Effect of prilled urea and urea super granules on dynamics of ammonia volatilisation and nitrogen use efficiency of rice

The nitrogen use efficiency and volatilisation losses of ammonia in rice were studied following application of prilled urea (PU) and urea super granules (USG) @ 76 and 114 kg N ha⁻¹ in a field experiment on a Typic Haplaquept. Application of USG at 76 kg N ha⁻¹ was adjudged to be the optimum source of fertilizer N for rice. Deep placement of USG significantly improved grain yield, straw yield and nitrogen use efficiency of rice and reduced the volatilisation loss of ammonia relative to the application of prilled urea. Recovery of 15N by the second crop was considerably lower (3.8–6.6%) than that by the first crop (24.2–37.0%) in a rice-rice cropping sequence. The contribution of fertilizer-N towards the volatilisation loss of ammonia was found to be dwindling with the progress of time following the application of 15N tagged urea.