A field study was conducted at the research field of the Bangladesh Sugarcrop Research Institute farm, Pabna, Bangladesh. The site is located at 24080 North latitude and 890040 East longitude and situated about 15.5 m above the mean sea level. The experimental site represents the High Ganges River Flood Plain soils under the Agro ecological zone-11. Sugarcane variety Isd 37, lentil (Lens culinaris L.) BARI Masur-5 as first intercrop and sesame (Sesamumindicum L.) BARI till-3 as second intercrop were used as test crop. For polybag settlings, the cane stalks were cut into small pieces (5 cm) containing one bud each with at least 1.5 cm stalk on above the node and about 3 cm at below. All setts were treated with Bavistin solution (1:1000) for 30 minutes to prevent fungal infection. The soil for filling polybag (12.5 cm × 10.0 cm) was mixed with cowdung (1:1) and then treated with Chlorpyrifos (Regent 3 GR) @ 0.04 g bag-1 and Carbofuran (Furadan 5G) @ 0.05 g bag-1 to control insect pest in the nursery. About two third of polybag were filled with the mixed soil and a previously treated sett was placed vertically in the centre of soil of the bag keeping the bud in upward direction. Then the polybag was completely filled with the soil so that about 1.5-2.0 cm soil covered the setts. The polybags were kept in a sunny place and thinly covered with rice straw to preserve soil moisture, and also protect soil loss from heavy rain (Ali et al. 1989). Watering was done at 2 days interval to the nursery beds throughout the period before transplantation of the settlings to the main field. Other cultural operations like weeding, rouging of diseased and pest infected settlings were done to maintain healthy settlings. Watering was done on days of transplanting of settlings into the main field.
Experimental design: The experiment was laid out in Randomized Complete Block Design (RCBD) in where each treatment replicated thrice under 2 factors. The unit plot size was 8 m × 6 m. Each plot was separated by 1.0 m border. Total number of unit plots was 24 in the experiment.
Factors A (Spacing of sugarcane and row number of intercrops)
S1 = Sugarcane row to row spacing (RRS) 80 cm + 1 row of lentil followed by 1 row of sesame S2 = Sugarcane RRS 100 cm + 2 rows of lentil followed by 2 rows of sesame S3 = Sugarcane RRS 120 cm + 3 rows of lentil followed by 3 rows of sesame S4 = Sole sugarcane with RRS 100 cm.
Factors B (Leaf cutting of sugarcane) C0 = Non leaf cutting (NLC) C1 = Leaf cutting (LC)
Cultivation and management of crops: The land was prepared by using tractor plough and harrow. To achieve good tilth, about 20 cm deep trenches were made. Row to row distances was maintained 80 cm, 100 cm and 120 cm. For sugarcane Urea, TSP, MOP, Gypsum and ZnSO4 were applied @ 325, 250, 180, 190 and 9kg ha-1, respectively. Full quantity of TSP, Gypsum, ZnSO4 and one-third of MOP were applied in trench and mixed with soil prior to transplanting of settlings. One-third of urea was applied at 21 days after transplanting (DAT). The second dose of (1/3rd) Urea and 1/3rd MOP were applied as first top dressing at 90 DAT. Similarly final dose of Urea and MOP were applied as top dressing at 150 DAT (Anon 2005). For lentil intercrop Urea, TSP and MOP, Gypsum and ZnSO4 were applied @ 20, 50, 20, 30 and 2.5 kg ha-1, respectively. Total amount of Urea, TSP, MOP, Gypsum and ZnSO4 were applied at basal dose at time of sowing (Rahman et al. 2005). For sole lentil Urea, TSP, MOP, Gypsum and ZnSO4 were applied @ 40, 80, 30, 50 and 4.5 kg ha-1, respectively. Total amount of Urea, TSP, MOP, Gypsum and ZnSO4 were applied at basal dose at time of sowing (Rahman et al. 2008). For sesame intercrop Urea, TSP, MOP, Gypsum and ZnSO4 were applied @ 50, 70, 25, 50 and 2 kg ha-1, respectively. Total amount of Urea, TSP and MOP were applied at basal dose at time of sowing. For sole sesame Urea, TSP, MOP, Gypsum and ZnSO4 were applied @ 100, 130, 40, 100 and 3 kg ha-1, respectively. Total amount of Urea, TSP, MOP, Gypsum and ZnSO4 were applied at basal dose at time of sowing (Satter et al. 2005).
Transplanting/Sowing: Previously raised 45 days old polybag sugarcane settlings were transplanted in each plot within 14 November, maintaining 45 cm plant to plant spacing. Lentil was sown as first intercrop sesame was sown as second intercrop. Lentil was shown on 14 November and harvested on 23 February. Sesame was shown on 4 March and harvested on 13 June. The seed rate of lentil and sesame were 15 kg ha-1 and 4 kg ha-1 respectively as intercrops while these were 35 kg ha-1 and 9 kg ha-1 as sole crop. In the main field, irrigation (10 cm) was given in trenches just after transplanting of the settlings for easy establishment. Supplementary irrigation was done at 30, 60, 90 and 120 DAT considering dryness of surface soil. Dead settling were replaced by healthy settlings within 15 days after transplanting. The mulching of the top soil was done after each irrigation. The plots were kept weed free 15 to 135 DAT, as the period is considered to be the critical period for crop-weed competition in sugarcane. Earthing-up and tying of sugarcane were done after 140 days of plantation to protect the cane stalks from lodging or damage by wind during the period from July to September. Pest management and disease controls were done following the recommend of Alam et al. 1990. During trench preparing Chlorpyrifos (Regent 3 GR) was applied in the trenches @ 33 kg ha-1 to control termite and Carbofuran (Furadan 5G) was applied as a preventive measure against borers at 90 and 150 days (two time) after planting @ 40 kg ha-1 for each time.