Excessive agro-chemicals are being used to enhance agricultural production to meet the food security challenge with increasing
population. Gaps or overlaps in the spraying patterns can result in under or over application of pesticides thus causing
environmental hazards. Conventional sprayers have uniform spray drift that is less effective for heavy canopies. Alternatively,
unmanned aerial system (UAS) are being used for crop monitoring and management (spraying insecticides/pesticides) however
proper spray height and nozzle opening needs investigation. In this study, a hexa copter unmanned aerial agro-chemical
spraying (UAAS) system was tested at different heights and nozzle openings to determine spray uniformity in the field
conditions. Operating height of 1.5 m, 2.0 m, 2.5 m and 3.0 m with spray nozzle opening (discharge rate) percentages of 25,
50, 75 and 100% were investigated for variable wind speeds ranging between 1 m/s to 5.8 m/s. Colored spray was used to get
impression of spraying droplets on sensitive papers placed for the purpose. Spray dots were counted to get the spraying
uniformity at different heights and wind conditions. The hexa copter UAAS system provided a good uniformity and coverage
area at operating height of 1.5 m with 50, 75 and 100% spray nozzle opening under wind conditions varying from 1 m/sec to
5.8 m/sec. This investigation provides a guideline to the farmers and service providers entering into the business of spraying
through UAS.
