Atrazine carryover in conservation tillage systems

Excerpt

ATRAZINE carryover can reduce the wheat stand in winter wheat-fallow cropping systems that employ conservation tillage. Atrazine carryover is influenced by clay content, pH, cation exchange capacity (CEC), and organic matter level of Great Plains' soils. Clay content provides a basis for relating the other factors to stand reduction because it is one of the characteristics used in describing and classifying soils. Information on the clay content of soils can be obtained from soils maps, which are available at Soil Conservation Service offices.

Figures 1, 2, and 3 show the relationship between clay content and pH, CEC, and organic matter with curves for various stand-reduction percentages. Also shown in the figures are the probabilities of incurring a stand reduction as great as that represented by the curve.

These figures provide the herbicide user with a guide for the stand reduction that might be expected if soil texture and either pH, CEC, or organic matter is known and 1 pound of atrazine (active ingredient) per acre is used. For any given set of soil characteristics, the percentage of stand reduction can be reduced about 10 percent with each 0.1-pound active ingredient-peracre reduction in atrazine applied …