Guess how much just one blackgrass plant per square metre is costing you in lost wheat yield? 

Detailed Masstock trials at Stow Longa in Cambridgeshire have produced a definitive answer which may surprise you.

“On average, for each blackgrass plant per sqm you leave uncontrolled in the spring – and therefore competing with the crop – you lose approximately 44kg/ha of yield*,” says Masstock agrochemical trials manager David Newton.

“A population of some 12 blackgrass plants per sqm is therefore generating a yield loss of over half a tonne per hectare.”

With a September 2005 feed wheat price of £66 per tonne and with a typical Atlantis (mesosulfuron-methyl + iodosulfuron-methyl-sodium) application costing £33/ha you need only count 12 plants per sqm to justify the treatment. Add to that the reduced weed seed burden for following cropping years and it looks even more worthwhile. For milling wheat of higher value it follows that Atlantis can be justified at even lower blackgrass counts.

“This simple blackgrass truth underlines the real value to farmers of Masstock’s commitment to practical, economic trials that are increasingly valuable in these times of continuing downward pressure on cereal returns,” adds Dr Newton.

There’s still time to control blackgrass for those who have not made their spring herbicide applications, he advises, although the sooner Atlantis is applied the less yield will be lost. The trials on Hereward last year showed delaying Atlantis until 31 March, when the blackgrass had six tillers gave a yield of 11.03t/ha - 0.35t/ha less than the best Atlantis timing in December. Delaying until mid-April, with the weed at GS29, produced a yield of 10.72t/ha.

“Blackgrass this year is more advanced than last year because of the dry autumn in 2003. So it will be more competitive and harder to control this spring. The importance of applying any remaining Atlantis treatments as soon as possible is clear,” says Dr Newton.

*Results based on fully randomised and replicated blackgrass trial at Rookery Farm, Stow Longa near Huntingdon, Cambs, on a 2004 crop of Hereward, taken to yield. Plant counts were taken 04/02/04, ear counts were made 09/06/04. The yield potential of the site was 11.38 t/ha, achieved where good control (98.5% control leaving only 9.3 black-grass ears/m2) was achieved by a timely application of Atlantis. Untreated plant count was 117/m2 - yield loss of 5.10 t/ha. Autumn-only plant count was 36/m2 - yield loss of 1.60 t/ha.

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