Experiments were conducted at the Bangladesh Agricultural University (BAU), Mymensingh (Latitude 24°75′ N, Longitude 90°5′ E, Altitude 18 m), during three consecutive soybean growing seasons namely: rabi 2004-05, kharif II 2005 and rabi 2005-06. The rabi and kharif II seasons generally extend from November to March and from July to October, respectively. The site belongs to the Sonatola Soil Series under the Old Brahmaputra Floodplain Agro-ecological Zone (AEZ 9) with Non-calcareous Dark Grey Floodplain soil. The soil was loam in texture having pH 6.84. The soil contained low organic matter (1.50%), total nitrogen (0.073%), extractractable phosphorus (12.0 mg kg-1), sulphur (9.5 mg kg-1), zinc (0.47 mg kg-1) and medium amount of potassium (0.18%). The soil test result also showed that the amount of P, K, S and Zn were relatively higher in kharif-II season than those in Rabi seasons while the amount of total nitrogen was higher in Rabi season than in kharif-II season. The long-term mean monthly temperature (1983-2003) shows that the temperature in November is 23.9°C but drops to 18.1°C in January and reaches to 24.7°C in March. The temperature in August attains to 29.0°C and then declines to 27.2°C in October. The long-term average total monthly rainfall during November to February was practically zero but slight rainfall occurs in March and April. The rainfall in July is 42.58 cm and that decreases to 19.83 cm in October. Two soybean varieties viz., Bangladesh soybean-4 (G-2) and Shohag (PB-1) and six planting densities viz., 20, 40, 60, 80, 100 and 120 plants m-2 were included in the trial with a split plot design: varieties were assigned to main plot and plant density into the subplots with three replications. Unit plot size was 4.4x3.0 m. An equidistant square planting pattern having spacing 22.4x22.4 cm; 15.8x15.8 cm; 12.9x12.9 cm; 11.2x11.2 cm; 10.0x10.0 cm and 9.1x9.1 cm, respectively were used to create target plant densities of 20, 40, 60, 80, 100 and 120 plants m-2. Seed sowing was done on 6 January, 28 July and 3 December 2005, respectively for rabi 2004-05, kharif 2005 and rabi 2005-06 growing seasons by manually placing three seeds per hill at 2-3 cm depth. Prior to sowing, seed was inoculated with Rhizobium inoculum collected from Bangladesh Institute of Nuclear Agriculture. Each unit plot was uniformly fertilized during final land preparation at 23-69-60-16-1 kg ha-1 N-P2O5-K2O-S-Zn through urea, triple super phosphate, muriate of potash, gypsum and zinc sulphate. Different intercultural operations such as weeding, thinning, gap filling and irrigation were done as and when needed. For example, weeding was done at 20 and 40 DAS in Rabi 2004-05, 20 and 30 DAS in Kharif-II 2005 and 21, 34 and 50 DAS in Rabi 2005-06 seasons followed by thinning to maintain a single seedling at each hill as per experimental specification. Gap filling was done at 42 DAS in Rabi 2004-05 and 35 DAS in Rabi 2005-06 seasons with the additional seedlings of same age raised in a corner of the experimental field and the irrigation was applied at the same day. In Kharif-II 2005 season, gap filling was done twice, first at 30 DAS and second at 37 DAS. In Rabi 2005-06 season, second irrigation was given at 65 DAS because the soil moisture deficit of a plot reached about 50% of the field capacity. The crop was infested by hairy caterpillar in all the three seasons. The rate of infestation was higher in Kharif-II season than Rabi seasons. The hairy caterpillar was successfully controlled with the application of Dimethion 40 EC at 1.5 L ha-1 at 65 DAS in Rabi 2004-05, 28, 44 and 56 DAS in Kharif-II 2005 and 61 DAS in Rabi 2005-06 seasons. There was no disease infection in the crop field. The crop was harvested at full maturity from the central 6.36 m2 area (2.52x2.52 m) of each plot. In Rabi 2004-05, both the varieties were harvested on 20 April 2005, in Kharif-II 2005, variety G-2 and PB-1 were harvested on 27 October and 14 November 2005, respectively while in Rabi 2005-06, harvesting was done on 1 and 9 April 2006 respectively for variety G-2 and PB-1. After threshing, cleaning and drying, the weight of seed of each plot was recorded at dry weight basis.Data on Leaf Area Index (LAI), Leaf Area Duration (LAD), Total Dry Matter (TDM) and Crop Growth Rate (CGR) were recorded by taking plant samples from randomly selected 0.20 m2 quadrats in each plot at 10 and 15 day intervals, respectively for Rabi and Kharif-II seasons starting at 30 DAS (excluding border plants and plants of four central rows). Leaf area of the sample plants was measured using a leaf area meter (LI-3000) and LAI was calculated using following equation below. LAD was also calculated by integrating the leaf area index over time.