Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 8/17/1999
Publication Date: 1/4/2001
Citation: Cambardella, C.A., Gajda, A.M., Doran, J.W., Wienhold, B.J., Kettler, T.A. 2001. Estimation of particulate and total organic matter by weight loss-on-ignition. In: Lal, R., J.M. Kimble, R.J. Follett, and B.A. Stewart, editors. Assessment Methods for Soil Carbon. Boca Raton, FL. Lewis Publishers/CRC Press. P. 349-359. Interpretive Summary: Interest in the evaluation of soil quality has been stimulated by an increasing awareness that soil is an important natural resource. Soil is a dynamic, living body that functions to produce food and fiber and help maintain environmental quality. Much like air or water, the quality of soil affects the health and productivity of the environments related to it. However, unlike air or water, soil quality is difficult to define and quantify. Soil organic matter (SOM) is considered to be one of the most important components of soil quality. The more active forms of SOM respond more quickly to changes in management practices and, as such, are better than others for evaluations of soil quality. Laboratory methods for quantification of SOM generally involve the use of expensive analytical instruments that require trained technicians to operate and maintain. Our objective was to develop and test the weight-loss-on- ignition (WLOI) method for SOM and a form of active SOM called particulate organic matter (POM), as an alternative to the more costly and technically sophisticated analytical methods. Relative comparisons of POM and SOM by WLOI for one field at several points in time or between one or more fields at one point in time appears to be feasible based on our data. Researchers, land managers, or producers wishing to use POM or SOM for soil quality estimates where sophisticated analytical technology is not readily available will derive the greatest benefit from this research.
Technical Abstract: Soil organic matter (SOM) is considered one of the most important components of soil quality. Although total SOM may take many decades to respond to change, active SOM fractions are hypothesized to respond relatively quickly to changes in climate, land-use, and management. A number of studies suggest that one form of active SOM, particulate organic matter (POM), is especially responsive and the concept of using POM as an indicator of soil quality has been widely adopted in the past 10 years. The method for isolating POM from soil is simple but quantification of POM C is generally done using automated dry combustion technology. The automated methods require a large capital investment and extensive technical expertise to run and maintain the instruments. Our objective was to develop and test the weight-loss-on-ignition (WLOI) method for POM and SOM as an alternative to the more costly and technically sophisticated dry combustion methods. We utilized two USDA- NRCS benchmark soils of contrasting textures to calibrate the WLOI method and surface soil samples from 5 field sites in the central and northern Great Plains to verify that POM assessed by WLOI is a sensitive soil quality indicator. Relative comparisons of POM and SOM by WLOI for one field at several points in time or between one or more fields at one point in time appears to be feasible based on our data. Researchers, land managers, or producers wishing to use POM and SOM for soil quality estimates where dry combustion technology is not readily available will derive the greatest benefit from the research.