Development of a Controller for Variable-Rate Application of Granular Fertilizer in paddy farming

Variable-rate application technology is an essential part of the precision farming that can solvethe economical and environmental problems associated with traditional farming practices in Korea. However,utilization of the technology has been limited by the lack of the development of a variable-rate applicator forgranular fertilizers. In this study a control system for variable-rate application of granular fertilizer was designedand fabricated with a F/G (Frequency generator) servo system and a discharger. Also, control performance anddischarge characteristics of the control system were evaluated. Results of the performance test showed thatthe uniformity of discharge amount in terms of the CV(Coefficient of variation) values for given rotationalspeeds of discharger were in the range of 11.23~2.94% for Super 21 (N:P:K=21:17:17), and 10.80~2.82% forShinsedae (N:P:K=22:12:12), respectively. It appeared that the CV values increased as the rotational speed ofdischarger decreased. The uniformity of rotational speeds of the discharger in terms of the CV values were inthe ranges of 0.51~3.06%. The uniformity of rotational speed improved as the input level of control signalincreased.