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Revista de la ciencia del suelo y nutrición vegetal

versión On-line ISSN 0718-2791

R.C. Suelo Nutr. Veg. v.8 n.especial Temuco  2008

http://dx.doi.org/10.4067/S0718-27912008000400021 

 

J. Soil Sci. Plant Nutr. v8 no especial 2008 (146-175)

POSTER ABSTRACTS 

                                       

Session 1. Ecological Significance of Interactions Among Clay Minerals, Organic Matter and Biota

Use of Natural Nanoclays as Support Material for Manganese Peroxidase Immobilization

 

F. Acevedo1*. M. Cea2, S. Sanhueza3, M. Calabi1 and M.C. Diez4

1Programa de Doctorado en Ciencias de Recursos Naturales, Universidad de La Frontera, Temuco. laboratorio de Suelos, Instituto de Agroindustria, Universidad de la Frontera, Temuco.3Carrera de Ingeniería Ambiental, Facultad de Ingeniería, Ciencias y Administración, Universidad de La Frontera, Temuco. 4Departamento de Ingeniería Química, Facultad de Ingeniería, Ciencias y Administración, Universidad de La Frontera, Temuco. *E-mail: facevedo@ufro.cl

Keywords: Nanoclays; enzyme immobilization; manganese peroxidase

Various applications of extracellular enzymes from white-rot fungi as biocatalysts have been reported in pulp bleaching, wastewater treatment and soil remediation. However, their use in industrial applications has been limited by several factors, mainly the high enzyme cost, the low operational stability and the low or no recovery options. The enzyme immobilization has demonstrated to be a good technology that may allow their practical application. Fungal enzymes have been successfully immobilized on porous glass beads and on various clay minerals for soil pollutants degradation. Nanomaterials of natural origin, such as nanoclays, have not been proved yet. The aim of this study was to obtain nanoclays as support material for the immobilization of manganese peroxidase (MnP) from the white rot fungus Anthracophyllum discolor. Andisol of the South of Chile, from the Temuco Series, was used for nanoclays obtention. The clay fraction was obtained by a sedimentation method based on Stokes's law, without destruction of the organic matter. 5 g clay was suspended in 100 mL NaCl 1 M, with agitation for 48 h. The suspension was centrifuged at 3,000 rpm for 40 min and the supernatant was discarded. Clay was re-suspended in 50 mL of filtered and deionized water, under moderate agitation for approximately 1 h, and then centrifuged under the same previous conditions. The procedure was repeated 7 times. The recovered supernatants were dialyzed until a conductivity range between 0.5 to 0.8 µS, and than concentrated. For its characterization, nanoclays were analyzed by transmission electronic microscopy and its isoelectric point was determined by microelectrophoresis. Electrophoretic mobilities were measured with a zeta meter (ZM-77) apparatus. Dilute dispersions (0.05 g/liter) were prepared in 10-3 M KC1. The pH was adjusted with 10-2 M HC1 or NaOH. The mobilities were averaged and the zeta potential calculated using the Helmholtz-Smoluchowski equation. The results indicate that the obtained material corresponds to nanoclays with a particle average size less than 100 nm, without the presence of electronic diffraction and with an isoelectric point (pi = 3.2 ) closed to that of clay. Future studies will be focused on the evaluation of the immobilization efficiency of MnP from A. discolor in this new natural nanomaterial.

Acknowledgments: This work has been financed partially by FONDECYT N° 1050614 project and PhD. scholarship from CONICYT, Chile.

Adsorption of Added Cadmium in Relation to Properties of Some Alluvial Soils

LA. Al-Hawas*

Department of Environmental and Natural Resources, College of Agriculture and Food Science KFU, Saudi Arabia. *E-mail: ihawas@kfu.edu.sa

Keywords: Adsorption modeling; Cadmium; Clay.

In the present work an attempts have been done to study the adsorption capacity of Malaysian soils for cadmium, which consider as an environmental harmful metal. Six soils represent the major soil series used for agricultural production in Malysia: Typic Sulfaquept (Sedu) Haplic Acrorthox (Segamat) Tropic Fluvaquent (Kundor), Orthoic Tropudult (Durian), Typic Paleudults (Melangit), and Typic Paleudults (Betu Anam) were used. The soils were very acid to slightly alkaline with the lowest pH value at 3.0 (Sedu) and the highest pH 7.3 at Melangit soil. The soils texture varied from silty to clayey. The highest clay content (87%) was found in Segamat series where the lowest was in Melangit which considered silty soil. The amount of Cd adsorbed by soil depends on their physico-chemical properties. The adsorption data were tested by three different models Langmuir, Freundlich and second order equation. For the Langmuir isotherm r2 ranged between 0.943 to 0.998 with an average of 0.979, Freundlich isotherm r2 ranged between 0.519 to 0.991 with an average value of 0.866 where the second degree (r2) ranged between 0.366 to 0.997 with an average 0.900. This suggests that the Langmuir isotherm provides a good model of the sorption system. The adsorption capacity differs between soils. The highest adsorption capacity was found in Melangit and Kundure ranged between 1800to 2500 ug soil-1 Cd. Though Melangit is silty soil but it has high pH and high content of Calcite this suggesting the precipitation of Cd and the sorption of heavy metals may be on the edge due to the aluminol sites. The usage of added CdCl2 as adsorbant metal, CdCl+tends to be desorbed from the clay to a larger extent than Cd and hence adsorbed as a monovalent than a divalent cation.

Comparing Two Selective Chemical Treatments to Selectively Extract Iron from the Organic Matter of Volcanic Soil Samples

S. Aravena1, C. Morales1, C. Pizarro1 and J.D. Fabris2

1Facultad de Química y Biología, Universidad de Santiago de Chile, Av. L. Bernardo O 'Higgins 3363, Estación Central, Casilla 40-Correo 33, Santiago, Chile. 2Departamento de Química - ICEx, UFMG, Pampulha, 31270-901, Belo Horizonte, MG, Brazil. *E-mail:susana.aq@gmail.com

Keywords: Chilean soils; pyrophosphate treatment; citrate treatment.

The chemical evaluation of the total amount and of the mineralogical distribution of iron in both soil-aluminosilicates and -organic matter (OM) fractions has been receiving special attention, in recent times. The main interests are centered on establishing differentiation criteria in soil grouping, regulating micro- and macro-nutrients dynamics in the soil-water interface and developing technological approaches to remediate contaminated areas. Chemical extraction treatments would be a more direct and practical laboratory alternative to selectively separate iron from minerals and iron-OM from soils. In this work, two selective chemical treatments for iron extraction from Fe-OM systems, namely 0.1 mol L-1 sodium pyrophosphate and 0.2 mol L-1 citrate solutions, were assayed with the clay fraction (particle diameter, < 2 urn) and the bulk soil (sieved to 2 mm) samples from two volcanic soils from Chile: a Ultisol (sample labeled according to the locality's name, Collipulli, geographical coordinates of the sample sites are 36°58'S 72°09'W) and two Andisols (Digullin, 36°53'S 72°10'W; and Freiré 38°57'S 72°36'W), in an attempt to compare the iron extractive ability of these methods. From chemical analyses, the clay and bulk Ultisol samples presented, as expected, higher iron content and lower OM amount than those from Andisols. The removal effectiveness of each of these two chemical treatments was found to behave differently. The iron extractive capacity was higher with citrate than with pyrophosphate for these clay fractions, whereas for bulk soils, the pyrophosphate treatment extracted iron more efficiently than citrate.

Acknowledgments: Work supported by DICYT-USACH (Chile, graduate scholarship), MIDEPLAN (Chile, grant Presidente de la República), CNPq and FAPEMIG (Brazil).

 

Use of Compost and Azospirillum lipoferum to Alleviate Saline Stress in Capsicum annuum Grown in Saline Soil

M. Bacilio-Jiménez* and P. Castillon-Baturoni

Centro de Investigaciones Biológicas del Noroeste (CIBNOR), La Paz, B. C.S., México.

*E-mail: mbaciüo 04@cibnor. mx

Keywords: Compost; Azospirillum lipoferum; alleviate saline stress.

One-third of all irrigated land is believed to be affected by the salt content, which is very common in arid and semi-arid regions. Salinity can cause a decrease in water uptake in plants, which reach toxic levels and reduce availability of nutrient and finally the growth of the plants is reduced. Soil amendments have been employed to ameliorate the adverse effects of salts, including plant-growth regulators, nitrogenous compounds, gypsum, and sugars. Recently, the use of microorganisms, compost, and humic acids have been shown to be more effective than gypsum, which is currently the standard amendment used to reclaim alkaline soils and reduce the effect of salt on seed germination and growth. Here we report on the degree of mitigation of salt stress in chili plants (Capsicum annuum), using compost and A. lipoferum as a soil amendment. We used chili seeds of the variety 'Ancho San Luis' germinated on peat moss. One month later, the seedlings were transplanted to pots containing saline soil (electrical conductivity 15 dS m-1 EC) or the control (EC = 1 dS m-1). Compost was mixed into the soil as an amendment agent at doses of 0%, 10%, and 20% (v/v). Some treatments involved plants inoculated with A. lipoferum (1x108 UFC plant-1) at the time of transplantation. Plants maintained under temperature and irrigation controls and harvested 3 months after the beginning of the treatments. Measurements of plants included height of plant, dry weight of the shoot and leaf, foliar area, and number of leaves. Chlorophyll content significantly increased a compost content of 10%, compared with controls (no compost). A synergic effect of compost with A. lipoferum increased root and leaf dry weight.

 

Azospirillum lipoferum and Humic Acids Induce Decrease of Salt Stress in Chili Plantlets (Capsicum annuum)

M. Bacilio-Jiménez* and D. Covarrubias-Robledo

Centro de Investigaciones Biológicas del Noroeste (CIBNOR), La Paz, B. C.S., México.

*E-mail: mbaciüo 04@cibnor. mx

Keywords: Azospirillum lipoferum; humid acids; salt stress.

To reclaim alkaline soils and reduce the effect of salt on seed germination and growth, several methods are currently used, including gypsum, compost and humic acids, and inoculation with A. brasilense. Simultaneous use of microorganisms and humic acid to alleviate saline stress represents another interesting possibility. Our objective was to evaluate the capacity of humic acids and Azospirillum lipoferum a plant growth-promoting bacteria together and separately for mitigating saline stress on plantlets of Capsicum annuum for 21 days after sprouting, under different levels of NaCl. Under in vitro conditions, seeds were germinated and cultivated under 0, 25, 50, and 75 mM NaCl for 21 days in an environmental chamber under axenic conditions. The treatments were: (1) Humic acid at a concentration of 1000 ppm; (2) A. lipoferum at a concentration of 106 UFC mL_1; and (3) humic acid and A. lipoferum at the same concentrations. To evaluate mitigation, we measured length of root and shoot, number of secondary roots, root and shoot dry weight, root hair length, and production of root mucigel. The results indicate a synergic effect between HA and A. lipoferum on primary root, root hairs length, and secondary roots number, especially in high levels of salt where, for example, a 75 mM NaCl the root hair were from 35 to 150% longer than the other treatments. The humic acid treatment provided the best results by increasing dry weight of shoots and roots at practically all levels of NaCl, 10% better than the A. lipoferum treatment or the A lipoferum-humic acid treatment. Higher production of mucigel, (two times more) was observed at 25 and 50 mM NaCl and was stimulated by A. lipoferum, but at 75 mM, mucigel production was stimulated by humic acid with amounts four times more than with the bacteria. These results suggest that a synergic effect between humic acid and A. lipoferum exists for mitigating saline stress in chili plants. However, in some cases, the mitigation is induced by humic acid or A. lipoferum independently, depending on the salt concentration and the target organ of the measured parameter.

