3 May 1996

Yield bonus claims

made for fringe spray-on boosters

TWO novel spray-on products to boost tuber yield and quality were launched at the event. Both were acknowledged to lie in the "muck and mystery" segment of the market, but have given useful trial results, according to their promoters.

Crop-Set, from Improcrop, is an extract of the yucca plant combined with a lactobacillus, as used in silage additives, urea and trace elements. Said to have been used in South Africa for four years and the US for two, the product is claimed to have given yield increases of 10-15% in limited UK trials last season. Overseas figures have been even higher, said the firms James Thompson.

"We dont really know how it affects the crop," he admitted. But stress relief at tuber initiation could be one benefit.

There are two tentative timings according to crop and variety. Each involves a comparatively low dose rate compared with other similar products. "Were using just 600mls/ha – 0.5pt/acre."

Applied at the "hooked" stage it helps boost tuber numbers in shy-setting varieties such as Pentland Dell, he said. Later application to other more freely setting types is said to give a more uniform size range.

Enough to treat about 1600ha (4000 acres) should be available this season at an on-farm price of about £20/ha (£8/acre).

Fulcrum, from Intermol, is a molasses-based solution including trace elements and an adjuvant. Its main use is in the early stages of growth when the crop is 8-12cm (3-5in) tall, said the firms Steve Lucas. "Were using it to kick-start the plants when photosynthesis may be limiting."

The product, said to have been inspired by the work of Nobel prize winning biochemist Tony Benson, provides readily available carbohydrate when the developing crop might otherwise be checked, he explained.

Adding micro-nutrients at the same time helps overcome stress that might be experienced in crops sprayed with sugar alone, he suggested.

Developed in the US since 1989, Fulcrum is said to have given yield lifts of up to 27% in UK field tests, being used on more than 2000ha (5000 acres) pre-launch last year.

Applications at tuber initiation have also proved beneficial, said Mr Lucas.

But with each treatment costing £100/ha (£40/acre) band spraying for early applications is advisable, he suggested. "Its the early timing thats giving the return."

&#8226 Crop-Set from Improcrop, 10-15% yield increase, raises tuber numbers in shy setting types, uniformity in others.

&#8226 Fulcrum, from Intermol, molasses based, kick starts early crop growth, up to 27% yield lift in trials.