A field experiment was carried out during kharif, 2015 in the Instructional cum Research (ICR) Farm of Assam Agricultural University, Jorhat, Assam (at a latitude of 260 47' N, longitude of 940 12' E and altitude of 87 m above mean sea level) with two cultivars of rice viz. Luit and TTB-404 grown in different micro climatic regimes created by manipulating the sowing as well as transplanting dates. Both the cultivars were sown on four different dates at fifteen days interval starting from 26 June, 2015 upto 10 August, 2015 following field layout factorial RBD. Agroclimatic indices viz., Growing Degree Day (GDD), Heliothermal Unit (HTU), Phenothermal Index (PTI) and Heat Use Efficiency (HUE) for attaining different phenological stages in both the cultivars were studied. Accumulated GDD at physiological maturity in different dates of sowing were relatively higher in TTB404which varied from to , while in Luit it varied from to delay in sowing date, GDD accumulation till physiological maturity decreases in both the cultivars. Comparatively, in cv. Luit higher grain yield was recorded in the crop sown on D2 (11 July) and D3 (26 July), while in TTB-404 it was recorded in D2 (11 July) and yield in both the cultivars declines gradually with crop transplanted beyond first fortnight of August. Furthermore, the grain yield of both the cultivars was significantly correlated with accumulated GDD and HTU during transplanting to maximum tillering stage with correlation coefficients (r) ** and * respectively. | Agrometeorological indices in relation to phenology and yield of rice genotype (Oryza sativa L.) under upper Brahmaputra valley zone of Assam, India
