No abstract

More than a century since Charles Darwin stated that diverse grasslands produce more herbage than monocultures, scientists still debate the relationship between species diversity and ecosystem function. Postulated benefits of diversity in experimental grasslands include greater and more stable primary production along with more efficient nutrient use. These benefits have been extrapolated to forage and grazing land systems with little supporting objective data. Most information on the potential benefits of increased plant diversity comes from studies of synthesized grasslands that have not included domestic grazing animals. We explore this debate relative to the management of temperate forage and grazing lands. Plant species diversity refers to the number of species (richness) and their relative abundance (evenness) within a defined area. Plant relations influence biodiversity responses through positive (e.g., facilitation, N2 fixation, hydraulic lift) and negative interactions (e.g., competitive exclusion, allelopathy). Early 20th century research on complex mixtures of forage species (limited to grasses and legumes) for pasture indicated equivocal results regarding benefits of species‐rich mixtures and typically recommended using the best adapted species in simple grass–legume mixtures. Recent research indicates potential herbage yield benefits from species‐rich mixtures for pastures. Limited animal productivity research on species‐rich mixtures indicates variable responses and much more research is needed. Grazing land productivity is a primary focus for biodiversity benefits because of the direct economic relevance to producers. However, taking a broader view of the multifunctionality of grazing lands to include environmental and aesthetic benefits to humans reveals a great scope for using biodiversity in grazing land management.

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Agricultural production systems in North America have become increasingly specialized. The lack of diversification has had negative economic, biological, and environmental consequences. One alternative approach to diversify agricultural production is to integrate cash grain cropping with ruminant livestock production. Our objective was to review research applicable to development of diversified croplivestock systems in the U.S. Corn Belt and discuss research priorities and constraints to adoption of those systems. One form of integration becoming more common in the U.S. Corn Belt occurs through contractual arrangements between spatially separated, specialized crop and livestock production farms. Less common is the spatial and temporal integration of crops and livestock on the same land base, which can occur via rotations of grain crops with perennial pastures, short rotations of grain crops with annual or short-season pastures, and utilization of grain crop residues for livestock grazing. We feel this latter model is truer to the concept of diversification. Based on published research and preliminary results from an integrated crop-livestock system project in Illinois, we suggest that integration of crops and livestock on the same land base offers tremendous potential to diversify farm ecosystems in the U.S. Corn Belt while being economically competitive and more environmentally compatible than prevailing specialized production systems. Although studies have addressed or are applicable to components of crop-livestock systems in humidcool environments, there remains a need for systems level research and funding opportunities for addressing the complex environmentplant-animal-economic-social interactions associated with integrated crop-livestock systems.