Granular Fertilizer Spreader Swath Uniformity Achieved at Varying Target Application Rates

Abstract

This study measured the within-swath uniformity of both spinner and pneumatic spreaders over a range of material application rates commonly associated with precision agriculture schemes (25 to 200 lb/acre). Although small pan sampling is not appropriate for spreader rate calibration, results suggested that five of the spreaders delivered rates ranging from 50 to 200 lb/acre with reasonable accuracy. Four of the five spreaders also appeared capable of delivering an even lower rate, 25 lb/acre. Within swath coefficients of variability (CV) values ranged from 16 to 30% for the most uniform of the spreaders tested, and from 45 to 122% for the least uniform. When different products were applied by multi-bin spreaders, substantial fluctuation in measured product ratios occurred for bulk bin products. For a single spreader evaluated with a micronutrient bin, micronutrient application rates and variability were relatively consistent regardless of the co-applied bulk bin product rate. The type of spreader (spinner or pneumatic) did not appear to determine the uniformity of application. Our data suggests a within-swath CV of 20 to 30% as a reasonable uniformity target for granular fertilizer spreaders under North Carolina commercial farm conditions.