Soil Microbes and the Global Carbon Cycle: Their Role in Soil Health and Climate

Soil microbes are important to the global carbon cycle, because they regulate transfers of carbon into, in and out of soil. Plants absorb carbon dioxide gas from the atmosphere and synthesize organic compounds, leaves, stems, roots into their metabolic system annually in the process of photosynthesis. Once these plant materials are dead or shed they are decomposed by microorganisms, and nutrients are recycled or released back to the atmosphere and the carbon is either stored in the soil or released into the atmosphere.

This microbial activity in soil is continual and determines the carbon sequestration/release balance. Some carbon is transformed to stable soil organic matter and may persist for years or even centuries while others are lost as carbon dioxide via microbial respiration. All of these processes occur in balance and are influenced by a myriad of environmental factors such as soil moisture, temperature, oxygen supply and microbial diversity.

Great Lakes Bioenergy Research Center (GLBRC) scientists have demonstrated that soil microbes react differently to the physical characteristics of the soil, especially the distribution and size of the soil pores in which decomposing plant residues reside. The results in this study reveal that microbial activity is not only regulated by the quantity of available organic matter but also is influenced by the microenvironment in which the microorganisms live. The finding of these can help scientists understand more about the global carbon cycle and give them useful information for sustainable agriculture and climate studies.

The soil carbon cycle, and how microbial decomposition works?

The soil carbon cycle refers to the cycling of carbon among plants, soil organisms, soil organic matter and the atmosphere. Agricultural soils take up a quantity of carbon through root exudates, fallen leaves, crop residues, manure, compost and other organic matter. Instead of being constant, these carbon-rich materials are consumed by microorganisms which begin microbial decomposition of organic matter.

The microbial decomposition carbon cycle is accomplished by bacteria and fungi that convert cellulose, lignin, proteins and carbohydrates into simpler molecules by releasing special enzymes. Some of these compounds are taken up by microorganisms and incorporated into microbial biomass and others add to the stable soil organic matter. While this is happening, microorganisms are respiring and emitting their metabolic by-product, carbon dioxide.

In the GLBRC study, it was shown that the ability of microbial breakdown of organic matter is highly variable between different soil pore types and moisture levels. The microbial communities, oxygen levels and water availability inside the different sized soil pores are different which affects the rate of decomposition.

The role of bacteria and fungi in soil carbon cycling

Bacteria and fungi are the main biological agents of carbon transformation under the soil surface, of which there are countless. They have long thread-like hyphae which grow in the soil, binding together organic matter and plant roots and creating more aggregation and structure in the soil. Fungi are thus an important component of the formation of stable soil organic matter which can be stored for a long time.

The diversity of soil microbes is responsible for different soil organic compounds being processed differently.Microbial activity is one of the most important characteristics to consider in assessing productive agricultural soils due to its relationship to soil changes in carbon, nutrient cycles, soil health and more.

What is the relationship between soil moisture and microbe activity and carbon release?

One of the most significant factors controlling microbial activity and soil moisture relations is water. Microorganism production of enzymes, transport of nutrients and maintaining cells requires adequate moisture. Too much water, though, can diminish the amount of oxygen available and on the other hand, too little water can inhibit microbial growth and decomposition. Within a soil profile, the combination of pore size and water and air availability produce different soil environments, which in turn lead to distinct kinds of microbial decomposition of organic matter.

They create the microsites that are essential for healthy microbial activity in soil. The larger pores allow better oxygen movement to promote aerobic microorganisms and the smaller pores prevent the water from evaporating and thus help to maintain the microbial populations during dry spells. The ratios between these environments have a direct influence on the decomposition of organic matter by microorganisms, and either carbon can be stored in the soil or released into the atmosphere.

This balance is greatly affected by agricultural management practices. Over-tilling creates soil aggregates and pore networks which are destroyed and excessively compacting the soil reduces the movement of oxygen. On the other hand, conservation tillage, organic matter amendments and cover cropping enhance soil structural properties that provide good soil environments for desirable microbial activity and carbon cycling.

Soil microbes and climate change: how are they related?

Soil microbes and climate change relationship is one of the most critical fields of environmental studies. Soils are one of the biggest carbon reservoirs on Earth as they contain more carbon than the atmosphere and vegetation combined. Soil processes that either sequester or release carbon to the atmosphere depend heavily on the microbial processes.

