Application Of Alachlor Research Articles

Influence of Pre-Emergence Weedicides on Turmeric (Curcuma longa L.) Growth and Yield

A field experiment was conducted during 2015-16, 2016-17 and 2017-18 at Agricultural Research Station, Hanumanamatti to study the effect of chemical herbicides on weed management in turmeric. The treatments consisted of pre emergent application of Alachlor, Butachlor, Pedimethalin, Atrazine and Quizalofop ethyl. The pooled mean results indicated that, pre-emergent application of Alachlor @ 1.50 kg ai / ha + one interculture + one hand weeding (A1IC1HW) recorded the least weed density (13.67, 68.11 monocot weeds and 2.67,12.36 dicot weeds), weed bio-mass (32.33 g, 43.67 g fresh weight of monocot weeds and 5.68 g, 26.05 g fresh weight of dicot weeds, 17.50g, 7.68g dry weight of monocot weeds and 2.34 g, 10.69 g dry weight of dicot weeds), the highest turmeric plant height (11.35 cm, 32.49 cm), number of leaves (4.92, 8.39), leaf length (5.08 cm, 18.91cm), leaf breadth (2.21 cm, 7.25 cm) and number of tillers per plant (1.01, 4.34) at 30 and 60 days after planting respectively. The treatment with Alachlor @ 1.50 kg ai / ha + one interculture + one hand weeding (A1IC1HW) also recorded the highest yield per plot (65.03 kg), rhizome yield/ha (43.36 tonnes) and processed rhizome yield (8.67 t/ha) followed by Pendimethalin @ 1.00 kg ai/ha + one interculture + one hand weeding (P1IC1HW) compared to farmer’s practice (2HW1IC) and unweeded control (WC).

Integrated weed management in elephant foot yam

The experiment was conducted at Krishi Vigyan Kendra, Bilaspur during 2017-18 and 2018-19 to find out alternatives to manual weeding in elephant foot yam. The manual weeding and herbicides alone and in combinations were tried. The results revealed that pre emergence application of alachlor @1.00 kg a.i./ha along with hand weeding after 60 days of planting is the most effective and economic treatment for weed management and getting highest return in elephant foot yam variety 'Palam Zimikand-1' under low hill condition of Himachal Pradesh.

Sequential application of pre-and post-emergence herbicides to control mixed weed flora in maize

A field experiment was laid out in randomized block design with ten weed management practices to determine the bioefficacy of PoE herbicides, halosulfuron-methyl 67.5 g/ha and tembotrione 100 g/ha alone or tank mix and sequential application after PE application of alachlor 1000 g/ha, besides two hand weedings and unweeded control. The broadspectrum weed control and the highest grain yield of rainy season maize was obtained with sequntial application of alachlor 1000 g/ha as PE fb PoE application of halosulfuron-methyl 67.5 g/ha + tembotrione 100 g/ha (tank mix). Post-emergence application of halosulfuron-methyl 67.5 g/ha effectively controlled purple nutsedge.

Effect of controlled release formulations of diuron and alachlor herbicides on the biochemical activity of agricultural soils

The use of pesticides in agriculture is essential because it reduces the economic losses caused by pests, improving crop yields. In spite of the growing number of studies concerning the development and application of controlled release formulations (CRFs) of pesticides in agricultural soils, there are no studies about the effects of such formulations on the biochemical properties. In this paper the dissipation of diuron and alachlor in three agricultural soils for 127days, applied either as commercial or CRFs, was determined as well as their concomitant effects on soil biochemical properties. Dehydrogenase, urease, β-glucosidase and phosphatase activities were measured thought the experimental period. The application of alachlor as CRF increases its half-life time in soils, whereas no differences were noticed between diuron formulations due to its slower degradation, which takes longer than its release from the CRF. At the end of the incubation period, the enzymatic activities were the same after the use of diuron either as commercial or CRF, recovering the soil previous status. For alachlor formulations, no differences in enzymatic activities were again observed between both formulations, but their levels in soils were enhanced. Therefore, the use of these CRFs does not adversely affect the soil biochemical properties.

