Comparison of Morpho-physiological Traits and Yield Attributes in Direct-seeded Aerobic and Conventional Transplanted Rice

Water stress is one of the main environmental stresses responsible for reducing crop productivity. Vital biochemical processes including photosynthesis, respiration, protein synthesis and assimilation of organic nitrogen have been demonstrated to be adversely affected by water stress. Traditionally, rice is grown by transplanting 3-to-5 week old seedlings into puddled fields. But in recent years, direct-seeded aerobic cultivation is being adopted by farmers because of its water saving potential. However, lower grain yield has been recorded in direct-seeded aerobic rice as compared with conventional transplanted crop. The susceptibility of rice crop to water stress varies with the variety, degree, duration of stress and its coincidence with different growth stages. The adverse effect of rice to water stress is more pronounced at reproductive stage and leads to a reduction in yield and yield attributes. Irrigation management strategies under direct-seeded aerobic condition can be developed to reverse the yield decline only after the causes of yield decline are identified. This article reviews the physiological and biochemical basis of yield gaps between rice crop grown under direct-seeded aerobic and conventional transplanted conditions.