Micronutrients and Plant Health 

Micronutrients are essential for growing a healthy, productive crop that works efficiently throughout its lifecycle. There are different micronutrients which are key to each crop, but on the whole there 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, P and K. Magnesium (Mg) is a key nutrient due to its central role as part of the chlorophyll molecule –  without Mg there wouldn’t be any chlorophyll and the plant wouldn’t be able to carry out photosynthesis.  

Mg is also involved in enzymatic reactions in the plant, increasing their velocity as well as in the formation of proteins and energy transfer. Once a seed has germinated, we want the growth to be unhindered and the plant’s processes to be working at full capacity to get the seedling growing away, and avoiding pest damage, for example. Mg has many roles within the plant, so having a deficiency during the early stages of growth will have a real impact on the overall capability of the crop to establish.  

While soils will have some level of magnesium present, it is often in an unavailable form to the plant and therefore deficiencies can easily occur, even during the early stages of growth. Mg deficiency symptoms are usually first seen in older leaves, with initial paling of the leaves and then, as it becomes more severe, the leaves will have interveinal chlorosis (yellowing). Eventually the whole leaf will become yellow. This is due to Mg being a central component of chlorophyll, 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 newly establishing 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 similarities between Mg and Mn in terms of the processes in which they are involved, 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 put on a lot of biomass before winter and therefore autumn applications of Mg and Mn can help ensure crop growth isn’t 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 out to 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 nutrients to 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) is an added bonus. 

The labs at Yara Analytical Services produce many routine tissue analysis results 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
Wheat	Magnesium	55%
	Copper	70%
	Zinc	70%
Oilseed	Magnesium	83%
	Boron	70%
	Molybdenum	58%

Table 1. Deficiency levels from Yara Analytical Services data 

To make life easier Yara has developed crop-specific products for cereals and oilseed in the form of YaraVita Gramitrel and YaraVita Brassitrel Pro. These contain all the key micronutrients for the respective crops. 

Gramitrel contains Mg, Mn, Cu and Zn, key for cereal crops, and Brassitrel Pro contains Mg, Mn, Calcium (Ca) B and molybdenum (Mo) which, you’ve 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 products are full tank mixable with most autumn pesticides too (you can check your mixture at tankmix.com). You can then follow up with another application in the spring to catch the key growth timing or take a tissue test to go down the more precise route of applying straight micronutrients. 

Whilehaving a 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 past sixyears of 0.30t/ha from both cereal and oilseed crops. However, each season is different – for example this year’s trial gave a massive 1.0t/ha yield increase from twoapplications of YaraVita Gramitrel (autumn and spring). The return on investment (ROI) can be huge when you get these kind of increases, but there is also a good ROI on the long-term average of 0.3t/ha, making the applications well worth it. 

So, apply micronutrients to your crops and be confident they have all the nutrition they need this autumn to grow to their optimum and give them the best chance of overwinter survival, and, ultimately, to produce maximum yield next harvest. 

For more information on micronutrients search “YaraVita”, or visit www.yara.co.uk