Forages in Corn Rotations: A Meta-Analytical Perspective.

Crop rotations benefit producers through improved soil health, reduced financial risk via operation diversification, and reduced disease and pest pressure. Soybeans [Glycine max (L.) Merr.] are the dominant rotational crop in corn [Zea mays L.] production systems due to similar infrastructure and more familiarity with their agronomic needs. Incorporating forage species, such as alfalfa [Medicago sativa L.]or perennial grass pastures, into the corn rotation as part of an integrated crop and livestock system may provide greater benefits. However, producers have been reluctant to utilize these types of integrated systems. The goal of this study was to perform a meta-analytical review of the available literature in order to provide an accurate representation of the potential benefits to corn that may be derived from several rotational crops in rain-fed corn systems of the U.S. Particular parameters evaluated for different regions of the U.S included biological nitrogen fixation (BNF), soil organic carbon (SOC), and corn grain yield in the rotation relative to a continuous system. Including alfalfa or grass pasture in a crop rotation provided larger increases in corn grain yield (1.22 ± 0.15 Mg ha^-1) than soybean (0.79 ± 0.13 Mg ha^-1) and small grains (0.42 ± 0.11 Mg ha^-1) due to improved N cycling and accumulation of SOC. Rotation with pasture provided greater corn grain yield increases than other rotational species in the southern U.S. Future plans include using the results of this meta-analysis to develop an interactive decision-making tool for producers considering the transition of their grain operation to an integrated crop-livestock system.