Profitability of erosion control with cover crops in Montilla-Moriles vineyards, Spain

The Montilla-Moriles PDO encompasses 5,000 hectares of vineyards with an average farm size of 2.3 hectares. The terrain features laminar soil structures with slopes requiring consideration for erosion management. The climate brings high-intensity rainfall events in autumn and spring that cause significant soil wash-away, with gullies being typical features of the landscape. Most vineyards use traditional management without trellis systems, which complicates cover crop implementation. The average vineyard operates on moderate slopes with trellis systems and no irrigation for modelling purposes.

To compare the profitability and cost-effectiveness of three soil management scenarios (conventional tillage, temporary cover crops, permanent cover crops) in Montilla-Moriles vineyards, incorporating both private on-site erosion costs borne by farmers and social off-site costs borne by society, to inform policy decisions about agri-environmental subsidies for erosion control.

• Current grape price of €0.30 per kilogram renders small winegrowers unprofitable considering all costs, though yields cover variable costs. 
• A Social Cost-Benefit ratio of 1.41 demonstrates no competitive advantage for the industry; minimum grape price of €0.41 per kilogram would be needed to achieve competitiveness. 
• Management cost increases for cover crops are 2.3% (temporary) to 4.5% (permanent) of variable costs: temporary cover crops add €66 per hectare, permanent cover crops add €126 per hectare. 
• The Agri-Environment Measure payment of €95 per hectare for organic producers maintaining cover crops on slopes above 20% covers at least the management costs for temporary cover crops. 
• From a private perspective only, changing management to cover crops is unprofitable despite subsidy payments.

Permanent cover crops reduced erosion rates substantially from 7.14 tonnes per hectare per year under conventional tillage to 1.64 tonnes per hectare per year. This translates to social erosion cost savings of €278 per hectare annually when considering off-site damages to infrastructure and environment. Temporary cover crops showed higher erosion rates than bare soil (9.53 versus 7.14 tonnes per hectare per year), possibly due to slope and rainfall event interactions. From a social perspective, permanent cover crop management saves more than it costs. Environmental benefits include improved soil organic carbon, aggregate stability, nutrient retention (60% reduction in loss), nitrogen fixation from legumes, and enhanced biodiversity and ecosystem services.

• Field surveys conducted across sixteen vineyards (eight for each of the two most common soil management techniques) to collect topographic, soil, cover and management information. 
• Daily climate data for 16 years (2000-2015) obtained from nearby weather stations. 
• The ORUSCAL tool calibrated using strategy incorporating soil moisture subfactor to assess erosion risk under different management scenarios. 
• Policy Analysis Matrix constructed using farm budgets adjusted for inflation to 2016 values, incorporating input-output prices, subsidies, and monetised erosion costs from literature. 
• Sensitivity analysis conducted on output prices, labour costs, variable machinery costs and erosion costs.

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Spanish vineyard study shows permanent cover crops savings

Montilla-Moriles is a Protected Designation of Origin (PDO) wine region in Andalusia, southern Spain, comprising approximately 5,000 hectares of vineyards managed by around 2,000 winegrowers. The region produces 276,000 hectolitres of white wine annually, with 90% sold on the domestic market. Vineyards are typically situated on slopes where bare soil management predominates, intensifying erosion and leading to significant losses of nutrients, organic matter, water and soil biodiversity.

The region experiences a semi-continental Mediterranean climate with an average annual precipitation of 604 mm and a mean annual temperature of 17.2°C. Soils are predominantly Luvisols and Cambisols with high carbonate content. Despite the erosion risk, only about 10% of vineyards currently use temporary vegetation cover during autumn and winter months. The economic situation for winegrowers is challenging as grapes are sold mostly to cooperatives at low prices (approximately €0.30 per kilogram), and the region faces competition from both Jerez wines and more profitable olive and almond orchards.

Research conducted through the VineDivers project compared three soil management scenarios using the ORUSCAL erosion model and Policy Analysis Matrix: conventional tillage (bare soil), temporary cover crops during autumn-winter, and permanent cover crops throughout the year. The study incorporated both private on-site costs borne by farmers and social off-site costs affecting broader society, including infrastructure damage and environmental impacts.