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Abstract: Chlordecone is a persistent organochlorine insecticide that, even decades after its ban, poses a threat to the environment and human health. Nevertheless, its environmental fate in soils has scarcely been investigated, and elementary data on its degradation and behaviour in soil are lacking. The mineralisation and sorption of chlordecone and the formation of possible metabolites were evaluated in a tropical agricultural andosol. Soil microcosms with two different soil horizons (S-A and S-B) were incubated for 215days with 14C-chlordecone. At five different times (1, 33, 88, 150 and 215days) the extractability of 14C-chlordecone was analysed. Mineralisation was monitored using 14CO2 traps of NaOH. The appearance of metabolites was studied using thin layer and gas chromatography techniques. At the end of the experiment, the water soluble 14C-activity was 2% of the remaining 14C-chlordecone for S-A and 8% for S-B. Only 12% of the remaining activity was non extractable and more than 80% remained extractable with organic solvents. For the first time to our knowledge, a significant mineralisation of chlordecone was measured in a microcosm under aerobic conditions (4.9% for S-A and 3.2% for S-B of the initial 14C-activity). The drastically lower emission of 14CO2 in sterilised microcosms indicated the biological origin of chlordecone mineralisation in the non-sterilised microcosms. No metabolites could be detected in the soil extracts. The mineralisation rate of chlordecone decreased by one order of magnitude throughout the incubation period. Thus, the chlordecone content in the soil remained large. This study confirms the existence of chlordecone degrading organisms in a tropical andosol. The reasons why their activity is restricted should be elucidated to allow the development of bioremediation approaches. Possible reasons are a heterogeneous distribution a chlordecone between sub-compartments with different microbial activities or a degradation of chlordecone by co-metabolic processes controlled by a limited supply of nutrients. [Copyright &y& Elsevier]

Coarse woody debris (CWD) is involved in important forest ecosystem functions and processes, e.g., habitat provision, water retention, and organic matter decomposition. However, a quantitative, CWD-produced soil organic carbon (SOC) imprint has not yet been detected, possibly due to lack of free adsorption sites on soil minerals. To circumvent this potential constraint, we selected plots with and without CWD in a beech ( Fagus sylvatica L.) primeval forest in the West Carpathian volcanic range (Slovakia). Local andic soil contains abundant allophane and amorphous Fe-compounds as important SOC binding agents. The C concentration in the fine earth of sampled soils was determined by the dry combustion method. We established that organic carbon concentration decreased with depth from 0.20 kg kg (0.0-0.3 m) to 0.11 kg kg (0.3-0.5 m) in soil with CWD and from 0.13 kg kg (0.0-0.3 m) to 0.07 kg kg (0.3-0.5 m) in soil without CWD. The respective average differences in soil organic carbon concentration (0.07 kg kg) and stock (15.84 kg m) between the two series of plots within the upper 0.3 m were significant according to the t test ( P < 0.05 or P < 0.01, respectively). Also, corresponding differences within the 0.3-0.5 m layer (0.04 kg kg and 5.51 kg m) were significant ( P < 0.05, P < 0.001). Our results represent the first indication that CWD-produced SOC imprint may reach deeper than just a few centimeters in soils featuring high adsorption capacity, such as Andosols. [ABSTRACT FROM AUTHOR]

Andosols comprise one of the most important soil groups for agricultural activities in Japan because they cover about 46.5% of arable upland fields. In this soil group, available phosphorus (P) is accumulated by application of excessive fertilizer, but little is known about the influence of increasing P availability on microbial community diversity at large scales. We collected soil samples from 9 agro-geographical sites with Andosol soils across an available P gradient (2048.1-59.1 mg P2O5·kg−1) to examine the influence of P availability on the fungal community diversity. We used polymerase chain reaction - denaturing gradient gel electrophoresis to analyze the fungal communities based on 18S rRNA genes. Statistical analyses revealed a high negative correlation between available P and fungal diversity ( H′). Fungal diversity across all sites exhibited a significant hump-shaped relationship with available P ( R2 = 0.38, P < 0.001). In addition, the composition of the fungal community was strongly correlated with the available P gradient. The ribotype F6, which was positively correlated with available P, was closely related to Mortierella. The results show that both the diversity and the composition of the fungal community were influenced by available P concentrations in Andosols, at a large scale. This represents an important step toward understanding the processes responsible for the maintenance of fungal diversity in Andosolic soils. [ABSTRACT FROM AUTHOR]

