The targeted use of mixed legumes in agricultural systems could enhance yields while protecting pollinators, new research by Scotland’s Rural College (SRUC) has found.
Protein-rich legumes deliver a range of agronomic and environmental benefits including providing a substitute to meat-based proteins for human consumption; decreasing requirements for imported soybean in livestock systems; and – by fixing atmospheric nitrogen – reducing reliance on inorganic fertilisers and supressing weeds and diseases.
In addition, legumes such as field beans and clover, provide sugar-rich nectar and protein-rich pollen, helping to mitigate pollinator declines.
However, their value to pollinators under their current implementation and management is questioned.
Researchers at SRUC looked at a range of nitrogen-fixing crops grown as monocultures and mixtures and compared their performance in providing forage for a variety of pollinators, from bumblebees to hoverflies.
They found that mixtures did not consistently provide more forage for pollinators, with vetch and beans preventing lower-lying species such as white clover from flowering.
Instead, the use of targeted mixtures – using legumes which bloom at different times during the summer and have a variety of flower structures – provided a more stable source of forage throughout the season and fed a wider number of species.
However, researchers said legumes could not provide all the resources pollinators require and should be combined with other agri-environmental options such as hedgerows, woodlands, areas of rough tussocky vegetation, ponds and ditches.
Lead researcher Lorna Cole, an Agricultural Ecologist at SRUC, said: “Legumes will play a critical role in future agricultural landscapes, from providing healthy diets to reducing the need for inorganic fertilisers.
“Our research highlights that with small tweaks in implementation and management, they can also provide valuable sources of forage for insect pollinators.
“We need to act now to reverse pollinator declines and farmers can play a vital role in saving our pollinators.”
The study, which was supported by the Scottish Government, Mains of Loirston Charitable Trust and Horizon 2020, was carried out on small plot field trials in Aberdeenshire and Midlothian.