Which factor does NOT influence the selectivity of herbicides?

The selectivity of herbicides is influenced by various factors, and among them, the soil moisture content is not a major determinant. Selectivity refers to the ability of a herbicide to target specific plant species while causing minimal or no harm to desirable plants.

The active ingredient's chemical nature is crucial, as it dictates how the herbicide interacts with plant physiology. Different chemicals have varying modes of action that make them more or less selective for particular types of plants. Additionally, the rate of application significantly impacts selectivity; applying too much can increase the likelihood of harming non-target species. The type of formulation used—liquid, granular, or others—can affect how the herbicide is absorbed and the efficacy against specific plants.

Soil moisture content, while it may influence overall herbicide efficacy and plant stress levels, does not directly dictate the inherent selectivity of the herbicide itself. This factor relates more to environmental conditions than to the specific characteristics or behaviors of the herbicide at the time of application, making it the correct answer as the factor that does not influence selectivity.