67 1. Introduction Onion (Allium Cepa L.) belongs to the family Allia- ceae in the genus Allium (Friensen, et al., 2006; Brewster, 2008). In Nigeria, onion is grown mainly for its bulb which is used in virtually every home on a daily basis to flavour and season a wide variety of dishes. As a constituent of a meal, both the green leaves and bulbs can be eaten raw or cooked in soups and salads. It is claimed to minimize high blood pressure and other heart diseases due to its favour- able action on the elasticity of blood vessels. As an item of world trade, onion ranks second in importance after toma- toes among vegetables in Nigeria, where annual produc- tion stands at 621 000 t, making it the 36th highest pro- ducing country in the world. The genus Allium constitutes “bulb crops” and these are weak competitors with weeds which emerge among the crops (Boydston and Seymour, 2002). Weeds are known to reduce available moisture, nu- trients, sunlight and growing space needed by crop plants. Subsequently, weeds can reduce growth, quality and yield of crops and make harvesting difficult. Onion seedlings are weak competitors with weeds because of their slow growth, small stature, shallow roots and thin canopy. In addition, their cylindrical upright leaves do not shade the soil enough to suppress weed growth. Weed interference was observed to be more devastating than insect (Thrips tabaci) infesta- tions on onion dry bulb yield (Ghosheh and Al-Shannag, 2000). Herbicides may be applied before planting or after planting. Pre-plant application of a soil residual herbicide such as oxadiazon has proved effective for weed control in onion (Amrutkar et al., 2002). Oxyfluorfen and pendi- menthalin were reported to have significantly reduced the weed population and increased onion yield to levels com- parable to yields of weed control in a relay cabbage-onion cropping system (Sanjeev et al., 2003). Onions are sown at densities that exceed 20 plants/m2, and hand weeding operations are practiced with great care. On the other hand, high costs, lack of manpower and low economic returns are currently pushing onion farmers to consider herbicides as an alternative weed management option in onion pro- duction. The reliance on unstructured or non-sequenced weed management programs by farmers, especially in a country like Nigeria where agricultural commodities are still inexpensive, is also very common. Therefore, the ob- jective of this study was to evaluate the efficacy of weed control using single herbicide applications. Although not all the herbicides used in this experiment were registered for onion production, producers might be tempted to use those available and at the lowest cost. 2. Materials and Methods Field experiments were conducted during the 2006/2007 and 2007/2008 dry seasons at the Irrigation Research Sta- tion, Kadawa, of the Institute for Agricultural Research, Screening of herbicides for weed control, growth and yield of irrigated onion (Allium cepa L.) in tropical Savanna climate D.I. Adekpe, J.A.Y. Shebayan, C.P. Shinggu, L. Aliyu * Department of Agonomy, Faculty of Agriculture, Institute for Agricultural Research, Ahmadu Bello University, P.M.B. 1044, Zaria, Nigeria. Key words: herbicides, hoe weeding, onion, weed control. Abstract: Field experiments were conducted during the 2006/2007 and 2007/2008 dry seasons at Sudan Savanna Nigeria to study the effects of herbicides on weeds and growth of irrigated onion (Allium cepa L.). The field was laid out in a randomized complete block design (RCBD) and the treatments included four rates (with and without supplementary hoe weeding - SHW) of oxadiazon 25 EC, butachlor 50 EC, pendimenthalin 50 EC, bullet 700 SC (atrazine + acetochlor + terbuthylazine), eight rates (with or without SHW) of oxyfluorfen 41 FW, hoe weeded at 3 and 6 weeks after transplant- ing (WAT) and untreated control. The treatments were replicated three times. The results indicated that application of oxadiazon 25 EC at 4 l/ha and oxyfluorfen 41FW at 6 l/ha both followed by SHW gave low weed dry weight, larger bulb diameter, higher mean bulb weight and bulb yield per hectare compared to the hoe-weeded control. Adv. Hort. Sci., 2013 27(1-2): 67-72 Corresponding author: idokodav@yahoo.com Received for publication 18 February 2013 Accepted for publication 15 May 2013 68 Ahmadu Bello University, Zaria, Nigeria (11o 39’N, 08o 02’E and 500 m above sea level). Meteorological data on temperature, relative humidity and sunshine hours, as well as physical and chemical characteristics of the soil of the experimental site were collected December 2006-April 2007 and December 2007-April 2008 (Tables 1, 2 and 3). Land preparation involved ploughing, harrowing and ridging (75 cm apart). The plot size was 12 m2 (4 x 3 m) representing the planting basin. Planting was done in rows at spacing of 15 x 30 cm within and between rows. The onion variety used, D77, has a maturity period of 120 to 130 days and potential yield of 5-15 t/ha. Plots were irri- gated by surface flooding before transplanting a day after herbicide application. Subsequent irrigation was applied once a week by surface irrigation of the basin to field ca- pacity, resulting in approximately 15-20 applications to supply about 350-550 mm of moisture as needed by the plant per growing season. In the two seasons, Single Su- per Phosphate (SSP) fertilizer at a rate of 19.8kg P/ha and Muriate of Potash (Potassium) at 10.4 kg K/ha were incor- porated into the basin as basal fertilizer before transplant- ing. Nitrogen (45 kg N/ha) was applied by broadcasting Table 1 - Meteorological data showing mean minimum and maximum temperatures, relative humidity and sunshine hours during 2006/2007 dry season at Kadawa Month Days Air temperature (oC) Relative humidity (%) Sunshine hours Min. Max. December 2006 1-10 14.0 33.5 25.1 7.2 11-20 13.2 32.6 27.2 7.4 21-31 13.5 33.0 27.4 7.0 January 2007 1-10 11.7 31.6 28.3 6.8 11-20 14.9 35.7 29.5 7.0 21-31 13.4 34.3 29.8 6.1 February 2007 1-10 16.2 36.3 32.0 6.1 11-20 19.7 35.9 34.1 5.8 21-29 19.5 37.1 35.8 5.0 March 2007 1-10 19.2 35.8 37.1 6.2 11-20 19.4 38.3 36.1 6.8 21-3 20.4 41.4 36.7 5.7 April 2007 1-10 19.6 40.7 36.9 5.4 11-20 18.6 39.1 37.5 5.6 21-30 22.3 40.9 37.6 6.0 Total 255.6 546.2 491.1 95.1 Average 17.04 36.42 32.74 6.34 Source: Meteorological Unit of the Institute for Agricultural Research, Samaru, Zaria. Table 2 - Meteorological data showing mean minimum and maximum temperatures, relative humidity and sunshine hours during 2007/2008 dry season at Kadawa Month Days Air temperature (oC) Relative humidity (%) Sunshine hours Min Max Dececember 2007 1-10 13.6 35.0 26.9 6.0 11-20 14.0 33.3 23.4 6.4 21-31 14.5 32.0 27.2 5.4 January 2008 1-10 15.1 34.3 27.9 5.0 11-20 13.6 32.7 28.0 5.7 21-31 NA NA 30.1 6.0 February 2008 1-10 17.3 38.3 34.3 5.0 11-20 15.6 34.7 30.8 4.5 21-29 14.8 35.9 32.0 4.5 March 2008 1-10 15.7 34.5 29.9 5.0 11-20 18.9 32.3 32.3 6.1 21-31 23.3 39.4 36.3 6.8 April 2008 1-10 25.7 42.8 38.3 5.4 11-20 23.9 41.1 36.9 6.0 21-30 25.7 41.2 37.6 6.0 Total 251.7 507.4 471.9 83.8 Average 18.00 36.24 31.46 5.59 Source: Meteorological Unit of the Institute for Agricultural Research, Samaru, Zaria. NA= not available. Table 3 - Physico-chemical properties