Publications - Faculty - Recently Submitted Faculty Publications 2008
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Schumann - Citrus Industry Magazine
Technology in Citrus Production II: Tips for Fine-Tuning Variable Rate Fertilization
AW Schumann and HK Hostler, UF/IFAS CREC
Abstract. Crude oil prices recently reached new highs so fertilizer prices will continue to increase. Variable rate fertilization (VRF) is a precision agriculture tool capable of immediately reducing citrus fertilizer costs in increasingly non-uniform blocks, conserving non-renewable resources and protecting the environment. Slow VRF systems may show apparent fertilizer savings but the tree nutrition could be incorrect and misplaced. The important components for fine-tuning VRF response times and accurate performance are 1) the hydraulic valves which control the chain speed, 2) the type of computer controller and its features, 3) the type and quality of ground speed sensor, 4) the type of canopy sensor and the inclusion of a "look-ahead" function, 5) correct calibration of the VRF spreader and adjustment of sensor angles. The buyer can choose to customize the components and options when ordering the spreader and this article should help both manufacturers and growers to find the right combination. A recent study of VRF in a solid-set young Hamlin grove achieved a 31% reduction in fertilizer consumption due to non-fertilization of the gaps between tree canopies. These large-scale field tests have confirmed the advantages of VRF in Florida citrus without detrimental effects on tree nutrition.
