Tackle blackgrass early to beat repeat
Woads revival spurred by lower cost extraction
Soaring demand for natural
dyes for fabrics, paints, and
for ink in bubble-jet printers
has triggered the first British
crops of woad for almost 70
years. Edward Long reports
CABBAGE-LIKE woad leaves are an important source of indigo, the worlds only natural blue dye.
The crop was grown on East Anglian fen farms until competition from cheaper synthetics forced closure of the last processing plant in Cambs in 1932.
In the past extraction was labour-intensive and took 12 weeks. But development of a mobile unit to do the job in only 12 minutes has transformed production costs.
"The prospects for woad look bright, as the textile industry is searching for natural clean substitutes for synthetic dyes, and new high-value markets are opening up," says Andrew Flux of Norfolk-based seed merchant Gorham & Bateson. "We are involved with a MAFF/LINK-funded project to redevelop woad as a commercial crop."
This year three pilot crops totalling 10ha (25 acres) are being grown on various soils across East Anglia to develop an agronomy package, to test a new harvester and mobile in-field processor, and to assess economic potential under farm conditions.
Three varieties, two from Europe and one from China, are being evaluated.
The spring-sown crop is harvested when the dark green fleshy leaves are about 30cm (12in) tall. In a non-destructive approach, a swather-like machine leaves the stubble to regrow. This is normally done three times a season, with first harvest in early to mid-July and the last in late autumn.
From a total yield of about 20t/ha (8t/acre) of leaves 45-50kg of indigo worth about £30/kg should be extracted.
"We are multiplying seed and will have sufficient for up to 100 acres of commercial crop next season," says Mr Flux.
Lot to learn, but the potential is there
NORFOLK farmer Ian Howard has one of this years pilot crops on his 160ha (400-acre) Rawhall Farm at Beetley, near Dereham.
"I am growing woad on behalf of 45 other members of the Anglian Industrial Crops Group, which has support from the EUs 5b initiative," he says.
"We need value-added alternative crops and the world is crying out for naturally-sourced raw materials for industry which can be grown and processed on farm without need for subsidies. Woad could be the answer."
The 1ha (2.5-acre) crop is after wheat. Glyphosate was sprayed on the stubble and the land ploughed in late autumn. Power harrowing twice in spring achieved a good seed-bed. An air drill was used, the manufacturer producing cell wheels to cope with the small irregular shaped seed. It was sown in 50cm (20in) wide rows at 10cm (4in) spacing on May 5, and was up within a week. Emergence was poor, possibly due to heavy rain, but plants grew away fast. Half was harvested last week.
"There seems a big demand for woad and I can see its potential as an alternative high value/high risk crop for an arable rotation, if we can learn how to grow it properly," says Mr Howard. "It is highly susceptible to weeds, particularly charlock, plantains, and docks, which if harvested with the crop will contaminate the indigo. We still have a lot to learn." *
Tackle blackgrass early to beat repeat
DECIDE the level of control you need and strike hard and early.
Thats the advice to cereal growers with blackgrass from Jim Orson of Morley Research Centre and chairman of the Weed Resistance Action Group. "You must have an overall control strategy," he says.
Many blackgrass infestations showing above crops this summer can be blamed on cool moist weather during seed maturation in June 1998. It extended seed dormancy, he says.
"That and the difficult autumn made it hard to time sprays correctly. And the problem was exaggerated because wet soils further increased seed dormancy."
Two more features made matters worse. Wet weather moved isoproturon (ipu) herbicide further away from the weeds rooting zone than normal, and many sprays simply went on too late to deal with big blackgrass plants. "It is important to tackle blackgrass when it is small, and critical where you have partial resistance as many people do."
Take advantage of rotational and cultural control to ease the action of herbicides, Mr Orson advises. "Drill your worst infested fields last, though I recognise that may conflict with other requirements. Unfortunately rotations are not as attractive as they once were.
"Above all determine the level of blackgrass control you require and be prepared to challenge the dogma that you should always aim for 95%.
"Naturally if you are knee-deep in blackgrass you will have to think about changing cultivation practice and consider using robust chemical programmes.
"But if you have very low infestations and you are drilling in October after ploughing you only need 75-80% control. That is why ipu is still sprayed on huge areas and generally gives satisfactory control. Yes it is inferior to newer products against blackgrass, but it has a place, especially in programmes for delaying the onset of resistance."
A common misconception is that so-called enhanced metabolism resistance affects ipu and nothing else, he says. "Enhanced metabolism resistance is not ipu resistance. If you have it you will have some degree of resistance to all the otherwise effective blackgrass herbicides in cereals."
One concern expressed at the European working group of the Herbicide Resistance Action Committee, of which Mr Orson is a member, is that more effective modern grassweed killers will tempt growers to sideline valuable cultural measures. "If we start drilling even earlier again we could simply end up on a treadmill of declining control." *