Potassium Depletion in Soil Threatens Global Food Security, Scientists Warn

Nutrient depletion in agricultural soil is nothing new. There have been numerous studies and concerns about the depletion of nutrient-rich topsoil and the loss of nutrients like carbon, nitrogen and phosphorus, but scientists are now warning about the depletion of potassium in soil.

In a study published in the journal Nature Food, scientists highlight how poor potassium management in agricultural soil could threaten global food security in the future without corrective actions.

According to the study co-authors, about 20% of global agricultural soil is deficient in potassium. Some of the most affected areas include farms in eastern Asia, southeastern Asia, Latin America and sub-Saharan Africa.

Globally, soils face challenges from soil-nutrient mining, when more nutrients are being taken from the soil during crop harvesting than are being replenished. The study noted that there is limited, if any, soil fertilization involving potassium, which could lower crop yields.

This is already happening in India, where low potassium levels in the soil are causing decreasing crop yields, the authors reported.

But the authors noted that simply adding more potassium isn’t enough to make up for the current deficiencies and their affects on the soil.

“We also still don’t know exactly what impact increasing potassium concentrations from fertiliser use will have on life in rivers and lakes,” study co-authors Will Brownlie, Mark Maslin and Peter Alexander shared in The Conversation. “Certainly in lab studies it has proven highly toxic to a range of animals. We need to know more about this before we support simply putting more potassium in soils.”

Instead, the study outlined a six-prong approach to avoid declining crop yields that could threaten global food security and minimize the environmental threats of potash mining, a method of extracting potassium for fertilizers. Potash mining can leave behind far more mining waste than the nutrient that is extracted, and the waste, much of it salt, is typically left behind, where it can pollute the environment. That raises concerns over quickly ramping up potassium fertilization worldwide.

First and foremost, the authors noted that there needs to be a global assessment of current potassium levels to better address the areas at greatest risk. 

From there, the authors recommended better tracking and forecasting for potassium price fluctuations, as price fluctuations can impact food supply for countries that rely on potassium imports from areas with more potassium resources.

Third, the authors noted a need for assisting farmers in determining their potassium levels and needs, then making recommendations for fertilization.

Another important action is to further assess the risks of potash mining and look into alternatives that could enrich soil without leaving behind so much waste. One possible alternative could be polyhalite, the authors said.

The study authors also emphasized the need to work toward a circular economy for potassium through recycling and reusing potassium as well as teaching consumers more about eating with a low potassium footprint, including by eating less meat.

Finally, the authors recommended better collaboration among governments, similar to the actions being taken by the United Nations Environment Programme and Global Partnership on Nutrient Management to address nitrogen in soil.

“A future UN Environment Assembly resolution on potassium provides a key opportunity for intergovernmental action, showcasing a strong commitment to fostering positive change,” the study concluded.