leaching behaviour of four herbicides in two soils of kerala
TRANSCRIPT
193
Indian Journal of Weed Science 47(2): 193–196, 2015
Leaching behaviour of four herbicides in two soils of Kerala
K.M. Durga Devi*, C.T. Abraham and C.N. UpasanaCollege of Horticulture, Kerala Agricultural University, Thrissur, Kerala 680 656
Received: 7 April 2015; Revised: 23 May 2015
ABSTRACTThe present study was conducted to find out the extent of leaching of butachlor, pretilachlor, 2,4-D andoxyfluorfen in two soil types, viz. Type I [coarse textured low organic matter soil (Mannuthy–Ultisol] andType II [fine textured high organic matter soil (Alappad-Inceptisol]. Intact soil columns were collectedfrom the paddy fields after the harvest of second crop. Butachlor, pretilachlor, 2,4-D and oxyfluorfen wereapplied in moist soil columns at the recommended rate of application. Soil samples from different depthsup to 10 cm (top 5 segments of 2 cm each) and the leachate at 30 and 60 cm depths were analyzed forherbicide residues using gas chromatography. Among the four herbicides tested, 2,4-D registeredhighest level of residue in the leachate (0.20 ppm at 60 cm depth). Pretilachlor and butachlor followed thesame trend in the pattern of movement of residue through the soil columns. However, the leachate ofpretilachlor registered much lower quantity of residue (0.006 ppm). Fine textured organic matter rich soilrecorded lower residue levels compared to the soil with coarse texture and poor organic matter. It couldbe attributed to the high adsorptive power of the soil, especially at the top layers with high organic mattercontent. Oxyfluorfen residues could not be detected in the leachate, because of its poor water solubility.
Key words: 2,4-D, Butachlor, Leaching, Oxyfluorfen, Pretilachlor
Among the different pre-emergence herbicidesin rice, butachlor, pretilachlor and oxyfluorfen aremore popular in the paddy fields of Kerala. Sodiumsalt of 2, 4-D is the most common post-emergenceherbicide in the major rice bowls of the state, viz.Kole and Kuttanad. Herbicide movement in soils is ofmajor concern in tropical soils with heavy rainfall.Since these herbicides are applied to the soil surfacewithout incorporation, heavy rainfall soon afterapplication may cause excessive leaching of theherbicide from the surface zone, resulting in poorweed control. In the case of herbicides with high soilmobility, leaching may lead to injury of deeper-rooteddesirable species. In addition, herbicide leaching mayresult in contamination of ground and surface water(Anderson 1983). Movement of herbicide within thesoil profile is influenced by many factors such aschemical nature of herbicide, the adsorptive capacityof soil and the amount of water available fordownward movement through the soil. Butachlor,pretilahlor, oxyfluorfen and 2,4-D differ much in theirwater solubility (RSC 1987). Considering thesefactors, studies on leaching pattern of three pre-emergence herbicides and one post-emergenceherbicide were conducted in two soil types of Kerala,under All India Coordinated Research Programme onWeed Control during the period from 2007-08 to2010-11.
MATERIALS AND METHODSIntact soil columns were collected from two soil
types, viz. Type I (sandy loam low organic matter soilof Ultisol order at Rice field of Agricultural Researchstation, Mannuthy) and Type II (high organic matterclayey soil of Inceptisol order, Kole Lands, Alappad)after the harvest of second crop. Long PVC tubes (60cm) of 16 cm diameter were taken for Type I soil.Tubes of only 30 cm and 16 cm diameter were takenfor Type II soil because the area is below mean sealevel and hence collection of intact soil columnsbelow 30 cm was not possible. The tubes were cutvertically and the two halves were pressed onto thelateral sides of the soil pit of 60 cm deep, dug in therice field. The soil corresponding to the differentdepths were transferred as such to the two halves ofthe PVC column and they were joined together usingadhesive tape. The tube was kept on an iron standafter tying the lower end with a muslin cloth. Afteradding water continuously to attain constantpercolation rate, the herbicides were added at therecommended rate of application, viz.1.25 , 0.75, 1.0and 0.2 kg/ha for butachlor (Machete®), pretilachlor(Rifit®), 2,4-D (Fernoxone®) and oxyfluorfen(Goal®), respectively using a spray volume of 500 L/ha. The quantity of solution required for spraying wascalculated based on the surface area.
*Corresponding author: [email protected]
194
Water was added frequently to the top of thecolumn at one day after spraying. A total of 1000 mLwater was added through the column (200 mL x 5times) so as to simulate the normal rainfall receivingin the area. Methods were standardized for estimationresidues in soil and water samples using the gaschromatograph. Soil samples from different layers(top 5 segments of 2 cm each) leachate wereanalysed for herbicide residues. Average values ofresidues from three replications were worked out forcomparison of data.
Extraction and estimation of 2,4-D residues Water samples were filtered out of any
particulate matter. A 50 mL portion of the sample wastaken and saturated with sodium chloride. The pHwas adjusted to <2 with HCl. It was then extractedwith (5 x 25 mL) portions of acetonitrile. The pooledextract was then concentrated to 15 mL. Fifteen mL10% NaOH was added and the pH was adjusted to >13. The organic phase was evaporated off inpresence of the alkali. The aqueous alkaline solutionwas refluxed for 20 min. It was then cooled andextracted with equal volume of hexane (x3). Thehexane fraction was discarded and the aqueousportion was acidified with HCl to pH<2. It was thenextracted with equal volumes of diethyl ether (x3)
Twenty five gram of wet soil sample afterdraining excess water by spreading over a filter paperwas shaken on a shaker with 80 m. extractingmixture (acetonitrile: water: glacial acetic acid in theratio 80:20:25) for a period of 30 minutes at 220 rpmand filtered through Whatman No.1 filter paper. Thefiltrate was acidified with concentrated HCl (15 mL)and separated by extracting thrice each with 50 mLdiethyl ether.
From the combined diethyl ether extract, theorganic phase was evaporated off and the residuewas dissolved in 3 mL of methanol. Added a 3mlportion of boron tri fluoride methanol reagent andrefluxed for 10 minutes on a water bath. Afterreaction, excess alcohol was evaporated off and20mL water was added, shaken vigorously for 5 min.and extracted with hexane (3x10mL). The hexaneportions were combined, the organic phaseevaporated off and the residue was concentrated
A 5 cm bed of activated silica gel Pyrex glasscolumn packed at the two ends each with 1g ofanhydrous sodium sulfate was used. The column waswashed with 25 mL hexane. The extract obtainedafter derivatisation as given in step II was placed onthe column. The residue in the column was washedwith 100 mL solvent system containing (70% hexane/
30% dichloromethane). It was then eluted with 100mL of (70% dichloromethane/30% hexane) solventmixture. First 20 mL was discarded and next 80 mLwas collected. The solvent was then evaporated offand the residue was dissolved in 1 mL n-hexane.
One micro litre of n- hexane extract was injectedin to the GC 2010 fitted with a 63Ni electron capturedetector, a DB-17 capillary column and a splitinjector. The temperature of the injector, column anddetector were 180, 210 and 3000 C, respectively witha split ratio of 3:1. The residue content was calculatedfrom the standard curve obtained with the referencestandard.
Air dried soil sample (15 g, 2 mm sieved) wasthoroughly mixed with 10g of anhydrous sodiumsulphate, 2 g of florisil (60-100 mesh size) and 0.3gof activated charcoal. A glass column of 30 cm lengthand 2 cm internal diameter was taken. Anhydroussodium sulphate of 3 cm layer was put on the nonadsorbent cotton kept at the lower end of the column.Then the soil sample mixture (prepared as above) wasadded to the column and another layer of anhydroussodium sulphate of 1 cm was put over this layer. Theherbicide was extracted with 100 mL of hexanes:acetone mixture (9:1) and excess solvent wasevaporated under vacuum to one mL. The evaporatedsample was made up to 5 mL with n-hexane. Onemicro litre portion of the n- hexane extract wasinjected in to the GC 2010 fitted with a 63 Ni electroncapture detector, a BPX-5 capillary column and a splitinjector. The temperature conditions for butachlorand petilachlor were the same (250, 220 and 3000Cfor injector, column and the detector wererespectively). For oxyfluorfen, optimum temperatureconditions were 220, 210 and 2400C for injector,column and the detector respectively). The residuecontent was calculated from the standard curveobtained with the reference material (97% purereference standards obtained from Dr. Ehrenstorfer,GmbH, Germany)
Gas chromatographic technique (KAU 2008)was used for estimation of butachlor, pretilachlor andoxyfluorfen residues in the leachate.
RESULTS AND DISCUSSION
Physicochemical characteristics of the soilThe major physico-chemical characteristics of
soil, viz. soil texture, pH, cation exchange capacity(CEC), anion exchange capacity (AEC) and organiccarbon content of the soil sample taken from the ricefield before conducting experiment are presented in(Table 1).
Leaching behaviour of four herbicides in two soils of Kerala
195
The soils showed wide differences in theirtextural characteristics. The mean clay content variedfrom 25.98% (Type I) to 64.00% (Type II). Theorganic carbon content of Type I soil (Mannuthy)was 0.90% and that of Type II (Alappad) was 1.87%.The soils were uniformly acidic in nature (5.1).Cation and anion exchange capacities showedvariations between the soil types (9.25 to 15.75. mol
(+)/kg and 9.38 to 12.4 C mol (-)/kg respectively).Sesquioxide content varied from 3.0 to 4.60 per centbetween the soil types.
