Magnesium
Magnesium is an essential part of chlorophyll and aids in the formation of sugars, oils and fats. Magnesium is a part of the chlorophyll molecule, magnesium deficient trees have older leaves that are pale in colour. Leaf analysis is the best way to evaluate magnesium requirements.
Identification
- Magnesium is mobile within the plant and therefore deficiency usually appears first on the older leaves as it translocates to the growing tissue,
- The leaf tissue between the veins turns yellow, while the veins remain green,
- Severe deficiencies will cause the leaf margins to curl,
- Necrotic spots develop later and eventually the leaves drop prematurely,
- If deficiency is prolonged, only a few pale leaves are left at the growing tip,
- Fruit matures early, is highly coloured and drops prematurely,
- Fruit bud formation may be limited.
- pesticide spray damage yellowing and browning of leaf margins and interveinal areas,
- herbicides such as triazines (simazine, atrazine); ureas (diuron, linuron), uracil (terbacil, bromacil); dichlobenil, paraquat, fluazifop-butyl, oxadiazon.
- mechanical damage to tree bark,
- leaf scorch root injury.
- availability is reduced when potassium levels are excessive,
- conditions which limit root growth such as wet, dry, or cold soils can reduce magnesium availability,
- excessive boron also causes interveinal and marginal leaf scorch.
Often Confused With
Chemical:
Mechanical:
Soil & planting conditions:
Scouting Notes
Symptoms are most pronounced at the end of the growing season and are more severe in wet years.
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