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María E. Báez - One of the best experts on this subject based on the ideXlab platform.
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sorption desorption behavior of pesticides and their degradation products in volcanic and nonvolcanic soils interpretation of interactions through two way principal component analysis
Environmental Science and Pollution Research, 2015Co-Authors: María E. Báez, Jeannette Espinoza, Ricardo Silva, Edwar FuentesAbstract:Sorption-desorption behavior of six pesticides and some degradation products was assessed on seven agricultural volcanic and nonvolcanic soils belonging to Andisol, Ultisol, Mollisol, and Alfisol orders. The global interpretation of sorption data was performed by principal component analysis. Results showed exceptionally high sorption of glyphosate and aminomethylphosphonic acid (AMPA) (the breakdown product) on volcanic soils (Kf > 1500 μg1 − 1 / n mL1 / n g−1) related mainly to contents of amorphous aluminum oxides (Andisols) and crystalline minerals (Ultisols). The lower sorption on nonvolcanic soils was associated to low organic matter contents and lack of significant minerals. Metsulfuron-methyl and 3,5,6-trichloro-2-pyridinol (metabolite of chlorpyrifos) were weakly to substantially sorbed on Andisols and Ultisols, but the first one was not sorbed at pH > 6.4, including nonvolcanic soils. The metabolite of diazinon, 2-isopropyl-4-methyl-6-hydroxypyrimidine, was weakly sorbed on all soils (Kf = 0.4 to 3.6 μg1 − 1 / n mL1 / n g−1). Acidic compounds would be lixiviated in Mollisols and Alfisols, but they could leach also in Andisols and Ultisols if they reach greater depths. Atrazine and deethylatrazine sorption was related to organic carbon content; therefore, they were weakly retained on nonvolcanic soils (Kf = 0.7 to 2.2 μg1 − 1 / n mL1 / n g−1). Chlorpyrifos was highly sorbed on all soils reaching KOC values of >8000. Finally, the significant retention of chlorothalonil and diazinon on Mollisols and Alfisols in spite of their low OC contents showed the contribution of clay minerals in the sorption process.
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characterization of the atrazine sorption process on andisol and ultisol volcanic ash derived soils kinetic parameters and the contribution of humic fractions
Journal of Agricultural and Food Chemistry, 2013Co-Authors: María E. Báez, Edwar Fuentes, Jeannette EspinozaAbstract:Atrazine sorption was studied in six Andisol and Ultisol soils. Humic and fulvic acids and humin contributions were established. Sorption on soils was well described by the Freundlich model. Kf values ranged from 2.2–15.6 μg1–1/nmL1/ng–1. The relevance of humic acid and humin was deduced from isotherm and kinetics experiments. KOC values varied between 221 and 679 mLg–1 for these fractions. Fulvic acid presented low binding capacity. Sorption was controlled by instantaneous equilibrium followed by a time-dependent phase. The Elovich equation, intraparticle diffusion model, and a two-site nonequilibrium model allowed us to conclude that (i) there are two rate-limited phases in Andisols related to intrasorbent diffusion in organic matter and retarded intraparticle diffusion in the organo–mineral complex and that (ii) there is one rate-limited phase in Ultisols attributed to the mineral composition. The lower organic matter content of Ultisols and the slower sorption rate and mechanisms involved must be cons...
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modeling the sorption kinetic of metsulfuron methyl on Andisols and ultisols volcanic ash derived soils kinetics parameters and solute transport mechanisms
Journal of Hazardous Materials, 2010Co-Authors: Lizethly Caceres, Edwar Fuentes, Mauricio Escudey, María E. BáezAbstract:Metsulfuron-methyl sorption kinetic was studied in Andisol and Ultisol soils in view of their distinctive physical and chemical properties: acidic pH and variable surface charge. Different kinetic models were applied to the experimental results. The pseudo-second-order model fitted sorption kinetics data better than the pseudo-first-order model. The rate constant and the initial rate constant values obtained through this model demonstrated the different behavior of metsulfuron-methyl in both kinds of soils, both parameters being the highest for Andisol. The application of Elovich equation, intraparticle diffusion model and a two-site nonequilibrium model (TSNE) allowed to conclude that: (i) the high organic matter content is the governing factor for Andisols where mass transfer across the boundary layer, and in a lesser degree, intraparticle diffusion were the two processes controlling sorption kinetic and (ii) the mineral composition was more relevant in Ultisols where rate was controlled almost exclusively by intraparticle diffusion into macropores and micropores. The slower sorption rate on Ultisols, the mechanism involved and the lower sorption capacity of this kind of soils must be taken into account to assess leaching behavior of this herbicide.
