Physiological analyses of nitrogen use efficiency and yield traits of rice genotypes

Nitrogen (N) is a vital element for plant development and growth, and the application of N fertilizer could significantly increase yield formation in rice. One potential approach to reduce N fertilizer application in rice production is the development of varieties with improved nitrogen use efficiency. This study was investigating the genotypic differences of rice in the physiological nitrogen use efficiency and yield traits under different nitrogen levels. The photosynthetic rate was recorded higher (36.91 μmol CO2 m−2 s−1) in the treatment of 150% of recommmended nitrogen with rice genotype CB-08-513 at 50% flowering stage. The higher SPAD meter value (44.23) and leaf thickness (0.87 mm) were recorded in the recommended nitrogen with the genotype of CB-08-513. Regarding nitrogen content, the leaf nitrogen (5.43%) and total nitrogen content (1.86%) was recorded higher in medium duration genotypes under 150% of recommmended Nitrogen level at panicle initiation stage. The Nitrogen Uptake Efficiency (1.73), Physiological Nitrogen Use Efficiency (29.39), Nitrogen Utilization Efficiency (3.17), photosynthetic nitrogen use efficiency (4.74) were lower in medium duration genotypes when treated with 150% of recommmended Nitrogen. The maximum grain yield of 9160 kg ha−1 was registered in medium duration genotype CO 50 under 150% of recommmended Nitrogen with increase of 20.62% over control. However, in short duration genotype CB-08-504 was recorded maximum grain yield of 8449 kg ha−1 under 150% of recommmended Nitrogen with increase of 21.41% compared to 50% of recommmended Nitrogen. © 2018, Indian Society for Plant Physiology.