Legumes are members of the plant family, Fabaceae, and include common crops such as peas, soybeans, alfalfa, and clovers. Through a symbiotic relationship with rhizobia bacteria, legumes can convert atmospheric nitrogen into plant useable forms through biological nitrogen fixation. Legume nitrogen fixation is a sustainable strategy for decreasing dependence on synthetic nitrogen fertilizer inputs for grain production*.
During plant domestication, legume crops were developed to maintain or increase soil fertility through nitrogen additions for subsequent crop species (like cereal grains) while simultaneous providing high protein seeds for human consumption or highly nutritious forage for livestock. Legumes continue to supply approximately 13% of the annual global agricultural nitrogen requirements, with synthetic inorganic nitrogen fertilizers fulfilling the vast majority of the remaining nitrogen requirements.
Despite all their benefits, just over a dozen grain legumes (annuals) and a few dozen forage legumes (annuals and perennials) are globally traded and commercially important. With more than 19,500 species in the legume family, humans have probably overlooked many species that merit further investigation and possibly domestication as new crop plants.
Perennial Grain Legumes
Temperate adapted perennial grain legumes, though currently non-existent, would be uniquely situated as crop plants able to provide relief from reliance on synthetic nitrogen while supplying stable yields of highly nutritious seeds in low-input agricultural systems. We are currently evaluating some native perennials such as lupins and some non-natives (alfalfa, sainfoin, etc.) as possible new grain legumes.
Companion Grain Legumes
We are also exploring various temperate-adapted wild and cultivated forage legumes as continuous living cover companion species (intercrops) with other TLI perennial grains. We are particularly interested in alfalfa, Kura Clover, and some Astragalus species that fit our criteria for perennial legumes that facilitate BNF and nitrogen-transfer in perennial polyculture cropping systems.
The first trials in spring 2017 explored alfalfa and lupin as a potential new grain legumes and Kura clover as a perennial companion legume. Since then the team has continued to work closely with the Perennial Agriculture Project Global Inventory team to identify other perennial legume candidates for domestication. Today the team is expanding breeding and agronomic research studying intermediate wheatgrass intercrops with legumes and studying sainfoin as a perennial grain legume candidate. We are working closely with the Perennial Agriculture Project Global Inventory (PAPGI) team to identify promising perennial legume species and to develop criteria for evaluating their agronomic potential as perennial crop plants using the pipeline strategy for domestication as a guide.
- Expand agronomic knowledge about dual-purpose intermediate wheatgrass + legume intercropping systems (i.e. row spacing, harvest timing, nitrogen balance) that produce grain for humans and forage for livestock.
- Design breeding strategies for improving the compatibility of perennial legumes, specifically alfalfa and kura clover, in intercrops with intermediate wheatgrass.
- Develop a long-term, collaborative domestication strategy to improve sainfoin seed yield and nutritional quality through a combination of breeding, agronomy, food science, and commercialization efforts.
*Their symbiosis with root-nodule bacteria (rhizobia) enables them to supply more than 100 Tg of biologically-available nitrogen to natural and agroecosystems each year through biological nitrogen fixation (BNF). This process, BNF, has been called the most fundamental biological process on earth aside from photosynthesis because nitrogen is the critical limiting element for plant growth. Availability of sufficient nitrogen to crop plants is essential for producing high-quality, protein rich, plant-based foods, and the entire nutritional nitrogen requirement for humans is obtained directly or indirectly from plants.Increasing the use of legumes for BNF is close to the idea of ecological intensification, using ecological processes rather than external inputs for crop production.
 Erik Steen Jensen and others, ‘Legumes for Mitigation of Climate Change and the Provision of Feedstock for Biofuels and Biorefineries. A Review’, Agronomy for Sustainable Development, 32.2 (2012), 329–64 <https://doi.org/10.1007/s13593-011-0056-7>.
 Jagdish K. Ladha and others, ‘Efficiency of Fertilizer Nitrogen in Cereal Production: Retrospects and Prospects’, Advances in Agronomy, 87.5 (2005), 85–156 <https://doi.org/10.1016/S0065-2113(05)87003-8>; T. E. Crews and M. B. Peoples, ‘Legume versus Fertilizer Sources of Nitrogen: Ecological Tradeoffs and Human Needs’, Agriculture, Ecosystems and Environment, 102.3 (2004), 279–97 <https://doi.org/10.1016/j.agee.2003.09.018>.
 J.N. Galloway and others, ‘Nitrogen Cycles: Past, Present, and Future’, Biogeochemistry, 70.2 (2004), 153–226 <https://doi.org/10.1007/s10533-004-0370-0>.
Makaneyyat Project, Ramallah, Palestine
National Laboratory of Genomics for Biodiversity, LANGEBIO, Irapuato, Mexico
North Carolina State University, Plants for Human Health Institute, Kannapolis, North Carolina
Saint Louis University and Missouri Botanical Garden, St. Louis, Missouri
University of Nebraska, Lincoln, Nebraska
University of Wisconsin, Madison, Wisconsin
University of Minnesota, St. Paul, Minnesota
Cornell University, Ithaca, New York
Related Scientific Publications
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Legume Program Videos
Learn about other perennial crops under development at The Land Institute.