MODELING INDIVIDUAL NUTRIENT-UPTAKE BY PLANTS - RELATING DEMAND TO MICROCLIMATE

This paper proposes an approach for modeling plant uptake of individua l nutrients based on incident microclimatic variables and independent of water uptake. Current nutrient uptake models, though quite complex, have not been developed in a form directly applicable to nutrient man agement systems for greenhouse crop production. This paper proposes an approach for predicting plant nutrient use based on the assumption th at plant nutrient demand, as determined by photosynthetic rate, determ ines the required rate of nutrient uptake for optimal growth. This gen eral model allows specific models to be developed with direct function al relationships between individual nutrient uptake rates and incident microclimatic variables. A simple model is presented which applies nu trient demand directly to photosynthetic photon flux density.