Herbicide residues at different soil depthsAll the herbicides registered maximum quantity
of residue in the upper 2 cm of the soil column.Maximum value was registered by butachlor
treatment (2.43 µg/g) in Type II soil and oxyfluorfenregistered lowest value in both the soil types (0.55and 0.61µg/g for Type I and Type II, respectively).This could be attributed to the differences in the levelsof application of herbicides to the columns. Therecommended level of application of butachlorwas1.25 kg/ha and that of oxyfluorfen was 0.20 kg/ha (KAU 2011). Higher proportion of appliedpretilachlor compared to butachlor observed in theupper layer of soil column could be attributed tohigher Kd (distribution coefficient) values forpretilachlor as reported by Hasna (2011).
There was considerable decrease in the residuewith increasing depth of the soil. Fine texturedorganic matter rich soil recorded lower residue levels
Table 1. Major physico chemical characteristics of thesoil columns collected for the study
Table 2. Leaching pattern of butachlor, pretilachlor oxyfluorfen and 2,4-D, in different soil types
Percentage of the applied herbicide remaining at different depths is given in parentheses; BDL: Below detectable level
Characteristics
Soil type (average values) Type I (Mannuthy) coarse textured low organic matter soil sandy loam- ultisol
Type II (Alappad) fine textured high organic matter soil- clay- inceptisol
Clay % 26.0 64.0 Organic carbon, % 0.90 1.87 pH 5.09 5.1 C.E.C, C mol(+)/kg 9.25 15.7 A.E.C, C mol(-)/kg 12.4 9.38 Sesquioxide, % 4.6 3.0
Herbicide and level of application (kg/ha)
Depth of soil (cm)
Concentration of herbicide (µg/g or µg/ mL)
Coarse textured low organic matter soil Fine textured high organic matter soil Butachlor (1.25) 0-2 1.47 (35.28) 2.43 (58.32) 2-4 0.25 (6.0) 0.77 (18.48) 4-6 0.15 (3.6) 0.14 (3.36) 6-8 0.05 (1.2) 0.02 (0.48) 8-10 0.05 (1.2) 0.02 (0.48) Leachate 0.16 (3.84) (>60 cm depth) 0.04 (0.96) (>30 cm depth) Pretilachlor (0.75) 0-2 1.56 (62.4) 1.85 (74.0) 2-4 0.19 (7.6) 0.21 (8.4) 4-6 0.09 (3.6) 0.09 (3.6) 6-8 0.06 (2.4) 0.03 (1.2) 8-10 0.03 (1.2) 0.01 (0.4) Leachate 0.006 (0.24) (>60 cm depth) 0.004 (0.16) (>30 cm depth) Oxyfluorfen (0.20) 0-2 0.55 (82.5) 0.61 (91.5) 2-4 0.005 (0.75) 0.004 (0.6) 4-6 0.005(0.75) 0.002 (0.3) 6-8 0.003 (0.45) BDL 8-10 0.003(0.45) BDL
Leachate BDL(>60 cm depth) BDL(>30 cm depth) 2,4-D (1.0) 0-2 1.44 (43.2) 1.83(54.9) 2-4 0.17(5.1) 0.19 (5.7) 4-6 0.10 (3.0) 0.16(4.8) 6-8 0.08 (2.4) 0.10 (3.0) 8-10 0.05(1.5) 0.09(2.7) Leachate 0.20 (6.0) (>60 cm depth) 0.05 (1.5) (>30 cm depth)
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compared to the soil with coarse texture and poororganic matter. It could be attributed to the highadsorptive power of the soil, especially at the toplayers with high organic matter content.
Based on the quantity sprayed over the soilcolumn, percentage of applied herbicide remaining ineach layer of soil was calculated (Table 2). It could benoticed that oxyfluorfen is more strongly adsorbed inthe first soil layer of 0-2 cm (82.5% and 91.5% of theapplied herbicide in Type I and Type II soil,respectively) followed by pretilachlor (62.4 and74.0%, respectively), 2,4-D (43.2% in Type I soil)and butachlor (35.28% in Type I soil). In Type II soil,butachlor (58.32%) adsorption was higher than thatof 2,4-D (54.9%). As reported by Hasna (2011),higher quantity of organic matter resulted inconsiderable increase in the adsorption of butachlor inthe lateritic soil of Kerala.
Herbicide residues in the leachateAmong the four herbicides tested, 2,4-D residue
was the maximum in the leachate (Table 2) followedby butachlor, pretilachlor and oxyfluorfen. Theleachate collected at 30 cm depth in Type II soilregistered 2,4-D residues to an extent of 0.05 µg/mL(1.50% of the applied herbicide). In the case of TypeI soil 2,4 D residues registered in the leachate at 60cm depth was 0.2 µg/mL (6.0%). Oxyfluorfenresidues in the leachate collected from both the soiltypes were below the detectable level. The resultsindicated that the mobility of oxyfluorfen was very
low in both the soil types and may not contaminategroundwater under recommended rate of applicationof the herbicide. Similar findings were reported byYen et al. (2003) after evaluating the possiblecontamination of oxyfluorfen using the behaviorassessment model and the groundwater pollution-potential (GWP) model. The present study alsorevealed that the solubility of herbicide in water is themajor factor determining the movement of herbicidesin the soils of Kerala. The extent of leaching followedthe order: 2,4-D (620 mg/L) >butachlor (50 mg/L) >pretilachlor(20 mg/L) > oxyfluorfen (0.114mg/L).
REFERENCESAnderson WP. 1983. Weed Science. Principles and Practices.
Second edition. West Publishing Co., NY.Hasna K. 2011. Influence of Organic Matter and Soil Moisture
on the Adsorption of Chloroacetanilide Herbicides, viz.,Butachlor and Pretilachlor, in Laterite Soil. M.Sc. thesis,Kerala Agricultural University, Kerala, India, 91p.
KAU [Kerala Agricultural University]. 2008. Annual Report2008. All India Coordinated Research Programme on WeedControl. Kerala Agricultural University, Kerala, India, 80p.
KAU [Kerala Agricultural University]. 2011. Package ofPractices Recommendations: Crops, 14th edition. Crops.Kerala Agricultural University, Thrissur, 337 p.
RSC, 1987. Agro Chemical Hand book (Ed. Hartley D). Secondedition. The Royal Society of Chemistry, Notingham, UK.
Yen JH, Sheu WS and Wang YS. 2003. Dissipation of theherbicide oxyfluorfen in subtropical soils and its potentialto contaminate groundwater. Ecotoxicology andEnvironmental Safety 54(2):151-6.
Leaching behaviour of four herbicides in two soils of Kerala
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Indian Journal of Weed Science 47(2): 193–196, 2015
Leaching behaviour of four herbicides in two soils of Kerala
K.M. Durga Devi*, C.T. Abraham and C.N. UpasanaCollege of Horticulture, Kerala Agricultural University, Thrissur, Kerala 680 656
Received: 7 April 2015; Revised: 23 May 2015
ABSTRACTThe present study was conducted to find out the extent of leaching of butachlor, pretilachlor, 2,4-D andoxyfluorfen in two soil types, viz. Type I [coarse textured low organic matter soil (Mannuthy–Ultisol] andType II [fine textured high organic matter soil (Alappad-Inceptisol]. Intact soil columns were collectedfrom the paddy fields after the harvest of second crop. Butachlor, pretilachlor, 2,4-D and oxyfluorfen wereapplied in moist soil columns at the recommended rate of application. Soil samples from different depthsup to 10 cm (top 5 segments of 2 cm each) and the leachate at 30 and 60 cm depths were analyzed forherbicide residues using gas chromatography. Among the four herbicides tested, 2,4-D registeredhighest level of residue in the leachate (0.20 ppm at 60 cm depth). Pretilachlor and butachlor followed thesame trend in the pattern of movement of residue through the soil columns. However, the leachate ofpretilachlor registered much lower quantity of residue (0.006 ppm). Fine textured organic matter rich soilrecorded lower residue levels compared to the soil with coarse texture and poor organic matter. It couldbe attributed to the high adsorptive power of the soil, especially at the top layers with high organic mattercontent. Oxyfluorfen residues could not be detected in the leachate, because of its poor water solubility.
Key words: 2,4-D, Butachlor, Leaching, Oxyfluorfen, Pretilachlor
Among the different pre-emergence herbicidesin rice, butachlor, pretilachlor and oxyfluorfen aremore popular in the paddy fields of Kerala. Sodiumsalt of 2, 4-D is the most common post-emergenceherbicide in the major rice bowls of the state, viz.Kole and Kuttanad. Herbicide movement in soils is ofmajor concern in tropical soils with heavy rainfall.Since these herbicides are applied to the soil surfacewithout incorporation, heavy rainfall soon afterapplication may cause excessive leaching of theherbicide from the surface zone, resulting in poorweed control. In the case of herbicides with high soilmobility, leaching may lead to injury of deeper-rooteddesirable species. In addition, herbicide leaching mayresult in contamination of ground and surface water(Anderson 1983). Movement of herbicide within thesoil profile is influenced by many factors such aschemical nature of herbicide, the adsorptive capacityof soil and the amount of water available fordownward movement through the soil. Butachlor,pretilahlor, oxyfluorfen and 2,4-D differ much in theirwater solubility (RSC 1987). Considering thesefactors, studies on leaching pattern of three pre-emergence herbicides and one post-emergenceherbicide were conducted in two soil types of Kerala,under All India Coordinated Research Programme onWeed Control during the period from 2007-08 to2010-11.
