Optimizing high-residue cultivation timing and frequency in reduced-tillage soybean and corn

Integrated weed management (IWM) practices are needed to prevent the development of herbicide-resistant weeds and create more robust weed management programs. This experiment was conducted to determine the optimal timing and frequency of highresidue cultivation in reduced-tillage soybean [Glycine max (L.) Merr.] and corn (Zea mays L.) in Pennsylvania. Banded herbicides were applied at planting and high-residue cultivation frequency ranged from one to three passes. A split-plot assessed the eff ects of cover crop residue, either cereal rye (Secale cereale L.) in soybean or a hairy vetch (Vicia villosa Roth)-triticale (X Triticosecale Wittm.) mixture in corn, on weed control and yields. Breakeven analyses were used to evaluate cultivation and cover crop costs. Two cultivator passes reduced weed biomass to 500 kg ha-1 or less and were needed to optimize weed control and prevent yield loss. No weed control or yield benefit was observed with three passes compared to two passes. Cover crop residues increased weed biomass and yield in dry years but suppressed weeds without influencing yields in wet years. In 1 of 3 yr, cover crop establishment costs were offset by 0.7 Mg ha^–1 greater soybean yield with cereal rye residue than without. In 1 of 2 yr, a 0.8 Mg ha^–1 greater corn yield with cover crop residue compared to none off set establishment costs only when legume N credit was substituted for urea fertilizer. This research confirms that banded herbicide application together with high-residue cultivation can achieve yields similar to herbicide-only programs while diversifying weed control tactics.