Mulching for a Healthy Landscape

N. Bassirani*

Department of soil science Zabol University, Zabol, I.R. Iran. *E-mail: N_Bassirani@yahoo.com

Keywords: Mulching; healthy landscape; Iran.

A result of the geographical and ecological situation of Iran, as well as the blowing of unfavorable winds in the Central Desert, more than 80% of the 164 million hectare area of the country is subject to the conditions of arid and semi arid regions, characterized by low precipitation, ranged between 50 to 250 mm per year. At the present the area of the country's deserts and sandy soils is estimated to be 34 million hectares, and that of the poor and desertified rangelands which 12 million hectares correspond to the sandy, soils 5 million of the same shifting sand dunes. For as long as trees have grown in forests, leaves and needles have fallen to the ground and formed a natural protective layer over the soil. This same protection can be given to the plants in our landscapes by mulching. Mulching can make a big difference in the success of your landscape. Mulches conserve soil moisture, allowing you to water less often; keep down weeds; reduce erosion; keep plant roots cool; provide winter protection; and make your yard more attractive. Mulches also simplify lawn mowing around trees and shrubs. A ring of mulch allows you to bring your lawn mower right up to the edge of the mulch, eliminating the need for string weeders. At the same time you are protecting tree trunks and surface roots from damage by mowing and clipping equipment.

Role of Planted Trees and Forest Plantations in Low Forest Cover Countries (LFCC) - Case Study of Iran

N. Bassirani*

Department of 'soil science Zabol University, Zabol, I.R. Iran. *E-mail : N_Bassirani@yahoo.com

Keywords: Planted trees; forest plantations; low forest cover

The decrease of woodland and tree vegetation in and around rural and human settlements in Low Forest Cover Countries (LFCC) has raised concerns among the countries concerned and the international community. The loss of these resources impacts directly on the poor communities, which rely on trees and wooded formations to maintain their quality of life. To confront this situation, the planting of trees will become more and more frequent in order to create more wooded areas. To make these plantations sustainable, careful consideration must be given to their position in the overall land use patterns, and this paper draws attention to the role of trees planted both within and outside the areas formally classified as forest. Low forest cover raises various issues for which plantations, tree growing and the encouragement of regeneration have been identified as vital activities in order to: Replace the loss of natural forest and planted forest cover (reforestation); Introduce forest to sites that have never supported forest, or have not had non forest cover for a long period (afforestation); Improve degraded natural forest ecosystems; Expand tree cover on non-forest areas, rehabilitate degraded lands, restore soil fertility and control soil erosion; Provide services and goods that natural forests may no longer be able to meet, including the provision of fiielwood, fodder and non-wood forest products; Provide industrial wood and fiielwood; Ease human and animal pressure on limited natural forest areas; Improve the land and natural resource base, including water conservation, and Contribute to global ecological benefits such as the conservation of biological diversity and carbon sequestration.

 

Gypsum and Organic Matter Application in Salinity Field Trial Play a Major Role on Detoxification of Salt-Stressed Jasmine Rice (Oryza sativa L. spp. indica)

S. Cha-um1*, Y. Pokasombat2 and C. Kirdmanee1

1 Plant Physiology and Biochemistry Lab, BIOTEC Central Research Unit, National Center for Genetic Engineering and Biotechnology, Thailand Science Park, Pathumthani 12120, Thailand. 2Pimai Salt Company Limited, Pimai, Nakhon Rajchasema 30110, Thailand. *E-mail: suriyanc@biotec.or.th

Keywords. Gypsum; organic matter; salt stress.

Jasmine rice, high cooking qualities as aromatic flavor, softening and long grain, has been reported as salt susceptible. The best quality of jasmine rice is generally cultivated in the northeastern region of Thailand, which is defined as inland salinity area. The salt contamination in the soil is one of the most barriers to reduce on growth and development of rice crop, especially in the seedling and reproductive stages, leading to low productivity. Soil physical and chemical improvements in the salinity area are alternative channels to enhance on detoxification of salt contaminant using exogenous calcium (gypsum) and organic matter (OM). In this study, rice grown in the exogenous application of gypsum and/or OM was 90% seed set, while rice grown in the soil without gypsum and/or OM treatment found seedless or lack of productivity. Sodium ion accumulation in both root and shoot organs of jasmine rice cultivated in the soil with exogenous gypsum and/or OM treatments was lower than those rice grown in the soil without gypsum and/or OM, while the potassium ion was enriched. In addition to, the low salt accumulation in exogenous gypsum and/or OM treated rice was positively related to pigment stabilization, photosystem II (PSII) function, and net-photosynthetic rate, resulting in high sugar content in the flag leaf with high yield. It should be concluded that the exogenous gypsum and/or OM in salinity field may be played as effective procedure to detoxify the damage from salts in salinity soil.

Contribution of Glomalin to Soil Organic Carbon in a Mediterranean Agroecosystem Managed under Two Tillage Systems

G. Curaqueo1*, E. Acevedo2, J. Garcia3, G. Borie3, R. Rubio4, A. Morales4 and F. Borie4

1Programa de Doctorado en Ciencias de Recursos Naturales, Universidad de La Frontera, Casilla 54-D. Temuco, Chile. 2Facultad de Ciencias Agronómicas, Universidad de Chile, Casilla 1004, Santiago,Chile. 3Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Casilla 203, Santiago,Chile. "Departamento de Ciencias Químicas, Universidad de La Frontera, Casilla 54-D, Temuco,Chile.

*E-mail: gcura@ufro.cl

Keywords: Glomalin; soil organic carbon; tillage systems

The glomalin or GRSP (glomalin related soil protein) is a glycoprotein produced by arbuscular mycorrhizal fungi (AMF), presenting a high recalcitrance to microbial and enzymatic breakdown, and consequently is accumulated in the soil profile. GRSP might contribute to increase the soil organic carbon (SOC) and therefore the carbon sequestered into the soil due to its structural C content and the promotion of soil aggregation. Tillage systems affect all soil properties and obviously the microbiological characteristics, including glomalin content and stability, influencing the C storage in the agroecosystems. We evaluated the influence of two tillage systems applied to a soil from Central Chile on its chemical, physical, and mycorrhizal properties including glomalin levels. Characteristics measured were: Total glomalin (GRSP), soil organic matter fractions (fiilvic acid, humic acid and humin), C content, AMF spores number, NAGase activity (enzyme related with the biomass fungi), bulk density, and aggregate water stability at the upper horizon (0-5 cm). All these properties were evaluated in an experimental agroecosystem managed for 6 years by conventional tillage (CT), and no tillage (NT) in a wheat-corn rotation in a Mollisol (Entic Haploxerolls) in Central Chile. Additionally, we made a decomposition assay to measure glomalin recalcitrance, incubating soil samples during 250 days at 20°C and determining the level of GRSP every 50 days. Mean values in the 5 cm soil profile for GRSP were CT=3.96 and NT=8.16 mg g-1. Soil organic matter fractions show 96.4% of humin, 0.5% of humic acid and 0.4% of fiilvic acid in NT system, and 95.5% of humin, 0.6% of humic acid and 0.5% of fiilvic acid in CT system. C content were CT=1.7% and NT=2.6%, where the glomalin-C represented 6.9% and 9.9% of total C for CT and NT, respectively. The AMF spore numbers were lower in soils under CT than NT system. NAGase enzymatic activity was high in NT in relation to CT. Soil bulk density was 0.884 g cm-3 in NT compared with 1.005 g cm-3 in CT. The aggregate water stability was higher in NT, with 59% in contrast to CT with 32% of aggregation. Glomalin decomposition assay shows that the glomalin levels decreased from TO to T150 and increased from T150 to T250. Results showed that the NT systems exert a positive effect on all the characteristics measured in relation to CT. Another aspect to highlight is the important role of AMF and specifically the glomalin in the C sequestration in the soil of the Mediterranean Agroecosystem studied.

 

Kinetic Changes in Phosphorus Fractions during Aerobic Degradation of Dairy Dung

B. Fuentes1,2*. A.A. Jara3 and M.L. Mora3

1Programa de Doctorado en Ciencias de Recursos Naturales, Universidad de La Frontera, Temuco, Chile. 2Departamento de Ingeniería Química, Universidad Católica del Norte, Antofagasta, Chile. 3Departamento de Ciencias Químicas, Universidad da la Frontera, Temuco, Chile. *E- mail: bfuentes@ucn.cl

Keywords: Phosphorus fractions; aerobic degradation; dairy dung.

Phosphorus (P) fractions in organic waste are modified during the aerobic degradation process. In this study, the changes in distribution of inorganic P (Pi) and organic P (Po) fractions were evaluated during the aerobic degradation of dairy cattle feces in laboratory-scale reactors for 105 d. Sequential fractionation procedure of Hedley was used. The kinetics data was described by power function. The fractionation procedure showed that P-residual fraction was strongly increased in time. Also, Pi fractions were gently increased. Thus, initial rate coefficients showed that Pi-H20 and Pi-NaHC03 (around 6.6 mg P kg-1 d) were higher than Pi-HCl (5.3 mg P kg-1 d-1) and Pi-NaOH (4.2 mg P kg-1 d-1). Therefore available P was provided mainly by Pi weakly linked to aluminum and iron surfaces. In contrast, initial P release rate showed that Po fractions were quickly decreased in the following order: Po- NaOH (12.2 mg P kg-1 d-1) > Po-H20 (9.9 mg P kg-1 d-1) > Po-HCl (8.3 mg P kg-1 d-1) Po-HC03 (6.9 mg P kg-1 d-1). P-residual fraction was increased through all the process of degradation, whereas Po fractions were decreased. This behavior was associated to strong interactions between organic macromolecules with aluminum, iron and calcium compounds. Therefore, useful tools focused to degradation of organic P compounds could contribute to increase P bioavailability in organic waste.

Acknowledgements: MECESUP FRO 0309 and CONICYT AT- 24060247 grants.

Effect of Green Rust Formation on the Phosphorus Adsorption and NitrogenMineralization in Flooded Soils Collected from the Lower Orinoco River, Venezuela

B. Garcia*. D. Benzo, J. Bastidas, R. Ochoa, S. Flores and N. Chacón

Centro de Ecología, Instituto Venezolano de Investigaciones Científicas, Apdo. 21.827 Caracas 1020-A, Venezuela. *E-mai¡: bgarcia@ivic.ve

Keywords: Green rust formation; phosphorus adsorption; nitrogen mineralization.