MATERIALS AND METHODSIntact soil columns were collected from two soil
types, viz. Type I (sandy loam low organic matter soilof Ultisol order at Rice field of Agricultural Researchstation, Mannuthy) and Type II (high organic matterclayey soil of Inceptisol order, Kole Lands, Alappad)after the harvest of second crop. Long PVC tubes (60cm) of 16 cm diameter were taken for Type I soil.Tubes of only 30 cm and 16 cm diameter were takenfor Type II soil because the area is below mean sealevel and hence collection of intact soil columnsbelow 30 cm was not possible. The tubes were cutvertically and the two halves were pressed onto thelateral sides of the soil pit of 60 cm deep, dug in therice field. The soil corresponding to the differentdepths were transferred as such to the two halves ofthe PVC column and they were joined together usingadhesive tape. The tube was kept on an iron standafter tying the lower end with a muslin cloth. Afteradding water continuously to attain constantpercolation rate, the herbicides were added at therecommended rate of application, viz.1.25 , 0.75, 1.0and 0.2 kg/ha for butachlor (Machete®), pretilachlor(Rifit®), 2,4-D (Fernoxone®) and oxyfluorfen(Goal®), respectively using a spray volume of 500 L/ha. The quantity of solution required for spraying wascalculated based on the surface area.
*Corresponding author: [email protected]
194
Water was added frequently to the top of thecolumn at one day after spraying. A total of 1000 mLwater was added through the column (200 mL x 5times) so as to simulate the normal rainfall receivingin the area. Methods were standardized for estimationresidues in soil and water samples using the gaschromatograph. Soil samples from different layers(top 5 segments of 2 cm each) leachate wereanalysed for herbicide residues. Average values ofresidues from three replications were worked out forcomparison of data.
Extraction and estimation of 2,4-D residues Water samples were filtered out of any
particulate matter. A 50 mL portion of the sample wastaken and saturated with sodium chloride. The pHwas adjusted to <2 with HCl. It was then extractedwith (5 x 25 mL) portions of acetonitrile. The pooledextract was then concentrated to 15 mL. Fifteen mL10% NaOH was added and the pH was adjusted to >13. The organic phase was evaporated off inpresence of the alkali. The aqueous alkaline solutionwas refluxed for 20 min. It was then cooled andextracted with equal volume of hexane (x3). Thehexane fraction was discarded and the aqueousportion was acidified with HCl to pH<2. It was thenextracted with equal volumes of diethyl ether (x3)
Twenty five gram of wet soil sample afterdraining excess water by spreading over a filter paperwas shaken on a shaker with 80 m. extractingmixture (acetonitrile: water: glacial acetic acid in theratio 80:20:25) for a period of 30 minutes at 220 rpmand filtered through Whatman No.1 filter paper. Thefiltrate was acidified with concentrated HCl (15 mL)and separated by extracting thrice each with 50 mLdiethyl ether.
From the combined diethyl ether extract, theorganic phase was evaporated off and the residuewas dissolved in 3 mL of methanol. Added a 3mlportion of boron tri fluoride methanol reagent andrefluxed for 10 minutes on a water bath. Afterreaction, excess alcohol was evaporated off and20mL water was added, shaken vigorously for 5 min.and extracted with hexane (3x10mL). The hexaneportions were combined, the organic phaseevaporated off and the residue was concentrated
A 5 cm bed of activated silica gel Pyrex glasscolumn packed at the two ends each with 1g ofanhydrous sodium sulfate was used. The column waswashed with 25 mL hexane. The extract obtainedafter derivatisation as given in step II was placed onthe column. The residue in the column was washedwith 100 mL solvent system containing (70% hexane/
30% dichloromethane). It was then eluted with 100mL of (70% dichloromethane/30% hexane) solventmixture. First 20 mL was discarded and next 80 mLwas collected. The solvent was then evaporated offand the residue was dissolved in 1 mL n-hexane.
One micro litre of n- hexane extract was injectedin to the GC 2010 fitted with a 63Ni electron capturedetector, a DB-17 capillary column and a splitinjector. The temperature of the injector, column anddetector were 180, 210 and 3000 C, respectively witha split ratio of 3:1. The residue content was calculatedfrom the standard curve obtained with the referencestandard.
Air dried soil sample (15 g, 2 mm sieved) wasthoroughly mixed with 10g of anhydrous sodiumsulphate, 2 g of florisil (60-100 mesh size) and 0.3gof activated charcoal. A glass column of 30 cm lengthand 2 cm internal diameter was taken. Anhydroussodium sulphate of 3 cm layer was put on the nonadsorbent cotton kept at the lower end of the column.Then the soil sample mixture (prepared as above) wasadded to the column and another layer of anhydroussodium sulphate of 1 cm was put over this layer. Theherbicide was extracted with 100 mL of hexanes:acetone mixture (9:1) and excess solvent wasevaporated under vacuum to one mL. The evaporatedsample was made up to 5 mL with n-hexane. Onemicro litre portion of the n- hexane extract wasinjected in to the GC 2010 fitted with a 63 Ni electroncapture detector, a BPX-5 capillary column and a splitinjector. The temperature conditions for butachlorand petilachlor were the same (250, 220 and 3000Cfor injector, column and the detector wererespectively). For oxyfluorfen, optimum temperatureconditions were 220, 210 and 2400C for injector,column and the detector respectively). The residuecontent was calculated from the standard curveobtained with the reference material (97% purereference standards obtained from Dr. Ehrenstorfer,GmbH, Germany)
Gas chromatographic technique (KAU 2008)was used for estimation of butachlor, pretilachlor andoxyfluorfen residues in the leachate.
RESULTS AND DISCUSSION
Physicochemical characteristics of the soilThe major physico-chemical characteristics of
soil, viz. soil texture, pH, cation exchange capacity(CEC), anion exchange capacity (AEC) and organiccarbon content of the soil sample taken from the ricefield before conducting experiment are presented in(Table 1).
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195
The soils showed wide differences in theirtextural characteristics. The mean clay content variedfrom 25.98% (Type I) to 64.00% (Type II). Theorganic carbon content of Type I soil (Mannuthy)was 0.90% and that of Type II (Alappad) was 1.87%.The soils were uniformly acidic in nature (5.1).Cation and anion exchange capacities showedvariations between the soil types (9.25 to 15.75. mol
(+)/kg and 9.38 to 12.4 C mol (-)/kg respectively).Sesquioxide content varied from 3.0 to 4.60 per centbetween the soil types.
Herbicide residues at different soil depthsAll the herbicides registered maximum quantity
of residue in the upper 2 cm of the soil column.Maximum value was registered by butachlor
treatment (2.43 µg/g) in Type II soil and oxyfluorfenregistered lowest value in both the soil types (0.55and 0.61µg/g for Type I and Type II, respectively).This could be attributed to the differences in the levelsof application of herbicides to the columns. Therecommended level of application of butachlorwas1.25 kg/ha and that of oxyfluorfen was 0.20 kg/ha (KAU 2011). Higher proportion of appliedpretilachlor compared to butachlor observed in theupper layer of soil column could be attributed tohigher Kd (distribution coefficient) values forpretilachlor as reported by Hasna (2011).
There was considerable decrease in the residuewith increasing depth of the soil. Fine texturedorganic matter rich soil recorded lower residue levels
Table 1. Major physico chemical characteristics of thesoil columns collected for the study
Table 2. Leaching pattern of butachlor, pretilachlor oxyfluorfen and 2,4-D, in different soil types
Percentage of the applied herbicide remaining at different depths is given in parentheses; BDL: Below detectable level
Characteristics
Soil type (average values) Type I (Mannuthy) coarse textured low organic matter soil sandy loam- ultisol
Type II (Alappad) fine textured high organic matter soil- clay- inceptisol
Clay % 26.0 64.0 Organic carbon, % 0.90 1.87 pH 5.09 5.1 C.E.C, C mol(+)/kg 9.25 15.7 A.E.C, C mol(-)/kg 12.4 9.38 Sesquioxide, % 4.6 3.0
Herbicide and level of application (kg/ha)
Depth of soil (cm)
Concentration of herbicide (µg/g or µg/ mL)
Coarse textured low organic matter soil Fine textured high organic matter soil Butachlor (1.25) 0-2 1.47 (35.28) 2.43 (58.32) 2-4 0.25 (6.0) 0.77 (18.48) 4-6 0.15 (3.6) 0.14 (3.36) 6-8 0.05 (1.2) 0.02 (0.48) 8-10 0.05 (1.2) 0.02 (0.48) Leachate 0.16 (3.84) (>60 cm depth) 0.04 (0.96) (>30 cm depth) Pretilachlor (0.75) 0-2 1.56 (62.4) 1.85 (74.0) 2-4 0.19 (7.6) 0.21 (8.4) 4-6 0.09 (3.6) 0.09 (3.6) 6-8 0.06 (2.4) 0.03 (1.2) 8-10 0.03 (1.2) 0.01 (0.4) Leachate 0.006 (0.24) (>60 cm depth) 0.004 (0.16) (>30 cm depth) Oxyfluorfen (0.20) 0-2 0.55 (82.5) 0.61 (91.5) 2-4 0.005 (0.75) 0.004 (0.6) 4-6 0.005(0.75) 0.002 (0.3) 6-8 0.003 (0.45) BDL 8-10 0.003(0.45) BDL
Leachate BDL(>60 cm depth) BDL(>30 cm depth) 2,4-D (1.0) 0-2 1.44 (43.2) 1.83(54.9) 2-4 0.17(5.1) 0.19 (5.7) 4-6 0.10 (3.0) 0.16(4.8) 6-8 0.08 (2.4) 0.10 (3.0) 8-10 0.05(1.5) 0.09(2.7) Leachate 0.20 (6.0) (>60 cm depth) 0.05 (1.5) (>30 cm depth)
K.M. Durga Devi, C.T. Abraham and C.N. Upasana
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compared to the soil with coarse texture and poororganic matter. It could be attributed to the highadsorptive power of the soil, especially at the toplayers with high organic matter content.
