Lower leaves lose green colour (chlorosis) in the midrib region particularly towards the base. These leaves develop brown rusty spots which unite and form continuous areas. In the case of acute deficiency, the whole leaf turns brown and dry and plant may die. A zinc deficient field gives brown rusty appearance, hence the name Khaira disease. With severe zinc deficiency the stand of rice is uneven in the field.

Application of zinc sulphate to soil is the most satisfactory way to correct zinc deficiency. Foliar spray of zinc sulphate is used to ameliorate zinc deficiency if symptoms appear in standing crop.

Rate of zinc sulphate varies between 25-50 kg per hectare depending on the texture of the soil. In sandy soils a lower dose is selected. Zinc sulphate is applied broadcast and incorporated in top soil with last ploughing or while puddling for transplanted nce.

0.5% zinc sulphate solution is sprayed on zinc deficient crop at least 2-3 times at an interval of 7-10 days. For spraying one hectare crop, dissolve 2.5 kg zinc sulphate and 10 kg urea (or 1.25 kg slaked lime) in 500 litres of water.

Response of rice to zinc sulphate application as measured in all India field experiments show a range of 3 to 7 quintal additional grain per hectare. The degree of response is dependent on the magnitude of zinc deficiency in soil, soil type and crop cuitivar.