Spray Penetration into the Citrus Tree Canopy from Two Air-Carrier Sprayers

Abstract

Field experiments were conducted to investigate The effect of sprayer type, application volume rate and airflow rate on spray deposition along depth of the citrus canopy. The trees were sprayed from one side using a tower sprayer with cross-flow fans and rotary atomizers (Curtec) at three spray volume rates and a tower sprayer with an axial-flow fan and hydraulic nozzles (Titan) at two spray volume rates and two airflow rates. Spray deposition was determined with fluorometry using cotton ribbons as targets within the entire canopy depth at two heights. For both sprayers, deposition decreased with canopy depth. The spray penetrated deeper at higher volume rates. The effect of volume rate became significant after about 1 m and 2 m depths for the Curtec and Titan sprayers, respectively. At high volume rate, mean depositions of the two sprayers were not significantly different at most canopy depths. In general, operating the Titan sprayer at lower airflow gave comparable mean deposition to that at normal (rated) airflow. The effect of airflow on spray penetration was significant beyond about 2 m depth.