United KIngdom
January 28, 2025
A new study using data from Rothamsted in partnership with the University of Sussex has outlined a significant biodiversity impact that increased fertiliser use has on agricultural grasslands.
The researchers made use of the meticulous records kept of the world’s longest-running ecological experiment, Park Grass, set up at Rothamsted nearly 170 years ago, in 1856.
The findings, published in the journal npj Biodiversity, show that increasing application of fertilisers such as nitrogen, potassium and phosphorus, can reduce flower numbers five-fold and half the number of pollinating insects in agricultural grasslands.
This is a critical moment for land use policy globally, with many countries including the UK and the European Union, currently undertaking significant green reforms of their agricultural policies.
Almost a quarter of the Earth’s land area and almost half of the UK is agricultural grassland, areas where grasses or grass mixtures are used to feed livestock, support wildlife and maintain land resources in good condition. Fertilisation of these areas has boosted food production but has come at the cost of environmental degradation and adverse effects on human health and welfare.
Dr Nicholas Balfour, Ciaran Harris and Professor Francis Ratnieks of the University of Sussex conducted a field study in Hertfordshire, England where they quantified and identified the flowering plants and the insect pollinators (bees, wasps, flies etc.) present across 18 paired fertiliser treatments at Park Grass.
They found that reducing fertiliser application increased the numbers, species richness and functional diversity of both flowers and pollinating insects.
They also identified a trade-off between flower and pollinator diversity and grassland yield. To maximise flowering plant species richness, and hence also pollinator species richness, a significant drop in fertility is required – but this will reduce yields.
“The Park Grass Experiment is a great illustration of the trade-offs between biodiversity and productivity in grasslands. However, this globally important experiment is also helping to identify solutions – plots that support both high pollinator numbers and high biomass can be used to help design management of more sustainable grasslands.” said Rothamsted’s Prof. Jon Storkey
The study, funded by NERC, Rowse Honey Ltd., and the Elizabeth Creak Charitable Trust, did identify a potential solution looking at fertiliser adjustments. Their findings revealed that fertilising plots with all the major plant nutrients except nitrogen encouraged a high proportion of leguminous species. This approach not only preserved yields but also supported a greater number of pollinators, including bees. This could be a possible solution for conflicted landowners.
Dr Nicholas Balfour, of the Laboratory of Apiculture and Social Insects at the University of Sussex, who led the study said, “While reduced yields are not typically thought of as a good thing, reducing grassland production intensity has the potential to realise many of the benefits of multifunctional landscape: benefiting pollinators, increasing resilience to extreme weather events, increased natural pest control, better soil health and air quality, and reduced soil erosion.
“Our study suggests that the subsidies proposed in the forthcoming agricultural reforms are an economic necessity for sustainable and considered land stewardship that reduces fertiliser application and limits its negative consequences for biodiversity.”
Publication
Trade-off between pollinator-wildflower diversity & grassland yields
Topics
Species
