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INTERNATIONAL JOURNAL OF AGRICULTURE & BIOLOGY 1560–8530/2006/08–5–636–640 http://www.fspublishers.org Effect of Various Weed Control Methods on Yield and Yield Components of Wheat Under Different Cropping Patterns MUHAMMAD RIAZ1, M. AZIM MALIK†, TAHIRA ZAFAR MAHMOOD AND MUHAMMAD JAMIL‡ Weed Management Program, and ‡Sugar Crops Research Program, NARC, Islamabad, Pakistan †Department of Agronomy, UAAR, Rawalpindi, Pakistan 1 Correspondence author’s e-mail: riaznarc@yahoo.com; jamil_narc@yahoo.co
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   I NTERNATIONAL J OURNAL OF A GRICULTURE &   B IOLOGY  1560–8530/2006/08–5–636–640http://www.fspublishers.org Effect of Various Weed Control Methods on Yield and YieldComponents of Wheat Under Different Cropping Patterns M UHAMMAD R IAZ 1 ,   M.   A ZIM M ALIK †,   T AHIRA Z AFAR M AHMOOD AND M UHAMMAD J AMIL ‡ Weed Management Program, and  ‡ Sugar Crops Research Program, NARC, Islamabad, Pakistan †  Department of Agronomy, UAAR, Rawalpindi, Pakistan 1 Correspondence author’s e-mail:riaznarc@yahoo.com; jamil_narc@yahoo.com  ABSTRACT   In this study, different weed control methods (chemical, mechanical, hand weeding & their integration) under variouscropping patterns (wheat-fallow-wheat; wheat-corn-wheat; wheat-legume-wheat) were compared for their efficiency to controlvarious weed species. Among different weed control methods, integrated weeding i.e. chemical weeding (recommended doseof isoproturon) at 2 - 3 leaf stage of weeds with a follow-up hand weeding after 50 days of crop sowing (WC 6 ) under wheat-mungbean-wheat cropping pattern, gave promising results. This was closely followed by mechanical weeding after 20 days of crop sowing with a follow-up hand weeding after 50 days of crop sowing (WC 5 ) and/or two hand weedings after 20 and 40days of crop sowing (WC 2 ). These weed control methods significantly affected the yield and yield components of wheat understudy during both the study years. The economic analysis of these weed control methods also showed better performance of WC 6 (chemical weeding at 2 - 3 leaf stage of weeds + hand weeding at 50 DAS) as compared to rest of the treatments underall cropping patterns. Key Words: Wheat; Weeds; Integrated weed control; Cropping pattern; Yield components; Triticum aestivum L.   INTRODUCTION Weed infestation is one of the main causes of lowwheat yield in Pakistan, which may reduce yield by 25 -30% (Nayyar et al ., 1992). Besides quantitative effects onyield, weeds deteriorate the quality of produce through thephysical presence of their seeds and debris. Weed density,type of the weeds, their persistence and crop managementpractices determine the magnitude of yield loss.The main weeds of wheat in Pakistan include Phalarisminor  L. (Canary grass), Avena fatua L.   (Wild oat)  ,Chenopodium album L.   (Lamb’s quarters)  , Medicago polymorpha L. (Wild medic), Convolvulus arvensis L.   (Fieldbind weed), Anagallis arvensis L.   (Blue pimpernel)  ,Fumaria indica L. (Fumatory)  , Melilotus alba L. (Sweetclover), Rumex dentatus L. (Broad leaf dock) and Seniberadidyma (Swine cress) (Shamsi & Ahmed, 1984) . Wheatcrop usually suffer from stress created by weeds throughcompetition for water, nutrients, space and sunlight(Anderson, 1983) along with interference caused byreleasing toxic substances into the rhizosphere of the cropplants (Rice, 1984). Apart from increasing the productioncost, they also intensify the disease and insect pest problemby serving as alternative hosts. The weed problem is gettingfrom bad to worst in wheat sown under irrigatedenvironments, where cropping intensity is rapidly increasingwith the result that weed management through traditionalmethods as Dab (delayed planting) and hand weeding hasbecome impossible.The farmers control weeds in wheat during landpreparation. Khan and Saghir (1987) pointed out thattraditional hand weeding is slow, tedious and