Lessons from a decade of system analysis
Lessons from a decade of system analysis
By Andrew Blake
CROP choice and field margin management far outweigh the effects of different farming systems on wildlife, according to 10 years of work at Boarded Barns Farm in Essex.
The study, which was conducted by Aventis CropScience, compared conventional, organic and integrated approaches on a commercial scale. It found that active management can definitely enhance biodiversity. But interactions between soil type, crop, cultivation and seasonal changes are highly complex.
"What may be good for one species may be bad for another," says Steve Higginbotham, stewardship manager for Aventis.
As expected the reduced cultivations of an integrated approach boosted earthworm numbers. But there was little difference in bird and small mammal populations between organic and conventional methods.
Wheat grown under all three systems was equally nutritious. But low protein in crops produced organically led to unacceptable loaves, says Mr Higginbotham. Blind tasting at the Campden and Chorleywood Research Association also suggested bread from conventional and ICM crops tasted "fresher".
"On a number of occasions there was mustiness reported in the organic samples." That could be due to fungal spores, he suggests.
Criticising the view that organic methods represent the only sustainable way ahead, the Game Conservancys Nick Sotherton highlights the shortage of research results to show how unconventional methods, including ICM, can help arable farmers.
There is growing evidence that they can, he says. "But we need more data, especially on the mechanisms at work." Grassland farming is potentially more harmful to biodiversity, he adds.
"People who are hell bent on turning the brown areas of arable green are making a mistake." Ryegrass leys can be more hostile to wildlife than cereals, he explains. "I am also sick to death of people saying it has to be organic or nothing."
Biodiversity enhancing features like field margins, crop edges, beetle banks, and set-aside are common to all farms irrespective of their methods, he points out. *
Growing organic weed burden
Weeds became increasingly troublesome under organic farming at Boarded Barns farm. Despite lower wheat yields the first five years of organic production were very satisfactory due to prices of up to £200/t, says former farm manager Lister Noble. "The very first crop surprised us all. It did over 5t/ha compared with the conventional at just under 9." But increasing perennial weeds saw a steady decline in organic output from 1996. By 1999 the average was down to 4t/ha (1.6t/acre).
By last year the first field, which had initially been weed-free apart from some timothy from a previous ley, had become a jungle of docks and thistles. Thistles in beans also meant intended following wheat had to be replaced by a clover ley, says Mr Noble.
"A friend of mine has been forced to pull out of organic farming because of weeds."