Abstract
Two field experiments were conducted to find out the optimum planting period for Indian rice hybrids during wet season (WS) of 2000 and dry season (DS) of 2001 at Uttar Banga Krishi Viswavidyalaya, Pundibari, West Bengal, India. Average cultivar growing degree days (GDD) to attain four leaf (4L), panicle initiation (Pl), flowering (F), and maturity (M) stages were 394, 1112, 1749, and 2326, respectively, in 2000 WS; which were greater than mean values for 2001 DS. The planting of 5 August increased the grain yield by 38.8 and 12.2% over 5 and 20 July plantings, respectively, in 2000 WS. However, delay in planting from 15 to 28 February during 2001 DS reduced the yield by 0.73 t ha-1. Hybrid PA 6201 (5.72 t ha-1) appeared promising for WS, while CORH 2 (6.42 t ha-1), CNHR 3 (6.42 t ha-1), and KRH 2 (6.40 t ha-1) performed better in DS. Positive correlations between grain yield and GDD or summed bright sunshine hours were evident during 4L to PI on 20 July (P < 0.01) and 5 August (P < 0.05) plantings. All rice hybrids had >75% brown rice recovery, >1.3% elongation ratio, >75% carbohydrate, and >7.5% protein content.
