ABSTRACT
94The advent of shrouded sprayers has made the application of ultra-small drops (≈ 130 (im) feasible in both the field and the laboratory. This chapter covers the initial research done to develop an application technology based on the extra coverage afforded by the ultra-small drops. Reducing drop size from 410 μm volume median diameter (VMD) to 130 μm VMD increases the number of drops by 31 times. Reducing the carrier by ten times still yields three times as many drops for coverage. Field trials applied herbicides with 10, 30, 50, and 100 ℓ/ha of carrier at 25, 50, 75, and 100% of the recommended rate with two drop sizes. The ultra-small drops and reduced carrier rates increased control with glyphosate, diclofop-methyl, fluazifop-butyl, and sethoxydim. Control was obtained with 25% of the recommended rate of glyphosate under specific conditions; other chemicals gave control at the 50 and 75% levels. Reducing carrier rate to 30 ℓ/ha did not affect efficacy for the herbicides tested. Nozzle tip plugging reduced efficacy at the 10 ℓ/ha rate. A deposit study, using sodium fluorescein mixed with diclofop-methyl increased deposit by 35% with 130 (μm VMD drops over conventional 410 μm VMD drops when sprayed on paper targets at various orientations. The greatest increase was on the surface facing the spray.
