Illinois Field Crop Applicators Practice Test

Which of the following factors contributes to a lower carryover potential for herbicides?

1. Herbicide application early in the season

2. High temperature

3. Herbicide persistence is long

4. Low precipitation totals

The correct answer is: Herbicide application early in the season

Herbicide application early in the season contributes to a lower carryover potential due to several important ecological and environmental interactions that occur. When herbicides are applied early, they may have greater opportunities for degradation due to factors like increased microbial activity in the soil, which tends to be higher in the spring as temperatures start to warm up. In addition, early applications often coincide with higher soil moisture levels from melting snow or spring rains, promoting the movement of herbicides into the soil and allowing for more effective degradation and breakdown over time. This means that any residual active ingredients are likely to diminish quicker, reducing their potential carryover into subsequent growing seasons. In contrast, when herbicides are applied later in the season, especially in hot and dry conditions, the potential for carryover can increase. High temperatures and low precipitation create conditions that might limit the breakdown processes, allowing herbicides to persist longer in the soil.