Water in soil restricts gas diffusion and limits the oxygen availability in soil with a consequent decrease in the soil redox potential. Under such circumstances, microbial dissolution of Fe (III) oxides can take place and the dynamics of the nutrients such as phosphorus (P) and nitrogen (N) can be affected. Under anaerobic soil condition biogenerated Fe(II) can experience secondary chemical reactions, which lead to the formation of aqueous complexes and/or the precipitation of ferrous solids as green rusts (GR) compounds [Fe11 (1-x)FexIII (OH)2]x+ [ (x/n)An-(m/n)H20]x-. In an earlier laboratory research with soil samples collected from a seasonal flooded forest in the lower Orinoco River, Chacón et al. (2005) hypothesized that anaerobic soil condition leads to the formation of the green rust compounds. In the field when the soils are exposed to the air, just at the end of the aquatic phase, we have detected dispersed spots of a blue-green color, which we have associated with precipitation of GR compounds. In this study we examined the N mineralization and adsorption P in samples collected from the GR spots and the adjacent soil as a control (C). Ten samples of both GR and C were taken at the end of the flood event in November 2006, following a completely random design. Nitrogen mineralization was carried out during eight weeks using an incubated method. Values of Nm (net nitrogen mineralization), No (potentially mineralizable nitrogen) and k were obtained following the Sanford and Smith (1972). Phosphorus adsorption was performed according to Waldbridge et al (1991). Theoretical adsorption maxima (b) were obtained fitting the data to the linear form of the Langmuir equation. The results showed that GR compounds were more active in the N mineralization, which leads to highest values of Nm and No. Ammonium-N predominates in both GR and C. The absence of nitrate forms was associated with the soil acidity. The P adsorption data were satisfactorily described by the Langmuir equation. Adsorption maxima value was lowest in the GR compounds. These minerals are active ion exchangers and sorbents of inorganic anions as C032- and S042- and organic acids. We hypothesized that the low b value obtained in the GR samples of this study could be obey to a strong competition among anions by the active adsorption sites of these compounds. Such low P adsorption capacity could be indicative of a greater P bioavailability in the soil influenced by the presence of these surfaces. The above results allowed us to suggest a number of hypotheses concerning the mechanism that regulate the P and N availability in anaerobic soils influencedby the GR formation. In this study we proposed that the GR precipitation in the flooded soils of the lower Orinoco river are hot spots for P and N bioavailability. It is further suggested that this provides a mechanism for essential nutrient release which could be subsequently rapidly utilized by plants and microorganisms.

References

J. Carbón and C. Schubert. (1994). Quaternary International 21: 91-100.

N. Chacon, S. Flores, A. González. (2005). Soil Biology & Biogeochemistry 38: 1494-1499.

L.H. Chaves. (2005). Revista Brasileira de Engenharia Agrícola e Ambiental 9: 284-288.

H.C.B. Hansen, C.B. Koch, H.N. Krogh, O.K Borggaard, J. Sorensen. (1996). Abiotic nitrate reduction to

ammonium: Key role of green rust. Environmental Science Technology, Washington, D.C. 30: 2034-2056.

M.R. Walbridge, C.J. Richardson and W.T. Swank. (1991). Biogeochemistry 13: 61-85.

 

 

Organic Installment and Humidity Levels in Fodder Nopal

J.A. Chavarria*. L. Garcia, M. Fortis, E. Salazar and P. Mexica

Technological Institute of Tower, Highway Tower-Saint Pedro km 7,5; Tower, Coahuila, México. *E-mail: chavarria_itt@hotmail. com

Keywords: Goat dung; chemical fertilizer; nopal

When incorporating dung to the ground is increased the biological activity, the physical properties and chemical of the ground and the availability of nutrients for the plants is increased (Castilian 1980). The objective was to obtain the optimal interaction of dose of goat dung, fertilizing chemistry and levels of volume of water and their answer in the production of nopal for forage of the variety fodder Alpha. The investigation carried out in the Experimental Agricultural Field of the Faculty of Agriculture and Zootechnics of the Juárez University of the State of Durango located in the kilometer the 30 of the highway Gómez Tlahualilo Palace, Durango. Mexico. The treatments of the organic installment and the chemical fertilizer that were applied in the three blocks are according to the design of blocks at random with adjustment in strips.

 

 

In analysis of the vegetative area and number of rackets the treatments of 40, 80 and 120 ton have-1 of goat dung excel of the chemical fertilizer and the witness. The oppuntia responded suitably to the application of goat dung with 120 ton has-1 and presents/displays the major yields and in number of rackets in comparison to the chemical fertilizer and the witness. The chemical properties of the ground (Ca, mg, Na, N03, pH and M.O.) presented/displayed major concentration in the goat dung treatments (80 and 120 ton has-1 ). These values exceed the permissible limits, reason why it will be due to have well-taken care of with the application continues (for year) of these doses, ton is better to initiate with 80 120 has-1 and later to diminish the dose according to a detailed ground analysis. The plant (rackets) in its quality analysis I present/display high levels of nutrients, where it excels the chemical fertilizer with 80-80-00, 40-160-00 and 120-160-00 kg ha-1 in comparison with those of goat dung. In analyzed the physical properties of the ground they presented/displayed an improvement to the application of goat dung. The treatment of 120 ton has-1 of goat dung was the one that I present/display major humidity retention in the ground in comparison to the one of chemical fertilizer and to the witness.

 

Management with Different Cover Crops and Phosphorus Fertilizers Affects Organic Matter Distribution in Savanna Soil Fractions

R.M. Hernández-Hernández1*. S. Sleutel2, S. De Neve2, D. Gabriels2 and Z. Lozano3

1Universidad Simón Rodríguez, IDECYT, Venezuela.2Faculty of BioScience Engineering, Ghent University, Belgium. 3 Universidad Central de Venezuela, Instituto de Edafología, Venezuela. * E-mail: rosa. hernandez@unesr. edu. ve.

Keywords: Cover crops; phosphorus fertilizers; soil organic matter.

The extension of the agriculture froontier in the savannas of Venezuelan Plains affects the functions of this ecosystem due to the perturbation of the physical and chemical protection mechanisms of soil organic matter (OM). Our objectives were to evaluate the effect of the cover crop-maize association managed with no tillage and different fertilizations on the organic matter fractions distribution in Savanna soils, as well as the stabilization mechanisms involved. The fertilization treatments applied to maize associated with Brachiaria dictyoneura (BDY) and Centrosema macrocarpum (CM), in a Savanna ecosystem localised in the Guárico State, Venezuela, were: IR: low level of inorganic fertilization using NPK compared with the average rates used by local farmers, RF: Phosphoric rock, IO: without fertilization. Total values of P, N, K applied were the same in all treatments, only the source of P was changed. Natural Savanna was used as a comparison control (NS). The experimental layout was big plots without repetition where a previous geoestatistic study of spatial variability was made. Six composed samples (0-5 cm) were taken in each plot (18 x 450 m). A soil fractionation was made using wet sieving (size) and density separation (sodium polytungstate d = 1.85 g cm-3). Free particulate OM no protected (OMf), free particulate OM between micro aggregates (OMfe), OM physically protected inside micro aggregates (OMi) and OM associated to clays and silts were obtained and total organic carbon was estimated in each fraction using a TOC auto analyzer. Grass cover (BDY) had more OMf and OMFe than NS and the legume cover CM (p < 0.05), while CM produced 10% more micro aggregates and OMi (p < 0.05), this cover crop promoted the microaggregation and the OM physical protection to similar levels than in the comparison untreated system (NS). Cover-fertilization interaction (BDY-RF) increased the OMf and OMfe (p < 0.05). A minor OM quantity associated clay and silt was found in the BD-IR treatment, decreasing the OM chemical stabilization of savanna soil. The combination of soluble fertilizers with easily decomposable organic material showed by BDY (Padrino and Hernández-Hernández, 2004) decreased the OM chemical stabilization favouring the OMf production, which don't contribute to the soil stabilization, while the use of more recalcitrant organic material produced by the legume (CM) raised the OM physical stabilization.

References

M. Padrino and R.M. Hernández-Hernández. (2004). Dinámica de la descomposición de raíces de coberturas perennes en suelos de sabanas bien drenadas. Trabajo en extenso Proceeding XVI Congreso Latinoamericano de la Ciencia del suelo, Cartagena de Indias, Colombia.

Soil Microbial Protein-Clay Complexes

B.P. Kelleher* and A. Spence

School of Chemical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland. * E-mail: brian.kelleher@dcu.ie

Keywords: soil microbes; soil microbial proteins; clay minerals.

Bacterial enumeration in soil environments estimates that the population may reach approximately 1010 g-1 of soil and comprise up to 90% of the total soil microbial biomass. Bacteria are present as single cells or multicell colonies and often strongly adsorb onto mineral surfaces such as sand, clay, or clay-organic matter complexes. The interactions of microbes and microbial biomolecules with these minerals have profound impacts on the physical, chemical and biological properties of soils. In this work, microbes were propagated form a light clay-loam soil sampled from Teagasc, Carlow, Ireland, and the number of colony forming units (CFU) determined. Soluble microbial proteins (116 to 6.5 kDa) were isolated and the concentration of proteins evaluated using the Bradford Dye protein determination reagent. Quantified microbes and microbial proteins were sorbed to montmorillonite (M) and kaolinite (K) clay minerals and the equilibrium adsorption of microbes and microbial proteins determined as previously indicated. M showed a greater affinity for soil microbes and soil microbial proteins. To determine where soil microbes and soil microbial proteins are adsorbed on clay minerals and the nature of the interaction, complexes were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Fourier-transform infrared (FT-IR) spectroscopy. XRD showed that microbes and microbial proteins intercalated the interlamellar region of M resulting in M-microbial and M-protein intercalation complexes with a 001 d-spacing of 1.5 and 1.6 nm, respectively. XRD also confirmed that microbes and proteins did not penetrate K, indicating that adsorption occurred primarily on the external surfaces, as also suggested by SEM observation. SEM observations also indicated microbial and protein adsorption to the surfaces of the M. FT-IR spectra were indicative of M-microbes and -protein, and K-microbial and -protein complexes. The implications of these interactions on the total contribution of proteins and other microbial constituents to soils are currently being considered using novel NMR approaches. We also intend to look at degradation patterns and possible protection mechanisms afforded by clay complexes.

 

Introduction about Microbial Biomass in Soil

H. Kheyrodin*

Department of Soil Science and Agri-Food Engineering Laval University, Quebec, Canada, G1K 7P4. *E-mail: Hkhyrodin@yahoo.com

Keywords: microbial biomass; soil microbes; soil quality.

