Bangladesh Agron. J. 2021, 24(2): 115-125 EFFECT OF SUNFLOWER CROP RESIDUE ON WEED SUPPRESSION IN DIRECT-SEEDED AUS RICE UNDER RICE – SUNFLOWER-RICE CROPPING PATTERN L. Khatun1, T. Chakrobarty1, M.A. Zaman1, M. Nasim1 and S. Mondal1, 2* 1 Bangladesh Rice Research Institute, Gazipur-1701. Bangladesh 2Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur-1706, Bangladesh *Corresponding E-mail: satyen1981@gmail.com (Received: 30 November 2021, Accepted: 17 December 2021) Keywords: Allelopathy, direct-seeded rice, sunflower residue, system productivity, weed, yield Abstract In Bangladesh direct-seeded Aus rice is a conventional rice cultivation practice and weed infestation is a severe problem in direct-seeded rice production due to the existence of favorable environment during this period. So, by minimizing the use of herbicides and replace them with eco-friendly and environmentally sustainable herbicides based on natural plant products or allelochemicals, a factorial experiment based on randomized complete block design with three replications was performed at the research field of Bangladesh Rice Research Institute (BRRI), Gazipur, Bangladesh from July 2018 to August 2019 to evaluate effect of sunflower crop residue on weeds growth and yield of direct seeded Aus rice in Transplanting Aman-Sunflower-Aus cropping pattern. Weed population and weed dry weight were significantly affected by crop residues treatment. Weed population was significantly lower in C3 (Direct sowing of Aus after 7 days of Sunflower residue incorporation) treatment than the control C1 (Direct sowing of Aus without Sunflower residue incorporation) treatment. The lowest weed dry weight (90.5 g m-2) was also obtained from C4 (Direct sowing of Aus after 14 days of Sunflower residue incorporation). The highest reduction of grain yield was obtained from without crop residue and no weeding treatments. The highest number of effective tillers m-2 (403.33), grain panicle-1 (114.67), tillers hill-1 (16.36), and grain yield (3.32 t ha-1) were observed from the treatments where sunflower residue was incorporated and the plots that were weed free. Results of this study indicate that sunflower residues showed potentiality to inhibit weed growth and it has a significant effect on the yield and yield parameters of direct seeded rice. Again weeds played a significant role in the reduction of yield of direct seeded rice. Thus, sunflower residues might be substitute for weed management practice as well as obtaining higher yield of direct seeded rice. Introduction Bangladesh has three rice growing seasons: Aus, Aman and Boro which cover about 9.6, 48.82 and 41.58% of total rice area and these contribute to 7.63, 38.62 and 53.74% of the total rice production respectively (BBS, 2019). Boro is the most important and single largest crop in Bangladesh in respect of volume of production. Due to higher weed infestation problem, farmers don’t like to cultivate Aus rice specially direct seeded Aus rice. Seasonal variation was also observed in the yield losses caused by weeds, with estimated rice yield losses dueto weeds at 70-80%, 30-40% and 22-36% in Aus rice, Transplanted Aman rice and Boro rice, respectively (Mamun, 1990). Yield loss in direct seeded rice is about 40-100% (Mazid et al., 2001; Ahmed and Chauhan, 2014; Mondal et al., 2020). With a substantial yield loss due to weed in direct seeded Aus rice, manual weeding is becoming less effective because of labor crisis at critical times and mailto:satyen1981@gmail.com 116 Khatun et al. increased labor costs. Due to labor scarcity and lack of proper technologies, chemical weed control is becoming popular than hand weeding (Ahmed et al., 2011; Hasanuzzaman et al., 2008). Chauhan et al. (2015) was found that even after the