MODELING EVAPOTRANSPIRATION PARTITIONING IN A SHRUB GRASS ALLEY CROP/

Improving intercropping requires a thorough understanding of resource, particularly water, between the plant species. Evaporative demand was modelled for the soil and the components of a shrub/grass intercrop p lanted in rows, by determining the energy balance of each component an d by distinguishing between sunlit and shaded foliage. Modelling was b ased on a light partitioning model and micrometeorological data from t he canopy. Stomatal conductance, necessary for estimating transpiratio n, was modelled as a function of photosynthetically active radiation ( PAR). This enabled the validation of the model with evapotranspiration measurements in the field, during 10 days. There was a good agreement between the measured and estimated fluxes, for both the soil/grass la yer and shrubs (r(2) = 0.95). The difference, less than 10% at a daily scale, between the measurements and the model was due to the difficul ty in estimating the flux transfer resistances, ie stomatal and aerody namic. The model enables the analysis of the influence of microclimate changes due to shrub development on grass transpiration.