Spray Penetration into Peanut Canopies with Hydraulic Nozzle Tips

The spray penetration into peanut canopies with single- and twin-row planting systems at three growth stages was investigated with four different types of hydraulic nozzle tips (flat fan, hollow cone, twin jet and air induction). The nozzles were operated at 276 kPa pressure, 6·4 km h−1 travel speed, and 0·5 m above the top of canopies. The canopy leaf area index (LAI) and height were measured for each test and correlated with spray deposits at the bottom and middle of peanut canopies. Spray deposits at the top, middle and bottom of canopies were determined with a spray mixture containing water and a fluorescent tracer. The concentration of spray samples were corrected with the calibration of the photo degradation of the tracer exposed to direct sunlight, under artificial shade and in a dark room. Plants with single- and twin-row planting systems received significantly different spray deposits within peanut canopies. For all four nozzles during the growth season, the spray deposits decreased dramatically from the top to the bottom of canopies, and also tended to linearly decrease as LAI increased. Compared to the flat fan nozzle at the bottom of canopies at 75 days after planting, the air induction nozzle produced 2·6 times higher spray deposits for single-row plants and 1·6 times higher spray deposits for twin-row plants. During the three growth stages, the air induction nozzle produced the highest mean spray deposit at the bottom of canopies, followed by the twin jet and then hollow cone nozzles. The conventional flat fan nozzle had the lowest spray penetration performance among the four types of nozzles.