*Atrazine applications for corn are restricted to a maximum of 2.5 pounds active ingredient per acre (lb. ai/A) per calendar year. In addition, there is a per-application maximum of no more than 1.6 or 2 lb. ai/A depending on soil erodibility (as defined by NRCS) and the amount of crop residue cover.
For preplant and preemergence applications on highly erodible soils with more than 30 percent crop residue cover, use up to 2 lb. ai/A (4 pt./A) per application. For highly erodible soils with less than 30 percent crop residue cover, use 1.6 lb. ai/A (3.2 pt./A). On soils that are not highly erodible, use up to 2 lb. ai/A (4 pt./A). For postemergence applications, a maximum of 2 lb. ai/A (4 pt/A) may be applied if no *atrazine was applied before corn emergence. If a postemergence treatment is required following a preplant or preemergence application, the total *atrazine applied may not exceed 2.5 lb. ai/A (5 pt./A) per calendar year.
Calculating the lb. ai/A of *atrazine is relatively simple when using products that contain *atrazine only. It may be difficult to calculate the total amount of *atrazine being applied when using prepackaged herbicide mixtures. This is especially true if both preplant/preemergence and postemergence premix products are being used. Table 3.7.6 gives common labeled application rates of some premix products along with the lb. ai/A of *atrazine being applied.