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Partie B; International audience; Incidental zinc sulfide nanoparticles (nano-ZnS) are spread on soils through organic waste (OW) recycling. Here we performed soil incubations with synthetic nano-ZnS (3 nm crystallite size), representative of the form found in OW. We used an original set of techniques to reveal the fate of nano-ZnS in two soils with different properties. 68 Zn tracing and nano-DGT were combined during soil incubation to discriminate the available natural Zn from the soil, and the available Zn from the dissolved nano-68 ZnS. This combination was crucial to highlight the dissolution of nano-68 ZnS as of the third day of incubation. Based on the extended X-ray absorption fine structure, we revealed faster dissolution of nano-ZnS in clayey soil (82% within 1 month) than in sandy soil (2% within 1 month). However, the nano-DGT results showed limited availability of Zn released by nano-ZnS dissolution after 1 month in the clayey soil compared with the sandy soil. These results highlighted: (i) the key role of soil properties for nano-ZnS fate, and (ii) fast dissolution of nano-ZnS in clayey soil. Finally, the higher availability of Zn in the sandy soil despite the lower nano-ZnS dissolution rate is counterintuitive. This study demonstrated that, in addition to nanoparticle dissolution, it is also essential to take the availability of released ions into account when studying the fate of nanoparticles in soil.

International audience; Organic waste (OW) reuse in agriculture is a common practice fostered by benefits in terms of waste recycling and crop production. However, OW amendments potentially affect the fate of pesticide spread on fields to protect the crops from pests and weeds. The influence of OW on the sorption, degradation, and leaching of pesticides is generally studied for each mechanism separately under artificial laboratory conditions. Our study aims at evaluating the balance of these mechanisms under more realistic conditions to clarify the influence of three common OW amendments on the fate, in soil, of the widely used herbicide S-Metolachlor. We performed leaching experiments in large undisturbed soil cores amended with raw sewage sludge, composted sludge, and digested pig slurry (digestate), respectively. We monitored S-Metolachlor and its two main metabolites MET-OA and MET-ESA in the leachates during a succession of 10 rainfall events over 126 days. We also quantified the remaining S-Metolachlor and metabolites in the soil at the end of the experiments. S-Metolachlor leaching didn't exceed 0.1% of the applied dose with or without OW amendment. Despite a soil organic carbon increase of 3 to 32%, OW amendments did not significantly affect the amount of S-Metolachlor that leached through the soil (0.01 to 0.1%) nor its transformation rate (6.0 to 8.6%). However, it affected the degradation pathways with an increase of MET-OA relative to MET-ESA formed after OW amendment (28 to 54%) compared to the controls (8%). Concentration of S- Metolachlor and metabolites in the leachates of all treatments greatly exceeded the regulatory limit for groundwater intended for human consumption in Europe. These high concentrations were probably the consequence of preferential macropore flow. Colloids had comparable levels in the leachates after S-Metolachlor application. Dissolved organic carbon was also comparable in the controls, digestate, and sludge treatments but was 65% higher in the compost-amended cores. These results, along with a great variability among replicates inherent to experiments performed under realistic conditions, partly explain the limited impact of OW on the transport of S-Metolachlor.

A soil chemical quality index is designed for cacao production systems. It is based on worldwide scientific knowledge and built using data from three municipalities of Tolima department in Colombia. Fuzzy logic is used in a multicriteria decision making framework in two different ways. First, fuzzy sets are used to model an expert preference relation for each of the individual information sources to turn raw data into satisfaction degrees. Second, fuzzy rules are used to model the interaction between sources to aggregate the individual degrees into a global score. The whole framework is implemented as an open source software called GeoFIS. A part of the data was used for calibration, then the remaining data served as a validation set. The results were easy to analyze and in agreement with field observations. The output inferred by the fuzzy inference system was used as a target to learn the weights of classical numerical aggregation operators. Only the Choquet Integral proved to have a similar modeling ability, but its optimal tuning would have been difficult without learning.

The determination of the mechanisms and extent of soil mineral weathering can be challenging, and the caveats reside in 1) difficulty identifying minerals that are actually involved in weathering reactions, 2) non-stoichiometric release of cations during weathering processes due to coupled dissolution, precipitation and transformation reactions and, 3) impact of vegetation activity on elemental cycles in upper soil horizons. To better characterize mechanisms controlling mineral weathering in soils and trace the evolution of B concentration and isotope ratios during chemical weathering, quantitative mineralogical analyses were coupled to B isotopes in a group of minerals (biotite, muscovite, K-feldspar and albite). Samples were selected along an Alocrisol (Alumic Cambisol, WRB FAO) soil profile from the bedrock (at 130 cm depth) up to 20 cm depth, developed on granitic bedrock in the Breuil-Chenue forest (France). The samples consist of residual primary minerals associated with weathering secondary phases (vermiculite, kaolinite…) in varying proportions. The B isotopic compositions of the most pristine minerals span a very narrow range of values (around −31‰), whereas all secondary phases point to a much heavier value (around −16‰), regardless of mineralogy. Our results also show a mineral-dependent evolution of B concentration or isotopic composition as weathering progresses: no variation is observed during dissolution of K-feldspars; B behaves like a very mobile element in micas (biotite and muscovite), whereas it concentrates in weathered products derived from albite. However, rates of B concentrations and changes in isotopic compositions appear to be much faster than those inferred from mineralogy or major element concentrations determined by XRD and bulk chemical analyses, respectively. These results indicate that B is involved in very early weathering reactions and raises the question of its actual location in the structure of the various soil minerals as well as its pathway to solution.

