Variable–rate, Spinner–disc Fertilizer Applicator

The popularity of spinner spreaders for application of granular fertilizers and agricultural lime, along with increased interests in variable–rate technology (VRT), has raised concern about application accuracy and distribution of these 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 ASAE Standard S341.2. Uniform and variable–rate tests were performed to characterize the application variability of the spreader and to test the effect of rate changes via GPS control. Uniform and variable–rate application models were developed from the collected data. A sigmoidal function was used to describe increasing application rate changes, while a linear function described decreasing rate changes. Average transverse distribution patterns were used to model both high and low application rates. The resulting models were then compared to the actual distributions. The model was found to do a good job of characterizing uniform and variable–rate application patterns and therefore may be suitable for simulating variable–rate application errors.