Abstract: The isotopic exchange kinetic (IEK) method allows assessing the rate of orthophosphate ions (Pi) exchange between the solid phase and the solution of the soil with time. However, two challenges have to be tackled when using this technique in soils with a very low water extractable Pi concentration ( C P ) and with a high sorbing capacity for Pi. The first is that current colorimetric methods do not allow quantifying Pi concentrations lower than 10μgP L−1. While the second challenge is that a significant fractionation between P isotopes may occur in the soil solution system in the presence of soils with high Pi sorption capacity. We assessed here: i) whether concentrating the blue phosphomolybdate complex (BPMC) in hexanol prior to its measurement would allow to lower the detection and quantification limits of Pi, ii) whether a significant isotopic fractionation between 32Pi and 33Pi could occur during IEK experiments conducted in the presence of high Pi sorbing substrates (e.g., pure goethite or Malagasy soils) and iii) whether the IEK method when used in conjunction with the hexanol concentration of the BPMC to measure C P would detect changes in Pi isotopic exchangeability in a ferralsol cropped with upland rice following the input of manure or water soluble fertilizer. The detection and quantification limits of the BPMC concentrated by hexanol were 0.3 and 0.8μgPL−1, respectively, using a cell of 10cm length for the colorimetric measurement. The IEK conducted on Pi amended goethite and on Malagasy soils with 32Pi and 33Pi did not show any systematic isotopic fractionation between both isotopes, suggesting that in these soils 31Pi and 32Pi or 33Pi have a similar behavior during isotopic exchange. The analysis of the soils sampled in the field experiment showed a significant increase in the amount of Pi isotopically exchangeable after 1min only after the application of water soluble P. This increase was paralleled by increases in rice yield and P export by grains demonstrating an increased P availability in this treatment. In conclusion, the IEK method can be used in low P and high Pi sorbing soils as the hexanol concentration method allows measuring very low C P and as the different P isotopes have a similar behavior in the soil/solution system. The IEK experiments conducted in the presence of goethite, however, point out to the necessity of taking into account the dispersion of particles for a proper interpretation of the isotopic data. [Copyright &y& Elsevier]

Abstract: Microbial biomass carbon (MBC) and water-extractable organic carbon (WOC) – as sensitive and important parameters for soil fertility and C turnover – are strongly affected by land-use changes all over the world. These effects are particularly distinct upon conversion of natural to agricultural ecosystems due to very fast carbon (C) and nutrient cycles and high vulnerability, especially in the tropics. The objective of this study was to use the unique advantage of Mt. Kilimanjaro – altitudinal gradient leading to different tropical ecosystems but developed all on the same soil parent material – to investigate the effects of land-use change and elevation on MBC and WOC contents during a transition phase from dry to wet season. Down to a soil depth of 50cm, we compared MBC and WOC contents of 2 natural (Ocotea and Podocarpus forest), 3 seminatural (lower montane forest, grassland, savannah), 1 sustainably used (homegarden) and 2 intensively used (maize field, coffee plantation) ecosystems on an elevation gradient from 950 to 2850m a.s.l. Independent of land-use, both MBC and WOC strongly increased with elevation on Mt. Kilimanjaro corresponding to ecosystem productivity and biodiversity. Through the agricultural use of ecosystems MBC and WOC contents decreased – especially in surface layers – on average by 765mgkg−1 for MBC and 916mgkg−1 for WOC, compared to the respective natural ecosystems. The decrease with depth was highest for forests>grasslands>agroecosystems and also was positively correlated with elevation. We conclude that MBC and WOC contents in soils of Mt. Kilimanjaro ecosystems are highly sensitive to land-use changes, especially in topsoil. The MBC and WOC contents were considerably reduced even in sustainable agricultural systems. Since MBC and WOC are very fast reacting and sensitive C pools, we expect a decrease in other soil C pools accompanied by a strong decrease in fertility and productivity due to changes in land use from natural to agricultural ecosystems. [Copyright &y& Elsevier]