International audience

Plant and soil 457(1-2), 293 - 320 (2020). doi:10.1007/s11104-020-04714-x, AimsThis study aimed to establish elemental profiles and to spatially resolve the elemental distribution in five New Caledonian woody Ni hyperaccumulator plant species (Geissois pruinosa var. pruinosa, Homalium francii, Hybanthus austrocaledonicus, Psychotria gabriellae, and Pycnandra acuminata) originating from the Cunoniaceae, Salicaceae, Violaceae, Rubiaceae, and Sapotaceae families respectively.MethodsUsing synchrotron-based micro-X-ray Fluorescence (��XRF) imaging of different plant tissues, from the roots to the shoots and reproductive organs, this study aimed to clarify how distribution patterns of nickel, and other physiologically relevant elements, differ between these species.ResultsThe results show that the tissue-level and cellular-level distribution of nickel in P. gabriellae, H. austrocaledonicus, G. pruinosa var. pruinosa, and H. francii conform with the majority of studied Ni hyperaccumulator plant species globally, including (temperate) herbaceous species, with localization mainly in epidermal cells and phloem bundles. However, P. acuminata has nickel-rich laticifers, which constitute an independent network of cells that is parallel to the vascular bundles and are the main sink for nickel.ConclusionsSynchrotron-based micro-X-ray Fluorescence (��XRF) is a powerful method for investigating how metal hyperaccumulation influences acquisition and spatial distribution of a wide range of elements. This non-invasive method enables investigation into the in vivo distribution of multiple elements and the structure and organisation of cells (e.g. laticifers)., Published by Springer Science + Business Media B.V, Dordrecht [u.a.]

Soil redox potential is an important factor affecting soil functioning. Yet, very few agronomy studies included soil redox potential in relation to soil processes. The objective of this study was to evaluate the spatial and temporal variation in soil redox potential and to determine the soil parameters affecting its variation. Soil redox potential, soil moisture, soil temperature, pH and bulk electrical conductivity were measured in upland rice fields during two growing seasons at six positions along an upland&ndash, lowland continuum, including two positions at the upland, two at the fringe and two at the lowlands in central C&ocirc, te d&rsquo, Ivoire (West Africa). The measurements were made at the following soil depths: 3, 8, 20 and 35 cm. Soil redox potential varied between 500 and 700 mV at the upland positions, 400 and 700 mV at the fringe positions and 100 and 750 mV at the lowland positions, and increased with soil depth. Variations in soil redox potential were driven by soil moisture, bulk electrical conductivity and soil organic carbon. We concluded that for proper interpretation of soil redox potential, sampling protocols should systematically include soil pH, moisture and bulk electrical conductivity measurements.

Made available in DSpace on 2020-12-12T01:29:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-11-10 Silpakorn University Ministry of Science and Technology of Thailand Agence Nationale de la Recherche Many studies have shown that introducing N2-fixing trees (e.g. Acacia mangium) in eucalypt plantations can increase soil N availability as a result of biological N2 fixation and faster N cycling. Some studies have also shown improved eucalypt P nutrition. However, the effects of N2-fixing trees on P cycling in tropical soils remain poorly understood and site-dependent. Our study aimed to assess the effects of planting A. mangium trees in areas managed over several decades with eucalypt plantations on soil organic P (Po) forms and low molecular weight organic acids (LMWOAs). Soil samples were collected from two tropical sites, one in Brazil and one in the Congo. Five different treatments were sampled at each site: monospecific acacia, monospecific eucalypt, below acacias in mixed-species, below eucalypts in mixed-species as well as native vegetation. Po forms and LMWOAs were identified in sodium hydroxide soil extracts using ion chromatography and relationships between these data and available P were determined. At both sites, the concentrations of most Po forms and LMWOAs were different between native ecosystems and monospecific eucalypt and acacia plots. Also, patterns of Po and LMWOAs were clearly separated, with glucose-6-P found mainly under acacia and phytate and oxalate mainly under eucalypt. Despite the strongest changes occurred at site with a higher N2 fixation and root development, acacia introduction was able to change the profile of organic P and LMWOAs in

