Optimizing Nitrogen Use Efficiency and Soil Fertility in Rice through Partial Substitution of Conventional Urea with Nano Urea

Sustainable rice production critically depends on improving nitrogen use efficiency, particularly in Bangladesh where conventional urea application is associated with substantial nitrogen losses through volatilization and leaching. A field experiment was conducted to examine the effect of nano urea with normal urea and recommended doses of other fertilizers (RDF) on the growth, yield, grain quality and post-harvest soil fertility of rice. The experiment had seven treatments which included T0 (Control), T1 (100% RDF), T2 (Only nano urea), T3 (nano urea + rest of RDF excluding urea), T4 (50% urea, 50% nano urea + rest of RDF) and T5 (no urea, no nano urea+rest of RDF) and T6 (Only Urea). The findings demonstrated that integrated nitrogen management with nano urea was markedly more effective for all parameters measured compared to the control. Plant height was significant in T4 which showed better vegetative growth. Grain yield significantly increased from 4.4 t ha⁻¹ in the control to 9.3 t ha⁻¹ in T4; biological yield (31.1 t ha⁻¹) and harvest index (30%, under the same treatment T4, respectively). Mirroring this trend, maximum levels of chlorophyll a (P < 0.01) and chlorophyll b (P < 0.01), as well as total chlorophyll contents (P < 0.01), were found in T4, indicating higher nitrogen assimilation rate and photosynthetic efficiency. Grain quality was also enhanced, and T4 boasted the highest protein content (9.2%) among treatments. Post-harvest soil study also revealed the positive effect of T4 on organic matter (1.53%), total nitrogen (0.20%), available phosphorous (32.71 ppm), and sulphur (12.81 ppm) with a good stability of soil pH at harvest stage as compared to control soil sample. Results suggest that, 50% conventional urea + nano urea + RDF be an effective and sustainable N management strategy for rice to achieve higher crop productivity, grain nutritional quality as well as better soil health while decreasing its dependency on bulk urea fertilizer.