Nitrogen (N) fertilizers applied on agricultural fields are an important source of nitrous oxide (N2O). The use of coated fertilizer is known to mitigate fertilizer derived N2O emissions; however, according to previous studies, the effectiveness of coated fertilizer as a mitigation option varies depending on the soil types. We hypothesized that this variability was due to the contribution of nitrification and denitrification to N2O emissions depending on the soil and fertilizer types. Two contrasting Japanese soils, Andosol and Fluvisol, were repacked in columns and treated with either urea or coated urea, and soil N2O emissions were monitored for 30 days at 55% water-filled pore space under laboratory conditions. Contribution of nitrification and denitrification to N2O emissions were determined for soils without fertilizer application and for soils at 7 and 28 days after urea or coated urea application, using a15N tracer technique. The results imply that >60% and >80% of N2O emissions in Andosol were derived from nitrification at 7 and 28 days after application, respectively, regardless of the fertilizer types used. In Fluvisol, nitrification-derived N2O contributed 59 ± 55% and 82 ± 8% of soil N2O emissions at 7 and 28 days after application, respectively, when coated urea was applied, whereas the domination of nitrification-derived N2O to soil N2O emissions was not observed when urea was applied to Fluvisol. Soil ammonium () was depleted at 4 weeks after fertilizer application in Andosol, but was still available in Fluvisol at the same period, regardless of fertilizer types used. In Andosol, nitrification-derived N2O emissions increased when theavailability was high but this was not the case for Fluvisol, when urea was applied, and we believe that the response of nitrifying microbes to the amount of availablecontrols the differing trend of N2O emissions after the application of urea or of coated urea. [ABSTRACT FROM PUBLISHER]

In a pot experiment using a strongly P-fixing Andosol from Nicaragua, the effects of sugarcane-filter cake application on the growth of white mustard ( Sinapis alba L.) were compared with those of 13C-labeled pea residues. The application of pea residues led to a 50% increase and the application of filter cake to a 30% decrease in soil organic matter-derived microbial biomass C compared with the control. In contrast, the application of filter cake resulted in a four times higher content of substrate-derived microbial biomass C than that of pea residues. The application of organic substrates generally increased microbial biomass N. Mustard growth led to significant increases in microbial biomass P in the control, but also in the organic-amendment treatments, which always resulted in decreased microbial biomass C : P ratios. Mustard growth also led to increased contents of Bray-1-extractable P, but this increase was only significant in the filter cake treatment. The application of pea residues had no effect on the yield of shoot C, but a positive effect on the yield of root C in comparison with the nonamended control. In contrast, the application of filter cake significantly depressed yields of shoot C and root C, due to N immobilization, presumably due to the high concentration of lignin. [ABSTRACT FROM AUTHOR]

Volcanic ash soils along the western edge of the Omiya tableland, Japan, are covered with thick anthropogenic soil horizons. The formation of anthropogenic soil horizons occurs because of the soil dressing practice known as “Dorotsuke,” where alluvial soil materials are deposited on fields and mixed with volcanic ash topsoil by tillage over the years. To clarify the chronology of this anthropedogenesis, carbon-14 (14C) age profiles were estimated using humic acid fractions from three pedons: an anthropogenic soil, an undressed Andosol, and a Fluvisol. Soil charcoal fragments were also dated to estimate maximum burial age. Charcoal fragments displayed vertically random age distributions, indicating that the fragments may have had multiple origins. However, the age of charcoal in the lower part of the anthropogenic soil horizons indicated that the initiation of anthropedogenesis occurred later than the late 13th century. The 14C age profile of humic acid in the Andosol exhibited little variation in age with depth in the subsoil. The 14C age profile of humic acid in the Fluvisol suggested that the humic acid fraction included allochthonous old carbon (C), although the soil itself had been formed from recent sediments. The 14C age profile of humic acid in the anthropogenic soil showed features of its two component soils. The 14C ages in the volcanic ash subsoil matched with those in the Andosol, whereas the ages increased in the anthropogenic soil horizons because of supplementation with old C from alluvial soil materials. However, the peak 14C ages occurred in the lower part of the anthropogenic horizons, whereas the middle part on the peak position displayed a gradual age-depth gradient. This feature was interpreted as a sign of 14C activity equilibrium throughout anthropedogenesis. On the basis of this postulated 14C activity equilibrium, the linear age-depth gradient at the peak position was derived from differences in burial time, and burial ages were calculated by estimating steady-state 14C. The calculated ages were lower than the charcoal ages. These age estimates suggest that anthropedogenesis was initiated in the Middle Ages and reached an intermediate stage before or during the first half of the Edo period. [ABSTRACT FROM PUBLISHER]

