Abstract:
Indigenous land races of soybean has shown promising yield potential, yet limited information are available for leaf area and related parameters. The present study aimed at assessing the leaf area, leaf area index (LAI), specific leaf area (SLA), specific leaf weight (SLW) and crop growth rate (CGR) of three indigenous land races (Kulat brown, Kulat white, Mothi) and two improved varieties (NARC-II, Swat-84) of soybean planted at monthly interval from April to July during 2004 and 2005 growing seasons. The parameters studied were significantly affected by planting dates, varieties and planting dates x varieties. Specific leaf area and crop growth rate at seed filling stage did not respond to the interaction. Maximum leaf area (2735 m2
plant-1), leaf area index (11), and specific leaf area (391.6 cm2 g-1) was recorded for April planted crop.
Gradual decrease in these parameters was observed when planting was delayed from April to July. However specific leaf weight increased from 2.7 to 10.1 mg cm-1, when planting was extended from April to June. Maximum CGR in early vegetative (1.11 mg g-1day-1), bloom (22.8 mg g-1day-1) and seed fill (6.5 mg g-1day-1) stages was recorded for July, May and April planted crops respectively. Maximum leaf area (2165 cm2
), LAI (8.3), and SLA (225 cm2 g-1) was recorded for Kulat brown. Swat-84 demonstrated maximum SLW (7.4 mg cm-1). Land races exhibited greater leaf area (1871 cm2 ), LAI (7.1) and SLA (214.7 cm2 g-1). At early vegetative, bloom and seed fill stages, maximum CGR was recorded for Swat-84 (0.97 mg g-1day-1), Mothi (19.9 mg g-1day-1) and Kulat brown (5.3 mg g-1day-1) respectively. Land races exhibited higher CGR
than improved varieties except at early vegetative growth stage. The average CGR at initial vegetative stage, bloom and seed fill stage were 0.81, 17.7 and 4.6 mg g-1day-1 respectively. The average CGR for April, May, June and July planted crop was 7.5, 8.9, 7.8 and 6.2 mg g-1day-1.
