~ 1956 ~ International Journal of Chemical Studies 2019; 7(4): 1956-1958 P-ISSN: 2349–8528 E-ISSN: 2321–4902 IJCS 2019; 7(4): 1956-1958 © 2019 IJCS Received: 01-05-2019 Accepted: 03-06-2019 Rovit Kumar M.Sc. Department of Agricultural Meteorology, N. D. University of Agriculture & Technology Kumarganj, Ayodhya Utter Pradesh, India AK Singh Assoc. Prof. Department of Agricultural Meteorology, N. D. University of Agriculture & Technology Kumarganj, Ayodhya Utter Pradesh, India AN Mishra Assitt. Prof. Department of Agricultural Meteorology, N. D. University of Agriculture & Technology Kumarganj, Ayodhya Utter Pradesh, India Gajendra Singh M. Sc. Department of Agricultural Meteorology, N. D. University of Agriculture & Technology Kumarganj, Ayodhya Utter Pradesh, India Manoj Kumar Department of Agricultural Meteorology, N. D. University of Agriculture & Technology Kumarganj, Ayodhya, Utter Pradesh, India Correspondence Rovit Kumar M.Sc. Department of Agricultural Meteorology, N. D. University of Agriculture & Technology Kumarganj, Ayodhya Utter Pradesh, India Studies on accumulated thermal unit and thermal use efficiency at different phenophases of rice varieties under different crop growing environment Rovit Kumar, AK Singh, AN Mishra, Gajendra Singh and Manoj Kumar Abstract A field experiment was conducted during kharif season of 2018 entitled “Studies on accumulated thermal unit and thermal use efficiency at different phenophases of rice varieties under different crop growing environment” at N.D. University of Agriculture and Technology, Kumarganj, Ayodhya (U.P.). The experiment consisted of nine treatment combinations viz. three crop growing environment viz. July 15 th , July 25 th and August 04 th and three varieties viz., NDR-97, NDR-2064 and BPT-5204. Results reveal that maximum accumulated thermal unit (2203.1 ° C days) was recorded in crop growing environment of July 15 th followed by the July 25 th (2089.8 ° C days). Among the varieties, maximum accumulated thermal unit in variety BPT-5204 (2367.2 ° C days) followed by NDR-2064 (2113.7 ° C days). Maximum thermal use efficiency of (0.51g/m 2 / ° C days) was recorded in July 15 th at Physiological Maturity followed by July 25 th (0.475g/m 2 / ° C days). NDR-2064 possess maximum TUE of 0.535g/m 2 / ° C days at Physiological Maturity followed by BPT-5204 (0.505g/m 2 / ° C days). Keywords: Thermal unit, thermal use efficiency, growing environment, rice Introduction Rice is one of the most important cereal crop belong to the family Poaceae. It is the staple food for half of the world’s population. Among the crop production tools, proper time of transplanting is the prerequisites that allow the crop to complete its life phase timely and successfully under a specific agro-ecology. In rice, the optimum leaf areas for seedlings, optimum leaf shapes to maximize photosynthetic efficiency, deep, well developed root systems, leaf area index (LAI) at flowering and crop growth rate (CGR) during panicle initiation have been identified as the major determinants of yield. Growth and grain yield reductions have been widely observed when traditionally flooded rice fields were subjected to water saving irrigation measures, where a continuous flood water layer is avoided. Rice is very much sensitive to photo thermal regimes and the crop growth is influenced largely by the growing environmental conditions. Among them temperature plays a significant role in physiological, chemical and biological processes of plants. It is an important environmental factor influencing the growth and development of crops. During growth and development of a cereal, several growth stages are distinguishable in which important physiological processes occur. Influence of temperature on phenology and yield of crop plants can be studied under field condition through accumulated heat units. Plants have a definite temperature requirement for attainment of certain phenological stages. The duration of each phenophase determines the accumulation and partitioning of dry matter in different parts as well as crop responses to environmental and external factors. The occurrence of different phenological events during crop growth period in relation to temperature can be estimated by using accumulated heat units or growing degree days (GDD). Growing degree days are based on the concept that the real time to attain a phenological stage is linearly related to temperature in the range between mean temperature and base temperature. A degree day or heat unit is the departure from the mean daily temperature above the minimum threshold temperature. The heat unit concept assumes that a direct and linear relationship between growth and temperature is advantageous for the assessment of yield potential of a crop in different weather conditions. Keeping above facts in view present investigation was under taken.