1. University of Extremadura, Forestry School of Plasencia The role of trees for Nitrate leaching after Organic and Mineral fertilization ML López-Díaz, G Moreno, V Rolo

2. Introduction Underground water Agriculture Nitrate leaching Directive 80/788/CEE Directive 91/676/CEE Fertilization rate Irrigation systems

3. Introduction PROBLEM Nitrate leaching SOLUTION Agroforestry Systems Organic Fertilization Tree – pasture root systemGradual N mineralization LIXIVIATED NITRATE

4. Soil NitratePasture Fertilization Treatments Tree Aims

5. Materials and Methods Systems D  Bare soil P  Pasture S  Tree SP  Tree & pasture Fertilization NF  No fertilize L  Sewage Sludge M  Mineral Greenhouse experiment n = 6 120 pots: 20 cm Ø, 120 cm height Soil: pH 4.7; 1 g N kg -1 ; 10 g Organic C kg -1

6. Materials and Methods 1 2 3 4 5 Parameters analyzed Tree Basal DiameterPasture Production Nitrate Lixiviated Profile of Nitrate Content Rooting profile

7. Results & Discussion NO 3 - Content in the Soil Profile NO 3 -, mg / Kg soil Depth, cm Systems D  Bare soil P  Pasture S  Tree SP  Tree & pasture Depth, cm NO 3 -, mg / Kg soil Fertilization Treatments NF  No fertilize M  Mineral L  Sewage Sludge

8. Results & Discussion Nitrate Lixiviation and Fertilization Rates Fertilization Nitrate, g /m 2 Fertilization Treatment 2006 2007 Date Nitrate, g /m 2 Fertilization Treatments NF  No fertilize M  Mineral L  Sewage Sludge

9. Nitrate Lixiviation and Systems Results & Discussion System Nitrate, g /m 2 2006 2007 Fertilization Date Nitrate, g /m 2 Systems D  Bare soil P  Pasture S  Tree SP  Tree & pasture

10. Results & Discussion Root system Tree Pasture

11. Results & Discussion Production

12. Conclusions The use of agroforestry systems are a good tool to control the nitrate leaching adjusting properly the fertilization rate to minimize the competitive effect between vegetation layers

14. THANKS FOR YOUR ATTENTION Victor Rolo