Description du sujet. Le maraichage est particulièrement développé au sein de l’agriculture urbaine et périurbaine dans la région de Dakar. L’application répétée de matières organiques dans ces agrosystèmes engendre sur le long terme de forts apports d’éléments traces métalliques (ETM).Objectifs. L’objectif est de diagnostiquer la contamination en ETM de ces agrosystèmes.Méthode. Pour quatre sites, nous comparons les teneurs en Cu, Zn, Pb et Cd des parcelles cultivées depuis longtemps et des parcelles connexes non cultivées, dans les couches de sol travaillées et en profondeur. Résultats. Les deux types de sols présents (Arénosol et Fluvisol) sont caractérisés par des fonds pédogéochimiques en ETM significativement différents. Dans les couches de sol 0-20 et 20-40 cm des quatre sites étudiés, les teneurs en ETM sont significativement plus élevées (p, Diagnosis of periurban Dakar (Senegal) agrosystem contamination by trace elementsDescription of the subject. Urban and periurban market gardening is widespread in the Dakar area of Senegal. Repeated long-term application of organic matter results in high inputs of trace elements (TE).Objectives. The aim is to assess TE contamination in suburban agrosystems.Method. At four sites, we compared the Cu, Zn, Pb and Cd content in the surface layers and sublayers of plots cultivated over a long period with the content found in adjacent uncultivated plots.Results. The two prevailing soil types (Arenosol and Fluvisol) were characterized by significantly different background soil geochemical TE content. In the 0 – 20 and 20 – 40 cm soil layers at the four studied sites, TE content was significantly higher (p

Os solos com Terra Preta Arqueológica (TPA) são formados pela deposição contínua de resíduos orgânicos e mantêm sua fertilidade elevada mesmo após anos de cultivo. O objetivo do trabalho foi caracterizar e quantificar as formas de fósforo orgânico em sítios de Terra Preta Arqueológica (TPA), visando compreender a dinâmica desse elemento e contribuir com o desenvolvimento de práticas sustentáveis de uso do solo. Foram utilizadas amostras de 10 perfis com horizonte A antrópico (TPA) em Latossolos, Argissolos e Gleissolo, usando como referência solos adjacentes não antropogênicos, localizados na Amazônia Oriental. As amostras referentes aos horizontes A, horizonte de transição e B, foram submetidas ao fracionamento sequencial do P, em extrato ácido e básico e demais caracterizações físico-químicas. A fração de P em extrato ácido nos horizonte A1 e B predominou sobre as frações lábeis e solúvel em extrato básico em todas as áreas, apresentando os maiores percentuais observados na forma inorgânica. Verificou-se o aumento do conteúdo de fósforo orgânico lábil (Pol) no horizonte A1, com redução entre os horizontes A e B de 97,6%. O fósforo total (PT) apresentou teores significativamente elevados (6.778 mg dm-3) nos horizontes A de TPA em comparação com o mesmo horizonte no solo de referência (168 mg dm-3). Na fração total observou-se o predomínio do fósforo inorgânico sobre o fósforo orgânico, enquanto que nas frações lábeis ocorreu o inverso. Portanto, a maior parte do P total lábil está acumulado nas frações orgânicas do solo, representando uma forma ativa para o fornecimento do nutriente aos vegetais à medida que se mineraliza. Soils containing archaeological black earth (ABE) are formed by the continuous deposition of organic residue, and maintain their high fertility even after years of cultivation. The aim of this study was to characterise and quantify the forms of organic phosphorus in areas of archaeological black earth (ABE), with a view to understanding the dynamics of the element and contributing to the development of sustainable practices of land use. Samples of 10 profiles were used from Latosols, Argisols and Gleysols located in the eastern Amazon with an anthropogenic A-horizon (ABE), using adjacent, nonanthropogenic soils as reference. The samples relative to the A, transitional and B-horizons, were subjected to sequential fractionation of P in an acid base extraction, and to further physicochemical characterisation. The acid-extracted P fraction in the A1 and B-horizons predominated over the basic-extractant labile and soluble fractions in all areas, displaying the highest percentages for the inorganic form. An increase in the labile organic phosphorus content (Pol) was found in the A1-horizon, with a reduction between the A and B-horizons of 97.6%. The amount of total phosphorus (TP) was significantly higher (6,778 mg dm-3) in the A-horizons of the ABE in comparison with the soil in the reference area (168 mg dm-3). The predominance of inorganic phosphorus over organic phosphorus was found for the total fraction, while the opposite occurred with the labile fractions. Most of the total labile P is therefore accumulated in the organic fractions of the soil, and represents an active means of supplying the nutrient to plants as it mineralises.