Based on the quantity sprayed over the soilcolumn, percentage of applied herbicide remaining ineach layer of soil was calculated (Table 2). It could benoticed that oxyfluorfen is more strongly adsorbed inthe first soil layer of 0-2 cm (82.5% and 91.5% of theapplied herbicide in Type I and Type II soil,respectively) followed by pretilachlor (62.4 and74.0%, respectively), 2,4-D (43.2% in Type I soil)and butachlor (35.28% in Type I soil). In Type II soil,butachlor (58.32%) adsorption was higher than thatof 2,4-D (54.9%). As reported by Hasna (2011),higher quantity of organic matter resulted inconsiderable increase in the adsorption of butachlor inthe lateritic soil of Kerala.
Herbicide residues in the leachateAmong the four herbicides tested, 2,4-D residue
was the maximum in the leachate (Table 2) followedby butachlor, pretilachlor and oxyfluorfen. Theleachate collected at 30 cm depth in Type II soilregistered 2,4-D residues to an extent of 0.05 µg/mL(1.50% of the applied herbicide). In the case of TypeI soil 2,4 D residues registered in the leachate at 60cm depth was 0.2 µg/mL (6.0%). Oxyfluorfenresidues in the leachate collected from both the soiltypes were below the detectable level. The resultsindicated that the mobility of oxyfluorfen was very
low in both the soil types and may not contaminategroundwater under recommended rate of applicationof the herbicide. Similar findings were reported byYen et al. (2003) after evaluating the possiblecontamination of oxyfluorfen using the behaviorassessment model and the groundwater pollution-potential (GWP) model. The present study alsorevealed that the solubility of herbicide in water is themajor factor determining the movement of herbicidesin the soils of Kerala. The extent of leaching followedthe order: 2,4-D (620 mg/L) >butachlor (50 mg/L) >pretilachlor(20 mg/L) > oxyfluorfen (0.114mg/L).
REFERENCESAnderson WP. 1983. Weed Science. Principles and Practices.
Second edition. West Publishing Co., NY.Hasna K. 2011. Influence of Organic Matter and Soil Moisture
on the Adsorption of Chloroacetanilide Herbicides, viz.,Butachlor and Pretilachlor, in Laterite Soil. M.Sc. thesis,Kerala Agricultural University, Kerala, India, 91p.
KAU [Kerala Agricultural University]. 2008. Annual Report2008. All India Coordinated Research Programme on WeedControl. Kerala Agricultural University, Kerala, India, 80p.
KAU [Kerala Agricultural University]. 2011. Package ofPractices Recommendations: Crops, 14th edition. Crops.Kerala Agricultural University, Thrissur, 337 p.
RSC, 1987. Agro Chemical Hand book (Ed. Hartley D). Secondedition. The Royal Society of Chemistry, Notingham, UK.
Yen JH, Sheu WS and Wang YS. 2003. Dissipation of theherbicide oxyfluorfen in subtropical soils and its potentialto contaminate groundwater. Ecotoxicology andEnvironmental Safety 54(2):151-6.
Leaching behaviour of four herbicides in two soils of Kerala
IMPACT OF VARIOUS DOSES OF BUTACHLOR ON WEED
GROWTH, CROP YIELD OF RICE, MICROBIAL POPULATION
AND RESIDUAL EFFECT ON WHEAT CROP V. Pratap Singh, Neeshu Joshi, Neema Bisht, A. Kumar, Kavita Satyawali
and R.P. Singh
Department of Agronomy, College of Agriculture,
G.B. Pant University of Agriculture and Technology, Pantnagar
E-mail: [email protected]
Abstract: A field investigation was carried to test the bioefficacy of Butachlor 50 EC at
various doses (Sponsor Vs market sample) to control the weeds in transplanted rice.
Butachlor was applied at various doses as pre emergence and its market sample used at two
doses, almix also applied as post emergence. All weed control treatments significantly
reduced the density as well as dry matter accumulation of weeds over weedy check during
both the years. The maximum suppression of density as well as dry matter accumulation of
weeds and highest WCE were obtained with application of Butachlor 50% EC at higher doses
(2000 and 4000 g/ha) as compared to its lower dose 1250 g/ha. Among herbicidal treatments
maximum grain (4479 and 5056 kg/ha) and straw (7370 and 6963 kg/ha) yield was achieved
by the application of Butachlor 50 EC (SS) at 2000 g/ha applied as pre emergence during
both the years.
Keywords: Bio-efficacy, Butachlor, microbial, residual and transplanted rice.
Introduction
Rice (Oryza sativa L.) is a staple food for more than 60% of the world’s population. Feeding
the 9 billion people expected to inhabit our planet by 2050 will be an unprecedented
challenge for the mankind. In India, rice is cultivated in an area of 44.07 m ha annually with a
production of 103.40 mt, with an average productivity only 2.3 t/ha (FAO, 2012). There are
several reasons for low productivity, however it has been estimated that without weed
control, the yield loss can be as high as upto 90%. Weeds have caused yield reduction of 28
to 45% in transplanted rice (Singh et al., 2007; Manhas et al., 2012). High density of grassy
weeds competing with crop and resulting into heavy yield losses up to 40-50% (Singh et al.,
2004). Furthermore, any delay in weeding will lead to increased weed biomass which has a
negative correlation with yield. The reduction in weed growth was observed with intensive
puddling and shallow depth submergence in transplanted rice (Reddy and Reddy, 1999).
Transplanted rice faces diverse type of weed flora, consisting of grasses, broad-leaf weeds
International Journal of Science, Environment ISSN 2278-3687 (O)
and Technology, Vol. 5, No 5, 2016, 3106 – 3114 2277-663X (P)
Received Aug 24, 2016 * Published Oct 2, 2016 * www.ijset.net
3107 V. Pratap Singh, Neeshu Joshi, Neema Bisht, A. Kumar, Kavita Satyawali and R.P. Singh
and sedges. Weed competition brings reduction in yield of transplanted rice by about 50 per
cent (Mukherjee and Singh, 2005).
Manual weeding is although effective and most common method, however, scarcity and high
wages of labor particularly during peak period of critical competition between weed and crop
period make this method uneconomical. The goal of herbicide use is to kill or stunt weed
infestation allowing the rice to grow and gain a competitive advantage. Weeds are the most
important biological constraint to decrease the yield of rice. Now chemical weed control
method is becoming popular among the farmers because it is the most efficient means of
reducing weeds competition with minimum labor cost. Butachlor, anilofos, oxadiargyl, etc.
are the herbicides presently use for weed control in transplanted rice. Weed density per unit
area is an important and key parameter in figuring out the impact of treatments on weed
growth. Moreover, the use of herbicides, though discouraged worldwide these days because
of environmental and health hazards, is inevitable due to many reasons particularly in the
terms of economics and the immediate effect. Bio-efficacy of herbicides is also depends on
herbicide doses and affect the crop physiology, soil health and residue effect on succeeding
crop. With this thought keeping in background, the present research work on bio-efficacy of
butachlor 50% EC of sponsor Vs market samples tested in transplanted rice to find out the
herbicide efficacy at various doses and its impact on crop and soil health along with
carryover of residues in succeeding wheat crop.
Materials and Methods
The field experiment was conducted at N.E. Borlaug Crop Research Centre of G.B. Pant
University of Agriculture and Technology, Pantagar during two consecutive year of 2010-11
and 2011-12. The Crop Research Centre where the experiment was conducted is located at
29o N latitude, 79.3
o E longitude, and at an altitude of 283.84 metres above the mean sea
level. The soil was loamy, medium in organic matter (0.67%), available phosphorus (17.5
kg/ha) and potassium (181.2 kg/ha) with pH 7.5. The experiment consisted of eight
treatments including untreated (control) and laid out in randomized block design (RBD) with
three replications. The treatments were as follows of Butachlor 50% EC (sponsor sample) at
1250, 2000, 4000 g/ha and two doses of market sample at 1250 and 2000 g/ha applied as pre
emergence, Almix 20%WP at 4 g/ha applied as post emergence to required volume of water
500 l/ha. Weed free and weedy check also included in experiment to compare the efficacy of
herbicidal treatments. Rice variety “Sarjoo 52” seedling was planted on June 2 of kharif 2010
and June 10 of kharif 2011. The other agricultural practices used for rice transplanting in the
Impact of Various Doses of Butachlor on Weed …. 3108
region were followed. Knap sack sprayer fitted with boom along with flat fan nozzle was
used to apply the herbicidal solution. The basal dose was applied at the rate of 60:60:40:25
kg/ha of N:P:K and Zn, respectively. Weed were recorded species wise in each plot at 30 and
60 days after transplanting (DAT) with the help of quadrate of 0.25m2
for the area marked for
observation. The weed after uprooting are cleaned and dried in oven at 720C temperature and
weed control efficiency was calculated by using the formula WCE = (weed biomass in
unwedded control– weed biomass in managed treatment)/ weed biomass in unweeded control
x 100. Besides observations for plant height, tillers (number/row), panicles/m2,
grains/panicle, 1000 grain weight, grain and straw yield were taken. Data recorded were
statistically analyzed according to Gomez and Gomez (1984). Means were compared at 5%
levels of significance by the least significant difference (LSD) test.
Result and Discussion
Weed flora
The dominant weed flora of the experimental site at 30 and 60 DAT was similar during both
years and comprised of grasses; Echinochloa colona, Echinochloa crusgalli, broad leaf
weeds; Ammania baccifera, Caesulia auxillaris, Alternanthera sessilis and Cyperus spp. was
the only species among the sedge.
