Magnesium |
Magnesium is required for crops to
capture the sun's energy for growth and production. Chlorophyll, the
green pigment in plants, is the site where photosynthesis
occurs without chlorophyll plants could not manufacture food.
Magnesium
is an essential component of the chlorophyll molecule, with each
molecule containing 6.7 percent magnesium. Its functions
include phosphate metabolism, plant respiration, and activation of
enzyme systems. Availability of Mg is often related to soil
pH. Other situations also increase needs for Mg: sandy soils with low cation exchange capacity, low Mg-supplying power, and a high Mg
leaching potential; application of calcitic limestone on low Mg soils;
crops with high Mg requirements; high application rates of ammonium-N
and K; soil test levels below 50 to 100 lb/A exchangeable Mg.
Plant Deficiency SymptomsMagnesium is taken up by the plant as the divalent cation, Mg++. It is mobile within the plant and easily translocated from older to younger tissues. When deficiencies occur, the older leaves are affected first. The deficiency symptoms may include the following: (1) loss of color between the leaf veins, beginning at the leaf margins or tips and progressing inward. This can give the leaves a striped appearance. (2) Leaves may become brittle and cup or curve upward and they may become thinner than normal. (3) Tips and edges of leaves may become reddish-purple in cases of severe deficiency (especially with cotton). (4) Low leaf Mg can lead to lowered photosynthesis and overall crop stunting.
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