The experiment was conducted at the Agronomy Field Laboratory of Patuakhali Science and Technology University (PSTU), Dumki, Patuakhali in high land during the period from July to November, 2018. The experimental site lies at 22o27' N latitude and 90o23' E longitude at an altitude of three-meter above the sea level. The experimental field belongs to the Agro-Ecological Zone-13; Ganges Tidal Floodplain. The texture of the soil was clay loam having pH 6.0, organic matter 1.38%, total N 0.09%, available P 6.30 ppm, exchangeable K 0.11 me/100g, available S 15.25 ppm, and available Zn 0.46 ppm. There were fourteen weed control treatments included in the study. These were as follows: T1 = Weedy check (Unweeded control), T2 = Weed-free check by hand weeding twice (at 20 and 40 DAT), T3 = Pendimethalin (PE), T4 = Pretilachlor (PE), T5 = Butachlor (PE), T6 = Pyrazosulfuron ethyl (Early post-emergence), T7 = Bensulfuron methyl + Acetachlor (PE), T8 = Bispyriback sodium ((Post-emergence), T9 = 2, 4-D amine (PoE), T10 = MCPA (PoE), T11 = Sunflower residues (PE), T12 = Sunflower residues (PE) + 100% Pyrazosulfuron ethyl (Early post- emergence), T13 = Sunflower residues (PE) + 75% Pyrazosulfuron ethyl (Early post-emergence) and T14 = Sunflower residues (PE) + 50% Pyrazosulfuron ethyl (Early post-emergence). Sunflower residues were studied in combination with Pyrazosulfuron ethyl only because many of the farmers of this region use this herbicide for weed control in rice. The experiment was laid out in a randomized complete block design with three replications. The layout was completed one day before transplanting. Spaces of 1m and 0.5 m were maintained in between replication and unit plots, respectively. The individual plot size was 4 m × 2.5 m (10 m2). The variety BRRI dhan49 was used as planting material. Fertilizer was applied @ 90-15-51- 9-1 kg N, P, K, S, and Zn ha-1, respectively through urea, triple super phosphate, muriate of potash, gypsum and zinc sulphate on a soil test basis. Urea was applied in three equal splits; 1st at 15 days after transplanting (DAT), 2nd at 30 DAT and 3rd at 45 DAT. The total amount of triple super phosphate, muriate of potash, gypsum and zinc sulphate was applied during final land preparation. Thirty-two days old uniform seedlings were transplanted on 9 August 2018 at the rate of 2-3 seedlings hill-1 at a spacing of 20 × 20 cm. Liquid/powdery herbicides were sprayed uniformly with the spray volume of 500 L ha-1 for pre- emergence spray and 350 L ha-1 for post-emergence spray using a knapsack sprayer with a flat fan nozzle. The pre-emergence application was made on the soil surface with 5 cm water depth uniformly with minimum trampling. Granular herbicide was broadcast uniformly on the soil surface by mixing with sand. Hand weeding was carried on bund side and paths whenever the weeds emerged in order to keep the experimental site clean. In the weed-free treatment, the plots were kept weed free up to 40 DAT by two hand weeding at 20 and 40 days after transplanting. Weedy plots allowed season long weed infestation. At physiological maturity, heads of sunflower plants were removed and the plants were harvested, air-dried for several days under sun light and chopped into 2-3 cm pieces. Sunflower plants were collected from the farmers’ field of Sreerampur village of Dumki Upazila, Patuakhali. Chopped material was kept under room condition until use. The air-dried and chopped residues were incorporated in soil 3 days after transplanting of Aman rice @ 5 t ha-1. Data on weed density and dry weight were recorded at 45 DAT randomly from 0.25 m2 (0.5 x 0.5 m) area and then converted to per square meter. Dry weights of weeds were taken by drying them in an electric oven at 70oC until the constant weight was recorded. Phyto-toxicity of herbicides on rice plants was determined visually (yellowing leaves, burning leaf tips, stunting growth etc.) according to the scale suggested by IRRI (1999). The rating of toxicity was done within a week (2nd, 4th, and 6th days) of herbicides application from 10 samples of each plot. The mean rate was calculated from 10 sample plants of a unit field plot. The day of recovery from the toxicity was also recorded visually. The degree of toxicity on the rice plants was measured by the following scale. Yield components were recorded from 10 random hills except for the harvest and border area. An area of 5.12 m2 (3.2 m x 1.6 m) was harvested from the centre of each plot to estimate grain and straw yields. After threshing and cleaning, the fresh weight of grain was recorded and adjusted to 14 % moisture content. Straw yield was recorded after proper sun drying. Weed index (WI) was calculated by using the following formula (Misra and Misra, 1997) Weed index (%) = x–y/x 100; Where, x = Yield from weed free plots, y = Yield from treated plots The cost of cultivation of each treatment was worked out. Further the economic evaluation of each treatment was done by estimating the gross returns, net returns and benefit cost ratio. The price of the inputs at the time of their use and the prevailing market price of the products obtained were considered for working out the cost of cultivation, returns, and benefit-cost ratio. The collected data were statistically analyzed using the F-test. Data on weed count and weed dry weight have shown a high degree of variation. Therefore, the data on weed count and weed dry weight were subjected to square-root [(x + 0.5)0.5] transformation to make an analysis of variance more valid as suggested by Chandel (1984). Data were analyzed with STAR 2.0.1 software for analysis of variance and means were compared based on the least significant difference (LSD) test at the 0.05 probability level (Gomez and Gomez, 1984).