Performance Assessment and Model Development of a Variablerate, Spinnerdisc Fertilizer Applicator

The popularity of spinner spreaders for application of granular fertilizers and agricultural lime, along withincreased interests in variablerate technology (VRT), has raised concern about application accuracy and distribution ofthese spreaders. This investigation was undertaken to assess the application distribution of a VRT spinner fertilizer spreader.Application distribution was assessed using a matrix of collection pans and following test procedures outlined in ASAEStandard S341.2. Uniform and variablerate tests were performed to characterize the application variability of the spreaderand to test the effect of rate changes via GPS control. Uniform and variablerate application models were developed fromthe collected data. A sigmoidal function was used to describe increasing application rate changes, while a linear functiondescribed decreasing rate changes. Average transverse distribution patterns were used to model both high and lowapplication rates. The resulting models were then compared to the actual distributions. The model was found to do a goodjob of characterizing uniform and variablerate application patterns and therefore may be suitable for simulatingvariablerate application errors.