USDA forest service spread factor technology database

摘要

Whenever drops impact on cards or foliage, estimates of their aerodynamic size rely heavily upon the spread factor expression assumed or developed. Uncertainties in spread factor may lead to erroneous estimates of aerodynamic drop size and subsequent calculation of mass and volume of spray material released. Over the last 40 years the USDA Forest Service and its cooperators have used witness cards (because they are inexpensive and easy to use) to collect and interpret spread factors for several hundred pesticide tank mixes, and have conducted extensive tests to quantify the relationship between deposit stain size and in-flight drop diameter.