Accumulated heat units requirements for different phenophases of raya (Brassica juncea L.) as influenced by sowing dates

Field experiments were conducted during rabi seasons of 2004–05 and 2005–06 to study the phenology, growing degree-days accumulation and heat use efficiency of raya (Brassjca Juncea). Cultlvar PBR-91 was sown under three dates of sowing viz 5 October, 30 October and 25 November. Different agro climatic indices viz. growing degree days, hello-thermal units and photo-thermal units were computed for different dates of sowing. Early sowing took more number of days to attain physiological maturity than normal and late sowing. The early sown crop accumulated more degree-days, hello-thermal units and photo-thermal units than normal and late sown crop during both the years. The pooled data of 2004–05 and 2005–06 showed a significant relationships between number of days and GDD (R2 =0.87), HTU (R2=0.87) and PTU (R2=0.77).