One of the functions of the BTSA is to prevent this material finding its way into the marketplace
and the electrical conductivity. Nutrient levels such as Magnesium (Mg), Potassium (K) Phosphorous (P) and Nitrogen (N) should also be shown on the specification sheet. The PSD will give an indication of the silt and clay content. The effects of high concentrations of the finest particles in a soil will affect the drainage and gas permeability of the
growing medium. Heavy clay soils will be slippery when wet and will be slow draining. When these soils dry out in hot summer conditions, which are becoming more prevalent with global climate change, they set rock hard, which is both unsuitable for most sports playing surfaces (with the obvious exceptions of cricket wickets and tennis courts) and
Typical specification sheet
use of inferior materials to economise on manufacturing costs. This frequently applies to the soil blended into these products. Soil of doubtful provenance can often be derived from root vegetable washing, as a by-product of the food production industry. Companies that hire skips can often sell topsoil as a sideline; the contents of the filled skips are passed through a screener, the result being sold as ‘topsoil’. Silt from river dredging has been discovered being sold as topsoil. All these products are usually high in silt and clay, in the case of vegetable washings there is often a high salt content. Soil that has been lifted from brown field/ex-industrial sites is being offered as premium grade topsoil. The lead photograph of this article is an actual case of this. One of the functions of organisations such as the British Topsoil Suppliers Association (BTSA) or BRTMA is to prevent this material finding its way into the market place. Poor quality topsoil substitutes can possess high levels of salts as measured by the soil’s Electrical Conductivity, the units being mS cm-1. Genuine topsoil will usually give a reading in the range of 250 - 800 mS cm-1. Vegetable washings sold as topsoil have been measured in excess of 2700 mS cm-1. Partly this is because lime is used in the cultivation process. What are the effects of high salt concentration on plant health? One of the main effects is that high salinity interferes with Ion exchange by raising the osmotic potential. This has the effect of hindering the plant’s ability to absorb nutrients in the form of dissolved mineral ions via the root system. In the case of turf this will produce weaker turfgrass with a greater susceptibility to disease.
A specification sheet provided by the supplier should show the Particle Size Distribution (PSD), the pH, the percentage content of organic matter
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