Effect of plant density and nano-urea-based nitrogen management on physiological growth and nitrogen use efficiency of sweet corn

Optimizing plant density and nitrogen management is essential for improving physiological performance and nitrogen use efficiency in sweet corn (Zea mays L. saccharata). A field experiment was conducted during the summer seasons of 2024 and 2025 to evaluate the effects of plant density and nano-urea-based nitrogen management on physiological growth parameters and nitrogen use efficiency of sweet corn. The experiment was laid out in a split-plot design with three plant densities (60 × 20 cm, 50 × 20 cm and 45 × 20 cm) as main-plot treatments and six nitrogen management practices, including conventional prilled urea and reduced nitrogen levels supplemented with nano-urea or prilled urea sprays, as sub-plot treatments. Results showed that plant density significantly influenced crop physiological behaviour; closer spacing (45 × 20 cm) enhanced crop growth rate at later stages and increased nitrogen uptake, apparent nitrogen recovery and partial factor productivity due to higher biomass production, while wider spacing recorded higher absolute growth rate and net assimilation rate, indicating better individual plant efficiency. Relative growth rate was higher under wider spacing at the initial stage but shifted towards closer spacing at later stages. Among nitrogen management practices, application of 75% nitrogen through prilled urea supplemented with nano-urea improved physiological growth parameters, nitrogen uptake, apparent nitrogen recovery and agronomic nitrogen use efficiency over 100% recommended nitrogen, while partial factor productivity was highest under 50% nitrogen supplemented with nano-urea. The study demonstrates that integrating optimum plant density with nano-urea-based nitrogen management enhances physiological efficiency and nitrogen utilization in sweet corn.