Foram estudados os efeitos do uso do solo sobre a fertilidade, em Gleissolo sob três diferentes sistemas de manejo. As coletas foram feitas antes do período chuvoso nos seguintes sistemas de manejo: área cultivada com arroz (Oriza sativa L.) há aproximadamente 40 anos, com algumas interrupções ao longo deste período, com o cultivo algumas vezes mecanizado e uso de aração e gradagem; área sob pastagem de canarana erecta lisa (Echinochloa pyramidalis Hitch.), formada há cerca de 20 anos sem uso de adubações ou calagens; e área sob vegetação natural de floresta típica das áreas de várzea alta. As amostras de solo foram coletadas em dez pontos a partir de um transecto nas áreas, em quatro profundidades 0-10, 10-20, 20-30 e 30-40 cm. Os resultados demonstraram que o solo em condições naturais, de modo geral, apresentou atributos químicos que variaram de bons a muito bons, o que demonstra um grande potencial para o uso agrícola. O cultivo agrícola dos solos das várzeas do rio Guamá provocou uma redução da concentração de P e de K. O sistema de uso com pastagem apresentou maior sustentabilidade da fertilidade do que o sistema sob cultivo com arroz, visto que, além da melhoria das características químicas, a matéria orgânica elevou-se, também, em relação ao sistema natural. The effect of the use of the soil on the fertility has been studied, in Gleyssoil under three different management systems. Collections had been made before the rainy period in the following handling systems: rice (Oriza sativa L.) plantation area, cultivated for approximately 40 years, with some interruptions in during this period. Some times the culture was mechanized, with use of plowshare and harrow; pasture area with plantation of canarana (Echinochloa pyramidalis Hitch.), cultivated for 20 years, without the use of fertilizers; and lowland area with natural vegetation. The samples of soil were collected in ten points, set by using the transect methodology, to four depths 0-10, 10-20, 20-30 and 30-40 cm in each point. The results demonstrate that the soil under natural conditions, presented chemical characteristics which insure to the soil a high potential for the agricultural use. The agricultural culture of the lowland soil in the Guamá River provoked a reduction in the concentration of P and K. The soil usage system with pasture presented better sustainability on it fertility than the system with rice cultivation, beyond the improvement of the chemical characteristics and raise in the organic matter concentration, when related to the natural vegetation system.

A miniaturized Mossbauer spectrometer, adapted to the Earth’s conditions from the instrument developed for Mars space missions, has been used for the first time to study in situ variations with depth and transformations with time of iron minerals in a gleysol. The instrument is set into a PVC tube and can be moved up and down precisely (±1 mm) at the desired depth. Mossbauer spectra were obtained from 15 to 106 cm depth and repeated exactly at the same point at different times to follow mineralogical transformations with time. X-ray diffraction (XRD) and selective extraction techniques were performed on soil samples. The piezometric level of the water table was measured and the composition of the soil solution was monitored in situ and continuously, with a multiparametric and automatic probe. All the Mossbauer spectra obtained are characteristic of Fe(II)-Fe(III) green rust–fougerite, a natural mineral of the meixnerite group, that is, whose structural formula is: [Fe1 − xII Mgy FexIII (OH)2+2y]x+[xA, mH2O]x−, where x is the ratio Fe3+/Fetot. and A the intercalated anion. The name of fougerite has been formally approved by the Commission on New Minerals and Mineral Names of IMA (number 2003-057), on January 29, 2004. No other iron phases have been found by this way or by XRD. About 90% of total iron is extractible by dithionite-citrate-bicarbonate, and 60% by citratebicarbonate. In the horizons showing oximorphic properties that are in the upper part of the studied soil profile, x ratio in fougerite, deduced from Mossbauer spectra, is approximately 2/3. In the deepest horizons that show reductomorphic properties, x ratio is only 1/3. Fast mineralogical transformations were observed at well-defined points in soil, as evidenced by x ratio variations observed when Mossbauer spectra were acquired at different times at the same depth. Variations of the level of the water table and of pe and pH of the soil solution were simultaneously observed and could explain these mineralogical transformations. A ternary solid solution model previously proposed for OH-fougerite has been extended to chloride, sulphate, and carbonate green rusts to estimate the Gibbs free energies of formation of fougerite, providing for possible anions other than OH− in the interlayer and for Mg substitution. Soil solutions appear as largely oversaturated with respect to OH-fougerite, either oversaturated or undersaturated to “carbonate-fougerite” and “sulphate-fougerite”, and largely undersaturated with respect to “chloro-fougerite”. Fougerite forms most likely from oversaturated solutions by coprecipitation of Fe3+ with Fe2+ and Mg2+. Oxidation and reduction are driven by pH and pe variations, with both long timescale variations and short duration events. Exactly as synthetic green rusts are very reactive compounds in the laboratory, fougerite is thus a very reactive mineral and readily forms, dissolves, or evolves in soils.

