1. Glossary, Symbols and conversion formulae associated with salt affected soils

2. Conductivity: SI unit is Seimens(S).Equivalent non SI unit is ‘mho’ and 1mho=1Seimens and mho/cm can be read as S/m The standard unit for conductivity (mho/cm) is a large unit and most solutions have the conductivity much less than one unit. Hence it is expressed as m mhos/cm i.e., EC×10 3 EC×10 3 : Conductivity 1S cm -1 (1mho/cm) = 1000 mS/cm (1000mmhos/cm) 1 mS/cm -1 (1 mmho/cm) = 1 dS/m = 1000 mS/cm (1000 micromhos/cm) EC×10 6 : Electrical Conductivity in micro mhos value in mhos/cm×10 6 or dsm -1 ×10 6

3. Conductivity to milli-equivalents per litre meq/l = 10×EC(EC in dS/m) for water and soil extract in the range from 0.1 to 5.0 m mhos/cm Milliequivalents per litre to ppm Multiply meq/l by equivalent of each ion mmol/l (chemical analysis) to mg/l: Multiply mmol/l for each ion by its molar weight and obtain the sum Conductivity to osmotic pressure in bars: OP = 0.36 × EC (EC in dS/m) for soil extracts in the range of 3 t0 30 m mhos/cm

4. Conductivity to mg/l: mg/l = 0.64 × EC x 10 3, or (EC in dS/m) =ppm µg/l = 640 × EC for waters and soil extracts having conductivity up to 5 dS/m. ECe : Electrical Conductivity of saturation extract EC W : Electrical Conductivity of water EC 1,EC 5,EC 50 : Electrical Conductivity of extract of soil, water ratio of 1,5 and 50.

5. The relation between the salt concentration of the extract of a saturated paste (ECe) and the salt concentration of the soil moisture at field capacity is about 1:2 The extract of a saturated paste needs centrifuging, whereas the measurement in the 1:2 suspension can be done directly. In general one finds: ECe = 4 to 5 EC1:2 (see figure).

6. Glossary: Absorption: The process by which a substance is taken into and included within another substance Adsorption: The process of holding ions/molecules at the surface. Alkali Soils: A soil that contains sufficient exchangeable sodium to interfere with plant growth either with or without appreciable quantities of soluble salts. Cat-ion exchange capacity : The total quantity of cations which a soil can adsorb by cation exchange usually expressed as meq/100g

7. Exchangeable sodium percentage : The degree of saturation of the soil exchange complex with sodium ESP = Exchangeable Na(m eq/100g soil) × 100 Cation exchange capacity(m eq/100g soil) Residual Sodium Carbonates (RSC meq/l) = (CO 3 -2 +HCO 3 -1 ) –(Ca +2 +Mg +2 )

8. Potassium Adsorption Ratio (PAR) : A ratio for soil extracts used to express the relative activity of potassium ions in exchange of the reaction with soil PAR = K + similarly √(ca ++ + Mg ++ )/2 Sodium Adsorption Ratio(SAR) : SAR = Na+ √(ca 2+ + Mg 2+ )/2 Soluble Sodium Percentage (SSP): Indicates the percent of sodium ions in solution in relation to the total cations concentration SSP = Soluble Sodium Concentration (meq/l) × 100 Total cation concentration (meq/l)

9. Saturation extract: The solution extracted from a soil at its saturation percentage Specific ion effect: An effect of a salt constituent in the substrate on plant growth that is not caused by the osmatic properties of the substrate. Milli equivalent: One thousandth of an equivalent Milli equivalent per litre: A milli equivalent of an ion or a compound in 1litre of solution. Saturated soil paste: A particular mixture of soil and water where soil gets saturated and appears glistens as it reflects light, flows slightly