Biodiversity can inflict a host of hidden costs
Biodiversity can inflict a host of hidden costs
By Louise Impey
INCREASING the amount of biodiversity on arable farms brings a host of hidden costs.
Experience on the 320ha (800-acre) Loddington Estate in Leics showed small fields and a move away from block cropping added to costs, Alastair Leake, of The Allerton Trust, told delegates at a recent BCPC conference at IACR-Rothamsted.
"Permanent set-aside strips mean you lose a break crop in the rotation and an early entry into a first wheat. A weed control opportunity is also forfeited."
The creation of two new headlands within the field, with their associated yield penalties, was another loss. "And it means even more measurements have to be done for the IACS form."
Work efficiency also suffered, because there was constant movement of men and machines around the farm and separate agronomy decisions needed making. "More agrochemicals have to be in stock and there is extra paperwork."
Smaller fields also reduced yield. "We have calculated that 0.38t/ha is the penalty. Then there is additional hedge cutting at £16/hour."
Establishing wild bird cover on set-aside land works out at £15/ha. "There are time and labour issues as well – Loddington is unusual in that it employs two men on 800 acres. That is a luxury in this climate."
Although organic farming supported higher levels of bio-diversity, it was the techniques characteristic of the farming system that exerted the influence, not the input regime, he said.
"Conventional farming uses large blocks of crops, some of which are early sown. There is little spring cropping employed and weed control is done by chemicals.
"Integrated systems have smaller cropping blocks and more diversified cropping. There is still very little spring cropping and both chemical and biological weed control techniques are employed."
By contrast, organic farming uses small crop blocks and more varied cropping, for fertility building purposes.
"There is late sowing and spring cropping too. But weed control is always non-chemical."
Organic weed control methods could be counter-productive where the aim was to increase biodiversity, said Mr Leake.
"The methods are almost always non-selective. Using a flame weeder or a harrowcomb will take out all the weeds, regardless of their value as a food source for birds."
Non-inversion tillage was preferred for supporting invertebra-tes. "Again, it cant be done in organic systems, which rely on ploughing to bury weed seeds and mineralise nitrogen. There are pros and cons in every type of farming." *
New headlands (below) are among the hidden downsides of diversifying to encourage wildlife, says Alastair Leake.
• Smaller fields = higher costs.
• Reduced break crop scope.
• Extra headland penalties.
• Time and labour issues.