After 27 years of comparing side by side conventional and organic farming system, the US Rodale Institute has found that soil carbon levels have increased by almost 30 per cent in the organic fields, and hardly changed in the conventionally farmed soils.

The Rodale research team has found that there is a very high correlation between higher soil carbon levels and higher amounts of mycorrhizal fungi.

The fungi produce glomalin, a glue like substance that holds carbon tightly to clay and minerals in the soil, forming larger aggregates that are more resistant to breakdown.

Researchers also found that soil carbon levels were higher in the manure-based organic system than in the legume-based organic system.

Application of soluble nitrogen fertilisers in the conventional trial stimulated more rapid and complete decay of organic matter, sending carbon into the atmosphere instead of retaining it in the soil.

Organic farming also helped reduce emissions because cover crops or compost were used instead of chemical fertiliser derived from fossil fuels.

As well, Rodale’s rotational no-till organic crops used up to 75pc less fossil fuel than its standard tilled organic crops.

Corn and soybean yields in the organic system matched the conventional systems except in drought years, when the organic system yielded about 30pc more corn because the soil aggregates were able to hold more moisture.

Rodale Institute says these findings have huge implications for future agriculture, given the push to store rather than emit carbon, and European scientists agree.

In a recent review publication, Organic farming and climate change, they write "Organic production methods emphasising soil carbon retention are most likely to withstand climatic challenges particularly in those countries most vulnerable to increased climate change.

"Soil erosion, an important source of CO2 losses, is effectively reduced by organic agriculture."

Read the Rodale report at:
www.rodaleinstitute.org/files/Rodale_Research_Paper.pdf (1.8 mb, PDF)

Read the European report at:
www.intracen.org/Organics/documents/Organic_Farming_and_Climate_Change.pdf (1.3 mb, PDF)