A comprehensive simulation analysis of the use and benefits of chloro-s-triazine herbicides (atrazine and simazine), in U.S. field corn, sweet corn and grain sorghum was conducted by David Bridges, Ph.D., Abraham Baldwin Agricultural College, and released last week.

Scenario analysis employed methods used in previous assessments coupled with 2009 regionally-specific data on weed incidence by species, crop yield losses by weed species, herbicide efficacy by weed species and herbicide use data by active ingredient, Bridges explained.

One scenario assumes that corn farmers would not have access to atrazine or simazine and that the glyphosate market share would remain constant at 2009 levels—approximately 75 percent of corn acres. (This scenario is highly likely because glyphosate-resistant weeds would probably increase quickly if more glyphosate is used, and, therefore, this would not be a likely alternative.)

In this scenario, field corn yields declined between 5.7 bushels and 17.6 bushels per current atrazine-treated acre. Averaged across all acres in the analysis, yield declines ranged from 2.9 to 13.6 bushels per planted acre. Averaged across all U.S. field corn acres, the projected yield decline without atrazine or simazine yield declines would range from 25 percent to 33 percent per atrazine-treated acre and approximately 20 percent per planted acre.