Enhancing the accumulation and bioavailability of iron in rice grains via agronomic interventions

Suboptimal or inadequate diet of iron (Fe) represents a latent health problem affecting over two billion people worldwide. To tackle micronutrient deficiency in crops, a short-term approach is agronomic biofortification in which nutrients can be enhanced by their accumulation in food plant tissue either by fertilisation or by other eliciting aspects. The present study evaluated the comparative influence of various Fe application methods, including (i) Fe seed coating (300 mg Fe kg(1) seed), (ii) Fe osmopriming (0.5% Fe solution), (iii) surface broadcasting (8 kg ha(1)), (iv) Fe foliar application (0.3% Fe solution), on paddy yield, net benefits, grain Fe accumulation, bioavailability, and Fe-use efficiencies in conventional (puddled transplanted rice, PTR) and conservational (direct-seeded aerobic rice, DSAR) production systems. Hydro-priming and foliar water spray were also included in treatments as a positive control for osmopriming and foliar spray of Fe respectively. Iron application by either method enhanced productivity, profitability, and biofortification in both rice systems. Grain yield improved in both years by the application of Fe in the following order: osmopriming > foliar application > surface broadcasting > seed coating, with the respective increase of 18%, 14%, 10%, 8% relative to no Fe application. Grain Fe concentration was the highest by Fe applied as foliar (37% over control) in both production systems. Similarly, minimum phytate concentration and phytate:Fe molar ratio were recorded with foliar-applied Fe. In crux, Fe application by osmopriming increased the productivity and profitability under PTR and DSAR systems, whereas foliar-applied Fe improved the grain Fe accumulation.