A study was undertaken to investigate the effect of soil physical and chemical properties on nematodes associated with sugarcane. Principal component analysis (PCA) showed little or no change in the nematode community between nematicide treated and untreated plots or between sugarcane varieties. Analysis of the topsoil revealed very small differences in chemical elements between varieties. Soil of plots with the variety N16 had higher levels of Mg and Ca and lower levels of Fe. The study of soil characteristics of the topsoil and of the deeper layer revealed a heterogeneous situation alluding to the distinction of two zones over the area. However, the overall distribution of the entire nematode community, described by the factorial values of the PCA, was not related to the location of these two soil delimited zones. The coinertia analysis was then performed to identify the relationship between individual soil factors and individual species. These relationships were shown to be significant and concerned mainly the Mn level in the soil, the size of the plant–parasitic community and the abundance of Helicotylenchus dihystera and Xiphinema elongatum . All three decreased as the Mn content increased. To a lesser extent, pH and Na were positively associated with the numbers of free-living nematodes.

Nickel speciation in a nickel hyperaccumulating plant ( Sebertia acuminata ) and its associated soil of southern New Caledonia was studied using various analytical methods. The soil is formed of iron oxides (goethite, hematite), which contain almost all the nickel. The available nickel is probably linked to the organic matter in the litter. Sebertia acuminata , acts as a nickel pump, and concentrates the metal in its leaves. It partitions nickel and silica; nickel is concentrated in the cells (probably in the vacuoles) as organometallic complexes, whereas silica forms the framework of the cells, and the phytolithes. A thorough study of these plants seems essential in order to define the soil–plant relations, and to propose appropriate ways for ecological restoration. To cite this article: N. Perrier et al., C. R. Geoscience 336 (2004).

Survival, biomass production, nutrient use and fertility of soil were examined in experimental stands of 10-year-old N-fixing indigenous Acacia nilotica (L.) Del. (eight provenances), A. senegal (L.) Willd. (one provenance), Acacia tortilis (Forsskal) Hayne (six provenances), Acacia raddiana syn A. tortilis (Forssk.) Hayne ssp. raddiana (Savi) Brenan (three provenances) and exotic N-fixing A. holosericea A. Cunn. ex G. Don (one provenance), A. cowleana Tate (one provenance), Acacia aneura F. Muell. ex Benth. (twelve provenances), Prosopis juliflora (Sw.) DC. (one naturalised provenance), Prosopis cineraria (L.) Druce (five provenances) and P. chilensis (Molina) Stuntz (two provenances) growing on a coastal site in semi-arid Senegal. Similar data were obtained for the non-N-fixing fast-growing exotic species Azadirachta indica Adr. Juss. and Eucalyptus camaldulensis Dehnh. of the same age that were growing on adjacent plots. P. juliflora produced more biomass than the other species and showed the greatest potential for use as a multipurpose tree. A. aneura showed the greatest potential for fodder production and despite its small stature, it ranked second for biomass among the N-fixing species. Of the indigenous species, A. nilotica was the most efficient user of non-renewable elements in biomass production. A. raddiana seemed profligate in its consumption of both N and P in wood production. E. camaldulensis was efficient in its use of N in wood but its wood contained large concentrations of P and K. A. aneura, P. juliflora and A. nilotica had the smallest concentrations of P in wood. A. raddiana and A. indica contained large concentrations of K in their wood in contrast to A. aneura and A. nilotica which were the most efficient users of K in wood production. There were few significant differences in fertility in soils beneath the differing tree species. Nevertheless, plots containing P. juliflora and P. cineraria tended to be the most fertile. Soil beneath A. indica was more fertile than soil beneath some N-fixing species. The extent of removal of plant nutrients in biomass suggests that without inputs of nutrient elements, harvest of wood and foliage is unlikely to be sustainable at the measured rate of production for more than two tree rotations of 10 years duration.

International audience; The soil science community is facing a growing demand of regional, continental, and worldwide databases in order to monitor the status of the soil. However, the availability of such data is very scarce. Cost-effective tools to measure soil properties for large areas (e.g., Europe) are required. Soil spectroscopy has shown to be a fast, cost-effective, environmental-friendly, nondestructive, reproducible, and repeatable analytical technique. The main aim of this paper is to describe the state of the art of soil spectroscopy as well as its potential to facilitating soil monitoring. The factors constraining the application of soil spectroscopy as an alternative to traditional laboratory analyses, together with the limits of the technique, are addressed. The paper also highlights that the widespread use of spectroscopy to monitor the status of the soil should be encouraged by (1) the creation of a standard for the collection of laboratory soil spectra, to promote the sharing of spectral libraries, and (2) the scanning of existing soil archives, reducing the need for costly sampling campaigns. Finally, routine soil analysis using soil spectroscopy would be beneficial for the end users by a reduction in analytical costs, and an increased comparability of results between laboratories. This ambitious project will materialize only through (1) the establishment of local and regional partnerships among existent institutions able to generate the necessary technical competence, and (2) the support of international organizations. The Food and Agriculture Organization (FAO) of United Nations and the Joint Research Centre of the European Commission are well placed to promote the use of laboratory and field spectrometers for monitoring the state of soils.

