Magnesium deficiency in cotton

MAGNESIUM (Mg) DEFICIENCY has occurred widely in cotton growing areas. Deficiencies occur particularly in highly leached humic acid soils or on sandy soils, which have been given heavy dressing of lime.

In some cases, the deficiency occurs on soils high in potassium (K).

In the presence of higher concentrations of calcium, nitrate, and sulphate and chloride ions in soil restricts the Mg{+2}{++} uptake through ion competition and pose deficiency problems.

Magnesium is mobile in the plant and defiency always begins in the older leaves and then moves to the younger leaves, showing reddish brown leaves with green colour veins.

The leaves sometimes remain fresh without any folding and the colour is yellowish red. Generally the deficiency is seen only when the bolls are formed.

The Mg deficiency can be prevented by the basal application of 25-50 kg MgSO{-4} or spraying of 2 per cent MgSO{-4} during reproductive stage. Or by the spraying of 20g MgSO{-4} + 10 g urea per litre at the interval of 15 days through stet.

P. Janaki and L. Chithra

Department of Soil Science and Agricultural Chemistry TNAU, Coimbatore-641003