Effect of Combined Application of Systemic Herbicides on Microbial Activities in North Bengal Alluvial Soil

An experiment was conducted under laboratory conditions to investigate the effect of combined application of three systemic herbicides, viz., fenoxaprop, pendimethalin and paraquat at 50 g, 1.0 kg and 1.0 kg a.i. ha^?1, respectively, on the changes of microbial biomass C, N and P in relation to transformations and availability of some plant nutrients in an alluvial soil (Typic Orchraqualf) of West Bengal, India. Application of the herbicides, in general, significantly increased microbial biomass C, N and P, resulting in greater availability of C, N and P in soil. The microbial biomass C was highly induced (28.4 %) when fenoxaprop was applied with pendimethalin, while fenoxaprop along with paraquat exerted maximum stimulation towards microbial biomass N (19.9 %) and biomass P (16.2 %). Application of fenoxaprop along with pendimethalin retained the highest amount of organic C (17.4 %), exchangeable NH₄ ⁺ (29 %) and available P (19.6 %), while fenoxaprop with paraquat augmented total N and soluble NO₃ ^? by 21.4 % and 25.2 %, respectively in soil.     

Effect of Two Herbicides on <Emphasis Type="Italic">Xenylla Welchi</Emphasis> (Hexapoda:Collembola) Under Laboratory Conditions

Xenylla welchi was used to evaluate toxicity of two herbicide formulations, pretilachlor (50 EC) and pendimethalin (30 EC) under laboratory conditions. Twenty four hours LC₅₀ value of pretilachlor and pendimethalin formulations on Xenylla welchi were 72.7 and 190.0 g a.i/ha respectively which were less than their corresponding recommended agricultural doses. Again pretilachlor attained fastest LT₅₀ (110 min) followed by pendimethalin (140 min). Significant reductions in hatching success were noted with the application of both the herbicide formulations at all doses excepting 1/₈ and ¹/₁₀th of LC₅₀ (9.1, 7.3 and 23.8, 19.0 g a.i/ha for pretilachlor and pendimethalin, respectively). Hatching success of the test specimens recorded 44.1 and 63.3% reduction from control for the highest applied dose (½ of LC₅₀) of pretilachlor and pendimethalin, respectively. Juveniles of Xenylla welchi exposed to ¹/₆, ¹/₈ and ¹/₁₀th LC₅₀ for pretilachlor (12.1, 9.1, 7.3 g a.i/ha) and ¹/₈ and ¹/₁₀th LC₅₀ for pendimethalin (23.8, 19.0 g ai/ha) survived and exhibited increased moulting frequency (7 moultings in 28 days in both the herbicide treatments) in comparison to control (8 moulting in 42 days). Test specimens required 26.0 ± 1.2 and 28.1 ± 2.1 days to attain sexual maturity exposed to pretilachlor and pendamethalin respectively which was significantly less than control (42 ± 2.6 days).     

Nitrous Oxide Emissions from Yellow Brown Soil as Affected by Incorporation of Crop Residues With Different Carbon-to-Nitrogen Ratios: A Case Study in Central China

To investigate the influence of crop residues decomposition on nitrous oxide (N₂O) emission, a field study was performed with application of crop residues with different C:N ratios in a bare yellow brown soil at the experimental station of Zhangjiachong at Zigui, China. We set up six experimental treatments: no crop residue (CK), rapeseed cake (RC), potato stalk (PS), rice straw (RS), wheat straw (WS), and corn straw (CS). The carbon (C) to nitrogen (N) ratios of these crop residues were 7.5, 32.9, 40.4, 65.7, and 90.9, respectively. Nitrous oxide fluxes were measured using a static closed chamber method. N₂O emissions were significantly enhanced by incorporation of crop residues. Cumulative N₂O emissions negatively correlated with C:N ratio (R ² = 0.9821) of the crop residue, but they were positively correlated with average concentrations of dissolved organic carbon and microbial biomass carbon. Nitrogen emission fraction, calculated as N₂O–N emissions originated from the crop residues N, positively correlated with C:N ratio of the residues (P < 0.05). Soil temperature did, whereas soil moisture did not, control the residue’s induced N₂O emissions because a significant correlation (P < 0.01) existed between soil temperature and N₂O emissions in all treatments except the control. In contrast, a significant relationship between soil moisture and N₂O emissions was found in the control only. Furthermore, N₂O emission significantly correlated (P < 0.05) with NO₃ ^––N, and NH₄ ⁺–N contents from all residue treatments. These results indicate that (1) crop residues with distinct carbon and nitrogen contents can significantly alter soil N₂O flux rates; and (2) soil biotic as well as abiotic variables are critical in determining soil–atmospheric N₂O emissions after crop residue incorporation into soil.     

