Which method is used to control weeds before they appear?

A preemergent application is a method of weed control that involves applying herbicides to the soil before weed seeds germinate. This type of application works by creating a barrier that prevents the seeds from sprouting. The herbicides used in preemergent treatments typically target specific types of weed seeds and disrupt their growth early in the germination process, effectively stopping them from becoming established.

This method is particularly effective for annual weeds, as it allows for preventive measures to be taken before the weeds have a chance to emerge and compete with desired plants. Timing is crucial, and proper application before the expected germination period of the weeds enhances its effectiveness.

Postemergent application, on the other hand, refers to treatments applied after weeds have already emerged, making it less suitable for controlling weeds before they appear. Mechanical removal involves physically pulling or cutting weeds, which does not prevent new seeds from germinating. Broadcast seeding relates to the process of spreading seeds over a given area, which is unrelated to weed control methods. Therefore, preemergent application stands out as the correct answer for controlling weeds before they surface.