AERIAL SPRAY DEPOSIT RELATIONS WITH PLANT CANOPY ANDWEATHER PARAMETERS

Abstract

Relationships were developed to determine the effects of plant canopy characteristics and weather parameterson aerial spray deposits on cotton and cantaloupe foliage. Deposits were quantified both by fluorometric analysis of leafwashes and image analysis of water sensitive paper cards fastened to foliage. Deposit variables included deposit volume,percent of area covered, drop density (drops/cm2), and volume median diameter of deposited drops. In cantaloupecanopies, aircraft airspeed did not significantly explain the variation of any of the deposit variables. If underleaf depositionis important, the results indicate that ambient wind, especially that component parallel to the crop row, is beneficial.Higher ambient temperatures should be avoided if the drop density on the underside of leaves is important. The volumemedian diameter of drops deposited on the underside of leaves increased while the volume median diameter of dropsdeposited on the upper side of leaves decreased as with-row wind increased. In cotton canopies, deposit volume and size ofdeposited drops decreased as aircraft airspeed increased. Deposits on the underside of leaves at the TOP canopy levelincreased as with-row wind increased. Cross wind had a positive effect on spray deposits at both canopy levels. Increasedrelative humidity significantly increased deposits at the MID canopy level but had no significant effect at the TOP canopylevel. Deposited drops tended to be larger at the higher relative humidities. Deposits and size of drops deposited at the MIDcanopy level decreased as leaf area index (LAI) increased. Regression models based on measurements with the LAI meterhad similar form and R2 values as models based on manual measurement of LAI for cotton canopies.