Exploring Cost effective Herbicide based Weed Management options for Sunflower in NW India

Field experiment was conducted during spring 2009 and 2010 in the Indo-Gangetic alluvial plains to evaluate the efficacy of different pre-emergence herbicides alone or in combination with hand weeding for effective weed management in sunflower. Season long competitional stress with weeds reduced the mean seed yield of sunflower by 43.5% in comparison to conventional practice of two hand weedings (3 and 6 weeks after sowing). Herbicide based weed management increased the sunflower yield by 52.6–71.6% in comparison to weedy check. Irrespective of herbicide dose, yield improvement to the tune of 5.5–12.5% was observed with weed management through either of the pre-emergence herbicide (oxydiargyl/alachlor) when compared with recommended herbicide application of pendimethalin @ 0.75 kg/ha. Integrated approach involving herbicides with one hand weeding 4 WAS resulted in better seed yields (3.1–4.4% superiority) but the profit margin gets reduced due to higher wages of human labour incurred. Alone application of alachlor 1.5 kg/ha resulted in highest monetary benefits with highest B: C ratio of 3.49 followed by oxydiargyl 0.1 kg/ha (3.35) which was as good as two hand weedings done 3 and 6 WAS. This study identifies pre-emergence application of alachlor 1.5 kg/ha or oxydiargyl 0.1 kg/ha as economically viable weed management strategy in sunflower considering the present situation of labour scarcity, quality of weed control, productivity and profitability concerns.

Response of chemical weed management in maize and cowpea intercropping system grown for quality fodder in Eastern Uttar Pradesh

Field experiment was carried out during Kharif 2005 and 2006 using different herbicides to study the response of weed control treatments in maize and cowpea intercropping system for quality fodder. Pre-emergence application of alachlor, metolachlor and pendimethalin @ 1.00 and 1.50 kg a.i./ha each and post emergence application of imazethapyr @ 0.10 and 0.15 kg a.i./ha at 20 days of crop sown combined with weedy and weed-free conditions. All the herbicides at each dose effectively controlled the weeds and reduced its dry weight as compared to weedy condition. Alachlor, metolachlor and pendimethalin at 1.5 kg a.i./ha and pendimenthalin at 1.0 kg a.i./ha significantly reduced the population and dry weight of total weeds over the other rates of herbicides. Pendimethalin @ 1.5 kg/ha gave maximum green forage and dry matter yield (448 and 102 q/ha) among herbicide treated plots which were at par with that of weed free condition (466 and 109 q/ha). All the herbicides at higher doses followed the same trend in reduction of dry matter accumulation of weeds and increased in green forage and dry matter yield of maize and cowpea mixed fodder over control. Similarly, with increase in the dose of herbicide the crude protein, nitrogen uptake and DM (dry matter) per cent increased significantly.

Effect of Seeding Method and Pre-emergence Herbicides on Plant Growth and the Production of Sorghum × Sudangrass Hybrid

Jeong Sung Jung, Ki-Won Lee, Ki Choon Choi, Hee Jung Ji, Hyung Soo Park, Won Ho Kim, Young-Jin Kim,Sang Hak Lee and Sang-Hoon Lee*National Institute of Animal Science, Rural Development Administration, Cheonan 330-801, KoreaABSTRACTThe following experiments were used to evaluate the effect of seeding method and pre-emergence herbicides on weed control and the production of the sorghum×sudangrass[sorghum bicolor (L.) Moench] hybrid under field and in vitro conditions. Under the in vitro condition, we evaluated how different kinds of herbicides affect the rate of seed germination and the growth of early seedlings in the sorghum×sudangrass hybrid treated with herbicides. Simazine, alachlor, and methabenzthiazuron were used, and their concentration levels were 0%, 40%, 70%, and 100%. The germination ratio of the seeds was reduced by the application of simazine, methabenzthiazuron, and alachlor compared with the control(distilled water). The alachlor application severely decreased the sorghum germination ratio. However, seed germination was not greatly influenced by the concentration level of the herbicides. Root and shoot length were increased in the following order: control>simazine>methabenzthiazuron>alachlor. Overall, alachlor significantly reduced root length more than shoot length. The differential tolerance of the sorghum×sudangrass hybrid to pre-emergence herbicides by seeding method was then tested under the field condition. The plants were severely injured by the alachlor application, leading to a great reduction in the number of stems. However, for the simazine and methabenzthiazuron applications the number of stems lost was slightly lower than it was for the alachlor and simazine+alachlor applications. In the seeding method, drilling was more effective in reducing herbicide injury than broadcasting. All of the herbicides effectively controlled weeds. The simazine and methabenzthiazuron applications showed a significantly higher dry matter(DM) yield. However, the alachlor and simazine+alachlor applications severely reduced the DM yield. This result suggests that the alachlor application has a significant effect on plant production. Similarly, the total digestible nutrient(TDN) yield was greatly reduced by the alachlor and simazine+alachlor applications. From the results presented above, we concluded that the yield of DM was the highest for broadcasting with no herbicide. and drilling was the most-effective way to reduce herbicide injury. The simazine application was the most-effective herbicide, showing the highest forage yield and TDN yield.(Key words :Pre-mergence herbicide, Sorghum×sudangrass hybrid, Seeding method, Production, Plant growth)

