The Carbon Cycle

 The Carbon Cycle

Out of the three greenhouse gases discussed throughout this site (carbon dioxide, methand and nitrous oxide), carbon (dioxide) is a part of all organisms. It is the building block of life. 

As you should already know, carbon dioxide is a greenhouse gas that is made naturally. Remember: A greenhouse gas is a gas that traps the Earth’s radiation inside the atmosphere warming the Earth up (other greenhouse gases are methane and nitrous oxide).   

Carbon affects all life on Earth. The carbon cycle consists of four major interconnected reservoirs of carbon; the atmosphere, the oceans and water bodies, the terrestrial biosphere (soil, plants, animals), and sediments and rocks.

The carbon cycle is the big circle the carbon travels in and is defined as the series of processes by which carbon compounds are interconverted in the environment. In agriculture, this involves the incorporation of carbon dioxide into living tissue by photosynthesis and its return to the atmosphere through the decay of dead organisms (plant material), and respiration of plants and animals. Therefore, agriculture affects the global carbon cycle since agricultural practices and land use alter the amount of carbon stored in plant matter and soil, and consequently, the amount of carbon dioxide (CO2) that is released into (or taken up from) the atmosphere.

Plants, including agricultural crops, play a role in the carbon cycle. Carbon dioxide from the atmosphere is taken up by vegetation (crops, trees). These plants use carbon dioxide to make their own food in a process known as photosynthesis. During photosynthesis atmospheric carbon dioxide is converted into a usable form of chemical energy (sugar), and the carbon is separated from the oxygen. Oxygen gets released back into the air and some carbon gets stored in the soil. As well, as the plants use the sugar’s energy, some of the carbon is released back into the atmosphere as CO2, and the rest of the carbon is used by the plant to grow new biomass. The carbon embodied by terrestrial plants can then replenish the carbon in soil, for example, through the decomposition of fallen leaves.

Plants that contain carbon are eaten by humans and animals. The plants are digested by the animal and passed out of their system as manure. The carbon in the manure then goes into the soil. The carbon that enters the soil increases soil organic matter. Soil organic matter is the organic matter component of soil, consisting of plant and animal residues at various stages of decomposition.

Other ways in which carbon can enter the soil is through the root system of a plant, or a decomposing plant. These things help increase soil organic matter, a mix of carbon, nutrients and dead materials.

A high soil organic matter usually means that there is more nutrients in the soil making it fluffier and better for plants to grow in. This would be soil of a black or brown colour and be very sticky when wet.  In the Prairies, our natural Chernozem soils had high soil organic matter content because of the native grassland.

A low soil organic matter means that there is a low amount of nutrients to the soil. This soil is often very sandy and not very good for growing plants. The soil is often tan in colour and very sandy or perhaps a clay.

For more information on the carbon cycle and for fun activities relating to the carbon cycle, see the links below!