Magnesium (Mg) promotes good plant growth, being an essential nutrient that intervenes decisively in the formation of chlorophyll, necessary for photosynthesis.
Making a brief history of magnesium as a fertilizer, this element was discovered in 1755 by the Scottish chemist Joseph Black, being isolated (as metallic magnesium) for the first time in 1808 by the English chemist Humphry Davy.
Practically a century later, in the 1920s, magnesium deficiency in plants was recognized, when researchers noticed that plants grown in low-magnesium soils showed symptoms of deficiency, such as yellowed leaves.
But a few years earlier magnesium was already used as a nutrient for plants and in fact, in 1904, the German botanist Julius von Sachs showed that magnesium was an essential element.
Since then, magnesium has been used in the field of plant agronutrition for the proper development of crops, either including it through the application of fertilizers that contain it or fertilizers especially rich in it.
Magnesium in the soil.
The nutrient magnesium (Mg) can be found in soil in different forms, including:
- Ion Mg2+ in the soil solution, which can be directly absorbed by the roots.
- As Mg2+ ion fixed at the cation exchange positions of the soil.
- Frequently in saline soils, forming salts such as sulfate MgSO4.H2O, or magnesium MgCl2.nH2O chloride.
- In certain soil minerals such as dolomite CaMg(CO3)2 or magnesium calcites MgCO3 where Mg partially replaces Ca2+.
- As a structural component of the siliceous crystal lattice of some clays such as vermiculite, montmorillonite (a mineral of the silicate group) or sepiolite.
Symptoms of magnesium deficiency in plants
1. Yellow leaves
This is one of the most common symptoms of magnesium deficiency. The leaves will start to turn yellow and then brown as the deficiency becomes more severe. In plants suffering magnesium deficiency, older leaves show interveinal chlorosis(dark green veins with yellow areas between them)
2. Wilting leaves
Magnesium is necessary for plants to maintain turgor pressure. When they are deficient in magnesium, plants will start to wilt.
3. Poor growth
If a plant is magnesium deficient, it will not grow as well as it should. This will result in slow growth. It may be stunted or have a reduced number of leaves. The deficiency is often not directly visible but still negatively affects crop growth.
4. Dead patches
If the deficiency is severe, it can cause dead patches on the leaves.
5. Brown patches
Brown patches on the leaves are another sign of a magnesium deficiency.
6. Curling of the leaf edges
The leaves may start to curl up is a sign of severe magnesium deficiency.
7. Rust-colored spots
The areas on the leaves that are affected by the magnesium deficiency will often be rust-colored.
8. Necrosis
The plant tissue in the leaves will start to die if there is a magnesium deficiency.
9. Poor fruit production
A magnesium deficiency can also affect the fruit production of a plant. The fruits may be smaller than normal or may not ripen properly.
10. Blossom end rot
Blossom end rot is a condition that affects the tomato plant and other fruit of plants. The bottom part of the fruit will start to turn black and rotten. This is often due to magnesium deficiency.