Differences in rates of infestation of root-knot nematode (Meloidogyne spp.) populations by the endospore-forming bacterium Pasteuria penetrans were not entirely due to inter/intra-specific variability of the organisms. Soil conditions, especially texture and chemical characteristics, are also involved. Focusing studies on vegetable crops, interactions between the occurrence of Meloidogyne spp. juveniles encumbered with spores of P. penetrans and some physico-chemical soil characteristics were analysed both between regions (West Africa, e.g. Burkina Faso and Senegal; South America, e.g. Ecuador; the Caribbean, e.g. Trinidad and Tobago; and Mediterranean Europe, e.g. Crete) and within Ecuador, Burkina Faso and Senegal. In Ecuador (clay or silty-clay soils), the mean proportion of infested juveniles was high (41.9%). In the sandiest soils, as in Senegal, there were very few infested juveniles (4.7%). In Crete, Burkina Faso, and Trinidad and Tobago, where the soils are siltier, the mean proportions of infested juveniles range between 14 and 24.4%. Multivariate analysis performed on the data from Senegal and Burkina Faso revealed that a significant increase of the mean clay content (1.4 and 10.5%, respectively) improved the mean proportions of infested juveniles (from 1.6 to 42.2% and from 10.7 to 79.4%, respectively). Influences of the soil texture and structure on the availability of the spores of P. penetrans to infest the juveniles of Meloidogyne spp. are discussed.

International audience

Within tree communities, the differential use of soil N mineral resources, a key factor in ecosystem functioning, may reflect functional complementarity, a major mechanism that could explain species coexistence in tropical rainforests. Eperua falcata and Dicorynia guianensis, two abundant species cooccurring in rainforests of French Guiana, were chosen as representative of two functional groups with complementary N uptake strategies (contrasting leaf δ15N signatures related to the δ15N of their soil N source, NO3- or NH4+). The objectives were to investigate if these strategies occurred under contrasted soil N resources in sites with distinct geological substrates representative of the coastal rainforests. Results showed that species displayed contrasting leaf δ15N signatures on both substrates, confirming their complementary N uptake strategy. Consequently, their leaf 15N can be used to trace the presence of inorganic N-forms in soils (NH4+ and NO3-) and thus to indicate the capacity of soils to provide each of these two N sources to the plant community.

Pour évaluer les différents changements d’état ou les modifications de fonctionnement du milieu rural induits par les perturbations naturelles, et surtout par les interventions de l’homme, l’observateur a le plus souvent recours à la mesure ou à l’évaluation de simples paramètres, attributs et caractéristiques du système écologique étudié, mais aussi à l’utilisation d’indices complexes calculés à partir de paramètres élémentaires. Cet ensemble est désigné sous le vocable général d’indicateurs...

The aim of the present study was to examine the interactions between an endogeic earthworm species, Metaphire posthuma , and purely mineral (control) or mineral plus organic (compost vs. vermicompost) amendments in terms of soil chemical properties and plant growth and yield. A one-year experiment was carried out in a greenhouse with a maize–tomato–maize cycle. Compost and vermicompost modified soil chemical properties leading to higher C and N, higher pH and CEC, and lower available P, NH 4 + and NO 3 − than in the control. Although no significant difference in plant growth was observed for the first maize planting, tomato and maize growth were then highest for the mineral and vermicompost treatments and lowest for compost. Overall plant yields were always highest in mineral fertilizer alone and lowest for the compost treatments. The application of vermicompost led to a similar yield as the control treatment for the first maize planting. However, its beneficial influence decreased during the experiment until it was similar to that of the compost treatment. The presence of earthworms reduced the C content in soil mixed with compost and vermicompost but only influenced plant growth and yield in the compost treatment. The effect of earthworms was initially null (i.e. for the first maize crop), positive (i.e. for tomato planting) and finally negative (i.e. for the second maize planting), thereby underpinning the complexity of the interactions between the quality of organic matter in soil, earthworm activity and plant growth.

International audience; Plant species (exotic invasive vs native non-invasive) colonization pattern and the relation with the soil nutrient availability and AM fungi abundance, was investigated. Soil samples were collected from two sites: one invaded by the exotic plant. Amaranthus viridis, and one uninvaded site for chemical and AM propagules density analyses. Additionally, we grew five Sahelian Acacia species in soil from the two sites, sterilized or not, to test the involvement of soil biota in the invasion process. While nutrient availability was significantly higher in soil samples from the invaded sites, a drastic reduction in AM fungal community density, was observed. Moreover, Acacia seedlings' growth was severely reduced in soils invaded by Amaranthus and this effect was similar to that of sterilized soil of both origins. The observed growth inhibition was accompanied by reduction of AM colonization and nodulation of the roots. Finally, the influence of soil chemistry and AM symbiosis on exotic plants' invasion processes is discussed. (C) 2011 Elsevier Ltd. All rights reserved.

