16 October 1998

Growth stimulants lift output in shy breeding potatoes

By Andrew Blake

POTATO growth stimulants could boost seed tuber numbers, according to field tests undertaken by a Scottish crop specialist firm.

Early test digs by CSC PotatoCare at David Pates Kincreich Farm, Inverarity, Forfar suggest a sequence of Yeald followed by Cropset offers plenty of scope for increasing output from certain varieties.

Mr Pate grows 28ha (70 acres) of potatoes for SE grade seed on medium loam soil. Among his six varieties is Hermes, a processing type.

"Hermes is a shy breeder," says CSCs Mark Ballingall. "So anything we can do to help it set more tubers is a help. There are many things we can do to increase numbers but they are not all cumulative."

Techniques include raising seed rates, applying seed-bed and foliar phosphate and treating the crop with Rovral (iprodione) fungicide which has a well recognised growth regulatory side effect, he explains.

"Unfortunately Rovral doesnt work very well on all varieties, for example Hermes." That is why the comparatively novel products, Yeald from Newman and Cropset from Improcrop are being investigated. Both have given valuable yield increases in ware crops in CSC trials, he says.

In what Mr Pate admits is only a "look-see" split field test Cropset applied at early bulking, when tubers are 25-35mm diameter, appears to have a stronger effect than Yeald sprayed at stolon initiation. "It seems quite consistent," says Mr Ballingall.

Best results in ware crops where overall yield is the target has come from a sequence of the two products, he adds. "Last year the response in replicated experiments was just under 19% for a total cost of £14-15/acre."

Yeald encourages auxin production in the plant, but Cropsets mode of action is still not fully understood, he notes.

In 1997 PotatoCares own trials in Angus on Maris Piper found Yeald at stolon initiation lifted output by 10% for about £15/ha (£6/acre). In a contract trial for supplier Improcrop, Cropset at early bulking gave 7.9% more marketable yield than the untreated crop, he says.

Another yield enhancing product being trialled by PotatoCare is Fulcrum from Cargill. A molasses-based material it is claimed to enhance plants photosynthetic properties by supplying sugar when the crop needs extra carbohydrate during bulking, Mr Ballingall explains. "Its more appropriate for ware crops."

In trials last year, again on Maris Piper, two 32litre/ha (23pt/acre) applications at stolon formation to early bulking produced a 12.8% yield increase over the untreated crop. Cost was about £40/ha (£16/acre). "Even at £40/t thats an economic response."

This season a single application of the same amount was applied much earlier, when the crop was only about 5cm (2in). That reflected manufacturer suggestions that it would give more consistent results, explains Mr Ballingall. Early signs are of a useful boost to bulking rates.

"They are three good products doing different things," he says.

Potato stimulants

* Cropset: action unclear.

* Fulcrum: Boosts bulking rate.

* Yeald: auxin enhancer.

* Cropset/Yeald for seed?

POTATOSTIMULANTS

&#8226 Cropset: action unclear.

&#8226 Fulcrum: Boosts bulking rate.

&#8226 Yeald: auxin enhancer.

&#8226 Cropset/Yeald for seed?