Sustainable Dryland Technologies for Improving Productivity and Livelihood Security in Alfisols of Karnataka

Operational Research Project on dryland agriculture with its main focus on participatory technology demonstration functioned at Alanatha cluster of villages from 2010 to 2014. Based on the PRA and benchmark survey, technical interventions have been taken up under different themes. Opening of moisture conservation furrow between paired rows of pigeonpea in finger millet + pigeonpea (8: 2) and groundnut + pigeonpea (8: 2) intercropping systems recorded higher finger millet grain equivalent yield (3156 kg/ha) and groundnut equivalent (1007 kg/ha) yield with higher net returns( 37390 and 18842/ha, respectively) and higher values of sustainable yield index (0.56 and 0.30, respectively). Introduction of pigeonpea + field bean (1: 1) intercropping system resulted in higher pigeonpea equivalent yield (1173 kg/ha), sustainable yield index value (0.43) and net returns ( 32415/ha) compared to sole crop of pigeonpea (1093 kg/ha), field bean (461 kg/ha). Improved medium duration finger millet variety GPU-66 produced higher grain yield (2722 kg/ha) and net returns ( 25542/ha) followed by variety ML-365. Improved pigeonpea variety TTB 7 produced higher seed yield (879 kg/ha). Application of organic and inorganic fertilizers along with micronutrients gave maximum net returns ( 36504/ha), sustainable yield index value (0.72) and higher yield (2899 kg/ha) compared to farmers’ practice. Pre-emergent application of alachlor @ 2.5 lt/ha along with one hand weeding recorded lower weed menace and higher groundnut pod yield (499 kg/ha).

Biodegradation of alachlor in liquid and soil cultures under variable carbon and nitrogen sources by bacterial consortium isolated from corn field soil

Alachlor, an aniline herbicide widely used in corn production, is frequently detected in water resources. The main objectives of this research were focused on isolating bacterial consortium capable of alachlor biodegradation, assessing the effects of carbon and nitrogen sources on alachlor biodegradation and evaluating the feasibility of using bacterial consortium in soil culture. Kavar corn field soil with a long history of alachlor application in Fars province of Iran has been explored for their potential of alachlor biodegradation. The influence of different carbon compounds (glucose, sodium citrate, sucrose, starch and the combination of these compounds), the effect of nitrogen sources (ammonium nitrate and urea) and different pH (5.5-8.5) on alachlor removal efficiency by the bacterial consortium in liquid culture were investigated. After a multi-step enrichment program 100 days of acclimation, a culture with the high capability of alachlor degradation was obtained (63%). Glucose and sodium citrate had the highest alachlor reduction rate (85%). Alachlor reduction rate increased more rapidly by the addition of ammonium nitrate (94%) compare to urea. Based on the data obtained in the present study, pH of 7.5 is optimal for alachlor biodegradation. After 30 days of incubation, the percent of alachlor reduction were significantly enhanced in the inoculated soils (74%) as compared to uninoculated control soils (17.67%) at the soil moisture content of 25%. In conclusion, bioaugmentation of soil with bacterial consortium may enhance the rate of alachlor degradation in a polluted soil.

