Solvita Rehydration CO2-Burst Test: A DIAGNOSTIC TOOL for ACTIVE SOIL CARBON, SOIL Microbial BIOMASS and for ESTIMATING POTENTIAL N-MINERALIZATION.

Taking account of a soil’s natural nutrient supply potential (especially for N and P) could become more standardized and commercialized by development of a reliable and rapid method to quantify soil biological responsiveness. Flush of CO2 following drying and rewetting mimics some natural processes. The CO2 burst from rehydration has been observed to correlate with N-supply potential which in some explained 97% of the variability in cumulative C mineralization over several weeks. However, laboratory respirometry methods have not attracted serious attention by commercial soil labs due to the high cost of required labor and the specifics of reagent handling. At the same time groundwater and surface water nutrient levels are of increasing concern, partly related to over-supply of nutrients. The recent introduction of a quick-test- “Solvita®” to capture 24-hr CO2 burst and a rapid-rewetting procedure to simplify laboratory processing of soils measn soil test labs will have access to a procedure to evaluate this factor. Initial laboratory trials (2009-2010) at Rutgers University soil lab and the University of Maine soil lab have indicated promising correlations of the Solvita test with other methods including WB-carbon (active carbon), N-mineralization (28-day extraction and 7-day anaerobic incubation) and N-uptake infield plot studies (Temple Experiment Station, TX and UMO field plot study, Highmoor Farm ME) and ISNT trials (preliminary results: Holyoke College, Cornell Univ.). The potential usefulness of a reliable test in evaluating contributions to soil biological activity of soil amendment practices is in the process of being evaluated by 12 soil laboratories across America. Such a test if used by more soil labs and soil consultants could aid more accurate fertilizer rates and more improve understanding of the role of soil biological activity in fertility management procedures.