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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.
  • Recording.

Observation

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:
    • nitrogen,
    • potassium, and
    • boron.

Leaf Analysis

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
    • moisture
    • organic carbon
    • total nitrogen %
    • phosphorus %
    • potassium %
    • sulphur %
    • calcium %
    • magnesium %
    • copper mg/kg
    • zinc mg/kg

Fertiliser Application

  • 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:

Year Month Ammonium Nitrate per Tree Root Zone Diameter
1 Oct/Nov/Dec 42gm 0.6m
1 Jan 50gm 0.9m
1 Feb  50-63gm 1.2m
2 Aug 85gm 1.8m
2 Nov  110gm 2.1m
2 Feb 120gm 2.7m
3 Aug 125gm  3.4m
3 Nov 140gm 3.7m
3 Feb 150gm 4.3m
4 Apply fertiliser in response to leaf and soil analysis.