Agronomic Biofortification of Wheat for Preventing Zinc Malnutrition: Multi-Year, Multi-Location Results from Pakistan.

The alkaline-calcareous soils in Pakistan are conducive to zinc (Zn) deficiency in crop plants. Thus, Zn fertilizer use is recommended for almost all crops, including wheat (Triticum aestivum L.) grown on >8 million ha. The 2002 and 2011 National Nutrition Surveys have revealed human Zn malnutrition of alarming magnitude: 40% children, 48% pregnant women and 41% non-pregnant women are diagnosed to be Zn-deficient. Zinc malnutrition is confined predominantly to resource-poor segments of the society, whose almost entire calorie source is low-Zn staple cereals (around 25 mg kg-1). As expensive measures, like mineral pills and dietary diversification, are hardly affordable by the resource-poor masses, the only feasible option appears to be enhancement of Zn in staple cereals. Cereal grain Zn concentration can be enhanced by developing Zn-efficient varieties, i.e., by genetic biofortification, or by using Zn fertilizer, i.e., by agronomic biofortification. Pakistan is attempting both the approaches. Currently, three Zn-efficient wheat lines (having upto 37 mg Zn kg-1) are undergoing field evaluation. Agronomic biofortification has also proven effective. In 2008–2014 multi-location field trials across rice-wheat, cotton-wheat and mixed cropping systems, Zn fertilizer not only has increased wheat yield by 15–18% (P<0.05), cost-effectively, but also increased grain Zn concentration upto to 52 mg kg-1 (P<0.05). Foliar sprays of Zn proved more effective in enhancing grain Zn. Also, high-Zn grains proved much better as seed for the next crop by improving germination, seedling vigor and yield (P<0.05). Thus, Zn fertilizer use, especially on Zn-efficient cultivars, can play a vital role in preventing Zn malnutrition.