Living soils are healthy soils

An increasingly popular method to determine the health of soil examines the CO2 respired by microorganisms in the ground. The Solvita® test is a cost effective method to better understand the level of life and activity in the field.

Soil health is an increasingly popular topic in modern agriculture. Although it has long been agreed that organic matter is a critical component to the soil health equation, the role of carbon is less understood. Respiration of carbon; released as CO2 in the soil from plants, bacteria, fungi and animals, is absorbed in soil through the humification (building humus) process. Declining humus and lowered rates of respired CO2 strongly relate to the lack of food for soil microbes. This condition is often found in degraded agricultural systems where management practices do not support soil life. Improved management, potentially through the use of reduced tillage and cover cropping will support this key ecosystem process that is being well-accepted as an indicator of healthy soil. 

The Solvita® test is a fairly new, cost-effective method to examine soil respiration in the field. A field-moist sample is placed in a sampling jar along with a Solvita® probe that includes a color-changing gel. The lid is placed back on the jar and screwed tight to minimize any respiration leakage. After 24 hours the color on the probe is matched with the Solvita® color chart, and the rate of respiration is determined. A digital color reader is also available and will provide the most accurate reading of the probes. The number from the probe (0-5) can be entered into the online calculator to determine the amount of CO2-C respired (ppm) and the amount of carbon sequestered (lbs/acre2) over the 24 hour period. The calculator will also provide you an explanation of whether or not your level is indicating a healthy, living soil. 

Putting Solvita® to practice

In the summer of 2014, the Michigan State University Upper Peninsula Research and Extension Center evaluated cover crops in a replicated trial that included eight different cover crop species (Annual Rye, Buckwheat, Chickling vetch, Cowpeas, Ethiopian cabbage, Egyptian wheat, Collards and Sunn hemp), along with a diverse blend of those eight species. The objectives were to evaluate species suitability for the U.P. and potential species differences in soil respiration. The nine treatments were laid out in a randomized complete block design with four replications. In order to simulate a low-input farming system, no herbicide or fertilizer was applied to the plots. On September 24, 2014, soil respiration was measured on each plot. Visual assessments were taken on relative level of vegetation and ability to suppress weeds. On September 25, 24 hours after the samples were collected, the respiration rates were determined. 

The Solvita® test was an efficient way to analyze soil respiration in the cover crop trial and was able to show significant differences between some of the treatments. Annual Rye on average had the highest CO2-C respiration reading, and was statistically significantly higher than Egyptian wheat, the diverse mix, Ethiopian cabbage, Collards, Cowpeas and Buckwheat. Success and results from this study, however, should be interpreted based on your goals for cover crop use. For example, Buckwheat, which produced a healthy stand and did the best at weed suppression, actually had the lowest average CO2-C respiration recorded. This may be due to the fact that the canopy from the plant shielded out any understory growth. This would explain why the higher yielding, weedy stands of other cover crop species (cover crop + weeds), actually had higher respiration rates, for example Sunn Hemp. As overall soil health interest increases, methodologies of identifying reliable soil indicators are increasing. The Solvita® test is one method that allows farmers to rapidly assess soil respiration and metabolism in the field.

If you would like to learn more about soil respiration or the cover crop trial, feel free to contact me at or 906-439-5176. I am the coordinator at the MSU Upper Peninsula Research and Extension Center and an Extension Educator with Michigan State Universtiy Extension.  

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