High fertiliser use killing bees and pollinators: Two-year long study finds 

High amounts of the most common fertilisers such as nitrogen (N), phosphorus (P), potassium (K) and magnesium (Mg) on farm lands drastically reduces the population of pollinators, their richness and the number of flowers, a two-year study at the world’s longest ecological experiment site has found. 

While population of pollinators like bees was halved, there was a five-fold decrease in the abundance of flowers in the plots treated with the highest levels of fertilisers compared to plots which did not have any fertiliser treatment. 

The study, published in npj biodiersity journal on January 20, 2025 was conducted at Park Grass, Rothamsted, the site for the longest running experiment since 1856, by the University of Sussex and Rothamsted Research. 

The Park Grass Experiment at Rothamsted, southeast England, was set up in 1856 and is the world’s longest-running ecological experiment. The initial goal was to explore methods to enhance pasture productivity through both organic and inorganic soil fertilisation.

Data from the current two-year study showed a large and significant negative effect of the major plant nutrients (NPK) on the abundance, species richness and functional diversity of both pollinators and flowering plants.

Pollinators are vital to agricultural productivity and maintaining natural ecosystems. The study, thus, emphasised on the direct link between fertiliser use and the decline in abundance and distribution of many pollinator species. 

The researchers studied various plots treated differently — some with zero inputs, a few with farmyard manure and others with a combination of fertilisers. 

The two untreated plots had significantly higher flower abundance (5.18 times) and species richness (8.46 times) compared to the two plots that received the most fertiliser.

This occurred mainly due to the use of fertilisers, which created conditions that benefited a few rapidly growing species, like grasses.

Strikingly, the research found a near doubling in pollinator abundance (95 per cent greater pollinator abundance) and richness (84 per cent greater pollinator species richness) in the untreated plots versus those receiving high levels of fertilisers.  

Bees, which are key pollinators, were the most affected — there were over nine times more of them in untreated plots compared with those with the highest levels of fertiliser. 

The study indicated that nitrogen was the primary cause of harm, as plots treated with a combination of fertilisers, excluding nitrogen, had a relatively high number of pollinators and flowers.