Potassium deficiency in the soil is a largely ignored problem that may affect food security, according to a study published in Nature Food. More potassium is being removed from soils than is being added in many areas of the world. The team from UCL, the University of Edinburgh, and the UK Centre for Ecology & Hydrology also gave a series of recommendations to mitigate the problem.
Potassium is a vital nutrient for plant growth. This compound helps with photosynthesis and respiration, and low levels can inhibit plant growth and reduce crop yields. It’s a common practice to spread fertiliser high in potassium but plants may not be able to use it and there are some questions about the environmental impact.
Globally, about 20% of agricultural soils have a severe potassium deficiency, mainly in Asia, Latin America and sub-Saharan Africa caused by intense farming practices. “Potassium is critical to sustaining the crop yields that keep the world fed, and its depletion poses a significant threat to the food security of millions of people around the world. This is an overlooked issue that needs to be addressed with a range of actions as the world population continues to grow,” said Professor Mark Maslin (UCL Geography).
In addition, the price of potassium can be quite volatile. Production is very localised; just 12 countries dominating production of potassium fertilisers, with Canada, Russia, Belarus and China covering 80% of the world’s total raw potash. In April 2022, the price of potash increased 500% above the previous year after Russia invaded Ukraine. This was mainly due to the fact that the UK, the US, Canada, and the EU imposed import sanctions on the two countries, disrupting global supplies and exacerbating prices.
Since the initial price increase, the cost has dropped by about 50% but remains higher than before the invasion. Farmers are concerned that they’ll be unable to afford sufficient fertiliser to maintain current food demands.
“The volatility of potash prices has major implications across the global food system. Access to potassium is vital for farmers to maintain their crop yields, but the recent high cost of potash makes it more difficult for the most vulnerable to obtain,” said Dr Peter Alexander of the University of Edinburgh.
These events are one of the main reasons the researchers have called for better potassium management and a more robust intergovernmental coordination mechanism. At the moment, there are no international policies to regulate the sustainable management of soil potassium that are similar to what is done for nitrogen and phosphorus.
In 2021, potash consumption reached 45 million tonnes. Global production is projected to be about 69 million tonnes in 2025, with new projects starting in Belarus, Canada, Russia, Australia, Eritrea, and the UK. The problem is that the mining of potash also raises human rights concerns and has a massive impact on the environment. The process generates millions of tonnes of sodium chloride salts, and other refuse chemicals. If these compounds leach into the soil, they can alter the soil’s and water’s pH and harm plants and animals.
The authors acknowledge that the impacts of potash mining are poorly understood and recommend more research. “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. 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,” said Will Brownlie of the UK Centre for Ecology & Hydrology.
Overall, the authors put forward a series of recommendations to prevent crop yield declines and protect the environment, including setting up a mechanism to assess current potassium stocks and identify the most at-risk countries and regions, developing sustainable mining procedures, and increasing intergovernmental cooperation (similar to what was created for nitrogen).
Brownlie, W.J., Alexander, P., Maslin, M. et al. Global food security threatened by potassium neglect. Nat Food 5, 111–115 (2024). https://doi.org/10.1038/s43016-024-00929-8