Effect on weeds
Weed density and weed dry matter varied significantly under different herbicidal treatments
(Table 1&2). Data presented in Table 1&2 indicated that all the herbicidal treatments
significantly reduced the density and dry matter accumulation of weeds with increasing the
dose of Butachlor 50% EC (Sponsor sample) as compared to market sample of Butachlor
50% EC at both stages during both the years except at 30 DAA in 2010 over the weedy check
and thus ultimately enhanced weed control efficiency. Prakash et al., 2013 also observed that
Butachlor 1500 g/ha significantly reduced the density and dry weight of weeds over weedy
check (control). Maximum reduction in weed density and dry weight of weeds was obtained
with application of Butachlor 50% EC (SS) 4000 g/ha followed by its lower dose 2000 g/ha.
Application of Butachlor 50% EC at 1250 and 2000 g/ha (SS) was found more effective in
reducing the population of grassy weeds over the market sample of butachlor at same doses.
Weed dry matter is a better parameter to measure the competition than the weed number
(Bhanumurthy and Subramanian, 1989). The total dry matter accumulation of weeds reduced
is an indication of the overall utilization of resources and better light interception.
Application of Butachlor either SS or MS both significantly reduced weed population as well
3109 V. Pratap Singh, Neeshu Joshi, Neema Bisht, A. Kumar, Kavita Satyawali and R.P. Singh
as weeds dry matter accumulation found in rice crop over weedy check during both the years
of experimentation. The lower weed dry weight in weed control treatments may be ascribed
to lesser number of weeds, rapid depletion of carbohydrates reserves of weeds through rapid
respiration (Hill and Santlemann, 1969). Among various herbicides, Butachlor 50% EC (SS)
at 4000 g/ha recorded the lowest weed dry matter accumulation followed by its lower dose at
2000 g/ha at both the stages of crop growth due to elimination of both grassy and non-grassy
weeds resulting in maximum weed control efficiency. While Almix 20% WP 4 g/ha was least
effective with lowest weed control efficiency as it was not effectively control the grassy
weeds.
3110
Table 1: Effect of treatments on density and total dry weight of weeds at 30 DAA during 2010 and 2011 Treatments Dose
(g/ha)
2010 2011
Weed density (no./m2) at 30 DAA
To
tal
wee
d d
ry
Wei
gh
t (g
/m2) Weed density (no./m
2) at 30 DAA
To
tal
wee
d d
ry
wei
gh
t (
g/m
2)
E.
colo
na
E. cr
usg
all
i
I. r
ugosu
m
A. basi
fera
C. axil
lari
s
A.
sess
ali
s
Cyp
eru
s
spp.
E.
colo
na
E. cr
usg
all
i
I. r
ugosu
m
A. basi
fera
C. axil
lari
s
A.
sess
ali
s
Butachlor50% EC(SS) 1250 1.1(2.7) 2.1(8.0) 0.0(0.0) 0.0(0.0) 1.5(5.3) 2.7(13.3) 0.0(0.0) 14.8 1.0(2.7) 0.5(1.3) 0.0(0.0) 1.0(2.7) 2.3(9.3) 0.0(0.0) 27.1
Butachlor 50% EC (SS) 2000 0.0(0.0) 1.3(4.0) 0.0(0.0) 0.0(0.0) 0.0(0.0) 2.4(10.7) 0.0(0.0) 13.4 0.5(1.3) 0.0(0.0) 0.0(0.0) 1.0(2.7) 2.1(8.0) 0.0 (0.0) 22.7
Butachlor 50% EC (SS) 4000 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.7(2.7) 2.3(9.3) 0.0(0.0) 7.6 0.5(1.3) 0.0(0.0) 0.0(0.0) 0.5(1.3) 2.3(9.3) 0.0(0.0) 19.4
Butachlor 50% EC (MS) 1250 0.0(0.0) 2.9(17.3) 0.0(0.0) 0.0(0.0) 0.0(0.0) 2.6(12.0) 0.0(0.0) 14.8 1.0(2.7) 1.6(4.0) 0.0(0.0) 1.0(2.7) 2.1(8.0) 1.0(2.7) 27.6
Butachlor 50% EC (MS) 2000 0.0(0.0) 1.3(4.0) 0.0(0.0) 0.0(0.0) 0.5(1.3) 2.7(13.3) 0.5(1.3) 12.7 0.5(1.3) 0.5(1.3) 0.0(0.0) 1.0(2.7) 2.3(9.3) 0.0(0.0) 22.9
Almix 20% WP 4 3.1(21.3) 4.0(52.0) 2.9(17.3) 0.0(0.0) 2.2(8.0) 2.1(8.0) 2.5(12.0) 35.0 1.8(5.3) 2.8(16.0) 0.0(0.0) 0.0(0.0) 1.4(5.3) 0.0(0.0) 52.8
Weed free - 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.0 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.0
Weedy - 4.5(88.0) 4.4(82.7) 1.5(5.3) 1.5(5.3) 0.0(0.0) 0.7(2.7) 3.4(29.3) 84.3 2.1(7.3) 3.0(21.3) 1.7(4.7) 2.4(10.7) 2.7(14.7) 3.1(21.3) 93.2
LSD(0.05) 0.5 1.1 1.1 0.8 1.3 0.9 0.6 12.3 1.1 0.8 0.1 1.2 0.8 0.5 6.9
SS- Sponsor sample, MS – Market sample, Values in parentheses are original which were transformed to log (X+1) for analysis, DAA- days after herbicide application.
Table 2: Effect of treatments on density and dry weight of weeds at 60 DAA during 2010 and 2011 2010 2011
Treatments Dose
(g/ha)
Weed density (no./m2) at 60 DAA
To
tal
wee
d d
ry
Wei
gh
t (g
/m2) Weed density (no./m
2) at 60 DAA
To
tal
wee
d
dry
wei
gh
t
(g/m
2)
E.
colo
na
E.
cru
sgall
i
A.
basi
fera
C.
axil
lari
s
A.
sess
ali
s
Cyp
eru
s
spp.
E.
colo
na
E.
cru
sgall
i
I.
rugosu
m
A.
basi
fera
C.
axil
lari
s
A.
sess
ali
s
Butachlor50% EC(SS) 1250 0.0 (0.0) 1.3 (4.0) 0.0 (0.0) 0.0 (0.0) 1.1 (2.7) 2.5 (10.7) 41.1 0.7(1.3) 2.1(7.3) 0.7(1.3) 1.3(2.7) 1.6(4.0) 3.1(21.3) 45.5
Butachlor 50% EC (SS) 2000 0.0 (0.0) 1.1 (2.7) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 2.7 (14.7) 12.9 0.0(0.0) 1.7(4.7) 0.0(0.0) 0.0(0.0) 0.5(1.3) 3.2(25.3) 34.0
Butachlor 50% EC (SS) 4000 0.5(1.3) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 2..4(10.7) 12.5 0.0(0.0) 1.0(2.7) 0.0(0.0) 0.0(0.0) 0.0(0.0) 3.2(24.0) 24.9
Butachlor 50% EC (MS) 1250 2.0 (6.7) 2.7(13.3) 0.0 (0.0) 1.1 (2.7) 1.1 (2.7) 2.7 (13.3) 54.1 1.2(2.7) 2.1(8.0) 0.7(1.3) 1.3(2.7) 1.6(4.0) 3.1(22.7) 46.1
Butachlor 50% EC (MS) 2000 1.1 (2.7) 0.7 (2.7) 0.0 (0.0) 0.0 (0.0) 2.0 (6.7) 3.0 (20.0) 42.7 0.7(1.3) 0.0(0.0) 0.0(0.0) 0.0(0.0 0.0(0.0) 3.0(20.0) 36.8
Almix 20% WP 4 2.3 (9.3) 3.9(49.3) 2.0 (6.7) 0.0 (0.0) 0.0 (0.0) 1.1 (2.7) 211.3 0.0(0.0) 2.1(8.0) 1.8(5.3) 0.0(0.0 0.0(0.0) 0.0(0.0) 60.9
Weed free - 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.0 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.0(0.0 0.0(0.0) 0.0(0.0) 0.0
Weedy - 2.5(10.7) 3.9(50.7) 2.0 (6.7) 2.7(14.7) 2.0 (6.7) 2.1 (8.0) 256.5 1.8(5.3) 3.1(21.3) 2.0(6.7) 1.8(5.3) 1.8(5.3) 2.6(17.3) 158.8
LSD(0.05) 0.8 1.3 0.3 0.6 0.8 0.7 29.0 0.5 0.5 0.6 0.3 0.6 0.6 21.6
SS- Sponsor sample, MS – Market sample, Values in parentheses are original which were transformed to log (X+1) for analysis, DAA- days after herbicide application.
3111
SS- Sponsor sample,
All the treatments of weed control increase
the doses of herbicide over weedy check
control efficiency other than weed free treatment
50 EC (SS) at higher dose 4000 g/ha
years.
Table 3. Effect of herbicidal treatments on yield an
Treatments Dose
(g/ha)
Panicles
2010
Butachlor 50% EC
(SS) 1250 147
Butachlor 50% EC
(SS) 2000 163
Butachlor 50% EC
(SS) 4000 162
Butachlor50% EC
(MS) 1250 143
Butachlor50% EC
(MS) 2000 157
Almix 20% WP 4 140
Weed free - 172
Weedy - 134
LSD 16
Effect of herbicides on yield attributes and yield of rice
All the yield attributing characters except 1000 grain weight were influenced significantly
due to various herbicidal treat
0
50
100W
ee
d C
on
tro
l E
ffic
ien
cy (
%)
Fig 1: Effect of different treatments on
WCE at 60 DAA during 2010 and 2011
Sponsor sample, MS – Market sample, DAA- days after herbicide application.
