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.

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.

"It's 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 fertilisers 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.

He doesn't worry abour 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? "It's 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.

"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.