contributed by Karen Colson and Jason Karl

Soil Properties - Quantitative

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The impacts of soil compaction, such as reduced water infiltration, increased runoff potential, limited root growth and microorganism activity, and ultimately reduced site potential, are well known. But reliable methods to measure compaction are limited. There are three commonly used techniques for assessing soil compaction: strain gauge penetrometer, impact penetrometer and bulk density.

An impact penetrometer is one method that can be used to help determine whether or not a soil is currently compacted. This method however requires reference data for similar soils with the same moisture content for comparison. In general, soil compaction is determined by the work needed to push a penetrometer cone into the soil with successive blows. See Herrick et al. 2002 for a more detailed description of this technique and information on constructing a penetrometer.

Cost, measurement reliability, and difficulty in comparing data can all be concerns when using penetrometers. Penetrometer measurements, for example, are very sensitive to soil moisture and measurements can only be compared among years if soil moisture content is the same during each sampling period. In addition, the repeatability of the measurements depends on the consistency of the height from which the mass is dropped.

• Monitoring Manual for Grasslands, Shrublands, and Savanna Ecosystems (Herrick et al. 2005) http://usda-ars.nmsu.edu/Monit_Assess/monitoring_main.php.

• Herrick, J.E. and T.L. Jones. 2002. A dynamic cone penetrometer for measuring soil penetration resistance. Soil Science Society of America Journal 66: 1320-1324. http://usda-ars.nmsu.edu/Monit_Assess/PDF_files/HerrickJones2002Penetrometer.pdf
• Pellant, M., P. Shaver, D.A. Pyke, and J.E. Herrick. 2000. Interpreting indicators of rangeland health, version 3. Technical Reference 1734-6. USDI, BLM, National Sci. and Tech. Center, Denver, Colo. 21-Mar-02. ftp://ftp.ftw.nrcs.usda.gov/pub/glti/IntIndRangeHealth.pdf

Qualitative methods (Pellant et al. 2000) are also useful for determining if soil is compacted. Some indicators, not related to a texture change, include platy soil structure and abrupt changes in root growth patterns.

Other methods that measure soil properties include Soil Infiltration and Soil Stability Method.

• Jornada Experimental Range Monitoring and Assessment Site

• Soil compaction data can be recorded directly into the The Database for Inventory, Monitoring and Assessment in the field.
• An Excel version of the soil compaction method data form that automatically calculates cover percentages can be found at the Jornada Experimental Range Monitoring and Assessment Site.
• An version of the soil compaction Excel form that is compatible with electronic PDAs can also be downloaded from the Jornada Experimental Range Monitoring and Assessment Site

Soil stability kits and impact penetrometers can be purchased from the following vendors:

1. Synergy Resource Solutions, Jack Alexander
   jack@countgrass.com
   http://www.countgrass.com
   Synergy Resource Solutions, Inc.
   1755 Hymer Ave.
   Sparks, NV 89431
   (775)-331-5577 Office
   (775)-331-5579 Fax
   (775)-772-5123 Cell

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