Iron
(Fe)
Iron is primarily used by chlorophyll for photosynthesis. Severe deficiency leads to chlorosis, for example in vines. In leguminous crops, iron plays a role in protein synthesis and in nitrogen fixation. Finally, iron participates in numerous enzymatic reactions and in plant respiration.
Very
Fairly
Moderately
Fe | ||
---|---|---|
Apple | ||
Pear | ||
Grape Vine | ||
Carrot | ||
Cabbage | ||
Cherries | ||
Spring Barley | ||
Strawberry | ||
Winter Barley | ||
Winter Wheat | ||
Winter Rapeseed | ||
Fiber Flax | ||
Cucumber | ||
Lettuce | ||
Grain Maize | ||
Silage Maize | ||
Potatoes | ||
Sugar Beet | ||
Sunflower | ||
Tomato |
As an important component of many enzymes it plays and important role for nitrogen reduction and fixation. Iron deficiency is frequently observed on crops growing on calcareous soils and causes significant reductions in yield and quality. Fe-deficiency is causing chlorosis, which is manifested by a yellowing of the interveinal areas of young leaves. In very severe cases, the entire leaf turns yellow and even white. Iron deficiency can easily be mistaken for nitrogen deficiency, which however affects the older leaves first.
Plants prone to iron toxicity include tomatoes and basil but iron toxicity is not very common. The symptoms include bronzing and stippling of leaves. Although iron is needed for chlorophyll production, too much iron can affect the functioning of chlorophyll. An excess of iron in the soil also impairs the uptake of other nutrients from the soil.
Analysing the soil’s iron content is a good method for identifying deficiencies. There are various extractives, in particular EDTA and DTPA chelate extraction, which are both reliable indicators. It should be noted that in limestone-rich soils, the required content is higher than in neutral to acid soils.
Organic matter plays an important role in the availability of iron but it also has antagonistic effects. The regular input of organic matter feeds the soil with iron and by combining with it, it reduces the chemical fixation or precipitation of iron as ferric hydroxide. On the other hand, rapid microbial respiration may produce sufficient carbon dioxide to form bicarbonate ions which immobilize iron within plants, resulting in deficiency.
A high soil pH and excess of Ca ions or bicarbonates in the soil solution, can induce Fe deficiencies.
Iron deficiency occurs most frequently in cool and wet soil early in the growing season. Humid and compacting conditions favour the reduction of iron from Fe3+ to Fe2+, along with reduction of stresses. However, in viticulture it has been observed that during rainy years iron deficiency increases.
LAT Nitrogen Austria GmbH
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4021 Linz, Austria