Magnesium deficiency causes a yellowing of intermediary or older leaves, beginning between the major veins, that by contrast remain green (interveinal chlorosis). This pattern initially appears at the leaf margins and gradually progresses toward the midrib. If not amended, the interveinal chlorotic areas become whitish and brown patches of necrotic tissues appear at the leaf edges. As the tissues collapse, eventually entire leaves become necrotic and start to shrivel. Fruit yield is reduced due to the damage to the leaves and the consequent loss of productivity. If the deficiency is severe, fruits can also show symptoms of collapse of the apical tissue (apical rot).
Magnesium deficiencies may be found in coarse-textured soils in humid regions, and especially on light, sandy, acidic soils in areas with frequent rainfall. The excess of potassium, ammonium or calcium (heavy liming) in soils can also influence negatively the availability of this nutrient to plants. Symptoms are more likely to show during cold weather or on heavy wet soils, when roots are less active. Magnesium is involved in sugar transport and it is a essential constituent of the chlorophyll molecule. Without sufficient amounts of magnesium, the plants begin to degrade the chlorophyll in the older leaves to transfer it to the newer, developing ones. This explains the development of interveinal chlorosis. Light intensity influences the development of the symptoms. High light worsens the effects of a magnesium deficiency.
Apply substances that contain magnesium such as algal limestone, dolomite or limestone magnesium. Use manure, organic mulches or compost to balance the soil nutrient content. They contain organic matter and many nutrients that are release slowly into the soil.
Use a balanced fertilization program appropriate to the soil and to the crop in question. Incorporate magnesite or dolomite into deficient soils before planting. Magnesium sulphate releases the magnesium over a four to six week period to the soil and is ideal for a slow release requirement. Foliar sprays of magnesium sulphate or of fully soluble magnesium nitrate should also help to amend a deficiency. Foliar sprays may be used as complement in cases where the concentrations of potassium or ammonium in the soil are high. Take care of the specified amounts and right utilization.
Check the pH of the soil and lime if necessary to get the optimal range.,The soil pH should always be above 6.,Plan a good drainage of fields and do not overwater the crop.,Use organic mulch to keep soil moisture stable.,Do not over fertilize with potash or ammonium.