Growth Stage-Dependent Foliar Application of Iron Improves its Mobilisation Towards Grain and Enhances Fe Use Efficiency in Rice
Foliar application could improve grain iron (Fe) concentration (GFeC) by following 4Rs, i.e., the right Fe compound with right concentration sprayed at the right growth stage with right number of sprays. We studied the Fe mobilisation towards grain and its use efficiency using chelated-Fe and nano-Fe compounds in rice.Various Fe formulations [Fe-citrate, Fe-EDTA, FePO4, nano-Fe oxide, and humic acid with FeCl3 (HA + Fe)] were evaluated for their effect on growth, yield, and Fe mobi lisation in rice. Single spray was done at tillering (set 1), anthesis (set 2), and grain filling (set 3) stages, or sprayed twice at anthesis and grain-filling (set 4) and thrice at all stages (set 5). In all sets, shoot Fe at harvest (SFeH) correlated significantly with grain yield whereas SFeH and GFeC were negatively correlated, indicating that higher Fe in foliage promotes growth but would not necessarily increase grain Fe. A significant correlation between GFe uptake (GFeU) with Fe mobilisation efficiency index revealed that Fe mobilisation from shoot rather than root was the primary contributor to GFeU. Among Fe compounds, HA + Fe application enhanced grain yield and GFeU (> 70%) relative to control in all sets whereas nano-Fe (4 mM) resulted in highest GFeC in sets 4 and 5. Improved yield and Fe mobilisation from shoot towards grain was obtained with a single spray of HA + Fe either at anthesis or grain-filling stage. Thus, foliar Fe regimen has potential to enhance grain mineral quality and alleviate Fe deficiency that have implications for human health.
Biofortification, Foliar nutrition, Use efficiency