The Role of Micronutrients in Crop Production and Human Health

The soils in Pakistan across 22 Mha cultivated area are predominantly alluvial and loessal, alkaline in pH, calcareous and low in organic matter. These factors are mainly responsible for nutrient fixation in soil and low availability to plants. Zinc (Zn) deficiency in Pakistan was the first micronutrient disorder recognised in early 1970s as a cause of hadda disease in rice. After identification of Zn deficiency, extensive research has been carried out during last four decades on micronutrient deficiencies in soils and their drastic effects on crops. Subsequently, field-scale deficiencies of zinc (Zn) boron (B) and iron (Fe) have been established in many field and horticultural crops. The most widespread deficiency is of Zn as 70 % of the soils of Pakistan are Zn deficient and observed in rice, wheat, cotton, maize, sunflower, sugarcane, brassica, potato and in many other crops along with citrus and deciduous fruits. Boron deficiency is another major nutritional disorder which severely affects rice, cotton, wheat, sugarbeet, peanut, citrus and deciduous fruits. The third field-scale disorder is Fe chlorosis which has been exhibited in peanut, chickpea, cotton, citrus, ornamentals and many tree species. Copper (Cu) and manganese (Mn) deficiencies are of localized occurrence. The mineral elements like Zn, Fe and Cu are as crucial for human health as organic compounds such as carbohydrates, fats, protein and vitamins. The daily dietary intake of young adult ranges from 10-60 mg for Fe, 2-3 mg for Cu and 15 mg for Zn. Intake less than these values can cause slow physiological processes. These micronutrients deficiencies in soil are not only hampering the crop productivity but also are deteriorating produce quality. High consumption of cereal based foods with low contents of micronutrients is causing health hazards in humans. The contents of micronutrients in food can be elevated either by supplementation, fortification or by agricultural strategies i.e., biofortification and application of micronutrients containing fertilizers. Food fortification and supplementation are too expensive, not practical to be applied on large scale and not easily accessible to poor masses. The development of micronutrient efficient genotypes can be a successive tool to overcome the micronutrient disorders in soil and for improvement in human health. However, the harvesting of micronutrient enriched grains from field would mine out more micronutrients. The cultivation of these genotypes can be integrated with the application of micronutrients containing fertilizers. Addition of such fertilizers will not only correct the deficiencies but also improve the fruit size and quality of crops. In general, 2-5 kg Zn ha may be adequate for improved crop production, however, soil applied Fe is generally ineffective except for Fe-sequestrine. Repeated sprays of Ferrous sulphate (FeSO4) or chelated Fe cure the chlorosis and improve the quality of food stuff. However, despite being highly cost effective, currently micronutrient use is negligible.