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metsulfuron methyl sorption desorption behavior on volcanic ash derived soils effect of phosphate and ph
Journal of Agricultural and Food Chemistry, 2010Co-Authors: Lizethly Caceres, Edwar Fuentes, Mauricio Escudey, Roxana Fuentes, María E. BáezAbstract:Metsulfuron-methyl sorption/desorption behavior was studied through batch sorption experiments in three typical volcanic ash-derived soils belonging to Andisol and Ultisol orders. Their distinctive physical and chemical properties are acidic pH and variable surface charge. Organic matter content and mineral composition affected in different ways sorption of metsulfuron-methyl (KOC ranging from 113 to 646 mL g -1 ): organic matter and iron and aluminum oxides mainly through hydrophilic rather than hydrophobic interactions in Andisols, and Kaolinite group minerals, as major constituents of Ultisols, and iron and aluminum oxides only through hydrophilic interactions. The Freundlich model described metsulfuron-methyl behavior in all cases (R 2 > 0.992). Kf values (3.1-14.4 μg 1-1/n mL 1/n g -1 ) were higher than those reported for different class of soils including some with variable charge. Hysteresis was more significant in Ultisols. A strong influence of pH and phosphate was established for both kinds of soil, intensive soil fertilization and liming being the most probable scenario for leaching of metsulfuron-methyl, particularly in Ultisols.
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adsorption of glyphosate on variable charge volcanic ash derived soils
Journal of Environmental Quality, 2009Co-Authors: L Caceresjensen, María E. Báez, Jianying Gan, Romulo Fuentes, Mauricio EscudeyAbstract:Glyphosate (N-phosphonometylglycine) is widely used due to its broad spectrum of activity and nonselective mode of action. In Chile it is the most used herbicide, but its adsorption behavior in the abundant and widespread variable charge soils is not well understood. In this study, three volcanic ash-derived soils were selected, including Andisols (Nueva Braunau and Diguillin) and Ultisols (Collipulli), to evaluate the adsorption kinetics, equilibrium isotherms, and the effect of pH in glyphosate adsorption. The influence of glyphosate on soil phosphorus retention was also studied. Glyphosate was rapidly and strongly adsorbed on the selected soils, and adsorption isotherms were well described by the Freundlich relationship with strong nonlinearity (n(fads) < 0.5). The n(fads) values were consistently higher than n(fdes) values, suggesting strong hysteresis. Adsorption (K(ads)) increased strongly when pH decreased. The presence of glyphosate (3200 mug mL(-1)) changed the adsorption behavior of phosphate at its maximum adsorption capacity. Andisol soils without the addition of glyphosate had similar mean K(ads) values for Nueva Braunau (5.68) and Diguillin (7.38). Collipulli had a mean K(ads) value of 31.58. During the successive desorption steps, glyphosate at the highest level increased K(ads) values for phosphate in the Andisol soils but had little effect in the Ultisol soil. This different behavior was probably due to the irreversible occupation of some adsorption sites by glyphosate in the Ultisol soil attributed to the dominant Kaolinite mineral. Results from this study suggest that in the two types of volcanic soils, different mechanisms are involved in glyphosate and phosphate adsorption and that long-term use of glyphosate may impose different effects on the retention and availability of phosphorus. Volcanic ash-derived soils have a particular environmental behavior in relation to the retention of organic contaminants, representing an environmental substrate that may become highly polluted over time due to intensive agronomic uses.
Mauricio Escudey - One of the best experts on this subject based on the ideXlab platform.
