Putting carbon into the soil can rectify two of our global problems.
In resolution of the first plight, it is the carbon which can be taken from the atmosphere which is important. In respect of the second issue, it is the effect of carbon in organic residues on soil biology which will sustainably increase food production.
Those matters have been widely reported and are generally accepted, and it is not the purpose of this article to sanction them. Instead it is intended to say that the premise that carbon can be added to agricultural soils by organic residues should have gained real traction and investment but it hasn’t.
Let me say it again, the crucial matters are the carbon dioxide concentration of the atmosphere, and the cycling of carbon from plants to the soil to in-turn promote plant growth.
Putting a price on carbon (however it is derived) may serve to limit carbon emissions but it does not remove carbon dioxide from the atmosphere, and it does little to focus agriculture towards systems that use carbon-rich soils to produce abundant foods.
Putting carbon into soil is real ‘carbon capture and storage’ and while it is necessarily a long game it is a biologically-perfect process. As organic material decomposes in the soil part of the consumed carbon is respired by soil microorganisms to the atmosphere, and part of the carbon is reassimilated in higher-order soil organisms (that in-turn are consumed) until humus and other soil carbon fractions that are resistant to decomposition are formed.
The amount of decomposable (labile) organic matter in soil is the determining factor in both sequestering atmospheric carbon into soil and maintaining diverse and active soil microbes. Microbial activity is crucial because it results in carbon and nitrogen mineralisation and the release of other nutrients essential for plant growth.
Measuring respiration from soil microorganisms is now easy and inexpensive, and it is a critical piece of information that farmers and other land managers can use to promote carbon storage in soils and sustained production.
Two recent research papers give insights about the processes by which carbon ends up in soil. The first by Munoz-Rojas et al. (2016) describes how in restored mining topsoils, vegetation cover begets carbon in soil and microbial activity, which in-turn begets vegetation cover. The second paper by Walela et al. (2014) describes how residues whether from straw, pastures or woodlands vary the amount of active organic compounds and the rate of carbon turnover. The collective point is that carbon sequestration to soil is manageable and should be pursued in mining, pastoral and agricultural situations.
My own work (Ockerby et al. 2014) and that of my colleague (Yang et al. 2014) demonstrated the responsiveness of floral development in plants to growth. Soil microbial activity affects plant growth and plant growth determines carbon capture from the atmosphere.
© Stephen Ockerby 2017