CO2-Burst Method – Standard Lab Protocol
Solvita CO2-Burst provides the means for commercial laboratories handling dried soils to measure CO2 respiration. The output of CO2 from soils due to microbial activity is a fundamental biological trait of living soil, and CO2-burst following re-wetting is a specific trait. Overall, without microbial CO2 respiration, no litter would decompose and no organic compounds would be recycled back to available nutrients, a process called mineralization. Measuring soil CO2 respiration also provides a key estimate for sequestration vs loss in planetary atmospheric CO2 concentrations.
How does it work?
Dried, weighed samples of soil are moistened with a specific amount of water, triggering a flush or “burst” of carbon dioxide. The magnitude of the burst is measured with the Solvita Digital Color Reader. CO2-Burst is proportional to microbial biomass and directly tied to potential carbon and nitrogen mineralization. SOP available here.
Why measure CO2 respiration?
- CO2 respiration is an indicator of soil health – The rate and quantity of CO2 release over a specific period is generally regarded as an accurate indicator of biological attributes favoring healthy soil functioning. The “turnover rate” of CO2 from soil rises with improved management practices. Such practices include cover cropping, reduced tillage and organic amendments which assist to build soil residual organic matter and plant litter, the food base of soil microbes and invertebrates.
- CO2 respiration is an indicator of potential nutrients – Measuring the rate of carbon exchange via soil respiration is indirectly linked to nutrient “mineralization” – the potential release of nutrients such as nitrogen and phosphorus that are components of plant residues, microbes and humus.
How soil and plants interact
Soil and plants interact in the search for and supply of nutrients. Soil provides the environment for plant growth while plants participate in building and sustaining soils by releasing exudates during life and leaving residues behind for bacterial food. This dynamic cycle is best described as the soil-plant-biology system. In the process, “humus” is formed and carbon dioxide (CO2) is released due to microbial activity. The relationship between these processes is the bedrock of lasting soil fertility. Declining rates of CO2 respiration are associated with intensive tilling, compaction and over fertilizing. Soil practices which are destructive act to inhibit the soil’s ability to sustain its humus content, the natural reservoir of organic nutrients and soil life. As soil quality declines, microbes food supply diminishes and the rate of CO2 respiration declines. Therefore, being able to evaluate the turnover of organic matter via CO2 respiration is important for a number of reasons.
Why is CO2 respiration important?
Soil CO2 respiration has been known to be an indicator of soil quality since as early as the 1920’s. Research in Europe after the 50’s helped standardize lab analytical procedures even before practical application was understood. By the 1970’s soil respiration tests were seen as useful indices to compare results of differing soil management strategies. Unfortunately, it was not until more recently that CO2 respiration was more broadly recognized to be a crucial trait linking microbial activity to healthy soil,- a complete cycle based on overall soil biota. No other test can claim this universality. All this combines into into a huge potential impact for measuring and addressing the implications of soil CO2 turnover. In the not-too-distant future soil respiration results will provide a useful key to leveraging natural fertility to save significantly on nitrogen fertilizer dollars and help bolster farming’s environmental commitment.