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Study of Sorption Kinetics and Sorption–Desorption Models to Assess the Transport Mechanisms of 2,4-Dichlorophenoxyacetic Acid on Volcanic Soils
'MDPI AG', 2021Co-Authors: Lizethly Cáceres-jensen, Mauricio Escudey, Jorge Rodríguez-becerra, Carlos Garrido, Lorena Barrientos, Jocelyn Parra-rivero, Valentina Domínguez-vera, Bruno Loch-arellanoAbstract:The sorption behavior of 2,4-dichlorophenoxyacetic acid (2,4-D) in the abundant agricultural volcanic ash-derived soils (VADS) is not well understood despite being widely used throughout the world, causing effects to the environment and human health. The environmental behavior and risk assessment of groundwater pollution by pesticides can be evaluated through kinetic models. This study evaluated the sorption kinetics and 2,4-D sorption–desorption in ten VADS through batch sorption experiments. Differences in the sorption extent for the fast and slow phases was observed through the IPD model where 2,4-D sorption kinetics was controlled by external mass transfer and intra organic matter diffusion in Andisols (C1 ≠ 0). We confirmed from the spectroscopic analysis that the carboxylate group directly drives the interaction of 2,4-D on Andisol soil. The MLR model showed that IEP, FeDCB, and pH×Silt are important soil descriptors in the 2,4-D sorption in VADS. The Freundlich model accurately represented sorption equilibrium data in all cases (Kf values between 1.1 and 24.1 µg1−1/n mL1/ng−1) with comparatively higher sorption capacity on Andisols, where the highest hysteresis was observed in soils that presented the highest and lowest OC content (H close to 0)
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kinetics adsorption and desorption of cd ii and cu ii on natural allophane effect of iron oxide coating
Geoderma, 2018Co-Authors: Jorge Silvayumi, Mauricio Escudey, Manuel Gacitua, Carmen PizarroAbstract:Abstract Volcanic soils are a potential source of abundant and low-cost adsorbent materials. Allophane and iron oxides are the main inorganic constituents of Andisols, soils derived from volcanic-ashes abundant in the central and southern continental Chilean territory. The present study aimed to elucidate the effect of free iron oxides on the adsorption of Cd(II) and Cu(II) from aqueous media on natural allophane (NA). Allophane samples consisted of natural allophane, obtained from a Chilean Andisol series, with (NA-FeOx) and without (NA) an iron oxide coating. Material characterisation showed that NA-FeOx was formed by nanometric (100–500 nm) sized spheres coated with an iron oxide layer that most likely consisted of a ferrihydrite-like mineral. On the other hand, NA consisted of aggregates (with particles as big as 1.0 μm) mostly constituted by allophane. The specific surface area of NA-FeOx and NA were ca. 150 and 17 m2 g− 1, respectively, and presented variable surface charge with an isoelectric point of 10.3. and 5.4. From the kinetic studies, equilibrium adsorption was achieved within 60 min and was almost independent of the presence of the iron oxides. Among the kinetic models evaluated, the pseudo-second order model presented a better correlation with the experimental data. The adsorption studies revealed that NA has a greater adsorption capacity of both Cd+ 2 and Cu+ 2 compared to NA-FeOx. Langmuir and Freundlich adsorption models fit the experimental data well, suggesting that the adsorption process is a combination of physical and chemical phenomena. The Freundlich constant (adsorption coefficient, KF) values obtained confirmed the superior affinity of NA active surface sites compared to NA-FeOx. Desorption studies demonstrated that the majority of adsorbed cations were retained by the adsorbent, indicating irreversible chemical adsorption on specific active sites of the adsorbents.
