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Modelling water dynamics in coffee systems: Parameterization of a mechanistic model over two production cycles in Costa Rica. Pablo Siles, Patrice Cannavo, Julie Sansoulet, Jean-Michel Harmand and Philippe Vaast
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Modelling water dynamics in coffee systems: Parameterization of a mechanistic model over two production cycles in Costa Rica. Pablo Siles, Patrice Cannavo, Julie Sansoulet, Jean-Michel Harmand and Philippe Vaast CATIE (Centro Agronómico Tropical de Investigación y Enseñensa), Turrialba, Costa Rica CIRAD (Centre de Coopération Internationale en Recherche Agronomique pour le Développement), Montpellier, France
Introduction Water is key issue in the coffee regions of Central America: • at plot level, complementarity /competition between coffee and various shade tree species • at landscape level, coffee located in mountainous areas (erosion) and rainy zones providing water for communities downstream. • Study with Inga (up to 6 species), predominant genus used in CA (70% shaded coffee)
Material and Methods • Trial established at CICAFE, Central valley of Costa Rica, Date : 1997 • Optimal ecological conditions • High altitude (~1200 m), temperate (~22°C) • high rainfall (>3000 mm), 3 dry Months • slope < 5% • Monoculture Coffee (MC): • Coffea arabica density : 5000 plants ha-1 • Agroforestry System (AFS) • Inga densiflora density : 277 trees ha-1 • Shade 40-55% • Intensive fertilization regime:
Transpiration Interception I. densiflora Interception Soil evaporation Coffee Gross Rainfall Runoff D Soil water stock Drainage Monitoring of water fluxes during 2 years GR = I + E + T + Rn + ΔS+ D I = GR - (Stemflow +Throughfall)
Transpiration : Sap flow (coffee & tree) Runoff Soil water content Stemflow: Inga and coffee
Influence of shade trees on throughfall Reduction in throughfall in AFS by 14.4% in 2004 and 7.6% in 2005
Influence of shade trees on stemflow • Higher stemflow in AFS (41%) could be explained by differences in architecture of coffee plants (40 cm taller, longer branches) in spite of lower coffee LAI • Low contribution of tree stemflow to the system (1% of rainfall)
Influence of trees on rainfall interception 74% higher in AFS 18% higher in AFS
Transpiration I. densiflora Interception Soil evaporation Coffee Gross Rainfall Runoff D Soil water stock Drainage Order of magnitude of various components for 2005
Adaptation of Model “HYDRUS” Comparison of simulated (solid line) and observed (circles) soil volumetric water contents in the 0-30 and 60-90 cm soil layers in AFS with allocation of water uptake in the various soil layers according to root density 0-30 cm soil layer in AFS 60-90 cm soil layer in AFS
Water drainage (in mm d-1) at 200 cm soil depth in AFS Cumulative values in AF system over wet season
Conclusion • Shade trees modify the coffee architecture resulting in increased coffee stemflow and a lower throughfall • Runoff was decreased in AFS due to coffee architecture and litter cover, hence less soil erosion and better water quality • Lower runoff offsets higher interception in AFS, hence a higher infiltration in AFS • Higher transpiration in AFS slightly lowers drainage in AFS • The soil water content simulated adequately by the Hydrus model (one the first time this model is used in agroforestry) • Sound basis to estimate the amount of water drainage and hence nutrient leaching (nitrate) • No OVERGENERALIZATION, present AFS with only one tree species (Inga), Andosol (fast infiltration) and high rainfall regime (>2500 mm). • The challenges are to use this approach 1) in more complex systems and 2) in conditions of lower precipitation and different soils (currently underway in India) and 3) upscaling.