Which physical factor contributes to the susceptibility of selective herbicides?

The placement of herbicides is a crucial factor that influences their effectiveness and selectivity. When herbicides are applied, their location in relation to the target plants and surrounding environment can greatly affect their uptake and effectiveness. Proper placement ensures that the herbicide reaches the intended plant tissues in sufficient quantities, allowing for adequate absorption and action, while minimizing exposure to non-target species.

Selective herbicides are designed to target specific plant types, often based on physiological differences between the target and non-target plants. For instance, the timing of herbicide placement, such as application during specific growth stages of the target plant, can enhance selectivity, as some plants may be more vulnerable to the herbicide at certain periods.

While factors such as soil type, time of day, and humidity can influence herbicide efficacy, they are less directly related to the specific mechanics of how selective herbicides interact with target versus non-target species. Soil type affects herbicide mobility and retention, time of day can influence plant physiology, and humidity may impact evaporation rates, but none of these aspects are as directly impactful to the selectivity mechanism of herbicide placement as the method and timing of application itself.