A Multifunctional Nano Fe-NPK Fertiliser: Synthesis, Characterisation, and Applications in Plant Growth

Abstract

Iron is a critical micronutrient that supports photosynthesis, respiration, enzyme activity, and nucleic acid synthesis in plants, yet its bioavailability in soils is often limited. Nanotechnology provides new opportunities to address this challenge by enabling controlled nutrient delivery and improved uptake efficiency. Building on advances in metallo-agriculture, this study evaluates the agronomic performance of a hybrid nano Fe-NPK fertiliser previously synthesised through the thermal reaction of calcium phosphate, potassium chloride, and urea with nano-iron produced via chemical reduction of FeSO₄·7H₂O using NaBH₄. The nanofertiliser, characterised by AAS, EDX, XRD, FTIR, UV–Vis, and SEM, exhibits an N:P:K:Fe ratio of 1:2:1:2 and a core–shell nano-architecture containing both zero-valent and oxide phases of iron. In this application study, the nano Fe-NPK formulation was applied to maize (Zea mays L.) seedlings for 21 days to assess its functional performance. Treated plants demonstrated enhanced chlorophyll production, accelerated shoot and root growth, and greater biomass accumulation relative to the untreated control. Leaf length in treated plants increased by approximately 33% relative to the control by day 21, and potassium uptake reached 0.48 mg/kg compared with 0.36 mg/kg in the control group. These improvements are attributed to increased iron bioavailability and improved uptake of N, P, and K facilitated by the nanoscale size and controlled-release behaviour of the formulation. Overall, the results highlight the potential of hybrid nano Fe-NPK fertiliser to improve early-stage crop development, improve nutrient use efficiency, and support sustainable agricultural productivity.