Soil Biological Responsiveness

Test for Soil CO2 Respiration reveals Soil Biomass and N-Mineralization Potential

A NEW CATEGORY OF SOIL  TESTING

Solvita is an important new soil test which measures soil microbial respiration  in a modified static-flux system.

Soil respiration represents the biological energy inherent in soil systems. While it has become customary  to ignore soil biology in fertilizer and fertility budgets, this recurring cycle of respiration represents the absorption and release of massive amounts of carbon which is increasingly recognized to be tied to the productivity of  flora and vegetation.

One significant form of this biology are drying and re-hydration cycles in soil which are natural events and which comprise a “biological pump” delivering soluble carbon to microbes and nutrients to growing plants. A result of testing soils with this method is to reveal the soil’s underlying biological (and sustainable) yield component.

By accurately measuring the magnitude of the CO2 pulse, the Solvita test infers microbial biomass and nutrient delivery potential. By factoring this information into nutrient budgets, it is possible to both reduce chemical inputs and to improve yield  sustainability – hence improve net economic yield.

The Solvita test is furnished with an interpretation guide that enables conversion of readings to useful units and provides insight into soil carbon management. With the newly developed digital colorimeter (DCR) it is possible to directly read ppm CO2-C a  quantify which has been successfully correlated with potential N+P release.

The Basic SOLVITA® Soil Response Color System

The patented gel-technology system indicates CO2-respiration over the range of 5 to 100 ppm CO2-C (about 9 to 65lbs CO2-C / acre / day).

With the new Solvita DCR (Digital Color Reader), soil test values can be as precisely determined as conventional laboratory CO2-base trap titrimetry or IRGA, without the cost and fussy chemistry of these techniques.

Two procedures to evaluate soil respiration are available:

1. GROWER TEST: Measurement of a volume of as-is (field moist) soil and reading the results visually by the colorimetric color chart; the result provides an good estimate of soil quality and the supply of available carbon. ORDER AS REGULAR SOIL TEST (uses lower cost polystyrene incubator jars).
2. HANEY-BRINTON TEST: The Woods End-USDA quantitative protocol uses pre-dried, weighed soil which is re moistened and immediately measured for 24-hr CO2 burst. The hand-held Solvita spectrophotometer (DCR) is required. The result provides a ppm reading of CO2 release and represents a close approximation of soil microbial biomass. It directly correlates to mineralized nitrogen and phosphorus. The methods of calculation are provided with the procedure. ORDER AS HANEY-BRINTON TEST (Uses glass incubation jars)

HISTORY OF VALIDATION STUDIES

PIONEER PHASE:  The Solvita soil test has had a long, venerable research and development history. Dr. John Doran’s USDA-ARS soil quality lab at University of Nebraska first worked with Woods End to evaluate field use of the Solvita test kit. It was found  suitable to substitute for Dräger tubes and  gas chromatography. Based on this, the USDA Soil Quality Institute listed the Solvita kit as an alternate procedure in its national soil-quality test kit program (see reprints below).

NEW SOIL TEST: A significant breakthrough occurred resulting in a new soil test protocol following the collaboration with Dr. Rick Haney’s USDA-ARS lab in Texas. In a 4 year research process careful measurements were made of soil drying and remoistening protocol, field soil-carbon turnover compared to actual 28-day N + P release, and calibration with a variety of instrumentation for quantitative calculations (see published papers, below).

Sequence of Typical Soil Solvita Test Results:

Video of Solvita Test Process

Published Papers