25 August 1995

Sulphur short in Scots crop

SCOTTISH potato crops could be on the verge of exhibiting sulphur deficiency it emerged at a recent Scottish Agricultural College trials site open day.

Applications of magnesium sulphate increased tuber numbers on the Dundee site, although the soil was not deficient in magnesium.

"I am sure the response is from the sulphur and we are probably seeing the start of sulphur deficiency in Scottish potato crops," commented college specialist, Dr Simon Bowen. "We will now be extending this trial to see if the results bear out our theory."

The trials also supported the practice of splitting nitrogen applications. Applying 125 or 225kgN/ha at planting followed by 100kgN/ha at tuber initiation gave extra tubers and higher yields in trials with both Record and Cara, he said.

"Too much nitrogen in the early part of the season can encourage canopy growth at the expense of tuber formation. It will also continue to maintain a strongly growing haulm in the later part of the season, which will delay crop maturity and cause problems with haulm desiccation and skin set."

He also advocated splitting applications of muriate of potash (potassium chloride). Trials show that applying half the muriate two months before planting allows the chloride to be leached from the immediate rooting zone, with a consequent increase in tuber number and size. &#42