Conventional Hydraulic Nozzles Used for Orchard Applications

A conventional, axial‐flow, air‐blast orchard sprayer was used to make applications to the outside row of a semi‐dwarf apple block. Fluorescent tracer was applied at the same rate using either disc‐core nozzle sets or air‐induction nozzles fitted with flat‐fan tips. The experiment included measuring the percent area of spray coverage on leaves after three variations in spray application method. Each of the variations used a different type of nozzle on the same conventional, axial‐fan orchard sprayer. The three nozzle variations were a Spraying Systems D3‐25 nozzle set, a Spraying Systems D4‐25 nozzle set, and a TurboDrop 02 (TD02) air‐induction nozzle set. Canopy spray deposits, downwind sedimentation, and airborne spray losses were also measured following treatment on the inside half of the outside row using D4‐25 nozzles or TD02 nozzles. The small droplet spectrum D3‐25 nozzle set produced the highest leaf surface coverage on both upperside and underside surfaces at 2.0 and 3.0 m heights in the canopy. The upperside leaf surface coverage produced by the D3‐25 nozzle was only somewhat greater than the TD02 nozzle. It was, however, significantly higher than the D4‐25 nozzle set at the 3.0 m height. Conversely, the underside leaf surface coverage produced by the D3‐25 was significantly greater than the TD02 nozzle set at both 2.0 and 3.0 m heights and not statistically different from the D4‐25 nozzle set at the lower sampling height. There were relatively few differences in canopy spray deposits between the D4‐25 and TD02 nozzle sets. The TD02 treatment produced the lowest downwind sedimentation deposits on targets 8 to 32 m from the edge of the orchard. The D4‐25 produced approximately three times higher deposits up to 9 m above the ground than the TD02 treatment on passive nylon screens located 8 m downwind from the edge of the orchard. The D4‐25 treatment produced significantly higher airborne deposits on elevated, high‐volume, air sampler filters out to 64 m. At 128 m, sedimentation and airborne deposits were similar for the D4‐25 and TD02 treatments.