Variable-rate technology (VRT) adds complexity to application equipment, thereby confounding the assessment of applicator performance. The intent of this investigation was to assess the rate response of various VRT granular applicators: two spinner spreaders (A and B), and two pneumatic applicators (C and D). Variable-rate (VR) tests were conducted to quantify the rate response characteristics (delay and transition times) for the applicators. A sigmoidal function was used to model the rate response for five of the six tests. Applicator A exhibited a linear response during decreasing rate changes. Results indicated that only applicator B demonstrated consistent delay and transition times, enabling the use of a single “look-ahead” time for rate response time correction. Contouring of prescription maps increased the transition times for applicator D by enlarging the adjustment area between management zones. Rate changes were quicker for the two newer VR control systems, signifying advancement in hydraulic control valve technology. This research illustrates the need for standard testing protocols for VRT systems to help guide VRT software developers, equipment manufacturers, and end users.

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Notes/Citation Information

Published in Transactions of the ASAE, v. 48, issue 6, p. 2095-2103.

© 2005 American Society of Agricultural Engineers

The copyright holder has granted the permission for posting the article here.

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Funding Information

Funding for this project was provided through a special CSREES-USDA Grant titled, “Precision Agriculture: Development and Assessment of Integrated Practices for Kentucky Producers.”

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The investigation reported in this article (05-05-038) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.