Potassium deficiency in agricultural soils is a largely unrecognised but potentially significant threat to global food security if not addressed, say researchers.

The lack of this key nutrient can inhibit plant growth and reduce crop yields. Farmers often spread potassium-rich fertilisers over their fields to replenish the depleted nutrient, but supply issues can inhibit its use and there are also questions about the environmental impact. 

The new study, published in Nature Food, finds that in many regions of the world, more potassium is being removed from agricultural soils through leaching or when crops are harvested. The authors from the UK Centre for Ecology & Hydrology (UKCEH), the University of Edinburgh, University College London and the Institute of Environmental Assessment and Water Research in Spain make a series of recommendations to tackle the issue.

The researchers report that globally, about 20% of agricultural soils face severe potassium deficiency. Particular regions are likely to experience more critical shortages, including 44% of agricultural soils in South-East Asia, 39% in Latin America, 30% in Sub-Saharan Africa and 20% in East Asia, largely due to more intensive agricultural practices. 

Dr Will Brownlie of UKCEH, lead author of the study, says: “By wisely handling nutrients like nitrogen, phosphorus and potassium together, we can reap multiple benefits: prevent pollution, boost crop yields and minimise nutrient loss. It's about coordinating our approach for better farming outcomes.”

Farmers often rely on fertiliser to replenish their fields’ potassium but prices can be quite volatile. Production of mined potash, from which potassium is extracted for fertiliser manufacture, is highly concentrated, with just 12 countries dominating the £15 billion international market for potassium fertilisers. Canada, Russia, Belarus and China produce 80% of the world’s total potash. 

The researchers highlight how in April 2022, the price of potash increased 500% above the previous year following a ‘perfect storm’ of factors. These included rising fertiliser demand, escalating fuel prices, recovery from the COVID pandemic and the Russian invasion of Ukraine, which resulted in the UK, US, Canada and the EU imposing import sanctions on Russia and Belarus. 

Since then, the cost of potash has fallen by about 50%. But concerns remain that farmers will not be able to access sufficient fertiliser to maintain food supplies under the current system, for there are no national or international policies or regulations governing the sustainable management of soil potassium.

Potash mining generates millions of tonnes of refuse mostly composed of sodium chloride salts which can leach into soils and salinise soil and water tables, harming plants and animals. The impacts of potassium fertiliser runoff into local ecosystems are poorly understood, and the researchers recommend more study about its effects. 

Dr Brownlie says: “The environmental impact of potash mining and use in agriculture is something that needs greater scrutiny. There’s much that we still don’t understand about the effects that artificial potassium enrichment has on nearby ecosystems.”

The researchers put forward six recommendations for policies and practices to prevent potential crop yield declines, safeguard farmers from price volatility and address environmental concerns: 

  1. Set up a global assessment of current potassium stocks and flows to identify the most at-risk countries and regions
  2. Establish national capabilities for monitoring, predicting and responding to potassium price fluctuations
  3. Help farmers maintain sufficient soil potassium levels with further research about the yield implications of limited potassium in various crops and soils
  4. Evaluate the environmental effects of potash mining and developing sustainable application practices
  5. Develop a global circular potassium economy that maximises the reuse and recycling of the nutrient
  6. Increase intergovernmental cooperation through the UN and other agencies to develop global policy coordination akin to what’s been developed for nitrogen

In 2021, global potash consumption reached 45 million tonnes and production is projected to rise to about 69 million tonnes in 2025 with new projects starting up in Belarus, Canada, Russia, Australia, Eritrea and the UK. 

Paper information

Will Brownlie, Peter Alexander, Mark Maslin, Miguel Cañedo-Argüelles, Mark Sutton, Bryan Spears. 2024. Global Food Security Threatened by Potassium Neglect. Nature Food. DOI: 10.1038/s43016-024-00929-8