Co-Author: Vinayak Shedekar, Postdoctoral Researcher OSU
A measurement for determining soil health is the release of carbon dioxide (CO2) from the soil. Carbon dioxide emissions from soil are primarily due to microbial respiration. The level of microbial activity is indicative of the amount of active organic matter that is being broken down and nutrients being released. Some professional labs measure the CO2 release in controlled environments over a 7 to 12 day incubation period. It is possible to conduct similar assessment using Solvita ® - a patented measurement system, which uses a gel probe impregnated with chemistry that is sensitive to specific gas molecules and changes color in proportion to their concentration. The colors of the gel are visually compared to a color chart for interpretation. The color chart is divided into graduated color codes from 0 to 5. Each increment on color palette indicates doubling of soil respiration.
Figure 2: Solvita paddle color chart. After 24 hours, compare color change to data table.
The Solvita Field CO² respiration test is designed for testing fresh, undisturbed soil not processed in a lab. A 3- inch tube of soil (use a bulb planter) is sealed intact in the sample jar with the gel probe. After 24 hours, the color of the gel probe is compared to the color chart to make interpretations. A digital color reader is also available through Sovita® to get a more accurate estimate of CO2 respiration.
Another respiration test is the CO 2 burst method. This is performed in a commercial lab where samples are shipped to the lab, then dried and sieved. Soil is rewetted with a specific amount of water, which causes a burst of carbon dioxide. This measures the soil microbe respiration potential under disturbed conditions. The burst method is usually 2 – 4 times higher than the field respiration method. The measurement is collected with analytical lab equipment.
Caution should be used when interpreting the amount of nitrogen release estimated from respiration. A grass sod may have high microbe respiration but low available nitrogen. A soil nitrate test could accompany the Solvita test to gain confidence in available soil nitrogen.
For more information: https://solvita.com/