Comparison of Venturi Spray Tips and Spray Pressure on Glyphosate and Paraquat Efficacy Robert Wolf Biological and Agricultural Engineering Dept. Cathy Minihan and Dallas Peterson Department of Agronomy
Objective of this study: • Compare the efficacy and spray droplet characteristics of three venturi flat-fan nozzles against the turbo flat-fan tip at 207, 345, and 482 kPa (30, 50, and 70 psi).
Materials and Methods: Experiments: Location: Ashland Bottoms, Manhattan, KS Exp. Design: 2 x 3 x 4 split-split plot with 3 reps (24 treatments) Drop Collectors: Placed in 2 reps with 2 cards per rep (96 cards) Plot Size: 3 x 9 m with 1.5 m buffer Weeds Velvetleaf, common sunflower, sorghum, corn Visual Ratings: 1, 2, and 4 weeks after treatment Herbicides (2): Paraquat, 0.487 lb ae/a (1.3pt/a), NIS @ .25% v/v Glyphosate, 0.28lb ae/a (12 oz/a), AMSU @17 lb/100 gal Application Conditions: Date: July 09, 2002 Weed Size: Vele - 15 cm, Cosf - 20 cm, Sorg – 25 cm, Corn – 13 cm Temperature: 37 C R. H.: 20% Wind: S-SW@ 4-5 km/h
Materials and Methods cont.: Spray Tips (4):Turbo Flat-fan (TT) Air Induction Flat-fan (AI) Ultra lo-drift (ULD) Air Mix (AM) Spray Volume: 94 L/ha (11002 orifice tips) Application Ground Speed: 5.5, 7.1, and 8.4 km/h Spray Pressure: 207, 345, and 482 kPa Spray Tip Spacing: 76 cm, tilted 15 degrees Canopy Boom Height: 51 cm
DropletScan used to analyze droplets: Water Sensitive Paper Software & lock-key Color Scanner Portable computer Color Printer System Components
Volume Medium Diameter: *Significant .05
Control: Tip / Pressure *Significant
% Area coverage - water sensitive paper: LSD 11.5% LSD 11.5%
Summary of findings Dv0.5 (µm) (VMD): • Venturi tips produced larger droplet VMD’s than the turbo flat-fan. • The AI produced significantly larger droplet VMD’s than the Air Mix and turbo flat-fan, but not the ULD.
Summary of Findings: %Area Coverage • Significant differences were measured for percent area coverage among chemical, tip, and pressure interactions. • Means for Percent area coverage ranged from 47 to 20 percent with means separated by at least 11.5% considered significant.
Summary of findings: Efficacy • Very few significant efficacy interactions were measured among herbicide, tip, and pressure variables. • Paraquat provided better velvetleaf control. • Glyphosate gave better sorghum and corn control. • Common sunflower control was simmilar with each product.
Summary of findings: Efficacy cont. • Only minor differences in control were measured among tips and pressures. • The turbo flat-fan tended to be slightly lower (<10%) in control than the venturi tips. • AI and Airmix tips tended to give lightly better (no significance) control than the ULD. • No significant differences were found in weed control among the three pressures.
Final thoughts: • Why reduced control with turbo flat-fan? • high temperature, low humidity resulting in smaller drops (evaporation) that were quicker drying. • Venturi tips performed well regardless of whether a systemic or contact herbicide was used. • Performance over a wide range of pressure is also possible. • Venturi tips appear to be a viable option to minimize spray drift potential while maximizing performance.