Growth and development of symbiotic Arbuscular mycorrhizal fungi, Glomus mossea (Nicol. and Gerd.), in alachlor and glyphosate treated soils

Herbicides are applied to control weeds in agricultural practices and could also be detrimental to the development of some microorganisms living in the soil ecosystem. This study was conducted to determine the growth and development of mycorrhizal fungi, Glomus mossea (Nicol. and Gerd.), in soils treated with herbicides. Herbicide treatments were alachlor at 1.8, 3.6, 5.4 and 36 μg active ingredient (a.i.) g -1 or glyphosate at 1.1, 2.2, 3.3 and 21.6 μg a.i. g -1 dry soil, representing 0.5, 1, 1.5 and 10 x their recommended field application rates. Spore germination percentage and hyphal growth length were determined from spores germinated on cellulose membrane filters, sandwiched between the herbicide treated soil layers in Perti-dish after 30 days incubation in darkness at 22±1°C. External and internal hyphae and their active portions were determined from soil samples of the host growing medium and colonized host plant root systems, respectively. The alkaline phosphatase (ALP) and succinate dehydrogenase (SDH) staining techniques were used to determine the respective active portion of the hyphae. Spores from the prepared inoculum source have high germination percentage (93%) in nonherbicide treated soil. Germination of spores and its hyphal growth were not significantly affected in soil treated with alachlor and glyphosate at the recommended field application rates or less. Alachlor reduced the spore germination and hyphal growth significantly at treatments higher than recommended field application rates, but non-significant effect caused by the glyphosate. The development of external hyphae was insignificantly affected in the herbicides treated soils compared with that of the untreated soil. Colonization and development of internal hyphae on host plant roots were not affected by the herbicide treatments to the soil growing medium at recommended field application rates or less. There was a tendency for the higher treatment rates of alachlor (1.5 and 10x) to affect the development of internal mycorrhizal tissues. Application of alachlor or glyphosate herbicide at their recommended field application rates were not harmful to mycorrhizal development and symbiotic colonization of plant roots. Alachlor, at higher treatments than the recommended field application rates affected the presymbiotic stages of the spore germination and the internal mycorrhizal tissues development substantially. Key words : Arbuscular mycorhrizal fungi, Glomus mossea (Nicol. and Gerd.), alachlor, glyphosate.

Potencial de lixiviação de herbicidas utilizados na cultura do algodão em colunas de solo

O intenso uso de herbicidas implica a necessidade de determinar o potencial dessas substâncias em contaminar fontes aquáticas subsuperficiais. Diante dessa preocupação, o objetivo deste trabalho foi avaliar o efeito de diferentes lâminas de água sobre o potencial de lixiviação de quatro herbicidas utilizados em pré-emergência na cultura do algodão, em dois solos provenientes de Campo Novo do Parecis-MT (RQ - textura arenosa) e Tangará da Serra-MT (LV - textura argilosa). No desenvolvimento deste trabalho utilizouse a técnica de bioensaio em colunas de solo, nas quais foram simuladas irrigações de 0, 20, 40, 60, 80 e 100 mm, após a aplicação de alachlor (RQ 2,40; LV 3,36 kg ha-1), oxyfluorfen (RQ 0,48; LV 0,72 kg ha-1), prometryne (RQ 0,75; LV 1,50 kg ha-1) e S-metolachlor (RQ 1,20; LV 1,44 kg ha-1). Nas amostras de solo com textura arenosa (RQ), evidenciou-se que lâminas de 80 e 100 mm de água proporcionaram lixiviação até a profundidade de 10-15 cm do alachlor e até 15-20 cm do S-metolachlor. Independentemente da lâmina de água aplicada, nas amostras de RQ oxyfluorfen não ultrapassou a camada de 5-10 cm, e o prometryne movimentou-se até a camada de 10-15 cm somente na lâmina de 100 mm de água. Nas amostras de solo com textura argilosa (LV), o oxyfluorfen não se movimentou além da camada superficial, mesmo sob as maiores lâminas de irrigação, e o prometryne atingiu 5-10 cm de profundidade sob lâminas de 80 e 100 mm. Os herbicidas alachlor e S-metolachlor atingiram 10-15 cm de profundidade sob lâminas de 80 e 100 mm no LV. Evidenciou-se uma maior movimentação efetiva das moléculas de herbicidas nas amostras de solo com textura arenosa (RQ), em relação às amostras de solo com textura argilosa (LV).