Biomass, defined as all land and water based vegetation as well as all organic wastes, fulfilled almost all of humankind's energy needs prior to the industrial revolution. Soil microbes play an important in role in how well the soil functions as a medium for plant growth and as an environmental buffer for clean water and air. Microbes increase soil quality by mineralization of nutrients for plants, processing residues into organic matter, increasing soil structure and degrading toxic compounds. The measurement of these microbes and their processes give us information as to how the soil in a particular ecosystem is functioning. The microbial biomass C, N, P, S are an important source for nutrient elements for the plants.

 

Contribution of Humic Substances from Different Composts on the Content ofHumin in a Tropical Soil

C.C. Lima1*. E.S. Mendoza2,1.R. Silva2, L.H.M. Silva3, B.H. Peres2 and A. Roig4

1Escola Agrotécnica Federal de Satuba, Satuba, AL, Brazil.2 Departamento de Solos/UFV, Vicosa, MG, Brazi. 3Departamento de Química/UFV, Vicosa, MG, Brazil; 4CEBAS-CSIC, Campus Universitario de Espinardo, Apartado de Correos 164, 30100 Espinardo, Murcia, Spain. *E-mail:claudivanc@yahoo.es

Keywords: Humic substances; compost; tropical soil.

The mineralogical nature of the soil, as well as the quantitative and qualitative characteristics of humic and fulvic acids present in the composts may affect both the reactivity and the stability of humic substances (HS). Due to their recalcitrant structures and their interaction with the soil mineral matrix or occluded intra-aggregates, the hydrophobic HS become more resistant to microbial degradation, they persist longer time in the soil. The alkyl groups of hydrophobic character in this humic acid fraction of composts can role the incorporation of this humic fraction to the humin fraction of the soil. To evaluate this proposition it was added increasing doses (0, 13, 26, 52 e 104 Mg ha-1) of five different composts in an Oxissol soil. The following wastes were used to obtain five composts: sweet cane bagasse (SCB), ashes of sweet cane bagasse (ASCB), poultry manure (PM), filter cake (FC) and castor oil plant residue (MR). The mixtures were as follows: a) SC: SCB+ASCB+PM (3:3:2); b) AS: SCB+ASCB+PM+ mineral fertilizers NPK (3:3:2); c) SM: SCB+ASCB+PM + serpentinite and micaxist powdered rocks (3:3:2 + 62.5 kg t-1); d) FC: SCB+FC (2:1); and e) MR: SCB+MR (2:1). These composts were characterized chemically by 13C NMR, and estimated the quantity of functional alkyl groups of humic acids applied to the soil as composts. Thirty days after application of the treatments, soil samples were collected, and the organic matter fractionation in humic acids (HA), fulvic acids (FA) and humin (HU) were analyzed, and it was calculated the HA/FA and (HA + FA)/HU ratios. There was predominance of FA in relation to the HA after application of increasing doses of different composts to the soil, although they had higher levels of HA than FA; the application of the compost M-G contributed to obtain higher levels of HU in the soil; the incorporation of organic components to the fraction HU was governed by the content of alkyl groups of HA fraction of the composts.

Modification Forms of P in Soils Affected by Ash from Forest Fires

P. De La Fuente. K. Manquián*, N. Arancibia, J.E. Forster and M. Escudey

Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile. *E-mail: hnanquian@ufro.cl

Keywords: Phosphorus; ash; forest fires.

In this work the impact in depth of ashes from native forest (NA), and pines (PA) and eucalyptus (EA) plantations on P forms in soils was studied. Ralun (Andisol) and Collipulli (Ultisol) soils were considered. Leaching columns to simulate the ash impact were used. Soils were packed into 10 cm of diameter columns to the depth of 25 cm according to their respective field bulk densities. Sixty grams of ash were incorporated into the surface 5 cm of the packed columns. The columns were irrigated weekly with one pore volume of distilled water and gravity drained, for a period of 12 weeks. At the end of the leaching experiment, each soil column was cut open lengthwise and the profile was sectioned into five equal length segments. Each section was characterized for pH, organic carbon (OC), electrical conductivity (EC), and available P. Fractionation was used to estimate P chemical forms. Phosphate determination was carried out by the formation of phosphomolybdic acid, reduced to intensely colored molybdenum blue by ascorbic acid. In general, ash application results in higher values of pH, EC and available P in the first 0-5 cm section, and lower values of OC in the 0-5 and 5-10 cm sections, when compared with the corresponding control column section. No significant P leaching was observed; however, organic P increases in the 0-5 and 5-10 cm sections, showing that P forms are affected by the ash action. Ash addition results in a solubilization of previously soil fixed P, the impact depend on the origin of ash and follow the sequence NA>PA>EA.

Acknowledgments: This study was supported by FONDECYT N° 1070116 grant.

Black Carbon Contribution to and Allophanic Soil as Affected by Agricultural and Natural Fire

F. Matus1'2*. Y. Rivas3, H. Knicker4, C. Rumpel5, E. Garrido3 and I. Cárcamo6

1Departamento de Ciencias Químicas, Universidad de La Frontera, P. O. Box 54-D, Temuco, Chile. 2Programa de Doctorado en Ciencias de Recursos Naturales, Universidad de La Frontera, Temuco, Chile. 3Escuela de Graduados, Universidad Austral de Chile, Valdivia, Chile. 4Lehrstuhlfiir Bodenkunde, TUMünchen, 85350Freising-Weihenstephan, Germany.5Chargée de recherche CNRS, Laboratoire de Biogéochimie et Ecologie des Milieux Continentaux (BIOEMCO), Centre INRA Versailles-Grignon Bátiment EGER. 78850 Thiverval-Grignon, France. 6Ingeniería ambiental, Universidad de La Frontera, Temuco, Chile. *E-mail: matus.francisco@gmail.com

Keywords: Black carbon; allophanic soils; Nothofagus sp.

Wildfire and burning practices on agricultural land contribute to the formation of black carbon (BC) which is one of the chemically most stable forms of organic matter. BC is defined as a continuum of condensed aromatic structures, which are biologically refractory that remains as a residue from incomplete combustion processes. Literature on Soil Organic Matter (SOM) alteration by fire in natural systems is still scarce. Here, we examine the effect of wildfire severities in a pristine Nothofagus sp. rain forest and of several decades of stubbles burning of harvesting agricultural residues on BC contribution to young allophanic soils. Unburned control in adjacent area was also sampled. The amount and nature of BC was determined in each layer down to 0.4 m depth by solid-state 13C NMR spectroscopy and after chemical oxidation. With this method the elemental resistant carbon (OREC) was recorded. NMR spectra were integrated and four areas of 13C-NMR chemical shift assigned (carboxyl-C, O-substituted aryl-C, C-substituted aryl-C and O-alkyl-C). Alkyl C was excluded because of its aliphatic nature. Additionally we used radiocarbon dating of bulk forest soil to gain information on SOM age. Our results indicate that BC contents in agricultural land ranged between 5% to 11% of initial C stock and both, burned and unburned soils presented similar amount of BC. Unexpectedly, more BC (19%) was found in deep soil (0.2-0.4 m) of burned site. In contrast, in the forest soils, BC content increased as fire severity increased from 7% in the control (unburned) to 16 % in the high severity treatment. On the other hand, BC was a distinct C pool from Al complexed organic matter as revealed by independent regression line between Al from pyrophosphate and Aryl C compounds (aromatics). This may indicate, that unlike observations made by other authors, BC in young allophanic soils is not stabilised by mineral interactions. Moreover, BC deposited on the soil surface across years can be transported vertically or lost horizontally by runoff, which could explain the low BC contents in both surface soils. In deeper soil layer, where radiocarbon age of 490 and 1.370 yrs were recorded, its preservation potential may be higher.

Interaction of Heavy Metals with Organic Matter of Chernozem in Model Experiments

G.V. Motuzova1*, T.M. Minkina2 and O.G. Nazarenko3

1Moscow State University, Faculty of Soil Science, Russia. 2South Federal University, Biological-Soil Faculty, Russia. 3Agroecological Faculty, Don State Agrarian University, Persianovskii, Rostov-on-Don, Russia. *E-mail: motuzova@mail.ru

Keywords: Heavy metals; organic matter; chernozem.

Compounds of metals with organic matter are obligatory soil components. Organic matter is active in bound of native and tecnogenic heavy metals (HMe). These interactions have the ecological significance because they suffer the alteration in the state as heavy metals, so organic matter. The object of investigation was the upper (0-20 cm) layer of an arable calcareous clay loamy ordinary chernozem with the properties: pHH2o 7.2, CaC03 11%, Corg 2.3%. Four kilograms of triturated (<5 mm) homogenized soil samples were placed in polyethylene vessels of 4 1, applied as dry acetates of Pb, Cu, and Zn separately at rates of 0-300 mg kg" (7 variants in triplicate) and wetted to the total moisture capacity. The vessels were incubated under natural conditions for two years. Soil samples were analyzed before the beginning of the experiment and after 1 and 2 years of incubation. There was determined the total HMe content in soils (after the decomposition with HF + HC104). The HMe species were sequentially extracted according to the Tessier schema, combined with some parallel extractions. Compounds of HMe strongly bound to organic matter were extracted with a 3.2 M CH3COONH4 (AAB) solution in 20% HN03 after oxidation of the organic substances with 30% H202 under 85°C. Metal compounds extractable by an AAB + 1% EDTA solution are classified as the potentially mobile forms. Among with the exchangeable ions, these compounds include the organo-mineral complexes of metals. The content of HMe in all extracts was determined by AAS method. Some parameters of organic matter state were determined: Corg total, for humus: Cha, Cfa, elemental composition. The initial contents of the metals in the soil were 24, 44, and 65 mg kg-1 for Pb, Cu, and Zn, respectively. The HMe content in the polluted soils exceeded their permissible critical level by 1.5-3 times. The 6- to 14-fold increase in the total content of metals in the contaminated soils was accompanied by an increase of HM compounds bound to organic matter by 17-30 times. A major part of the Pb and Cu applied to the soils entered into the organic matter. As a result, the share of these species increased to 23% of their total content in the soil. The enrichment of the organic matter with metals depended on the nature of the metal, they formed the following series: Pb > Cu > Zn. A major part of the metals retained by the organic substances in the chernozem (about half the total content of metals in the organic matter) was found in the mobile organomineral form. At the same time some alteration were noticed in organic matter. After the incubation of a chernozem with metal salts for two years, the content of fulvic acids increased and that of humic acids decreased; the Cha:Cfa ratio decreased from 1.0 to 0.5. The contamination also affected the elemental composition of the organic matter; its H:C ratio increased, which was indirect evidence for an increase in the aliphatic segment of the humus acid molecules. It was supported that interaction between metals and organic substances in contaminated soils can result in their mutual mobilization, modification of humus acid molecules, the formation of more stable soluble complexes. The metal contamination can result not only direst toxicological effect. Complexation of metals with organic matter can activate the organic substances and disrupt the humus status of chernozem that is a relatively stable system points to its ecological hazard.

