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

Another name for Soil Organisms.

  Soil Organic Matter: Factors Influencing Rates of Decomposition

There are a range of factors that can influence the rate at decomposition of organic matter, and many of these also influence the effect of the included and other factors. 1. Temperature is a key factor as this influences the activity of the micro-organisms which break down organic matter. Warmer temperatures (35°C compared with 25°C), especially when adequate moisture levels are present, can result in very rapid decomposition occurring. 2. Moisture availability is another key factor, with increasing moisture (up to about 90% water-filled pore space), but not at a waterlogging stage (as no o

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  Species

A similar group of individuals, for example plants which interbreed with each other and produce offspring. Species can only, generally, interbreed with their own species. In limited cases where closely related species interbreed the resultant offspring are called hybrids. The species is, however, the standard unit of classification for identifying plants, or other organisms. For plants to be included within a species individual plants have to possess many characteristics which are the same. However, it is the discontinuity of similarities which distinguish species from each other. Essential

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  Specific Epithet

The second part of a species name which comes after the genus name. For example, rubra is the specific epithet element of the name Festuca rubra.

  Spore

A reproductive cell of numerous organisms, including fungi, bacteria, algae, moss, ferns and conifers.

  Spot Treatment

The selective and specifically targeted treatment of a pesticide to an individual plant (for example, a selective herbicide being applied to a single broad leaved weed) or to a small area of turf which has a very localised condition which needs treating.