The Importance of Molybdenum in Plant Nutrition

In the pursuit of higher yields and sustainable agriculture, micronutrients often play an outsized role despite their minimal presence in the soil. One such essential micronutrient is molybdenum (Mo) which is critical for the optimal growth and productivity of agricultural crops. Plants take up Mo as the MoO₄⁻² anion.

Why molybdenum matters

Molybdenum is a key component of several plant enzymes, most notably nitrate reductase and nitrogenase, which are vital for nitrogen metabolism. These enzymes enable plants to convert nitrate into usable forms of nitrogen and, in legumes, facilitate biological nitrogen fixation through symbiotic relationships with Rhizobium bacteria.

Without sufficient molybdenum, plants struggle to utilise nitrogen efficiently, leading to symptoms such as stunted growth, leaf chlorosis, and poor yield quality. This is particularly critical in crops like soybeans, alfalfa, canola, and cauliflower, which have higher molybdenum demands. Legumes are particularly molybdenum-hungry crops, as they need more molybdenum to fix nitrogen to their root nodules.

Soil and crop management

Molybdenum availability is highly pH-dependent. Molybdenum becomes more available as soil pH increases, the opposite of most other micronutrients. Acidic soils (pH < 5.5) often limit molybdenum uptake due to maximal adsorption of Mo anions in the soil by Fe and Al oxides. This makes soil pH management and targeted molybdenum fertilisation essential strategies. Applying molybdenum-enriched fertilizers or foliar sprays can correct deficiencies and enhance crop performance, especially in sensitive growth stages.

Deficiency symptoms of molybdenum

Molybdenum deficiency is relatively rare but can be highly detrimental, especially in acidic soils. Molybdenum is a mobile nutrient, so it translocated to the growing parts, leaving the older leaves with deficiency symptoms.

Common symptoms include:

• Interveinal chlorosis (yellowing between leaf veins), especially in older leaves
• Stunted growth and reduced leaf size
• Marginal leaf scorching or cupping
• Poor pod or flower development in legumes
• Whiptail disorder in cauliflower (distorted, narrow leaves)
• Reduced nitrogen fixation in legumes due to impaired nodule function

These symptoms often resemble nitrogen deficiency, making accurate diagnosis essential.

Molybdenum deficiency in cauliflower crop. Photo contributed by Takeshi Shimizu, Encyclopedia Nutrient Disorder Diagnosis (ISBN 13: 978-4540171666; ISBN 10: 4540171666)

Molybdenum deficiency in spinach crop. Photo contributed by Takeshi Shimizu, Encyclopedia Nutrient Disorder Diagnosis (ISBN 13: 978-4540171666; ISBN 10: 4540171666)

Sources of molybdenum for crops

To prevent or correct deficiencies, molybdenum is supplied as inorganic forms (molybdates). They can be incorporated in NPK fertilisers fortified with Mo, in seed treatments for legumes to enhance early nodulation and can be combined with lime in acidic soils to improve availability.

ICL’s commitment to balanced nutrition

At ICL Growing Solutions, we understand that balanced plant nutrition is the foundation of resilient and productive agriculture. Our innovative fertiliser solutions are designed to deliver essential micronutrients like molybdenum in forms that are readily available and effective across diverse soil conditions.

Plants need molybdenum to help process the nitrogen they need for their nutrition. Agroleaf® Liquid MolyComplex delivers it to them.  Agroleaf® Liquid MolyComplex is developed for use in both foliar and root applications, a nutritional supplement for plants requiring molybdenum in large amounts, preventing and correcting any deficiencies.

Other ICL fertilisers with molybdenum are: Agrolution Liquid ME-5 and M-6, and Agroleaf® Liquid MolyB.

The new line of ICL biostimulants, BIOZ® and BEOZ®, include molybdenum in their composition: Nephrite, Topaz, Sunstone, Onyx Annual, Onyx Permanent and Moonstone contain molybdenum, which is the core nutrient formulated in these products.

By integrating molybdenum into your crop nutrition program, you not only support robust plant development but also maximize the efficiency of nitrogen fertilisers—boosting both yield and sustainability.