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Iodine in agriculture


Iodine has an important physiological function in marine seaweeds and algae species. It takes part in physiochemical pathways that prevent damage after oxidative stress caused by desiccation or exposure to light. In terrestrial crops such as lettuce or tomato, addition of iodine in plant nutrition has shown to increase the amount of antioxidant secondary plant compounds, making plants more resilient to drought or salinity stress. Adding iodine to fertiliser in low amounts can be beneficial for biomass production. The crop can accumulate the iodine in the harvested produce, and this has the added benefit of increasing the amount of iodine in the human and animal diet.


Additions of iodine, in the form of potassium iodate, to irrigation water have been used to eliminate iodine deficiency in villages in northwestern China. A single application of iodine to the farmers’ fields corrected iodine deficiencies in villagers consuming the crops grown on these fields for at least four years at a low cost of around USD 0.05 per person per year. Livestock productivity also improved by around 30 percent because livestock in the region had previously been iodine-deficient.


This example is widely used to show the feasibility of iodine supplementation by enrichment of crops with iodine. In recent years progress has been made to further improve the concept. Research has shown that to apply iodine to plants homogenously and more efficiently, the iodine may be included in fertiliser formulations. This approach has resulted in adequate iodine fortification of edible parts of crops when the formulation is applied to the rooting zone of hydroponically and soil-grown vegetables or to above-ground plant parts with foliar sprays. Research has confirmed that iodine in biofortified food is readily bioavailable and assimilated. Importantly, the iodine content in these crops is preserved after common cooking procedures. 


The benefits of iodine-enriched fertilisers are directly related to addressing iodine deficiency as one of the main global human health problems, and to the fundamental role the fertiliser industry plays in growing healthy and nutritious foods for human well-being. Offering iodine-enriched fertilisers may be part of the social responsibility programmes of some fertiliser companies. Studies conducted so far have demonstrated encouraging results in increasing iodine concentrations in food crops. More research is being done to study iodine uptake from iodine-enriched fertilisers in various crops under different cultivation methods and growing conditions in order to market iodine-biofortified foods in a cost-effective manner. 


Currently, agronomic research is implementented to further improve agronomic biofortification with iodine, with funding by international NGO’s such as the Bill and Melinda Gates foundation in the HarvestPlus Biofortification Challenge Program, coordinated by CGIAR (a global agriculture research partnership for a food secure future). CGIAR programmes are carried out by 15 research centres in collaboration with hundreds of partner organizations. The HarvestPlus program is coordinated by two of these centres, the International Centre for Tropical Agriculture (CIAT) and the International Food Policy Research Institute (IFPRI). The international fertilizer industry association (IFA) also works in close partnership with the HarvestPlus Program.

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