Hidden in the heart of each chlorophyll molecule is an atom of magnesium (Mg), making the nutrient actively involved in photosynthesis. Magnesium also aids in phosphate metabolism, plant respiration and the activation of many enzyme systems.

Quick Facts

Magnesium is mobile within the plant and moves easily from older to younger tissues.

Quick Facts

Plants require Mg to capture the sun's energy for growth and production through photosynthesis.

Quick Facts

When Mg deficiencies occur, the lower (older) leaves are affected first.

Quick Facts

The most common source of Mg is dolomitic limestone, which provides both calcium and Mg, while neutralizing soil acidity.

Quick Facts

Magnesium acts as a phosphorus carrier in plants, and is required for better root formation and thus for better nutrient and water efficiency in plants.

Dig Deeper

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.

Show More Hide

Magnesium nutrition of plants is frequently overlooked and shortages will adversely impact plant growth. Many essential plant functions require adequate Mg supplies, the most visible being magnesium’s role in root formation, chlorophyll and photosynthesis. Mg is required for crops to capture the sun’s energy for growth and reproduction. All crops require magnesium to capture the sun’s energy for growth and production through photosynthesis. Chlorophyll, the green pigment in plants, is the substance through which photosynthesis occurs. Without chlorophyll, plants couldn’t manufacture food.

Magnesium is an essential component of chlorophyll, with each molecule containing 6.7 percent Mg. Magnesium also acts as a phosphorus (P) carrier in plants, which is necessary for cell division and protein formation. So, Mg is essential for phosphate metabolism, plant respiration and the activation of several enzyme systems.

Soils usually contain less Mg than calcium because Mg is not absorbed as tightly by clay and organic matter and is subject to leaching. The supply of available Mg has been and continues to be depleted in some soils, but growers are noticing good responses to fertilization with Mg.

Magnesium’s availability to plants often depends on soil pH. Research has shown that Mg availability to the plant decreases at low pH values. In acidic soils with a pH below about 5.8, excessive hydrogen and aluminum can decrease Mg availability and plant uptake. At high pH values (above 7.4), excessive calcium may greatly increase Mg uptake by plants.

Magnesium is mobile within the plant and easily translocates from older to younger tissues. When deficiencies occur, the older leaves become damaged first, which may include color loss between the leaf veins, beginning at the leaf margins or tips and progressing inward, giving the leaves a striped appearance.

Dig even deeper into Magnesium

Source: Soil Fertility Manual (2006) by the International Plant Nutrition Institute (IPNI) and the Foundation for Agronomic Research (FAR).

Deficiency Symptoms

Symptoms of deficiency can vary across crop species, but similarities exist for how nutrient insufficiency impacts plant tissue color and appearance. Nutrient deficiencies are commonly associated with the physical location on the plant (i.e., whether the symptoms are primarily observed on older versus newly formed plant tissue), but these symptoms can spread as the severity of the deficiency progresses.

All photos are provided courtesy of the International Plant Nutrition Institute (IPNI) and its IPNI Crop Nutrient Deficiency Image Collection. The photos above are a sample of a greater collection, which provides a comprehensive sampling of hundreds of classic cases of crop deficiency from research plots and farm fields located around the world. For access to the full collection, you can visit IPNI's website.