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MAGNESIUM IN THE CROP CYCLE

Magnesium in plant nutrition is often forgotten and shortages have negative implications on the plant’s growth. Nonetheless each variety has different needs, at each stage of development.

Cereals

 

Spread all across the globe, the cereals are known for being easy to cultivate and for their low fertilization requirements. Nevertheless they need a certain quantity of nutrients, in order to maintain a good yield and a satisfactory grain quality. Magnesium is crucial in the sugar transport from the foliar tissues to the grains during the grain filling process. The magnesium supply for the cereals is about 15 to 30 kg of MgO/ha/year according to the yield and the MgO soil content.

Regarding the winter crops, the magnesium uptake increases from the end of tillering until the flowering stage. Magnesium can be applied in various different forms. There are the slow release forms, like the oxide or the carbonate forms. These are applied to the soil in a powder or in a granular form. It needs to be planned before this critical uptake period, usually in autumn. Quickly available forms like the magnesium sulphate also exist. In this case, the supplementation can be used in two ways: via the soil by spreading granulates, from the end of the tillering stage, or via the foliar application by spraying a liquid containing the magnesium sulphate in a powder or in a crystal form, during the bolting stage.

For the spring cereals, the oxide and the carbonate forms are applied a few months before the sowing. The magnesium sulphate is applied either to the soil in granules just after the sowing or by foliar application when the last leave emerges.

 

Sources : Values calculated from the Comifer PKMg table ; INRA « le magnésium en agriculture » 1992

Rapeseed

 

Well known for its high sulphur demand, magnesium plays a significant role in the rapeseed’s crop cycle. Indeed, at the end of the winter period, the plant enters into an intense growth period. Therefore, its photosynthesizing activity and its foliar surface increase. Considering that magnesium is the central cation of the chlorophyll molecule, essential for photosynthesis, the need in magnesium increases considerably during the growth period.

The magnesium supply for the rapeseed is about 15 to 35 kg MgO/ha/year according to the yield and the MgO content in the soil. Magnesium can be applied under the oxide or the carbonate form at the sowing, in autumn for a slow release all along the crop cycle. It is also possible to apply the sulphate form. The application can be done in granules to the soil, usually at the end of the winter, just before the key uptake period, or by foliar application. This one is done to quickly respond to the rapeseed’s needs in magnesium, when they are the highest, that is between the end of bolting and the flowering stage.

 

Sources : Values calculated from the Comifer PKMg table

 

Sugarbeet

 

The sugar beet is one of the most demanding crops when it comes to fertilization and particularly for magnesium. In addition to covering a wide surface with its foliar tissues, the sugar beet demands a high amount of nutrients to ensure its root development. Magnesium plays an essential role in the sugar content because it favours the sugar transport from the leaves to the roots.

The magnesium supply starts from 35 to sometimes 90 kg MgO/ha/year, depending on the crop yield and its soil richness in magnesium. It can be applied under the oxide or the carbonate form a few months before sowing, at the end of the winter. Or it can be applied after the sowing in the sulphate form. The granular form has to be spread to the soil just after the sowing, whereas the foliar application can be done when the leaves cover 70% of ground.

 

Sources : Values calculated from the Comifer PKMg table ; INRA « le magnésium en agriculture » 1992

Potato

 

The potato is a crop that requires a particular attention to detail in terms of protection and nutrition. Indeed, the formation of a dense foliar system and the tuber makes it very demanding in nutrients. Magnesium has several impacts : it participates in the growth of the aerial tissues at the beginning of the crop cycle, then in the tubers development as well as their conservation after the harvest. It is thus essential all along the potato’s crop cycle.

The magnesium supply is estimated between 20 to 40 kg MgO/ha/year according to the targeted yield and the magnesium content in the soil. It can be applied in the oxide or the carbonate form a few months before the sowing, at the end of winter, or in the sulphate form after the sowing. If it is the magnesium sulphate in a granular form, it has to be spread on the soil within a few weeks, following the sowing. Otherwise, the foliar form is sprayed at the emergence of the first inflorescence until the flowering.

 

Sources : Values calculated from the Comifer PKMg table ; INRA « le magnésium en agriculture » 1992

Corn

 

One of the most cultivated crops in the world, corn has a fast growth cycle leading to an rapid increase in biomass. Corn is a plant with a C4 photosynthesis pathway, enabling it to better resist against dry climate conditions. However, this ability induces a heavier energetic cost than the other crops. Magnesium, in addition to being involved in the foliar tissue development in the photosynthesis, also is a co-factor in the activation of a large number of enzymes, especially relating to energy.

The magnesium supply is between 20 and 50 kg MgO/ha/year according to the crop yield and the magnesium soil content. It can be applied in either the oxide or the carbonate form, a few months before the sowing, at the end of winter. The aim in this case is to slowly release the magnesium for the crop when it emerges. The sulphate form otherwise can be applied after sowing.

The magnesium sulphate in granular form has to be spread to the soil immediately after sowing. The foliar form has to be sprayed when the leaves are developed enough, from the ten leaves stage until the tassels appear.

 

Sources : Values calculated from the Comifer PKMg table ; INRA « le magnésium en agriculture » 1992, RN’BIO