Agriculture Reference
In-Depth Information
560 kilos of carbon per hectare per year - a figure which is in line with IPCC and other
mainstream projections, though far less than that anticipated by the likes of Yeomans and
Jones. This would offset 23 per cent of the UK agricultural GHG emissions, or about 1.75
per cent of all our GHG emissions. Not that much really, considering it would involve a
massive change in land use and diet.
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Azeez's discussion of the 39 studies, as well as other research, paints a clear picture of
what factors help to make organic farming more effective at retaining soil carbon:
(i) Converting arable land to grass;
(ii) Use of legumes to bring in fertility;
(iii) Mixed arable farming systems where arable is alternated with ley;
(iv) Use of catch and cover crops;
(v) Application of biomass in the form of compost, because much of the carbon is se-
cured in stable form as humus;
(vi) Application of manure in solid form rather than as slurry;
(vii) Use of straw in manure (which contains sufficient nitrogen for healthy decom-
position) compared to ploughing it in;
(viii) More biomass in the form of crop residues (eg longer straw) and weeds.
(ix) Avoidance of chemical nitrogen, on the uncertain grounds that it inhibits benign
microbial action, and discourages deep rooting;
(x) Avoidance of some other chemicals such as herbicides and the wormer avermectin.
All of these, except (ix), are well supported in the scientific literature, though it is usually
possible to find exceptions that demonstrate the contrary. Azeez also concludes that the
main argument levelled against organic farming in respect of soil carbon - that it cannot
easily operate minimum tillage systems which rely upon herbicides - carries little weight
in the UK. In this she is supported by scientists at Rothampsted and at ADAS who estimate
that the soil carbon benefits of minimum tillage are modest, precarious and may be com-
Most of the factors listed above are not exclusive to organic farming and many can be
and sometimes are practised by non organic farmers, but they are either integral or heav-
ily associated with organic farming. The first four are probably the most effective because
they involve the roots, as opposed to straw, manure and compost, all of which are derived
from the shoots (although (v) the use of compost, particularly associated with Biodynamic
farming techniques, performs very impressively). The first three of these are all integral to
grass farming, either pure livestock or mixed livestock and arable with leys, and to a large
extent that is what Azeez is gunning for: 'Reversing the trend of intensification of dairy
farming, reversing the expansion of pig and poultry farming, halting imports of intensively
produced chicken and pork, and reinvesting in grass-based livestock systems on the large
areas of existing farmland'.
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