SPRAY APPLICATIONS TO TOMATO PLANTS IN GREENHOUSES. PART 2: EFFECT OF SPRAY LANCE TYPE

Abstract

The present paper reports the results of some spray application trials carried out in a greenhouse with full developed tomato plants to assess foliar deposition, ground losses, and dermal operator exposure when using handheld high pressure spray lances and when walking backwards during treatments. Two spray lance types (conventional with one nozzle and Yamaho C-6 with two steel nozzles, each with two orifices) and two working pressures (10 and 20 bar) were taken into consideration. An experimental design with two factors (spray lance and pressure) was adopted, arranged according to a randomised block design with three replicates. Volume application rates ranged from 775 up to 1252 L/ha, but all data were normalised to 1000 L/ha. The results showed no statistically significant differences in the mean foliar deposition between the two spray lances and the two working pressures. However, the higher pressure improved significantly the deposit into the internal layer of the canopy (+57%), whereas the Yamaho C-6 spray lance produced a higher deposit on the external layer at any pressure. The greatest differences between external and internal layer were mainly concentrated in the middle and high parts of the canopy, where there were 55 007_Cerruto(557)_49 18-11-2009 11:59 Pagina 55 the highest values of LAI and number of foliar layers. The fraction of the applied volume rate on the ground was on average 25 percent and it was affected only by the pressure value: it increased from 21.7 to 28.7 percent when the pressure increased from 10 to 20 bar, due mainly to the contribution of the conventional spray lance under the sprayed twin-rows. Finally, neither pressure nor spray lance type affected significantly the dermal operator exposure. Upper limbs accounted for 51 percent of the total exposure, while trunk and lower limbs accounted for 24 percent each. The body parts more exposed were the left arm and the hands, but also relatively high was the deposit on the respirator, so operators should ever wear appropriate personal protective equipment.