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modeling the sorption kinetic of metsulfuron methyl on Andisols and ultisols volcanic ash derived soils kinetics parameters and solute transport mechanisms
Journal of Hazardous Materials, 2010Co-Authors: Lizethly Caceres, Edwar Fuentes, Mauricio Escudey, María E. BáezAbstract:Metsulfuron-methyl sorption kinetic was studied in Andisol and Ultisol soils in view of their distinctive physical and chemical properties: acidic pH and variable surface charge. Different kinetic models were applied to the experimental results. The pseudo-second-order model fitted sorption kinetics data better than the pseudo-first-order model. The rate constant and the initial rate constant values obtained through this model demonstrated the different behavior of metsulfuron-methyl in both kinds of soils, both parameters being the highest for Andisol. The application of Elovich equation, intraparticle diffusion model and a two-site nonequilibrium model (TSNE) allowed to conclude that: (i) the high organic matter content is the governing factor for Andisols where mass transfer across the boundary layer, and in a lesser degree, intraparticle diffusion were the two processes controlling sorption kinetic and (ii) the mineral composition was more relevant in Ultisols where rate was controlled almost exclusively by intraparticle diffusion into macropores and micropores. The slower sorption rate on Ultisols, the mechanism involved and the lower sorption capacity of this kind of soils must be taken into account to assess leaching behavior of this herbicide.
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metsulfuron methyl sorption desorption behavior on volcanic ash derived soils effect of phosphate and ph
Journal of Agricultural and Food Chemistry, 2010Co-Authors: Lizethly Caceres, Edwar Fuentes, Mauricio Escudey, Roxana Fuentes, María E. BáezAbstract:Metsulfuron-methyl sorption/desorption behavior was studied through batch sorption experiments in three typical volcanic ash-derived soils belonging to Andisol and Ultisol orders. Their distinctive physical and chemical properties are acidic pH and variable surface charge. Organic matter content and mineral composition affected in different ways sorption of metsulfuron-methyl (KOC ranging from 113 to 646 mL g -1 ): organic matter and iron and aluminum oxides mainly through hydrophilic rather than hydrophobic interactions in Andisols, and Kaolinite group minerals, as major constituents of Ultisols, and iron and aluminum oxides only through hydrophilic interactions. The Freundlich model described metsulfuron-methyl behavior in all cases (R 2 > 0.992). Kf values (3.1-14.4 μg 1-1/n mL 1/n g -1 ) were higher than those reported for different class of soils including some with variable charge. Hysteresis was more significant in Ultisols. A strong influence of pH and phosphate was established for both kinds of soil, intensive soil fertilization and liming being the most probable scenario for leaching of metsulfuron-methyl, particularly in Ultisols.
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adsorption of glyphosate on variable charge volcanic ash derived soils
Journal of Environmental Quality, 2009Co-Authors: L Caceresjensen, María E. Báez, Jianying Gan, Romulo Fuentes, Mauricio EscudeyAbstract:Glyphosate (N-phosphonometylglycine) is widely used due to its broad spectrum of activity and nonselective mode of action. In Chile it is the most used herbicide, but its adsorption behavior in the abundant and widespread variable charge soils is not well understood. In this study, three volcanic ash-derived soils were selected, including Andisols (Nueva Braunau and Diguillin) and Ultisols (Collipulli), to evaluate the adsorption kinetics, equilibrium isotherms, and the effect of pH in glyphosate adsorption. The influence of glyphosate on soil phosphorus retention was also studied. Glyphosate was rapidly and strongly adsorbed on the selected soils, and adsorption isotherms were well described by the Freundlich relationship with strong nonlinearity (n(fads) < 0.5). The n(fads) values were consistently higher than n(fdes) values, suggesting strong hysteresis. Adsorption (K(ads)) increased strongly when pH decreased. The presence of glyphosate (3200 mug mL(-1)) changed the adsorption behavior of phosphate at its maximum adsorption capacity. Andisol soils without the addition of glyphosate had similar mean K(ads) values for Nueva Braunau (5.68) and Diguillin (7.38). Collipulli had a mean K(ads) value of 31.58. During the successive desorption steps, glyphosate at the highest level increased K(ads) values for phosphate in the Andisol soils but had little effect in the Ultisol soil. This different behavior was probably due to the irreversible occupation of some adsorption sites by glyphosate in the Ultisol soil attributed to the dominant Kaolinite mineral. Results from this study suggest that in the two types of volcanic soils, different mechanisms are involved in glyphosate and phosphate adsorption and that long-term use of glyphosate may impose different effects on the retention and availability of phosphorus. Volcanic ash-derived soils have a particular environmental behavior in relation to the retention of organic contaminants, representing an environmental substrate that may become highly polluted over time due to intensive agronomic uses.
