Variable tolerance of some crop species to atrazine in various soils

Abstract

The carry-over of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-s-triazine), which occasionally causes damage to susceptible crops grown in rotation with atrazine-treated maize (Zea mays L.), calls for a refinement of the specified recropping intervals. Bioassays were conducted in a glasshouse to evaluate, with nine soils, the tolerance to atrazine shown by dry beans (Phaseolus vulgaris L. cv. Teebus), grain sorghum (Sorghum bicolor (L.) Moench cv. NK222), oats (Avena sativa L. cv. SWK001), soybeans (Glycine max (L.) Merr. cv. Forrest) and sunflower (Helianthus annuus L. cv. S0222). Significant differences between the tolerance of test species in experiments where dry beans/sunflower and oats/soybean combinations were evaluated are inconsistent with the single recrop interval that is stipulated for all four species. The amount of atrazine that was required to elicit a significant response from a particular test crop varied from soil to soil. The variable availability of atrazine in different soils for uptake by crop species needs to be considered to limit the risk when a sensitive follow-up crop is selected for a soil in which the amounts of toxic atrazine residues are known.