application of pre and post-emergence herbicides, it was not enough to achieve adequate weed control in direct seeded rice. To overcome the problems related to herbicides, use of allelopathic strategies is an alternative way in weed management for sustainable agriculture (Narwal, 1997).The application of the allelopathic properties of some crops (e.g. sunflower) has been suggested for weed management due to the possibility of reducing the application of expensive, pollutant synthetic herbicides (Belz, 2007; Kruse et al., 2000). As a tool for biological weed control in crop production, allelopathy may be natural technique (Cheema and Khaliq, 2000; Heidarzadeh et al., 2010). Even in alley cropping system direct seeded Aus rice is a good practice to uphold rice yield, minimizing weed infestation and soil health improvement through incorporation of pruning materials (Mondal et al., 2013). Considering the above point of view, the present study was conducted to determine the allelopathic and residual potential of sunflower towards weeds and yield performance of direct seeded rice. Materials and Methods The experiment was carried out at the research farm of Bangladesh Rice Research Institute (BRRI), Gazipur, Bangladesh in medium high land during July 2018 to August 2019 (Aman-2018 to Aus 2019). The experimental field belongs to the Agro-Ecological Zone -28 (Madhupur Tract). Soil texture was clay loam. The experiment was executed in factorial randomized complete block design with three replications. The treatments were: Factor A: Time of crop residue incorporation: C1: Direct sowing of Aus without Sunflower residue incorporation, C2: Direct sowing of Aus immediately after Sunflower residue incorporation, C3: Direct sowing of Aus after 7 days of Sunflower residue incorporation and C4: Direct sowing of Aus after 14 days of Sunflower residue incorporation and Factor B: Weeding: W1: Weeding and W2: No Weeding. The experiment was conducted under T. Aman (var. BRRI dhan71)-Sunflower- DS (direct seeded) Aus (var. BRRI dhan83) cropping pattern to determine the effect of sunflower residue incorporation on weed scenario in direct seeded Aus rice and the system productivity of the following pattern. The seed of Aman rice was sown in the first week of July 2018 and twenty-five days old seedlings of TransplantingAmanrice var. BRRI dhan71 were transplanted on using 2-3 seedlings hill-1 at a spacing of 20 × 20 cm and harvested at last week of November 2018. Sunflower var.BARI Sunflower-2 were sown at a depth of 1 cm in December 2018. Seeds were planted with inter-row and interplant spacing of 50 and 25 cm, respectively. A basal dose of 180 urea, 160 triple super phosphates, 150muriate of potash and 150 kgha-1was applied in each plot. Plots were irrigated as per necessary for sunflower. After 90 days of sowing, mature sunflower plants were decapitated. Remaining vegetative parts were uprooted, chopped into 3-5 cm to incorporate in the soil by ploughing in the recommended plot as per treatment. Direct seeded Aus rice var. BRRI dan83 (growth duration 103 days) was selected. Seeds were sown continuously by maintaining 20 cm line to line distance according to the treatment at three dates (29 March 2019, 4 April 2019 and 11 April, 2019) and after sowing irrigation were ensured for germinating the seed. The recommended dose of chemical fertilizers was: 150 urea, 52 triple super phosphate and 75 kgha-1 muriate of potash. Growth and yield attributes of rice In case of T. Aman rice the crop cut area was 6 m2 for grain yield measurement and 4 hills from three different place (4 hills × 3=12 hills) of the plot were taken for obtaining yield attributing characters of Effect of Sunflower Crop Residue on Weed Suppression in Direct-Seeded Aus Rice 117 rice. The