10 September 1999

FIXED&VARIABLECOSTSSLASHED

Reduced cost establishment,

and lower herbicide bills.

Thats the strategy of Oxon

farmer Duncan Jack and crop

systems specialist

Steve Townsend.

Andrew Swallow reports

CULTIVATIONS and glyph-osate are the cornerstone of grassweed control strategy for one Oxon grower and his adviser. Get it right, and both fixed and variable costs are slashed, they say.

Duncan Jack grows 730ha (1800 acres) of combinable crops near Banbury. On his own 300ha (750 acre) Brake Lands Farm minimal cultivation and stale seedbeds replaced routine ploughing a number of years ago.

"Traditionally we had a big wild oat problem here, but now it is pretty much under control," he says. Blackgrass on the farm can be difficult, but Mr Jack is reluctant to call it resistant.

"I feel the resistance line is over-played by the manufacturers as an excuse for when a product doesnt work. We try to use as many different lines of attack on the blackgrass as possible."

That starts with stale seedbed creation, using wide cultivation equipment.

"My strategy is to do as much of the weed control out of the crop as possible," says consultant Steve Townsend. Cultivation costs are cut in the process (see table), and pressure on in-crop herbicides reduced.

"All cultivations are aimed at keeping conditions right for the grassweed to grow. Cultivation to kill weeds costs money, can damage the soil, and often doesnt work," he stresses.

At Brake Lands Farm, heavier land after cereals gets a pass with a disc and press combination followed by a roll. Lighter, brashier land gets a pass with tines and a roll. A Vaderstad crusher roll may be used five days after the initial round of cultivation to improve the germination.

"The better the false seedbed the more weeds will grow. And theres no reason why you cant drill straight into that," he says.

Mr Jack aims to have half his area in wheat every year, and only first wheat is grown. No more than five days is allowed to elapse between the last glyphosate spray and drilling with the Simba Free-Flow drill.

Weed control opportunities in breakcrops are made the most of, with no hard and fast rules on crop choice. "Oats do better than rape on our really heavy soils, and we can get better blackgrass control in oats than in wheat."

On fields where grassweeds are a particular problem, drilling later, or opting for a spring crop, is considered, adds Mr Townsend.

To aid weed seed germination and seedbed consolidation, Mr Jack leaves a long stubble with the combine, then follows with a topper to get a really fine straw chop. "Weve effectively bought ourselves an extra 20t/hr of combine output," he adds.

When the field has greened up sufficiently to get glyphosate onto the weeds, the sprayer comes out.

Typically 0.75litres/ha of a glyphosate 360 formulation is used, with 0.5 litres of tallow-amine adjuvant per 100 litres of water. Water volume is kept low, 70-100 litres/ha, to increase the concentration of the glyphosate and increase work-rate.

"I can do 300 acres a day on my own, or 500 acres with support," says Mr Jacks son, Clinton.

Most fields are sprayed at 20kmh (12.5mph) or above using high pressure to produce a fine spray. That combination would normally produce severe drift and vortexing, acknowledges Mr Jack. But the aerodynamic design of the Spra Coupe sprayer limits problems.

"We have a lot of 2-3m wildflower headlands, and we havent damaged one yet." The farm has won the Banbury Agricultural Associations conservation prize and is a LEAF member.

Greater speed puts forward momentum on the droplets, helping them to hit the thin leaves of emerging grassweeds, and high pressure ensures a fine spray to hit the small target.

"Where we sprayed some set-aside at 15kmh we had only 70% kill, but where we went at 24kmh it was 100%." &#42