Abstract
The objective of the research was to characterize the influence of weather parameters on spray application and determine the effects and interactions of the application time and spray volume on deposition. Spray applications were made in August, November, and February to plots of Dancy tangerine trees. In each month, the trees were sprayed at 6 nominal times (2, 6, and 10 a.m. and 2, 6, and 10 p.m.), 3 volume rates (470, 1890, and 4700 L/ha (50, 200, and 500 gpa)), and 4 replications. Spray mixtures contained a manganese tracer and spray deposition was sampled at 3 heights (1.2, 2.4, and 3.6 m (4, 8, and 12 ft)) and six radial locations at each height. Deposition was determined by colorimetry. Weather data including temperature, relative humidity, wind velocity, and wind direction were collected during the applications and leaf surface wetness was characterized by visual judgement. Application time and spray volume had significant effects on spray deposition. Overall, night-time applications (lower temperatures and higher humidities), made under dry leaf conditions, had higher deposition than day-time applications. However, wet leaf conditions could reduce deposition by increasing runoff from the leaves.
