Validation of Growth and Nutrient Uptake Models for Tomato on a Gravelly South Florida Soil Under Greenhouse Conditions

The Soil and Water Assessment Tool （SWAT） has been widely used throughout the world to model crop growth and nutrient uptake in various types of soils. A greenhouse experiment was performed to validate the process equations embedded in SWAT for describing the growth and nutrient uptake of tomatoes in south Florida. The scaled growth curve of greenhouse-grown tomatoes was in close agreement with the theoretical model for field conditions, with the scaling factors being the maximum canopy height and the potential heat units. Similarly, the scaled leaf area index （LAI） growth curve and the scaled root depth curve for greenhouse- grown tomatoes agreed with the SWAT functions, with the scaling factors being the maximum LAI and maximum root depth. The greenhouse experiment confirmed that the growth of biomass is a linear function of the intercepted photosynthetically active radiation. The fractions of nutrients in the plant biomass under greenhouse conditions were found to be on the order of 60~ of those fractions observed in the field. Values of the initial P distribution （0.2 mg kg-1）, initial ratio of mineral stable P to mineral active P （50：1）, and initial ratio of humic N to humic P （2.4：1） were determined from soil measurements and can be used for field simulations. The conventional saturation-excess model for soil-water percolation was used to predict the movement of water in the top 10 cm of the greenhouse containers and the results agreed well with measurements.