data were recorded on grain weight (kg), straw weight (kg), moisture percentage (%), tiller number hill-1, panicle number hill-1, grain panicle-1, unfilled spikelet panicle-1, thousand grain weight (g). In Aus season data on weed parameters at 40 and 55 days after sowing the rice and alsorecorded on grain weight (kg), moisture percentage (%), tiller number hill-1, effective tiller m-2 and filled spikelet panicle-1. Biological yield was calculated by using following formula. Biological yield= Grain yield + straw yield. Growth and yield attributes of sunflower Plant height (cm), stem diameter (cm), capitulum diameter (cm), number of seeds per capitulum, thousand seed weight and total seed weight (kg) of the plot were recorded. Weed density and dry matter production Weed samples were collected from prefixed location of 1 m × 1m area in each plot. Collected weeds were separated into grass, sedge and broadleaf and were expressed in number m-2. After counting the weeds were firstly dried in shade for removing extra moisture and then oven dried at 70 °C for 48 h and weighed (g). Statistical Analysis All data were statisticallyanalyzed through STAR (Statistical Tools for Agricultural Research) statistical package and treatment means were compared by LSD test at 5% level of significance. Results Yield and yield component of Aman rice (BRRI dhan71) There was no significant difference among the treatments in case of tiller, panicle number hill-1 filled spikelets and 1000- grain weight. Table 1. Effect of weeding and crop residue of sunflower on yield component of Aman rice, BRRI dhan71 Crop residue of sunflower Weeding (W1) No weeding (W2) Tiller no. hill-1 Panicle no.hill-1 Filled spikelets panicle-1 (no. Thousand grain wt. (g) Tiller no. hill-1 Panicle no.hill-1 Filled spikeletspanicle-1 (no.) Thousand grain wt. (g) C1 9.58 8.01 87.19 24.08 9.00 8.25 86.03 24.22 C2 10.33 9.58 83.82 24.04 10.55 9.75 87.09 23.87 C3 12.00 11.67 86.58 24.23 11.89 10.02 84.73 24.17 C4 13.01 12.23 87.18 24.05 12.33 11.11 86.37 24.25 LSD(0.05) NS NS NS NS NS NS NS NS CV (%) 1.70 1.47 4.79 0.83 1.70 1.47 4.79 0.83 NS=Not significant Grain yield and Biological Yield of BRRI dhan71 Grain yield and biological yield of BRRI dhan71 showed insignificant difference among the treatments. On an average BRRI dhan71 gave similar yield and biological yield in all the treatments (Fig.1). 118 Khatun et al. Fig. 1. Variation in grain yield and biological yield influenced by sunflower crop residue and weeding. Yield and yield component of sunflower There was no significant difference in case of plant height among the treatments. Stem diameter showed statistically significant difference among the treatments. The highest stem diameter (2.38 cm) was recorded in C1W2 followed by C4W1 (2.28 cm) treatment and the lowest value in C4W2 (1.33 cm) followed by C3W2 (1.51 cm) treatment (Table 2). Maximum capitulum diameter (22.67 cm) was found in C1W2 treatment followed by C2W1 (20.67 cm) and C4W1 (19.67 cm) and minimum capitulum diameter (8.00 cm) was recordedin C4W2 treatment (Table 2). Maximumnumber of seeds per capitulum (546.67) was found in C4W1 treatment followed by C1W2 (520.00), C2W1 (446.67) and C2W2 (446.6) where minimumnumber of seeds per capitulum (246.67) was in C1W2 followed by C4W2 (313.33) treatment (Table 2). Maximum value of thousand seeds weight(67.33 g) was found in C4W1 followed by C3W2 (65.66 g) and C4W2 (65.00 g) and minimum thousand seeds weight(67.33 g) was registered in C3W1 (62.33 g) followed by C1W2 (62.66 g) (Table 2). The maximumseed yield was found in C1W2 (2.43 tha-1) treatment followed by C4W1 (2.32 tha-1) and C2W1 (2.14 tha-1) and lowest yield (1.46 tha-1) was recorded in C2W2 treatment (Table 2).Maximum yield of sunflower (2.43 t ha-1) was observed in C1W2 treatment followed by C4W1 (2.32 t ha-1) and C2W1 (2.14 t ha-1) treatments. Minimum yield (1.46) was in C2W2 followed by C4W2 (1.68 t ha-1) treatment (Table 2). Table 2. Effect of weeding and crop residue of sunflower on yield and yield componentof sunflower Crop residue of sunflower Weeding (W1) No weeding (W2) Plant height (cm) Stem diameter (cm) Capitulum diameter (cm) No.of seeds per capitulum 1000- seed wt.