Comparison of different drift risk assessment means

Three contrasting drift risk assessment means were evaluated when predicting absolute losses of sedimenting pesticide drift from field crop sprayers namely  PDPA laser measurements, wind tunnel measurements (both indirect drift risk assessment means) and field drift experiments (direct drift risk assessment means).  In total, 90 PDPA laser measurements, 45 wind tunnel experiments and 61 field drift experiments were performed with 10 different spray nozzles at a pressure of 3.0 bar. The effect of nozzle size (ISO 02, 03 04 and 06) and nozzle type (standard flat fan, low-drift flat fan, air inclusion) on the amount of near-field sedimenting spray drift was studied.  The reference spray application was defined as a Hardi ISO F 110 03 standard flat fan nozzle at a pressure of 3.0 bar with a nozzle or boom height of 0.50 m and a driving speed of 8 km.h^-1 for the field measurements; conditions that were always used for the comparative assessment of the different investigated nozzle-pressure combinations.  In this paper, a comparison is made between the results obtained with the indirect drift assessment means and the direct drift assessment method to evaluate the potential of these three different drift assessment means.  Results showed that with the indirect risk assessment means (wind tunnel and PDPA laser measurement), driftability experiments can be made with different spraying systems under directly comparable and repeatable conditions and both methods are suited to permit relative studies of drift risk.  Moreover, based on these indirect drift measurements and a statistical drift prediction equation for the reference spraying, it is possible to come to a realistic estimate of field drift data at a driving speed of 8 km.h^-1 and a boom height of 0.50 m