Fe and Zn Metal Nanocitrates as Plant Nutrients through Soil Application

Nanocitrates of iron (Fe) and zinc (Zn) in the form of plant nanonutrients were examined for their behavior in soil and the uptake of these by 20-day old groundnut (Arachis hypogaea) seedlings under greenhouse conditions. The Fe (0.04 to 0.008 mmol/kg of soil) and Zn (0.02 to 0.004 mmol/kg of soil) nanocitrates were applied to soil and compared with commercial counterparts (FeSO₄, ZnSO₄, nano-Fe, nano-Zn, Fe-EDTA, Zn-EDTA). The combined nanocitrate compositions were also formulated by physical means and characterized. The plant uptake of Fe and Zn was determined through atomic absorption spectrometry (AAS). All the treated plants showed good germination and higher vigor indexes compared to the control treatments. The highest available Fe and Zn soil contents after leaching were 150.5 and 18.9 mg/kg, respectively, in combined nanocitrate compositions, whereas in the control (untreated) soil, the Fe and Zn contents were 6.0 and 0.7 mg/kg, respectively. The plant's Fe content was 0.48 mg/pot for the combined nanocitrate composition, and that of the untreated plant sample was 0.02 mg/pot. The plant's Zn content was 82.3 μg/pot for pure zinc citrate, and the respective untreated-plant Zn content was 2.1 μg/pot. These values are better than those observed for commercial fertilizers. Additionally, no trend in promotional and antagonistic correlations between Fe and Zn in combined nanocitrates was observed in the studied period (20 days in duration). Among the 34 synthesized citrates, six nanocitrates show promising trends for evaluation under field conditions with higher stability.