of the 0-20 cm depth of soil at the experimental site during the 2006/2007 and 2007/2008 dry seasons at Kadawa Composition Dry season 2006/2007 Dry season 2007/2008 Physical properties Sand (%) 56.0 58.0 Silt (%) 30.0 30.0 Day (%) 14.0 12.0 Textural class Sandy-loam Sandy-loam Chemical properties pH in H 2 O 5.70 5.80 pH in 0.01 m cacl 2 (1:2.5) 5.10 5.32 Organic carbon (g/kg) 0.58 0.56 Total nitrogen (g/kg) 1.20 1.30 Available phosphorus 0.90 1.20 Exchangeable cations (cmd/kg soil) Calcium 1.88 0.60 Sodium 0.81 0.73 Potassium 0.21 0.37 Magnesium 3.13 2.97 C.E.C. 6.70 6.90 69 using urea (46%W) as split doses at two and six weeks after transplanting (WAT). Treatments consisted of the following rates, each ap- plied with and without supplementary hoe weeding (SHW) for a total of four treatments per herbicide: oxadia- zon 25 EC (4 and 6 l/ha), butachlor 50 EC (5 and 6 l/ha), pendimenthalin 50 EC (5 and 6 l/ha) and bullet 700 SC 9 (1.04 and 1.4 l/ha) (atrazine + acetochlor + terbuthyla- zine), eight treatments (4, 6, 8 and10 l/ha with and without SHW) of oxyfluorfen 41 flowable (FW), and an untreated control; hoe weeding was carried out at 3 and 6 weeks after transplanting (WAT). These treatments were laid out in a randomized complete block design (RCBD) with three replications. All herbicides were applied a day before transplanting using a conventional CP3 knapsack sprayer with a green deflector nozzle at a pressure of 2.1 kg/m2 to deliver a spray volume of 200 l/ha. Supplementary hoe weeding was imposed at 6 WAT on some plots as indi- cated in the treatment because some herbicides have short persistence in the soil and therefore cannot exhibit long season weed control. In the Nigerian savanna, despite high labour requirements and cost of inputs, some workers have emphasized the need to supplement pre-emergence herbi- cide treatments with hoe weeding for long season weed control for increased yields in various crops (Adigun et al., 1987; Magani, 2008; Oluwafemi, 2013). Onion bulbs were harvested manually at 16 WAT. Data on weed dry weight, mean bulb diameter, bulb weight and bulb yield per hectare were assessed and subjected to statistical analysis of variance (ANOVA) as described by Snedecor and Cochran (1967). Differences between treatment means were compared using Duncan Multiple Range Test (DMRT) (Duncan, 1955) at 5% level of probability. 3. Results Weather and soil conditions Meteorological data on temperature, relative humidity and sunshine hours during the study periods (2006/2007 and 2007/2008) are shown in Tables 1 and 2 respectively, while physical and chemical characteristics of the soil of the experimental sites for the same period are presented in Table 3. The average maximum temperature was 36.42 and 36.24°C in 2006/2007 and 2007/2008 respectively, while for the same periods the relative humidity was 32.74 and 31.46% and sunshine hours were 6.34 and 5.59. With re- gard to the soil of the experimental sites, it was classified as sandy loam in both study periods, and the organic car- bon, total nitrogen and available phosphorus were, respec- tively, 0.58, 1.20 g/kg-1 and 0.90 mg/kg-1 in 2006/2007 and 0.56, 1.30 g/kg-1 and 1.20 mg/kg-1 in 2007/2008. Weed dry weight The untreated control had significantly (P≤M0.05) higher weed dry weight than all the other treatments ex- cept for oxadiazon at 4 and 6 l/ha in 2006/2007 and for the combined mean (Table 4). The hoe-weeded control in the 2006/2007 study period resulted in significantly lower weed dry weight, comparable to the application of oxa- diazon at 4 l/ha followed by supplementary hoe weeding (fbSHW), oxyfluarfen