Source: http://vasat.icrisat.org/crops/pearl_millet/pm_production/html/m6_3/index.html

Plants need certain other nutrients in addition to primary nutrients.

These nutrients are secondary nutrients and micronutrients. The secondary nutrients are Calcium, Magnesium, and Sulfur. The important micronutrients are Iron, Zinc, Boron, Molybdenum, Manganese, Copper, Chlorine and Cobalt. These nutrients are equally essential for pearl millet plants for proper growth, development and disease resistance. Continued use of only common fertilizers, which do not supply these nutrients, is leading to their deficiencies resulting in reduced pearl millet yields.

Testing the soil will help in identifying the need for the application of these plant nutrients.

Application of organic manures like well decomposed farm yard manure (FYM) and compost, green manuring and green-leaf manuring practices provide most of these plant nutrients.Also, using choice fertilizer material containing one or more of these nutrients could help in supplying such nutrients. For example, applying super phosphate will not only supply phosphorus but also provides calcium and sulfur.

Calcium and sulphur deficiencies may occur in problem soils. In acid soils, calcium application may be required. Similarly sulfur deficiency may occur in alkaline soils.

However, we come across very rarely the deficiency of these secondary nutrients in many pearl millet growing areas . Among the micronutrients, Zinc and Iron are the most commonly deficient in pearl millet growing areas. Zinc deficiency can be corrected by applying Zinc sulfate to the soil before the final ploughing. Zinc application to soils last for several years. So, zinc need to be applied once in 3 to 5 years.

Soil application of ferrous sulfate at the final ploughing is recommended in soils low in available iron.

Foliar application of 0.5-1.0% ferrous sulfate solution corrects iron deficiency if noticed in a standing crop. Soil applications of iron may be long-lasting than foliar application.