Modeling Water Movement Through a Florida Spodosol and Entisol Using Hydrus-2D.

Citrus production in Florida is the largest in the US, accounting for 63% of national production. Understanding water movement in sandy soils with low water retention is important for improved water uptake and conservation. Thus, irrigation management in Florida is key to improved citrus yields. A study was conducted on two soils, Candler and Immokalee fine sand, to measure and predict water movement patterns within a 0.5-m by 0.6-m simulation domain using drip- and microsprinkler-irrigation. Water movement was monitored using capacitance probes, gravimetric water content and bromide at 10-15 cm and 40-60 cm depth. Results indicate reasonably good agreement between measured and predicted values for water movement (R²>0.87, RMSE~0.013-0.078 mm) and Br movement (R²>0.63, RMSE~0.04-0.57 mg kg^-1) suggesting that a carefully calibrated HYDRUS-2D model could be used for irrigation decision support on Florida’s Spodosols and Entisols.

Key words: Citrus sinensis, Trickle irrigation, Water use, Tracer-bromide