Ontology-based Simulation of Water Flow and Phosphorus in Organic Soils used for Sugarcane.

A nutrient management support tool has been developed to help Florida citrus growers optimizing yields in an economically effective manner, while greatly reducing the environmental impacts associated with excess fertilizer and water applications. It utilizes a unique data modeling environment where soil-plant-nutrient processes are represented as database objects in an ontology-based simulation (OntoSim). Our aim was to expand the OntoSim to model hydrology, nutrient cycling and crop growth on organic soils in Florida sugarcane production where water table control systems and phosphorus (P) fertilization contribute to nutrient enrichment of the Everglades by releasing highly P enriched farm drainage water from the Everglades Agricultural Area (EAA). The processes for soil organic matter decay, which are based on the mathematical framework of the CENTURY model, are included, as well as dynamics of inorganic P. Sugarcane growth and its nutrient uptake are modeled according to a modified version of the DSSAT-CANEGRO model. The water balance model allows simulating an impermeable layer in the soil profile to model a perched water table and vertical and lateral drainage flux in the saturated zone. This was essential to simulate water table control systems commonly managed on Florida sugarcane fields where sub-irrigation and open ditch drainage are used. A sensitivity analysis revealed that hydrologic and water quality outputs are within expected parameters and most sensitive factors could be identified that drive P flux on organic soils. We tested and validated the model using a long-term record of water quality data - canal levels, rainfall, discharge, and water P concentrations - from a farm in the EAA. By assembling the information into OntoSim, we were able to simulate the fluctuation of water table height within the site and estimate lateral drainage flux from and to an adjacent canal with more than 70% accuracy in most seasons.