Integrated Mechanical Weed Management in High Residue Cropping Systems

The objective of this research was to evaluate the potential of select mechanical tillage implements and reduced herbicide inputs in integrated high-residue corn and soybean systems. This integrated approach attempted to reduce the negative effects from herbicides and intense inversion tillage, while providing effective economical weed control. Treatments examined a vertical coulter, a rotary harrow, a high-residue rotary hoe, and a high-residue row cultivator in combination with soil-applied broadcast, soil-applied banded, or post-emergence herbicides. Conventional no-till using herbicides and a weedy check were included for comparison and the weed seed bank was supplemented to help ensure an effective assessment. Evaluation parameters included crop population, weed density, end of season weed biomass, surface residue, grain yield, and costs. Weed density, crop, and production year influenced the efficacy of the mechanical implements. Treatments including herbicides reduced weed density and weed biomass compared to treatments relying on mechanical control alone. The vertical coulter and rotary harrow controlled weeds similar to a herbicide burndown treatment in corn, while with the later planting date of soybean, this treatment was not as effective as a burndown herbicide. While the rotary hoe had a minimal impact on surface residue, weed densities were higher than with the soil-applied broadcast herbicide treatments. In addition, the rotary hoe did not increase weed control in banded herbicide treatments. Treatments that included banded herbicide tended to have better weed control than treatments that relied strictly on mechanical implements, but lower weed control than broadcast herbicides. Of the mechanical tools tested, the high residue cultivator was the most effective in reducing weed density and weed biomass, while maintaining crop yield. The greater reliance on mechanical implements reduced weed control cost, but tended to have higher breakeven prices due to lower yields. Overall, mechanical tillage implements alone did not provide adequate weed control, while integration with reduced herbicide inputs maintained acceptable weed control and competitive crop yields.