Olives are grown in a variety of soils and conditions. Therefore customised management of tree nutrition is required.
The four tools for optimal nutrient management are:
- Observation of trees and environmental conditions.
- Soil and water analysis.
- Leaf analysis.
Visual symptoms should be used as an aid to interpreting soil and leaf analyses:
- Look for abnormal symptoms in foliage or growth.
- Look for significant variations in yield.
- Observation can suggest deficiencies of:
- potassium, and
Initial leaf analysis should be undertaken when the trees are two years old, then on a regular basis. A standard analysis will cost approximately $70.
- Summer (January) is the best time to undertake leaf tissue analysis.
- Levels of most nutrients stabilise in the olive leaf during January and February.
- Standards for optimum leaf nutrient concentrations are given in The Olive Handbook.
- For the analysis:
- Remove 4 mature leaves per tree from the middle of current season non-bearing shoots from 25 trees.
- Trees should be of similar size and on a single soil type.
- Different samples should be taken for widely differing soils.
- Wrap leaves in paper bags or newspaper, NOT plastic or other material which will make them sweat.
- If testing for Boron, mature fruit samples may be more reliable than leaf samples.
Soil and Water Analysis
- Soil and water analysis should be undertaken during site selection and deficiencies rectified during site preparation.
- This should be followed by continuous analysis at two-year intervals.
- Reliable standards for soil mineral nutrients for fruit trees are lacking so analysis should be considered in conjunction with leaf analysis.
- A standard soil analysis should provide information on the following soil conditions and nutrients and will cost approximately $70.
- pH - indicating soil acidity
- salt - indicating salinity levels
- organic carbon
- total nitrogen %
- phosphorus %
- potassium %
- sulphur %
- calcium %
- magnesium %
- copper mg/kg
- zinc mg/kg
- Spreading fertiliser well beyond the root zone is a waste.
- Cover the entire present root zone.
- Extend slightly beyond root zone to allow for new growth.
- Generally, the diameter of the root zone is @ 2-3 x the foliage area.
The following table suggests nitrate application for spring plantings: