Glossary - Afforestation, Reforestation and Forest Restoration in Arid and Semi-arid Tropics - page 275

Social fencing The concept of general agreement among the users of a tract of land
to keep their animals off the land, thus producing the same effect as if the land had
been fenced.

Sodium absorption ratio A measure of suitability of water for irrigation, deter-
mined by the concentrations of solids dissolved in the water. It is also a measure of
the sodicity of soil, as determined from analysis of water extracted from the soil.
In general, the higher the sodium adsorption ratio, the less suitable the water is for
irrigation. Irrigation using water with high sodium adsorption ratio may require soil
amendments to prevent long-term damage to the soil.

Soil amendment Addition of chemical substances, such as gypsum, to soil in order
to control a particular characteristic of the soil, such as high salinity.

Soil binders Class of shrubs, trees, and perennial grasses that develop a bushy thick
root system and hold soil together effectively. These are planted where soil erosion
is to be controlled.

Soil hardness classes Division of soil into categories based on its hardness to work-
ing or excavation. Harder soils require more effort to excavate and thus lead to higher
costs.

Soil replacement Removal of a particularly problematic soil from its place and
replacing it with better and fertile soil brought from some other place.

Spot irrigation Irrigation by delivering water from point to point. It results in
economic use of water, though labour costs may be higher.

Sprinkler irrigation Irrigation by means of water dispensed through minute holes
in pipes or through nozzles that spray water in form of fine drops. This method is far
more economical compared to the traditional method of flow irrigation, though by
no means as efficient as drip irrigation.

Stadia In tachymetric theodolite, the parallel horizontal hairlines that read the
intercept on a vertical graduated staff to measure distances telescopically.

Stadia tacheometry Method of surveying in which distances are measure telescop-
ically by observing the stadia readings on a graduated staff.

Stand-out bed ⇒ Bed

stem cuttings ⇒ Cuttings

Stonewall fence A fence made by constructing a wall of stones available on ground
surface. It is usually constructed in dry masonry, but can have concrete coping on
top to give it stability.

Stream discharge Rate of flow of water in a stream at a given point of time. Maxi-
mum likely stream discharge, or the peak discharge, is required to be estimated while
designing a stopdam or a weir on a stream. Various empirical formulae have been