FIELD-EVALUATION OF A BIOECONOMIC MODEL FOR WEED MANAGEMENT IN CORN (ZEA-MAYS)

A bioeconomic weed management model was tested as a decision aid for w eed control in corn at Rosemount, MN, from 1991 to 1994, The model mak es recommendations for preemergence control tactics based on the weed seed content of the soil and postemergence decisions based on weed see dling densities. Weed control, corn yield, herbicide active ingredient applied, and economic return with model-generated treatments were com pared to standard herbicide and mechanical control treatments, Effects of these treatments on weed populations and soybean yield the followi ng year were also determined, In most cases, the model-generated treat ments controlled weeds as well as the standard herbicide treatment, Th e quantity of herbicide active ingredient applied decreased 27% with t he seed bank model and 68% with the seedling model relative to the sta ndard herbicide treatment, However the frequency of herbicide applicat ion was not reduced, In 1 yr, seed bank model treatments did not contr ol weeds as well as the standard herbicide or seedling model treatment s, Corn yields reflected differences in weed control, Net economic ret urn to weed control was not increased by using model-generated control recommendations. Weed control treatments the previous year affected w eed density in the following soybean crop, In 2 of 3 yr, these differe nces did not alter weed control or soybean yield, Although tactics dif fered, the bioeconomic model generally resulted in weed control and co rn yield similar to the standard herbicide. The model was responsive t o differing weed populations, but did not greatly alter economic retur ns under the weed species and densities in this research.