Microbes do most of the work to decompose organic matter which is added to the soil. They take carbon from the soil organic matter and respire about two-thirds of it as CO2, which then escapes to the atmosphere. The microbes use the rest of the carbon to grow and divide and so the microbial biomass builds up in the soil and essentially become part of the long-term pool of soil organic carbon.
The carbon going into the soil organic carbon pool is impossible to see and difficult to measure, in the same way that the money flowing from the poker machine to the bank is hidden. In contrast, the carbon which is lost as CO2 escaping to the atmosphere is easy to quantify with simple colour-change tests, just as the pay-out from poker machines can be seen by the punter because it is trumpeted by bells and whistles.
The peculiar aspect of the analogy is that CO2 emissions to the atmosphere affirm that the microbes are active, and that soil carbon sequestration is happening. Great news – which provides encouragement enough to keep adding organic matter to the soil. And as long as organic matter is added, the microbes will keep taking small amounts of carbon into the long-term soil organic carbon pool. It is a perverse winning strategy.
