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  • Molybdenum (Mo)
    4294.95
    Mo
  • Forme ionique
    Molybdenum (Mo) ionic formula image
  • Anion/Cation
    MoO42-
  • Molybdenum (Mo) influance image
    Leaf
  • Molybdenum (Mo) origin image
    Origine: Volcanic
  • Molybdenum (Mo) mobility image
    15mm around the root

Molybdenum

(Mo)

The behaviour of molybdenum is totally different from other trace elements in relation to soil pH: it is not available in acidic soil but becomes very soluble and can be mobilised in basic soil. The quantities involved are very small and require precision and moderation in the applications.
Mo
Plante
Plante
Sol
Sol
Culture
Culture
Origine
Origine
Clés
Clés
IMPORTANCE FOR THE PLANT:
Molybdenum is involved mainly in enzymatic mechanisms related to the assimilation of nitrogen (nitrogenase and nitrate reductase).
ABSORPTION MECHANISMS:
Molybdenum is absorbed via the soil solution as anion.
INTERACTIONS, SPECIFICITY:
Molybdenum works quite well in synergy with phosphorus. Sulphur has an acidifying effect in the soil which impedes the availability of Mo.
Unlike other trace elements, molybdenum is unavailable in acidic soils. It is then strongly linked to iron. With increasing pH-value, molybdenum becomes mobile and its availability strongly increases. Fresh organic matter ensures a good supply of Mo. This is obviously not the case for peat, which develops under acidic conditions. The graph shows the different forms of Mo depending on the pH-value in the soil. It clearly turns out that the content of MoO 4 2- , the plant-assimilable form, strongly increases with higher pH-value.
SOIL ANALYSIS:
Molybdenum is extracted specifically with oxalate. A soil analysis for Mo is not common but can be done upon request.

Tableau de sensibilité

Echelle de sensibilité:
  • nutrient very sensible icon

    Hautement

  • nutrient very fairly icon

    Moyennement

  • nutrient very moderately icon

    Modérément

Mo
Sugar Beet
Wheat
Carrot
Alfalfa
Melon
Potatoes
Soya
Tomatoes
Cauliflower
Spinach
Clover
Letuce
Rapeseed
Broccoli
Citrus
Oat
Pea
Radish
Turnip
Maize
Barley
Rye
Sorghum
Rice
Apple & Pear
Vineyard
Asparagus
Peach

Tableau sensibilités & Symptômes

Symptoms of Mo deficiency are similar like symptoms of nitrogen deficiency in legumes. Since Mo is necessary for the activity of nitrogenase and the fixation of N 2 , an N-deficiency can be observed. On crucifers, interveinal chlorotic plaques appear on the leaves, with a greyish colour and a soft consistency. In the most severe cases, the leaves of the plants are completely deformed.

Excès & Besoins

Excess molybdenum blocks copper and may induce deficiencies in cereals and fodder grasses. Acidophilic crops, such as rubber, are sensitive to any excess of molybdenum.

The soil content varies greatly depending on the source rocks, the iron content and the level of acidity. In general, assimilable Mo is higher in alkaline soils, soils rich in organic matter and young soils derived from volcanic rocks, whereas soils rich in iron have low Mo contents. Fertilizers contain Mo as sodium or ammonium molybdate.
SOIL CONTENT:
Mo soil analyses are not routinely performed. However, a soil poor in Mo and rich in iron, induces a deficiency for the demanding crops.
ORGANIC MATTER CONTENT:
A high organic matter content, may, in low pH, reduce the risk of deficiency. Regular inputs of organic matter can provide soluble Mo for crops. Conversely, peat input creates a retention of Mo on humic acids.
CLIMATE:
High temperature above 25° C increase Mo solubility in soils. Dry conditions, on the other hand, cause deficiencies in Mo.
pH:
This is the most important factor for the absorption of Mo by plants. At high pH, Mo is very mobile.
INTERACTION WITH OTHER ELEMENTS:
Phosphorus facilitates the absorption and transport of molybdenum. This positive interaction is found when Mo is combined with P. High levels of iron contribute to limiting the assimilability of Mo. An excess of copper as well as inputs of Cu decrease the absorption of Mo; an excess of manganese shows the same effect.