Spray Deposits and Ground Losses when Using a Self-propelled Sprayer in Greenhouse Applications

The paper reports the results of some experimental tests aimed at evaluating the performances of a prototype of self-propelled sprayer useful for pesticide application in greenhouses. The sprayer was equipped with one vertical spray boom fitted with Albuz ATR hollow-cone brown nozzles and the distribution profiles were assessed by using a vertical patternator equipped with 20 cmx20 cm metallic trays. The profiles were measured at varying nozzle spacing (35 and 50 cm), distance of the spray boom from the patternator (30, 40, and 50 cm), and working pressure (5, 15, and 25 bar). Their uniformity was assessed by computing a suitable "uniformity index", related to the average absolute deviations from the mean. The results showed high repeatability of the tests and that the vertical uniformity of the profiles was mainly affected by nozzle spacing. The best uniformity was detected when the spray boom was equipped with 4 nozzles 50 cm spaced, when the distance from the patternator was 30 or 40 cm, and when the working pressure was 15 bar. This sprayer setup was then tested in field by simulating a pesticide application on full developed tomato plants arranged in twin rows. The rows were sprayed on one side only and foliar deposits and ground losses were measured. The analysis of variance showed that 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 and foliar layer distribution, decreasing from top to bottom. Foliar deposits were also decreasing from external to internal layers: however, when spraying the twin rows from both sides as in an effective pesticide application, the differences among the layers should decrease and result not statistically significant. Finally, ground losses were quite high: they accounted for some 60% of the applied volume rate.