Use of Magnesium to complement fertilization

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How to adjust management to increase use efficiency and its result on crop productivity and quality

It is very common to hear similar answers when a question about fertilization and plant nutrition is asked, regardless of the crop to be fertilized or region. The question is: “how do you manage Magnesium in fertilizers?” The answer – most of the time – comes as a simple statement: “I keep quiet”.

There is no doubt about the importance of soil correction. The positive and beneficial effects of applying lime and other sources that act to correct soil acidity are indisputable. Adjusting the pH, which is the acronym used to define the Hydrogenionic potential of the medium, or in a more practical and applied way, indicating whether the soil is acidic or basic, is fundamental to defining the behavior of the medium in which the roots will develop and They will be responsible for absorbing water and nutrients throughout the life of the plants. 

Liming, when recommended based on technical criteria such as soil analyzes and methodologies validated in Brazilian soils - base saturation (V%), pH SMP, increase in exchangeable Ca and Mg - guarantees that the soil pH is always within ranges suitable for better nutrient availability and root growth and development. Whether in direct planting, minimum cultivation, perennial crops, pasture renovation, one thing is certain: applying correctives is the first step when thinking about efficient fertilization.

But, even for a nutrient applied in liming, it is increasingly clear that it should not be the only step to be considered for its adequate and efficient supply. The nutrient that has shown excellent results when supplemented in fertilizers is Magnesium (Mg).

Magnesium plays an extremely important role in various functions within plants and positively impacts processes related to crop growth and productivity. In general, a large part of magnesium is found in chlorophyll, which is the pigment responsible for the photosynthesis process in which sunlight is converted into chemical energy to be used by plants throughout their cycle. Plants with a low magnesium content may have problems absorbing light energy from the sun and the accumulation of this energy can cause great damage, not always noticeable, to the leaves. Thus, plants well supplied with magnesium throughout the cycle tend to be more tolerant to thermal stress and make better use of water, solar energy and nutrients.

Another vital process to guarantee plant production, and which Magnesium is fundamental, is the transport of sugars from the leaves to the roots, shoots and reproductive organs. Therefore, plants deficient in magnesium may present a reduction in the growth of roots and vegetative structures such as leaves, stems, pods and, mainly, seeds, directly impacting the productivity and quality of crops.

Seeing how magnesium acts on plants and when it is most demanded, it is likely that the importance of applying this nutrient in fertilizers will begin to make more sense. But if it's still not very clear, there are some other points related not only to plants, but to interactions between nutrients in the soil that can help explain, a little more, the importance of magnesium intake at different stages of cultivation.

One of these interactions is related to the bases in the soil, which are Calcium (Ca), Magnesium (Mg) and Potassium (K). There are numerous scientific works that demonstrate the importance not only of the absolute levels of these nutrients in the soil, but mainly in relation to the balance between them for the best use by plants. Specifically in relation to Magnesium, high levels of Ca and K in the soil or in fertilizers can hinder or prevent the absorption of Mg by the roots. This means that, even though magnesium is in the soil and supplied via liming, plants may not have full access, which may present deficiencies and, consequently, the negative effects already presented above. 

In general, even limestones classified as dolomitic, that is, which have magnesium levels (expressed as MgO) above 12%, also contain high levels of calcium and, depending on the levels in the soil, may not provide all the magnesium required. crops at the appropriate time. Additionally, we must remember that the most abundant source of Mg supplied in correctors is magnesium carbonate, which requires contact with the soil and reaction time to release the carbonate, which is mainly responsible for pH correction, as well as magnesium , which will be retained in the soil.

Returning to the concepts presented that can, to a certain extent, limit the efficiency of using magnesium, what would be the way to provide this nutrient in fertilization without changing too much management or even operations in the field and increasing the productivity and quality of crops? Mosaic Fertilizers’ response: K-Mag.

K-Mag is a product that contains, in a single granule, magnesium, potassium and sulfur. As it is a double sulfate of potassium and magnesium, it has high solubility and immediate availability of nutrients. Furthermore, it is a highly concentrated product, containing 10,5% Mg, 21% K2O and 21% S.

The advantages of using K-Mag in fertilizers range from the possibility of applying the product as such to provide doses of magnesium in cover crops that require potassium and sulfur, as in the case of grains, or even in fertilizer mixtures containing other nutrients such as nitrogen, phosphorus and micronutrients for use in perennial crops such as coffee, sugarcane and citrus. 

Another great advantage of K-Mag is that it contains very low levels of chlorine, which makes it an extremely interesting solution for crops that are sensitive to this element or that require higher quality products such as potatoes, onions, garlic , tobacco, coffee and citrus.

Knowing a little about K-Mag now, if you are in the situation of being asked about how you manage magnesium in your crops, it is very likely that the answer will still come to your mind as a simple, but more complete statement: “I do liming ... and I use K-Mag!”