labouroriented. Labour input is not only getting expensive but isbecoming scanty too and at present the cost of handweeding is about Rs. 5600 ha -1 . Very few farmers practicerotation for controlling weeds. Moreover, in the irrigatedareas of Pakistan wheat is sown mostly by broadcastingseed in which weeding is difficult (Byerlee et al. , 1986).Recently, quite a large number of farmers have startedusing herbicides. The use of herbicides, however, is too un-economical in addition to resulting in serious ecological andenvironmental problems such as increase in herbicideresistance in the weeds, ground water contamination andenvironmental pollution. In fact, none of the weed controlmethods is best under all conditions. So, there is a need tomake a comparative study of different weed managementtechniques in wheat and to develop an integrated weedmanagement approach, which should be efficient and costeffective and environmentally safe.This study was planned to integrate different weedcontrol methods in rain-fed wheat crop to identify costeffective weed control methods in wheat based croppingpatterns and to study the phytotoxic effect of herbicides ondifferent crops in order to achieve sustainable rain-fed wheatyield. MATERIALS AND METHODS The field experiment was conducted under rain-fedconditions for two crop years (2002 - 03 & 2003 - 04) atNational Agricultural Research Centre (NARC), Islamabad.The experiments were laid out using two factors, in-splitplot design with three replications. The cropping patternswere placed in the main plots and weed control methods insub-plots.  Avena futua L. (Wild oat), Fumaria indica L.(Fumatory), Euphorbia helioscopia L.,  Melilotus indica L.,     E FFICIENCY OF V ARIOUS W EED C ONTROL M ETHODS /   Int. J. Agri. Biol., Vol. 8, No. 5, 2006    637 Chenopodium album L. (Lamb’s quarters), Medicago polymorpha L. (Wild medic),   and Convolvulus arvensis L.(Fieldbind weed)   were the main weed species found inwheat field. Six weed control methods included in the studywere (i) Weedy check (WC 1 ): No weed control during rabiand kharif, (ii) Hand weeding at 20 and 40 DAS (WC 2 ):(complete weed control) during rabi and kharif throughhand weeding, (iii) Mechanical weeding at 20 DAS (WC 3 ),(iv) Chemical weeding (WC 4 ) at 2 - 3 leaf stage of weeds,(v) Mechanical weeding at 20 days after sowing + handweeding at 50 DAS (WC 5 ) and (vi) Chemical weeding at 2 -3 leaf stage of weeds + hand weeding at 50 DAS (WC 6 ).The four cropping patterns considered in the study were (i)Wheat-fallow-wheat (CP 1 ), (ii) Wheat-corn-wheat (CP 2 ),(iii) Wheat-mungbean-wheat (CP 3 ) and (iv) Wheat-cowpeas-wheat (CP 4 ).Wheat variety Wafaq 2001 was planted in the middleof November in 25 cm apart rows. A local recommendedmaize variety was planted in the month of July in rows 75cm apart 20 cm plant to plant distance. Mungbean varietyNCM-209 was planted in the second week of July in rows25 cm apart. Similarly, for cowpeas, a local recommendedvariety was sown in July. Recommended plant populationwas maintained for all crops.All other agronomic operations except those understudy were kept normal and uniform for all the treatments.Standard procedures were adopted for recording the data onvarious growth and yield parameters. Data collected werestatistically analyzed by using the Fisher’s Analysis of Variance technique and Duncan`s New Multiple Range(DNMR) test at 0.05 P was applied to compare thedifferences among treatments (Steel & Torrie, 1984). RESULTS AND DISCUSSION 1. Number of tillers m -2 . Different cropping patternsaffected significantly the number of tillers during both theyears of study. Maximum tillers were recorded under CP 4  followed by CP 2 . Rest of the cropping patterns (CP 1 & CP 3 )showed significantly lower tillers, which were statistically atpar with each other.Statistically significant differences in number of tillerswere observed due to different weed control methods duringthe study years. Maximum number of tillers (261.89 m -2 )was found in case of WC 6 followed by 257.7 m -2 in case of WC 5 . WC 2 also showed better performance as compared toWC 3 and WC 4 during both years (Table I). The increase innumber of tillers as compared to weedy check was possiblydue to effective weeding at proper time resulting in lesscompetition of weeds with wheat for growth factors. Theseresults are in line with the previous findings of Ahmad et al.  (1989), who reported that water shower after sprayapplication of Arelon @ 1.5 kg ha -1 proved to be beneficialby producing more productive tillers, which were at parwith hand weeding. The increase in number of tillers ascompared to weedy check in all the weed control treatmentsindicated that the possibility of better availability of plantnutrients and favorable environment under weed freeconditions resulted by various weed control methods duringboth years. 2. Plant height. All cropping patterns showed significantresults during the study years. CP 2 and CP 4 produced longerplants, while CP 1 showed comparatively poor performancein terms of plant height (Table I).It is clear from the data that plant height of wheat wasalso significantly affected by different weed controlmethods (Table I). WC 6 caused maximum increase in plantheight (109.8 cm) followed by WC 5 that resulted in 104.8cm plant height at maturity. The increase in wheat plantheight was possibly due to better weed suppression atproper time resulting in maximum utilization of moistureand nutrients by the crop during both years. It is apparentfrom the data that mechanical weeding followed by a handweeding after 50 days of crop sowing (WC 5 ) resulted inabout 12% improvement in plant height and was statisticallybetter than rest of the treatments except WC 6 . The efficiencyof chemical weeding at 2 - 3 leaf stage of weeds (WC 4 ) wasalso significant during both years of study. The taller plantsin these treatments were due to better weed control. Plantheight of 100.2 cm was obtained with two hand weedingsafter 20 and 40 days of crop sowing (WC 2 ), which was alsosignificantly better than that of weedy check (WC 1 ) andmechanical weeding at 20 DAS (WC 3 ) as well. Weeding atproper time successfully reduced competition between cropplants and weeds and in turn resulted in healthy crop stand.Similar results have also been reported by Ahmad et al.  (1984). 3. Spike length. All cropping patterns showed significantresults during the study years. The highest spike length of wheat was obtained under CP 4 closely followed by CP 2  during the study years, while CP 1 and CP 3 comparativelydid not affect the spike length of wheat (Table I).Different weed control methods increased the spikelength significantly. The results showed that maximumspike length was obtained with WC 6 followed by WC 2  during both years of study (Table I). Other treatments i.e.WC 3 , WC 4 and WC 5 also had a significant effect on spikelength of wheat crop but their performance was some-whatpoor than WC 6 and WC 2 . The increase in spike length of wheat due to both these treatments (WC 6 & WC 2 ) was about62 and 56%, respectively over control (WC 1 ). Aconsiderable increase in spike length, because of thesetreatments was probably due to reduced weed competitionand availability of adequate amount of plant nutrients andmoisture to crop plants. The increase in spike length byweed control methods is well documented by Verma andChaturvedi (1985), Verma and Kumar (1986), Bhan (1987)and Ahmad et al. (1989). 