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Spray Costs Down Yields Up with Comb Harrow In Northants

Northants arable farmer Robert Chapman has achieved significant reductions in spray costs as well as increased yields in his winter wheat through the use of an OPICO Comb Harrow as a viable mechanical alternative to chemicals for weed control.

Mr Chapman, who farms 344 ha (860 acres) at South Lodge, Barnwell near Peterborough, purchased the 12 metre Comb Harrow in 1992 and subsequently increased its size to 18 metres. Over the years the machine has covered more than 10,000 acres and Mr Chapman needs no persuading that it plays a key role in his weed control.

"We bought the machine because it looked a useful tool which would help us cut our spraying costs", he said. "Our experience is that you can't do without the sprayer entirely - but the Comb Harrow works really well in conjunction with it".

Cropping at South Lodge comprises some 500 acres of winter wheat plus 148 acres of spring beans and 190 acres of winter rape. The Comb Harrow is used in all the crops, but its principal and most successful application is controlling weeds in the wheat.

"We use a pre-emergence spray, such as IPU in the autumn and then in the spring instead of applying herbicide we use the weeder," says Mr Chapman.

"To make the machine work well you need about two inches of frost mould in the wheat crop so that the tines can pull the weeds out. We have been running through the wheat once in the early spring, then again at the end of April / early May. This pulls all the dead leaves out and suppresses the weeds. It will also break up capping and encourage good crop cover to smother the weeds.

"One year," recalled Mr Chapman, we had a 40 acre field where the blackgrass had run up to try to get above the wheat. Its shallow rooted and the harrow hooked a lot of it out."

Tine angles are varied according to ground conditions, how high the crop is, and forward speed. "If you have your tines set too hard and the forward speed too fast, you'll bury your wheat. So you set your tines and forward speed accordingly."

Output of the 18-metre machine is a comfortable 100 acres per day - "probably more in good fields. Sometimes you can do 3mph, in other situations you can get up to 4 - 4.5."

This year Mr Chapman calculates he has saved £2.50 per acre over 200 acres of wheat where the Harrow was used instead of the sprayer. He stresses, however, that the use of the Harrow varies from year to year - there is no set pattern with the machine. "Some fields you can use the weeder and other fields you have to use the sprayer. The two work together."

For two years running, in 1996/97, yields from 170 acres where the weeder had not been used were lower by 1 cwt per acre using the same variety - Hereward - and in the same heavy clay. The results were confirmed on the farm's own weighbridge.

The Comb Harrow has also done "a fairish job" controlling a serious cleaver problem in the rape, added Mr Chapman, and has been used to good effect in the spring beans.

Weather, he emphasises, plays a critical part. In 1998 Easter Flooding restricted the use of the machine to 50 acres.

But used when the ground and crop are dry, Mr Chapman finds that the Comb Harrow is a fast, effective and cost effective method of weed control.

June 1999.