All the treatments of weed control increase the weed control efficiency in respect to increase
the doses of herbicide over weedy check (Fig 1). The results revealed that
other than weed free treatment was obtained with application of
4000 g/ha followed by its lower dose 2000 g/ha
. Effect of herbicidal treatments on yield and yield attributes of rice crop
Panicles/m2 Grains/
panicle
1000 grain
weight(g)
Grain yield
(kg/ha)
2010 2011 2010 2011 2010 2011 2010
147 212 161 130 21.6 23.7 4139
163 237 185 140 22.9 24.1 4479
162 213 146 135 23.0 23.5 4089
143 211 155 127 23.7 23.7 4167
157 215 159 131 24.7 24.0 4427
140 194 153 118 23.4 24.1 3281
172 259 166 143 25.4 23.7 4505
134 172 158 97 23.9 22.7 3015
30 14 18 NS NS 350
Effect of herbicides on yield attributes and yield of rice
All the yield attributing characters except 1000 grain weight were influenced significantly
due to various herbicidal treatments during both years (Table 3). Among the
Treatments
Fig 1: Effect of different treatments on
WCE at 60 DAA during 2010 and 20112010 2011
days after herbicide application.
in respect to increase
. The results revealed that maximum weed
obtained with application of Butachlor
followed by its lower dose 2000 g/ha during both the
d yield attributes of rice crop.
Grain yield
(kg/ha)
Straw yield
(kg/ha)
2010 2011 2010 2011
4139 4650 6771 6663
4479 5056 7370 6963
4089 4812 6589 6760
4167 4583 6406 6500
4427 4928 7084 6917
3281 4349 6271 6322
4505 4974 7451 6988
3015 4096 6302 5390
350 273 525 352
All the yield attributing characters except 1000 grain weight were influenced significantly
. Among the herbicidal
Fig 1: Effect of different treatments on
WCE at 60 DAA during 2010 and 2011
Impact of Various Doses of Butachlor on Weed …. 3112
treatments, the highest value of yield attributing characters viz., panicles/m2 and grains
/panicle was recorded with application of Butachlor 50% EC (SS) at 2000 g/ha during both
years. Grain yield is the principal and primary parameter for assessment of any weed control
treatments applied in experimentations. Data on grain yield revealed that the all executed
treatments out-weighted over the weedy check. Among the herbicidal application, Butachlor
50 EC (SS) 2000 g/ha performed the best by giving the highest grain yield of 4479 and 5056
kg/ha during 2010 and 2011, respectively which was comparable to weed free as well as
butachlor (MS) at 2000 g/ha. During 2010 highest straw yield (7370 kg/ha) was achieved
with the application of butachlor (SS) at 2000g/ha which was found at par with butachlor
(MS) applied at 2000g/ha and weed free while in 2011, it was found maximum (6988 kg/ha)
with weed free situation which was significantly superior to butachlor (MS) applied at 1250
g/ha, almix at 4g/ha and weedy check. The effective control of weeds starting from the early
crop growth stage might have resulted in better growth and yield of rice. The variation in
grain and straw yield under different treatments was the result of variation in weed density
and weed control efficiency. Due to maximum infestation of weeds, the lowest grain yield of
rice was recorded in the untreated control plots.
Effect on microbial activity of soil
A healthy population of soil microorganisms can stabilize the ecological system in soil
(Chauhan et al., 2006) due to their ability to regenerate nutrients to support plant growth. Any
change in their population and activity may affect nutrient cycling as well as availability of
nutrients, which indirectly affect productivity and other soil functions (Wang et al., 2008).
Before herbicidal application the population of bacteria, actinomycetes and fungi was not
significantly affected by the treatments during 2011 while at harvest weed control measures
had no significant effect on the population of bacteria during 2010 as well as on the
population of actinomycetes and fungi during 2011. Maximum bacterial population was
recorded with almix 20% WP at 4 g/ha before application and with butachlor 50% EC (MS)
at the time of harvest which was found superior to all other herbicidal treatments except
butachlor 50% EC (SS) applied at 4000 g/ha. During the year 2010, among herbicidal
treatments, application of butachlor 50% EC (MS) at 1250 g/ha before application and
application of butachlor 50% EC (SS) at 1250 g/ha at harvest achieved highest population of
actinomycetes as well as fungi (Table 4).
3113 V. Pratap Singh, Neeshu Joshi, Neema Bisht, A. Kumar, Kavita Satyawali and R.P. Singh
Table 4: Effect of different treatments on microbial population at different stages
Treatment Doses
(g/ha)
Bacteria 10-7
Actinomycetes 10-5
Fungi 10-4
BA AH BA AH BA AH
2010 2011 2010 2011 2010 2011 2010 2011 2010 2011 2010 2011
Butachlor 50% EC
(SS) 1250 12.7
14.3
8 16.0
22.5
3 12.0
17.2
2 12.7 21.00 3.3
11.4
3 3.7 22.03
Butachlor 50% EC
(SS) 2000 10.7
15.5
1 13.7
21.4
0 10.0
18.7
8 12.0 19.03 2.3
14.6
9 2.3 19.36
Butachlor 50% EC
(SS) 4000 10.3
14.8
3 14.7
17.7
3 8.7
17.6
9 9.4 16.40 1.7
12.7
7 2.0 17.63
Butachlor 50% EC
(MS) 1250 12.0
15.6
7 14.3
23.2
0 12.3
18.8
1 12.4 21.66 4.0
13.9
8 3.3 22.43
Butachlor 50% EC
(MS) 2000 13.0
14.4
9 14.7
21.9
0 9.3
19.2
6 11.7 19.30 2.3
15.3
5 2.7 20.73
Almix 20% WP 4 13.3
13.2
5 14.7
20.2
6 10.7
19.3
6 12.0 20.46 4.0
16.4
0 3.0 21.63
Weed free - 15.3 13.9
1 18.3
20.5
3 12.7
18.7
4 13.4 22.93 4.3
12.7
9 4.0 21.80
Weedy - 14.0 14.3
7 15.7
23.1
0 14.7
16.6
2 15.0 20.46 3.7
16.7
2 4.7 22.76
Sem± - 0.9 1.1 1.5 1.0 0.7 1.0 0.9 1.0 0.5 1.0 0.4 1.1
CD at 5% - 2.9 NS NS 3.2 2.4 NS 2.7 NS 1.5 NS 1.3 NS
BA- before application, AH- at harvest
Effect on succeeding wheat crop
All yield and yield attributing characters were not influenced significantly due to weed
control treatments (Table 5) and they were statistically similar and at par to each other,
including weedy check plots. Pre emergence application of Butachlor (sponsor sample as
well as market sample) against weeds in rice crop during kharif season was safe for growing
wheat crop.
Table 5: Residual effect of herbicides on succeeding crop (wheat)
Treatments Dose
g/ha
Plant
height
(cm)
No.
Spikes (m-2
)
Grains/
spike
1000 grain
weight (g)
Grain yield
(kg/ha)
Straw yield
(kg/ha)
2010 2011 2010 2011 2010 2011 2010 2011 2010 2011 2010 2011
Butachlor 50%
EC (SS) 1250
92.3 91.5
116 255
37.0 57.4
39.8 45.80
4083 3198
5708 6302
Butachlor 50%
EC (SS) 2000
91.0 90.6
108 287
39.5 48.1
43.7 48.75
4150 3283
7458 7344
Butachlor 50%
EC (SS) 4000
93.5 92.5
128 259
40.5 42.8
45.1 45.30
4250 3229
7208 6854
Butachlor 50%
EC (MS) 1250
93.0 92.6
111 271
35.2 48.3
40.3 44.95
3875 2948
7500 7427
Butachlor 50%
EC (MS) 2000
89.1 89.1
128 300
38.6 41.1
42.2 45.68
4000 3271
6750 7146
Almix 20% WP 4 91.6 92.0 100 298 38.1 49.5 43.6 47.06 3542 3000 7250 7167
Weed free - 92.0 92.0 99 276 33.3 52.6 43.1 46.26 4167 3448 7625 7510
Weedy - 95.2 95.5 109 284 40.7 45.4 41.7 46.90 3667 3062 7458 7105
CD at 5 % NS NS NS NS NS NS NS NS NS NS NS NS
Impact of Various Doses of Butachlor on Weed …. 3114
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African Journal of Biotechnology Vol. 12(5), pp. 499-503, 30 January, 2013 Available online at http://www.academicjournals.org/AJB DOI: 10.5897/AJB12.2433 ISSN 1684–5315 ©2013 Academic Journals
Full Length Research Paper
Acute toxicity of the chloroacetanilide herbicide butachlor and its effects on the behavior of the
freshwater fish Tilapia zillii
Christopher Didigwu Nwani1*, Udu Ibiam Ama2, Florence Okoh3, Uche Obasi Oji2, Rebecca Chima Ogbonyealu2, Arua Agha, Ibiam4 and Onyinyechi Udu-Ibiam2
1Department of Zoology and Environmental Biology, University of Nigeria, Nsukka, Nigeria.
2Department of Biochemistry, Ebonyi State University PMB 053 Abakaliki, Nigeria.
3Department of Applied Biology, Ebonyi State University, PMB 053, Abakaliki, Nigeria.
4Department of Industrial Mathematics, Ebonyi State University, PMB 053, Abakaliki, Nigeria.