4. Number of spike-lets spike -1 . A non-significant effect of cropping patterns on spike-lets spike -1 of wheat was foundduring both study years (Table I). However, the highestnumber of spike-lets per spike in case of CP 2 may beattributed complete eradication of weeds. Among all the   R IAZ   et al . /   Int. J. Agri. Biol., Vol. 8, No. 5, 2006    638 weed control methods, WC 3 showed comparatively poorperformance but on an average, it was about 27% betterthan that of WC 1 (Table I). On the other hand, when afollow-up hand weeding after 50 days of crop sowing(WC 5 ) was done, a further increase of about 27% in numberof spike-lets per spike was observed due to effectiveweeding at proper time. WC 6 produced maximum numberof spike-lets spike -1 followed by WC 2 and WC 5 . The betterperformance of WC 6 , WC 2 and WC 5 as compared to rest of the treatments could be due to effective weed control, whichultimately facilitated healthy crop stand and resulted in thehighest number of spike-lets spike -1 during both years. 5. Number of grains spike -1 . The data revealed that betternumber of grains spike -1 was produced under CP 2 and CP 4  closely followed by CP 3 during both study years. Thenumber of grains spike -1 was significantly affected byvarious weed control methods during both years (Table I).Maximum number of wheat grains spike -1 (59.21) wasobserved with WC 6 followed by WC 5 having 52.0 grainsspike -1 (Table I). Two hand weedings after 20 and 40 daysof crop sowing (WC 2 ) also produced promising results butits efficiency was less than that of WC 6 and WC 5 .Maximum grain production with efficient weedingtreatments may be attributed to supportive action of weedcontrol techniques described by Singh and Sharma (1984),Pandey and Singh (1985), Parihar et al. (1986), Rajput et al.  (1988), Tanweer et al. (1990) and Tomar et al. (2003).  6. 1000-Grain weight. Maximum 1000-grain weight of wheat was produced with CP 3 closely followed by CP 4 andCP 2 . The CP 1 produced statistically less 1000-grain weightthan rest of the cropping patterns (Table I). The data alsorevealed that more number of grains spike -1 was producedunder CP 2 and CP 4 closely followed by CP 3 during bothstudy years (Table I). As far as the effect of weed controlmethods on 1000-grain weight is concerned, different weedcontrol treatments significantly influenced the 1000-grainweight of wheat. Maximum 1000-grain weight was obtainedwith WC 6 and WC 2 during both the years. Rest of thetreatments (WC 3 , WC 4 & WC 5 ) produced similar andcomparatively less 1000-grain weight but were statisticallybetter than that of WC 1 . On an average, these treatments(WC 3 , WC 4 & WC 5 ) showed about 27% increase in 1000-grain weight as compared to WC 1 . The better performancein case of WC 6 and WC 2 (about 48 & 43% increase overWC1, respectively) has also been discussed previously. Theweeding at proper time with an adequate source couldprovide healthy environment for the crops and ultimatelybetter yields. This is quite possible that weed free good cropstand produced robust grains and ultimately resulted in more1000-grain weight. Similar results have also been reportedby Cheema et al. (1997), Singh and Prasad (1998),Narkhede et al. (2000), Tomar et al. (2003) and Kumari andPrasad (2003). While the results reported by Margin et al.  (1984) showed no effect on grain weight of wheat byeliminating weed competition.   7. Grain yield of wheat. A significant effect of croppingpatterns on grain-yield of wheat crop was also found duringthe years of study. The maximum grain yield was recordedwith CP 3 than rest of the cropping patterns (Table I). Thismight be due to the inclusion of legumes that enhanced soilfertility and resulted in maximum grain yield of wheat. Thedata regarding grain yield of wheat as affected by differentweed control methods also revealed that all the weed controltreatments increased wheat grain yield during both years of study (Table I). Maximum grain yield (3.5 tonnes ha -1 ) wasobtained with WC 6 followed by (3.4 tonnes ha -1 ) WC 2  during the study period. WC 6 and WC 2 producedapproximately 67 and 63%, respectively more grain yield of wheat over weedy check. Among all the weed controlmethods, WC 3 showed poor performance, but was slightlybetter than WC 1 . A follow-up hand weeding after 50 days of crop sowing (WC 5 ) interestingly improved grain yield of wheat by about 25%. This indicates that re-emergence of weeds later on occurred during crop growth period andcaused a considerable reduction in grain yield. Similarfindings have also been narrated by Cheema (1988),Tanweer et al. (1990) and Pandey and Mishra (2002). 