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Poster Presentations


Poster Presentations

Fungicide spray coverage: effects of soybean row spacing, spray volume, and nozzle type.

Presenter: Clifford H. Koger, USDA-ARS
Coauthor(s): Dan Poston, Mississippi State University. Eric Walker, USDA-ARS

A field experiment was conducted to investigate the effects of spray volume and spray nozzle type in wide- and narrow-row soybean on fungicide spray coverage, disease severity, and soybean yield. The glyphosate-resistant soybean variety Dekalb 46-51 was planted in 40- or 102-cm-wide rows in mid-April. A one liter/ha application of Quilt fungicide, azoxystrobin + propiconazole, was applied over-the-top of soybean in the R3 growth stage at 84 or 168 liters/ha with flat-fan, air-induction, twin-jet, or Turbo duo-jet spray nozzles. Water sensitive cards were placed half-way down the plant canopy in the row-drill and row-middle of each plot. Higher spray volume increased spray coverage, with 15 and 27% spray coverage at 84 and 168 liters ha-1 spray solution, respectively. Optimal spray coverage was obtained with flat-fan or air-induction spray nozzles when compared to twin-jet and Turbo duo-jet nozzles, as spray coverage levels were 28, 26, 17 and 14%, respectively, with the four nozzle types. Spray coverage was similar in the drill of narrow- and wide-row soybean. Spray volume and nozzle type did not affect disease severity, as Cercospora kikuchii and C. sojina infestations were similar across all treatments. Fungicide treatment reduced disease severity when compared to nontreated plots. Soybean yields ranged from 5240 kg/ha when fungicides were applied, regardless of spray volume or nozzle type, to 4970 kg/ha when no fungicide was applied. Narrow-row soybean yields were 5585 kg/ha and were when compared to yields for wide-row soybean, which yielded 4775 kg/ha when averaged across spray volume and nozzle type.

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