Effect of slow release urea sources and nitrogen levels on growth and productivity of rice (Oryza sativa L.)

A field experiment was conducted at ICAR-Indian Institute of Rice Research, Rajendranagar, Hyderabad, during the kharif seasons of 2023 and 2024 to evaluate the effect of slow-release urea sources and nitrogen levels on growth and productivity of rice (Oryza sativa L.). The study was laid out in a randomized block design with sixteen treatments and three replications, comprising five urease inhibitor-coated urea sources neem-coated urea, allicin-coated urea (2000 ppm), eucalyptus-coated urea (2000 ppm), NBPT coated urea (1000 ppm), and cedar wood oil coated urea (2000 ppm) applied at 100%, 75%, and 50% of the recommended nitrogen dose, along with a control. Results revealed that 100% RDN through CWO coated urea produced the highest number of tillers (355 m⁻²), dry matter accumulation (13,319 kg ha⁻¹), and leaf area (765 cm² hill⁻¹), resulting in the maximum grain yield (6641 kg ha⁻¹) and straw yield (8139 kg ha⁻¹), followed by 100% RDN through NBPT-coated urea (6348 and 7956 kg ha⁻¹, respectively). Notably, 75% RDN through CWO coated urea achieved a grain yield of 6363 kg ha⁻¹, statistically comparable to full-dose applications of other coated urea sources, indicating a potential nitrogen saving of 25% without a yield penalty. The findings confirm that slow-release urea sources, particularly those coated with CWO and NBPT, significantly enhance nitrogen use efficiency and sustain higher rice productivity under irrigated conditions.