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VRT Citrus Test Plot Applications of Granular Fertilizer

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  031127,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.15022) @2003
Authors:   William M. Miller, A. Schumann, and S. Buchanon, Sr.
Keywords:   best management practices (BMPs), fertilizer, GPS, GIS

A key component in precision agriculture is exact delivery of liquid and solid materials to sitespecific locations. For Florida citrus, one major fertilizer component is nitrogen which typically is required at a maximum suggested yearly rate of 269 kg/hectare (240 lb-N/A) for orange trees >7 years old. However, over-fertilization can produce groundwater contamination through nitrate leaching. Addressing this concern, Florida growers are in the throes of implementing best management practices for various citrus growing areas. The application rates, as well as the frequency and seasonal timing are key components. A 16.2 ha (40 acre) field trial was initiated with a grower in the Ridge growing section of the state. As part of that project, prescription maps were developed for multiple applications throughout the season. A granular fertilizer unit with hydraulically powered split-chain outputs controlled from a MidTech Legacy 6000 controller was utilized. Data were collected on target and as-applied rates compensating for missing trees and resets. Additional mass balance data were obtained by weighing each load before spreader application. As small blocks of trees were involved, insight into the controller performance was obtained with respect to start-up, shut-off, and steady-state operations. Application rates for each of 43 blocks (42 test, 1 conventional) were compared for 4 tests conducted over the 2002-03 fruit season.

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