Certified Crop Advisor Practice Exam 2026 – Complete Study Resource

The most important factor in herbicide carryover is persistence. Persistence refers to the length of time a herbicide remains active in the environment after application. Herbicides that have high persistence can remain in the soil for extended periods, which can lead to carryover effects in subsequent crops. This is particularly significant when sensitive crops are planted in areas where a persistent herbicide was previously used, as it can cause phytotoxicity or impact crop establishment.

While factors like soil moisture, degradation, and temperature can influence herbicide behavior, they do not directly define carryover. Soil moisture affects the mobility and effectiveness of the herbicide during its active period but does not determine how long the herbicide will persist in the soil. Degradation processes can break down herbicides, potentially reducing their persistence, but understanding the persistence itself is key to predicting carryover. Temperature can influence the rate of degradation and insect activity, but again, it is the persistence that primarily determines the likelihood of carryover concerns.