Assessing the suitability of using rotary coring for sampling in rocky soils

Abstract

Forest soils are difficult to sample quantitatively because of obstruction by rocks and coarse roots. Collecting quantitative soil cores with a motorized diamond-tipped cylindrical bit can provide much faster access to deep soil samples than digging quantitative soil pits. However, the grinding of rock and soil during coring could elevate exchangeable cation concentrations relative to samples collected manually. We compared soils collected by rotary coring to those collected from quantitative pits at four sites in the United States with differing soil types: Alfisols in California (CA), Mollisols in Nevada (NV), Inceptisols in New York (NY), and Spodosols in New Hampshire (NH). Estimates of soil mass were 34% higher from cores than pits at the NY site (p < 0.0001). Estimates of rock mass were lower in cores than pits by 60% at the NH site (p < 0.0001), by 36% at the NY site (p < 0.0001), and by 55% at the CA site (p = 0.002). Exchangeable K was significantly elevated in cores relative to pits at all four sites by 32 to 1700%, and Ca, Mg, and Na showed elevated concentrations at one or more sites. We tested whether the inner portion of the core was comparable to samples from pits, but found that the rotary action of the corer mixed soils throughout the core bit at the two sites we tested. Coring does have the advantage that more samples can be collected for the same effort, compared to pits. Some degree of inaccuracy might be acceptable in a tradeoff for greater precision in the site-level mean, for example in studies aimed at detecting change in soil nutrients over time.

Department

Earth Systems Research Center

Publication Date

9-2012

Journal Title

Soil Science Society of America Journal

Publisher

ACSESS-Alliance of Crop, Soil, and Environmental Science Societies

Digital Object Identifier (DOI)

10.2136/sssaj2011.0425

Document Type

Article

Rights

Copyright ©2012 by the Soil Science Society of America, Inc.

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