Optimizing Rapeseed Productivity through Sowing Date Adjustment and Agro-climatic Indices Moderation

Aims: To optimize rapeseed variety TS 67 yield and agroclimatic indices through sowing date adjustment in Assam condition i.e. Eastern Himalayan agroclimatic region. Study Design: Split plot design. Place and Duration of Study: Instructional cum Research Farm, Assam Agricultural University Jorhat, during kharif season of 2022. Methodology: The treatments were laid out in a split plot design with three replications. The treatments comprised of three different sowing dates viz., D1: 15th November, D2: 30th November, D3: 15th December in main plots and four Jasmonic acid concentration JA1 (no JA), JA2 (50 micromole per litre), JA3 (100 micromole per litre), and JA4 (150 micromole per litre). From the study, the growth, physiological parameters, yield attributes, yield and agroclimatic indices were recorded and analyzed. Results: Results revealed that among the different sowing dates, The crop sown on 15th November (D1) required significantly higher number of days to flower initiation (28.50 days), 50% flowering (34.50 days), siliqua formation (34.58 days) and physiological maturity (87.08 days) along with significantly higher accumulated growing degree days (1199.77 0C day), helio-thermal units (7567.22 0C day hours) and photo-thermal units (12766.70 0C day hours). Significantly higher seed yield of 6.66 q ha-1, stover yield of 14.11 q ha-1 and oil yield of 243.62 kg ha-1 were also obtained from the sowing of the crop on 15th November (D1). On the other hand, the crop sown on 15th December (D3) recorded lowest seed as well as stover yield of 4.99 q ha-1 and 12.21q ha-1 respectively. Correlation studies indicate significant interrelationship between agroclimatic indices and plant growth parameters having higher correlation coefficient which indicates that the optimum agroclimatic parameters improves growth and yield of rapeseed. Conclusion: Based on growth, yield and agroclimatic indices, the sowing of the crop on 15th November can be considered best for enhancing the production of rapeseed (Brassica campestris var. toria) under rainfed condition.