Test of an automatic rate control system for a centrifugal-type dry fertilizer spreader

A study was undertaken to investigate the accuracy of a commercial electron ic system for the control of dry fertilizer application rate on a centrifug al spreader The components of the electronic equipment, the logical sequenc e of the controller functioning and the test procedure are described. The s ystem performance was evaluated considering three fertilizers with three no minal application rates, varying the spreader forward speed in the range 6- 13 km/h and measuring the corresponding flow rates. The study was conducted under stationary conditions. The results show a good linear correlation be tween the fertilizer flow rate and the spreader work speed. The system accu racy, expressed by the distribution of the application rate error epsilon, was different for the three fertilizers tested. The optimal machine respons e was obtained with prilled urea (100% of samples affected with a +/-10% ap plication error), while the worst one occurred when using a compound of fer tilizers (only 77% of samples within the application error range +/-10%).