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What Causes Carbon Soil & How Do We Increase It?

Close up of a sprout of grass growing in the soil

What is Carbon?

Carbon is a term that has become increasingly popular over the past decade. From climate activists focusing on the carbon dioxide levels on Earth to politicians creating their platforms around environmental carbon policies, it sounds like carbon is an extreme detriment to everything on Earth.

One area that significantly benefits from carbon is soils.

In this article we will discuss how carbon is stored in soil and how soils can become an excellent resource for stabilizing carbon dioxide levels on Earth.

Current State of Carbon Storage in Soil

Scooping up soil

Although soils benefit dramatically from having carbon in them, it has been a challenge to maintain carbon in our soils. Currently, the “Earth’s soils contain about 2,500 gigatons of carbon—that’s more than three times the amount of carbon in the atmosphere and four times the amount stored in all living plants and animals”[i].

While this number sounds substantial, activities such as mining fossil fuels, developing land, clearing forests, tilling, fallow fields, and reducing organic matter in the soils have all resulted in depleted soils that cannot hold or sequester much carbon.

The soil on Earth today holds significantly less carbon than it did decades ago. Soils have lost 50-70% of the carbon they once held[ii]. As a result, more carbon is being stored in oceans, increasing its acidity and harming marine life[iii].

The rest of the carbon dioxide has begun creating a shield around the Earth that traps in heat resulting in the global warming that has taken place the past few decades. With humans and oceans begging to reduce the carbon dioxide on Earth and soils wanting more carbon, society is presented with an excellent opportunity to rebalance its carbon levels.

How is Carbon Stored in the Soil

We have discussed the importance and opportunity of storing carbon in soils, but how is carbon actually stored in the soil?

Diagram of how plants sequester carbon before and after termination
Photo: University of Nebraska-Lincoln / Institute of Agriculture and Natural Resources

Carbon enters the soil via photosynthesis. All plants on Earth engage in photosynthesis where they take sunlight and carbon dioxide (CO2) from the atmosphere, separate the carbon from the oxygen and release the oxygen back into the atmosphere via respiration[iv].

The carbon molecules are then traded along with sugars to microorganisms in the soil in which microbes trade whatever nutrient they possess for the carbon and sugars of the plant. In this relationship the plant is able to obtain vital nutrients for growth (such as nitrogen, and potassium) and the microbes are able to feed on the carbon and sugars being fixated by the plant.

Carbon is a medium of exchange for life underground. Plants obtain all of the nutrients and pest protection by trading carbon. Microbes, on the other hand, live off feeding from the carbon and sugars the plant provides.

Benefits to High Carbon Levels in the Soil

soil with grass sprouts

What are the benefits of storing carbon in the soil?

High carbon levels underground pose many benefits to soils and crops. Carbon and soil quality form a feedback loop in which the more carbon in the soil the higher its quality and the higher the quality of soil the more carbon it can hold.

By fostering high populations and diversities of microorganisms in the soil, soils will improve their organic matter and soil composition[v]. Cottage cheese textured soil enables lots of space between soil clusters. This space is excellent at storing and draining water, holding carbon, and creating pathways for root systems[vi].

Poor quality soils with minimal organic matter and lots of compaction struggle to hold both water and carbon due to the convergent soil particles. Through healthy, carbon enriched soils, plants are able to create more intricate root systems, access water deeper into the ground, and obtain more nutrients from microorganisms. This translates into healthier crops that have higher yields and more resiliency.

Not only does this benefit plants but the entire environment. By storing more carbon in soils, oceans are able to release some carbon, rebalancing the PH levels of the ocean and humans are able to reduce CO2 in the atmosphere.

How to Add Carbon into the Soil

What are some ways to add carbon to the soil? There are three main ways to add carbon back into your soil. They are:

  • cover crops

  • increasing organic matter

  • and minimizing soil disturbances

1. Cover Crops

Person planting on a covered crop

Firstly, the only way to get carbon into the ground is through photosynthesis. The only way photosynthesis can occur is through plants. Thus, it is important to ensure your soil is constantly covered by plants.

For farmers that means planting a cover crop in between crop cycles. Not only do cover crops preserve and add carbon into the soil but they also perform a multitude of other benefits.

Cover crops prevent soil degradation, improve soil fertility, suppress weeds, and replenish nutrients and carbon into the soil[vii]. The larger the quantity and diversity of plants on a field the more carbon that can be sequestered underground.

Another strategy for improving carbon in soils is to plant perennials as they remain in the ground year over year, constantly fixating carbon into the soil.

2. Increase Organic Matter

Spout growing in mulch

Secondly, it is important to increase organic matter within the soil. Organic matter improves the fertility and composition of the soil enabling it to sequester more carbon. Organic matter can be built in multiple ways. Some of these include adding compost, manure, mulch, and microorganisms.

Composts and manure are relatively inexpensive ways to boost the organic matter in your soil. These can be found around your farm or purchased. Compost can be applied a few ways. It can be mixed directly into soil, strained into a liquid that can be used as a spray or heated into a compost tea.

The Marin Carbon Project found that a one-time application of compost increased the soil’s carbon content continually, at a rate comparable to removing 1.5 metric tons of carbon from the atmosphere each year[viii].” Regardless of the mechanism you are applying the compost it is effective at building organic matter in the soil.

Another option is to mulch your field. Although this may not be practical for all farms, mulch provides some excellent benefits to the ground. Mulch acts as an insulator where in the summer months, it retains water and cools the soil En the summer, in conjunction with providing a blanket to the ground in the winter, thus maintaining soil health[ix]. Mulch also provides nutrients to microorganisms, increasing organic matter in the soil as it decays. Additionally, mulch suppresses weeds beneath it, saving farmers time and money on pesticides.

Furthermore, a way to add organic matter to the soil is to add the beneficial microorganisms. The easiest way to apply these is by purchasing a microbial fertilizer such as Nurture Growth's bio-organic fertilizer.

Adding beneficial microbes to the soil increases the organic matter within the soil and the ability to sequester carbon. In addition to aiding in carbon sequestration, microorganisms benefit crop health and quality significantly. Microbial fertilizers increase the plants resiliency to stresses and pests. Simultaneously, microbial fertilizers promote vigorous growth and yield increases. Nurture Growth has recently received an award from the government of Ontario for its role in sequestering carbon.

Pesticides kill both good and bad pests resulting in significantly lower microbial populations in the soil. Rather, farmers should look to deal with pests in more natural ways such as microorganisms, cover crops, and mulch.

3. Minize Soil Disturbances

Rake going over a bed of soil & weeds

Another mechanism to maximize carbon levels in the soil is to minimize soil disturbances. When soil is disturbed carbon is released into the atmosphere, negating all of the steps done to increase the storage capacities of the soil.

Through practices such as tilling and fallow fields, soil becomes eroded. This significantly reduces soil organic matter and carbon levels underground. There is no sense working towards building carbon levels in the soil if the soil is just going to get disrupted and release all of the carbon that has been sequestered. Rather, farmers should look to preserve the soil by adding cover crops and increasing organic matter.

Benefits of Improving Crop Quality & Quantity

Conclusively, carbon poses many threats to life on Earth. Soils provide society with an opportunity to reduce CO2 levels in the atmosphere while simultaneously improving the fertility of the soil. Through improving crop quality and quantity while reduce CO2 in the atmosphere, carbon sequestration has the potential to be extremely beneficial.

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