at 10 l/ha fbSHW, butachlor at 6 l/ ha fbSHW and pendimenthalin at 5 l/ha fbSHW (Table 4). In 2007/2008, all the herbicides and their rates, including the untreated control, gave statistically comparable weed dry weight. The application of oxadiazon at 6 l fbSHW had significantly (P<0.05) higher weed dry weight than butachlor at 6 l/ha and the hoe-weeded control which gave statistically similar weed dry weights (Table 4). Table 4 - Effects of rates of herbicides on weed dry weight in onion during dry seasons of 2006/2007, 2007/2008 and combine at Kadawa Rates (l/ha) Weed dry weight (kg/ha) Combined mean Herbicides 2006/2007 2007/2008 Oxadiazon 4 101.70 a 17.47 a-c 59.58 ab 4 fbSHW 34.60 l-g 11.23 a-c 22.93 ef 6 82.07 a 15.90 a-c 49.00 a-c 6 fbSHW 38.60 c-f 21.00 a 29.85 d-f Oxyfluorfen 4 56.37 b-e 8.57 a-c 30.08 c-f 4 fbSHW 41.8 c-f 13.96 a-c 27.85 d-f 6 57.70 b-e 14.90 a-c 36.32 c-f 6 fbSHW 38.10 c-f 15.10 a-c 28.60 d-f 8 45.97 l-f 13.96 a-c 29.97 d-f 8 fbSHW 49.59 b-c 9.60 a-c 29.55 d-f 10 62.33 b-e 16.37 a-c 39.35 c-e 10 fbSHW 33.90 d-g 17.7 a-c 25.80 d-f Butachlor 5 45.57 c-f 14.30 a-c 29.93 d-f 5 fbSHW 38.40 c-f 14.46 a-c 26.43 d-f 6 48.37 b-f 6.13 bc 27.25 d-f 6 fbSHW 21.27 fg 14.97 a-c 18.12 fg Bullet 1.04 57.20 b-e 13.03 a-c 35.12 c-f 1.04 fbSHW 42.60 c-f 10.53 a-c 26.57 d-f 1.4 46.80 c-f 14.20 a-c 30.50 d-f 1.4 fbSHW 29.17 e-g 17.70 a-c 23.43 e-f Pendimenthalin 5 67.70 b-d 19.43 a-c 43.57 b-d 5 fbSHW 33.47 d-g 21.30 a-c 27.40 d-f 6 69.27 bc 20.20 a-c 44.73 a-d 6 fbSHW 62.33 b-e 14.46 a-c 38.55 c-e Hoe weeded 3 + 6WAT 3.70 g 5.00 c 6.13 g Untreated check 109.03 a 12.66 a-c 60.85 a SE(±) 10.203 3.847 5.533 Means followed by same letter(s) within a column are not significantly different at 5% (P=0.05) using DMRT. fbSHW= Followed by supplementary hoe weeding. WAT= Weeks after transplanting. 70 Mean bulb diameter Table 5 shows mean bulb diameter for the herbicide treatments. The results reveal a larger bulb size in the first study season compared to the second season. The appli- cation of oxyfluorfen at 4 l/ha produced larger bulbs for all treatments in 2006/2007 and for the combined mean (2006/2007-2007/2008); the values were comparable with the hoe-weeded control in both cases. In 2007/2008, the use of oxadiazon at 6 l/ha fbSHW resulted in bigger bulbs compared with those produced by oxadiazon at 4 l/ha (with or without SHW), pendimethalin at 6 l/ha without SHW and the hoe-weeded control. Oxadiazon at 6 l/ha and the untreated control gave comparable but smaller onion bulbs for the combined mean (Table 5). Mean bulb weight Mean bulb weight appeared higher in the 2006/2007 dry season compared with the following year (Table 6). In the former, hoe weeded control yielded a significantly (P<0.05) higher mean bulb weight, compared with oxadia- zon at 4 l/ha (with or without SHW) and bullet (atrazine + acetochlor + terbuthylazine) at 1.04 l/ha fbSHW. The untreated control gave the lowest mean bulb weight, al- though it was comparable to some herbicide treatments. The application of oxadiazon at 6 l/ha followed by sup- plementary hoe weeding (fbSHW) in 2007/2008 and com- bined mean resulted in the highest mean bulb weight, but it was comparable to oxadiazon at 4 l/ha (with and without Table 5 - Effects of rates of herbicides on mean bulb diameters in onion during dry seasons of 2006/2007, 2007/2008 and combine at Kadawa Herbicides Rates (l/ha) Mean bulb diameter (cm) Combined meanDry season 2006/2007 Dry season 2007/2008 Oxadiazon 4 19.52 ab 9.49 b-d 14.51 a-d 4 fbSHW 19.13 ab 9.36 b-d 14.64 a-d 6 14.85 b-f 7.99 d 11.42 d 6fbSHW 17.68 a-e 16.40 a 17.04 ab Oxyfluorfen 