On large farms, traditional crop rotations typically consist of barley, wheat and rapeseed.
According to a new study — published Tuesday in the journal Frontiers in Sustainable Food Systems — the addition of legumes, such as beans and lentils, could offer both sustainability and nutritional advantages, helping farmers promote soil health while providing consumers a wealth of vitamins and minerals.
"This strategy can contribute significantly to the specific European Union Green Deal Farm to Fork objectives to reduce greenhouse gas emissions, chemical pesticide use and synthetic fertilizer use," first author Marcela Porto Costa said in a press release.
"For example, in Scotland, we've shown that the introduction of a legume crop into the typical rotation reduced external nitrogen requirements by almost half whilst maintaining the same output of food measured in terms of potential human nutrition," said Costa, an agricultural researcher at Bangor University in Britain.
Without fertilizers, modern agriculture wouldn't be possible. Crops need nitrogen, and to sustain intensive, monoculture agriculture, farmers must rely on fertilizers to deliver sufficient quantities.
More and more research has unveiled the significant environmental and ecological costs of commercial farming's over-reliance on fertilizers.
The production of fertilizers is energy intensive, depletes finite resources and often involves the use of toxic chemicals. In addition, runoff from fertilized fields pollutes the surrounding environs, disrupting vulnerable ecosystems.
Legumes don't require extra nitrogen, as they acquire all the nitrogen they need from the air. The crops have a unique symbiotic relationship with bacteria that turns nitrogen from the atmosphere into a form usable by plants.
In fact, legumes add nitrogen back to the soil, boosting reserves for future crops.
Additionally, legumes provide eaters with a greater concentration of nutrients than most cereal grains, including protein, fiber, folate, iron, potassium, magnesium and vitamins.
For the new study, scientists used a unique agriculture model to analyze the impacts of adding legume to 10 different crop rotations. The model considered 16 different impact categories and three different European climates in Italy, Romania and Scotland.
"Our innovative approach goes beyond simple food footprints by looking at the footprint of delivering a specific quantity of human, or livestock, nutrition from all crops produced within representative crop rotations," said study co-author David Styles, researcher at the University of Limerick in Ireland.
"This provides a clearer picture of inter-crop effects and the overall efficiency of different cropping sequences in delivering nutritious food or livestock feed," said Styles, a researcher at the University of Limerick in Ireland.
For now, the model has only offered predictions about the nutritional benefits of adding legumes to commercial crop rotations, but the scientists suggest the environmental bonafide of legumes are well established.
"Our results strengthen evidence on the positive role that healthy diet transitions could make to environmental sustainability," said Styles. "Legumes provide a healthier balance of carbohydrates, protein and fiber compared with cereal crops, and could improve the nutritional profile of the food we eat."
"These results also highlight the need for whole-system — multi-crop, farm-to-fork — thinking when designing interventions to drive sustainable food systems so that we can deliver better nutrition whilst reducing environmental impacts," said Costa.
