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ARS Home » Pacific West Area » Pendleton, Oregon » Columbia Plateau Conservation Research Center » Research » Publications at this Location » Publication #223936


item Wuest, Stewart

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2008
Publication Date: 1/2/2009
Citation: Wuest, S.B. 2009. Correction of bulk density and sampling method biases using soil mass per unit area. Soil Sci. Soc. Am. J. 73:312-316

Interpretive Summary: Interest in quantifying carbon sequestration in soil has created a need for soil sampling methods which give consistent and accurate results over time, locations, soil conditions, and by different researchers. Fluctuations in soil bulk density make this very difficult when using the soil surface as the criteria for determining depth of samples. Equivalent soil mass (mass-depth) can be used instead of linear depth, allowing more precise and accurate quantitative comparisons of soil constituents. We compared mass-depth against the standard linear-depth method and found mass to give much more consistent results. It is also capable of correcting for artifacts due to differences in sampling equipment and sampling conditions. Using mass-depth requires only small changes in sampling protocols, and represents an important advance in our ability to perform accurate assessments of soil constituents.

Technical Abstract: It is becoming increasingly clear that both quantitative and concentration soil constituent comparisons are confounded with soil bulk density if samples are collected based on depth from the surface. Our first experiment made direct comparisons of linear depth and soil mass per unit area for water content determinations of soils which differed only in surface bulk density. A second experiment compared different soil sampling tools. In both experiments analysis by mass instead of depth corrected discrepancies caused by bulk density or sample compaction and resultant depth-of-sampling differences. In a third experiment, soil samples collected from an on-farm test resulted in different relationships between summer fallow tillage practices depending on whether the soil water content (or concentration) was analyzed using depth or mass. Sampling by mass per unit area instead of depth is more accurate and precise than many quantitative methods currently in use, and represents an important advance in our ability to make comparative measurements over time, treatments, locations, and equipment.