Assessing the Performance of Drought-Tolerant Rice Varieties under Varied Nitrogen Doses

Abstract

Field experiments were carried out at ICAR- Indian Institute of Rice Research, Hyderabad during the dry season of 2015/16 and 2016/17 to study the influence of nitrogen rates and varieties on yield attributes, yield, nitrogen use efficiency, and economics of puddled direct-sown rice Treatments comprised of four rates of nitrogen- control (no nitrogen), N100 (100 kg N ha-1), N120 (120 kg N ha-1) and N140 (140 kg N ha-1) as main plots and four drought-tolerant rice varieties (V1-DRR Dhan 42; V2-DRR Dhan 44; V3-DRR Dhan 46 and V4-IR 64). The experiment was laid out in split-plot design with 16 treatment combinations and each treatment was replicated thrice. The results of experiments revealed that increasing the N application rate from N0 to N140 increased the yield of all the varieties, but apparent differences between N120 and N140 were not observed.  When compared with DRR Dhan 42 or IR 64, DRR Dhan 44 and 46 accumulated greater shoot biomass, tillers m-2, and higher leaf area. The yield was significantly higher with DRR Dhan 44 closely followed by DRR Dhan 46 than other varieties, reflecting a higher biomass production and harvest index. Grain yield had a positive quadratic relationship with N uptake by grain (r2= 0.97 and r2=0.94). The relationship between total N uptake and grain yield was linear for 2015/16 (r2=0.98) but quadratic positive relationship was observed in 2016/17 (r2=0.93). Grain yield from N140 plots was significantly increased by 39.65% and 41.5% compared to N0 during 2015/16 and 2016/17. Results show that both  DRR Dhan 44 and  DRR Dhan 46  produced higher grain yield,  had higher N uptake from the soil  in grain and straw and  exhibited higher  NUE  compared to DRR Dhan 42 and IR 64 at all the   N  rates  (0,  100, 120 or  140  kg  ha−1). Agronomic efficiency (ANUE) and recovery efficiency (RE) was higher with DRR Dhan 44 and DRR Dhan 46 and both can be called as nitrogen economising varieties. However, with increasing the N rates, use efficiency of applied nitrogen declined. Also, DRR Dhan 44 was found to be remunerative during both the years and recorded higher net returns and Benefit:Cost ratio. DRR Dhan 44 can be recommended as a suitable variety for the Telangana zone, adapted to drought-prone situations during the dry season.