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Combining reduced herbicide rates and cultivation for effective weed control in corn 1999

Project Leader: J. Mt. Pleasant, N. Gift, and R.F. Burt, Department of Crop and Soil Sciences, Cornell University, Ithaca, NY

Abstract: Only 20% of N.Y. field corn growers currently use cultivation to control weeds, either with or without herbicides. Despite years of on-station research demonstrating that banded herbicides and cultivation result in yields equal to broadcast herbicides, most N.Y. corn growers who cultivate still use broadcast, full-rate herbicides. While interest in cultivation is growing, according to both growers and extension agents, growers who cultivate and use herbicides lose money unless they understand the role of banding. According to growers, the reasons not to cultivate include time constraints (both amount of time during hay cutting and timeliness due to wet soil) and costs (fuel, equipment). However, both of these concerns can be mitigated with use of a banded herbicide. A banded herbicide enables growers to cultivate later in the season and still control weeds (timeliness), to cultivate only once or twice and still control weeds (lessening hours in the field), and to cut the herbicide portion of weed-control costs by two-thirds.

Demonstrations of a banded herbicide and single cultivation in field corn were held at the Mt. Morris BOCES in N.Y. The site was planted by students and fertilized, sprayed and/or cultivated by the researchers. Data were collected on weed biomass in and between rows and grain yield. Weed numbers and species were counted in each plot, both in and between rows. Treatments included broadcast herbicide alone, broadcast herbicide plus cultivation, 1/3 rate broadcast herbicide, 1/3 rate broadcast herbicide plus cultivation, banded herbicide and one cultivation, cultivation only, and a weedy check. A demonstration was given for students and local growers at a Weed Control Field Day in midsummer.

There were no significant differences in yield among the weed control treatments, though the untreated check did yield significantly lower than all weed control treatments except the 1/3 broadcast herbicide alone. Weed populations were strikingly low, which probably explains the lack of yield differences, even though competition for water was probably intense in this, a very dry season.

Growers who are already cultivating have the most to gain from banding or reducing herbicide rates, since they are already adept at cultivation and would not have to purchase new equipment. In addition, a grower who is less adept at cultivation is probably more likely to experience the apparent potential for yield loss associated with using a banded or reduced-rate herbicide. We believe that future demonstrations of banding and cultivation should be focused more on growers who already cultivate. Growers may be tempted to reduce herbicide rates without cultivating, since that may result in yields as high as with full-rate herbicides, but we do not recommend reducing herbicide rates unless the grower is prepared to cultivate in case of weed control failure. 1999 was a year where this could be especially important, since a lack of rainfall meant that many pre-emergence herbicides failed to activate, and cultivation might have been necessary even for growers who used full-rate herbicides.