Enrichment of fertilizers with zinc: An excellent investment for humanity and crop production in India.

Micronutrient malnutrition is a growing concern in the developing world, resulting in diverse health and social problems, such as mental retardations, impairments of the immune system and overall poor health. In recent years, the zinc (Zn) deficiency problem has received increasing attention and appears to be the most serious micronutrient deficiency together with vitamin A deficiency. Zinc deficiency is particularly widespread among children and represents a major cause of child death in the world. In countries where Zn deficiency is well documented as an important public health problem, cereal-based foods are the predominant source of daily calorie and protein intake. Because the concentration of Zn in cereal crops is inherently very low, growing cereals on potentially Zn-deficient soils further decreases grain Zn concentrations. It is, therefore, not surprising that high Zn deficiency incidence in humans occurs predominantly on areas where soils are deficient in plant-available Zn, as shown in many Southeast Asian countries. India has some of the most Zn-deficient soils in the world. Nearly 50% of cultivated soils in India are low in plant-available Zn; these soils are under intensive cultivation of wheat and rice with no or little application of Zn fertilizers. Consequently, cereal crops grown on such Zn-deficient soils contribute only marginally to daily Zn intake. In the rural areas of India, rice and wheat contributes nearly 75% of the daily calorie intake. These facts clearly point to an urgent need for improved Zn concentration of cereal grains in India. Recent calculations indicate that biofortification (enrichment) of rice and wheat grain with Zn, for example by breeding, may save lives of up to 48,000 children in India annually. Breeding new cereal genotypes for high grain Zn concentration is the most realistic and cost-effective strategy to address the problem. However, this strategy is a long-term one, and the size of plant-available Zn pools in soils may greatly affect the capacity of Zn-efficient (biofortified) cultivars to take up Zn and accumulate it in grains. Therefore, application of Zn-containing fertilizers represents a quick and effective approach to biofortifying cereal grains with Zn, thus being an excellent complementary tool to the breeding strategy for successful biofortification of cereals with Zn. Increasing evidence is available from field trials showing that soil and/or foliar application of Zn fertilizers improves grain Zn concentration up to 2- or 3-fold. In the countries where Zn deficiency is both a public health issue and an important soil constraint to crop production, like in India, enrichment of widely applied fertilizers with Zn would be an excellent investment for improving grain Zn while contributing to increased crop production. Recent work by the scientists of the Indian Agricultural Research Institute indicates that the use of Zn-enriched urea in rice and wheat significantly improves both grain Zn concentration and grain yield. It is obvious that enrichment of widely applied fertilizers with Zn and/or foliar application of Zn fertilizers appear to be a high priority with the strongest potential to alleviate Zn deficiency-related problems in India. A Government action and policy plan for enrichment of selected major fertilizers with Zn is required urgently.