Two experiments were carried out at the experimental farm of Bangladesh Institute of Nuclear Agriculture, Mymensingh, Bangladesh (24° 75´ N and 90° 50´ E) under subtropical condition during the two successive seasons (March-May) of 2013 and 2014. The experimental field was under subtropical climates characterized by heavy rainfall during the months of May to September and scanty rainfall during October to April. The soil of experimental site was sandy loam having a total nitrogen 0.065%, organic matter 1.07%, available phosphorus 18.5 ppm, exchangeable potassium 0.30 meq/100 g, sulphur 20 ppm and pH 6.8. The first experiment comprised of one factor randomized complete block design with three replications. The widely cultivated variety, BINAmung-7 was used as plant material. The debranching levels were: (i) Category 1 [Control, main stem (MS) with 4 branches per plant], (ii) category 2 (MS with three branches per plant), (iii) category 3 (MS with two branches per plant), (iv) category 4 (MS with one branch per plant) and (v) category 5 (only MS). The treatments were imposed when branches initiated and maintained the treatments until harvest. The unit plot size was 3 m × 3 m. To determine optimum spacing for different plant canopy (which developed by different levels of debranching), the second experiment was conducted in 2014. Four different plant spacings (which was determined based on the canopy structure of each treatment) such as 40 cm × 10 cm, 30 cm × 10 cm, 25 cm × 10 cm and 20 cm × 10 cm were maintained for the plant having main stem (MS) with 4 branches, MS with three branches, MS with two branches, MS with one branch and only MS, respectively. Plants were thinned within a line at 20 days after sowing (DAS) to maintain population (25, 25, 30, 40, 50 plants per square meter) according to treatment (Category 1, 2, 3, 4 and 5, respectively). For the first experiment, seeds were sown on 3 March, 2013 in the experimental field with recommended spacing of 30 cm × 10 cm. In the second experiment, seeds were sown on 9 March, 2014 in the experimental field with different spacings. Urea, triple superphosphate, muriate of potash and gypsum were used as sources of nitrogen, phosphorus, potassium and sulphur at the rate of 40, 120, 80 and 30 kg/ha, respectively at the time of final land preparation (BARC 2005). First weeding was done followed by thinning at about 21 DAS. A single irrigation was given at 25 DAS in both years. Insecticide (Ripcord 50 EC, 0.025%) was sprayed at flowering and fruiting stage (55 DAS) to control shoot- and fruit borer. Other intercultural operations were done as and when required. Five plants from each replication of the first experiment were randomly tagged for daily count of opened flowers. Flower count began from the date of opening of the first flower and continued daily until flowering ceased. The second rows from the border of each plot were used for sampling. For determination of total dry matter, the plants were separated into roots, stems, leaves and fruits, and the corresponding dry weight were recorded after oven drying at 80 ± 2ºC for 72 hours. The total dry matter/plant was estimated by summing dry matter of leaves, stem, root and pods dry weight per plant. The leaf area was measured using automatic leaf area meter (Model: LICOR 3000, USA). The canopy area was measured using Ceptometer (Decagon Devices Inc., Pullman, WA, USA) at noon of sunny day at 71 DAS just before harvesting the pods. Harvest index was determined as: (grain yield/plot ÷ biological yield/plot) × 100. Per cent fruit set to opened flowers, reproductive efficiency (RE) was estimated as: % fruit set = (Number of fruits/ plant ÷ number of flowers/plant) × 100. The degree of synchrony/asynchrony in pod maturity was determined as follows: Synchrony: > 90% pod matured; partial synchrony: 80 - 90% pod matured and asynchrony: < 80% pod matured at 1st harvest (Mondal et al. 2011b). At harvest, ten plants from each plot were selected randomly for data recording on total dry mass, reproductive efficiency, yield and yield related traits. Pod yield was measured from each plot excluding border line and converted into kilogram per hectare. The collected data were analyzed statistically following the ANOVA technique and the mean differences among treatments were compared by DMRT using the statistical computer package program, MSTAT-C (Russell 1986).