Effects of Sprayer Boom Height and Operating Pressure on the Spray Uniformity and Distribution Model Development

One of the most important factors easily overlooked yet seriously influencing the efficiency of chemical crop protection is the uniformity of liquid distribution on the entire sprayer boom. The uniform distribution of crop protection chemicals is an important element for achieving the maximum efficiency of chemical treatments with minimum costs and minimum environmental contamination. It is expressed in percentages by the coefficient of variation. Three types of nozzles (ST 120-04, IDK 120-04, and IDKT 120-04) were used for testing the uniformity of liquid distribution in laboratory conditions at three different operating heights, which are commonly adopted for pesticide treatments in Serbia (0.4, 0.5, and 0.6 m), and six different pressures within the range recommended by the manufacturer (200, 250, 300, 350, 400, and 450 kPa). All three types of nozzles had flat jets but IDK and IDKT nozzles were air-injector nozzles. The IDKT nozzles had twin jets with an angle of 60[degrees] between the two jets. An electronic spray scanner recorded the flow in the nozzles and the variation coefficient. The results of performed tests show significant differences between the set conditions. However, all nozzles had different coefficients of variation. The lowest coefficient was recorded with the air-injector nozzle, IDK 120-04. The flat spray nozzle ST 120-04 had the highest coefficient (from 8.545% to 7.226%) and all the others were within the acceptable 10% limits for the distribution uniformity. In general, a uniform distribution is enhanced with applications at greater heights and increased pressure does not ensure the constant distribution uniformity of injector nozzles in comparison with flat jet nozzles (in field conditions it is also necessary to take drift into account). At higher pressures, the distribution uniformity of air-injector nozzles is of poor quality due to greater liquid disintegration. The best possible application with this type of nozzle can be achieved at greater heights and medium application pressures. The results obtained in this research were used for the development of a mathematical model of CV changes in transversal distribution performed by the tested nozzles with respect to the pressure and sprayer boom height. The model can lead to better pesticide applications.