(g) Seed yield (tha-1) Plant height (cm) Stem diameter (cm) Capitulum diameter (cm) No. of seeds per capitulum 1000- seed wt. (g) Seed yield (tha-1) C1 105.00 1.78 13.33 246.67 63.00 1.75 116 2.38 22.67 520.00 62.66 2.43 C2 113.00 1.85 20.67 466.67 64.33 2.14 113 2.11 14.33 446.6 63.66 1.46 C3 119.33 2.03 15.00 396.00 62.33 1.75 116 1.51 10.33 396.67 65.66 1.97 C4 103.33 2.28 19.67 546.67 67.33 2.32 127 1.33 8.00 b 313.33 65.00 1.68 0 5 10 15 20 25 30 GrainYield (t ha-1) Biological yield(t ha- 1) GrainYield (t ha-1) Biological yield (t ha-1) Weeding (W1) No weeding (W2) Y ie ld ( th a -1 ) C1 C2 C3 C4 Effect of Sunflower Crop Residue on Weed Suppression in Direct-Seeded Aus Rice 119 LSD(0.05) NS 0.56 6.18 167.23 NS 0.51 NS 0.56 6.18 167.23 NS 0.51 CV (%) 9.12 6.12 10.45 9.45 3.73 9.26 9.12 6.12 10.45 9.45 3.73 9.26 NS=Not significant Weed scenario The experimental field was infested with the naturally occurring weed community including grass, broad leaved and sedge weeds. The weed composition of the plots is presented in Table 4. The most dominant weed species (on the basis of density) encountered in the weedy plots at 40DAS. Number of grasses differed significantly among the treatments. The highest number of grasses (45.33 and 65.00 m- 2) was observed in the treatments where no sunflower residue was incorporated (C1W1 and C1W2 respectively) and lowest number of grasses (13.67 and 23.33 m-2) was recorded in the treatment where Aus rice was sown 7 days after the incorporation of sunflower residue (C3W1 and C3W2 respectively) (Table 3). The highest number of sedges m-2 was registered in C2W1 (254), C4W1 (250) and C4W2 (398) which were statistically different from other treatments and the lowest number of sedges m-2 in C1W1 (215) treatment followed by C3W1 (226) and C3W2 (230) treatments (Table 3). The highest number of broadleaved weed m-2 was found in C1W2 (20.67) treatment followed by C1W1 (20.33) and the lowest in C3W1 (10.00) (Table 3).There is no significant difference of dry weight and fresh weight of weeds among the treatments.The effect of crop residue on fresh weight and dry weight of weeds in Rice- Sunflower-Rice cropping pattern was statistically significant. Incorporation of sunflower residue significantly reduced fresh weight and dry weight of weeds. The highest value (660.01 g m-2) of fresh weight of weeds was registered in C1 treatment and the lowest (535.03 g m-2) value was in C4 treatments. The highest value (205.02 g m-2) of dry weight was recorded in C1 treatment which was statistically different from others and the lowest value (125.33 g m-2) was in C4 treatment (Fig. 2). Table 3. Effect of sunflower crop residue on the growth, plant population and dry matte production of weeds Crop Residue Weeding (W1) No weeding (W2) No. of grass m-2 No. of sedge m- 2 No. of broadleaf m-2 fresh wt. of weed (g m-2) Dry wt. of weed (g m-2) No. of grass m- 2 No. of sedge m-2 No. of broad Leaf (m-2) fresh wt. of weed (g m-2) Dry wt. of weed (g m-2) C1 45.33 215.00 20.33 590.02 180.01 65.00 273 20.67 730.12 230.03 C2 31.67 254.00 13.67 570.23 170.06 41.00 319 14. 67 710.20 190.05 C3 13. 