Magnesium

MAGNESIUM

Energy is required for proper plant growth. Wheat and other crops require magnesium to capture the sun's energy for growth and production through photosynthesis. Magnesium is an essential component of the chlorophyll molecule, with each molecule containing 6.7 percent magnesium. Chlorophyll, the green pigment in plants, is the site where photosynthesis occurs. Without chlorophyll, plants could not manufacture food, and life on Earth would cease to exist.

Magnesium also acts as a phosphorus carrier in plants. It is necessary for cell division and protein formation. Phosphorus uptake could not occur without magnesium, and vice versa. So, magnesium is essential for phosphate metabolism, plant respiration and the activation of several enzyme systems.

Magnesium in Soils
The Earth's crust contains about 1.9 percent Mg, largely in the form of Mg-containing minerals. As these minerals slowly weather, some Mg is made available to plants. The supply of available Mg has been or is being depleted in some soils through leaching, plant uptake and removal processes.

Magnesium availability to plants is often related to soil pH. Research has shown that

Mg availability to the plant decreases at low pH values. On acid soils with a pH below about 5.8, excessive hydrogen and aluminum can influence Mg availability and plant uptake. At high pH values (above 7.4), excessive calcium may have an overriding influence on Mg uptake by plants.

Sandy soils with low cation exchange capacity have a low Mg-supplying power.

Application of high-calcium limestone can aggravate an Mg deficiency by increasing plant growth and increasing the demand for Mg. High applications of ammonium and potassium may also interfere with balanced nutrition through competitive ion effects. If soil test levels are below 25 to 50 parts per million (ppm) – 50 to 100 lb/acre – exchangeable Mg is usually considered low, and Mg application is warranted.

Symptoms of Magnesium Deficiency
Magnesium is mobile within the plant and easily translocated from older to younger tissues. When deficiencies occur, the older leaves are affected first.

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