Fly Ash Addition Affects Microbial Biomass and Carbon Mineralization in Agricultural Soils

The microbial biomass carbon (MBC) and carbon mineralization of fly ash (FA) amended soil at (0 %, 1.25 %, 2.5 %, 5 %, 10 % and 20 % FA; v/v) was investigated under laboratory conditions for 120 days at 60 % soil water-holding capacity and 25 ± 1°C temperature. The results demonstrated that soil respiration and microbial activities were not suppressed up to 2.5 % FA amendment and these activities decreased significantly at 10 % and 20 % FA treatment with respect to control. Application of 10 % and 20 % FA treated soils showed a decreasing trend of soil MBC with time; and the decrease was significant throughout the period of incubation. The study concluded that application of FA up to 2.5 % can thus be safely used without affecting the soil biological activity and thereby improve nutrient cycling in agricultural soils.     

Comparison of the Effects of Two Herbicides and an Insecticide on Tropical Freshwater Plankton in Microcosms

Natural plankton communities from a tropical freshwater reservoir (Combani Reservoir, Mayotte Island, Mozambique Channel) were exposed, in 20-l nutrient-enriched microcosms, to two nominal concentrations of three pesticides: the herbicides diuron (2.2 and 11 μg/l) and paraquat (10 and 40.5 μg/l) and the insecticide fenitrothion (10 and 100 μg/l), commonly used in the tropics for agriculture and disease vector control. Bacterioplankton, phytoplankton, and zooplankton communities were monitored for 5 days after exposure, and the concentrations of toxicant and major nutrients were measured. Bacterioplankton growth was noticeable in all systems and was slightly affected by pesticide at any concentration. A transitory increase in thymidine-based bacterial production was observed in diuron- and fenitrothion-treated microcosms, followed by a marked decrease in all microcosms after 5 days. The functional diversity of bacterioplankton, evaluated using BIOLOG ECO^® microplates, was reduced by exposure to the highest pesticide concentrations. Phytoplankton was affected by pesticides in different ways. Chlorophyll biomass and biovolumes were increased by diuron addition and decreased by paraquat, whereas fenitrothion-treated microcosms remained unaffected relative to controls. Phytoplankton taxonomic diversity was decreased by paraquat and high doses of fenitrothion but was unaffected by addition of diuron. The decrease in diversity was due to a reduction in the number of species, whereas the density of small cells increased, especially after addition of paraquat. Heterotrophic flagellates were sensitive to paraquat and to the highest diuron concentration; a reduction in biomass of up to 90% was observed for 40.5 μg/l paraquat. Zooplankton, dominated by Thermocyclops decipiens and Diaphanosoma excisum, was slightly sensitive to diuron, and very sensitive to paraquat. High concentrations of the insecticide fenitrothion were effective only on young stages. The potential direct and indirect effects of pesticide contamination on such a simplified plankton food web, typical of newly constructed reservoirs, appear to differ significantly depending on the biological compartment considered. The overall sensitivity of tropical plankton is comparable to the sensitivity for temperate systems, and direct and indirect effects appeared rapidly, within 5 days of exposure.     

A Method for Determination of Imazapic and Imazethapyr Residues in Soil Using an Ultrasonic Assisted Extraction and LC-MS/MS

At least 52 % of the planted rice area in Rio Grande do Sul, a major rice producing state in Brazil, employs Clearfield^® production system, corresponding to 580,000 ha of cultivated area. To grow rice with Clearfield^® technology, producers combine imazethapyr and imazapic herbicides. However, these herbicides leave residual activity in soil; consequently, the repeated application of imazethapyr and imazapic on Brazilian Clearfield^® rice fields has increased these herbicides persistence in treated soils. In this study, a method has been developed for removal and quantification of imazethapyr and imazapic residues in soil through ultrasonic assisted extraction using methanol–phosphoric acid aqueous solution (pH 2.0). The detected response was linear for both herbicides within the range of 0.25–5 ng mL^?1 with correlations coefficients >0.99. The quantification limit was limit of quantification 0.2 µg Kg^?1 for both pesticides. The good recovery rate from all pesticides, which ranges between 70 % and 120 %, demonstrates the method’s validity.     

