Cultivar response, dry-matter partitioning, and nitrogen-use efficiency in dry direct-seeded rice in Northwest India

Dry-seeded rice (Oryza sativa L.) (DSR) is an emerging production system in the Indo-Gangetic Plains because of increasing constraints of labor, water, and energy availability. Studies on dry-matter partitioning and nitrogen-use efficiency (ANUE) are particularly important for developing high-yielding cultivars for this new production system. We investigated yield, dry-matter partitioning, and NUE of selected cultivars in response to nitrogen (N) application. The experiment, replicated thrice, was laid out in a split-plot design with four N levels (0, 60, 120, and 180 kg ha) as main plots and four cultivars (IR-64, PR-120, PAU-201, and IET-20653) as subplots. At optimum N level (120 kg ha), grain yield was positively correlated with physiological efficiency, agro-physiological efficiency, and filled grains panicle, whereas in zero-N plots these traits did not show any relationship with yield. The study revealed that dry-matter redistribution from leaves and stems contributed significantly to grain yield in DSR. The study suggested that leaf area index and relative water content at flowering, N-uptake efficiency (NUE), and root density could be used as selection criteria for identifying cultivars with high ANUE and productivity under DSR. Results implied that N-use-efficient genotypes (on the basis of N-uptake efficiency %), such as IET-20653, could be used in breeding programs to develop agronomically suitable cultivars with high yield potential for DSR