Comparable grain and straw yield of selected BAAP lines and Pakistani rice cultivars under 50% of recommend N application in alkaline calcareous soils of Punjab, Pakistan

Low nitrogen use efficiency due to imbalanced fertilization causes heavy losses of N from agriculture which imparts both economic and environmental consequences. Rice (Oryza sativa L.) genotypes vary in genetic potential to use nitrogen. In order to evaluate the NUE of different rice genotypes, two years screening of 268 rice genotypes (258 BAAP lines and 10 Pakistani cultivars) was done at the University of Agriculture Faisalabad at 50 and 100% of the recommended dose of N. Urea fertilizer was used as a source of N at the rate of 127 kg ha-1. Different parameters such as Plant Height, Grain Weight, Straw Weight, SPAD at 45 DAT and SPAD at 60 DAT and plant N concentration were determined. Categorization of genotypes based on their scores of various parameters into efficient(E), medium(M) and inefficient (I) scoring genotypes and Cluster Analysis of with all parameters was also performed. For grain yield, 27% of genotypes perform better at 50% N versus 100% N. Plant height was greatest for both AUS 175 and Jabahul at 50% and 100% N level during 2022. Dubhi and Kalo Bira both produced highest grain yields at 100% N and 50% N, respectively. BCULARN's Grain Yield was highest at both N levels in 2022. BCULARN also demonstrated highest Grain Yield on average in 2 years at both N levels. In both years, NAIDumur had the highest Straw Weight at both N levels. At both N levels in 2021, the maximum SPAD value was observed for Lakhai at 45 DAT, whereas Asahi and Lakhai had the highest SPAD values at 45 DAT at 50 and 100% of N level, respectively. Punjab Basmati at 50% N level and Moroberekan at 100% N level showed highest SPAD value at 60 DAT in 2021. The highest levels of N for the genotypes Dulaaus (50%) and MINGHUI 63 (100%) were observed. The study revealed encouraging results in terms of maintaining yield of rice genotypes at 50% of the current recommended dose of N for rice crop in Pakistan.