Effect of Moisture, Organic Matter, Microbial Population and Fortification Level on Dissipation of Pyraclostrobin in Soils

The dissipation of pyraclostrobin, a strobilurin fungicide, in soil was found to be influenced by soil moisture, organic matter content and microbial population. Among the different moisture regimes, dissipation was faster under submerged condition (T_1/2 10 days) followed by field capacity (T_1/2 28.7 days) and in dry soil (T_1/2 41.8 days). Use of sludge at 5 % level to Inceptisol favoured a faster dissipation of pyraclostrobin, whereas a slower rate of dissipation was observed in partial organic matter removed soil as compared to normal soil. Slower rate of dissipation was also observed in sterile soil (T_1/2 47 days) compared to normal soil. Pyraclostrobin dissipated faster in Vertisol (T_1/2 21.8 days) than in Inceptisol (T_1/2 28.7 days). No significant difference in the dissipation rate was observed at 1 and 10 μg g^?1 fortification levels.     

Efficiency of C3 and C4 Plant Derived-Biochar for Cd Mobility,Nutrient Cycling and Microbial Biomass in Contaminated Soil

Biochar is considered a novel soil amendment to reduce metal mobility, but its influence on soil chemical and biochemical properties is not fully understood. In the present study, biochar derived from rice straw (RSB), rice hull (RHB), and maize stover (MSB) was used to evaluate comparative efficiency on Cd mobility and soil biochemical properties. Ammonium nitrate extractable Cd significantly decreased among all the applied biochar types and application rates. The European Community Bureau of Reference (BCR) technique showed significant decrease in acid-soluble Cd by 24%–32%, 19%–23%, and 22%–27% for RSB, RHB, and MSB, respectively at the 1.5% and 3% rate. However, the concentration of Cd in the residual increased by 38%, 35% and 36% for RSB, RHB and MSB, respectively at a 3% application rate. Soil microbial biomass (C and N) and inorganic nitrogen forms (NH₄ and NO₃) significantly increased among all biochar applications. Overall, RSB demonstrated positive results as soil amendments for Cd immobilization, increasing soil nutrient availability, and enhancing soil microbial biomass.     

Exacerbation of symptoms in agricultural pesticide applicators with asthma

Purpose

Exacerbation is a critical event in asthma management. We investigated whether exacerbation of symptoms is associated with farming exposures among agricultural pesticide applicators with asthma.

Methods

Participants were pesticide applicators with active asthma (wheezing and breathing problems in past 12 months) who completed enrollment questionnaires for the Agricultural Health Study (AHS). Exacerbation of asthma was defined as having visited a hospital emergency room or doctor for an episode of wheezing or whistling in the past 12 months. Exposures of interest were using 36 specific pesticides in the past 12 months and conducting various agricultural activities. Adjusted odds ratios (ORs) were estimated by logistic regression while controlling for potential confounders.

Results

The 926 AHS adult pesticide applicators with active asthma included 202 (22 %) with exacerbation. Inverse associations with exacerbation were observed for two herbicides [glyphosate, odds ratio (OR) = 0.5, 95 % confidence interval (CI) 0.3, 0.8, and paraquat, OR = 0.3, 95 % CI 0.1, 0.9] and several agricultural activities (repairing engines, grinding metal, driving diesel tractors, and performing veterinary procedures). Only asthma cases with allergies (i.e., doctor-diagnosed hay fever or eczema, 46 %) had positive exacerbation–pesticide associations, with OR = 2.1 (95 % CI 1.1, 4.1) for the herbicide pendimethalin and OR = 10.2 (95 % CI 1.9, 55) for the insecticide aldicarb.

Conclusions

The inverse associations with two pesticides and specific farm activities are consistent with the possibility that asthma cases prone to exacerbation may avoid exposures that trigger symptoms. Although limited by small sample size and a cross-sectional design, our study suggests that use of specific pesticides may contribute to exacerbation of asthma among individuals with allergies.     

