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Nitrate leaching and N20 emissions in Coffea arabica systems in Costa Rica according to fertilization and shade management

Harmand J.M., Chaves V., Cannavo P., Avila H., Dionisio L., Zeller B., Hergoualc'h K., Vaast P., Oliver R., Beer J., Dambrine E.. 2009. In : Book of abstracts of the 2nd World Congress of Agroforestry, 23-28 August 2009, Nairobi, Kenya : Agroforestry, the future of global land use. Nairobi : WCA [Nairobi], p. 487-487. World Congress of Agroforestry. 2, 2009-08-23/2009-08-28, Nairobi (Kenya).

In optimum growing conditions for coffee in full sunlight and high fertilization in Costa Rica, full-sun coffee plantations were compared with coffee agroforestry systems in order to improve N fertilization and shade management, to optimize the production of coffee and associated trees while reducing nitrate (NO3-) leaching to ground water and N2O emissions. The inclusion of shade trees (Eucalyptus deglupta or Inga densiflora) in highly fertilized coffee plantations (250 kg N ha-1 yr-1) increased N accumulation in litter and permanent biomass, and slightly reduced water drainage, but it also reduced coffee production by 25 33%. As a result, the effect of the shade tree on NO3- leaching varied according to coffee production. These experiments showed a low efficiency of N fertilizer use by both coffee and trees and a large NO3- loss to groundwater, highlighting the need to reduce N fertilization in intensively managed shaded coffee systems. In a full-sun coffee plot, where N fertilizer was only provided in coffee pulp (150 kg N ha-1 yr-1), coffee berry production was very low (0.7 t dry matter [DM] ha-1 yr-1 during three years). Incorporating a legume tree stratum (Erythrina poeppigiana) increased berry production to 3 t DM ha-1 yr-1 for the same period without significant changes in NO3- leaching. Compared to the highly fertilized agroforestry system (250 kg N ha-1 yr-1), mean NO3- concentration in water drainage in this ¿organically¿ managed agroforestry system was reduced by three fold. N2O emissions were always insignificant compared to the losses though NO3- leaching. However these emissions were increased by high inputs of mineral N fertilizer and to a lesser extent by leguminous shade trees. Coffee producers should be encouraged to adopt environmentally sound N management, reducing N inputs and refining shade management based on a combination of leguminous and timber tree species. (Texte intégral)

Mots-clés : coffea arabica; costa rica

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