Weed control with pre-emergence herbicides in vegetable soybean ( Glycine max L. Merrill)

Field and laboratory experiments were conducted in the early and late rainy seasons in Thailand to evaluate the effect of pre-emergence application of herbicides and determine the herbicide residues on vegetable soybean ( Glycine max L. Merrill cv. No. 75) production. No visible crop injury was observed after application of alachlor 469 g a.i./ha, clomazone 1080 g a.i./ha, metribuzin 525 g a.i./ha, pendimethalin 1031.25 g a.i./ha, tank-mixed clomazone 960 g a.i./ha + pendimethalin 928 g a.i./ha, or tank-mixed metribuzin 350 g a.i./ha + pendimethalin 928 g a.i./ha. However, acetochlor 1875 g a.i./ha, isoxaflutole 75 g a.i./ha, and oxadiazon 1000 g a.i./ha caused visible crop injury. Plant bioassay of herbicide residues in the soil after harvest showed no phytotoxic effect on baby corn ( Zea mays Linn. cv. Suwan 3), cucumber ( Cucumis sativus L. cv. Pijit 1), pak choi ( Brassica chinensis Jusl. cv. Chinensis), and soybean ( G. max L. Merrill cv. CM 60). Gas Chromatography-Mass Spectrometry (GC–MS) analysis showed no significant herbicide residues on crop yield (or MRLs < 0.01 ppm) for all herbicides used in this study. The application of metribuzin at 525 g a.i./ha was sufficient to provide satisfactory full-season control of several weed species and gave the highest crop yield. In addition, pendimethalin at 1031.25 g a.i./ha, and tank-mixed metribuzin at 350 g a.i./ha + pendimethalin at 928 g a.i./ha can provide a similar level of weed control as an alternative to reduce herbicide dosage thereby increasing food and environmental safety in vegetable soybean production.

Weed Management Studies in Cassava (Manihot esculenta L.) Intercropping Systems under Irrigated Conditions

A field experiment was conducted during 2003-04 and 2004-05 to asses the production potential of intercropping of cassava (Manihot esculenta L.) with groundnut (Arachis hypogea), vegetable cowpea (Vigna sinensis) and black gram (Vigna mungo) in relation to various weed control practices. Intercropping influenced the population of grasses, sedges, BLW and total dry matter production of weeds. Weed management caused significant improvement in growth, yield and economic returns of cassava system. Best results were achieved with intercropping of vegetable cowpea with pre-emergence application of fluchloralin 0.75 kg/ha + one hand weeding 4 weeks after planting followed by application of alachlor @ 1.5 kg/ha + one hand weeding 4 weeks after planting.

Determination of alachlor, metolachlor, and their acidic metabolites in soils by microwave‐assisted extraction (MAE) combined with solid phase extraction (SPE) coupled with GC‐MS and HPLC‐UV analysis

A well-validated analytical method based on microwave-assisted extraction (MAE) and SPE is presented for the combined analysis of alachlor, alachlor-oxanilic acid (OXA), alachlor-ethanesulfonic acid (ESA), metolachlor, metolachlor-OXA, metolachlor-ESA residues in soils. Extraction of solutes by soil sample was carried out by MAE for 20 min at 100 degrees C in the presence of 50 mL solution (methanol/water 50:50), the extract was subsequently passed through C18 cartidges and fractionated into two fractions, the first with parent compounds (PCs) analyzed with GC-MS and the second one containing the metabolites analyzed with HPLC. For the SPE step, various types of sorbents (Environmental C18, tC18, Supelclean ENVI-carb, and LiChrolut EN) have been used, and their respective advantages and disadvantages are discussed. After the method optimization, average recovery values of all solutes were > 71% in the 50-500 microg/kg fortification range with RSD <10%. The LOQ and LOD were 10-50 and 5-10 microg/kg, respectively. The method was validated with two types of soils (1 and 2.4% organic matter) and in fresh (12 h aging), intermediate (1 wk aging), and aged (1 month aging) spiked samples. Moreover, residue levels determined after field application of alachlor or metolachlor were higher when soils were processed using this method than with a comparison method based on an overnight flask shaking (FS) of soil suspension.

