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For a “Minor” Element Molybdenum Has Big Impact For All Crops

To make sure the health of your plants and your yields are maximized in 2020, let’s do a quick refresher on molybdenum (Mo or abbreviated as “Moly”).

In a plant, Mo’s role is to transform nitrogen to amino acids.  In legumes it enables nitrogen fixation, leading to greater yields.  Sometimes referred to as “Poor Man’s lime”, Mo becomes more available in less acidic soils.  Essential to the success of a plant’s normal growth, only a small amount of Mo will ever be needed by your crops.

How much is enough? 

Molybdenum (Mo) is one of the eight ‘minor’ elements essential for plant growth. The others are boron, iron, manganese, zinc, copper, nickel and cobalt. They are labelled as minor because of the small amount plants generally need (approx. 50 grams per acre).

Studies have found that legumes followed by canola require the largest supply of Moly. Over the last few years, acreages and yields of both these crops have increased, and these crops are therefore extracting nutrients like Mo from the soil at higher levels.  

What happens to a crop without enough molybdenum?

In non-legume crops, Mo enables plants to use nitrates absorbed from the soil. Without enough Mo, plants can not efficiently reduce nitrates to ammonium for incorporation into amino acids.  Instead, nitrates accumulate in the leaves, causing the edges of the leaves to become scorched or burnt from the build up of the unused nitrates.

The same thing happens in legumes, but in legumes deficient in Mo, the enzyme nitrogenase is in low supply and therefore the ability of root nodule bacteria to fix atmospheric nitrogen is hampered.

In addition to nitrogen metabolism in plants, Mo is also involved in sulphur and phosphate metabolism and in the function of at least five other enzymes of importance.

Signs of molybdenum deficiency:

• Yellow-green colour and lack of vigor in clover
• Very similar to nitrogen deficiency symptoms (older leaves become yellow first)
• Interveinal chlorosis (yellow mottling between plant veins)
• Rolling, curling, withering and crinkling of leaves, and vegetable crops experience irregular leaf formation (whiptail)

Source: Fact Sheet ‘Molybdenum ranges in soil and tissues’ – A&L Canada Laboratories

How does soil pH factor in?

While most soils contain enough Molybdenum for plant growth, plant availability of this element is affected by soil pH, texture and weathering.

Mo deficiencies typically occur in acidic sandy soils with pH levels below about 5.8.

“Soil test results from across the Prairies shows that soils, especially in the top three or four inches, where minimum tillage is practiced, are acidifying,” explains Mike Dolinski (M.Sc, M.P.M.), Director of Science & Innovation at Taurus. “It’s happening all around the world and is a direct result of fertilizer application, and simply normal plant growth.”

In addition, there are also acidic soil zones found across the Prairies. Dolinski says Alberta has over 5 million acres of naturally acidic soil, mostly in central and northern Alberta, while Saskatchewan and Manitoba have fewer and more isolated acidic areas.

Because soil pH can vary drastically across the landscape and may be an unknown to the grower, this makes the supply of nutrients affected by low pH difficult to manage.

How best to apply Mo

One way to solve Molybdenum deficiency is to apply lime, as it will increase the soil pH and lead to it’s release from the soil.  However, this is a long-term play as it can take weeks to months to release the Mo into a plant available form.  As well, liming is not a practice commonly used by Western Canadian farmers.

That leaves application of Mo as a seed treatment, soil application or foliar application.

“Because soil or tissue tests may not provide a good indication of Moly levels across the landscape, a seed treatment or foliar application is generally a more reasonable approach,” says Dolinski. “Foliar application provides immediate uptake, and in legumes, Moly applied as a foliar spray in the early growth stages is preferentially translocated into the nodules and very effective in increasing final yield.” In soybean, peas, lentils, and faba beans in particular, Mo is very mobile in the plant (existing in its anion form) and therefore foliar application is very suitable.

For the benefits that molybdenum can provide, Active AgriScience and Taurus decided to add Mo to two of our 2020 products-  Active Build™ and Active PLS™.

Active PLS™ is a nutritional seed treatment that is specifically designed for legume crops and works synergistically with rhizobial inoculants to maximize nitrogen fixation. The benefits that Molybdenum can contribute to nitrogen metabolism make this a winning combination for stronger yields.

 Active Build ™ , with the highest concentration of N, P and K, promotes strong root growth and reduces evapotranspiration, allowing plants to sidestep the effects of drought conditions. At the same time, it helps plants handle other stresses, both biotic (pests and disease) and abiotic (herbicide application), enhancing photosynthetic capacity to help plants continue to grow through the stresses by keeping photosynthesis going.

In 2020…

In a season that will likely see some challenges, every advantage helps to lead towards a better crop.  We hope you find this Molybdenum refresher interesting and helpful towards maximizing vigor and yield in your fields this year.  

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Suggested reads:
The importance of Molybdenum- Grainews- https://www.grainews.ca/columns/the-importance-of-molybdenum/

A&L Labs Fact Sheet-Molybdenum Ranges in Soils and Tissues- https://www.alcanada.com/pdf/Tech_Bulletins/Soil/Nutrition/546-Molybdenum_Ranges.pdf

Nutri-Facts-Molybdenum- IPNI- http://www.ipni.net/publication/nutrifacts-na.nsf/0/71D0B217A35EEF1E85257D9600742FC6/$FILE/NutriFacts-NA-13.pdf

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