Salinity is one of the major challenges facing olive growers in many regions of the Mediterranean. Although the olive tree has a relative tolerance to saline soils, excessive salt concentration can significantly affect the health and productivity of the trees.
How does salinity affect the olive tree?
Nutrient imbalance When the soil contains high concentrations of sodium and chlorine, trees have difficulty absorbing essential nutrients. Sodium ‘competes’ with potassium, interfering with its uptake by the roots – something you can see from yellowing leaves and weakening vegetation.
Effects on growth Salinity creates conditions of “normal drought” – although the soil appears moist, water is not available for the tree. You will notice:
- Less annual vegetation
- Reduced leaf size
- Limited flowering
- Smaller fruits with low oil content
Practical fertilisation solutions for saline soils
1. Selection of suitable fertilizers
Calcium – The Ally Against Sodium The addition of gypsum (calcium sulphate) helps to displace sodium from the soil. Apply 1-2 pounds per tree during the winter season when rainfall will help incorporate it.
Potassium – strengthening the tree’s defences Potassium fertilisers are essential in saline soils. Prefer potassium sulphate to potassium chloride, as the latter increases salinity. Application of 300-500 grams per tree in spring enhances resistance to saline environment.
Nitrogen – care in selection Use nitrate forms of nitrogen (calcium or potassium nitrate) and avoid ammoniacal forms, which can aggravate salinity problems. Apply small, frequent doses instead of one large application.
2. Salinity management techniques in the field
Effective soil leaching Salt leaching is an option for maintaining tree health in dangerous high salinity conditions:
- Apply 20-30% more water than normal irrigation needs
- Prefer drip irrigation with drippers away from the trunk
- Perform deep irrigation every 2-3 months especially for salt leaching.
Organic enrichment The addition of compost or manure (3-5 kg per tree per year) dramatically improves the soil condition:
- Increases water retention
- Improves drainage
- Binds sodium ions
- Gradually releases nutrients
3. Selection of resistant varieties
If you are starting a new planting in an area with salinity problems, choose resistant varieties such as:
- Lefkoelia Serres
- Koroneiki
- Kalamata
- Picual