Segurança das condições de trabalho de tratorista em aplicações de herbicidas em soja e amendoim e eficiência de equipamentos de proteção individual

Teve-se o objetivo de avaliar a eficiência de um conjunto de equipamentos de proteção individual no controle das exposições proporcionadas ao tratorista aplicando herbicidas nas culturas de soja e de amendoim com o pulverizador de barra e a segurança dessas condições de trabalho. Os pulverizadores utilizados foram os convencionais empregados nas duas culturas para as aplicações de herbicidas em pré-plantio incorporado (ppi), em pré-emergência (pré) e em pós-emergência inicial (pós), com volumes de 200 L ha-1, e 150 L ha-1 apenas na aplicação em pós, na cultura de soja. As exposições sem EPIs foram de 102,77 mL de calda por dia nas aplicações em ppi, 39,62 em pré e 47,14 em pós-emergência. A eficiência dos EPIs no controle das exposições dérmicas foi de 76,5% em ppi, 50,9% em pré e 75,3% em pós-emergência. Na cultura de soja, foram seguras para o tratorista, sem ou com EPIs, as aplicações de pendimethalin, imazaquin e flumetsulam em ppi; de pendimethalin, acetochlor, clomazone, flumioxazin, imazaquin, metribuzin, sulfentrazone, dimethenamid e flumetsulamem em pré, e de bentazone, glyphosate, imazethapyr, quizalofop-ethyl, chlorimuron ethyl e oxasulfuron em pós. Na cultura de amendoim, sem e com EPIs, foi segura a aplicação de pendimethalin em ppi; em pré, a aplicação de alachlor foi classificada como insegura, sem ou com o uso dos EPIs.

Agricultural pesticide use and hypospadias in eastern Arkansas.

IntroductionWe assessed the relationship between hypospadias and proximity to agricultural pesticide applications using a GIS-based exposure method.MethodsWe obtained information for 354 cases of hypospadias born between 1998 and 2002 in eastern Arkansas; 727 controls were selected from birth certificates. We classified exposure on pounds of pesticides (estimated by crop type) applied or persisting within 500 m of each subject’s home during gestational weeks 6 to 16. We restricted our analyses to 38 pesticides with some evidence of reproductive, developmental, estrogenic, and/or antiandrogenic effects. We estimated timing of pesticide applications using crop phenology and published records.ResultsGestational age at birth [odds ratio (OR) = 0.91; 95% confidence interval (CI), 0.83–0.99], parity (OR = 0.79; 95% CI, 0.65–0.95), and delaying prenatal care until the third trimester (OR = 4.04; 95% CI, 1.46–11.23) were significantly associated with hypospadias. Risk of hypospadias increased by 8% for every 0.05-pound increase in estimated exposure to diclofop-methyl use (OR = 1.08; 95% CI, 1.01–1.15). Pesticide applications in aggregate (OR = 0.82; 95% CI, 0.70–0.96) and applications of alachlor (OR = 0.56; 95% CI, 0.35–0.89) and permethrin (OR = 0.37; 95% CI, 0.16–0.86) were negatively associated with hypospadias.ConclusionsExcept for diclofop-methyl, we did not find evidence that estimated exposure to pesticides known to have reproductive, developmental, or endocrine-disrupting effects increases risk of hypospadias. Further research on the potential effects of exposure to diclofop-methyl is recommended.

Developmental disorders in embryos of the frog Xenopus laevis induced by chloroacetanilide herbicides and their degradation products

AbstractPesticides are known to transform in the environment, but so far the study of their effects in the environment has concentrated on the parent compounds, thereby neglecting the effects of the degradation products. The embryotoxic, developmental, and teratogenic effects of chloroacetanilide herbicides and their environmentally stable aniline degradation products were investigated in this study in view of the massive application of alachlor and metolachlor. Embryos at midblastula to early gastrula stages of a locally abundant African clawed frog Xenopus laevis were used as test organisms. The embryos were exposed to the test chemicals for 96 h in each experiment. Alachlor is more embryotoxic (the concentration causing 50% embryo lethality, 96‐h LC50 = 23 μM [6.1 mg/L]) and teratogenic (teratogenic index [TI] = 1.7) than metolachlor (96‐h LC50 5 48 μM [13.6 mg/L], TI = 0.2). The degradation products of alachlor and metolachlor, respectively, 2,6‐diethylaniline (96‐h LC50 = 13 μM [19.4 mg/L], TI = 2.1) and 2‐ethyl‐6‐methyaniline (96‐h LC50 = 509 μM [68.8 mg/L], TI 5 2.7), are less embryotoxic but more teratogenic than their parent compounds. The most common teratogenic effects observed were edema for alachlor as opposed to axial flexures and eye abnormalities for 2,6‐diethylaniline and 2‐ethyl‐6‐methylaniline. Metolachlor is found to be an example of a nonteratogenic herbicide that upon degradation loses toxicity but gains teratogenicity, and both the herbicides, metolachlor and alachlor, are potential sources of teratogenic transformation products.

