Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2008
Publication Date: 6/29/2008
Citation: Derksen, R.C., Zhu, H., Ozkan, E., Hannond, R., Dorrance, A. 2008. Determining the Influence of Spray Quality, Nozzle Type, Spray Volume, and Air-Assisted Application Strategies on Deposition of Pesticides in Soybean Canopy. Transactions of the ASABE. 51(5):1529-1537. Interpretive Summary: Protecting soybeans against threats like Asian soybean rust requires targeting of sprays deep into difficult to treat canopies. With the emergence of this disease threat, there have been few studies documenting the fate of sprays on soybean plants. Most studies have examined the performance of various application strategies by utilizing artificial targets and tracers. The objective of this research was to determine the effect nozzle type, spray volume, and spray quality had on the fate of active ingredients in a narrow-row soybean canopy. Much lower concentrations of pesticide residue were found on stem tissue than leaf tissue. Differences in application methods were identified. Across two years, there was some indication that air-assisted delivery was superior to a standard flat fan nozzle treatment at 145 L/ha. Spray pattern also had an effect but was dependent on the angle of attack of the spray pattern, droplet size, and droplet velocity. Fungicide residue analysis in the showed Medium quality sprays performed somewhat better than Fine quality and Coarse quality flat fan nozzles at the same spray volume. There was no consistent effect of spray volume on the amount of spray residue found on stem and leaf tissue. Pesticide residue levels produced by air-assisted spray delivery was similar for 93 and 145 L/ha applications. The lower volumes were applied using an air-assist sprayer. This research aids producers in selecting application techniques to help manage the threat of Asian soybean rust and to put material where it is most needed.
Technical Abstract: Many insect and disease problems occur in specific plant canopy locations and can not be managed with systemic pesticides. Diseases such as soybean rust infect plant material deep inside a canopy that are difficult to target. Field studies were established in north central Ohio to determine the effect different application strategies had on targeting of foliar pesticide in narrow-row (18 cm) soybean plantings. Several different application factors were tested including spray quality, nozzle type, air-assistance, and spray volume. Pesticides for soybean pest management were applied each year. Pesticide residue analysis was conducted on treatment stem and leaf tissue samples. Overall, there was significantly less active ingredient found in the lower third of the canopies than the middle third and significantly less pesticide residue was found on stems than leaves from the same canopy location. Significantly more fungicide residue was found on lower leaves treated by the Medium quality XR8004 flat fan nozzle in 2005 than the Coarse quality XR8005 flat fan nozzle. There were no differences in fungicide residue found on lower leaves between the Fine quality flat fan nozzle and the Medium and Coarse quality flat fan nozzles. The twin-fan pattern nozzles (Turbo Duo and TwinJet) produced the lowest amounts of fungicide residue on the lower leaves in 2005. The mechanical canopy opener produced significantly higher fungicide residues on middle canopy leaves than all other treatments but the Jacto air-assist sprayer using JA3 nozzles produced the highest fungicide residues on lower canopy leaves. There were some statistical differences between the amounts of fungicide and insecticide residue found on plant tissue in 2006 because of the high amount of variability in the sample data. Overall in 2006, the higher volume XR8004 treatment (186 L/ha) and the twin-fan TTJ60-11003 treatment at 145 L/ha performed similar to the Jacto sprayer making applications at 145 L/ha using either flat fan or hollow cone nozzles. In general, higher volume applications produced higher amounts of fungicide and insecticide residue on leaves from the middle of the canopy for conventional flat fan and air-assist applications. Spray volume had less affect on residues measured on leaves from the lower canopy area. Across two years of different canopies at the same spray volume (145 L/ha), the Jacto sprayer using JA3 hollow cone nozzles produced more fungicide residue on middle and lower canopy leaves than the Medium quality XR8004 flat fan nozzle. Producers can use these results to choose application techniques that put pesticides where it will be most effective and to help reduce total pesticide usage.