Why Legumes Save Thousands of Litres of Water (and the Planet too)

What if your dinner could double as a climate solution – with legumes leading the way?

Agriculture accounts for nearly 70% of global freshwater withdrawals (FAO, 2021), what we grow – and eat – has never mattered more. Plant proteins like lentils, peas, chickpeas, and soybeans quietly lead the way in reducing water waste, restoring soil health, and even improving air quality.

Legumes: Cutting Water Use Drastically

Plant proteins like legumes have an edge when it comes to water use, especially under climate stress. Rising global temperatures increase atmospheric dryness – measured as vapor pressure deficit (VPD)– which forces plants to lose more water through transpiration to stay healthy. This means crops need to use more water to grow, making water efficiency crucial.

Chickpeas, lentils, and soybeans handle dry conditions well. Some types use water steadily even when the air is very dry, saving moisture in the soil for important growth times. They also lose less water through tiny leaf openings, which helps them use sunlight better by trapping more CO₂ inside.

On the molecular level, legume roots and leaves regulate water flow with specialized proteins called aquaporins, which can be enhanced to further improve water-use efficiency (WUE). Under elevated CO₂ conditions expected with climate change, legumes generally maintain better water balance and productivity.

Restoring Soil Health Naturally

They are the main plants that naturally capture nitrogen from the air and turn it into a form plants can use-a process called biological nitrogen fixation (BNF). This means farmers don’t have to rely as much on synthetic nitrogen fertilizers, which can harm the environment. Thanks to legumes, farms release less nitrous oxide, a powerful greenhouse gas.

Because of BNF, legume crops like soybeans, peas, and faba beans can grow better and often have more protein. In the European Union alone, legumes fix about 800,000 tons of nitrogen from the air every year, with grain legumes making up about a third of that. The amount of nitrogen fixed depends on the legume type, how long it grows, and the environment, usually between 100 and 300 kg of nitrogen per hectare.

The key is the partnership between legumes and helpful bacteria like Rhizobium and Bradyrhizobium that live in their roots. This partnership not only feeds the legume plants but also leaves extra nitrogen in the soil through root secretions and leftover plant material. That makes legumes a natural way to enrich soil, helping future crops grow with less need for chemical fertilizers. Including legumes in crop rotations is an affordable and eco-friendly way to improve soil health and reduce pollution.

Lowering Carbon Emissions

Legumes play a key role in reducing agriculture’s carbon footprint by naturally fixing nitrogen, which cuts down the need for synthetic fertilizers – major contributors to greenhouse gas emissions. By integrating legumes into cropping systems, farmers can simplify practices and lower overall carbon emissions. However, to fully reap these benefits, proper management is essential to avoid unintended environmental impacts. Assessing the carbon footprint alongside water, land, and nitrogen use helps optimize sustainable farming. Promoting legumes supports climate-friendly agriculture by significantly reducing carbon emissions throughout the food production system. 

Enriching Biodiversity

Biodiversity is essential for healthy ecosystems, and legumes play a powerful role in enhancing it within agricultural landscapes. By including legumes in cropping systems, biodiversity improves both above and below ground, over space and time. One major benefit comes from legumes’ ability to fix atmospheric nitrogen, enriching the soil and creating ideal conditions for other plants, microbes, and soil animals like earthworms, which boost biological activity. This natural nitrogen supply also reduces the need for chemical fertilizers, which can cause harmful runoff and damage aquatic ecosystems.

In addition to conserving space, their cultivation supports biodiversity directly. Their flowers provide essential nectar and pollen for pollinators including bees and butterflies, which play a crucial role in maintaining ecosystem health and crop productivity. They attract pollinators such as bees and butterflies by providing nectar and pollen, and their physical presence offers habitat for insects and small animals, supporting a wider food web that includes birds, bats, and other vertebrates.

Their extensive root systems improve soil structure, aiding water retention and carbon storage, while supporting diverse plant life. These local benefits extend to strengthen entire food chains, helping transfer nutrients to larger animals. Projects like the UK Agri-Tech Centre’s NUE-leg trial are exploring how legumes can reduce fertilizer use in grasslands while boosting biodiversity and sustainability. Integrating legumes is thus a crucial strategy for healthier crops, richer biodiversity, and more resilient ecosystems.

How VALPRO Path Contributes

The VALPRO Path project is driving a shift toward greener farming across Europe by boosting plant protein production. Focusing on legumes and protein-rich crops, it aims to cut down the use of synthetic fertilizers, greenhouse gas emissions and environmental damage. Through sharing knowledge, introducing new farming methods, and developing sustainable business models, VALPRO Path empowers farmers to work more efficiently while protecting biodiversity. The result? Lower carbon footprints, healthier soils, better water management, and stronger ecosystems – all crucial steps in fighting climate change and safeguarding the planet’s future.