7 March 1997

Knock weeds then crop gets fertiliser

By Amanda Dunn

INTERACTIONS between crop nutrition and weed management can bring big benefits to integrated farming systems, says Dr Geoff Paulson, head of agronomy at HydroAgri, one of the collaborators in the Focus on Farming Practice project.

The aim of an integrated approach is to prevent weeds benefiting from fertiliser or soil nitrogen whilst the crop gains competitive advantage. Applying sub-lethal doses of herbicide before top dressing gives crops this opportunity, he says.

The idea is being tested at the FOFP site on CWS Agricultures site at Stoughton in Leicestershire.

"Before the main dressing of fertiliser, well look at the range of weeds and decide whether we need to kill them or just keep them in their tracks," explains project manger Alastair Leake.

"The classical situation may be a combination of cleavers and chickweed. First well apply an Ally/Starane mix at 25% of the recommended rate to knock them and then well put on the nitrogen. While the weeds are stunted, the crop has the chance to makeoptimum use of the fertiliser."

Profitability can and mustbe maintained, says MikeCalvert, CWS Agriculture generalmanager.

"Focus on Farming Practice has been running for three years, and results to date indicate that it is possible to maintain an economic yield," he says. Early indications suggest a yield penalty of just 0.2t/ha in winter wheat.

Hitting weeds with a sub-lethal dose of herbicide, then giving the crop a strong push with nitrogen, could give acceptable weed control, suggests Hydros Dr Geoff Paulson.


ICM TRIALS


Advantages

&#8226 Maintains farm income.

&#8226 Low unit cost of production.

&#8226 Less active ingredient applied.

&#8226 Environmental benefits.

&#8226 Lower commodity prices favour system.

Disadvantages

&#8226 Greater knowledge and management input.

&#8226 Tolerating weeds mayincrease weed seed bank.

&#8226 High commodity prices favour conventional, high yields.