Design, Fabrication and Evaluation of a Continuous Controllable Metering Device for a Fertilizer Applicator

Variable rate technology is a way to reduce the environmental effects of agricultural chemicals, including fertilizer. The present study developed and evaluated the accuracy of a control system for a fluted wheel-type metering device for a fertilizer applicator. The relationship between fertilizer flow rate, traveling speed, and the opening of the metering device gate was calculated. The equation was saved in the memory of an electronic control unit. A factorial experiment was used to evaluate the effects of traveling speed (3.5, 5, 6.5 and 8 km/h-1) and fertilizing rate (70, 100, 150, 250, 350 and 450 kg/ha-1) on the accuracy of fertilizing as the percentage of deviation between the actual and target rates. The results showed that the rate of fertilizing had a significant effect of less than 1% on the accuracy of the metering device output, but no significant effect was found for traveling speed. A maximum error of 8.2% was recorded for metering device output with a mean error of 2.21%. To evaluate system performance, it was simulated in a workshop. A fertilizer prescription map for a 180 m path with 20 m interval zones having successive fertilizing rates of 50, 100, 150, 200, 250, 200, 150, 100 and 50 kg/ha-1 was loaded into the electronic control unit. A factorial experiment with a split plot design was used to evaluate the effects of traveling speed (3.5, 5, 6.5, 8 km/h-1) and fertilizing rate (100, 150, 200 kg/ha-1) on the accuracy of the fertilizing rate as the percentage of deviation between the actual and target rates. The results showed that traveling speed had a slightly significant effect on the accuracy of output (less than 5%). The rate of error of the system was less than 4.51% and was acceptable.