costs and raised concerns about the hazard of plastic contamination. Under our conditions, without herbivory, the use of grow tubes had no significant effect on plant survival and growth. The most straightforward strategy, same as above but without tillage, had the lowest hedgerow implementation cost, but a plant survival rate below 50%. However, even using this hedgerow management strategy, the implementation costs were higher than the financial support for implementing the eco-scheme for biodiversity areas (which includes hedgerows) under the current CAP in Spain. Therefore, better financial incentives for these environmental schemes are needed to maximize their beneficial impact.