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Comparison of Variable-Rate Granular Application Equipment

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

Citation:  Paper number  031125,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.14930) @2003
Authors:   John P. Fulton, Scott A. Shearer, Timothy S. Stombaugh, Stephen F. Higgins
Keywords:   Precision agriculture, spinner disc spreader, Gandy Orbit-Air, Newton Crouch, New Leader, modeling, fertilizer and lime, potash, distribution patterns

The popularity of variable-rate technology (VRT) has grown but limitations and errors of this technology are generally unknown. Therefore, uniform and variable-rate (VR) tests were conducted to characterize distribution patterns at various rates and quantify rate changes for assessing the application accuracy of 3 VRT granular applicators (2 spinner spreaders and 1 pneumatic applicator). The characterized single-pass patterns demonstrated consistent shapes but deviated slightly from the desired patterns for two applicators at all rates. The simulated overlap multiple-pass summary statistics indicated that the three applicators performed satisfactorily with all but one of the CVs less than 20%. A majority of the CVs were less than 15%. The average application rates for 2 applicators were less than the desired levels for all tests. The third applicator under-applied at the low rate, over-applied at the high rate, but equaled the desired level at the medium rate. The overlap patterns for the spinner spreaders showed consistent peak levels at the center of the pattern, valleys on either side, and then tails on the ends that exceeded the desired levels. The pneumatic applicator overlap patterns indicated a problem with under-application at its center. The most uniform application occurred at the lower application tests for all applicators. Rate changes were much quicker for the two newer VR control systems. These results showed distribution plots are required along with CVs to calibrate applicators and correctly assess patterns while new technology has improved response time on VRT equipment.

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