Here we have investigated the emission of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from long- and short-term organic farming Andosols in Matsumoto city of Nagano, in central Japan. We focus on three upland plots in Matsumoto, distinguished by how long they had each experienced continuous organic farming (OF)—in these three cases, since 1971, 2009, and 2010 (plots hereafter termed M39-OF, M1-OF, and M1F-OF, respectively). Since 2001, in M39-OF, mainly rye (Secale cereale L., as green manure) and soybeans [Glycine max (L.) Merril, as crop] were cultivated, in winter and summer respectively, without tillage, other fertilizers and agro-chemicals. In contrast, from 2001 to 2008 in M1-OF, and from 2001 to 2009 in M1F-OF, these plots underwent conventional farming of some vegetables with tillage, fertilizer and agro-chemicals. Soils sampled from M39-OF and M1-OF in August 2009 were incubated for 4 weeks in darkness at 25°C. During these 4 weeks, M39-OF emitted 8.0 times more CO2 and 274 times more N2O than M1-OF. Less than 2 µg carbon (C) kg–1 dry soil of CH4 was emitted from both soils. From February 2010 until January 2011, CO2, CH4, and N2O emission rates of M39-OF and M1F-OF were measured almost monthly, using a closed-chamber method. Annual CO2, CH4, and N2O emissions were 317, –1.7, and 27 g CO2-C equivalent m–2 in M39-OF, and 138, –0.2, and 21 g CO2-C equivalent m–2 in M1F-OF, respectively. The rye yield in M39-OF was 334 g C m–2. Soybeans in M39-OF and M1F-OF yielded 290 and 286 g C m–2, and withdrew 230 and 224 g C m–2, respectively. Greenhouse gas (GHG) balance was calculated at –52 and 97 g CO2-C equivalent m–2 in M39-OF and M1F-OF, respectively. Negative GHG balance indicated that M39-OF was acting as a GHG sink, with higher CH4 absorption than M1F-OF. Further, this beneficial function for global warming was thought to be based on its cultivation system, which had included green manure application since 2001. The difference in gas exchange between incubation and field experiments was considered a reason for the difference in N2O emission between incubation and field experiments. [ABSTRACT FROM PUBLISHER]

The lack of a universal method to extract RNA from soil hinders the progress of studies related to nitrification in soil, which is an important step in the nitrogen cycle. It is particularly difficult to extract RNA from certain types of soils such as Andosols (volcanic ash soils), which is the dominant agricultural soil in Japan, because of RNA adsorption by soil. To obtain RNA from these challenging soils to study the bacteria involved in nitrification, we developed a soil RNA extraction method for gene expression analysis. Autoclaved casein was added to an RNA extraction buffer to recover RNA from soil, and high-quality RNA was successfully extracted from eight types of agricultural soils that were significantly different in their physicochemical characteristics. To detect bacterial ammonia monooxygenase subunit A gene ( amoA) transcripts, bacterial genomic DNA and messenger RNA were co-extracted from two different types of Andosols during incubation with ammonium sulfate. Polymerase chain reaction-denaturing gradient gel electrophoresis and reverse transcription polymerase chain reaction-denaturing gradient gel electrophoresis analyses of amoA in soil microcosms revealed that only few amoA, which had the highest similarities to those in Nitrosospira multiformis, were expressed in these soils after treatment with ammonium sulfate, although multiple amoA genes were present in the soil microcosms examined. [ABSTRACT FROM AUTHOR]

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Abstract: The Orravatnsrustir palsa site, located north of the Hofsjokull glacier in Central Iceland, has well developed palsas located in a valley-like depression at 710–715m a.s.l. and stands in remarkable contrast to the surrounding desert-like highland plateau. The purpose of this paper is to give an overview of the Orravatnsrustir palsa site, geographic distribution and geomorphic statistics related to size and permafrost thicknesses of the palsas, including recent changes. Icelandic palsas exhibit characteristics of both organic palsas and lithalsa (frozen mineral soil). They are subjected to intense aeolian deposition of volcanic materials. The palsas are often 40–200cm high, with a 40–80cm thick active layer and permafrost reaching more than 5m depth. Measurements of the size of the palsas and the thickness of the active layer which started in 2001 indicate that their size is decreasing and the thickness of the active layer is increasing. These results are in agreement with the general warming trend which has occurred in Iceland during the last decade. [Copyright &y& Elsevier]

