Fertiliser application performance of a variable-rate pneumatic granular applicator for rice production

To apply precision farming technology for rice production in Korea, a variable-rate pneumatic granule applicator with a 10 m long boom span was developed. The pneumatic applicator was equipped with relatively simple blow heads and a metering system. High accuracy, short response time, and uniform application patterns are required from a reliable fertiliser applicator for precision farming. The fertiliser application performance of the prototype applicator was tested and evaluated in the field. The application uniformity (coefficient of variation) in both the transverse and the longitudinal direction was in the range of 11.2–13.1% and 2.9–15.3%, respectively. The application accuracy of the prototype was quantified as a percentile ratio of the collected fertiliser amount to the desired amount per unit area. The application accuracy ranged from 81.9% to 97.4% at its working speed range. The response time (the time delay to reach a steady application rate when the application rate is suddenly changed) ranged from 1.5 to 3.0 s. The application uniformity and the response time were sufficient compared to previous studies. The time delay of the application rate setting caused an error of 0.5–1.0 m in the travelling direction. The application accuracy was not satisfactory due to slip characteristics of the driving motor at a low application speed, but was judged to be good enough for practical use.