SYMPOSIA PAPER Published: 01 January 1990
STP25379S

Droplet Spectra for Some Agricultural Fan Nozzles, with Respect to Drift and Biological Efficiency

Source

The differences in drop size characteristics along the long axis of “fine”, “medium” and “coarse” sprays produced by agricultural fan nozzles were determined using the Aerometries Phase Doppler Particle Analyzer (PDPA). Water, water + 0.06% adjuvant, water + 0.4% emulsifiable concentrate (EC) and water +0.2% dispersible granule (DG) were sprayed through each nozzle. There was little difference in volume median diameter (Dv.5), number median diameter (Dn.5) or percent (by number and volume of the spray contained in drops <100um or >300um diameter when water was compared with the DG. However, the EC had a significantly larger Dv.5 than the water sprayed through five out of the six nozzles tested. Therefore, sprays produced by specific nozzles cannot be reliably defined on the basis of data for water alone. The percentage of spray volume contained in drops <100um diameter (most likely to drift) was 4 times greater in fine compared to coarse sprays. However, the 6-fold difference in flowrate results in the higher throughput nozzles producing most “driftable” volume per unit time. In coarse sprays, 69 — 84% by volume, but only 13 – 29% by number, was contained in drops >300um diameter (may rebound upon impaction). When these drops were artificially removed from the analysis, the Dv.5 was in the range 190 – 231um, irrespective of nozzle or'formulation. Thus, while coarse sprays contain, characteristically, large drops (which may contribute to off-target contamination because they are not retained well by plant surfaces), they are not associated with a reduced drift potential compared to fine sprays, based on volume production of drops <100um diameter.

Author Information

Adams, AJ
Chappie, AC
Hall, FR
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Developed by Committee: E35
Pages: 156–169
DOI: 10.1520/STP25379S
ISBN-EB: 978-0-8031-5136-9
ISBN-13: 978-0-8031-1388-6