7 September 2001
Sap shows spuds running out of juice


POTATOES may be running out of nitrogen over a month before crop growth ends, which could be costing growers over 1t/ha/week in lost yield.

The finding follows checks made on the nutrient content of the sap taken from a range of UK potato crops.

“Despite rapid early growth, many crops which were planted late into moist warm soils appear to have run out of steam,” says Omex SAP manager James Brundle.

Sap tests in early August showed nitrogen levels throughout the UK averaging a healthy 115% of optimum.

That figure dropped to 55% of optimum by late August. Leaching and unusual growing conditions are likely causes.

“Up to 15% of a crops yield potential is put on during late bulking, so growers who picked this up in time are now reaping the benefits.”

For crops with several weeks of growth left before burn-off he recommends 50litres/ha of foliar N, such as Omex Folex, mixed with a blight spray.

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