HEAT-UNIT REQUIREMENT FOR PHENOLOGICAL DEVELOPMENT OF WHEAT (TRITICUM-AESTIVUM) UNDER DIFFERENT LEVELS OF IRRIGATION, SEEDING DATE AND FERTILIZER

A field experiment was conducted during winter season of 1992-93 and 1 993-94 at the university farm, Ranchi, to estimate the heat-unit requi rement for phenological development of wheat (Triticum aestivum L. eme nd. Fiori & Paol.) under different irrigation, seeding date and fertil izer levels on sandy-loam soil. Wheat crop irrigated at crown-root ini tiation, maximum tillering, boot and milk stages (4 irrigations) requi red more days for onset, duration and heat units for expression of var ious phenophases, than the crop irrigated either at crown-root initiat ion and boot (2 irrigations) or at crown-root initiation, boot and mil k stages (3 irrigations). Timely seeded (24 November) wheat required 5 , 6, 7, 8, 9. 10 and 10 more days for the onset of nag-leaf emergence, boot, spike emergence, flowering, milk, soft dough and maturity respe ctively than late-sown (is December) crop. However, a fixed amount of heat units was needed to proceed from one phenophase to the other, irr espective of the seeding time. Wheat fertilized with recommended dose (N100P22K21) prolonged the onset and duration of phenophases and conse quently required more heat units than that fertilized with half this d ose.