Tillage-Induced Carbon Inputs in Soil in Rice-Wheat Cropping System: Farmer's Participatory Studies

N.S. Pasricha*

Potash Research Institute of India, Gurgaon, Haryana, India. *E-mail: nspasricha@sify.com

Keywords: Tillage; induced carbon; rice-wheat cropping system.

For sustainability of the rice-wheat production system, several resource conservation technologies are being promoted across the Indo-Gangetic plains of south Asia, where this cropping system covers an area of 13.5 million ha. The practice of burning the rice-straw for vacating the fields is common for timely seeding of following wheat crop. Burning of rice straw deprives soil its major source of organic matter (OM) and recycled plant nutrients. It has also become a source of atmospheric pollution. Zero tillage is one of such technologies which afford to recycle crop-residue in soil, thereby, helping not only to sequester OC but also prevents huge amounts of C02 emanating to the atmosphere due to burning of rice-straw in the fields. Farmer's participatory experiments were conducted at several sites across Punjab and Haryana states of India to compare the tillage effects on the carbon sequestration through efficient crop residue management. Results of 132 trials demonstrated a significant productivity increase in wheat by strategic tillage using zero-till-seed-cum-fertilizer-drill (ZT). The mean grain yield of wheat planted with ZT and conventional tillage (CT) were 4.25 and 3.52 ton ha- , respectively. This is mainly due to advancement of sowing with ZT, which ranged from 12 to 14 days. ZT technology reduced the turnaround time for sowing of wheat with residual moisture (no pre-sowing irrigation) having anchored rice-straw, by an average of 13.25 days. This practice helped, on an average incorporation of slightly more than 2.0 ton of C ha- . Changing to ZT saved approximately one million liters ha-1 of irrigation water from sowing till harvest of wheat crop. Decrease in soil (5-10 cm) temperature by an average of 3°C as a result of mulching effect of anchored rice straw in ZT plots during end March and till the harvest of wheat, is helpful in decreasing the rate of depletion of SOM through oxidation.

Isothermal Titration Calorimetric Investigation on the Effects of Temperature, pH and Salt Concentrations on Bacillus subtilis Adsorption on Clay Minerals and Iron Oxide

P. Cai*

State Key Laboratory of Agricultural Microbiology, College of Resources and Environment, Huazhong Agricultural University, Wuhan, Hubei 430070, China. *E-mail: cp@mail.hzau.edu.cn

Keywords: Bacillus subtilis; Clay mineral; Isothermal titration calorimetry.

The adsorption enthalpy changes (ΔHads) oí Bacillus subtilis on montmorillonite, kaolinite and goethite were determined using isothermal titration calorimetry (ITC) at various temperatures, pH values and KN03 concentrations to clarify the bacteria-mineral adsorption mechanisms. The values of ΔHads were in the range of -3.3 to -14.7 kJ kg-1 under experimental conditions, indicating the adsorption of Bacillus subtilis on minerals was exothermic. The A.Hads values of bacteria adsorption on minerals were not affected obviously by temperature and the absolute AHads values decreased with the increment of pH and the decrement of salt concentrations. These findings implied that hydrophobic effect and electrostatic interaction played an important role in Bacillus subtilis adsorption on clay minerals and iron oxides. Data obtained in this study provide valuable information for a better understanding of the interaction mechanisms between bacteria and minerals in soil and associated environments.

Use of Low Temperature Ashing Coupled with DRIFT-FTIR Spectroscopy to Characterize Soil Organic Matter Resistance to Degradation

A. Piedra Buena1*, A. Pucci2, P. Tinoco1, G. Almendros1 and L.P.D'Acqui2

1Centro de Ciencias Medioambientales - CSIC, Serrano 115B, 28006 Madrid, Spain. 2Istitutoper ¡o Studio degli Ecosistemi - CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino (Firenze), Italy. *E-mail: apiedrabuena@ccma. csic. es

Keywords: DRIFT-FTIR spectroscopy; soil organic matter; degradation.

Low Temperature Ashing (LTA) by oxygen plasma coupled with DRIFT-FTIR spectroscopy has been used to study the dynamics, function and protection of soil organic matter (SOM) in undisturbed aggregates. As the LTA technique can remove SOM from the mineral matrix of soil aggregates with minimal disturbance and damage to the inorganic constituents, the gradual oxidation of SOM can be monitorized by both spectroscopic and chemical analysis. Undisturbed aggregates (0.5-1.0 mm size) from six different soils from the hilly area of Madrid (Spain), both under undisturbed forest and cultured/reforested plots of the same formerly forested areas, were subjected to LTA treatments of 1, 5 and 24 hours respectively, in order to obtain the dynamics of C removal. The samples before and after the removal of organic material at the different steps were analyzed by DRIFT-FTIR spectroscopy and the residual organic material in the aggregates was extracted by chemical methods. The findings showed that C removal dynamics by LTA can be related to the type of SOM and to its interactions with the different mineral constituents of the aggregates. The characterization of organic matter of undisturbed aggregates by DRIFT spectroscopy was compared with the one obtained by chemical methods of extraction.

 

Evidences of Organic Matter Affecting the Clay Fraction Mineralogy of Volcanic Soils

C. Pizarro1. J.D. Fabris2, R.C. Graham3, E. Murad4 and J.W. Stucki5

1Facultad de Química y Biología, USACH, Av. L. B. O^Higgins 3363, Santiago, 7254758, Chile. 2Departamento de Química - ICEx, UFMG, Pampulha, 31270-901 Belo Horizonte, Minas Gerais, Brazil. 3Soil & Water Sciences Program, Department of Environmental Sciences, University of California, Riverside, CA 92521, USA. 4Bayerisches Landesamtfur Umwelt, Dienststelle Marktredwitz, D-9560, Marktredwitz, Germany, department of Natural Resources and Environmental Sciences, University of Illinois, Urbana, IL 61801, USA.*E-mail:cpizarro@lauca.usach.cl

Keywords: Organic matter; clay fraction mineralogy; volcanic soils.

Andisols and Ultisols forming on volcanic materials are abundant and widespread in Southern Chile. There, about 65% of all agricultural activities are usually carried out on these soils. Andisols are characterized by high organic matter (OM), relatively high amounts of iron oxides and poorly ordered aluminosilicates in the clay fraction; Ultisols have lower OM, higher iron oxide contents and a mineralogy mainly dominated by more crystalline compounds. The mineralogy of clay fractions from the B-horizon of two Ultisols (samples were collected in the localities of Collipulli and Metrenco, geographical coordinates of the sampling sites, 36°58'S 72°09'W and 38°50'S 72°37'W, respectively) and two Andisols (Diguillin and Freiré, 36°53'S 72°10'W and 38°57'S 72°36'W, respectively) was determined in this study, in order to search for evidence of the role of organic matter in the crystallization mechanism of clay minerals in these volcanic Chilean soils. The mineralogical analyses were mainly based on powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Mossbauer spectroscopy (MS) data. The OM contents were evaluated by the Walkley-Black method. The clay samples were sub-divided into two sub-samples each and treated with dithionite - citrate - bicarbonate (DCB) and ammonium oxalate (OX) solutions, in an attempt to selectively remove iron oxides and aluminosilicates with different degrees of crystallinity. From chemical analytical data, the Ultisol samples were confirmed to contain lower organic matter content (2.4 mass%) than Andisols (6.4 and 8.0mass% for Diguillin and Freiré, respectively). Phyllosilicates (mainly kaolinite and halloysite), gibbsite and Fe-oxides coating aluminosilicate grains were identified in the clay fraction of the Ultisol samples. From 6 K-M6ssbauer spectra, goethite, hematite, and maghemite were identified, along with some poorly crystalline iron oxyhydroxides, more easily removed by ammonium OX treatment. The XRD patterns for clay fractions of the Andisols resulted mostly in few broad reflections, which did not allow an unambiguous interpretation. After DCB or OX treatment, XRD patterns showed characteristic reflections of phyllosilicates. The 6 K-MS spectra of the clay fractions from the Andisols revealed hematite and some poorly crystalline iron oxyhydroxides that were not completely removed with the previous OX-treatment. In these volcanic Chilean soils, the organic matter accumulation tends to have an inhibitory effect on aluminosilicate stability and on the crystallization processes of iron oxides.

Acknowledgments: This work was supported by DICYT-USACH (Chile; grant 2070726), MIDEPLAN (Chile; grant Presidente de la República), CNPq and FAPEMIG (Brazil).

Surface Thermodynamic Study on Adsorption of Pseudomonas putida and Bacillus subtilis on Kaolinite and Montmorillonite

X. Rong. Q. Huang*, W. Chen, P. Cai and W. Liang

State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China, 430070. *E-mail: qyhuang@mail.hzau.edu.cn

Keywords: Bacteria; kaolinite; montmorillonite.

Understanding the sorption process of microorganisms on soil components is fundamental in predicting their fate in soil environments. The sorption characteristics of gram-negative Pseudomonas putida and gram-positive Bacillus subtilis on kaolinite and montmorillonite were investigated by surface thermodynamic approach in the current study. The surface thermodynamics provides critical information on the relative magnitudes of the different forces involving in bacterial-mineral adsorption. The total free energy for the sorption of bacteria on clay minerals (ΔG) was assumed to be the summation of ΔGH (hydrophobic interactions)ΔGEL (electrostatic interactions). Based on the state function, the magnitude of ΔGH was determined from the different interfacial tensions (contact angles) present in the system. The ΔGEL was calculated from A-potentials of the colloidal particles using three models, namely plate-plate, plate-sphere and sphere-sphere model by assuming the different shapes of the sórbate and sorbent, and the best plausible model was selected to obtain the ΔG. The calculated AGH was -3.5 and -2.4 mJ m2 for the sorption of P. putida on kaolinite and montmorillonite, respectively. The AGH increased by 60.0% and 45.5% for the sorption of B. subtilis on the two clay minerals. The ΔGEL was 0.882 and 0.827 mJ m2 for the sorption of P. putida on kaolinite and montmorillonite, and the ΔGEL decreased by 36.6% and 25.6% for the sorption of B. subtilis. The negative values of ΔGH and the positive values of ΔGEL suggested that the hydrophobic force favored the adsorption of bacteria on the two clay minerals, while the electrostatic force contributed negatively to bacterial adsorption. The magnitude of ΔG were -2.62 and -1.57 mJ m2 for the sorption of P. putida, and -5.04 and -3.79 mJ m2 for that of B. subtilis on kaolinite and montmorillonite, showing that the adsorption of bacteria on clay minerals was a thermodynamically spontaneous process. These results also imply that clay minerals possess higher affinity for the gram-positive bacteria in soil system. The quantification of bacterial adsorption to clay minerals in terms of free energy in this study would be helpful for a better understanding of the mobility of bacteria and the formation of bacteria-mineral complexes in soils and sediments.

 

Is Bradford Reactive Soil Protein, Glomalin, Stabilised by Association with Allophane in Forest Soils of Martinique, French West Indies?

