Long-term trials conducted on behalf of K+S have shown the importance of maintaining soil levels of both potash and magnesium.

Trials on high-risk loamy sand soil have recorded a 0.67t/ha yield penalty after just one year when no potash or magnesium was applied, with a similar drop occurring in the second year.

“The K index fell by a whole point in 12 months without any fertiliser applications,” said Jerry McHoul of K+S. “The magnesium index took three years to fall by the same amount because of the depletion of soil levels.”

The studies confirmed the need for maintenance applications of both nutrients, he stressed. “It doesn’t make sense to wait until yields are falling. There’s too much at stake.”

Other trials demonstrated the value of magnesium applications to oilseed rape, noted Mr McHoul. “The average response to magnesium over five years has been 0.27t/ha. We’re delighted to see that the new Fertiliser Manual recognises the role of magnesium in achieving good oilseed rape yields.”