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 PSR+ can be done in situ without harming the sample.

The PSR+ is a spectroradiometer designed for field measurement and analysis. It’s rugged and reliable with a range of direct attach FOV lenses as well as fiber mount options for use with a handheld contact probe or a benchtop probe with sample tray and soil compactor.

The PSR+ is a full range agricultural spectroradiometer (350-2500nm) with the highest available resolution and sensitivity in a field instrument. In a typical soils sample, TOC features would appear at 1100,1600,1700-1800, 2000 and 2200-2400nm. There may also be other materials present, fo example hydrocarbons with similar absorption features at 1180, 1380, 1680-1720 and 2300-2400nm.

The PSR+ 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 a sealed unit, 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 the PSR+ 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 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.

The PSR+ is a field portable spectroradiometer for remote sensing applications including measuring total organic carbon in soil. It is easy to use in the field, including collecting scans in a soil pit.

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.