World soils potassium-deficient in wake of Ukraine war

Low potassium levels in soils resulting from global sanctions on Russia and Belarus pose a significant threat to global food security if left unchecked, scientists warn.

Potassium is a critical nutrient for crops as it facilitates photosynthesis and respiration, needed for plant growth and successful yields.

However, the team of UK-based researchers say more potassium is being removed from agricultural soils through the harvesting of crops through intensive agricultural practices than is being added in fertilisers.

As a result, about 20 per cent of agricultural soils have deficient levels of potassium, according to the research by University College London (UCL), University of Edinburgh and the UK Centre for Ecology and Hydrology, which presents a raft of recommendations to address this.

“Deficiencies in potassium often go unnoticed until crop yields decrease,” said Will Brownlie, senior science project manager at the UK Centre for Ecology and Hydrology in Edinburgh and lead author of the study published this week (19 February ) in the journal Nature Food.

He said a lack of routine soil and plant tissue testing for potassium in many parts of the world contributes to the oversight.

Price hikes

Regions in the global South are experiencing the worst shortages: South East Asia (44 per cent) Latin America (39 per cent), and Sub-Saharan Africa (30 per cent).

Farmers traditionally apply potassium-rich fertilisers over their fields to replenish the depleted nutrient.

However, disruptions in the supply chain and soaring prices have inhibited its use, with farmers relying on nitrogen and phosphorus to boost yields, the researchers say.

The study says that in April 2022 the price of potash, the key ingredient in potassium fertiliser, was 500 per cent above the previous year due to a “perfect storm” of factors including rising fertiliser demand, escalating fuel prices, recovery from the COVID-19 pandemic, and the Russian invasion of Ukraine.

As a result, many farmers held back from applying potassium fertilisers, Brownlie told SciDev.Net.

Russia and Belarus together export about 42 per cent of the word’s potash supply, but following the Russian invasion of Ukraine in 2022, the UK, US, Canada and the EU imposed import sanctions on the two countries, disrupting global supplies and fuelling rising prices.

Since the initial price spike, the cost of potash has fallen by about 50 per cent, but remains elevated, raising concerns that farmers will be unable to access sufficient fertiliser to maintain food supplies, the researchers warn.

Co-author Peter Alexander, senior lecturer in geosciences at the University of Edinburgh, said: “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.”

Taking action

The researchers put forward six recommendations including better potassium management and a robust intergovernmental coordination mechanism.

Currently there are no national or international policies or regulations governing the sustainable management of soil potassium akin to the systems being established for other vital crop nutrients like nitrogen and phosphorus.

Brownlie said organic waste recycling was a straightforward solution.

“This involves safely reintroducing nutrient-rich materials such as human waste, manure, and food scraps back into agricultural systems,” he explained.

“Transitioning to circular systems like these is vital, not only for sustainability but also to shield farmers from the volatility of international fertilizer markets.”

Other recommendations include regular soil and plant tissue testing to determine specific nutrient requirements for crops; precise fertilizer application tailored to growth needs, and measures to mitigate soil erosion and water runoff, which can lead to nutrient loss into rivers and groundwater.

“A critical aspect is ensuring farmers understand the interconnectedness of nutrients,” added Brownlie.

Insufficient levels of one nutrient can limit crop yields and decrease the uptake of other nutrients from the soil, he said, adding: “Consequently, these unused nutrients may be more prone to environmental loss rather than being utilised by crops.

“Therefore, a holistic approach to nutrient management is essential for sustainable agriculture.”

Geoffrey Waweru, a soil scientist at Kenya’s Jomo Kenyatta University of Agriculture and Technology, welcomed the findings of the study as timely.

He believes the importance of potash in agriculture, especially in the wellbeing of plants in the face of climate change, cannot be understated.

“The recommendations are very well written, but I don’t know how far they went to the effect of potassium, especially its critical role in photosynthesis and stomata opening that regulate transpiration,” he told SciDev.Net.

“This is especially key as climate change will affect plant water use,” he added.

This piece was produced by SciDev.Net’s Global desk.