4 21.60 a 12.88 a-d 17.24 a 4 fbSHW 16.93 a-f 15.75 ab 16.17 a-c 6 14.43 b-f 11.87 a-d 13.15 a-d 6fbSHW 15.75 b-f 10.65 a-d 13.20 a-d 8 13.37 ef 13.12 a-d 12.75 b-d 8fbSHW 13.53 l-f 10.77 a-d 12.15 cd 10 15.79 b-f 10.95 a-d 13.37 a-d 10fbSHW 17.99 a-c 14.13 a -d 16.06 a-c Butachlor 5 13.19 d-f 13.22 a-d 13.23 a-d 5 fbSHW 17.37 a-f 12.25 a-d 14.81 a-d 6 14.76 b-f 9.97 a-d 12.36cd 6 fbSHW 17.55 a-f 14.18 a-d 15.87 a-c Bullet 1.04 15.67 b-f 8.49 cd 12.06 cd 1.04 fbSHW 19.54 ab 13.23 a-d 16.38 a-c 1.4 16.92 a-f 12.43 a-d 14.67 a-d 1.4 fbSHW 16.60 a-f 13.00 a-d 14.80 a-d Pendimenthalin 5 16.52 a-f 11.15 a-d 13.84 a-d 5 fbSHW 19.15 a-c 14.64 a-c 16.90 ab 6 17.02 a-f 9.76 b-d 13.34 a-d 6 fbSHW 18.08 a-c 12.19 a-d 15.14 a-d Hoe weeded 3 + 6WAT 18.96 a-d 9.78 b-d 14.37 a-d Untreated check 11.87 f 10.05 a-d 10.90 d SE (±) 1.673 1.903 1.269 Means followed by same letter(s) within a column are not significantly different at 5% (P=0.05) using DMRT. fbSHW= Followed by supplementary hoe weeding. WAT= Weeks after transplanting. Table 6 - Effects of rates of herbicides on mean bulb weight of onion during dry seasons of 2006/2007, 2007/2008 and combine at Kadawa Herbicides Rates (l/ha) Mean bulb weight (g) Combined meanDry season 2006/2007 Dry season 2007/2008 Oxadiazon 4 77.48 a-c 20.72 c 49.10 a-f 4 fbSHW 86.03 ab 35.63 a-c 60.83 a-d 6 48.34 c-h 19.38 c 33.89 fg 6fbSHW 68.26 b-e 71.03 a 69.65 a Oxyfluorfen 4 33.51 f-h 43.41 a-c 38.46 c-g 4 fbSHW 58.97 b-g 64.45 ab 61.71 a-c 6 37.38 e-h 33.08 a-c 35.23 fg 6fbSHW 50.88 c-h 31.59 bc 41.23 c-g 8 27.65 gh 43.70 a-c 35.68 e-g 8fbSHW 35.77 f-h 27.61 bc 31.69 fg 10 52.89 c-h 25.65 c 39.27 c-g 10fbSHW 62.05 b-f 50.05 a-c 56.05 a-f Butachlor 5 41.59 d-h 45.48 a-c 43.53 b-g 5 fbSHW 48.60 c-h 48.27 a-c 48.44 a-f 6 43.57 d-h 36.86 a-c 40.21 c-g 6 fbSHW 47.36 c-h 45.87 a-c 46.62 a-f Bullet 1.04 50.18 c-h 21.95 c 36.06 d-g 1.04 fbSHW 77.25 a-c 43.19 a-c 60.22 a-e 1.4 44.89 d-h 37.96 a-c 41.43 b-g 1.4 fbSHW 68.58 b-e 38.24 a-c 53.41 a-f Pendimenthalin 5 55.15 c-g 24.67 c 39.91 c-g 5 fbSHW 52.96 c-h 55.03 a-c 53.00 a-f 6 60.68 b-f 22.81 c 43.75 b-g 6 fbSHW 69.19 b-d 33.68 a-c 51.44 a-f Hoe weeded 3 + 6WAT 103.06 a 28.46 bc 65.77 ab Untreated check 22.87 h 20.03 c 21.45 g SE (±) 9.126 11.171 7.189 Means followed by same letter(s) within a column are not significantly different at 5% (P=0.05) using DMRT. fbSHW= Followed by supplementary hoe weeding. WAT= Weeks after transplanting. 71 supplementary hoe weeding), oxyfluorfen at 4 and 10 l/ ha fbSHW, pendimenthalin at 5 and 6 l/ha fbSHW and the hoe-weeded control (Table 6). The untreated control con- sistently maintained the lowest mean bulb weight in both years of study and in the combine mean. Onion bulb yield In 2006/2007, the use of oxadiazon at 4 l/ha fbSHW, oxyfluorfen at 6 l/ha and pendimentalin at 5 and 6 l/ha fbSHW resulted in statistically similar but significantly (P≤0.05) higher bulb yield compared with oxyfluorfen at 4, 8 and 10 l/ha and the untreated control. The differ- ences in bulb yield between all other herbicides and their rates including the untreated control were not significant (P≤0.05) statistically (Table 7). The effect of the herbi- cides and their rates on onion bulb yield was not signifi- cant in 2007/2008. The application of pendimenthalin at 5 l/ha fbSHW resulted in significantly (P≤0.05) higher bulb yield compared with oxyfluorfen at 8 and 10 l/ha and the untreated control for the combined mean. All the other herbicides and their rates gave statistically similar bulb yields (Table 7). 