Uneven fertiliser distribution can reduce yield and crop quality. Tray testing ensures even spreading across the spreader’s full bout width, improving nutrient efficiency and return on investment. To perform a tray test, place trays at 0.25?m intervals across the bout width (e.g., 48 trays for 24?m). Use trays with baffles to prevent granule bounce and align them in a straight line in a long, uninterrupted field section. Drive the tractor at a steady speed over the trays and continue spreading beyond them. Weigh each tray’s contents individually and enter the values into Excel or a calculator. Calculate the mean and standard deviation (SD), then compute the coefficient of variation (CV = SD/Mean × 100). A lower CV indicates more uniform spreading, which helps ensure consistent nutrient delivery, better crop performance, and more sustainable fertiliser use.