What two environmental factors can cause granular formulations to slow down in application devices?

The correct answer highlights that temperature and humidity are two critical environmental factors that can influence the performance of granular formulations in application devices.

Temperature affects the physical properties of the granular material. For instance, if the temperature is too low, the granules may become more friable and less able to flow smoothly through the application equipment, which can lead to uneven distribution. On the other hand, high temperatures can cause the granules to become clumped, affecting their release and effectiveness.

Humidity also plays a significant role. High humidity can lead to the absorption of moisture by the granules, causing them to stick together or even dissolve, which impairs their ability to flow through the application device. Low humidity can cause the granules to become overly dry and brittle, resulting in inadequate application.

In contrast, the other options do not directly relate to the application device's performance in the same way. For example, soil moisture and temperature, while important for plant health and growth, do not directly impact the mechanical operation of the application device. Pest pressure and air quality, though relevant to pest management strategies, do not influence the physical characteristics of granular formulations. Thus, temperature and humidity are pivotal in ensuring the effective application of granular formulations.