The different speeds of paddock carbon

Have you ever considered that all the different forms of carbon in a paddock are moving at different speeds?


Paddock carbon moves at different speeds depending on what type it is.

The first two columns drew attention to the difference between carbon flows and carbon stocks. It was explained why the success of rural producers relies on how well their management promotes the flow of carbon through their paddocks. Now I am going to add another level of refinement to this discussion of carbon flows in the paddock.

Given that all carbon in the paddock flows, some quickly and some slowly, maybe we should discuss carbon in terms of the speed of the flow, rather than simply stocks versus flows.

Some of the carbon that enters a paddock moves very quickly through the paddock on its way back to the atmosphere. Some stays a bit longer and some of the carbon is moving very slowly.

Different speeds = different functions

This suggestion of thinking speed of carbon may seem like a radical proposal, however it brings the discussion of land management back to exactly what all the different forms of carbon are doing. The faster moving carbon has a different role in production and landscape health to the slower moving carbon.

Short term resilience is linked to the faster moving carbon and long term resilience is linked to the slow moving carbon, as will be explained in a later column.

To understand the concept of different speeds of carbon, we have to go back to the idea of individual carbon atoms entering the paddock via photosynthesis then heading off in all different directions, before finding their way back to the atmosphere. Some quickly, some slowly.

Carbon atoms form different compounds as they keep moving. As you know, it is consumption of carbon compounds by life above and below ground that moves carbon around the paddock. Generally, the more times carbon is consumed, the slower it moves and the simpler carbon compounds become. 

Increasing the speed of faster moving carbon improves profit

There is a reason why a paddock is more productive when the faster moving carbon moves even faster. In the case of soil, everything that is joined to carbon, such as nutrients, becomes available to plants sooner if the carbon moves faster.

Apart from flowing through the landscape after entering plants, carbon also flows through sheep and cattle. Increasing the speed of carbon through these ruminant animals increases profits by getting them to market sooner and reduces the production of methane per kg of production. 

What speeds up the faster moving carbon will be discussed soon.

Carbon flows in the paddock involve virtually none of what we term long term carbon (the slow moving carbon). 

If you want to increase production in the short term, it is the faster moving carbon that increases production, not slow moving carbon. In the case of soil carbon, it is accepted in the scientific community that stocks of long term soil carbon are slow to change, which reinforces the point that long term carbon can’t to be responsible for short term increases in production.

Examples of different speeds of carbon movement

The carbon that leaves the paddock in the quickest time after entering is root exudates. Root exudates are carbon based compounds (sugars, amino acids and organic acids) released by the roots of plants. Soil microbes that are fed by root exudates procure nutrients that plants require. A good example of this process is microbes making phosphorus soluble and ready for plant use. This carbon leaves the paddock within hours of entering i.e. it is very fast moving carbon. Plants only release this liquid carbon into the soil when they are growing (photosynthesising).

Carbon above and below ground in plants is some of the faster moving carbon. However, the carbon in the stems will move slower than the carbon in leaves when it enters a cow or the soil.

The slowest moving carbon is soil humus and charcoal. It is virtually not moving at all.

Conclusion

Carbon is the organiser as it flows through the paddock.

It is the faster moving carbon that runs down quickly and needs constant replacement. Ground cover is a good example.

Carbon trading is more interested in the slow moving stable carbon, while the decisions rural producers make relate directly to the faster moving short term carbon.

Next week’s discussion: “How carbon and nitrogen work to together”

Alan Lauder



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