Improving pollen and nectar supply by identifying the red clover (Trifolium pratense) cultivars that attract most pollinators

Abstract

Red clover (Trifolium pratense) is an important legume in agriculture for fodder and building soil fertility. Red clover flowers are also a valuable pollen and nectar source for pollinators during bloom. Farmers can choose among hundreds of commercially available red clover cultivars to plant, but the value of different cultivars for pollinators is not currently assessed or used as a recommendation criterion for farmers. Here, we compared the numbers of pollinators on 20 red clover accessions (12 cultivars and 8 breeding lines) grown under management typical for silage production in the UK in 2022 and 2023. Other potentially pollinator-friendly traits (inflorescence density, florets per inflorescence, floret length and nectar sugar production) were also measured to help determine which would be desirable to integrate into red clover breeding programmes. Accessions varied greatly, 50-fold, in numbers of pollinators attracted per plot and varied significantly in all other traits examined. Only inflorescence density was significantly positively related to insect abundance and species richness. These results suggest that breeding and using red clover cultivars that produce more inflorescences can increase the value of red clover to pollinators. We note that data on insect visitation can be gathered easily and could be provided to farmers to help improve the value of red clover fields to pollinators.