Each year the area of fast-growing tree plantations in the world expands by around one million hectares. Concerns are rising regarding their influence on soil fertility and water resources. This thesis, as part of a project developed at the University of São Paulo, aims at studying the soil matrix and solution during the first two years of growth of an Eucalyptus Grandis stand to identify the drivers of the chemistry of the soil solution, quantify the water and nutrient fluxes leaving the ecosystem by deep drainage, and prepare reactive transport modeling using the MIN3P model. It is shown that (i) Eucalyptus trees took up large amounts of water starting from six months after planting, so that the water drainage at a depth of 3 m was largely reduced, (ii) almost no nutrient was leached below a depth of 3 m, (iii) part of the fertilizers was taken up by the Eucalyptus trees without appearing in soil solution, (iv) following clear cutting and fertilizing, large amounts of nutrients were released in the upper soil layers and leached down to a depth of 1 m (65-100 kg ha-1 of N-NO3) : acidification occurred in the upper soil layers but in such ferralsols, Al reserve and buffering capacity are still large, (v) S released by the fertilizers increased Ca, Mg and P mobilities, and decreased the H and Al release in soil solution, (vi) large quantities of S released by the fertilizers were adsorbed on the soil constituents, if this sulphate happens to be desorbed, greater soil acidification is to be expected. It is suggested that the amount of N brought by the fertilizers can be reduced without altering the stand productivity.; Chaque année, les plantations de ligneux à croissance rapide augmentent de près d'un million d'hectares dans le monde, menaçant selon certains la fertilité des sols et les ressources hydriques. Cette thèse s'attache, au sein d'un projet en cours à l'Université de São Paulo, à étudier le sol et la solution du sol pendant les deux premières années de croissance d'une plantation d'Eucalyptus grandis afin d'identifier les processus gouvernant la chimie de la solution du sol, de quantifier les flux d'eau et d'éléments minéraux sortant de l'écosystème par drainage profond, et de préparer la modélisation des transferts réactifs par le modèle MIN3P. On observe que (i) dès six mois, les Eucalyptus prélèvent de grandes quantités d'eau : le drainage à 3 m de profondeur en est largement réduit, (ii) les flux d'éléments minéraux à 3m sont pratiquement nuls, (iii) les éléments minéraux apportés par fertilisation sont en partie prélevés par les arbres sans apparaître dans la solution du sol, (iv) après la coupe rase et les fertilisations, les éléments minéraux sont libérés en quantité dans les horizons supérieurs du sol et lixiviés jusqu'à 1 m (65-100 kg ha-1 de N-NO3), des processus d'acidification apparaissent mais les réserves d'aluminium et le pouvoir tampon de ces ferralsols restent élevés, (v) le soufre libéré par les fertilisants augmente la mobilité de Ca, Mg et P et réduit la libération d'H et d'Al dans la solution, (vi) ce soufre se retrouve largement adsorbé sur les constituants du sol : son éventuelle désorption serait synonyme d'acidification. La fertilisation azotée de la plantation pourrait probablement être réduite sans en altérer la productivité.

Each year the area of fast-growing tree plantations in the world expands by around one million hectares. Concerns are rising regarding their influence on soil fertility and water resources. This thesis, as part of a project developed at the University of São Paulo, aims at studying the soil matrix and solution during the first two years of growth of an Eucalyptus Grandis stand to identify the drivers of the chemistry of the soil solution, quantify the water and nutrient fluxes leaving the ecosystem by deep drainage, and prepare reactive transport modeling using the MIN3P model. It is shown that (i) Eucalyptus trees took up large amounts of water starting from six months after planting, so that the water drainage at a depth of 3 m was largely reduced, (ii) almost no nutrient was leached below a depth of 3 m, (iii) part of the fertilizers was taken up by the Eucalyptus trees without appearing in soil solution, (iv) following clear cutting and fertilizing, large amounts of nutrients were released in the upper soil layers and leached down to a depth of 1 m (65-100 kg ha-1 of N-NO3) : acidification occurred in the upper soil layers but in such ferralsols, Al reserve and buffering capacity are still large, (v) S released by the fertilizers increased Ca, Mg and P mobilities, and decreased the H and Al release in soil solution, (vi) large quantities of S released by the fertilizers were adsorbed on the soil constituents, if this sulphate happens to be desorbed, greater soil acidification is to be expected. It is suggested that the amount of N brought by the fertilizers can be reduced without altering the stand productivity., Chaque année, les plantations de ligneux à croissance rapide augmentent de près d'un million d'hectares dans le monde, menaçant selon certains la fertilité des sols et les ressources hydriques. Cette thèse s'attache, au sein d'un projet en cours à l'Université de São Paulo, à étudier le sol et la solution du sol pendant les deux premières années de croissance d'une plantation d'Eucalyptus grandis afin d'identifier les processus gouvernant la chimie de la solution du sol, de quantifier les flux d'eau et d'éléments minéraux sortant de l'écosystème par drainage profond, et de préparer la modélisation des transferts réactifs par le modèle MIN3P. On observe que (i) dès six mois, les Eucalyptus prélèvent de grandes quantités d'eau : le drainage à 3 m de profondeur en est largement réduit, (ii) les flux d'éléments minéraux à 3m sont pratiquement nuls, (iii) les éléments minéraux apportés par fertilisation sont en partie prélevés par les arbres sans apparaître dans la solution du sol, (iv) après la coupe rase et les fertilisations, les éléments minéraux sont libérés en quantité dans les horizons supérieurs du sol et lixiviés jusqu'à 1 m (65-100 kg ha-1 de N-NO3), des processus d'acidification apparaissent mais les réserves d'aluminium et le pouvoir tampon de ces ferralsols restent élevés, (v) le soufre libéré par les fertilisants augmente la mobilité de Ca, Mg et P et réduit la libération d'H et d'Al dans la solution, (vi) ce soufre se retrouve largement adsorbé sur les constituants du sol : son éventuelle désorption serait synonyme d'acidification. La fertilisation azotée de la plantation pourrait probablement être réduite sans en altérer la productivité.

