Environmental BioTechnologies, Inc.

Does soil moisture content have an effect on the MET value?

EBT has conducted a series of studies to determine if soil moisture has an effect on the MET score. The data indicates that soil moisture in the range of 10-28% has only a minimal influence on the MET score. However, a soil with a moisture content below 5% demonstrates a significantly reduced MET value. This reduction in the MET value with decreasing soil moisture is shown in the following graph. From this figure it appears that soils with a moisture content below 5%, a factor should be used to adjust the measured MET score accordingly.

In a laboratory study, it was found that as soils dry out, the MET score drops significantly. It was also found that soils stored in paper bags dry out and demonstrate a drop in MET score, whereas soils stored in plastic bags remain moist and maintain the same initial MET value over time, as shown in the following figure. Therefore, EBT collects and stores all soil samples in sealed plastic bags to prevent drying out of the samples.

In conclusion, studies have shown that soil moisture content has a direct affect on the MET value. Therefore, every effort is made to maintain the moisture content of the soil after collection in the field (i.e. the use of plastic sample bags). Soil moisture determinations are done in the laboratory to assure that the sample is not well below 10% moisture. If moisture levels are exceptionally low, as in a desert survey, either the MET value can be adjusted using the linear relationship between moisture and MET value, or EBT takes other technical and statistical approaches to "normalizing" the MET value in a dry region.

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Environmental BioTechnologies, Inc.
255C S. Guild Ave.
Lodi, CA 95240
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