Which environmental factor influences both deposition and drift of pesticides?

• A. Soil type.
• B. Cloud cover.
• C. Humidity.
• D. Vehicle speed.

Answer: (C)

Humidity directly controls how fast spray droplets evaporate in the air, which in turn determines their size as they travel. When humidity is high, evaporation slows, so droplets stay larger and heavier longer and are more likely to deposit on the target surface. Drift is reduced because those bigger droplets don’t stay airborne as easily. When humidity is low, droplets evaporate quickly, becoming smaller and lighter, making them more prone to be carried by air currents and drift away from the target area. So humidity links both deposition and drift by shaping droplet size and air behavior during spraying, making it the factor that best influences both processes.