Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 16, 1997
Publication Date: N/A
Interpretive Summary: In the U.S., most pesticides are applied as liquid sprays. The technology of inline injection of pesticides into the water line of agricultural sprayers eliminates problems such as left-over tank mix, application rate errors due to driving speed, and safety hazards from pouring pesticides that are inherent to single tank sprayers. With inline injection systems, pesticide injection rate can be easily varied while spraying; thus by measuring travel speed, the pesticide injection rate can be matched to actual speed. The injection system can also provide the precise amount of pesticide (or fertilizer) required for each field sub-section when precision farming methods are used. A transfer pumping system moves pesticides from the chemical company supply container to individual, small tanks on the sprayer. When spraying is completed, unused pesticide can be returned to the supply container for later use. Inline injection sprayers are subject to problems of non-uniform spray mixtures and lag time from when the pesticide is injected until it reaches the nozzles. We developed a unique, computer controlled system to measure uniformity of mixture and lag time. System operation is shown by measuring lag times and mixture uniformities for several operating conditions. This system is important in determining the design characteristics of inline injection systems, i.e., how nozzle supply-line size, injection pump operation, pesticide viscosity, and number of nozzles supplied by each injection point can be selected to optimize sprayer system design. Results from this system will be of great value to sprayer designers and to growers for field spraying and precision farming operations.
Technical Abstract: A turntable sampling system was developed to measure the uniformity of mixtures in spray nozzle lines over a time period and to measure the lag time required to reach expected concentrations of the mixture at different nozzle positions. The system consisted of a 1.22 m (4 ft) diameter turntable, 50 sample bottles, turntable speed controller, flow rate and pressure sensors, and a portable computer. The system was controlled with the computer, which allowed the operator to collect samples easily at any nozzle while the simulated sprayer underwent accelerations or decelerations between specified travel speeds. A Raven SCS 700 console and metering pump were used to evaluate the performance of the turntable sampling system for mixtures containing a fluorescent tracer and either water or Prime Oil II (55.61 mPa s) as the simulated pesticide. Spray samples were collected from the sampled nozzle during the desired time period and then analyzed with a fluorescence detector. The injection spray system required a spiral mixer in the injection chamber to maintain uniform mixture when Prime Oil II was used as the simulated pesticide. Lag time was 20.3 s at the nozzle at the end of the 1.07 cm (3/8 in) diameter and 5 m (16.4 ft) long boom and was 42.2 s at the nozzle end of the 2.09 cm (3/4 in) diameter and 5 m (16.4 ft) long boom when travel speed linearly increased from 1.6 to 6.4 km/h (1 to 4 mile/h) in 5 s.