Interactive effects of fertilizer particle-size distribution and spreader settings on application uniformity and particle segregation

Abstract Double-disc centrifugal fertilizer spreaders are widely used because of their high operational capacity and low cost for applying granular fertilizers. However, achieving adequate application uniformity remains a challenge. This study evaluated fertilizer distribution by examining transverse application uniformity and the intensity of particle-size segregation. The variables included fertilizer type, application rate, disc rotation speed, and vane shape, totaling sixteen treatments arranged in a factorial design. Transverse distribution data were analyzed to determine the coefficient of variation (CV) and the granulometric spread index (GSI). Results showed that effective application width depended on the interaction between fertilizer type and disc rotation speed. The fertilizer with the most homogeneous particle-size distribution (GSI = 16) produced wider effective spreading widths, exceeding 30 m. In contrast, the fertilizer with a higher initial GSI exhibited greater segregation across the spreading width, with the GSI increasing from 34 to 47. The surface area of fertilizer particles deposited along the spreading width also varied, and this effect was more pronounced for the product with initially higher quality. This study provides a detailed quantification of how fertilizer–machine interactions influence spreading performance, offering insights to improve broadcast fertilization accuracy and mitigate segregation-driven nonuniformity in precision agriculture.