Sprayer Performance in Relation to Air-Assistance
Spraying of pesticides for crop protection entails some physical wastage of pesticide to the surroundings either by missing or overdosing. An efficient spray requires deposition of spray droplets both on upper as well as on under side of the leaves, so that pests do not get a chance to survive. Incorporation of high speed air stream into the droplet spectrum, produced by hydraulic nozzles, facilitates in transporting and depositing the droplets in different parts of the canopy, especially on the underside of leaves, more effectively and uniformly. The experiments were planned and conducted by a tractor mounted air-assisted sprayer to study the influence of air-assistance along with forward speed viz. 0.85, 1.36 and 1.93 m/s and vegetable crop canopies (brinjal, chilli and bittergourd) on spray deposition and off-target losses. The crop canopy was virtually divided into three planes, top, middle and bottom and observations were taken on these planes at both upper side and under side of the leaves. The experiments were repeated using the same sprayer but without air-assistance. Based on the results of the study it was concluded that deposition of spray droplets on both upper and under side of canopy improved with air-assistance. The droplet size without air-assistance was slightly more on upper side of the top surface of the canopy than was found with air-assistance. The droplet density and droplet size obtained on under side of the canopy were found to be less than that on the upper side. Droplet density on both upper and under side of the canopy decreased with increase in LAD and forward speed. Leaf area density did not influence the droplet size significantly. Spray drift in case of sprayer without air-assistance was slightly higher than with air-assistance while the runoff was less. Overall, the air-assisted sprayer gave a superior performance in terms of effective spray in all canopies than the sprayer without air-assistance.