Eliminating Zinc Deficiency in Rice-Based Systems

Zinc deficiency is a wide-spread and serious problem both in human populations and in crop production. It is a relevant issue in rice-based systems due to their extent and role in human nutrition worldwide. There is an urgent need to increase human Zn intake through biofortification strategies in these systems. Particularly in developing countries, there is a spatial correlation between human Zn deficiency and low Zn soils Main soil factors controlling plant-available Zn are pH, redox condition, organic matter content and concentrations of other trace elements. By far the biggest fraction of total Zn is adsorbed to the soil's solid phase in most soils. This requires management practices that avoid a risk for Zn fertilizer failure and/or a choice of rice cultivars that are able to mobilize Zn adsorbed by the soil's solid phase. Management practices could include balancing Zn with N and P fertilization, seed or follar application of Zn and effective organic matter management. On the plant level the rooting density, the root efflux (exudates) and influx (Zn) and Zn translocation are important factors. The translocation from aboveground vegetative tissues to the grain endosperm seems the most limiting step to reach higher Zn concentrations in grains. Genetic variation in several steps leading to grain Zn loading have been found, but options to align these do not seem to have been fully explored. It probably needs combination of breeding with Zn application treatments to both tackle Zn deficiencies at the crop growth stage and at grain Zn loading stages. The role of N fertilization in creating synergy also needs further investigations. To improve human Zn intake, several strategies can be applied, such as supplementation, dietary diversification and food fortification. Among these, biofortifying rice through breeding or agronomic management is the most sustainable strategy and unlikely to pose any adverse health effects on people. The few case studies available support this conclusion.
Soil, Phosphorus, Rice, Zinc
A. Duffner, E. Hoffland, T.J. Stomph, A. Melse-Boonstra and P. S. Bindraban, 2014.Eliminating Zinc Deficiency in Rice-Based Systems. VFRC Report 2014/2. Virtual Fertilizer Research Center, Washington, D.C. 35 pp.; 1 table; 5 figs.; 1 text box; 200 ref.