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In the valley land of North-East Hill (NEH) ecosystems of India, about 70% area under rice (Oryza sativa L.) is transplanted. Physiological attributes and yield performance of aerobic rice over conventional flood-irrigated rice need to be assessed while promoting water saving technology. A field experiment was conducted at the experimental farm, ICAR Research Complex for NEH Region, Umiam (950 m msl), Meghalaya during rainy seasons of 2006 and 2007 under aerobic and flooded conditions with aerobic rice variety collected from IRRI, Philippines. Some important high-yielding varieties (HYVs) recommended for the region were also included in the study. The objectives of this study were (i) to evaluate the influence of frequent mid-season drainage as a measure of water saving technique besides inducing the pre-conditioning effect on genotypes to withstand water stress during the subsequent growth period of crop ontogeny, (ii) to compare crop performance between aerobic and flooded rice management practices, and (iii) to identify attributes responsible for the yield gap between aerobic and flooded rice. The results revealed that the yield difference between aerobic (average yield, 1.67 t/ha) and flooded rice (average yield, 2.31 t/ha) ranged from 18.4 to 37.8% (P < 0.05) depending on varieties, highest difference being observed with rice hybrid DRRH 1. Cultivation of rice under aerobic condition resulted in 27.5% yield reduction over flooded rice. Among the yield components assessed, sink size (spikelets per panicle) contributed more to the yield and is considered to be most important factor responsible for yield gap between aerobic and flooded rice. The study suggests that, variety Sahsarang 1 with its moderate values of photosynthesis rate, transpiration rate and water use efficiency (WUE) along with higher grain yield seems to be better choice for both stress (aerobic) as well as normal (flooded) condition. Aerobic rice varieties with minimum yield gap compared to flooded rice is the key for success of aerobic rice cultivation