Influence of the Activity of Allobophora molleri in Microbial Activity and Metal Availability of Arsenic-Polluted Soils

We investigate the use of Allolobophora molleri as a biomarker of arsenic (As)-polluted soils and study the influence of A. molleri on the metabolic activity and microbial biodiversity of soil polluted with As. Because there are no experimental data available regarding the effect of the pollutant rate of As on A. molleri, we determined the LC₅₀ that was 143.5 mg As kg^?1. Sodium arsenite was added at two rates, equivalent to 143.5 and 71.8 mg As kg^?1 soil, to a soil that was then maintained with and without worms for 120 days. In addition, a nonpolluted soil without and with earthworms was used as the control. The As concentration in the soil was measured after 7 and 120 and the worm weight and As concentration after 120 days of exposure. Soil enzymatic activities and the structure of the soil microbial community, by analysis of phospholipid fatty acids, were determined. At the end of the experiment, the highest earthworm As contents were found in soils polluted with the highest rate of As. Earthworm weights significantly decreased in soil polluted with 143.5 or 71.8 mg As kg^?1, by 49.9 and 29.8 % of initial weight, because the worm consumption rate decreased. These results suggest that A. molleri can be used as a good biomarker of the As toxicity. The As available fraction decreased in polluted soil with worms because the metal was accumulated in worm tissues. However, this assimilation was lower than other worms such as L. rubbellus or L. terrestris. Soil enzymatic activities were decreased in As-polluted soils but were increased significantly by the presence of earthworms. The earthworms modified the soil microbial diversity. In this respect, A. molleri significantly increased (p < 0.05) the bacterial and fungal populations. Soil As pollution decreased microbial biodiversity but to a lesser extent in the presence of A. molleri.     

Influences of inorganic and polycyclic aromatic hydrocarbons on the sources of PM2.5 in the Southeast Asian urban sites

PM_2.5 released from urban sources and regional biomass fire is of great concern due to the deleterious effect on human health. This study was conducted to determine the chemical compositions andsource apportionment of PM_2.5. Twenty-four-hour PM_2.5 samples were collected at two urban monitoring sites in Kuala Lumpur, Malaysia, from 12 November 2013 to 15 January 2014 using a high volume air sampler (HVS). The source apportionment of PM_2.5 was determined using positive matrix factorization (PMF) version 5.0. Overall, the PM_2.5 mean concentrations ranged from 16 to 55 μg m^?3 with a mean of 23 ± 9 μg m^?3. The results of enrichment factor (EF) analysis showed that Zn, Pb, As, Cu, Cr, V, Ni, and Cs mainly originated from non-crustal sources. The dominant polycyclic aromatic hydrocarbons (PAHs) were benzo[b]fluoranthene (B[b]F), benzo[ghi]perylene (B[ghi]P), indeno[1,2,3-cd]pyrene (I[cd]P), benzo[a]pyrene (B[a]P) and benzo[k]fluoranthene (B[k]F). PMF 5.0 results showed that the secondary aerosol coupled with biomass burning was the largest contributor followed by combustion of fuel oil and road dust, soil dust source and sea salt and nitrate aerosol, accounting for 34, 25, 24 and 17% of PM_2.5 mass, respectively. On the other hand, biomass and wood burning (42%) was the predominant source of PAHs followed by combustion of fossil fuel (36%) and natural gas and coal burning (22%). The broad overview of the PM_2.5 sources will help to adopt adequate mitigation measures in the management of future urban air quality in this region.     

Bioavailability of Metsulfuron and Sulfentrazone Herbicides in Soil as Affected by Amendment with Two Contrasting Willow Biochars

This study investigated the effect of two willow (Salix spp.) biochars, produced using either fast- or slow-pyrolysis, on the bioavailability of metsulfuron and sulfentrazone herbicides in soil. Five rates (0%, 1%, 2%, 3%, and 4%; w/w) of each biochar were used, along with varying rates of metsulfuron (0–3.2 µg ai kg^?1) and sulfentrazone (0–200 µg ai kg^?1), followed by a sugar beet bioassay. The fast-pyrolysis biochar had minimal effect, while the slow-pyrolysis biochar decreased the bioavailability of both herbicides. Despite using the same feedstock, the two biochars had different physical and chemical properties, of which specific surface area was most contrasting (3.0 and 175 m² g^?1 for fast- and slow-pyrolysis biochar, respectively). Increased anionic herbicide adsorption associated with greater surface area of the slow-pyrolysis biochar is considered to be the primary mechanism responsible for reducing herbicide bioavailability with this biochar.     

