Agriculture Reference
In-Depth Information
'When chemical use is added to intensive cultivation, which exposes and oxidizes the hu-
mus already in the soil it is easy to see why soil has become a huge net source rather than
a net sink for the atmosphere.'
Unfortunately nothing is ever that easy, least of all soil science. Since Dr Jones provides
no references to support any of this, I looked on the internet. The first article I turned up
was by researchers in Wisconsin attempting to test the hypothesis that mycorrhizal coloniz-
ation would be higher under organic dairy and grain farming systems, than under continu-
ous corn receiving chemical fertilizer. They found precisely the opposite: 'This study found
that mycorrhizal colonization was not suppressed but actually enhanced in the continuous
corn system. These results were contrary to the initial expectations … Lower mycorrhizal
levels were observed in the organic managed systems.' The authors suggest that levels of
fungi in the organic soils might have been lower because more tillage was used. They ob-
serve:
The complexity of nature, especially that part of nature which lies underground,
makes the study of the effect of farming systems on root biology a challenging pro-
position. The current knowledge of soil biology can be illustrated by the fact that soil
ecologists cannot explain the feeding strategies of more than 90 per cent of soil bi-
ota.
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Organic Matters
However, the Wisconsin study is probably the exception rather than the rule. In Novem-
ber 2009 the Soil Association published its long awaited report on 'Soil Carbon and Or-
ganic Farming', by Gundula Azeez. This is a monumental piece of work, not so much on
account of its main text, which is 130 pages long, but because of its 1288 references, cover-
ing 60 pages. Azeez is just as messianic in her advocacy of organic carbon farming as any
of the enthusiasts discussed above, but is more measured in her assessment of the potential
benes ts, and more diligent about providing evidence and sources for her conclusions. For
anyone struggling to get their head round the complexities of soil carbon, this report is like
a Baedeker, though one cannot be sure to what extent Azeez may or may not have selected
her data to suit what was clearly her brief - to show that organic farming sequestrates sig-
nificantly more carbon in the soil than chemical farming.
Azeez carries out a very useful analysis of 39 separate studies comparing soil carbon se-
questration rates on organic and non-organic farms in Europe, the USA, Australia and New
Zealand. In 32 of these, soil carbon levels were higher under an organic regime, and on av-
erage organic farming had 20 per cent higher soil carbon levels than non-organic farming,
and 28 per cent in Europe. From this, Azeez projects that organic farming could sequestrate