8. Straw yield of wheat. Various cropping patterns showed Table I. Effect of different cropping patterns and weed control methods on yield and yield components of wheat Treatments No. of tillers(m -2 )Plant height(cm)Spike length(cm)No. of spike-letsspike -1  No. of grainsspike -1  1000-grainwt. (g)Grain yield(t ha -1 )Straw yield(t ha -1 )Total Biol.yield (t ha -1 )Harvestindex (%)A. Years Y 1 246.03b * 101.00b * 10.44b * 23.47b * 48.39b * 46.40b * 2.683b * 5.682b * 8.550b * 31.02b *  Y 2 249.67a 101.97a 10.97a 24.17a 49.54a 47.76a 2.850a 5.717a 8.575a 33.08a B. Cropping patterns  CP 1 247.19c * 100.53c * 10.39c * 23.58 NS 48.08b * 46.19b * 2.687d * 5.665 NS 8.526b * 31.28c *  CP 2 248.03b 102.08a 10.81ab 24.06 49.19a 47.03ab 2.776c 5.709 8.572a 32.10bCP 3 247.03c 101.28b 10.67bc 23.86 48.89ab 48.00a 2.808a 5.716 8.579a 32.48aCP 4 249.14a   102.06a 10.97a 23.78 49.69a 47.11ab 2.796b 5.711 8.574a 32.36a C. Weed Control Methods  WC 1 233.04f  * 98.12e * 7.88e * 17.08e * 40.54f  * 38.63c * 2.078f  * 5.198d * 7.487f  * 27.76f  *  WC 2 253.71c 100.21d 12.29b 26.42b 48.58c 51.96a 3.392b 6.397a 9.864b 34.39bWC 3 237.96e 94.21f 10.79c 21.75d 45.92e 45.67b 2.300e 5.228d 7.594e 30.30eWC 4 242.87d 101.83c 10.17d 23.58c 47.50d 46.79b 2.524d 5.284c 7.883d 32.02dWC 5 257.71b 104.79b 10.37cd 26.25b 52.04b 46.13b 2.836c 5.725b 8.636c 32.87cWC 6 261.79a 109.75a 12.75a 27.83a 59.21a 53.33a 3.469a 6.369a 9.914a 34.99aY 1 =1 st year, Y 2 =2 nd year, CP 1 = were wheat-fallow-wheat, CP 2 = wheat-corn-wheat, CP 3 = wheat-mungbean-wheat, CP 4 = wheat-cowpeas-wheat,WC 1 = Weedy Check, WC 2 = Hand Weeding at 20 and 40 DAS, WC 3 = Mechanical Weeding at 20 DAS, WC 4 = Chemical Weeding at 2-3 leaf stage of weeds, WC 5 = MechanicalWeeding at 20 DAS + Hand Weeding at 50 DAS, WC 6 = Chemical Weeding at 2-3 leaf stage of weeds + Hand Weeding at 50 DAS; * Means not sharing a letter in commonwithin treatments differ sinificantly at 5% robability level; NS = Non sinificant   E FFICIENCY OF V ARIOUS W EED C ONTROL M ETHODS /   Int. J. Agri. Biol., Vol. 8, No. 5, 2006    639 non-significant results during the study years (Table I).However, maximum straw yield was found in case of CP 3 ,while all other cropping patterns (CP 1 , CP 2 & CP 4 )produced comparatively lower straw yield. Different weedcontrol methods significantly affected straw yield of wheatduring the study period. WC 6 and WC 2 out yielded in termsof straw yield as compared to rest of the treatments (TableI). These treatments produced about 22 and 23%,respectively more straw yield as compared to weedy check (WC 1 ). WC 5 also showed statistically significant increase instraw yield of wheat during the study years. The poorperformance of WC 3 and WC 4 was probably due toinadequate weeding at initial stage of crop and re-emergence of weeds during crop growth period, resulting inless crop biomass. Decrease in crop biomass as a result of weeds has also been reported by Tiwari et al. (1984). Theincrease in wheat biomass (straw yield) under varioustreatments may be attributed to suppression of weed densityand growth that also favored increase in number of tillers m -2 and plant height. Significantly higher straw yield in weedcontrol treatments compared to weedy check has alsoreported by Sarwar (1994), Pandey and Mishra (2002) andRoslon and Fozelfors (2003). 