Variable rate granular fertilization of citrus groves: spreader performance with single-tree prescription zones

A. Schumann; W. Miller; Q. Zaman; K. Hostler; S. Buchanon; G. Perkins; S. Cugati

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Variable rate granular fertilization of citrus groves: spreader performance with single-tree prescription zones

In: Precision Agriculture â05

Authors:

A. Schumann

A. Schumann awschumann@crec.ifas.ufl.edu

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W. Miller

W. Miller
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Q. Zaman

Q. Zaman
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K. Hostler

K. Hostler
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S. Buchanon

S. Buchanon
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G. Perkins

G. Perkins
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S. Cugati

S. Cugati
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Type:: Chapter

Pages:: 665â673

DOI:: https://doi.org/10.3920/978-90-8686-549-9_082

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Commercial variable rate technology (VRT) fertilizer spreaders for citrus are currently being implemented in Florida groves to improve profitability and reduce nitrate contamination of groundwater. Although VRT spreaders incorporate proven embedded controllers and tree sensors which permit changing fertilizer rates according to tree size, there is currently limited information on their performance characteristics in spatially variable groves. This study investigated the performance characteristics of a split-chain, spinner-type VRT spreader during fertilization of a commercial citrus grove. Six nitrogen rates (0, 134, 168, 202, 236, and 270 kg ha^-1 y^-1) were varied according to a prescription map developed from ultrasonically measured tree size information. Missing trees and one-year old reset trees were not fertilized with the spreader. Target fertilizer rates for 1,490 trees in an 8.1-ha experimental area were compared with actual fertilizer rates calculated from geartooth speed sensors monitoring the conveyor chain speed. Through classification and regression analysis, spreader performance and response times during transitions from zero or low fertilizer rates to high rates and vice versa were compared. In this grove, 73.1% of the fertilizer rate changes were required between single tree spaces of 5.3 m linear row distance, taking about 4 s to drive at 1.34 m s^-1. The spreader had an average on-off response time of â¤ 3 s, and an average rate changing response time of 2-5 s. Based on these data, the spreader design is not suitable for rapid fertilizer rate changes between single tree spaces, but could be greatly improved by substituting its hydraulic servo control valves with faster devices.

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Precision Agriculture â05

E-Book ISBN:: 9789086865499

Publisher:: Wageningen Academic

Print Publication Date:: 24 Oct 2005

Subjects
- Life Sciences
  - General
  - Agriculture & Environment

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Variable rate granular fertilization of citrus groves: spreader performance with single-tree prescription zones

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