Certified Crop Advisor Practice Exam

What is the most important factor in herbicide carryover?

1. Soil moisture

2. Persistence

3. Degradation

4. Temperature

The correct answer is: Degradation

The most important factor in herbicide carryover is persistence. Persistence refers to the length of time a herbicide remains active in the environment before it breaks down or degrades. This is crucial because it directly influences how long the herbicide can affect subsequent crops or non-target plants. Herbicides with high persistence can pose a greater risk for carryover issues, especially if the herbicide is not broken down adequately before the next planting season. This situation can lead to unintended crop injury or yield loss, as sensitive crops may be planted in soils where the residual herbicide is still active. Understanding the persistence of specific herbicides, along with the environmental factors that may influence it, is essential for effective crop management and to minimize potential negative impacts on future plantings. While factors such as soil moisture, degradation, and temperature also play roles in the overall behavior of herbicides in the environment, they are not as critical in determining the extent of carryover as the herbicide's inherent persistence. Soil moisture can affect the rate of degradation, and temperature can influence microbial activity, but ultimately, it is the persistence of the herbicide that is most significant when assessing the risk of carryover.