Certainly, due to the drier conditions in certain parts of the state, a number of products may have an increased potential to carry over into the 2000 season. Areas in Illinois that have been hit the hardest with droughty conditions are the western and southern regions of the state. When making planting decisions for the 2000 growing season, especially in these droughty areas, make sure to check the rotational restrictions from the labels of herbicides used during 1999. The following information describes some factors to consider when assessing the potential for herbicide carryover in the 2000 growing season. Herbicide Persistence First of all, it is important to ask what products were used in the 1999 growing season, how long they persist, and what crops are sensitive to soil residues from these herbicides.
Different herbicides persist in the soil different lengths of time.
It is important to know when a product was applied to determine the time the product has been available for degradation. For example, the atrazine label indicates that soybeans can be planted the following year if applications were made before June 10 of the previous year. This rotational restriction was made to ensure that there was enough time for atrazine to degrade between application and soybean planting the following year. Soil Moisture and Temperature Other questions to ask are how much rainfall there has been since the herbicide application and what the soil temperatures have been. Dry weather conditions reduce the rate of herbicide degradation.