Bean Fixing the Planet: Sustainable Nitrogen for Better Planetary Health
Nitrogen plays a vital role as a fundamental component in the creation of life’s essentials, such as nucleotides and proteins. The introduction of nitrogen into the food chain starts from the roots of plants, where it undergoes assimilation and fixation into a usable form for the plants. These plants are then consumed by animals and humans to provide the essential nutrients for optimal health and physiological functions. However, the current state of nitrogen utilization, specifically in the agriculture sector, has exceeded the safe operating limits for our biosphere. At the same time, there remains a growing necessity to enhance our food production capabilities to adequately support the projected global population of 10 billion by 2050.
This raises a crucial question: How can we ensure a sustainable supply of nitrogen for our crops? One potential solution lies in the utilization of nitrogen-fixing legumes, commonly known as bean plants.
Introducing the bean family and its nitrogen-fixing ability
The legume family, scientifically known as Leguminosae or Fabaceae, consists of familiar bean plants such as lentils, peas, peanuts, and many kinds of beans. One unique ability of most legume is their unique ability to fix nitrogen directly from the air through a symbiotic relationship with specific soil bacteria housed in dedicated globular-looking structures called nodules on the root system (see Figure 1) This natural process essentially allows legumes to produce their own nitrogen fertilizer, hence reducing or eliminating their need for synthetic fertilizers.
Figure 1: A legume plant root showing nodules attached to the roots (source: Nitrogen Fixation by Legumes).
This is a big deal as the environmental impact of synthetic nitrogen fertilizers presents a significant challenge. The production of synthetic nitrogen fertilizers is energy intensive as it requires high temperature and pressure that relies on fossil fuels. Furthermore, the overuse of these fertilizers frequently leads to runoff, contaminating our groundwater and promoting detrimental algal blooms in our waterways, such as rivers and lakes. The breakdown of these fertilizers also releases nitrous oxide, a potent greenhouse gas that is 270 times more impactful than carbon dioxide.
“We should leverage the potential of legumes and their natural nitrogen-fixing capabilities, which offers a pathway towards a closed-loop and regenerative food system, one that is inherently sustainable at its core.”
Untapped resources as functional food and sustainable agriculture
Due to their nitrogen-fixing capability, legumes have the remarkable capacity to utilize their nitrogen reserves for the evolution of diverse and wonderful enzymes that produce unique and valuable molecules. For example, the broad bean or fava bean (Vicia faba) naturally produces high levels of L-DOPA (l-3,4-dihydroxyphenylalanine), a precursor molecule to the neurotransmitter dopamine, the “happy molecule.” L-DOPA is currently used as a drug to treat Parkinson’s and Alzheimer’s diseases. Recent findings by Bekhbat and team (2022) also suggest its potential in alleviating anhedonia symptoms in patients with depression linked to brain inflammation. This makes the broad bean a readily accessible functional food that could positively impact both mental health and sustainable planetary health, i.e., agriculture. This concept is central to Broad ‘n Mind’s mission, a campaign to raising public awareness about the benefits of broad beans for our mental well-being and planetary health.
Another remarkable ability of the legume family is their ability to adapt to diverse environmental conditions. Some of these legumes can develop dedicated structures that aid their survival in challenging environments. For example, white lupin (Lupinus albus) can form cluster roots (Felderer et al., 2015) – bottlebrush-shaped rootlets – when soil phosphate levels are low. These unique cluster roots release organic acids that free up “locked” phosphate in the soil, making it accessible for the plant to absorb. Another fascinating adaption is seen in hopniss, a native North American legume (Apios americana). This plant forms periodic tubers, which resemble beads on a string. These structures function as biodrills, helping to loosen compacted soil eliminating the need for tilling.
The exciting potential of reintroducing legumes into our food system
Reintroducing legumes into our food system can create significant improvement by harnessing their fullest potential. Here are few strategies to consider:
- Promote Regenerative Agriculture: Integrating legumes into crop rotations and intercropping systems can greatly contribute to regenerative agriculture. This approach naturally reduces the need for synthetic nitrogen fertilizers while simultaneously enriching the soil through biological nitrogen fixation.
- Diversify with Underutilized Legumes: Reintroducing forgotten and neglected legume crops can significantly enhance the resilience of our food system. Greater diversity act as a buffer against unexpected disruptions, making our food supply more secure.
- Invest in Legume Biotechnology: Unlike extensively improved commodity crops like soybean, most legumes have not received the same level of genetic advancement. Furthermore, breeding these crops through conventional methods and even advanced techniques like gene-editing presents unique challenges due to a lack of translation research. Focused investment in translational plant biotechnology tailored to legumes can unlock substantial new potential for their improvement.
Legumes offer substantial advantages for both agriculture and our food system, yet their full potential has not always been recognized. Given the urgent need for affordable, accessible, and sustainable food sources, it is now crucial to consider the greater integration of legumes both into our agricultural practices and our diets. Ultimately, a wider adoption of legumes can contribute significantly to building a resilient and climate-smart food system, supporting the UN’s Zero Hunger goal in the face of climate change.
References
Bekhbat, M., Li, Z., Mehta, N.D. et al. Functional connectivity in reward circuitry and symptoms of anhedonia as therapeutic targets in depression with high inflammation: evidence from a dopamine challenge study. Mol Psychiatry 27, 4113–4121 (2022). https://doi.org/10.1038/s41380-022-01715-3
Felderer, B., Vontobel, P., & Schulin, R. (2015). Cluster root allocation of white lupin (Lupinus albus L.) in soil with heterogeneous phosphorus and water distribution. Soil Science and Plant Nutrition, 61(6), 940–950. https://doi.org/10.1080/00380768.2015.1081076
Nadia Radzman – enlightenbio guest blogger
Nadia Radzman, PhD, is a postdoctoral researcher in plant developmental biology at the Sainsbury Laboratory Cambridge University (SLCU) and a founder of an early stage agritech startup that accelerates genetic improvement in plants, especially legumes, that are impossible to be improved through conventional technique. She is also the director for the Broad ‘n Mind project – a campaign to increase public awareness about broad bean or fava bean as accessible and sustainable functional food for mental health. In Cambridge, she is an active steering committee member of Cambridge Global Food Security (GFS) and a research associate at the King’s College Cambridge’s Entrepreneurship Lab (E-Lab).
