Neat profits with comb

4 March 2000

Neat profits with comb

Mechanical weed control is delivering big benefits for one Staffordshire grower. Heres how.

SWITCHING to mechanical weeding at Home Farm, Chartley in Staffordshire enabled James Mackellar to slash his input bill by £18,000.

That saving came from eliminating autumn and spring herbicides (£15,000) and reducing fertiliser usage by £17.50/ha (£7/acre) – through better soil aeration and improved use of soil nutrients, he claims.

On top of this, yields have improved. Oats were up half a tonne to 10t/ha (4t/acre) because of the extra aeration, believes Mr Mackellar. Both barley and wheat crops also showed increases of a quarter of tonne – to 2.75 and 3.25t/acre respectively.

Mr Mackellar runs the 361ha (903-acre) mixed enterprise with his wife, Isobel, with additional help from son, Bryce, currently on a year out from agricultural college, and daughter, Alexandra.

The decision to buy an 18m Opico comb harrow was made to pre-empt a possible future levy on agrochemical use. That may be on the political backburner now, but Mr Mackellar reckons less reliance on chemicals makes sound economic and environmental sense.

"Its a big decision to completely cut out chemical weed control," he admits. "But with the agricultural climate as it is, we felt there was no alternative. We have to try and show the public that we are growing crops without herbicides on them."

Savings in herbicide and fertiliser as well as the yield increase mean that the £18,000 investment in the high output comb harrow has been paid back in one season. "This year we should be in profit," he says.

Mr Mackellar grows 290 acres of wheat, 300 acres of barley, and 84 acres of oats, which serves as a break crop. Soil on this scenic and undulating landscape not far from Stafford is mild clay to black peat and is not ideal for growing cereals. The farm also runs a flock of 320 North County Mules on 150 acres of long-term grass leys. The remainder of the farm is down to set-aside.

The Opico comb harrow is made with a moulded tube frame with beds of spring tines fixed individually onto chains. Each individual bed of spring tines has six rows of adjustable tines. The harrow bed is easily adjustable with a lever.

Good eye

"It requires quite a lot of skill to understand how to use it – there are 10 different settings ranging from very aggressive to very light," says Mr Mackellar.

Judging too when the crop needs weeding also requires a good eye: "It all depends on how fast the weeds are growing – I wouldnt entrust the job to a contractor. For instance, I am hoping the weather is going to turn fine so that I can get on to my crops in the next week or so and then it may be a case of mechanical weeding every week," he says.

He doesnt worry about weeding every week or fortnight because he can do about 60 to 80 acres an hour: "That adds up to just £2.50/acre," he says.

What about damage to the crop? "Its not a problem if you have the setting right and what I like about this Hatzenbichler weeder is that the tines are incorporated in the machine, unlike other makes, so that it does not rip up the stems of the crop," adds Mr Mackellar.

He reckons that the comb harrow has left some fields as clean and weed free as when he used to apply IPU, much to the frustration of his agronomist.

"Bearing in mind the atrocious weather conditions experienced last year, I was extremely happy with a 65% weed control," he says. "Obviously an 85% result would be even better but well need drier conditions so that we can use the machine every two weeks.


"I work with my wife and son so we have to make the equipment perform to its full potential," he says. "We bought the machine in the autumn of 1998 but bad weather conditions meant it stayed in the shed until 16 March 1999.

"By the spring the weeds had a hold on the wheat crop but the comb harrow kept them in check, knocking most of them out in one pass.

"Because of the capping caused by the wet weather we used more pressure on the comb harrow to help break up the soil pan. A week later there was a marked improvement in crop health, which eventually resulted in a significant increase in yield," he says.

He also reckons on removing all the cleavers in three passes. Chickweed is more difficult to eradicate but can be kept under control without detrimental affect to crop yield or quality. It is important, Mr Mackellar stresses, to harrow the land every two weeks.

"In a normal year we go in at the beginning of March," he says. "The machine can achieve 60 acres an hour so we can afford to make more passes and still save money. Also, rain or wind does not reduce the opportunity to make best use of the equipment. This is not the case with agrochemical spraying, he points out.

"We can achieve as good a result from using the comb harrow in three passes for oats, three for barley and five for wheat. Considering the amount of land covered, adopting a mechanical weeder option is not a problem."

Environmentally, another bonus has been a marked increase in the bird population on the farm, especially skylarks and lapwings.

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