Accepted 5 December, 2012
Acute toxicity of butachlor, a chloroacetanilide herbicide (2-chloro-N-[2, 6-diethylphenyl] acetamide) to Tilapia zillii, was studied in a semi static bioassay. The 24, 48, 72 and 96 h LC50 values (with 95% confidence limits) estimated by probit analysis were 3.13 (2.88 to 4.61), 1.93 (0.63 to 4.41), 1.27 (0.59 to 1.92) and 1.25 (0.60 to1.85) mgl
-1, respectively. There were significant differences (p<0.05) in the LC50
values obtained at different exposure times and the safe levels estimated by different methods varied from 1.25×10
-1 to 1.25×10
-5 mgl
-1. There were dose and time dependent increase in mortality rate due to
exposure to the herbicide. Stress signs in form of hyperactivity, erratic swimming, skin discoloration, vigorous jerks of the body followed by exhaustion and death were observed. The 96 h LC50 of 1.25 mgl
-1
obtained indicate that the herbicide was toxic to T. zillii. Agricultural use of butachlor in the environment, especially, near water bodies, must be restricted to avoid the severe risk associated with the use of the pesticide. Key words: Tilapia zillii, butachlor, toxicity, mortality, behavioral changes, safe level.
INTRODUCTION Butachlor, (2-chloro-N-[2, 6-diethylphenyl] acetamide) is one of the most widely used chloroacetanilide herbicide for the control of annual grasses in rice fields and many broadleaf weeds. It can also be used in seed beds and seed transplant fields as well as in some crop fields such as wheat, barley, cotton, vegetables and peanuts. It reac-hes aquatic environment due to the proximities of the agricultural country sides to water places. The repeated and indiscriminate use of the herbicide, careless hand-ling, accidental spillage or discharge of untreated efflu-ents into natural water ways has harmful effects on the fish and other aquatic organisms. Butachlor contamina-tion of 0.163 ppb has been recorded in ground water col-
*Corresponding author. E-mail: [email protected]: +2348037509910.
lected from tube wells adjacent rice fields in Philippines (Natarajan, 1993). The pesticide can degrade rapidly but under conditions of low temperature, low moisture, high alkalinity and lack of suitable microbial degraders, it may remain biologically active and persist in soils for a long time. Lin et al. (2000) reported that increase in sunlight enhanced photo degradation of butachlor in water and that the half life of the herbicide in non-filtered river water was shorter than filtered samples. Lin et al. (1999) also reported that surface waters with high concentrations of organic and suspended solid reduced the toxicity of pesticides possibly through photo degradation.
The contamination of aquatic ecosystems by xenobio-tics has gained increased attention and several recent studies have demonstrated the toxicity of butachlor to fish and other aquatic organisms (Geng et al., 2005; 2010; Ateeq et al., 2006; Geng et al., 2005; Peebua et al.,
500 Afr. J. Biotechnol.
Table 1. Data on fish survival at different test concentrations and sampling time intervals in T. zillii.
Exposed concentration
(mgl-1
)
Number exposed
Number of fish alive at different time intervals (hours) Mortality
(%) 24 48 72 96 Survival (%)
0.00 30 30 30 30 30 100 00
0.60 30 30 30 30 24 80 20
1.20 30 28 24 20 18 60 40
1.80 30 26 21 14 12 40 60
2.40 30 24 12 10 06 20 80
3.00 30 18 10 4 00 00 100
2007; Geng et al., 2010, Chang et al., 2011). Butachlor has also been reported to be carcinogenic (Ou et al., 2000) and can adversely disrupt the reproductive process and affect the thyroid and sex steroid hormones in Zebra fish (Chang et al., 2011). The fish Tilapia zillii is com-monly found in all African countries and some other tropi-cal countries of the world. It is an aquaculture candidate that can narrow the gap between demand and supply of animal protein in developing countries. Furthermore, Tilapia zillii is an attractive model species for toxicity studies because of its availability throughout the year, ease of culture, prolific reproduction, omnivorous nature and their general hardiness in culture environment.
In spite of the wide application of butachlor to farm-lands by our farmers and the possible ecotoxicological impact attached to its use, there is paucity of information on its effects on many local fish species like Tilapia zillii. The present study thus aims at the determination of the 96 h LC50 of butachlor to the freshwater fish Tilapia zillii, their behavioral responses and the possible safe levels of the pesticide during the exposure period. MATERIALS AND METHODS
Experimental fish specimen and chemicals
The juveniles of freshwater fish Tilapia zillii (Family: Cichlidae, Order: Perciformes) were caught from nearby rivers, ponds and lakes with the help of local fishermen. The fish specimens had an average (±S.D) wet weight and length of 8.304 ± 0.13g and 6.17 ± 0.15cm, respectively. To avoid bias, fish of similar length and weight range were selected and used. Specimens were subjected to a prophylactic treatment by bathing twice in 0.05% potassium permanganate (KMnO4) for 2 min to avoid any dermal infections. The specimens were then acclimatized for 2 weeks under laboratory conditions in semi-static systems. They were fed with commercial trout pellets daily at 2% body weight (BW) during acclimatization. The fecal matter and other waste materials were siphoned off daily to reduce ammonia content in water. The fish were treated in accordance with the rules conforming to principles of Laboratory Animal Care as set by set by the Institutional Animal Ethics Committee (IAEC) of the University. For the present study, commercial formulation of butachlor (50% EC) with trade name “butaforce” manufactured by Anhui Futian Agrochemical Ltd Shanghai, China, with CAS NO A5-0268 was purchased from the local market and used.
Acute toxicity bioassay
Acute toxicity assay to determine the 96 h LC50 values of butachlor was conducted with definitive test in a semi-static system in the laboratory as per the standard methods (APHA, AWWA, WPCE, 2005). The range finding test was carried out prior to determine the concentrations of the test solution for definitive test. The experiment was conducted in glass aquaria (60 × 30 × 30 cm size) containing 40 L of de-chlorinated and aerated water. The test solution was changed on every alternate day to counter-balance the decreasing pesticide concentrations. During the treatment, fish behavior was observed daily. In definitive test, a set of 10 fish specimen were randomly exposed to nominal butachlor (0.60, 1.20, 1.80, 2.40, 3.00 mgl
-1) concentrations. Another set of 10 fish were simultaneously
maintained in tap water, without test chemical, and considered as control. The experiment was set in triplicate and mortality of the fish due to butachlor exposure was recorded up to 96 h at every 24 h interval (Table 1) to obtain LC50 values of the test pesticides. The LC50 of butachlor was determined following the probit analysis method described by Finney (1971). The safe level of the test pesticides was estimated by multiplying the 96 h LC50 with different application factors (AF) and was based on Hart et al. (1948), Sprague et al. (1971), Committee on water Quality Criteria (CWQC, 1972), National academy of Sciences/National Academy of Engi-neering (NAS/NAE, 1973), Canadian Council of Resources and Environmental Ministry (CCREM, 1991) and the International Joint Commission (IJC, 1977). The physicochemical properties of test water, namely temperature, dissolved oxygen; pH, total hardness, conductivity and total alkalinity were analyzed using standard methods (APHA, AWWA, WPCE, 2005).
Data analysis
The data obtained were statistically analyzed by statistical package SPSS (Version 16). The data were subjected to one way analysis of variance (ANOVA) and Duncan’s multiple range test to determine the significance difference at 5 % probability level.
RESULTS
Physico-chemical parameters of the test water
The physico-chemical characteristics of the test water are presented in Table 2. The water temperature varied from 23.50 to 25.50°C, pH ranged from 7.15 to 7.80 while dissolved oxygen varied from 6.30 to 6.80 mgl
-1. The
conductivity value ranged from 252 to 300 µM cm-1
whereas total hardness varied from 174 to 180 mgl
-1as
CaCO3 during the experimental period.
Nwani et al. 501
Table 2. Physico-chemical properties of the test water.
Characteristic Mean Range
Air temperature (°C) 25.5 25.40-26.42
Water temperature (°C) 24.66 23.50-25.50
PH 7.20 7.15-7.80
Dissolved oxygen (mgl-1
) 6.55 6.30-6.80
Conductivity (µMcm-1
) 254 252-300
Total hardness (mgl-1
) 176 174-180
Table 3. Lethal concentration of butachlor (mgl-1
) (95% confidence intervals) depending on exposure time for T. zillii (n=10 in three replicates).
Lethal
concentration
Exposure time (h)
24 48 72 96
LC10 2.14a
(1.61-2.40) 1.17a
(0.01-1.65) 0.53b
(0.04-0.90) 0.52b
(0.04-0.87)
LC20 2.47a
(2.13-2.77) 1.40a
(0.01-1.89) 0.72b
(0.10-1.10) 0.69b
(0.11-1.07)
LC30 2.75a
(2.47-3.25) 1.57a
(0.03-2.17) 0.89b
(0.20-1.31) 0.87b
(0.21-1.27)
LC40 3.00a
(2.70-3.86) 1.75ab
(0.18-2.67) 1.07b
(0.36-1.55) 1.05b
(0.37-1.51)
LC50 3.26a
(2.88-4.61) 1.93ab
(0.67-4.41) 1.27b
(0.59-1.92) 1.25b
(0.60-1.85)
LC60 3.54a
(3.07-5.53) 2.12a
(1.30-14.23) 1.50a
(0.89-2.59) 1.48a
(0.89-2.46)
LC70 3.87a
(3.27-6.74) 2.36ab
(1.69-18.06) 1.81ab
(1.21-4.05) 1.79b
(1.20-3.75)
LC80 4.30a
(3.51-8.53) 2.67ab
(1.96-65.67) 2.24ab
(1.54-7.69) 2.22b
(1.54-6.87)
LC90 4.96a (3.86-11.84) 3.16
a (2.26-95.11) 3.02
a (1.98-20.48) 3.00
a (1.98-17.40)
Values with different alphabetic superscripts differ significantly (p<0.05) between exposure time within lethal concentration.
