Mike Kiely commentary on soils

This post is responding to my post in April.

Michael Kiely said...

Good to see agriculture getting some attention. A few facts from Australia, which has many advanced 'carbon farmers' sequestering carbon dioxide via native perennial grasses, shrubs and trees: 1. If the world stopped emitting CO2 today there is already enough up there to drive us through the 2°C limit into climate chaos. 2. Only photosynthesis can extract the 'legacy load' of 200 years worth of emissions. 3. It would require 7 planet the size of Earth entirely covered in forests that never died or fell down or burned to do the job. 4. An acre of pasture can hold more carbon than an acre of forest. 5. Soil already holds 1500GT of Carbon vs 750GT held in the Air and 650GT in Vegetation. 6. Farmland (mainly pasture) covers 65% of the landmass of the Earth. 7. A change in land management from conventional farming to carbon farming is easy when farmers can trade the credits for the carbon they store in their soils. 8. Farming techniques that capture and store carbon stimulate soil biology and restore health to soils, waterways, and farmland ecologies. Biodiversity increases. Resistance to pests increases. Soil productivity increases. Reliance on chemical inputs falls. Profits rise. 9. Life's beautiful.

I am personally not convinced that all pasture land holds more carbon than all woodland although that is certainly true in selected cases. Unfortunately, most original grassland has been plowed and a lot of the carbon bank has been released. The most egregious example of this is the area of the buffalo commons in western North America. It would actually be nice to see extensive carbon measurement on soils done on a global scale so as to establish benchmarks.

A quick review of he literature reveals that that is not so easy yet. Which means that there is currently a lot of educated guessing going on.

Woodland has a potential to ultimately store fifty to one hundred tons of carbon for every acre without been clever about carbonization. We are referring to temperate woodlands. Dry land environments are not nearly so cooperative, although the tropics can easily double these figures.

Agricultural soils usually deteriorate down to a layer that is perhaps several inches in thickness for a number of reasons, but mostly to do with the shallow root systems of the annuals used as our primary crops. I grew up with a working six inches of soil were once stood a maple forest that certainly carried a ton of carbon for every tree. This includes the root ball.

In all likelihood the soil itself still contains similar amounts of carbon as the original forest soils although the science is indicating a 35% reduction. What is missing is the tree itself that drew up nutrients from deep down and dumped them every year onto the surface. The elimination of the tree's root system then shrank the soil layer.

One needs to be reminded that the tallest and largest trees(Douglas firs and the like) on the planet grow in the mountains on which soil cover is often negligible. We can have our cake and eat it too by the simple expedient of promoting silviculture on waste and marginal land and employing carbonization to enhance crop lands.

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