S. Staunton1*. T. Woignier2, P. Etcheverria3, F. Borie3, T. Chevallier4 and H. Quiquampoix1

1INRA, UMR 1222 (Biogéochimie du Sol et de la Rhizosphére), France. 2IRD, UR Seqbio, B.P. 213 Petit Morne, 97232, Le Lamentin, Martinique. 3Univiversidad de La Frontera, Casilla 54-D, Temuco, Chile. 4IRD, UR Seqbio, Montpellier 34060, France. *E-mail: staunton@montpellier.inra.fr

Keywords: Glomalin; allophane; forest soils.

Soil organic matter plays an essential role in mitigating the effects of rising levels of atmospheric C02 and the corresponding rise of temperature and increase in the frequency of extreme weather conditions. Glomalin, first reported in 1996 by Wright & Upadhyaya (1996) may be an important component of soil organic matter in terms of soil physical structure and resistance to breakdown. This glycoprotein is produced by the hyphae of arbuscular mycorrhizal fungi and secreted into the soil where it may accumulate. In some soils, glomalin may account for a large proportion of soil carbon, and on a global scale may represent an important carbon sink. Oxides of iron and aluminium are thought to protect glomalin and decrease its turnover time. In addition, it has been suggested that, in common with fungal polysaccharides, glomalin may play an important role in the stability of soil aggregates. We have studied the glomalin contents of soils sampled from A and B horizons of forest soils of Martinique, French West Indies. Both easily extracted (one short autoclave extraction in 20 mM sodium citrate solution at pH 7) and total (five 1-hour extractions in 50 mM sodium citrate solution at pH 8) glomalin contents were measured as Bradford reactive BSA-equivalent protein. The glomalin contents were compared to other soil properties. Glomalin contents ranged from about 1 to 36 g kg-1 accounting for up to 10% soil organic carbon. Such levels of glomalin are high although even larger levels have been reported for Chilean Andosols. Glomalin contents were strongly correlated with organic carbon and allophane contents for surface soils. For sub-soils, glomalin content followed the same trend with organic C content as surface soils, but showed no significant relationship with allophane content. There was no correlation between the ratio of glomalin to total organic carbon content with the allophane content, suggesting that this mineral accorded similar protection to glomalin and other forms of stable organic matter. The glomalin content also followed a similar trend to that of soil respiration rate. However, since the latter was strongly correlated with organic carbon content, the effect is probably not direct. There was no correlation between the glomalin content and any other microbial parameter measured (microbial biomass, relative respiration rate or respiratory quotient. About half the soil glomalin was easily extractable in surface soils, whereas the fraction was smaller and more variable for B-horizon soils. This contrast between glomalin in surface and deeper horizons suggests that glomalin is transformed with time in contact with the solid phase.

Radiocaesium Transfer in Mountainous Ecosystems in Central Balkan 20-Year after the Chernobyl Accident

M. Zhiyanski1, J. Bech B.2, M. Sokolovska1, P. Turne3* and J. Bech R.4

1Forest Research Institute, Bulgarian Academy of Sciences, 132 "Kl. Ohridski" Blvd., 1756 Sofia, Bulgaria. 2 Chair of Soil Science, Faculty of Biology, University of Barcelona, Spain. 3Engineering Faculty, Universidad Católica de la Santísima Concepción, P.O. Box 297, Concepción, Chile. 4Department of Astronomy and Meteorology, C/Martí i Franqués 1, 08028, University of Barcelona, Spain. * E-mail: ptume@ucsc.cl

Keywords: Radiocaesium; mountainous ecosystems; forest soils.

Following the Chernobyl accident a number of natural and semi-natural environments were contaminated by radiocaesium mainly through wet deposition. Radiocaesium deposited in these areas has a long term impact on the environment. This fact is attributable to the persistence of radiocaesium in all compartments of forests, pastures and natural meadows. During the last twenty years scientific efforts were directed towards the comprehension of the transfer phenomena of radionuchdes in the ecosystems. Despite of this, few studies were conducted to compare the Cs-137 soil-to-plant transfer between native beech forest, pure spruce plantation and upland mountainous pasture in the Central Balkan Mountain in Bulgaria. We compared Cs-137 contents in forest floor, in upper mineral soil layers and in plant species in mountainous pasture, 45-yars old natural Fagus silvática L. forest and 45-years-old Picea abies Karst, forest. We indicated that 20-years after Chernobyl accident the main concentrations of Cs-137 are located in forest floor layers. The little thickness of forest floor was related with comparatively lower Cs-137 content. The higher organic C content in upper mineral soil layers was related with higher Cs-137 contamination and easier soil-to-plant transfer in the mountainous pasture. The relatively higher clay content in upper mineral soil under the plantation was related with lower transfer of Cs-137 towards spruces, despite of their surface root system. 20-years after the main pollution after the Chernobyl accident the transfer factors for caesium-137 for studied plant species were low and varied between 0.01 and 0.02. The grass vegetation had the highest Cs-137 soil-to-plant transfer compared with beech and spruce.

Factors Influencing Competitive Sorption of Cupper and Lead on Ferrihydrite and Goethite

J. Zhu1*. L. Perelomov2, V. Cozzolino3, M. Pigna3 and A. Violante3

1 College of Resources and Environment, Huazhong Agricultural University, Wuhan 730070, China, 2Department of Biology and Medicine, Tula State University, Russia.3 Dipartimento di Scienze del Suolo, della Pianta, dell Ambiente e delle Produzioni Animali, Universita di Napoli Federico II, Portici(Napoli), Italy. *E-mail: junzhl002@sina.com

Keywords: Heavy metals; ferrihydrite; goethite.

Mobility of trace elements in soil environments is affected by sorption-desorption reactions, which are the predominant factors that control the bioavailability of heavy metals. Few studies have been carried out on the competition in sorption of heavy metals to soil components and soils. Competition in sorption between two or more trace elements is of great importance for understanding their relative affinity for a given sorbents. Variable charge minerals selectively sorb polyvalent cations even when their surfaces are positively charged (solution pH lower than the PZC of the sorbents). Competitive sorption between two (or more) heavy metals seems to be affected by pH, surface properties of the minerals, nature and concentration of heavy metals and presence of inorganic and organic ligands. We have carried out experiments on the sorption of copper and lead added alone or together onto synthetic ferrihydrite and goethite as affected by pH, concentration of the heavy metals (initial Cu/Pb molar ratio of 0.5, 1 and 2), sequence of addition of the trace elements onto the sorbents and presence and concentration of oxalate and/or tartrate (among the most abundant low molecular-weight organic anions present in soil environments, mainly at the soil-root interface). At pH 4.5-5.0 the sorption isotherms of these two heavy metals fitted the Langmuir equation (L-type) and showed a higher affinity of cupper for goethite, but a much greater affinity of lead for ferrihydrite. The sorption of both trace elements was strongly increased by increasing pH. In particular, the pH50 (the pH value at which 50% of the total sorption of the elements has occurred) was 4.90 and 5.90 for cupper and 5.20 and 4.40 for lead on goethite and ferrihydrite respectively. In the presence of increasing concentration of oxalate (OX/Me molar ratio [R] ranging from 0 to 10) the pH50 of cupper sorbed onto goethite decreased from 4.90 at R=0 to 3.85 at R=4 and then increased up to 4.74 at R = 10, whereas the pH50 of lead was less affected by the presence of oxalate. The two heavy metals strongly competed with each other for sorption sites on the surfaces of the oxides. At pH 4.5-5.0 the sorption of a given metal onto ferrihydrite and goethite was inhibited in the presence of increasing concentrations of the other element. By adding the two heavy metals together in equimolar amounts (25 mmol added per kg) on the oxides, cupper sorption was reduced by lead of 35% onto ferrihydrite and of 11% onto goethite, whereas lead sorption was reduced of less than 5% onto ferrihydrite and 24% onto goethite. Competition in sorption between the two heavy metals was affected by the sequence of addition and the residence time of the first element added to a given sorbent. Finally, the presence of oxalate and/or tartrate previously added to ferrihydrite or goethite or added as a mixture with cupper and lead strongly affected the competitive sorption of these heavy metals on the iron oxides.

Comparison of Carbon Sequestration in Volcanic and Non-volcanic Soil of Chile

E. Garrido1,2 *, F. Matus3'4 and N. Sepúlveda3

1Programa de Doctorado en Ciencias Agrarias. Escuela de Graduados, Universidad Austral de Chile. 2Facuitad de Ciencias Agrarias y Forestales. Universidad Católica del Maule. 3 Departamento de Ciencias Químicas, Universidad de La Frontera. 4Programa de Doctorado en Ciencias de Recursos Naturales, Universidad de La Frontera, Temuco, Chile. *E-mail: egarrido@ucm.cl

Keywords: Carbon sequestration; allophane; volcanic soils.

The organic carbon (OC) stabilization and sequestration mechanisms differ due to the presence of aluminum (Al) in the soil solution, allophane and imogolite type materials in volcanic soils and the amount of silt + clay crystalline minerals in non volcanic soils. The objective of this work was to compare these factors of stabilization on OC immobilization in both, volcanic and non volcanic soils of Chile. We selected agricultural sites with similar managements (cropping and grassland); all soil belongings to the order: Andisol, Ultisol, Molisol, Vertisol, Alfisol and Inceptisol (USDA classification). Soils samples were taken at 0-0.1, 0.1-0.2, and 0.2-0.4 m depth. The analysis were carried out for extractable Al with Na pyrophosphate (Alp), acid ammonium acetate (Ala), CuCl2 (AlCu) and OC in: Whole soil, fractions 0-53 um and the supernatant of pyrophosphate (Cp). We also determine water pH, bulk density and allophane content by Al/Si ratio. Our study confirmed previous results in non volcanic soils; Particles 0-53 um (silt + clay) was positive and significantly related with whole soil OC (R2 = 0.5) and the OC in 0-53 um (R2 = 0.8). The opposite being true in volcanic soils; instead, soluble C, Cp was highly related with soil OC and constituted ca. 43 % from this amount. Allophane content (about < 13 %) was positive and significantly related with the soil OC (R2 = 0.6) and OC in the fraction 0-53 um (R2 = 0.8). The small amount of allophane may exert large influence on soil aggregation and it in turn on physical protection of soil organic matter. This was supported for the good relationship between allophane and total porosity of soils. We confirmed that the differences in soil organic C stabilization in volcanic with respect to non volcanic soils are due to the clay mineralogy and active Al, which complexed near half amount of whole soil organic C. The rest is assumed to be associated with Allophane per se and physically protected in soil aggregates. We also confirmed that Ala (which is similar to CuCl2 extraction) was highly and positively related with OC of volcanic soils.

Soil Organic Carbon Determination Associated to Active Al under Different Managements

M. Panichini1*, F. Matus1'2 and N. Sepúlveda2

1Programa de Doctorado en Ciencias de Recursos Naturales, Universidad de La Frontera, Temuco, Chile. 2Departamento de Ciencias Químicas, Universidad de La Frontera, Temuco, Chile. *E-mai¡: marcelopanichini@gmail. com

Keywords: soil organic carbon; aluminum; allophanic soils.

