Magnesium (Mg)
Magnesium (Mg) is taken into the plant through the root system as the Mg2+ ion. It is the central ion in the chlorophyll molecule and is therefore critical to the process of photosynthesis.
Magnesium is readily transferred from older tissue to younger tissue under deficiency conditions resulting in deficiency symptoms occurring in the older tissue first. In cotton this is primarily exhibited as an interveinal chlorosis where the main tissue of the leaf begins to turn pale green or purplish red with prominent green veins. The chlorosis begins at the tip and around the margins of the leaf and progresses toward the back of the petiole producing a 'herringbone' appearance.
Most soils across the cotton belt provide sufficient quantities of Mg to sustain proper plant growth and development. Magnesium deficiencies are most common on very light texture soils at low soil pH levels. Symptoms can often be confused with late season maturation of cotton leaves. Liming materials,especially dolomitic limestone, may often contain sufficient Mg to supply cotton's need for Mg.
Images of magnesium deficiency symptoms
