The Opportunities and Challenges of Interseeding Cover Crops in North American Corn-Soybean Systems.

Abstract:

Cover crops offer numerous opportunities to enhance soil quality and reduce the environmental impacts associated with soil and nutrient losses from corn-soybean systems in North America. While knowledge of these potential benefits has increased farmers’ interest in cover crops, the narrow planting window for establishing cover crops after corn harvest often poses a practical barrier to widespread adoption of the practice. In this meta-analysis of the scientific literature, we assess the benefits and limitations of interseeding cover crops into standing crops of corn via high-clearance drill seeding relative to aerial seeding and surface broadcast seeding. High-clearance drill seeding during the early vegetative stages of corn (e.g. V4-V7 stage)  offers several advantages over aerial seeding and surface broadcasting, including better seed-soil contact, more uniform germination, less spatial variability in stands, cheaper seed costs, and a longer period for biomass accumulation. Possible challenges of interseeding cover crops include interspecific competition for water, nutrients and light, reduced yields of corn grain and silage, and increased input and labor costs required to establish and terminate the cover crop. Gaps in current knowledge of suitable cover crop species, technology needs, and priorities for future cover crop research will be discussed.