Received: 15th April, 2024; Accepted: 30th May, 2024

Abstract

Field experiments (Kharif 2021 and Rabi 2021-2022) were conducted on a deep black clayey vertisol at the ICAR-Indian Institute of Rice Research farm in Hyderabad to identify efficient rice genotypes for their use of soil N (no external application) and response to applied N (100 kg N/ha) and to improve NUE using urease inhibitors (UIs). Twenty-one popular high-yielding genotypes were tested under two nitrogen levels: N0 (no nitrogen) and N100 (100 kg N/ha). Significant differences were observed among the genotypes in terms of grain yield and various nitrogen use efficiency indices, including agronomic efficiency (AE), physiological efficiency (PE), recovery efficiency (RE), internal efficiency (IE), partial factor productivity (PFP), N requirement (NR), and nitrogen harvest index (NHI). Based on the grain yield data and NUE indices, the top-performing genotypes were Varadhan, Rasi, PSV 181, MTU 1010 and PUP 221 during the wet season, while KRH 4, PSV 181, PSV 344, PSV 190, and PUP 221 excelled during the dry season. Notably, PSV 181 and PUP 221 consistently ranked among the top 5 genotypes in both seasons. Additionally, the application of two urease inhibitors (NBPT and allicin) resulted in a significant increase in grain yield while reducing nitrogen levels by 15-20%