Add calcium to spuds to hit rust spot
Add calcium to spuds to hit rust spot
ADDING a calcium and boron solution to blight sprays could help ensure internal rust spot does not devalue potato crops this autumn, says a Lincs agronomist.
"Most of the soils I advise on have an abundance of calcium and boron," says Robert Boothman. "But, under stressful growing conditions, such as drought or poor soil structure, the element supply can be restricted."
That has been shown to be linked to rust spot incidence, but applying a foliar feed of the nutrients, such as Cal-N, can overcome short-term deficiencies, he claims.
Problem
"The problem is we cannot predict when the crop is going to come under stress, so we advocate applying three or four applications of Cal-N at intervals of 10-14 days – it usually goes in with the blight sprays."
That policy has eliminated internal rust spot from crops of Maris Piper and Pentland Squire for grower Joe Bratley of Quadring, Spalding for the past three seasons.
Severe spotting in 1997 prompted his search for a remedy.
Now, most of his 95ha (235 acres) crop makes pre-pack premiums.
"We started off using Omexs CalMax, then Robert said he had a product that did the same job for half the price so we tried it instead," he says.
At 2.5 litres/ha application cost is about £6/ha (£2.50/acre).
As the calcium is in nitrate form it is immediately available to the plant, and is cheaper than using a calcium nitrate fertiliser, says Mr Boothman.
Nutrient content of Cal-N is quoted as 22.5% calcium oxide, 750ppm boron, plus magnesium, nitrogen and zinc, and there are no known tank-mixing problems, he says.
"We havent found anything we cant mix it with yet." he says.
Telephone 07860 251869 or visit www.boothman.co.uk for more details. *
INTERNAL RUST SPOT SOLUTION
• Foliar calcium + boron.
• 3-4 doses with blight sprays.
• Cost £6/ha/application.
• Appears to eliminate IRS.
Cal-N will be included with the first blight spray on this crop of Maris Piper at Quadring, says Joe Bratley. Given the difficult start to the season, many crops could be shallow rooting and run short of calcium, he believes.