Shade 
A reduction in the amount of light reaching a plant. Less shade produces less energy available for photosynthesis and growth; this results in turf that is less dense, with thinner leaves, weaker root development and a more easily worn surface.
Shear Strength
The ability of a material, such as a soil or grass surface, to resist tearing. It is used to measure the ability of a surface to hold together and to identify at what point it fails.
Size Grade Number
The diameter (given as millimetres x 100), of the median of the fertiliser granules of an analysed batch of fertiliser. Where a size grade number (which is frequently referred to by its acronym of SGN) of 250 is quoted, this means that 50% of the sample will be greater than 2.5mm and 50% below 2.5mm diameter.
Slow Re-growth
A characteristic which is used to evaluate the relative slow speed of growth of a turfgrass cultivar. A cultivar and sward which has a slow regrowth rate will require less frequent mowing, being more suited to low maintenance areas and surfaces where budgets are limited or where usage on a sports pitch is not excessively high.
Sod
An alternative and within the UK an old-fashioned term for turf.
Sodium Adsorption Ratio
A measure of the concentration of sodium and its relationship with calcium and magnesium in irrigation, especially extracted from bore holes or from recycled water, or soil water to determine soil or water salinity. The SAR value is the ratio of the amount of sodium (measured in meq/L) divided by the square root of one-half of the amount of calcium and magnesium.
SAR=〖Na〗^+/√((〖Ca〗^(+2)+ 〖Mg〗^(+2))/2)
The hazard presented from the water will depend not just on the SAR value but also the value of the electrical conductivity of the water.
Soil Balance Sheet
A tabulated data sheet with numerous columns for data recording to help estimate water requirements of a plant. The table will typically include columns for Potential Evapo-transpiration; Estimated actual Evapo-transpiration; Rainfall; Irrigation; Drainage; Soil Moisture or Water Deficit. A similar Soil Balance Sheet can also be devised and used for nutrient requirements; especially Nitrogen, Phosphorus and Potassium.
Soil Ecology
The diversity and interactions of soil organisms and the effect they have on plant growth and development and conditions, for example soil structure and drainage potential, of the soil profile.
Soil Ecosystem
A range of interconnected components within a soil which creates a living system Micro-organisms, plant roots, soil minerals, water, temperature, air and nutrients are all essential components of a soil ecosystem.
Soil Fauna