Measurement of foliar spray retention on creeping bentgrass

Experiments were conducted to evaluate the impact of spray volume, nozzle type, adjuvants, the presence of dew, and their interactions on foliar retention of creeping bentgrass. Tartrazine, a common food dye, was used as a tracer in this study. Increasing spray volume from 95 L ha(-1) to 1,500 L ha(-1) decreased foliar retention efficiency from 98% to approximately 85%. Compared with flat-fan nozzles, air-induction nozzles delivered similar retention efficiency at all spray volumes evaluated. However, flat-fan nozzles provided higher uniformity and more thorough coverage. Adding nonionic surfactants, organosilicone adjuvants, or methylated seed oils at typical concentrations yielded retention efficiency of approximately 90% to 93% regardless of spray volumes. In contrast, with water alone, increasing spray volume reduced retention efficiency from 95.9% to 87.3%. Simulated dew applied at 1,950 L ha(-1) increased retention efficiency by approximately 3% when spray application volume was 190 L ha(-1), while no difference was observed at 750 L ha(-1). The presence of dew reduced the impact of adjuvants on retention efficiency. Large quantities of dew, 3,800 L ha(-1), did reduce retention efficiency.