Katrijn Baetens

The Influence of Operator-Controlled Variables on Spray Drift from Field Crop Sprayers

Spray drift can be defined as the quantity of plant protection product that is carried out of the sprayed area by the action of air currents during the application process. This continues to be a major problem in applying agricultural pesticides. The purpose of this research is to measure the amount of sedimenting drift from a horizontal boom sprayer for different (drift reducing) spray application techniques under field conditions and to compare the results with the results from a reference spray, taking into account variations in meteorological conditions during the field drift experiments. Field drift measurements were performed for several combinations of nozzle type (standard flat-fan, low-drift, air inclusion) and size (ISO 02, 03, 04, and 06), spray pressure (2.0, 3.0, and 4.0 bar), driving speed (4, 6, 8, and 10 km h-1), and spray boom height (0.3, 0.5, and 0.75 m ) according to ISO 22866 by sampling in a defined downwind area at 24 different positions using horizontal drift collectors. The reference spray was defined as a standard horizontal spray boom without air support, a spray boom height of 0.50 m, a nozzle distance of 0.50 m, ISO 110 03 standard flat-fan nozzles at 3.0 bar (1.2 L min-1), and a driving speed of 8 km h-1, resulting in an application rate of approximately 180 L ha-1. Nozzle type as well as spray pressure, driving speed, and spray boom height, have an important effect on the amount of spray drift. Larger nozzle sizes, lower spray pressures and driving speeds, and lower spray boom heights generally reduce spray drift. Concerning nozzle types, air inclusion nozzles have the highest drift reduction potential, followed by the low-drift nozzles and the standard flat-fan nozzles. Drift results are closely linked with droplet size characteristics of the sprays.

Drift from Field Crop Sprayers Using an Integrated Approach: Results of a Five-Year Study

Spray drift continues to be a major problem in applying agricultural pesticides. This article summarizes the results of a five-year study of drift from field crop sprayers using a unique integrated approach. Indirect (spray quality and wind tunnel measurements) and direct (field) drift experiments were performed, and drift models were developed to study the effect of spray application technique, droplet characteristics, buffer zones, meteorological conditions, spray liquid properties, border structures, and crop characteristics on drift from field crop sprayers. It was found that indirect drift measurements can be a valuable alternative to field drift experiments. A validated 3-D computational fluid dynamics (CFD) mechanistic drift model was developed, which can be used for a systemic study of different influencing factors. This model was reduced to a fast 2-D diffusion advection model, which is useful as a hands-on drift prediction tool. From the experiments as well as from the models, the fraction of small droplets and the spray boom height were found to be the most influential spray application factors. Moreover, meteorological conditions as well as crop characteristics have an important effect on the amount of spray drift, which can be reduced significantly using intercepting screens or buffer zones. From this study, drift protocols, data, and models are made available, which help to understand and reduce the complex phenomena of spray drift.

Effects on pesticide spray drift of the physicochemical properties of the spray liquid

This research was on the effect of the physicochemical properties of the spray liquid on pesticide spray drift. Ten pesticide spray liquids with various physicochemical properties were selected for study. Some of these spray liquids were also examined with the addition of a polymer drift-retardant. In the first part, laboratory tests were performed to measure surface tension, viscosity, evaporation rate and density of the spray liquids. Subsequently, drift experiments were performed in a wind tunnel. From the results it was found that the dynamic surface tension is a major drift-determining factor, and also that the addition of a polymer drift-retardant can reduce drift significantly by increasing the viscosity. Drift reduction was found to be less effective with spray liquids of emulsifiable and suspendable formulation types than with spray liquids of water-dispersible granules and powders.