BRRI prilled urea applicator was designed and developed to facilitate deep placement of regular urea. Experiments were conducted to evaluate the performance of BRRI prilled urea applicator in the farmers' fields at Gosaidanga in Shailkupa upazila under Jhenaidah district and at Rashidpur in Mithapukur upazila under Rangpur district during Boro 2015 season. Three treatments: hand broadcasting of urea (recommended dose) (HB), BRRI prilled urea applicator (70% of the recommended dose) (PUA) and BRRI USG applicator (70% of the recommended dose) (USGA) were compared in the experiments. The experiment was laid out in randomized complete block design (RCBD) and replicated in four farmers' plots in each location using BRRI dhan28 as test crop both the locations. Prior to field experiment, prilled urea applicator was calibrated and urea dispensed was set to 14 gm in one revolution of drive wheel for Boro season. The field capacity of the PUA and USGA was almost similar (0.09-0.10 ha hr -1 ) in both the locations. Field efficiency of PUA and USGA had 64-65 and 68-69 percent, respectively. PUA and USGA saved 29-32 percent urea fertilizer compared to HB whereas labour requirement of HB (3.74-4.04 man-hr ha -1 ) in three splits showed similar to single application of urea by PUA (3.68-4.00 man-hr ha -1 ) and USGA (3.78-3.97 man-hr ha -1 ). Urea application cost in HB, PUA and USGA was Tk 4,624, 3,424 and 3,483 per hectare in both the locations. Prilled urea application method reduced the production cost. Urea application methods showed insignificant effect on grain yield. BRRI prilled urea safely dispensed urea fertilizer in subsurface, increased the efficacy of urea fertilizer and saved urea fertilizer without sacrificing grain yield. BRRI prilled urea applicator could be a viable technology in rice cultivation. Extensive dissemination works should be undertaken in different agro-ecological zones for wide spread adoption of the applicator.

Air borne particulate matter (PM) samples (both PM 10 and PM 2.5 ) were collected simultaneously from continuous air quality monitoring station (CAMS) at Rajshahi city from

Bi2Mn4O10 was synthesized from corresponding metal salts in glycerin by using an organic precursor-based glycerin nitrate method. The precursor was heated at various temperatures (300 – 800 °C) for about 18 hours to determine the lowest synthesis temperature for the formation of Bi2Mn4O10. The XRD patterns of the calcined samples revealed that the desired mullite type phase started to form at 600 °C, which became more crystalline with further increase of calcination temperature. Attempts were also taken to prepare chromium and cobalt incorporated solid solution series with nominal composition Bi2MxMn4-xO10 (M = Cr3+ and Co3+) by the same procedure. The XRD data of these series exhibited mullite type single phase up to x = 0.7 and 0.1 compositions for chromium and cobalt, respectively. For further insertion of M, an extra phase appeared along with the mullite type phase. J. Bangladesh Acad. Sci. 45(1); 13-26: June 2021

Mechanical intervention in crop production is increasing rapidly in Bangladesh. Researchers are finding ways to manage weeds in rice field using suitable mechanical devices instead of conventional hand weeding. A study was conducted to evaluate the field performance of BRRI (Bangladesh Rice Research Institute) power weeder compared to BRRI weeder and hand weeding in the farmers' field at Rashidpur in Mithapukur upazila under Rangpur district during boro season of 2014-15. Three treatments: T 1 = BRRI weeder (BW), T 2 = BRRI power weeder (BPW) and T 3 = Hand weeding (HW) were used in the experiment. The experiment was carried out in a randomized complete block design (RCBD) and replicated in four farmers' plots. Rice variety BRRI dhan28 was selected for the experiment. The effective field capacity of BW and BPW was found to be 0.06 and 0.09 ha hr -1 , respectively. The weeding efficiency was the highest in HW (92%), followed by BPW (78%) and BW (73%). It was found that BW damaged the lowest number of plants (9%) compared to BPW (11%) during weeding operation, although the damaged plants recovered after a few days. BW and BPW reduced 74 and 85% of labor requirement in weeding operation compared to HW. The highest weeding cost was involved in HW (Tk. 4287 ha ). Weed control methods exerted insignificant effect on grain yield. BRRI power weeder and BRRI weeder reduced weeding cost, enhanced weed control and improved the labor efficiency without sacrificing grain yield. The highest BCR was obtained in BPW (1.22) followed by BW (1.16) and HW (1.11). BRRI power weeder and BRRI weeder appeared to be economic, easy and also environmentally safe weed control device in low land rice cultivation.

Diamine-mono-dithiocarbamates are mono-basic bidentate ligand forming stable complexes with transition metals. Mixed ligand catecholato-bis (diamine-mono-dithiocarbamato) vanadium (IV) complexes were synthesized and characterized using FT-IR, UV-visible and 1 H-NMR spectroscopic techniques. The formation of vanadium complexes was confirmed by the disappearance of υ S-H band in the complexes which was present in the ligands and incidence of υ V-S and υ V-O band in FT-IR spectra of the complexes. The mono-dithiocarbamate with one uncoordinated υ NH/NH2 group was indicated by the presence of υ N-H vibrational band in both the ligands and complexes. In the 1 H-NMR spectra, the peak for -SH proton of ligands disappeared in the complexes suggest the formation of [VL 2 Cat] complex. Non-electrolytic nature of the synthesized complexes was established by their low molar conductance values. The +4 oxidation state of vanadium was confirmed by the electronic spectra of the complexes. On the basis of all physico-chemical data, a six-coordinated octahedral structure has been suggested for catecholato-bis (diamine-mono-dithiocarbamato) vanadium (IV) complexes.