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Why is Salinity Important?
Constant shallow watering during drought periods can result in elevated levels of salts in the top soil. Salinity results in rapid uptake of salts to toxic levels, This can badly damage or kill trees. Fruit tree's are generally considered to be sensitive and a reduced yield can be experienced even with fairly low levels, because:
- water is naturally attracted to higher salt levels - if soil is high in salt, it binds the water strongly and becomes difficult for the tree to extract (ie. in effect, the saline soil reduces the available water)
- excesses in some salts (Eg. sodium and chloride) can poison the tree.
- excess salts taken up by the tree are stored in the woody tissues
Symptoms of salt damage include:
- leaf burn
- leaf drop
- reduced vigour, yield and size
- trees may appear wilted (despite moist soil)
- chloride and sodium present in leaves.
| Species of Fruit | Salinity at initial yield
decline (threshold) (ECe) | Yield decrease per unit increase
in salinity beyond the threshold (%) |
| Apple | 1.0 | 18 |
| Almond | 1.5 | 19 |
| Apricot | 1.6 | 24 |
| Grape | 1.5 | 9.6 |
| orange | 1.7 | 16 |
| Peach | 1.7 | 21 |
| Plum | 1.5 | 18 |
| Pear | 1.0 | - |
(Source: Guide to best practice water management - orchard crops, Page 51-53)
Salt Sensitivity?
Irrigation scheduling and soil moisture monitoring will be vital in the management of saline irrigation area's.
The following table can be used as a guide.
Soil salinity levels should generally be kept below 2.0 dS/m (ECe) for fruit trees.
Sensitivity of various crops to salt.
| Sensitive | Moderate sensitivity | Moderate tolerance | Tolerance |
| Apple | Grapes | Squash | Salt Bush |
| Apricot | Potato | Zucchini | Olives |
| Cherry | Tomato | Ryegrass | Date Palms |
| Citrus | Lucerne | Strawberry Clover |  |
| Peach | | Barley | |
| Pear | | | |
| Plum | | | |
General salt tolerance levels.
| ECe dS/m | Result |
| 0 - 0.5 | Very low salinity; all crops will grow |
| 0.5 - 2.0 | Low soil salinity; level is generally safe for fruit trees. |
| 2.0 - 3.0 | Soil salinity slightly above threshold for fruit trees; leaching management will be needed to reduce salinity. |
| > 3.0 | High soil salinity for fruit trees; specific management needs to be adopted; grow more salt tolerant crops. If levels are above 3.0, further investigation will be required. |
Recommended maximum soil EC levels for fruit production
| Soil Type | EC1:5 (dS/m) Quicker Measurement | ECe (dS/m) Standard
Measurement |
| Medium Clay | 0.27 | 2.0 |
| Loam | 0.21 | 2.0 |
| Sandy Clay Loam | 0.14 | 2.0 |
(Source: Guide to best practice water management - orchard crops, Page 52)
Soil Salinity Bench Mark Data?
Soil Sample results Will give Electrical Conductivity (ECe) values, which is a measure of the soil salinity. The tables below show benchmark data collected from 40 growers in Ardmona, Cobram, Shepparton East and Swan Hill.
Location | Soil ECe (dS/m) 0 - 25 cm Depth | Soil ECe (dS/m) 25 - 45 cm Depth |
1997 - 98 | 1998 - 99 | 1997 - 98 | 1998 - 99 |
Average | Range | Average | Range | Average | Range | Average | Range |
| Ardmona | 0.55 | 0.27 - 1.24 | 1.27 | 0.73 - 1.93 | 0.46 | 0.30 - 0.56 | 1.25 | 0.73 - 2.22 |
| Shepparton East | 0.69 | 0.21 - 2.23 | 1.02 | 0.44 - 2.61 | 0.59 | 0.21 - 2.27 | 0.93 | 0.32 - 2.58 |
| Cobram | 1.26 | 0.05 - 4.52 | 1.76 | 0.79 - 3.48 | 1.54 | 0.26 - 5.33 | 2.90 | 0.77 - 4.42 |
| Swan Hill | 1.67 | 0.48 - 4.65 | 1.03 | 0.82 - 1.35 | 1.47 | 0.51 - 4.31 | 0.98 | 0.58 - 1.59 |
(Source: Guide to best practice water management - orchard crops, Page 91)
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