67 226.00 10.00 440.32 100.05 23.33 230 14.00 630.11 180.15 C4 24.33 250 .00 11.33 400.04 90.50 36.67 398 16.00 670.02 160.21 LSD(0.05) 3.78 14.48 3.10 54.80 23.80 3.78 14.48 3.10 54.80 23.80 CV (%) 6.15 3.50 11.72 10.56 11.78 6.15 3.50 11.72 10.56 11.78 120 Khatun et al. Fig. 2. Effect of sunflower crop residue on fesh and dry weight of weeds in Rice-Sunflower-Rice cropping pattern. Yield and Yield parameters of Aus rice in Rice-Sunflower-Rice cropping pattern Sunflower residue incorporation at different time in combination with the weeding treatments was no significant effect on plant height at harvest. (Table 4). Data presented in Table 1 revealed that there were no significant effects on effective tiller m-2 among the treatments combination. There was no significant difference among the treatments in case of number of tillers hill-1(Table 4). Grains per panicle showed insignificant different among the treatments. Maximum number of Filled spikeletspanicle-1(114.67) was observed in C2W1 followed by C3W1 (113.67) treatment and minimum number of filled grains panicle-1(114.67) was found in C1W2 (75.33) treatment (Table 4).There was no significant difference among various treatments combination (Table 4). Table 4. Yield and yield parameters of Aus rice (var. BRRI dhan83) in Rice-Sunflower-Rice cropping Pattern Crop residue of sunflower Weeding (W1) No weeding (W2) plant height (cm) Effective tiller m-2 (no.) Tillers hill-1 (no.) Filled spikelets panicle-1 (no.) Grain yield (tha-1) Plant height (cm) Effective tillers m-2 (no.) Tillers hill-1 (no.) Filled spikelets panicle-1 (no.) Grain yield (tha-1) C1 99.00 385.00 13.67 105.00 2.75 97.67 262.33 4.67 75.33 1.72 C2 103.67 403.33 16.33 114.67 3.21 98.33 269.67 5.67 93.67 2.39 C3 104.00 394.00 15.67 113.67 3.32 98.67 316.33 6.00 86.67 2.26 C4 102.67 267.83 13.33 102.33 3.00 99.33 265.33 4.33 88.33 1.99 LSD(0.05) NS 73.79 2.03 6.78 0.21 NS 73.79 2.03 6.78 0.21 CV (%) 5.05 9.16 8.33 7.95 9.53 5.05 9.16 8.33 7.95 9.53 NS=Not significant Effect of crop residue on filled spikeletspanicle-1andgrain yield (t ha-1)of Aus Rice Crop residue incorporation of sunflower had significant effect on filled spikelets panicle-1 and grain yield (t ha-1) of Aus rice. The highest filled spikeletspanicle-1 (104.17) was observed in the treatment where Aus rice was sown immediately after the incorporation of sunflower residue (C2) which was 660.07 640.22 535.22 535.03 205.02 180.01 140.1 125.33 0 100 200 300 400 500 600 700 C1 C2 C3 C4 F re sh a n d d ry w e ig h t o f w e e d s (g m -2 ) Sunflower crop residue Fresh weight of weeds (gm-2) Dry weight of weeds (gm-2) Effect of Sunflower Crop Residue on Weed Suppression in Direct-Seeded Aus Rice 121 statistically identical with the treatment where Aus rice was sown seven days after the incorporation of sunflower residue (C3) and lowest value (90.17) was noted where no residue was incorporated (Fig. 2). Grain yield of rice was significantly influenced by crop residue incorporation of sunflower at different time. The highest grain yield (2.80 t ha-1) was found in (C2) which was statistically similar with the treatment C3 (1.79 t ha-1). The lowest grain yield (2.23 t ha-1) was noted in the treatment (C1) where no residue was incorporated (Fig. 3).Effective tillers m-2, tillers hill-1, filled spikelets panicle-1 and yield (t ha-1) of Aus were significantly affected by weed management practices. The highest value of effective tillers m-2 (362.54), tillers hill-1 (14.75), filled spikelets panicle-1 (108.92) and yield (3.07 t ha-1) of Aus was found in weeding plot and lowest was in no weeding plot (Fig. 4). Fig. 3. Effect of crop residue on filled spikelets panicle-1 and yield of Aus rice in Rice-Sunflower-Rice cropping pattern. Fig. 4. Effect of weeding on effective tillers m-2, tillers hill-1, filled spikelets panicle-1 and yield of Aus in Rice-Sunflower-Rice cropping pattern. Rice equivalent yield (REY) of the cropping patterns 90.17 104.17 100.17 95.33 2.23 