Extremes under investigation

PUSHING THE boundaries is how Unilever’s sustainable agriculture research manager Jos van Oostrum describes some of the husbandry strategies being evaluated on the food giant’s Colworth Estate at Sharnbrook, Beds.

Drilling in wide rows, mechanical weeding and up to an 80% cut in fertiliser use may appear radical, but valuable lessons are being learned, he says.

The aim is to strike a balance between zero environmental impact and commercially viable farming. Over the past five years, rotation, pesticides, fertilisers, crop timing and field margin management have all been scrutinised, as well as alternative cultivation methods, including controlled traffic.

The Colworth Estate farm is run commercially, growing winter wheat, oilseed rape and winter beans, with the sustainable project accounting for 60ha, including vining peas – a key crop for Unilever, which owns Bird’s Eye.

Stale seed-beds

Extreme husbandry peaked at the outset. “No herbicides were used, just stale seed-beds,” says Mr van Oostrum. “We drilled cereals in wide rows, 25cm apart, and used mechanical weeding.”

Where fertiliser rates were maintained weed counts were overwhelming. That prompted the adoption of band spraying, aimed at the crop row, plus inter-row mechanical weeding. “This allows us to apply herbicides in a targeted fashion, as well as reducing the total amount.”

The approach has a future, he believes. “The weed control is better, herbicide use is more than halved and leaching is reduced to well below EU drinking water limits. We also found an average of 20kg/ha of nitrogen was mineralised by the tine action, giving us the chance to cut fertiliser use.”

Biodiversity also benefited, reports Mr van Oostrum. “There was more food for birds, both in terms of seeds and insects, and farmland bird numbers have risen consistently, by around 35%.”

Fertiliser use in cereals is reduced by up to 80%, omitting an early spring dose, because nitrogen is released by weeding. “Stem extension (GS32) is the first timing, and then we only apply around 50kg/ha. After that, applications are adjusted to ensure nitrate leaching is within EU drinking water limits.”

But Innes McEwen, Colworth farm manager, says that around 75% of biodiversity benefits stem from rotation changes and pro-active site management, including grass and flower margins managed for biodiversity. Reduced crop inputs explain the remaining 25%.

“The non-cropped areas have made a major contribution. Management of margins and hedges has boosted bird and invertebrate numbers considerably, with complementary but small improvements in food provision in crops due to changed in-crop management.”

Including some spring cropping has allowed weedy stubbles and cover crops to create a more varied crop mosaic. “That’s been the single most important change for bird densities.”

The biggest practical challenge has been weed control, says Mr McEwen. And it can affect wildlife adversely. “Where a wheat crop was swamped with wild oats, there was no value for birds at all. The wild oats were too dense for birds to land.”

Blackgrass control

Blackgrass control has been impossible without herbicides. “Inter-row weeding didn’t work, even with an autumn pass and a further three or four in the spring.”

Wide drilled wheat results have been variable, he adds. “Where the weeds have won, yields have been as low as 3.2t/ha, where we would expect 9.25t/ha. But where the extreme practice has worked, wheat has yielded 7.5-8.25t/ha, often providing a better gross margin than the conventional approach.”

Controlled traffic farming, where tramlines are set using GPS technology, is also being assessed. “We’re in a unique position to be able to do these things,” Mr McEwen admits. “And while some of them might not be practical for commercial farms at the moment, they provide unique insight into the challenges and opportunities faced by UK farmers.”

Indeed, striking the right balance is the key, adds Mr van Oostrum. “The idea is to find out whether some of the so-called extreme practices” are more sustainable in the long-term.”


* Radical approach tests limits

* 75% wildlife benefit from rotation/site management, 25% from in-crop actions

* Water quality improved

* Weedy stubbles before spring crops bring big benefits

* Band spray and mech weeding potential

* Fertiliser regime must change too