As soil engineers, earthworms and ants play major roles in soil functioning, especially in modifying soil physical and chemical properties. This study was conducted in a very constraining environment, i.e., paddy fields which have anoxic conditions (approximately four months per year), and which are affected by soil salinisation during the dry period (approximately eight months per year). This study points out that despite those very adverse conditions, soil invertebrates must be taken into account in the dynamic of soil organic and mineral properties in paddy fields. The effects of one earthworm species, Glyphodrillus sp., and an ant species, Epelysidris sp., on soil physical and chemical properties were determined through elemental soil physical and chemical properties (texture, pH, conductivity, C and N contents) and near infrared reflectance spectroscopy (NIRS) in order to evaluate their ability to influence soil organic matter quality. PCA processed with NIRS data clearly showed that biogenic structures (ant sheetings and earthworm casts) were separated from the control surrounding soil. Earthworms and ants affected differently soil properties. Glyphodrillus sp. increased the SOM content and decreased the pH on the surface of the soil. These effects were attributed to an increase in fine particle content (clay). Conversely, Epelysidris sp. only increased the content of coarse particles (sand) and did not influence either soil pH or SOM content. Soil conductivity was found to be very variable but was not significantly affected by soil invertebrates. These results show the potential of soil macro-fauna to create heterogeneity at small spatial scale and to modify the quality of surface soils even under adverse conditions like saline paddy fields.

Invertebrates play significant, but largely ignored, roles in the delivery of ecosystem services by soils at plot and landscape scales. They participate actively in the interactions that develop in soil among physical, chemical and biological processes. We show that soils have all the attributes of self-organized systems as proposed by Perry (Trends Ecol. Evol. 10 (1995) 241) and detail the scales at which invertebrates operate and the different kinds of ecosystem engineering that they develop. This comprehensive analysis of invertebrate activities shows that they may be the best possible indicators of soil quality. They should also be considered as a resource that needs to be properly managed to enhance ecosystem services provided by agro-ecosystems. © 2006 Published by Elsevier Masson SAS.

Dans les montagnes du nord du Vietnam, le riz pluvial conserve une place importante, mais les rendements obtenus sont extrêmement faibles et variables. L'analyse de la variabilité des rendements obtenus chez les agriculteurs a permis d'identifier les principales contraintes à la production rizicole. Elle a été menée dans un village représentatif de la diversité des conditions biophysiques de la province de BacKan. La variabilité des rendements en riz pluvial entre les parcelles est expliquée en premier lieu par le type de végétation précédant la culture de riz et le nombre de saisons culturales consécutives. Au sein de chaque parcelle, la variabilité de la culture est largement expliquée par la structure (porosité, compaction, densité) et, partiellement, par les caractéristiques chimiques et l'activité biologique des sols. Tous ces facteurs sont, à des degrés divers, des indicateurs d'état de la fertilité\\dégradation du sol. La régénération de la forêt et du sol est contrainte par l'allongement des périodes de culture lié à une forte pression démographique ainsi que par le pâturage des jachères par les buffles. La dégradation du sol est accentuée par l'érosion qui fait suite à la déforestation et au brûlis sur les terres de pentes. En conséquence, une mauvaise structure du sol, de fortes pertes par ruissellement et un enracinement superficiel du riz sont responsables d'une mauvaise utilisation de l'eau. L'infestation par les mauvaises herbes est, comme partout, une autre contrainte majeure à la riziculture pluviale. Ces deux aspects ont été placés en priorité pour la recherche, ce qui a permis de développer des alternatives à ces systèmes d'abattis-brûlis.