LandWISE 2015 Presenter, Miles Grafton
crops and pastures since upgrading to spreaders capable of spreading at increased, bout or swath widths. This issue is more prevalent where fertilizer blends of products with dissimilar ballistic properties are sown simultaneously.
The problem is more obvious when applicators have purchased modern top of the range twin disc spreaders with the ability to spread at an acceptable spread pattern at tram lines at or greater than 30 m. These spreaders have increased tram or bout widths of spread from 20 – 24 m, to greater than 30 m thus reducing the number of tram lines, increasing output and reducing trafficking of the crop or pasture.
Spreading at a tram line of 30 m requires a total spread pattern to be around 45 m, allowing for a pattern overlap of around 50%, to achieve the desired accuracy (Chok et al., 2014). Given that the spreading discs are around 0.5 – 1.5 m above ground level, then fertilizer particles must be discharged at some considerable speed.
In order to achieve an optimal even distribution, spreaders deliver 50% of the required amount of fertilizer on each side, which is overlapped with another 50% when the vehicle makes the next run in the opposite direction, or an adjacent run in a round and round spreading pattern. Therefore, the area closest to the border of the distribution area only receives half of the recommended rate as there is no pattern overlap and the desired fertilizer response, would then be reduced as if 50% of the desired rate on average has been applied.
Border spreading refers to the capacity to reduce the application distance on the side towards the border in order to minimize the amount of fertilizer applied outside the zone. Yield spreading compensates for the need to overlap by doubling the amount of fertilizer applied in the boundary side.
Product separation can be avoided by soil testing early, then addressing fertility issues by direct drilling or broadcast application prior to the crop establishing. Then use tram line application on crops for the one product intended to be side dressed during the crop life cycle.