Determination of pin-roller parameters and evaluation of the uniformity of granular fertilizer application metering devices in precision farming

• It is proposed to determine the parameters of the pin-roller to increase the amount of fertilizer discharged and uniform distribution of fertilizer. • The uniform distribution of fertilizers was 10.36% at low speed of rotation of the pin-roller. • The function of the coefficient of variation decreases hyperbolically with increasing speed of rotation of the metering devices. • The resulting new pin-roller configuration can be used to apply fertilizer with variable speed. The application of fertilizer to the soil for the subsequent extraction by plants is a method to increase crop production. Fertilizer spreaders with an outer groove wheel (OGWFSs) have a large volume, and current metering devices are suitable for precision farming systems. However, the study of OGWFSs has shown that fertilizer metering is impaired due to sudden releases of fertilizer batches. Research has shown the performance advantage of using a pin-roller metering device whose pins are configured in the form of a truncated pyramid. This configuration not only provides highly uniform fertilizer discharge but is also advantageous for use with wet fertilizers and prevents clogging. In this study, an orifice was added between the pins to increase the working volume of the metering device and the amount of fertilizer discharge. The uniform distribution of the fertilizer particles and the amount of fertilizer discharge depends on the pin parameters. Therefore, the objective of this study was to determine the pin-roller parameters to increase the uniformity of the distribution and the amount of discharged fertilizer for variable-rate fertilizer applications. The pin-roller configurations that were investigated included the α angle, height of the roller pin, β angle, and radius between two pins for six right and left entry lines. As a preliminary test, 25 pin-roller configurations were designed and evaluated for fertilizer distribution at three rotation speeds of the metering device. The uniformity of the fertilizer distribution was evaluated in a laboratory test, and the coefficient of variation was used as an evaluation index. A compound fertilizer, N-P 2 O 5 -K 2 O, was used in the experiment. The results indicated that different pin-roller characteristics of the metering device had significant effects on the uniformity of the distribution and discharge capacity of the fertilizer. Based on the results of the preliminary test, a new pin-roller design was developed. The performance of this pin-roller was evaluated and compared to that of the OGWFS. The coefficient of variation and the amount of discharged fertilizer was evaluated at three different rotational speeds. The discharge capacity of the new pin-roller was not as high as that of the OGWFS at all rotation speeds of the metering device, but the coefficient of variation was higher for the pin-roller than the OGWFS at lower speeds. However, there was no significant difference in the coefficient of variation between the metering devices at higher speeds.