Dissipation and Dynamics of Mesotrione in Maize and Soil Under Field Ecosystem

Modified QuEChERS-HLPC (quick, easy, cheap, effective, rugged and safe) methods for the analysis of mesotrione in maize and soil were developed and validated. At three fortification levels of 0.01, 0.1 and 0.5 mg kg^?1 mesotrione, the recoveries of mesotrione in maize plants, maize and soil were in the range of 85.95 %–96.05 %, with relative standard deviations (RSD) of 2.89 %–9.83 %. The limit of quantification (LOQ) of method was 0.001 mg kg^?1 for maize and soil. In the supervised field trials, the degradation rates of mesotrione were described using first-order kinetics and mesotrione dissipation in maize plants coincided with C _t  = 1.735e^?1.0194t with the half-life 3.94 days in Tianjin, and C _t  = 4.9536e^?0.7237t with the half-life 5.10 days in Jilin. As for soil, C _t  = 20.272e^?1.208t with the half-life 2.98 days in Tianjin, and C _t  = 5.5835e^?8141t with the half-life 4.49 days in Jilin. At pre-harvest interval (PHI) of 0 and 20 days, the final residue levels of mesotrione could not be detected in maize and soil at the recommended dosage and 1.5 times recommended dosage.     

Investigating Pseudomonas putida–Candida humicola Interactions as Affected by Chelate Fe(III) in Soil

Microcalorimetric technique was applied to assess the toxic effect of EDTA-chelated trivalent iron on Pseudomonas putida (P. putida) (bacterium), Candida humicola (C. humicola) (fungus) and their mixture in sterilized soil. Microbial growth rate constant k, total heat evolution Q _T, metabolic enthalpy ?H _met, mass specific heat rate J _Q/S, microbial biomass C and inhibitory ratio I were calculated. Results showed that microcalorimetric indexes decreased with the increasing Fe(III)-EDTA complex concentration. Comparing the single and mixed strains, the effect of Fe(III) on bacterium-fungus interaction was dominant at lower dose, whereas, the metal toxicity at high dose of Fe was the main factor affecting P. putida and C. humicola activity. Thus, the mixture had moderate tolerance to the iron overload, and exhibit synergistic interaction in exponential growth phase (0–0.3 mg g^?1). The results of glucose degradation showed that glucose was consumed totally at the end of exponential phase of microbial growth.     

Individual and Joint Toxicity of Three Chloroacetanilide Herbicides to Freshwater Cladoceran Daphnia carinata

Individual and joint toxicity of three chloroacetanilide herbicides to a freshwater cladoceran were studied. The 48 h-LC₅₀ values of alachlor, acetochlor and butachlor to Daphnia carinata Dc42 were 11.1, 11.8 and 3.45 mg L^?1, respectively. The toxicity was significantly (p < 0.05) related to hydrophobicity. The additive indexes of binary mixtures of three herbicides were less than zero and it showed antagonism. The body length of D. carinata treated with high concentration of herbicides was shorter than that of control group significantly (p < 0.05). It suggests that joint actions must be considered when assessing the acute toxicity of chloroacetanilide herbicides to D. carinata.     

A Combination Method to Study the Effects of Petroleum on Soil Microbial Activity

TAM III multi-channel calorimetry was applied to study the effect of different concentrations petroleum on soil microbial activity and community. The microbial activities of the soil samples were recorded as power-time curves. The thermokinetic parameters such as microbial growth rate constant k, total heat evolution Q _T, metabolic enthalpy ?H _met and mass specific heat rate J _Q/S were calculated. Results showed that petroleum had a certain extent effects to soil microorganisms. The results indicate that the soil microbial activity was promoted with a petroleum concentration lower than 0.52 % ± 0.24 %, but inhibited with further increase in petroleum.     

A Comparative Study on the Impact of Phthalate Esters on Soil Microbial Activity

In this study, an isothermal microcalorimetric technique was used to demonstrate the impact of dimethyl phthalate (DMP), di-n-octyl phthalate (DOP) and diethyl phthalate (DEP) on soil microbial activity. The effect of these phthalate esters (≤100 μg g^?1 soil) follows the order: DEP > DMP > DOP but changed to DMP > DEP > DOP when the concentrations of the phthalate esters are above 100 μg g^?1 soil. DMP, DEP and DOP significantly decreased (p < 0.05) the soil urease activity. The effect of phthalate esters on soil microbial activity is not the same with those on enzymatic activity. In addition, DEP, which has a lower bioavailability, is less toxic to soil microbes than that of DMP when its concentration is above 100 μg g^?1 soil.     

