Highest Use Of Fertilizers On Grasslands Cut Flowers Fivefold; Pollinators Dropped By Up To 50%

Using high levels of common fertilisers on grassland halves pollinator numbers and drastically reduces the number of flowers, research from the world’s longest-running ecological experiment has found. Increasing the amount of nitrogen, potassium and phosphorus doused on agricultural grassland reduced flower numbers fivefold and halved the number of pollinating insects, according to the paper by the University of Sussex and Rothamsted Research.

Bees were most affected – there were over nine times more of them in chemical-free plots compared with those with the highest levels of fertiliser, according to the paper, published in the journal npj Biodiversity. The lead researcher, Sussex University’s Dr Nicholas Balfour, said: “As you increase fertilisers, pollinator numbers decrease – that’s the direct link that​ to our knowledge has never been shown before. “It’s having a drastic effect on flowers and insects. The knock-on effect goes right up the food chain,” he said.

This is primarily because fertilisers create conditions that allow fast-growing grasses to dominate, crowding out other grasses and flowers. It is generally assumed that having a greater diversity of flowers leads to a greater diversity of pollinators, which often have specialist requirements in terms of the blooms they like to visit.

The research was done in Rothamsted, Hertfordshire, on strips of grassland called Park Grass, which have been studied since 1856. The average use of fertiliser on grassland in the UK is about 100kg for every hectare. The highest amount in the experiment was 144kg a hectare, to which the greatest pollinator declines (of 50% or more) were linked. Even land spread with the average amount, however, had 42% fewer pollinators and five-fold fewer flowers than land with none. The results were most pronounced on plots treated with nitrogen, the most widely used type of fertiliser. Researchers found that plots treated with a fertiliser mix excluding nitrogen maintained a relatively high number of pollinators and flowers.

EDIT

https://www.theguardian.com/environment/2025/jan/20/uk-agriculture-farming-fertilisers-yields-biodiversity-study-park-grass-pollinators-bees-wildflowers-aoe