Edwar Fuentes - One of the best experts on this subject based on the ideXlab platform.
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sorption desorption behavior of pesticides and their degradation products in volcanic and nonvolcanic soils interpretation of interactions through two way principal component analysis
Environmental Science and Pollution Research, 2015Co-Authors: María E. Báez, Jeannette Espinoza, Ricardo Silva, Edwar FuentesAbstract:Sorption-desorption behavior of six pesticides and some degradation products was assessed on seven agricultural volcanic and nonvolcanic soils belonging to Andisol, Ultisol, Mollisol, and Alfisol orders. The global interpretation of sorption data was performed by principal component analysis. Results showed exceptionally high sorption of glyphosate and aminomethylphosphonic acid (AMPA) (the breakdown product) on volcanic soils (Kf > 1500 μg1 − 1 / n mL1 / n g−1) related mainly to contents of amorphous aluminum oxides (Andisols) and crystalline minerals (Ultisols). The lower sorption on nonvolcanic soils was associated to low organic matter contents and lack of significant minerals. Metsulfuron-methyl and 3,5,6-trichloro-2-pyridinol (metabolite of chlorpyrifos) were weakly to substantially sorbed on Andisols and Ultisols, but the first one was not sorbed at pH > 6.4, including nonvolcanic soils. The metabolite of diazinon, 2-isopropyl-4-methyl-6-hydroxypyrimidine, was weakly sorbed on all soils (Kf = 0.4 to 3.6 μg1 − 1 / n mL1 / n g−1). Acidic compounds would be lixiviated in Mollisols and Alfisols, but they could leach also in Andisols and Ultisols if they reach greater depths. Atrazine and deethylatrazine sorption was related to organic carbon content; therefore, they were weakly retained on nonvolcanic soils (Kf = 0.7 to 2.2 μg1 − 1 / n mL1 / n g−1). Chlorpyrifos was highly sorbed on all soils reaching KOC values of >8000. Finally, the significant retention of chlorothalonil and diazinon on Mollisols and Alfisols in spite of their low OC contents showed the contribution of clay minerals in the sorption process.
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characterization of the atrazine sorption process on andisol and ultisol volcanic ash derived soils kinetic parameters and the contribution of humic fractions
Journal of Agricultural and Food Chemistry, 2013Co-Authors: María E. Báez, Edwar Fuentes, Jeannette EspinozaAbstract:Atrazine sorption was studied in six Andisol and Ultisol soils. Humic and fulvic acids and humin contributions were established. Sorption on soils was well described by the Freundlich model. Kf values ranged from 2.2–15.6 μg1–1/nmL1/ng–1. The relevance of humic acid and humin was deduced from isotherm and kinetics experiments. KOC values varied between 221 and 679 mLg–1 for these fractions. Fulvic acid presented low binding capacity. Sorption was controlled by instantaneous equilibrium followed by a time-dependent phase. The Elovich equation, intraparticle diffusion model, and a two-site nonequilibrium model allowed us to conclude that (i) there are two rate-limited phases in Andisols related to intrasorbent diffusion in organic matter and retarded intraparticle diffusion in the organo–mineral complex and that (ii) there is one rate-limited phase in Ultisols attributed to the mineral composition. The lower organic matter content of Ultisols and the slower sorption rate and mechanisms involved must be cons...
