AERIAL SPRAY DEPOSIT RELATIONS WITH PLANT CANOPY AND WEATHER PARAMETERS

Relationships were developed to determine the effects of plant canopy characteristics and weather parameters on aerial spray deposits on cot ton and cantaloupe foliage. Deposits were quantified both by fluoromet ric analysis of leaf washes and image analysis of water sensitive pape r cards fastened to foliage. Deposit variables included deposit volume , percent of area covered, drop density (drops/cm(2)) and volume media n diameter of deposited drops. In cantaloupe canopies, aircraft airspe ed did not significantly explain the variation of any of the deposit v ariables. If underleaf deposition is important, the results indicate t hat ambient wind, especially that component parallel to the crop row, is beneficial. Higher ambient temperatures should be avoided if the dr op density on the underside of leaves is important. The volume median diameter of drops deposited on the underside of leaves increased while the volume median diameter of drops deposited on the upper side of le aves decreased as with-row wind increased. In cotton canopies, deposit volume and size of deposited drops decreased as aircraft airspeed inc reased. Deposits on the underside of leaves at the TOP canopy level in creased as with-row wind increased. Cross wind had a positive effect o n spray deposits at both canopy levels. Increased relative humidity si gnificantly increased deposits at the MID canopy level but had no sign ificant effect at the TOP canopy level. Deposited drops tended to be l arger at the higher relative humidities. Deposits and size of drops de posited at the MID canopy level decreased as leaf area index (LAI) inc reased. Regression models based an measurements with the LAI meter had similar form and R-2 values as models barred on manual measurement of LAI for cotton canopies.