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Arboriculture & Urban Forestry Online
Volume 8, Issue 4 — April 1982

A Composite Sampling Technique to Assess Urban Soils Under Roadside Trees    (View PDF)

G.A. Ruark, D.L. Mader and Terry A. Tattar

Abstract: Soils underlying roadside sugar maple {Acer saccharum Marsh.) trees in an urban setting were studied to determine the relative advantages of a ten-point composite sampling scheme over the more common practice of averaging analytical results from a few individual samples. The soil samples near the crown periphery were systematically extracted using a hammer-driven tube sampler and composited using equal volumes from each point. Mineral soils were partitioned into 0-15 and 15-30 cm depth components. Duplicate composite samples were obtained for each of 12 trees. Four individual soil samples also were extracted with a larger tube sampler from the same region and depths. Coefficients of variation and numbers of samples needed to estimate the mean within ten percent at the .05 probability level were computed for various chemical and physical measurements. The ten-point composite method consistently displayed a pronounced reduction in variation of analytical results and provides a considerable savings of laboratory time. Specifications for sampler design and utilization are described.


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