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| Author: | K. Sommer |
Abstract:
The lime induced iron chlorosis in fruit trees is a widespread and up to now unresolved problem in plant nutrition on calcareous soils in arid and semiarid areas.
On average some 20% to 50% of different kinds of fruit trees suffer from this type of physiological disorder and show symptoms of iron deficiency.
This is accompanied by poor yields, low fruit quality and the complete loss of trees.
In order to overcome iron chloroses ironchelates are either applied to the leaves or to the roots of the trees.
While being rather expensive these kinds of treatments have up to now been of limited success and have hence proved unprofitable in many cases.
In order to overcome these difficulties we propose to solve the problem of iron chloroses in fruit trees by a newly developed technique based on the “CULTAN” system according to Sommer.
With this technique a proportion of the roots of a fruit tree is directed to a certain spot in the root zone by ammonium attraction.
There for every tree about one liter of calcareous soil is replaced by compost material, which is enriched with iron and ammonium as sulfates and acidified by sulfuric acid to yield a pH-value of 3,0. The ammonium in this mixture is stabilized by a nitrification inhibitor.
From these spots trees take up ammonium, iron and sulfate — the latter being taken up as active sulfate in high surplus according to needs of sulfur of the plants.
Therefore, a large amount of sulfate is available in the trees for the bonding calcium, which has been taken up from soil solutions rich in calcium carbonate or calcium bicarbonate.
Thus metabolic carboxylation processes of the plants are supplemented with the surplus of sulfate to stabilize the pH-value of the plant sap.
This is the main idea of our approach to solving the problem of iron deficiency.
In a number of countries this technique has proved to be an effective and economical way of overcoming lime induced iron chlorosis.
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