2.8 2.79 2.49 0 10 20 30 40 50 60 70 80 90 100 110 C1 C2 C3 C4 F il le d s p ik e le ts p a n ic le -1 Sunflower crop residue Filled spikelets panicle-1 yield (t ha-1 ) 362.54 14.75 108.92 3.07 278.42 5.17 86 2.09 0 50 100 150 200 250 300 350 400 Effective tiller m-2 Tiller hill-1 Filled spikelets panicle-1 yield (t ha-1 ) G ro w th p a ra m e tr s a n d y ie ld a tt ri b u te s Weeding Weeding (W1) No weeding (W2) 122 Khatun et al. There was no significant difference in REY among the treatments. The highest REY was registered in C4W1 (19.31 t ha-1) followed by C2W1 (18.78 t ha-1) and C1W2 (18.65 t ha-1) treatments and the lowest in C2W2 (14.83 t ha-1) treatment (Table 5). Table 5. Rice equivalent yield(t ha-1) of Rice-Sunflower-Rice cropping pattern Crop residue of sunflower Weeding (W1) No weeding (W2) C1 16.51 18.65 C2 18.78 14.83 C3 16.88 16.86 C4 19.31 15.32 LSD(0.05) NS NS CV (%) 12.05 12.05 Discussion Among the sunflower residue treatments, the significantly higher number of weeds (grass and broadleaf) was recorded in the plots (45.33 and 20.33 m-2 respectively) which were not treated with sunflower residue incorporation and the lowest value of weeds (grass and broadleaf) in C3W1 (10.00 m- 2) and C3W2 (14.00 m-2) treatment where Aus seeds were directly sown after seven days of sunflower residue incorporation. There was significant reduction of weed number in sunflower residue incorporated plot. This might be due to inhibition of weed growth by allelopathic effect of sunflower residue. Sunflower rhizosphere soil reduces the seedling growth (population, plant height) and yield attributes (seed and biomass) of P. hysterophorus and Trianthemaportulacastrum weeds in pot experiments. The effect of such soil was due to the presence of allelochemicals (p-hydroxybenzoic acid, vanillic acid, caffic acid, ferulic acid) released by sunflower roots in soil (Rawat et al., 2011). Sarkeret al. (2020) also found the highest weed population (9.67 m-2) with no sunflower crop residues and the lowest weed population (1.67 m-2) was found in the treatments where 2.0 t ha-1 of sunflower crop residues was used in transplanted Aman rice and also reported that application of sunflower residues reduce weed. Allelopathic effects of sunflower on other crops and weeds are well established in the literature (Mahmood et al., 2013). Again the effect of crop residue on fresh weight and dry weight of weeds was significant. The highest value of fresh weight (660.01 g m-2) was found in C1 (Direct sowing of T. Aus without Sunflower residue incorporation) and dry weight (205.02 g m-2) was found in C1 treatment and lowest value of fresh weight (535.03 g m-2) and dry weight (125.33 g m-2) was in C4 (Direct sowing of T. Aus after 14 days of Sunflower residue incorporation ) treatment followed by C3 (Direct sowing of T. Aus after 7 days of Sunflower residue incorporation) treatment. Similar trend in weed dry weight was observed by Sahoo et al. (2020). They reported that significantly lower weed dry weight was recorded in the sunflower residue incorporation plot (69.7 g m-2) which was lesser than sunflower residue removal (71.1 g m-2) and control (73.6 g m-2) at 40 days after sowing/transplanting. Maximum plant height (104.0 cm) of Aus rice was found in C3W1 treatment followed by C2W1 (103.67 cm) andC4W1 (102.67 cm) while shortest (99.0 cm) was found in C1W1 treatment (control) followed by C1W2 (97.67 cm),C2W2 (98.33 cm),C3W2 ( 98.67 cm) and C4W2 (99.33 cm). The highest number of effective tiller m-2 (403.33) was registered in C2W1 treatment followed by C3W1 (394.00) and C1W1 (385.00) treatments. The lowest number of effective tiller m-2 (262.33) in C1W2 treatment followed by C4W2 (265.33) treatments. Islam et al., (2018) reported the lowest number of