The opinions, beliefs and viewpoints expressed by the author of this five-part blog series do not necessarily reflect the opinions, beliefs and viewpoints of Benton Soil & Water Conservation District representatives.
Part 1: Introduction to Soil Carbon Sequestration
Improving soil and solving climate change have something in common; increasing soil organic matter helps solve both problems at once.
Let’s start with the basics. We know there’s too much carbon dioxide (CO2) in the atmosphere. And, the way soil has been treated has caused an estimated loss of 100 to 200 billion tons of soil organic matter in the last century or so.
There is a finite amount of carbon on the earth which is divided between various pools including oceans, atmosphere, living organisms, and soil. To put it simply, we have too much in the air and not enough in the soil. There is all kinds of research going on into technical, mechanical ways to remove CO2 from the air. We hope the smart people working on these solutions are successful. However, most people don’t know about soil’s incredible ability to store carbon.
The top 3 feet of soil holds more carbon than the atmosphere, plants, trees, and animals combined, and is capable of holding many times more.
Fortunately, there is growing awareness of the oldest method of CO2 removal from the atmosphere – photosynthesis. Remember 9th grade biology? Plants breathe in CO2 and use that carbon for growth and life. This growth creates organic matter (OM) which is around 50% carbon.
The biomass created by living plants is one form of OM. The accumulated amount of dead roots and parts of plants that fall to the ground adds to the total amount of carbon in the soil. We can collect some of this OM and put it on the soil as mulch or compost. However, there is one drawback to using this method to increase OM levels. Organic matter put on the soil surface tends to be short-lived, and it decomposes faster than OM that is protected underground. For example, dead, subsurface roots tend to stick around longer than surface OM.
Organic matter does decompose and turns back into CO2. This is necessary for life, because the decomposition process releases nutrients that plants need to grow. However, if more OM decomposes than is added, soil organic matter levels drop. In a nutshell, soil organic matter levels are a balance between the amount of organic matter that is added and the amount lost.
In the next post, we will explain a very important but little-understood way that plants add carbon to the soil.