Decrease of soil organic carbon (SOC) proceeds from the conversion of natural to agricultural ecosystems and it has contributed to raise the level of atmospheric C02. There is still little information about the mechanisms of stabilization of organic matter (OM) in allophanic soils. A key factor is the active Al complexed with organic compounds which has been previous reported by a significant and positive relationship with SOC. However, the quantity and quality of soil organic C bound to Al has not been quantified yet in our soils. The aim of this study was to determine the C associated with the Al (Cp) in the supernatant of Na-pyrophosphate at pH 10 extraction. Cp was measured by potassium dichromate in a range of 10 Andisols from Southern Chile, sampled between 0-40 cm. The results showed a good correlation (R2= 0.72, P < 0.01) between Cp and SOC. Approximately 45% of soil organic C corresponded to Cp, confirming that the active Al immobilized significant amounts of organic C in our allophanic soils.

 

Preparation of a Humic Acid/Polypirrole Modified Pige Electrode and its Prospective Environmental Use

M. Antilén* and J. Armijo

Departamento de Química Inorgánica, Facultad de Química, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, 6904411, Chile. *E-mail: mantilen@uc.cl

Keywords: Humic acids; chelating agents; paraffin-impregnated graphite electrode

Owing to their polyfunctionality, humic acids (HAs) are among existing natural organic compounds' most powerful chelating agents. Thus, many studies have demonstrated the important interaction between HAs and varied contaminants, which form complexes of different chemical-biochemical solubility and stability. This means that HAs might modify environment contaminants availability, transport, fixation, and toxicity. On the other hand, conductive polymers' properties offer an amply variety of applications, e.g., doping-undoping process that can be carried out by electrochemical means and has been utilized as contaminants extracting method. Thus, the aim of the present work is the preparation of a humic substances modified PIGE electrode that will be evaluated regarding its potential environmental use for chemical species of interest, compared to those described in the literature. All electrochemical experiments were performed using a VoltaLab PGZ100 potenciostat system, in a glass three-compartment three electrodes cell under argon atmosphere. A paraffin-impregnated graphite electrode (PIGE) was used as working electrode. The counter electrode was a Pt wire and all potentials were measured with respect to Ag/AgCl reference electrode. Humic acid was transferred and immobilized onto the electrode surface by the abrasive transfer technique. Electrochemical growth of polypyrrole (Ppy) films was carried out on PIGE or PIGE/HA from ImM pyrrole + 1 mM Na2S04+ 3-10-2 M H2S04 by a potentiodynamic method applying 5 cycles between - 200 and 1000 mV. Next, two of the prepared electrodic surfaces (PIGE/HA/Ppy and PIGE/Ppy) were studied in the presence of ImM As043- + ImM Na2S04 + 3 x-10-2 M H2S04 (cell A) and in ImM Na2S04 + 3 x 102- M H2S04 (cell B) solutions respectively, in order to select the doping-undoping potential to perform the extractions (ExC). The total volume of electrolyte in each cell was always 10.0 mL. Each ExC was accomplished as follows: the PIGE/Ppy or PIGE/HA/Ppy modified electrode was immersed in A, potentiostatically perturbed (0.4 V) during 5 min, after which was immersed in B, where it was potentiostatized at -0.5 V during 5 min. Initially and after several ExC, arsenic concentration in A and in B was determined by ICP-OES spectroscopy using a Varían Liberty Serie II instrument. As(V) concentration found before and after the extraction using the PIGE/HA/Ppy showed an extracting efficiency of 0.34 mg L-1 for 10 extractions, considering the electrode area as 28.25 mm2. The observed efficiency corresponds to the incorporation of the HA into PIGE. As for the charge transfer, the process was not wholly reversible.

Acknowledgements. The authors thank financial support from VRAID of Pontificia Universidad Católica de Chile through Límite 2007 project.

 

Evaluation of The Oxidation Capacity of Humic Acids Extracted from Chilean South-Central Soils

M.A. González1, M. Antilén1*, J. Armijo1, M. Briceño2 and J. Canales3

1Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860,6904411, Santiago, Chile. 2Universidad Arturo Prat, Casilla 121, Iquique, Chile.3 Universidad de La Frontera, Casilla 54-D Temuco, Chile. *E-mail: mantilen@uc.cl

Keywords: Humic acids; redox properties; acid-base characteristics.

Humic acids (HAs) are soil constituents found as negatively charged colloids, biodegradable that can be stored for long periods of time. Also, these humic compounds present the properties of participating in redox reactions with elements such as Fe (II), Mn(IV), V(V), and Hg(II). The linkage of these materials to redox reactions and the scarce information in this respect, arouse interest concerning to their determination and characterization, as well as their likely applications to varied processes. The redox characterization will enable evaluation of, based upon cell potential and oxidation capacity of HAs, the actual possibility of utilizing theses substances as base materials for feasible redox processes in analites of interest. Consequently, the aim of this work is to study and to establish the differences related to redox properties and acid-base characteristics of humic acids obtained from soils of the Chilean South-central region. Conductivity, pH, chemicals analysis, and organic matter for all soil samples [Collipulli (C), Colina (CL), Diguillín (D), and Ralún (R)] were determined. Extracted HAs, using the IHSS's recommended procedure, were characterized by elemental analysis, phenolic and carboxylic groups, UV-Vis, and FT-IR. Cell potential and oxidation capacity were determined by redox titration of a 50-mg sample at pH 7.0 using I2 as titrant. End point was detected by means of a conjugated glass electrode and Pt under Ar atmosphere. Each titration took nearly 3-5 h because of the necessary stabilization required after each titrant addition. From the obtained cell potential, HA-D displayed the highest reduction values (438.3 ± 9.78 mV), becoming thus the humic fraction that possesses more energy to bring about oxidation processes. Analyses of the remaining samples enables establishing the following sequence: HA-C > HA-CL > HA-R (364.2 ± 39.7 mV). However, the cell potential must be evaluable concomitantly with the oxidation capacity since this allows establishing how much of the species of interest will be oxidized. As for HAs extracted from soils, a slight correlation of the oxidative capacity with the phenolic groups was found (R2=0.863), which would enable associating the existence of these groups to a lesser oxidation capacity. According to the obtained results it may be inferred that the humic fraction of D-soil is the one having the most suitable redox conditions to oxidize chemical species of interest contained in soil-solution currently under survey using electrochemical techniques.

Acknowledgements: The authors thank financial support from VRAID of Pontificia Universidad Católica de Chile through Límite 2007 project.

 

Reduction of Ammonia Loss by Mixing Urea with Humic and Fulvic Acids Isolated from Peat Soil

S. Kasim1*. O.H. Ahmed1, N.M.A. Majid1 and K. Yusop2

'Department of Crop Science, Faculty of Agriculture and Food Science, University Putra Malaysia Bintulu Campus, Sarawak, 97008 Bintulu, Sarawak, Malaysia. 2Department of Land Management, Faculty of Agriculture, University Putra Malaysia, 43400 Serdang, Selangor, Malaysia. *Email: susilawati@putra. upm. edu. my

Keywords: Ammonia loss; humic and fulvic acids; peat soil.

Surface application of urea is less effective due to high loss of N through volatilization. Rapid increase of pH (at soil microsite) and low soil exchangeable cations are some of the factors affecting urea-N efficiency. In order to improve urea-N use efficiency as well as contributing to reduction of environmental pollution, granular urea was mixed with liquid humic acid (LHA) only, liquid fulvic acid (LFA) only, and LHA + LFA isolated from a tropical peat soil. The presence of LHA only, LFA only, and LHA + LFA significantly reduced ammonia loss by 29.2, 11.4, and 8.1% respectively as compared to urea only (urea without additives). The high total acidity (417 to 583 cmol kg-1) of these treatments may be one of the reasons for the significant reduction of ammonia volatilization. The other reason was that the treatments (LFA only and LHA + LFA) significantly retained ammonium ions compared to urea only. The high exchange properties of the treatments may have retarded urea hydrolysis and hence the reduction of ammonia volatilization. Urea amended with LHA only or LFA only or LHA + LFA could reduce ammonia loss, hence their potential of improving urea-N-use efficiency as well as contributing to the reduction of environmental pollution.

Effect of Wildfire on Soil Organic Matter Dynamics and Quality in a South Chilean Andisol

Y. Rivas1*. D. Huygens2, O. Van Cleemput2, R. Godoy1 and P. Boeckx2

1instituto de Botánica, Universidad Austral de Chile, Casilla 567, Valdivia, Chile. 2Laboratory of Applied Physical Chemistry-ISOFYS, Ghent University, Coupure 653 9000 Gent, Belgium. *E-mail: yessicarivas@uach. cl

Keywords: Ammonia loss; humic and fulvic acids; peat soil.

Old-growth forests of Southern Chile represent an important reserve of temperate forests in the World. The precipitation chemistry in Chile still reflects a cloe approximation of pre-industrial conditions. In this way, the productivity of the ecosystem depends on the internal cycling of soil organic matter (SOM). However, catastrophic events, such as wildfires can disturb this balance and produce important changes in the physical and biogeochemical properties of soils and as a consequence to the ecosystem sustainability. The isotopic composition of SOM is a useful tool for elucidating the different mechanisms of SOM decomposition processes. Araucaria-Nothofagus forests in the Andean mountains of Chile (38°S, 71°W) were affected by wildfire (February, 2002) providing an "experimental field" to study its effect on SOM. The objective of this investigation was to analyze the effect of the fire on the quality of SOM at different soil depths. We used δ13C and δ15N signatures coupled to size and density fractionation to evaluate SOM dynamics. In the burned site, the different SOM fractions were depleted in δ13C and enriched in δ15N when compared to the unburned site. Our result respect to C dynamics suggest that: fire induces changes in C composition of the SOM, toward more depleted C compounds due to increase charcoal components. Respect to N dynamics, we found increased nitrification rate after fire and because nitrification discriminates against 15N, this may in turn lead to a 15N-enriched residual in soil. This conclusion indicates that 513C and 515N can be used as proxy to assess the fire on C and N dynamics. This conclusion is noted, especially, in the upper soil layers (0-10 cm).

 

Comparative Study of Structural and Physical-Chemical Characteristics of Nanoparticles Extracted from two Andisols of Southern Chile: Potential in Agricultural Application

M. Calabi1, M. Cea2*. P. Reyes4, A.A. Jara3, S. Sanhueza2 and M.L. Mora3

1Programa de Doctorado en Ciencias de Recursos Naturales,2Laboratorio de Suelos, Instituto de Agroindustria, and3 Departamento de Ciencias Químicas, Facultad de Ciencias, Ingeniería y Administración, Universidad de La Frontera, Temuco, Chile. 4Laboratorio de Microscopía Electrónica, Universidad de Concepción, Concepción, Chile. *E-mail: mcea@ufro.cl

Keywords: Nanoparticles; nanostructured surfaces; Andisol.

