Measuring Total Organic Carbon in Soil

Total Organic Carbon (TOC) is a measure of the organic carbon contained within soil. Organic carbon in soil is the result of the decomposition of plant and animal matter, living and dead microorganisms, roots from plants and soil biota. The amount of TOC in soil affects color, nutrient capacity (cation and anion exchange capacity - CEC), nutrient stability and turnover, water relationships, aeration, cultivation and plant growth and health. TOC is the main source of energy for soil microorganisms and is a trigger for nutrient availability though mineralization for plant growth.

Measuring TOC provides information on soil fertility, aggregate stability, and the exchange of CO2 with the atmosphere. All these and other characteristics are important for a range of applications from environmental monitoring to precision agriculture.

VIS/NIR field spectroscopy offers a fast, accurate and affordable alternative to lab analysis of TOC. In addition, measuring TOC with a field spectrometer like the SR-6500, RS-5400, PSR+ or RS-3500 can be done in situ without harming the sample.

These spectroradiometers are  designed for field measurement and analysis. They are rugged and reliable with a range of fiber mount options for use with a handheld contact probe or a benchtop probe with sample tray and soil compactor.

They are full range agricultural spectroradiometers (350-2500nm) with the highest available resolution and sensitivity in field instruments. In a typical soil sample, TOC features would appear at 1100,1600,1700-1800, 2000 and 2200-2400nm. There may also be other materials present, for example hydrocarbons with similar absorption features at 1180, 1380, 1680-1720 and 2300-2400nm.

High resolution allows you to collect accurate scans that can be clearly analyzed for TOC. Auto-shutter, auto-exposure, and auto-dark current capabilities mean no manual optimizations steps between scans. As sealed units, you don't need to worry about dust or dirt getting inside the unit as you work in a soil pit. No moving optical parts means no breakdowns in the field.

The DARWin Data Acquisition software on our spectroradiometers provides access to 19 vegetation indices and the USGS spectral library with its soil and mineral samples. Optional EZ-ID sample identification software is also available with access to the SpecMIN, GeoSPEC and USGS mineral spectral libraries to quickly identify clays and other minerals. The Custom Library Builder module allows you to collect TOC scans and build your own custom libraries.

Field spectroradiometers for soil analysisField spectroradiometers

The SR-6500, RS-5400, PSR+ and RS-3500  are designed for remote sensing applications including measuring total organic carbon in soil. They are easy to use in the field, including collecting scans in a soil pit.

Multiple soil spectra

DARWin SP Data Acquisition software saves all your spectra and metadata as ASCII files for use with a wide range of 3rd party analysis and chemometrics programs, including GRAMS, TSG, Unscrambler and R.