Total soluble salts are usually measured by the electrical conductivity of the water and are quoted as millisiemens per metre (mS/m). Multiply the conductivity (in mS/m) by 5.5 to convert approximately to milligrams per litre (mg/L) or parts per million (ppm).
The suitability of water for reticulation and home gardens is influenced not only by the total soluble salts and their composition, but also by the type of soil and its drainage, the climate and the rainfall. Salts accumulating in the soil from the reticulated water can cause a salt problem.
Using saline water
Seedlings are more sensitive to salt than mature plants. In salty situations it may help to grow seedlings in poting mix in containers that break down when the plants are placed in their permanent positions. Saline water can be used more successfully on a well-drained light soil than on a poorly-drained heavy soil. Plants have more tolerance to salty water in districts where high seasonal rainfall leaches the salts accumulated in the soil.
Trickle systems can reduce the effects of salinity by maintaining a continuously moist soil around the plant roots and providing steady leaching of salt to the edge of the wetted zone. If saline water is used for sprinkler systems, it is important to reduce evaporation.
Improve soil structure by applying gypsum to heavy soils that have been shown to become more friable with gypsum and add big quantities of organic matter to all soils.
Water at night, early in the morning, or late evening when the air is more humid. Watering in the heat of the day or during high winds concentrates the salts due to the high evaporation. Do not use sprinklers that produce fine droplets and if possible avoid intermittent sprinklers, especially slow revolution sprinklers, that allow drying periods and cause salt to build up on the leaves.
Generally, 635mS/m (or 3500mg/L) of total salts is regarded as the maximum safe level for watering of any plants. With this salt content drainage must be excellent and each watering should apply enough water to leach accumulated salts below the roots of plants. Keep the water off the leaves to avoid burning. Where reticulation is used infrequently or only for short periods during the year, more saline water may be used. When watering with saline water closely observe the growth and condition of plants or herbage. Saline water can cause considerable yield loss before symptoms of leaf burn become obvious.