Chemical surface fuctionalization and surface structuring particularly on the nanometer scale play an increasing role in many fields of technological application. However, the production of nanoparticle with small diameters and a narrow size distribution is challenging and expensive. Therefore, natural nanoparticles are a cheap alternative if the size distribution is narrow and the extraction of the particles from soil material is economically efficient. Our goal is to provide nanostructured surfaces based on natural nanoparticles particularly for agricultural application (e.g. Biofertilizer or pesticides of controlled release). The first stage of our study contemplates the extraction and characterization of nanoparticles from two Andisols belonging from Piedras Negras and Temuco series of southern Chile. To obtain the nanometric fraction of soils (nanoclays covered with organic matter), first we separate the < 0.02 mm fraction by a sedimentation method based on Stokes's law. From this fraction, the nanoparticles were obtained according the methodology described by Li and Hu (2003). The nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), infrared spectroscopy (FTIR) and also, were determinated the isoelectric point (PIE) and specific surface area Brunauer-Emmett-Teller (SSABet) of both materials. Transmission electron microscopy micrographs revealed more or less condensed aggregates of nanoparticle and the obtaining material corresponds to nanoclays with a particle average size less than 50 nm for Andisols series Piedras Negras and less than 100 nm for Temuco series, which displaying homogeneous elemental compositions, with Al/Si molar ratios ranging ~ 2:1. SEM showed aggregates of nanoclays with variable pore size, which can adsorb high quantity of water generating microenvironments benefit for an adequate mass transfer. The FTIR spectra showed characteristic bands of the soil organic matter (fulvic and humic acids). Low values of PIE (3.2) are attributed to the organic matter covering of nanoclays. Variations in SSABet and in mesoporous and microporous between both materials were observed (14 m2 g-1 and 8 m g-1 for Piedras Negras and Temuco series respectively). The shape of the nitrogen adsorption-desorption isotherms allows two types of curves BET, nanoparticles from Piedras Negras series presented a curve Type II that suggest the presence of a relatively well-calibrated pore and a narrow pore-size distribution, and nanoparticles from Temuco series presented a curve Type III suggesting high microporosity and relatively low nitrogen-adsorbed volumes. From the results, we can conclude that both nanomaterials are promising to be used in biocatalysis or in other technological application, because of suitable confinement and enzymatic stabilization that those support nanomaterial can provide.

Acknowledgments: We wish to thank FONDECYT projects N° 1061262, N° 11070241 and N° 3080039, and Scholarship CONICYT N° 24080106.

Natural Nanoclays: Physicochemical Characterization

E.G. Garrido1*. A.A. Jara2 and M.L. Mora2

Keywords: Natural nanoclays; allophane; aluminosilicate.

1Programa de Doctorado en Ciencias de Recursos Naturales, Universidad de La Frontera, Temuco Chile. 2 Departamento de Ciencias Químicas, Universidad de La Frontera, Temuco, Chile. *E-mail: eggarrido@ufro.cl

Nanotechnology is an emerging science with different applications in scientific and technological research. Studies with nanoclays have carried out to resolve environmental problems, due to its small size, high surface area, and charge characteristics. The nanoclays have a potential use in the pollution removal, mainly as adsorbent compounds and catalytic support. Allophane is the main component of the clays fraction of Andisols of Southern Chile. It is an aluminosilicate non-crystalline, amorphous to X-ray, which presents a short-range order in its structure with a predominance of Si-O-Al bonding (Wada and Wada, 1977). In these soils, the allophane is covered by amorphous iron oxide (hydrous ferric oxide and ferrhydrite), giving the Andisols typical features of iron oxides than allophane, even though it has been reported that Fe oxides normally not exceed 10% in these soils. The aim of this study was to characterize nanoclays from an Andisol of Southern Chile. Natural nanoclays were extracted using the methodology described by Liu et al. (2005) from a soil without organic matter. The nanoclays were characterized by the surface area and the micropores volume using the BET and Broekho and de Boer methods. The surface charge properties were evaluated by the isoelectric point (IEP), the Point of zero salt effect (PZSE) and the Zero point charge (ZPC), through electrophoretic mobility, potentiometric titration and Parks model (Parks, 1967), respectively. The natural nanoclays showed an Al/Si ratio of 0.24, the surface area of 124 m2g-1 and volume of micropore 0.018 cm3 g-1. The shape of adsorption-desorption curves were similar to synthetic allophane with Al/Si ratio < 5 reported by Montarges-Pelletier et al. (2005). It suggests a wide pore size distribution and high content of mesopores. The zero point charges were 3.8 (ZPC), 7.0 (IEP) and 5.4 (PZSE). These values support that the superficial composition is different from their percentage composition. Therefore, the properties nanoclays evaluated in this study showed similar characteristics of aluminosilicate coated with iron oxides previously synthesized (Jara et al., 2006).

Acknowledgements: This work was support by Fondecyt Grant 11070241.

References

A.A. Jara, S. Goldberg and M.L.Mora. (2005). J. Colloid Interface Sci. 292: 160-170.

Y. Liu, H. Liu and N. Hu. (2005). Biophysical Chemistry 117: 27-37.

E. Montarges-Pelletier et al. (2005). Colloids Surf. A: Physicochem. Eng. Aspects 255: 1-10.

G.A. Parks. (1967). In: W. Stumm, Ed., American Chemical Society Advances in Chemistry Series 67:121-160.

S.-I. Wada and K. Wada (1977). Clay Minerals 12: 289-298.

 

Allophane Nanoclays: The Potential Use to Increase the Catalytic Efficiency of Acid Phosphatase Enzyme

M. Calabi1*. A. Jara2 and M.L. Mora2

1 Doctorado en Ciencias de Recursos Naturales, Universidad de ¡a Frontera, Temuco Chile 2 Departamento de Ciencias Químicas, Universidad de ¡a Frontera, Temuco Chile. E-mail:mcalabi@ufro. el

Keywords: Natural nanoclays; allophane; aluminosilicate.

Natural nanoparticles occur widely in soils derived from volcanic ash like Andisols. The more important constituent of Andisols is allophane, which is an aluminosilicate non-crystalline. These nanoclays have morphology sphereroidal with an outer diameter of 3.5-5.0 nm, the think wall (0.7-1.0 nm) is composed of an outer Al octahedral sheet and an inner Si sheet. Also, defects in the wall structure give rise to perforations of ~ 0.3 nm diameter. These nanoparticles form stable microaggregates, with pores within the nanoscale range with similar physical characteristics to silica nanomaterials which were very important in biocatalysis. Studies have reported that nanomaterials are more promising clays for enzyme immobilization compared to conventional materials. The aims of this study were: characterize natural clay and nanoclay with and without organic matter from an Andisol and ii) evaluate clay and nanoclays as support to immobilize acid phsophatase. An Andisol, Piedras Negras soil from Southern Chile was sampled within 0-20 cm of depth, sieved to 2 mm mesh and air-dried. One part of the soil was treated with 30% hydrogen peroxide to remove the soil organic matter. The separation of particle-size < 2 um fractions was obtained by sedimentation procedures based on Stoke's law. Natural nanoclays were extracted using the methodology described by Liu et al. (2005). The clays and nanoclays were characterized by using energy dispersive X ray (EDX), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and electronic diffraction (ED). Synthetic complexes were formed by interaction between acid phosphatase and either allophanic clay or nanoclay, and used as model systems to simulate enzymatic reactions occurring in heterogeneous environment. The enzymatic activities of immobilized phosphatase on nanoclay, with or without organic matter, were measured with p-nitrophenylphosphate (pNPP) as substrate. The kinetics parameters (Vmax and Km values) were calculated by a non-linear regression analysis according to the Michaelis-Menten equation. The TEM analysis showed the nanoclay presence (< 50) nm in the samples evaluated. The occurrence of amorphous and crystalline particles were observed by DE analysis in samples the clay and nanoclay. The SEM analysis the immobilized phosphatase showed cavities of different sizes. The enzymatic activity increased in 90 % compared with the free enzyme. Likewise, the kinetic parameters showed that the catalytic efficiency (between 60 and 70 %) and Vmax (between 110 and 130 %) were enhanced.

Acknowledgements: This work was support by Scholarship CONICYT N° 24080106 and Fondecyt Grant 11070241.

References

Y. Liu, H. Liu and N. Hu. (2005). Biophysical Chemistry 117: 27 - 37.

 

Greenhouse Gases Emissions from Soils with Different Anthropogenic Influence in Southern-Central Chile

C. Muñoz1*. L. Paulino1, N. Stolpe1, C. Ovalle2 and E. Zagal1

1Departmento de Suelos y Recursos Naturales, Universidad de Concepción, Campus Chilian, Chile. 2Departamento de Producción Animal, Instituto Nacional de Investigaciones Agropecuarias (INIA) Quilamapu, Chillan, Chile. *E-mail: cristinamunoz@udec.cl

Keywords: Greenhouse Gases; climate change; anthropogenic activities.

The anthropogenic activities are potential sources of Greenhouse Gases (GHG) emissions where C02 and N20 are of relevance in agricultural systems. In South America few information is available about in situ quantification of GHG from agricultural and agroforestry systems. In Chile, a national inventory was done based on factors proposed by the Intergovernmental Panel of Climate Change (IPCC) for the most representative systems, but reveled the lack of information for their particular characteristics of soil (meanly volcanic ones) and climate considering the most relevant productive activities at the country or region scale. A recently financed project of our research group has the main aims to assess biogeochemical processes related to GHG emissions (meanly C02 and N20) from soil under different anthropogenic influence, including agriculture uses and management of Southern-Central Chile. The methodology includes periodical in situ GHG sampling through non-fixed closed chambers (200 cm ), at least once a month and after events (meteorological or fertilization) during 3 consecutive years, simultaneously with records of meteorological data (e.g. precipitation, wind direction wind speed, relative humidity of air, temperature) and soil conditions (e.g. temperature, moisture and mineral N content as (-NO3 and -NH4). Gas sampling will be performed under different soil uses as native forests, exotic forest plantations (Pinus radiata), long-term prairie (Medicago sativa), agroforestry (with exotic species, intensive wheat (Triticum aestivum), oat (Avena sativa), prairie (Trifolium sp.) and maize crop (Zea Maize) rotation) including different soil and climate types. Also a no-till system under different nitrogen fertilization type and lime rates is considered as management field tray. The preliminary results indicate that the soil use intensity produce effect in C02 emission with major rate in agroforestry and pasture (with 52 t ha-1 year-1 each) compared with no-till (35 t ha-1 year-1 ), but it is necessary to reinforce that information with measurements during 3 years at least. The N20 emission rates were not well discriminated from different soil use due to very low amounts released. Sampling of C02 and N20 at the other areas are to be started, and will add complementary information about the contribution of soil types on GHG emission from different scenarios of economic relevance.

Acknowledgments: Fondecyt Project (N° 1080076) and Programa Bicentenario de Ciencia y Tecnología, "Inserción de Investigadores a la Academia 2005 (PSD-12)", CONICYT-World Bank-Universidad de Concepción.

 

 

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