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modeling the sorption kinetic of metsulfuron methyl on Andisols and ultisols volcanic ash derived soils kinetics parameters and solute transport mechanisms
Journal of Hazardous Materials, 2010Co-Authors: Lizethly Caceres, Edwar Fuentes, Mauricio Escudey, María E. BáezAbstract:Metsulfuron-methyl sorption kinetic was studied in Andisol and Ultisol soils in view of their distinctive physical and chemical properties: acidic pH and variable surface charge. Different kinetic models were applied to the experimental results. The pseudo-second-order model fitted sorption kinetics data better than the pseudo-first-order model. The rate constant and the initial rate constant values obtained through this model demonstrated the different behavior of metsulfuron-methyl in both kinds of soils, both parameters being the highest for Andisol. The application of Elovich equation, intraparticle diffusion model and a two-site nonequilibrium model (TSNE) allowed to conclude that: (i) the high organic matter content is the governing factor for Andisols where mass transfer across the boundary layer, and in a lesser degree, intraparticle diffusion were the two processes controlling sorption kinetic and (ii) the mineral composition was more relevant in Ultisols where rate was controlled almost exclusively by intraparticle diffusion into macropores and micropores. The slower sorption rate on Ultisols, the mechanism involved and the lower sorption capacity of this kind of soils must be taken into account to assess leaching behavior of this herbicide.
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metsulfuron methyl sorption desorption behavior on volcanic ash derived soils effect of phosphate and ph
Journal of Agricultural and Food Chemistry, 2010Co-Authors: Lizethly Caceres, Edwar Fuentes, Mauricio Escudey, Roxana Fuentes, María E. BáezAbstract:Metsulfuron-methyl sorption/desorption behavior was studied through batch sorption experiments in three typical volcanic ash-derived soils belonging to Andisol and Ultisol orders. Their distinctive physical and chemical properties are acidic pH and variable surface charge. Organic matter content and mineral composition affected in different ways sorption of metsulfuron-methyl (KOC ranging from 113 to 646 mL g -1 ): organic matter and iron and aluminum oxides mainly through hydrophilic rather than hydrophobic interactions in Andisols, and Kaolinite group minerals, as major constituents of Ultisols, and iron and aluminum oxides only through hydrophilic interactions. The Freundlich model described metsulfuron-methyl behavior in all cases (R 2 > 0.992). Kf values (3.1-14.4 μg 1-1/n mL 1/n g -1 ) were higher than those reported for different class of soils including some with variable charge. Hysteresis was more significant in Ultisols. A strong influence of pH and phosphate was established for both kinds of soil, intensive soil fertilization and liming being the most probable scenario for leaching of metsulfuron-methyl, particularly in Ultisols.
Lizethly Caceres - One of the best experts on this subject based on the ideXlab platform.
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modeling the sorption kinetic of metsulfuron methyl on Andisols and ultisols volcanic ash derived soils kinetics parameters and solute transport mechanisms
Journal of Hazardous Materials, 2010Co-Authors: Lizethly Caceres, Edwar Fuentes, Mauricio Escudey, María E. BáezAbstract:Metsulfuron-methyl sorption kinetic was studied in Andisol and Ultisol soils in view of their distinctive physical and chemical properties: acidic pH and variable surface charge. Different kinetic models were applied to the experimental results. The pseudo-second-order model fitted sorption kinetics data better than the pseudo-first-order model. The rate constant and the initial rate constant values obtained through this model demonstrated the different behavior of metsulfuron-methyl in both kinds of soils, both parameters being the highest for Andisol. The application of Elovich equation, intraparticle diffusion model and a two-site nonequilibrium model (TSNE) allowed to conclude that: (i) the high organic matter content is the governing factor for Andisols where mass transfer across the boundary layer, and in a lesser degree, intraparticle diffusion were the two processes controlling sorption kinetic and (ii) the mineral composition was more relevant in Ultisols where rate was controlled almost exclusively by intraparticle diffusion into macropores and micropores. The slower sorption rate on Ultisols, the mechanism involved and the lower sorption capacity of this kind of soils must be taken into account to assess leaching behavior of this herbicide.