9. Biological yield. Maximum biological yield wasproduced by CP 2 , CP 3 and CP 4 during the study years,while CP 1 gave less total biological yield. The effect of different weed control methods on total biological yield of wheat was statistically significant during both the years of study (Table I). WC 6 out yielded significantly followedby WC 2 . These treatments (WC 6 & WC 2 ) increasedapproximately 32 and 31%, respectively biological yieldof wheat over control (WC 1 ). Among all weed controlmethods, WC 3 showed poor performance than rest of thetreatments, but was statistically better than that of WC 1 .However, its efficiency was further increased about 14%with a follow up hand weeding after 50 days of cropsowing. Significant increase in total biological yield of crops due to weed control methods has also been reportedby Tiwari et al. (1984), Pandey and Mishra (2002) andRoslon and Fogelfors (2003). 10. Harvest index. The effect of different croppingpatterns on the harvest index of wheat was foundstatistically significant during both years of study. Themaximum harvest index (32.5 & 32.4%) of wheat wascalculated for CP 3 and CP 4 , respectively. It is clear fromthe data that the harvest index of wheat crop as affectedby different weed control methods showed significantdifferences during the study years (Table I). Amongvarious weed control treatments, higher value of harvestindex (35%) was recorded for plots, where chemicalweeding at 2 - 3 leaf stage of weeds with a follow up handweeding after 50 days of crop sowing (WC 6 ) wereapplied. Twice hand weeding after 20 and 40 days of cropsowing (WC 2 ) also resulted in high harvest index value of 34.4% during the study years. The other treatmentsshowed comparatively lower value of harvest index beingminimum with WC 3 but were statistically higher thanWC 1 . The significant increase in harvest index may beattributed to suppression of weed growth resulting inmore availability of plant nutrients to wheat crop, whichfavored utilization of photo synthates for better grainyield formation. Similar conclusions have also beendrawn by Salisbury and Ross (1978) and Sarpe et al.  (1986). The lower harvest index value in case of WC 3  might be due to ineffective weed control. The lowerharvest index value at higher weed density has beendiscussed by Sarwar (1994). Economic analysis. The economic analysis (Table II)revealed that WC 6 proved to be the best weed controlmethod under all cropping patterns followed by WC 2  during both years of study except CP 4 . Although WC 6  gave higher return (Rs. = 25120.96) than rest of the weedcontrol treatments under CP 1 , but the net benefit was lessthan other cropping patterns (CP 2 , CP 3 & CP 4 ). Maximumnet benefit of Rs. 77837.80 was obtained with treatmentWC 6 under CP 2 in both the study years. It decreasedgradually under CP 3 , CP 4 and CP 1 cropping patterns withrest of the treatments. Among all weed control methods, Table II. Net benefit of various Cropping Patterns under different weed control methods   Treatments CP 1 CP 2 CP 3 CP 4   WC 1 (Weedy Check) 12201.25 50304.25 45725.78 40147.58WC 2 (Hand Weeding at 20 and 40 DAS) 23697.25 72247.77 66641.77 60972.75WC 3 (Mechanical Weeding at 20 DAS) 13961.50 61398.25 61021.95 48588.75WC 4 (Chemical Weeding at 2-3 leaf stage of weeds) 15388.30 64172.82 64313.99 52737.49WC 5 (Mechanical Weeding at 20 DAS + Hand Weeding at 50 DAS) 17725.00 68549.48 66595.25 61970.27WC 6 (Chemical Weeding at 2-3 leaf stage of weeds + Hand Weeding at 50 DAS) 25120.96 77837.80 75112.74 73206.02 CP 1 = Wheat - Fallow – Wheat, CP 2 = Wheat - Corn – Wheat, CP 3 = Wheat - Mungbean – Wheat, CP 4 = Wheat - Cowpeas – Wheat Table III. Cost benefit ratio of various Cropping Patterns under different weed control methods   Treatments CP 1 CP 2 CP 3 CP 4   WC 1 (Weedy Check) 1.82 2.81 2.65 2.41WC 2 (Hand Weeding at 20 and 40 DAS) 2.13 2.82 2.68 2.51WC 3 (Mechanical Weeding at 20 DAS) 1.85 2.99 2.99 2.54WC 4 (Chemical Weeding at 2-3 leaf stage of weeds) 1.88 2.95 2.95 2.52WC 5 (Mechanical Weeding at 20 DAS + Hand Weeding at 50 DAS) 1.91 2.86 2.81 2.65WC 6 (Chemical Weeding at 2-3 leaf stage of weeds + Hand Weeding at 50 DAS) 2.23 3.00 2.93 2.81 CP 1 = Wheat - Fallow – Wheat, CP 2 = Wheat - Corn – Wheat, CP 3 = Wheat - Mungbean – Wheat, CP 4 = Wheat - Cowpeas - Wheat
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