How to calibrate your fertiliser spreader - Ten steps to more accurate spreading
When was the last time you calibrated your fertiliser spreader?
If you ignore this crucial job you are throwing money away with wasteful application of an expensive commodity. If you don’t have a calibration kit you can get your local dealer to calibrate the spreader for you.
This shouldn’t cost any more than €250. It’s a good idea to have the spread pattern checked at least once every two seasons, and this is usually done using a tray test.
A tray test is simple. After laying the trays out across the machine’s spreading width, a run through the trays is made with the tractor and spreader as it would be operated in the field.
Fertiliser collected in the trays is then transferred into corresponding test tubes and the contents are recorded. From this data something called the Coefficient of Variation (CV) is calculated by measuring the variation in each tray from the average. The lower the CV, the better.
A CV of 10-15pc is acceptable and will prevent crop striping. However, surveys indicate that a lot of spreaders in use today have CVs of 30pc or more.
Research shows that improving the CV from 30pc to 10pc will bring a yield benefit of around 0.25t/ha in wheat. If the result of the first run is unsatisfactory, adjustments are made to the spreader settings until an acceptable CV is obtained.
These adjustments could involve any number of issues – worn vanes, incorrect spreader height or top link setting.