Evaluation of Modified Variable Rate Granular Fertilizer Spreader for Spot-Specific Fertilization in WildBlueberry Fields

摘要

Existing commercial variable rate granular (VRG) fertilizer spreader change fertilizer rates in different management zones using global positioning system-guided prescription maps without considering unevenly distributed bare spots and weed patches inwild blueberry fields. The modifications in the existing spreader were made to control each pair of nozzles independently to avoid excessive fertilization in bare spots and weed patches. For this purpose, six pEye digital color cameras were incorporatedon the boom (6.21 m wide) in front of the tractor. Custom software installed in the computer was capable of processing the images to detect weeds, bare spots and blueberry plants in real-time and sending signals to the 8-channel variable rate controller(VRC). The VRC then sends the signal to solenoid valves, which in turn closes the pair of nozzles which is directly above the bare spot or weed patch.This study was designed to evaluate the modified VRG (MVRG) fertilizer spreader for spot application of fertilizer only in plant areas. A preliminary test using clay filler as the applied material was conducted at the selected field and 7.3 m wide and 60m long track was made in the field. Twelve artificial bare spots were made in the selected track using orange colored tarps. Equal numbers of weighed rat catchers (i.e. 12) were placed on artificial bare spots and grass. The MVRG fertilizer spreader wasoperated on variable rate (VR) mode (detection and no application of clay filler on bare spots). The rat catchers were collected and re-weighed. The same procedure was repeated for uniform (UN) application mode of the system. The results of paired t-test showed significant difference (p-value < 0.0001) in VR and UN application in terms of clay filler application on bare spots. The results also showed that VR and UN treatments were not significantly different (p-value = 0.58) in terms of clay filler application on green grass areas. Therefore, the MVRG fertilizer spreader could be used to save fertilizer and protect environment.