Agronomics and Economics of Different Weed Management Systems in Corn and Soybean

The USDA has a goal of implementing integrated pest management (IPM) practices on 75% of crop area by 2000. Growers require more economic information before adopting IPM practices. A field study was initiated in New York to evaluate weed control, yields, and net returns of chemical (broadcast herbicides), chemical–mechanical (banded herbicides and cultivations), and mechanical (rotary hoe and cultivations) weed management under moldboard plow and chisel tillage in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. Chemical and chemical–mechanical weed management had similar corn net returns under moldboard plow ($370 and $355 ha⁻¹, respectively) and chisel tillage ($282 and $287 ha⁻¹). Mechanical weed management had less net returns in moldboard plow ($302 ha⁻¹) and chisel tillage ($121 ha⁻¹) because of 15% lesser corn densities and greater weed densities, especially in chisel tillage. In soybean, mechanical weed management in moldboard plow tillage had similar weed density (1.5 weeds m⁻²) lower yield (2.71 Mg ha⁻¹), but similar net return ($107.50 ha⁻¹) compared with chemical (1.3 weeds m⁻², 2.92 Mg ha⁻¹, and $85.60 ha⁻¹, respectively) and chemical–mechanical weed management (1.0 weeds m⁻², 2.78 Mg ha⁻¹ and $99.35 ha⁻¹, respectively). In chisel tillage, mechanical weed management had greater weed density (7.4 weeds m⁻²), lower yield (2.2 Mg ha⁻¹), and lower net return (−$7.80 ha⁻¹) compared with chemical (1.9 weeds m⁻², 2.8 Mg ha⁻¹, and $56.80 ha⁻¹, respectively) and chemical–mechanical weed management (1.9 weeds m⁻², 2.4 Mg ha⁻¹, and $27.30 ha⁻¹). Corn and soybean growers apparently can adopt chemical–mechanical weed management and maintain net returns. Soybean growers who use moldboard plow tillage can also adopt mechanical weed management and maintain net returns.