Abstract

A field experiment was conducted with rice variety RNR 15048 at Experimental Farm, M. S. Swaminathan School of Agriculture, Centurion University of Technology & Management, Paralakhemundi, Gajapati district, Odisha to evaluate heat efficacy of the crop transplanted under four dates (29th July, 7th, 17th and 27th August, 2021) with three age of seedlings (35, 25 and 15 days) during Kharif season of 2021. The heat units, i.e., Growing-degree days (GDD), Photothermal Units (PTU) and Heliothermal Units (HTU) were computed at different crop phenological stages. Accumulated values of GDD, PTU, HTU and growth parameters (CGR and NAR) were always higher on 29th July transplanted crop compared to others. Among different seedling ages, transplanting 25 days aged seedling recorded higher heat units and growth rates than over-aged (35days) and younger (15days) seedlings throughout the crop growth. CGR and NAR were significantly influenced by the transplanting dates (D) and the age of seedlings (A) while the interaction between D x A was found to be non-significant. The heat units (GDD, PTU and HTU) were found to be significantly positively correlated with CGR, TDM and grain yield at different crop growth stages, where r values were found to be highly significant during panicle initiation to flowering (60 to 90 days) and flowering to maturity stages (90 days to harvest). Heat use efficiency (HUE) for grain and straw yields were higher with 29th July transplanted crop as well as with use of 25 days old seedling. It is concluded that transplanting of RNR 15048 rice variety on 29th July using seedlings of 25 days enables efficient utilization of weather parameters such as sunlight and heat (in terms of temperature) in different phenological stages (seedling to final harvest) through a higher accumulated GDD, PTU, HTU as well as HUE values that would result in better crop growth and yield.