11 December 1998

Beet Pand K balance risks

MAINTAINING enough potash in soils for optimum sugar beet output is important and may cost less than some growers realise.

So says John Hollies of the Potash Development Association who is concerned that the price differential between sodium and potassium fertilisers may be leading to an inappropriate balance of inputs.

Although their functions are similar the crop needs an adequate supply of both for maximum yield, he maintains. With a unit of sodium only about two-thirds the price of a unit of potassium Mr Hollies believes some growers may be applying too much salt and not sufficient potash.

Available K

Large amounts of readily-available K are vital for heavy crops, he says. "Top growers are achieving more than 60t/ha. Operating at marginal levels at those yields is questionable.

"Potash is not lost from most soils, so the cost of maintaining higher levels is simply that of replacing the higher offtake. It is salutary that the cost of K replacement for a 60t crop is only £8/ha more than for a 40t one, even though the difference in value is around £800/ha."