Crop specific requirement of growing degree days and agrometeorological indices in rice growing zones

The spatial and temporal distributions of heat unit and various agrometeorological indices for the rice crop, are studied in this paper. Eight ET – stations were selected from six rice growing zones, viz., Canning (in lower Gangetic plains), Bikramganj and Varanasi (in middle Gangetic plains), Ludhiana (in trans Gangetic plains), Ranchi, Shymakhunta (in eastern plateau and hills), Annamalai Nagar (in east coast plains and hill region) and Pattambi (in western plains and ghat region). Eleven crop growth stages were identified for this  study, viz., germination, nursery seedling, transplanting, tillering, active tillering, lag phase, panicle initiation, flowering, grain formation, grain maturity and harvesting, the duration of each of the growth stages varied widely, station wise. Daily data were collected growth stagewise for latest available five years and the mean values were computed for the derived parameters, viz., the crop requirements of heat unit, agroclimatic rainfall index (ARI), yield moisture index (YMI), aridity index (AI). The study revealed that for rice crop the total degree days requirement varied from 1706 degree – days (at Ranchi) to 2815 degree – days (at Shymakhunta). It showed primary peak (with 16.7 % of total requirement) at active tillering stage. The ARI values were mostly higher than 100 per cent. The mean YMI values varied widely from 477 mm (at Bikramganj) to 1523 mm (at Pattambi). The values showed main peak at active tillering stage. The AI values showed moderate aridity at early growth stages, which increased at advanced crop growth stages.