POTASH AND phosphate prices have risen dramatically in addition to those of nitrogen, but it is unwise to cut back on potash applications without knowing soil indexes.

Michael Armstrong, of the Potash Development Association, warned Smithfield visitors that low soil potash levels can reduce crop yield at an index below 2-.

“But, unlike nitrogen deficiency – which you can see by yellow colouring – you cannot see potash deficiency.

“You could end up saving pennies and losing pounds. Once soil is at index 0 or 1 it takes time and money to build it back up to maximise crop yields,” added Dr Armstrong.

However, producers who do a soil test and find a high index could cut back on applications next spring. “At 2- or higher you only need to put back what the crop takes out.”