Crop and pasture yield can decline if the salts in irrigation water exceed certain levels.

Salinity problems may, however, be difficult to recognise because yields can decline by 20 to 30 per cent before signs of salinity are obvious.

Visible signs include plants being slow to germinate and establish, and stunted growth. Tips of leaves may also appear burnt, and then the whole plant may appear yellow or bronzed (especially if waterlogged).

In more severe cases, crops, pastures and trees may die off, salt crusts or greasy black patches may appear on the soil surface and the structure of the surface soil may appear loose and fluffy.

If using saline water, there are several factors to be aware of. You should know the quality of your water, remembering 1000 electrical conductivity (EC) or 640 parts per million water contains about 640 kilograms of salts per megalitre.

You should also use your best quality water for plant establishment and remember that some plants are more salt sensitive during the reproductive (flowering) stage.

Saline and fresher water can also be mixed together in a farm channel. This is a better option than alternating bore water and channel water.

The best time to use poorer quality water is for pre-watering winter crops, watering perennial pastures and lucerne, watering annual pastures after their second watering and during the mid-season stage (after germination and before flowering) of most annual field crops.

Avoid filling your storage dam with saline bore water, as the water may become more saline, increasing the dam’s leakiness and damaging the clay lining.

Excess sodium in irrigation water can lead to soil structure problems by causing dispersion, swelling and slaking after rain or if fresh irrigation water is used. This results in surface crusting, slow water penetration, poor internal drainage, low soil aeration, hardto- work soils, cloddy seedbeds and muddy water.

Be aware the use of saline-sodic water (water which is both saline and sodic) can lead to soil structure problems if it cannot leach quickly enough. Water is considered sodic if the Sodium Absorption Ratio (SAR) is three or more.

Avoid using groundwater more saline than 5000 EC, even if it is mixed with non-saline water.

When you finish watering with saline-sodic water, reduce the proportion of groundwater to channel water gradually over several waterings, as abrupt changes in water quality can worsen soil dispersion problems.

Under normal conditions, the salinity of bore water should be checked at the beginning and several times during the irrigation season. Checking should also occur after mixing saline water with fresher water, and during periods of low stream flows and a fresh in river flows (a flushing event following rains upstream).

NSW Department of Primary Industries has a standard water sampling kit to assist in determining water quality.

Contact your local NSW DPI irrigation or salinity officer.