Interactive Effects of Soil-Applied Nitrogen and Foliar Nano-Urea on Growth and Grain Yield of Maize (Zea mays L.)

Abstract

A field experiment was conducted in the spring season of 2025 in Sumer district, Al-Qadisiyah, Iraq, to study the combined effect of soil applied nitrogen and foliar nano nitrogen spray on the growth and grain yield of maize (Zea mays L.). The factorial experiment was laid out in a randomised complete block design with three replications. Three levels of soil nitrogen were tested, namely: N0 (unfertilised control), N1 (50% of the recommended dose) and N2 (100% of the recommended dose).  Four concentrations of foliar nano-nitrogen were applied: F₀ (unsprayed control), F₁ (2 mL L⁻¹), F₂ (4 mL L⁻¹), and F₃ (6 mL L⁻¹). X-ray diffraction, Fourier-transform infrared spectroscopy and field-emission scanning electron microscopy characterised the fertiliser as crystalline urea as the main phase with a mean particle diameter of 38.5 nm. Ten growth and yield traits were measured. Main and interaction effects were significant (P < 0.05) for most traits. The N₂F₂ combination produced the highest plant height (226.8 cm), chlorophyll content (49.6 SPAD), kernels per ear (548), 100-kernel weight (34.7 g), and grain yield (8.62 t ha⁻¹), representing an 82.6% yield increase over the N₀F₀ control (4.72 t ha⁻¹). Raising the spray to 6 mL L⁻¹ gave no significant further gain. N₁F₂ (half the soil nitrogen dose plus 4 mL L⁻¹) gave a grain yield (6.86 t ha⁻¹) statistically equal to that of N₂F₀ (full soil dose without spray, 6.58 t ha⁻¹). Combining soil nitrogen with foliar nano-nitrogen therefore raises maize yield and may reduce soil fertilizer inputs.