Magnesium and other elements
Calcium and magnesium are both soil alkaline elements with the same behavior in the soil, but the amount of calcium in the soil is usually higher in comparison to magnesium. It is worth noting that magnesium is stronger than calcium in increasing the soil pH and increases it to more than 8.5. This can even cause poisoning of the trees.
Magnesium is absorbed into the plant as the Mg2+ ions and its absorption rate depends on the degree of soil saturation, its exchange capacity, clay and the elements in the soil, and soil type. For instance, in calcareous soils, due to the antagonistic effects with calcium (calcium absorption), relatively severe deficiencies can be witnessed. Magnesium deficiency is also more found in gardens with sandy soils. The excessive amount of potassium and nitrogen in the soil makes it difficult for the plant to absorb magnesium due to the competitive effects. Magnesium deficiency can be observed in soils that are fertilized with potassium or fertilizers containing nitrogen in an uncontrolled and unscientific way. Besides, excessive irrigation causes magnesium to be washed and transferred to deeper areas of the soil.
Excessive copper increase and toxicity in the soil can be compensated for by the use of magnesium.