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metsulfuron methyl sorption desorption behavior on volcanic ash derived soils effect of phosphate and ph
Journal of Agricultural and Food Chemistry, 2010Co-Authors: Lizethly Caceres, Edwar Fuentes, Mauricio Escudey, Roxana Fuentes, María E. BáezAbstract:Metsulfuron-methyl sorption/desorption behavior was studied through batch sorption experiments in three typical volcanic ash-derived soils belonging to Andisol and Ultisol orders. Their distinctive physical and chemical properties are acidic pH and variable surface charge. Organic matter content and mineral composition affected in different ways sorption of metsulfuron-methyl (KOC ranging from 113 to 646 mL g -1 ): organic matter and iron and aluminum oxides mainly through hydrophilic rather than hydrophobic interactions in Andisols, and Kaolinite group minerals, as major constituents of Ultisols, and iron and aluminum oxides only through hydrophilic interactions. The Freundlich model described metsulfuron-methyl behavior in all cases (R 2 > 0.992). Kf values (3.1-14.4 μg 1-1/n mL 1/n g -1 ) were higher than those reported for different class of soils including some with variable charge. Hysteresis was more significant in Ultisols. A strong influence of pH and phosphate was established for both kinds of soil, intensive soil fertilization and liming being the most probable scenario for leaching of metsulfuron-methyl, particularly in Ultisols.
Milko A. Jorquera - One of the best experts on this subject based on the ideXlab platform.
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putative nitrogen fixing bacteria associated with the rhizosphere and root endosphere of wheat plants grown in an andisol from southern chile
Frontiers in Microbiology, 2018Co-Authors: Joaquin I. Rilling, Jacquelinne J. Acuña, Michael J. Sadowsky, Milko A. JorqueraAbstract:Acidic ash derived volcanic soils (Andisols) support 50% of cereal production in Chile. Nitrogen (N) is essential for cereal crops and commonly added as urea with consequent environmental concerns due to leaching. Despite the relevance of N to plant growth, few studies have focused on understanding the application, management and ecological role of N2-fixing bacterial populations as tool for improve the N nutrition of cereal crops in Chile. It is known that N2-fixing bacteria commonly inhabits diverse plant compartments (e.g., rhizosphere and root endosphere) where they can supply N for plant growth. Here, we used culture-independent and dependent approaches to characterize and compare the putative N2-fixing bacteria associated with the rhizosphere and root endosphere of wheat plants grown in an Andisol from southern Chile. Our results showed significantly greater bacterial loads in the rhizosphere than the root endosphere. Quantitative PCR results indicated that the copy number of the 16S rRNA gene ranged from 10^12~10^13 and 10^7~10^8 g-1 sample in rhizosphere and root endosphere, respectively. The nifH gene copy number ranged from 10^5~10^6 and 10^5 g-1 sample in rhizosphere and root endosphere, respectively. The total culturable bacteria number ranged from 10^9~10^10 and 10^7~10^8 CFU g-1 sample in rhizosphere and 10^4~10^5 and 10^4 CFU g-1 sample in root endosphere using LB and NM-1 media, respectively. Indirect counts of putative N2-fixing bacteria were 10^3 and 10^2~10^3 CFU g-1 sample in rhizosphere and root endosphere using NFb medium, respectively. Sequencing of 16S rRNA genes from randomly selected putative N2-fixing bacteria revealed the presence of members of Proteobacteria (Bosea and Roseomonas), Actinobacteria (Georgenia, Mycobacterium, Microbacterium, Leifsonia and Arthrobacter), Bacteroidetes (Chitinophaga) and Firmicutes (Bacillus and Psychrobacillus) taxa. Differences in 16S rRNA and putative nifH-containing bacterial communities between rhizosphere and root endosphere were shown by denaturing gradient gel electrophoresis (DGGE). This study shows a compartmentalization between rhizosphere and root endosphere for both the abundance and diversity of total (16S rRNA) and putative N2-fixing bacterial communities on wheat plants grown in Chilean Andisols. This information can be relevant for the design and application of agronomic strategies to enhance sustainable N-utilization in cereal crops in Chile.
