Depleted levels of potassium in UK soils are not only affecting drought tolerance and yields, but also lowering the capacity of soils to store water, according to research presented by Europe's largest potash producer, K+S Kali.
"'Potash saves water' is an old adage that has been shown still to be true," said the company's head of applied research and agronomy Professor Andreas Gransee.
"Long-term field trials in several sites in Germany show that potassium fertilisation raises the water storage of soils whether they are sandy, silty or clay."
This is due to "potash bridging" - the formation of links between soil particles that tend to lock in water while still making it accessible to plant roots, he explained.
"It also promotes rooting and improves soil structure by increasing the shear strength in sandy soils and decreasing it in clay soils."
According to K+S Kali UK technical manager Jerry McHoul: "We are in the early stages of understanding these effects. They are exciting but also worrying findings because we know that the potassium index of UK soils is falling. More than a third of all soils are now below the target index."
Meanwhile, he added, water is moving quickly up the political agenda. "The trend is towards drier, warmer weather. And as of this year, abstraction licences can be revoked without compensation under the Water Framework Directive."
McHoul suggested that growers were tempted not to apply potassium to soils because the effects of reduced levels are not immediately apparent.
"It's the Cinderella nutrient," he added. "But if you add up the soil benefits, improvements in yield and quality and efficiency of use of other nutrients as well as water, it can be costly to let levels drop."
Potash supply Stable prices
The long-term supply and affordability of potash fertilisers should not be a concern, said K+S Kali UK managing director Richard Pinner.
"Prices are stable and there is no reason for them to spike. There's enough potash in the ground for hundreds of years," he added.
The developing world accounts for half of global demand and this is likely to grow. Kali is currently investing US$3bn in a new potash mine in Canada.