20 August 1999
Beware lower than usual soil potash levels
By FW Arable Reporters
BEWARE of significant changes in soil potash status, warns soil agronomy company Soil Services.
Wetter winters and late springs could have leached more of the vital nutrient out of soil profiles than usual, it says.
The company analyses 2000 fields each year across a range of soil types in central and southern England.
This years results show a widespread fall in K status from a stable index 2 to index 1 and sometimes low index 1. At those levels combinable crop yields can start to suffer, the company says.
The changes are not due to reduced K inputs, most fields receiving enough K to offset crop removal, the firm says.
Instead wetter winters and a wetter April-June are being blamed, leaching the nutrient out of top-soils.
If soil testing shows potash levels are very low some potash fertiliser should be applied to seed-beds, or top-dressed shortly after autumn drilling, advises Soil Services.
All growers should restore K-depleted top-soils to lower index 2 for cereals and upper index 2 for pulses, vegetables and rape, it adds. Heavier soils and those recently manured will be least affected.