Efficiency and feasibility of Best Management Practices to reduce nutrient loads in the Carapelle agricultural basin, Italy

The Carapelle basin encompasses 506 km² of mixed terrain from plains to mountainous areas. Lithology includes clayey-limestone and limestone-marly units in uplands with sands, conglomerates, clays and alluvial terraces in plains. The intermittent-pool hydrological regime features seasonal low flows in summer and high flows during winter and early spring. Rainfall ranges from 450-800 mm annually with high-intensity, low-duration summer events. Agricultural land dominates with winter wheat as primary production, alongside olive groves and limited forest cover (7%). The basin is characterised by severe erosion areas exceeding 10 Mg ha⁻¹ y⁻¹ requiring targeted intervention.

To evaluate the effectiveness and economic feasibility of Best Management Practices for reducing nutrient pollution in agricultural watersheds while supporting EU policy objectives including the Water Framework Directive, Farm to Fork Strategy and European Green Deal targets for soil and water restoration by 2030.

• EU Common Agricultural Policy and Rural Development Programme (PSR Puglia 2014-2020) provide subsidies: €100 per hectare annually for conventional agriculture and contour farming, €322 per hectare annually for no tillage, and €6,000 per hectare plus €2,500 annually for 12 years for reforestation. 
• Unit costs include €222 per Mg for winter wheat sales, €25.70 per Mg for wood, €544 per hectare for wheat production operations, and €140 per hectare for fertilizer. 
• Community-level costs valued at €19.46 per Mg for soil loss replacement and €0.80 per kg for nitrogen. Investment costs for no tillage machinery upgrade at €6,000 per farm.

• Contour farming with fertilizer reduction (CFR) and no tillage with fertilizer reduction (NTR) achieved 16-17% reduction in nitrate-nitrogen in surface waters and 26% reduction in leached nitrate. 
• Organic nitrogen decreased 15-20% across all conservation scenarios. Total phosphorous loads reduced by 2-11% depending on practice. 
• At farm level, no tillage scenarios showed benefit-cost ratios of 1.66-1.67 for gentle slopes and 1.40-1.41 for steep slopes. 
• At basin scale, NTR showed lowest total costs due to reduced nitrogen loss values. 
• Community cost savings include reduced soil loss replacement costs (from €4.7 million to €3.3 million annually) and lower nitrogen loss valuation.

SWAT hydrological model configured with 20m Digital Ementation Model, 115 sub-basins and 451 Hydrological Response Units. Model calibrated and validated for streamflow, sediment and nutrients using continuous measurements from 2007-2011. Five BMP scenarios simulated based on EU Rural Development Programme measures and Good Agricultural Environmental Conditions standards. Economic analysis calculated at field level using literature crop yields and at basin scale incorporating Total Practice Costs, Soil Loss Costs and Crop Productivity Losses. Fertilizer reduction scenarios applied 20% reduction aligned with EU Farm to Fork Strategy targets.

Giovanni F. Ricci, Università degli Studi di Bari Aldo Moro, giovanni.ricci@uniba.it

Best management practices in Carapelle, Italy

Intensive agriculture drives land degradation and nutrient pollution across the European Union, with inappropriate tillage and excessive mineral fertilizer use contributing to soil erosion and water quality deterioration. In the Carapelle river basin in Southern Italy, researchers developed an integrated framework to evaluate Best Management Practices (BMPs) for reducing nutrient loads while assessing their economic feasibility for both farmers and the public sector.

The 506 km² Carapelle basin spans between the Apulia and Campania regions in Southern Italy, with elevations ranging from 120 to 1089 metres above sea level. Winter wheat covers approximately 75% of the agricultural area, with olive groves prevalent in lowlands and forests in uplands. The basin experiences Mediterranean climate conditions with seasonal hydrology characterised by summer drought and winter-spring high flows. Monitoring data collected between 2007 and 2011 revealed nitrogen surplus of approximately 49 kg per hectare per year, comparable to the EU-27 average but indicating significant pollution pressure on water bodies.

Five BMP scenarios were modelled using the Soil and Water Assessment Tool (SWAT): contour farming, no tillage, reforestation, and two additional scenarios incorporating a 20% fertilizer reduction aligned with the EU Farm to Fork Strategy. The analysis evaluated physical impacts on nutrient loads alongside economic costs and benefits at both farm and basin scales, considering EU Rural Development Programme subsidies and community-level costs including soil loss replacement and nitrogen value.

Results demonstrated that contour farming and no tillage alone increased nitrate leaching despite reducing soil erosion. However, combining conservation practices with 20% fertilizer reduction achieved approximately 20% reduction in nitrogen losses while maintaining economic viability for farmers through reduced input costs and available subsidies.