Evaluation of Centrifugal Spreader Response to Variable Rate Application by Using Task File Data

Abstract

In the site-specific fertilization based on a variable rate prescription, the application accuracy and distribution of the spreader are the key points when it comes to applying fertilizer with centrifugal disk spreaders. The application error occurs mainly due to inaccurate position, the delayed response of the spreader to rate changes and application width errors across the management zones. This study aims to evaluate the application error occurring due to rate changes at management zone boundaries across the application width of the spreader. Towards this aim, a variable rate fertilizer application was performed using a centrifugal spreader. The performed task data that included a spatial field application file in ISO XML format was recorded from a dedicated in-cab terminal to generate the “as-applied” point map. A two-dimensional (2D) matrix method based on a 2D triangular distribution was used to generate the as-applied rate to examine if it results in more accuracy to assess the applied amount of fertilizer at intersections of the management zones. The resulted “as-applied” map, as well as the raw data one, were compared with the prescription map to extract absolute errors. Statistics of absolute error resulted from the comparison was assessed to examine the application accuracy. The mean value and standard deviation of the error for the distributed rate were 13.4 and 11 kg ha1. These figures were equal to 17.5 and 12.7 kg ha-1 for the error of the raw data “as-applied” map. Evaluation of covered area by the error in percentage also indicated a higher value for the raw data “as-applied” map than that for the distributed one.