Diverse agroforestry systems as both restoration and agriculture: Meta-analysis and a new long-term research site
Annual, monoculture cropping systems have become the standard agricultural model in the Midwestern US. Unintended consequences of these systems include surface and groundwater pollution, greenhouse gas emissions, loss of biodiversity, and soil erosion. Diverse agroforestry systems dominated by fruit and nut trees/shrubs have been proposed as an agricultural model for the Midwestern US that can restore ecosystem services while simultaneously providing economically viable and commercially relevant staple food crops. While much research has been done on both simple woody systems and diverse herbaceous systems, the concept of establishing multiple woody crops in a single agricultural system represents a combination of characteristics that has garnered very little attention, especially in temperate regions.
In order to provide information on this complex topic, a meta-analysis was performed on results from studies of biogeochemical and ecological indicators from a wide range of woody agricultural systems, to better refine estimates of what diverse agroforestry systems can attain. The lack of existing research on these systems also drives a critical need for establishing long-term experimental trials that can begin basic scientific research on diverse agroforestry systems.
Results from the meta-analysis clearly demonstrate the extreme deficit of research of diverse woody cropping systems. Nevertheless, results from other classes of woody systems provide a solid starting point for estimating performance of diverse agroforestry systems. Results demonstrate that yield-weighting the externality metrics is key to not overstating the potential benefits of woody agricultural systems. Most young woody systems displayed worse yield-weighted externalities compared to the corn/soy standard during the early years, demonstrating the importance of obtaining commercial yields when evaluating the potential environmental benefits of woody systems. In the long run, the different woody systems included in the meta-analysis had varying trends in yield-weighting externalities.
The obvious gap in existing research demonstrated by this meta-analysis, along with a growing interest in these systems in the Midwest, has led to the creation of the Multifunctional Woody Polyculture Research Site at the University of Illinois at Urbana-Champaign. This recently established site is the first large-scale field experiment evaluating a range of diverse food-producing agroforestry systems that have great potential for application in the Midwestern US. The field experiment hosts seven treatments, including several diverse agroforestry systems that lie along a diversity gradient.