Behavioral response of fishes to test concentrations
Fish exposed to different concentrations of the pesticide displayed behavioral abnormalities in response to the test chemical. At the initial exposure, fish that were alert stopped swimming and remained static in position in res-ponse to the sudden changes in the surrounding environ-ment. After some time, fish in the experimental groups tried to avoid the test water by swimming very fast, jump-ing and displaying other random movements. In tanks with higher concentrations of the test pesticide swimming of the fish was erratic with vigorous jerky movements along with hyper excitation. Faster opercula movement, surfacing and gulping of air were observed. Body pig-mentation was decreased while copious mucus which covered the buccal cavity, body and gills were secreted. Later, the fish lost their balance, consciousness, engaged in rolling movement and became exhausted and lethargic owing to respiratory incumbency. Soon, they settled down passively at the bottom of the tank with the opercu-lum wide open and ultimately died.
Median lethal concentration and application factor
Median lethal concentration (LC50) is the concentration of a test chemical, which kill 50% of the test organism in a particular length of exposure, usually 96 h. The LC50
values (with 95% confidence limits) of different concen-trations of butachlor in T. zillii were found to be 3.13 (2.88 to 4.61), 1.93 (0.63 to 4.41), 1.27 (0.59 to 1.92) and 1.25 (0.60 to 1.85) mgl
-1 respectively for 24, 48, 72 and 96 h
exposure time (Table 3). A time and dose-dependent increase in mortality rate was observed; thus, as the exposure time increased from 24 to 96 h, the median lethal concentration required to kill the fish was reduced. There were significant differences (p < 0.05) in LC10-90
values obtained for different times of exposure. During the experimental period no mortality was recorded in the control experiment. The estimated safe level of butachlor as calculated by multiplying the 96 h LC50 with different application factors are given in Table 4. The values of safe level of butachlor in the Tilapia zillii varied from 1.25×10
-1 to 1.25×10
-5 mgl
-1.
DISCUSSION
Acute and chronic toxicity tests are widely used to eval-uate the toxicity of chemicals on non-target organisms (Santos et al., 2010). The 96 h LC50 of 1.25 mgl
-1 ob-
tained indicate that the herbicide is toxic to T. zillii. The toxicity is both concentration and time dependent thus, accounting for the differences in the values obtained at different concentrations and exposure times. When T. zillii juveniles were exposed to 0.60 mgl
-1 butachlor con-
502 Afr. J. Biotechnol.
Table 4. Estimate of safe levels of butachlor at 96 h exposure time.
Chemical 96 h LC50 (mgl-1
) Method AF Safe level (mgl-1
)
Butachlor 1.25 Hart et al. (1948)* - 2.30×10-2
Sprague (1971) 0.1 1.25×10
-1
CWQC (1972) 0.01 1.25×10
-2
NAS/NAE (1973) 0.01-0.00001 1.25×10
-1-1.25×10
-5
CCREM (1991) 0.05 6.25×10
-2
IJC (1977) 5% LC50 6.25×10-2
*C = 48 h LC50×0.03/S2, where C is the presumable harmless concentration and S = 24 h LC50/48 h LC50.
centrations, only 20 % died after 96 h, whereas all the fish (100 %) died after 96 h expose at 3.00 mgl
-1
butachlor concentration. Previously reported LC50 values of butachlor in Oreochromis niloticus (Wang et al., 1992), Heteropneustus fossilis (Ateeq et al., 2005) and Channa punctatus (Tilak et al., 2007) were 0.880 mgL
-1, 2.34 ppm
and 247.46 ppb, respectively. Geng et al. (2005) reported 96 h LC50 of 1.40 mgl
-1 when Rana japonica was exposed
to butachlor while Gobic and Gunasekaran (2010) obtained 96 h LC50 of 0.515 mg/kg for Eisenia fietida. From the observed results, 96 h LC50 value for butachlor in T. zilli was higher than the 10.20 and 381.9 µgl
-1 ob-
tained when similar fish, Nile tilapia (Oreochromis niloti-cus) was exposed to endosulfan (Werimo and Willen, 2010) and alachlor (Peebua et al., 2007), respectively thus indicating that endosulfan and alachlor are more to-xic to tilapia than butachlor. The previous literature clearly indicates that the toxicity of butachlor varies from one species to another and even in strains of the same species.
Toxicity of chemicals to aquatic organisms has been reported to be affected by temperature, pH, dissolved oxygen, size and age, type of species, water quality, concentration and formulation of test chemicals (Gupta et al., 1981; Young, 2000; Nwani et al., 2010). The safe level obtained for butachlor in the present study varied from 1.25×10
-1 to 1.25×10
-5 mgl
-1. However, the large
variation in safe levels determined by various methods has resulted in controversy over its acceptability (Buikema et al., 1982; Pandey et al., 2005). Kennega (1979) emphasized that the major weakness in calcula-tion of application factor (AF) is its dependence on LC50 values. Behavioral changes are the most sensitive indica-tors of potential toxic effects (Banaee et al., 2011). The behavioral and swimming patterns of the fish in the con-trol group were normal but for the experimental groups abnormal swimming behavior increased with increasing concentration and exposure time. Bekeh et al. (2011) reported similar behavioral responses in Tilapia (Oreo-chromis niloticus) exposed to butachlor. The behavioral symptoms observed during butachlor exposure to T. zillii also agree with the observations reported by other authors reporting toxicity of pesticides in fish (Kumar et al., 2010, Pandey et al., 2011; Banaee et al., 2011, Chang et al., 2011; Altinok et al., 2012).
Our results from the present study on butachlor toxicity support the conclusion that T. zillii is sensitive to the pesticide and their mortality rate is dose and time depen-dent. This study also shows the significance of behavioral parameters in assessing the hazards of the pesticide to fish. Agricultural use of butachlor in the environment especially near water bodies must be restricted to avoid the sever risk associated with the use of the pesticide.
ACKNOWLEDGEMENTS We acknowledge Tertiary Education Trust Fund Nigeria (TETFUND), and the DERIC, Ebonyi State University, Abakaliki for providing the fund and the conducive environment, respectively, to carry out the research. REFERENCES
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Comparative and combined acute toxicity of butachlor, imidacloprid and chlorpyrifos on earthworm,
Eiseniafetida.
Chen C1, Wang Y2, Zhao X2, Wang Q2, Qian Y1
Author information
Chemosphere, 27 Dec 2013, 100:111-115
DOI: 10.1016/j.chemosphere.2013.12.023 PMID: 24377448
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Abstract
Various pesticides have become widespread contaminants of soils due to their large applications in
agriculture and homes. An earthworm assay was used to assess the acute toxicity of butachlor,
imidacloprid and chlorpyrifos with different modes of action. Ecotoxicities of these pesticides were
compared for earthworm Eiseniafetida separately and in combination in artificial soil and contact
filter paper tests. Imidacloprid was the most toxic for E. fetida with LC₅₀ (lethal concentration 50)
values three orders magnitude lower than that of butachlor and chlorpyrifos in both tests. The
toxicity of the mixtures was compared to that predicted by the concentration addition (CA) model.
According to the CA model, the observed toxicities of all binary mixtures were less than additive.
However, for all the mixtures in 14 d artificial soil test, and mixtures of butachlor plus chlorpyrifos
and imidacloprid plus chlorpyrifos in 48 h contact filter paper test, the difference in toxicity was less
than 30%, hence it was concluded that the mixtures conformed to CA. The combined effects of the
pesticides in contact filter paper tests were not consistent with the results in artificial soil toxicity
tests, which may be associated with the interaction of soil salts with the pesticides. The CA model
provides estimates of mixture toxicity that did not markedly underestimate the measured toxicity,
and therefore the CA model is the most suitable to use in ecological risk assessments of the
pesticides.
Bull Environ ContamToxicol
. 2018 Feb;100(2):208-215. doi: 10.1007/s00128-017-2245-9. Epub 2017 Dec 13.
Oxidative Stress Response Induced by Butachlor in Zebrafish Embryo/Larvae: The Protective Effect of
Vitamin C
Qingqing Xiang 1, Bofan Xu 1, Yilun Ding 2, Xiaoyi Liu 1, Ying Zhou 3 4, Farooq Ahmad 5
Affiliations expand
PMID: 29236155 DOI: 10.1007/s00128-017-2245-9
Abstract
The widespread contamination and persistence of the herbicide butachlor in the environment
resulted in the exposure of non-target organisms. The present study investigated the toxicity effect
of butachlor (1-15 µmol/L) and the protective effect of vitamin C (VC) against butachlor-induced
toxicity in zebrafish. It was found that butachlor significantly increased the mortality and
malformation rates in a dose-dependent manner, which caused elevation in reactive oxygen species
(ROS) and malondialdehyde (MDA) after 72 h exposure. Compared with butachlor treatment group,
the protective effect of VC against butachlor-induced toxicity were observed after adding 40, 80
mg/L VC respectively. VC significantly decreased the mortality, malformation rates, ROS, MDA, and
normalized antioxidant enzymes activities of zebrafish after 72 h exposure. The result shows VC has
mitigative effect on butachlor-induced toxicity and it can be used as an effective antioxidant in
aquaculture.
Keywords: Butachlor; Oxidative stress; Protective effect; Vitamin C; Zebrafish.