4. Discussion and Conclusions Weed dry weights were very high in the untreated con- trol compared to the herbicide-treated plots in 2006/2007 and combined means, except for oxadiazon at 4 and 6 l/ ha without fbSHW. This could be due to a higher weed intensity resulting from no hoe weeding and herbicide treatment. Lower weed dry weights and herbicide sup- pression of weeds in crops has been demonstrated in many studies (Ibrahim, 2001; Ishaya, 2004; Adekpe et al., 2007). The statistically similar weed dry weight found in the present study for hoe weeded control and oxadiazon at 4 l/ha fbSHW, oxyfluorfen at 10 l/ha fbSHW, butachlor at 6 l/ha fbSHW and pendimnthalin (5 l/ha fbSHW) dem- onstrates herbicide competitiveness with conventional hoe weeding in weed management practices. Similar observations have been made in other related studies (Adekpe et al., 2007; Shinggu et al, 2009; Oluwafemi, 2013). Bulb size was higher with the application oxy- fluorfen at 4 l/ha compared to to hoe-weeded control in both 2006/2007 and combined data. Numerical differ- ences in bulb size (diameter) were observed and in some cases not statistically significant, reflecting the within treatment variability encountered in the study. The use of oxyfluorfen has been reported to increased onion perfor- mance (Ghosheh, 2004) Onion mean bulb weight and bulb yield (t/ha) were observed to be better with oxyfluorfen (6 l/ha fbSHW) and pendimenthalin at 5 and 6 l/ha fbSHW. This observa- tion may not be unconnected with the observed favour- able weed control, higher bulb diameter influenced by these herbicides. The weed control must have helped in the reduction of competition for both the above and underground growth factors by the weeds, thereby pro- viding an adequate environment for the growth and bulb yield of onion. The high total nitrogen and available phosphorus found in the soil of the experimental sites might have contributed to high bulb yield in these low weed-infested plots. The use of oxyfluorfen, oxadiazon and pendimethalim has been reported to improve perfor- mance in some bulb and root vegetable crops (Amrutkar et al., 2002; Sanjeev et al., 2003; Adekpe et al., 2007; Adekpe et al., 2012). It can be concluded from the present study that the use of oxadiazon at 4 and 6 l/ha fbSHW and oxyfluorfen at 6 l/ha fbSHW gives the lowest weed dry weight, higher bulb diameter, higher mean bulb weight and bulb yield per hectare compared to the hoe-weeded control. Table 7 - Effects of rates of herbicides on onion bulb yield during dry seasons of 2006/2007, 2007/2008 and combine at Kadawa Herbicides Rates (l/ha) Onion bulb yield (t/ha) Combined meanDry season 2006/2007 Dry season 2007/2008 Oxadiazon 4 6.00 a-c 0.73 3.37 a-d 4 fbSHW 6.93 a 0.83 3.88 a-c 6 3.78 a-d 0.66 2.22 a-d 6fbSHW 4.30 a-d 2.66 3.44 a-d Oxyfluorfen 4 2.17 b-d 2.27 2.22 a-d 4 fbSHW 3.06 a-d 2.60 2.83 a-d 6 7.05 a 1.13 4.09 ab 6fbSHW 3.90 a-d 0.70 2.30 a-d 8 1.78 cd 2.13 1.96 b-d 8fbSHW 3.68 a-d 0.93 2.30 a-d 10 2.05 cd 0.88 1.46 cd 10fbSHW 5.22 a-d 1.90 3.58 a-c Butachlor 5 3.22 a-d 2.07 2.65 a-d 5 fbSHW 5.05 a-d 2.13 3.59 a-c 6 3.22 a-d 1.90 2.58 a-d 6 fbSHW 3.58 a-d 1.40 2.48 a-d Bullet 1.04 3.45 a-d 0.92 2.19 a-d 1.04 fbSHW 5.39 a-d 1.20 3.30 a-d 1.4 2.83 a-d 2.13 2.48 a-d 1.4 fbSHW 4.22 a-d 1.00 2.61 a-d Pendimenthalin 5 4.61 a-d 0.47 2.54 a-d 5 fbSHW 6.56 a 2.93 4.75 a 6 4.00 a-d 0.53 2.27 a-d 6 fbSHW 6.92 a 1.20 4.06 ab Hoe weeded 3 + 6WAT 5.78 a-c 0.47 3.12 a-d Untreated check 1.22 d 0.73 0.98 d SE (±) 1.279 0.762 0.737 Means followed by same letter(s) within a column are not significantly different at 5% (P=0.05) using DMRT. fbSHW= Followed by supplementary hoe weeding. 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