How is preemergence herbicide typically incorporated into the soil?

Preemergence herbicides are designed to prevent weed seeds from germinating and are most effective when they are incorporated into the soil before the weeds emerge. This incorporation can occur either through mechanical means, such as tilling the soil, or naturally through the application of moisture, such as a rainfall or irrigation event. The need for incorporation ensures that the herbicide is available in the seed zone, where it can effectively inhibit seed germination.

Using tillage allows the herbicide to mix into the top soil layer, creating a barrier that can help suppress the germination of various weed species. Alternatively, sufficient moisture from rain or irrigation can facilitate the herbicide's movement into the soil, ensuring that it reaches the depths where germination occurs. This method increases the efficacy of the herbicide, making it importantly effective against anticipated weed populations.

In contrast, spraying on the surface only may not provide adequate soil incorporation, which can lead to lower effectiveness against weeds. Applying the herbicide after the weeds have emerged is contrary to the function of preemergence herbicides, as they must be effective before the weeds can germinate. Mixing with other herbicides does not directly relate to the incorporation process necessary for preemergent action. Thus,