How to Interpret your Soil Life (CO2 burst) Test

How to interpret your soil life (CO2 burst) Test

CO2 Burst Method 

The CO2 burst method provides the means for a laboratory to realistically measure CO2 respiration. Carbon dioxide output is a fundamental biological trait within soil systems. It is also a primary indicator of carbon cycling. Without CO2 respiration no soil organic matter would be decomposed and recycled back to available nutrients, a process called mineralisation. In fact soil CO2 respiration is a principal controlling force in planetary atmospheric CO2 concentrations.

How does it work? 

Dried weighed samples of soil are wet with a specific amount of water, triggering a burst of carbon dioxide. The carbon dioxide is measured over a 24 hour period. The CO2 burst is proportional to the microbial biomass and is directly tied to potential carbon and nitrogen mineralisation.

Why measure CO2 respiration? 

  1. CO2 respiration is an indicator of soil health. The rate and quantity of CO2 release is regarded as an accurate indicator of biological attributes favouring soil health. The CO2 burst increases with improved management practices such as cover cropping, reduced tillage, manure, plant litter or compost addition that help build the organic matter content. This, combined with balanced soil nutrients forms the food base for the soil microbes and invertebrates that are important for nutrient recycling and crumb structure. 
  2. CO2 respiration is an indicator of potential nutrients , soil respiration is indirectly linked to the rate at which mineralisation of the organic matter can occur, and therefore the rate at which the minerals that are in the organic matter can be made available to the plants.

How soil and plants interact 

Soil and plants interact in the search for and the supply of nutrients. Soil provides an environment and foundation for plant growth, while plants build and sustain soils by releasing plant exudes and leaving crop residues. This dynamic cycle is described as a soil- plant-biology system. In the process humus is formed and carbon dioxide is released due to microbial activity. This process is the bedrock of lasting soil fertility. Declining rates of CO2 respiration are associated with intensive tilling, compaction, over fertilisation, pesticide damage and water-logging. Destructive soil practices inhibit the soils ability to sustain its humus content. As soil quality declines, the humus content reduces and the microbes food supply diminishes and so the CO2 respiration rate of the soil declines. Therefore being able to determine the potential ability of the soil to turnover its organic matter is important.

Soil CO2 respiration was known to be an indicator or soil quality as early as the 1920s. Research in Europe in the 1950s helped standardize laboratory analytical procedures. In the 1970s soil respiration tests were seen as useful indices to compare results of differing soil management strategies. More recently soil CO2 respiration is recognized as a crucial trait linking biological activity to healthy soil.

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