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Data_Sheet_1_Putative Nitrogen-Fixing Bacteria Associated With the Rhizosphere and Root Endosphere of Wheat Plants Grown in an Andisol From Southern Chile.docx
2018Co-Authors: Joaquin I. Rilling, Jacquelinne J. Acuña, Michael J. Sadowsky, Milko A. JorqueraAbstract:Acidic ash derived volcanic soils (Andisols) support 50% of cereal production in Chile. Nitrogen (N) is essential for cereal crops and commonly added as urea with consequent environmental concerns due to leaching. Despite the relevance of N to plant growth, few studies have focused on understanding the application, management and ecological role of N2-fixing bacterial populations as tool for improve the N nutrition of cereal crops in Chile. It is known that N2-fixing bacteria commonly inhabits diverse plant compartments (e.g., rhizosphere and root endosphere) where they can supply N for plant growth. Here, we used culture-independent and dependent approaches to characterize and compare the putative N2-fixing bacteria associated with the rhizosphere and root endosphere of wheat plants grown in an Andisol from southern Chile. Our results showed significantly greater bacterial loads in the rhizosphere than the root endosphere. Quantitative PCR results indicated that the copy number of the 16S rRNA gene ranged from 1012~1013 and 107~108 g−1 sample in rhizosphere and root endosphere, respectively. The nifH gene copy number ranged from 105~106 and 105 g−1 sample in rhizosphere and root endosphere, respectively. The total culturable bacteria number ranged from 109~1010 and 107~108 CFU g−1 sample in rhizosphere and 104~105 and 104 CFU g−1 sample in root endosphere using LB and NM-1 media, respectively. Indirect counts of putative N2-fixing bacteria were 103 and 102~103 CFU g−1 sample in rhizosphere and root endosphere using NFb medium, respectively. Sequencing of 16S rRNA genes from randomly selected putative N2-fixing bacteria revealed the presence of members of Proteobacteria (Bosea and Roseomonas), Actinobacteria (Georgenia, Mycobacterium, Microbacterium, Leifsonia, and Arthrobacter), Bacteroidetes (Chitinophaga) and Firmicutes (Bacillus and Psychrobacillus) taxa. Differences in 16S rRNA and putative nifH-containing bacterial communities between rhizosphere and root endosphere were shown by denaturing gradient gel electrophoresis (DGGE). This study shows a compartmentalization between rhizosphere and root endosphere for both the abundance and diversity of total (16S rRNA) and putative N2-fixing bacterial communities on wheat plants grown in Chilean Andisols. This information can be relevant for the design and application of agronomic strategies to enhance sustainable N-utilization in cereal crops in Chile.
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Aluminum-tolerant bacteria improve the plant growth and phosphorus content in ryegrass grown in a volcanic soil amended with cattle dung manure
Applied Soil Ecology, 2017Co-Authors: Maria De La Luz Mora, Rolando Demanet, Milko A. Jorquera, Jacquelinne J. Acuña, Sharon Viscardi, Zed Rengel, Paola DuranAbstract:Abstract In Chilean volcanic soil, crop production often is limited by a combination of the low available P and high concentration of toxic aluminum (Al). In this study we aimed to isolate Al-tolerant plant-growth-promoting bacteria from the rhizosphere and the endosphere of ryegrass grown in acidic Chilean volcanic soil in order to characterize a bacterial consortium capable of contributing to alleviation of Al 3+ toxicity and supporting plant growth in Andisol. Five strains, i.e. Klebsiella sp. RC3, Stenotrophomonas sp. RC5, Klebsiell a sp. RCJ4, Serratia sp. RCJ6 and Enterobacter sp. RJAL6, were selected based on their capacity to tolerate high Al concentration (10 mM) and to exhibit multiple plant-growth-promoting traits (P solubilization, indole acetic acid production, 1-aminocyclopropane-1-carboxylate deaminase activity, and exudation of organic acid anions and siderophores). Based on the results, we can suggest that selected bacteria could alleviate Al stress by forming Al 3+ -siderophore complexes. The plant-growth-promoting potential of the bacterial consortium was confirmed in an assay with ryegrass plants. In the treatment with cattle dung manure, the consortium promoted plant growth and the phosphatase activity in the rhizosphere soil. Increased phosphatase activity coincided with elevated P concentration in shoots. Our results suggest that a combination of native Al-tolerant bacteria and cattle dung manure is effective in decreasing Al toxicity and promoting plant growth in Andisols of southern Chile.