VOELCKER'S TOPSOIL QUALITY STANDARD

Extracted from "A Guide to Specifying Topsoil" Parts 1 and 2 by R.M.Voelcker et al., published in Landscape Design, March and April 1989.

A soil which meets the requirements of the specification would possess the necessary attributes to sustain healthy plant growth in a variety of landscape situations under satisfactory conditions of management.

Major Nutrients etc.

pH	5.5-7.8
Electrical Conductivity 1:2.5 (w/v) extract	<1500 us/cm
Organic Matter	> 4.0% (w/w) (1)
Nitrogen (N)	> 0.2% (w/w) (2)
Extractable Phosphorus (P)	> 45 mg/kg (3)
Extractable Potassium (K)	> 240 mg/kg (3)
Extractable Magnesium (Mg)	> 80 mg/kg (3)

(1) BS 1377, (2) Kjeldahl, (3) MAFF Handbook RB427

Stones

Maximum size in any direction	50mm
Maximum content (2mm-50mm)	35% by dry weight of which the fraction 2mm-5mm must not exceed 20% by dry weight

Soil Texture

 

The diagram above shows the soil texture triangle with lines denoting organic matter superimposed. Soils with the appropriate amounts of organic matter would have cation exchange values of 30+ meq. per 100g, and would possess adequate water-holding and sufficient cation retention properties. The area inside the hexagon (shaded in green) denotes the preferred textural classes for landscaping purposes.

Topsoil must be free from pernicious weeds and roots, clay lumps, non-soil material, brick and other building materials, foreign matter and chemical contamination.

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