Obtaining Uniform Distribution of Granular Fertilizers with a Spinner Disc Spreader in Variable Rate Scenarios

Abstract

Broadcast fertilizer distribution through spinner-disc spreaders is a widely accepted practice throughout the agricultural industry due to ease of use and low economic impact on producers. Typically, operators can apply pre-mixed granular fertilizer blends of nitrogen, phosphorus and/or potash. The ability to independently-meter multiple fertilizer products at variable application rates allow for site-specific management of in-field fertility. Fertilizer granules of various sources and densities possess different physical and aerodynamic properties when being spread. The purpose of this study was to evaluate the effect of fertilizer composition on distribution uniformity between independently metered and blended fertilizer sources, and determine the effect of metering type on spread of multiple products. A spreader with a dual bin, and the ability to independently meter two products onto spinner-discs was used for this study. Prior to spreading fertilizer, particle analysis determined that the bulk density of diammonium phosphate (DAP), muriate of potash (KCl), and a blended fertilizer (10-26-26) were 1009, 1105, 1025 kg/m3, respectively. All three fertilizer sources were broadcast and nutrient distributions determined. Specifically, the DAP components of the patterns were analyzed for any changes across all three fertilizer sources. DAP only spread patterns differed from that of the independently metered and the blended mixture, while the independently metered and blended fertilizer patterns were almost identical. Pan collection test results showed independently metered DAP and potash spread patterns were not significantly different than the blended mixture. These results indicate that there is a need for in-field spreader adjustments during a variable rate scenario.