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24 Sep 2021

Micronutrients and plant health

Micronutrients and Plant Health

by By Natalie Wood, Country Arable Agronomist, Yara UK

Micronutrients are essential for growing a healthy, productive crop that worksefficiently throughout its lifecycle. There are different micronutrients which are key to each crop,but on thewholethere are certain nutrients that are required at specific times to get the most out of your crops.

If we think about establishment, manganese and magnesium (which can also be thought of as a secondary nutrient) are the key micronutrients, on top of our major(or primary)nutrients N, PandK. Magnesium (Mg) is a key nutrient due to its central role as part ofthechlorophyll molecule-withoutMg there wouldnt be any chlorophyll and the plant wouldnt be able to carry out photosynthesis.

Mg is also involved in enzymatic reactions in the plant, increasing their velocity as well asintheformation of proteins and energy transfer.Oncea seed hasgerminated,we want the growth to be unhindered and the plants processes to be working at full capacity to get the seedling growing away, and avoidingpest damage,for example. Mg has many roles within the plant,sohaving a deficiency during the early stages of growth will have a real impact on the overall capability of the croptoestablish.

Whilesoils will have some level of magnesium present, it is often in an unavailable form to the plant and therefore deficiencies can easilyoccur, even during the early stages of growth. Mg deficiency symptoms areusually first seen in older leaves,withinitialpalingof theleaves andthen,as it becomes more severe,the leaves willhave interveinal chlorosis (yellowing). Eventually the whole leaf will becomeyellow. This is due to Mg being a central component ofchlorophyll,which gives plants their green colour.

Manganese (Mn) is, again, important for enzymatic reactions in the plant, production of amino acids and chlorophyll,as well as the metabolism of nitrogen. All of which are, of course, important for a newlyestablishing plant. Symptoms of Mn deficiency are seen on the younger leaves as chlorotic spots and streaks which, over time, turn grey,with overall plant growth stunted.Deficiency is made worse by unconsolidated soils, which is why the areas around tramlines can appear darker green due to the more compacted soils.

You can see there are similaritiesbetween Mg and Mninterms of theprocessesin which theyareinvolved, which is why these two nutrients are particularly important to plant growth, especially near the start of its life.If conditions are right, crops can putona lot ofbiomassbefore winter and therefore autumn applications of Mg and Mn can help ensure crop growth isnt being held back at this critical phase.

Another reason to ensure the crop has good levels of micronutrients is the fact that a healthy crop is better able to defend itself against disease and pest pressure. Think of it as a healthy animal being less likely to succumb to disease than one that is lacking good nutrition from a balanced diet it is the same for plants.

Work has been carried outto show how nutrients affect the incidence of disease in plants;large reductions in disease came from Mg, Mn, Copper (Cu), Boron (B) and Zinc (Zn). These are the key nutrientsto apply to autumn crops such as cereals and oilseed, the fact that applying them could also decrease the level of disease (and therefore fungicide spend) isan added bonus.

The labs at Yara Analytical Servicesproducemany routine tissueanalysisresults each year and if we look at the key nutrients for the 2021 season then there are still high numbers of deficiencies seen(Table 1).

Crop Nutrient Level of deficiency in samples


Magnesium 55%
Copper 70%
Zinc 70%


Magnesium 83%
Boron 70%
Molybdenum 58%

Table 1. Deficiency levels fromYara Analytical Servicesdata

To make life easier Yara has developed crop-specific products for cereals and oilseed in the form ofYaraVitaGramitrelandYaraVitaBrassitrelPro. Thesecontain all the key micronutrients for the respective crops.

Gramitrelcontains Mg, Mn, Cu and Zn, key for cereal crops,andBrassitrelPro contains Mg, Mn, Calcium (Ca) B and molybdenum (Mo) which, youve guessed it, are key for the oilseed crop. Having all the key nutrients in one can takes the hassle out of the autumn application and these productsare full tank mixablewith most autumn pesticides too (you can check your mixture at You can then follow up with another application in the spring to catch the key growth timing or take a tissue test togo down the more precise route of applying straight micronutrients.

Whilehavinga healthier plant might sound like a good thing can you equate this to yield increases? The answer to that is yes.Yara carries out trials on these products each year and there is a long-term average yield benefit over the pastsixyearsof 0.30t/ha from both cereal and oilseed crops. However,each season is different for example this years trial gave a massive 1.0t/ha yield increase fromtwoapplicationsofYaraVitaGramitrel(autumn and spring).The return on investment (ROI) can be huge when you getthese kind of increases,but there is also a good ROI on the long-term average of 0.3t/ha,making the applicationswellworth it.

So, apply micronutrientsto your crops and be confidentthey have all the nutrition they need thisautumnto growto their optimum and give them the best chance of overwinter survival,and, ultimately,to producemaximum yield next harvest.

For more information on micronutrientssearch YaraVita, orvisit

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