Major chemical compositions,possible sources,and mass closure analysis of PM2.5 in Jinan,China

The fine particulate matter samples for 24 h were carried out at the Environment Monitoring Station (EMS) and Shandong Jianzhu University (SJU) sites during 2010 in Jinan City, China. Eight water-soluble ion species were analyzed by ion chromatography, while organic carbon (OC) and elemental carbon (EC) were determined with the IMPROVE thermal optical reflectance method, and 20 inorganic elements were measured by inductively coupled plasma-atomic emission spectrometer and inductively coupled plasma-mass spectroscopy. The annual average mass concentration of PM_2.5 was 168.85 μg m^?3 at EMS and 148.67 μg m^?3 at SJU. The coefficient of divergence was 0.14, 0.19, 0.23, and 0.23 in spring, summer, fall, and winter, respectively, indicating that there was no obvious spatial difference at the two sampling sites. The highest PM_2.5, OC, and OC/EC ratio were in winter because of the enhanced emissions from coal combustion for heating and poor atmospheric dispersion. By the method of enrichment factors, the 20 inorganic elements were divided into three types owing to their sources. Al, Si, and Ti were mainly contributed by crustal sources. Na, Mg, P, K, Ca, V, Cr, Mn, Fe, Co, Ni, Ba, and Sr were from both natural emissions and anthropogenic sources. Cu, Zn, Pb, and Sn mainly originated from anthropogenic sources such as vehicular exhaust and industrial emission. Chemical mass closure calculation estimated that SO₄ ^2? was the largest contributor and explained 29.66 % of PM_2.5 mass at EMS, while 31.64 % was at SJU. The organic matter, crustal matter, and NO₃ ^–, respectively, accounted for 15.12, 12.87, and 13.77 % to PM_2.5 at EMS, while it accounted for 13.46, 13.96, and 14.93 % at SJU, respectively. By the positive matrix factorization analysis, the coal combustion and biomass burning, secondary sulfate, soil dust, secondary nitrate, and vehicle emissions were identified as the major emission sources.     

Effects of Complex Pollution of Pb and B[a]P on the Growth and Physiological and Biochemical Indexes of Ryegrass

Effects of complex pollution of Pb and B[a]P on the growth and physiological and biochemical indexes of ryegrass were investigated in a potted soil. The results showed that under single Pb treatment condition, low-concentration (0–100 mg kg^?1) Pb stimulated the increase of ryegrass biomass while high-concentration (200–400 mg kg^?1) Pb obviously inhibited ryegrass growth. Under single B[a]P pollution condition, low-concentration (0–30 mg kg^?1) B[a]P facilitated the growth of ryegrass while high-concentration (50–100 mg kg^?1) B[a]P had toxic effect on ryegrass. Under joint impacts of Pb and B[a]P at low concentrations, biomass, chlorophyll content and carotenoid content as well as POD and CAT activities of ryegrass presented firstly rising and then descending trends, SOD accumulation increased slightly and MDA didn’t experience obvious change. Under co-existence of Pb and B[a]P, Pb was the main toxic factor for ryegrass growth and it controlled the variation trend of whole growth cycle of ryegrass.     

Toxicity Assessment of Herbicides Quizalafop-p-Ethyl and Clodinafop Towards Rhizobium Pea Symbiosis

In modern conventional agriculture, herbicides are frequently used to prevent yield losses due to weeds. Herbicides also affect negatively the productivity of legumes. With these considerations, we evaluated the effects of soil applications of different concentrations of quizalafop-p-ethyl and clodinafop on the performance of Rhizobium inoculated pea, grown in clay pots. In this study, the concentration of herbicides higher than the recommended rates of quizalafop-p-ethyl and clodinafop adversely affected the dry matter accumulation, symbiotic properties, grain yield and nutrient status of pea plants. Toxicity of quizalafop-p-ethyl and clodinafop to pea plants increased progressively with increase in rates of herbicides. Of the two herbicides, quizalafop-p-ethyl was more toxic than clodinafop. In contrast, when herbicide tolerant Rhizobium strain MRP1 was also used with herbicide, it increased the measured parameters at all concentrations. A maximum increase of 11%, 17%, 46%, 33%, 21% and 7% in the root N, shoot N, root P, shoot P, seed yield and seed protein, respectively, was observed when MRP1 was used with 120 μg quizalafop-p-ethyl kg⁻¹ soil while with 1,200 μg clodinafop kg⁻¹ soil it increased the root N, shoot N, root P, shoot P, seed yield and seed protein by 20%, 9%, 56%, 56%, 29% and 7%, respectively, compared with the un-inoculated but herbicide treated control. This study suggested that the toxic effects of herbicides on pea plants could be attenuated by applying growth promoting herbicide tolerant strain of Rhizobium under herbicide stressed soil environment.