Microbial decomposition carbon cycle is the process in which microorganisms naturally produce carbon dioxide during the degradation of the organic materials. This is important as it helps in recycling of plant growth nutrients. Decomposition rates vary with changes in environmental factors, however. Microbial communities and the processes by which they transform carbon are affected by the warmer temperatures, modified rainfall, vegetation changes, and agriculture.

The effects of climate change on the populations of microbes is of particular interest to scientists as a change in decomposition rate could result in a change of the balance of the global carbon cycle. With increased rate of decomposition, there is the possibility for a greater amount of carbon dioxide to enter the atmosphere. 

How Novobac Soil Vigor Supports Biological Soil Management

Nowadays, productive soils are dependent not only on their chemical fertility but on their good biological activity as well. Novobac is a biotechnology business focused on biological agriculture and sustainable soil health technologies to enable enhanced soil natural processes with microbial solutions for farmers. Soil Vigor is one of its biological products developed as an organic soil amendment that will help maintain healthy soil microbial environments and the long-term productivity of the soil.

Soil Vigor is different from conventional fertilizers, which are designed to provide nutrients to the plant. Soil Vigor is designed to stimulate activities in the root zone. It is one of the modern biological soil amendments having beneficial microorganisms which helps in the mobilization of nutrients, decomposition of organic matter and re-establishment of balanced microbial communities. It can help enhance soil health by stimulating beneficial soil microbes, allowing plants to grow for several seasons.

In agricultural soils, microbial decomposition of organic matter is responsible for much of what is naturally occurring, and is driven by healthy microbial communities. Crop residues and organic amendments release nutrients that are available to plants as they decompose and stable organic matter slowly builds up. Soil Vigor encourages these natural biological processes by providing a suitable soil environment for beneficial microorganisms, not in lieu of good soil management.

It also helps to promote soil biological activity that helps aggregate and grow roots. Improved soil structure will allow more nutrients to be available, more air to pass through, and more water to infiltrate the soil, providing a space in which beneficial microorganisms can grow. These enhancements will not only contribute to the health of the soil, but also promote sustainable production systems. Soil Vigor should be considered one part of a soil health program, importantly. 

How can Farmers assist with healthy Soil Carbon Cycling?

Energy + carbon input (adequate energy input + adequate carbon input from organic matter) will positively impact the soil carbon cycle and soil resilience.

The reduction of unnecessary tillage also has a major impact on reducing the loss of microbial habitats. Excessive soil disturbance can break up fungal networks, break down soil aggregates and break up stored organic carbon. Conservation tillage leaves the soil in a better condition for biological activity, beneficial soil organisms and improved soil structure.

Water management is of paramount importance, too. Adequate soil moisture levels will help to ensure good soil microbial activity and prevent extended periods of waterlogging or drought conditions that may affect decomposition. Good structured, well-fertilised soils have excellent moisture control naturally, and are able to support microbial communities during the growing season.

The diversity of these crops contributes to biological activity too. Crop rotation and use of cover crops will bring more variety of root exudates and organic residues, which will foster more variety of microbes. More microbial diversity generally leads to better nutrient cycling, disease control and environmental stress resistance.

As the global carbon cycle is becoming more understood, soils also need to be considered as living, biological systems and properly managed. The adoption of farming systems that promote microbial diversity and maintain soil structure while sequestering carbon will help agricultural production as well as sustainability.

Soil microbes and climate change are being studied and knowledge is growing, making it apparent that sustainable soil production is a major window of opportunity to sustain agricultural production. By utilizing sound agronomic practice and innovative biological soil amendments like Novobac Soil Vigor, growers can contribute to the natural functioning of soils, contribute to the increase of soil fertility, build resilience within the soil and provide productive soil for future generations.

Reference:

• Gougoulias, Christos, Joanna M. Clark, and Liz J. Shaw. "The role of soil microbes in the global carbon cycle: tracking the below‐ground microbial processing of plant‐derived carbon for manipulating carbon dynamics in agricultural systems." Journal of the Science of Food and Agriculture 94.12 (2014): 2362-2371.
• Bertini, Simone Cristina Braga, and Lucas Carvalho Basilio Azevedo. "Soil microbe contributions in the regulation of the global carbon cycle." Microbiome under changing climate. Woodhead Publishing, 2022. 69-84.