Self-seeded cereal cover crop effects on interspecific competition with corn
Perpetuating cereal cover crops through self-seeding may increase adoption by reducing risk and cost. Winter rye (Secale cereale L.), wheat (Triticum aestivum L.), and triticale (x Triticosecale Wittmack) were used to develop self-seeding cover crop systems in a soybean [Glycine max (L.) Merr.]–corn (Zea mays L.) rotation. Cereal cover crops were planted in varying row spacing configurations and managed chemically and mechanically to achieve different levels of resource utilization in time and space. The objective of this study was to quantify interspecific competition of self-seeded winter cereal cover crops growing concurrently with corn. Total weed density responded more to environment than cover crop treatment, with 12.0 and 2.2 weeds m–2 in 2005 and 2006. Averaged across species, cover crop treatments lowered corn grain yield 5 to 22% compared with a no cover crop check. The most promising treatment lowered corn grain yield 7 and 11%, which is in the range for previously reported yield reduction using rye cover crops when rye was killed at or immediately after planting in a corn–soybean rotation. Cover crop regrowth intercepted <9% of photosynthetically active radiation (PAR) during early growth of corn. Combinations of lower corn plant population density and kernel density in cover crop treatments appear most responsible for the yield reduction. Additional research should focus on reducing interspecific competition during vegetative growth in corn when sink size is being determined.