DEVELOPMENTAL DISORDERS IN EMBRYOS OF THE FROG XENOPUS LAEVIS INDUCED BY CHLOROACETANILIDE HERBICIDES AND THEIR DEGRADATION PRODUCTS

Pesticides are known to transform in the environment, but so far the study of their effects in the environment has concentrated on the parent compounds, thereby neglecting the effects of the degradation products. The embryotoxic, developmental, and teratogenic effects of chloroacetanilide herbicides and their environmentally stable aniline degradation products were investigated in this study in view of the massive application of alachlor and metolachlor. Embryos at midblastula to early gastrula stages of a locally abundant African clawed frog Xenopus laevis were used as test organisms. The embryos were exposed to the test chemicals for 96 h in each experiment. Alachlor is more embryotoxic (the concentration causing 50% embryo lethality, 96-h LC50 = 23 microM [6.1 mg/L]) and teratogenic (teratogenic index [TI] = 1.7) than metolachlor (96-h LC50 = 48 microM [13.6 mg/L], TI = 0.2). The degradation products of alachlor and metolachlor, respectively, 2,6-diethylaniline (96-h LC50 = 13 microM [19.4 mg/L], TI = 2.1) and 2-ethyl-6-methyaniline (96-h LC50 = 509 microM [68.8 mg/L], TI = 2.7), are less embryotoxic but more teratogenic than their parent compounds. The most common teratogenic effects observed were edema for alachlor as opposed to axial flexures and eye abnormalities for 2,6-diethylaniline and 2-ethyl-6-methylaniline. Metolachlor is found to be an example of a nonteratogenic herbicide that upon degradation loses toxicity but gains teratogenicity, and both the herbicides, metolachlor and alachlor, are potential sources of teratogenic transformation products.

SORPTION AND DESORPTION OF THE HERBICIDE ALACHLOR ON HUMIC ACID FRACTIONS FROM TWO VERMICOMPOSTS

The present study focuses on the analysis of two vermicomposts, that have been used as alternative sources of restitution of soil organic matter, as well as sources of nutrient replacements. For this purpose, two samples of vermicom-posts from different Brazilian regions (São Carlos—SP and Londrina—PR) were characterized according to their humic acid content. Both samples had a pH value near 7.0, and the humic acids present showed high cationic exchange capacities and low values for the C/N ratios. The infrared spectra showed bands that suggested the presence of aliphatic and aromatic components bound to phenolic, carboxylic and amide groups. The effect of vermicompost added to soil on the application of alachlor was evaluated. Alachlor sorption, Freundlich isotherms and alachlor desorption curves in the soil matrix and the vermi-compost/soil mixture matrix were determined.

Effect of pre and post emergence herbicides on weed control and productivity of soybean (Glycine max)

A field experiment was conducted during the rainy seasons of 2000 and 2001 on Vertisol, to study the effect of different pre and post emergence herbicides on JS 335 soybean [Glycine max (L.) Merr.]. Among the tested herbicides, the highest seed yield was recorded with combi product of imazamox imazethapyr Q 75 glha PoE, i.e. 1,622 kglha, and it was significantly on a par with 2 hand weedings (1,710 kglha). The highest weed control efficiency and lowest weed biomass were recorded with 2 hand weedings, followed by application of imazamox imazethapyr Q 75 glha PoE and quizalofop ethyl Q 50 glha PoE. Among the pre emergence herbicides, S metolachlor Q 750 glha performed better than application of alachlor Q 2 kglha and lower dose of S metolachlor 500 glha.