The Nexus Between Carbon, Nitrogen and Biodiversity
This article is part of a series of articles by Carbon Sync’s team members and collaborators. This week’s article is by Joel Williams from Integrated Soils and Kevin Elmy from Cover Crops Canada.
Nature is a wonderful thing to observe. Incredibly complex yet so elegantly simple. Ecosystems working within ecosystems, supporting life on Earth as we know it. To be involved with agriculture puts you on the front row to observe it.
Life on Earth is based on photosynthesis, plants capturing light, combining carbon dioxide and water to create glucose and oxygen. This is the basis of energy transfer for the rest of the living organisms. Plants then are able to take this carbon chain, add different molecules to it to create different types of nutrient sources, like amino acids, proteins, carbohydrates, oils, secondary plant metabolites, just to name a few. These are used for the plant’s growth, some exudates to feed the above-ground microbes, and some get released into the soil to feed the soil biology. Plants are the primary producers in our food chain. The key to the plant’s success of obtaining the rest of the nutrients it requires is the soil microbiology.
Carbon is the building block that nutrition is built around by the plant that is transferred to all living beings. Carbon is cycled through living organisms; it is used for growth and is respired back into the atmosphere. Through human intervention, the carbon dioxide levels in the atmosphere have been increasing, mainly due to burning fossil fuels that release carbon dioxide. In agriculture we have the opportunity to use the soil as a sink to store carbon in our soils by growing a diverse array of plants, reducing our tillage, reducing the amount of synthetic inputs, and managing grazing in a more effective way.
The other nutrient that dramatically influences plant growth is nitrogen. Nitrogen is one of the key molecules in proteins, as well as other plant metabolites. It is also one of the largest expenses on crop production farms. When not properly applied or if it’s under-utilised and is allowed to volatilise into the atmosphere, it adds to the greenhouse gas load. One of nature’s solutions to this is planting legumes and rhizobia, a symbiotic relationship that allows atmospheric nitrogen to be captured and converted to plant-available forms. Nitrogen can also be locked up in the soil organic matter. Just another reason why building soil organic matter is so important.
Successful plant growth will result in plant reproduction, by seed or rhizomes. In order to get the nutrients that the plant needs, the soil microbes will work with the plant in exchange for carbon in the form of root exudates. As the roots push down into the soil, it continues to release root exudates, allowing microbes to thrive deeper in the soil. When the plant matures, root exudates stop and the microbes either die or go dormant. This is one of the main ways carbon is sequestered deep in the soil profile in a very stable state, resistant to being released back into the atmosphere.
Without adequate nitrogen to ensure normal plant growth, carbon cannot be stored deep into the soil. Without carbon, organic matter cannot be built up to help store nitrogen in the soil. Imbalances between the two can cause issues. Over-application of nitrogen will cause the soil microbes to search for carbon to balance their diet, which they can find in the soil organic matter, thereby decreasing it. Adding too much carbon at one time will cause the microbes to tie up any free nitrogen in the soil.
By supplying the soil with a diverse cover of plants that feed the soil, more diverse microbes are supported, ensuring that there will be microbes that are adapted to grow in almost any condition. Active microbes will ensure nutrient availability and plant health.
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