Effect of the Nozzle’s Angle on Foliar Deposit in Greenhouse Treatments.

The paper reports the results of some spraying tests on full developed tomato plants, aimed at evaluating the performances of a self-propelled sprayer useful for pesticide application in greenhouses. The sprayer was equipped with one vertical spray boom fitted with 4 Albuz ATR hollow-cone brown nozzles, 50 cm spaced. Two nozzle angles with respect to the forward direction of the sprayer were considered: directly towards the crop (0°) and backwards (30°). Spraying pressure and forward speed were kept constant: 25 bar and 0.9 m/s, resulting in a volume application rate of 725 L/ha. The rows were sprayed with a water solution of food dye Red Poinceau on one side only and foliar deposits and ground losses were measured via a spectrophotometric technique. The results showed that the rotation of the nozzles didn’t improve the penetration of the spray inside the canopy, but increased, even if not significantly, the deposition on the external layer (+12%). On average, the vertical distribution of the foliar deposit was decreasing from the bottom to the top of the canopies, due both to the gravitational effect and the LAI distribution, decreasing from top to bottom. Foliar deposits were also decreasing from external to internal layers: however, when spraying the rows from both sides as in an effective pesticide application, the differences among the layers should decrease. Finally, ground losses were quite high: they accounted for some 44% of the applied volume rate, without significant differences between the two nozzle angles.