effective tiller hill–1 due to the severe crop weed competition in the weedy treatment whereas, the highest number was found in weed free treatment because of no crop-weed competition in T. Aman rice. The highest number of panicles m-2 (305.00) was recorded from weed free plots by manual weeding in transplanted rice (Tanu et al. 2020). Maximum number of tiller hill-1 (16.36) was found in Effect of Sunflower Crop Residue on Weed Suppression in Direct-Seeded Aus Rice 123 weed free treatment (C2W1) followed by C3W1 (15.67). The highest number of tiller hill-1 may be due to the reduction of inter species competition between crop and weed thus facilitated efficient utilization of resources viz., sunlight, nutrient and moisture to produce effective tillers. The lowest tiller hill-1 (4.33) was in weed containing treatment (C4W2) followed by C1W2 (4.67) treatment. Again the highest number of filled spikelets panicle-1 (114.67) was observed in C2W1 followed by C3W1 (113.67) treatment and minimum number of filled spikelets panicle-1 (75.33) was found in C1W2 treatment. The reason for higher plant height, more number of Effective tiller m-2 and filled spikelets panicle-1 in the weed free treatments might be due to the fact that there was lower weed-crop competition in terms of dry matter production of weeds as well as good source sink relationship which allowed the crop to absorb the required amount of nutrient, water and sunlight for its growth, production of panicles m-2 and grains panicle-1. The highest number of grains panicle-1 (120.78) was recorded in weed-free treatment and Weedy check treatment gave the lowest no. of grains panicle-1 (78.85) in transplanted rice by Tanu et al. (2020). These results are also the substantiating with the results of Acharya and Bhattacharya (2013). The highest yield (3.32 t ha-1) was observed in C3W1 treatment followed by C2W1 (3.21 t ha-1) treatment and lowest yield was recorded in C1W2 (1.72 t ha-1) treatment followed by C4W2 (1.99 t ha-1) treatment. From the yield data it was observed that in all cases maximum yield was observed in weed free condition and the lowest was in weed containing treatments. Crop residue incorporation of sunflower had significant effect on filled spikelets panicle-1 and yield (t ha-1) of Aus rice. The highest filled spikelets panicle-1 (104.17) and yield (2.80 t ha-1) of Aus rice was observed in C2 (direct sowing of T. Aus immediately after Sunflower residue incorporation) treatment and lowest was in C1 (Direct sowing of T. Aus without Sunflower residue incorporation) treatment. Sarker et al. (2020) also found maximum number of grains panicle-1 (141.7) by using sunflower crop residues at 2.0 t ha-1 in transplanted Aman rice and the lowest number of grains panicle-1 (66.83) was produced by no crops residues treatment. The highest numbers of tillers hill-1, numbers of grains panicle-1, 1000-grain weight, grain yield and straw yield were observed where wheat crop residues were incorporated @ 2.0 t ha-1 (Ferdousi et al., 2017). Effective tiller m-2, tiller hill-1, filled spikelets panicle-1 and yield (t ha-1) of Aus were significantly affected by weed management practices. The highest value of effective tiller m-2 (362.54), tiller hill-1 (14.75), filled spikelets panicle-1 (108.92) and yield (3.07 t ha-1) of Aus was found in weeding plot and lowest was in no weeding plot. Bhurer et al. (2013) reported that weed control treatments significantly increased the number of paniclesm-2, panicle weight, filled grains/panicle and thousand grain weight. Conclusion Results of the present study reveal that application of sunflower residue reduces weed infestation and it has positive effect on yield and yield attributes of rice. 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