Abstract: Soil structure dependent properties are subject to temporal changes as a consequence of tillage and environmental factors. These changes are well documented in soils with bulk densities >1Mgm−3; however, no major studies have been carried out in soils with extremely low densities, such as those normally presented by Andosols. Thus, in order to study the temporal dynamics of a volcanic ash soil''s physical properties, this study aimed to assess the impact of tillage on soil structure-dependent properties and their development throughout the year. The soil water and temperature dynamics, as well as rainfalls and the penetration resistance, were registered in the field. In order to characterize the effect of mechanical and hydraulic stresses, 10 soil samplings (5–10cm depths) were conducted before/after tillage, during crop development (Tritricum aestivum) and after grazing. The water retention and shrinkage curves, air and saturated hydraulic conductivity, precompression stress, aggregate strength and cohesion between particles were measured. Our results show that the soil structure behaves dynamically at different scales due to mechanical and hydraulic stresses which impact the soil mechanical stability, porosity and related soil-pore functions. In spite of the low bulk density of the Andosol, the mechanical disturbance did not affect the soil structure and related pore functions significantly throughout the year, demonstrating the ability of the soil to recuperate its functions. As observed for the precompression stress (Pc<90kPa), bulk density (<1.7Mgm−3), air capacity (>8%) and hydraulic conductivity (>20cmd−1), the physical properties of the Andosol did not reach critical values in terms of subsoil compaction. The well-known high resilience capacity of volcanic ash soils allowed the integral functionality of these soils’ pores to recover, presenting the same or even greater values as compared to their initial condition; i.e. both hydraulic (k s ) and air (k l ) conductivity clearly decreased after the roller compacted the soil due to a decrease in the amount and continuity of macropores; however, as soon as wetting and drying cycles occurred and the biological activity started (root development during the growing season), k s and k l tended to increase as a consequence of a more continuous pore system, thus soil pores were able to reach the initial values previous to soil tillage. Finally, the shrinkage curves show the soil pores’ instability after tillage. At the same time, they illustrate the dynamic behavior of the soil structure, highlighting the fact that soils do not behave as a rigid body and temporal variability of hydraulic properties (macropores, hydraulic conductivity) must be expected. Therefore, better hydrological models which consider this dynamic behavior are needed. [Copyright &y& Elsevier]

Abstract: Soil physical properties continuously change as a result of wetting and drying cycles (WD), soil tillage and grazing events. In order to define sustainable grazing management, it is necessary to determine how the soil responds during and after applied external stresses. This is relevant in southern Chile where pastures are the main livestock feed throughout the course of the year and Andosols are exposed to great mechanical stresses by a wide range of soil water contents. Therefore, the purpose of this paper was to illustrate the effect of grazing, considering two grazing intensities in the winter: 50 and 200cowsha−1, on the temporal changes of structure-dependent properties of an Andosol in southern Chile. In order to characterize the impact of grazing, 15 soil samplings (5–10cm depths) were conducted over a 2 year period. The penetration resistance (PR) and soil water content were determined in the field. Air capacity (AC), air (k l ) and saturated hydraulic (k s ) conductivity, precompression stress (Pc), and aggregate strength (AS) were measured. Changes in the soil mechanical stability and pore functions were observed as a consequence of grazing events and WD cycles, indicating that the structure-dependent properties are dynamic. Animal trampling induced an increase in PR; however, the increase in soil mechanical strength may not affect root growth, considering the changes in time of the PR and the specific properties of Andosol (e.g. bulk density <0.9Mgm−3). Temporal variations in Pc did not exceed critical values for root growth even under high grazing intensities, indicating that the soil recuperates after the impact of trampling during grazing. The air capacity/conductivity values measured in our study reached critical values for gas exchange as a consequence of animal trampling; however, the Andosol showed its ability to recuperate its integral pore functionality. Finally, in spite of the low bulk density of the Andosol, the increasing grazing intensity during the winter did not affect their structural properties. This, however, does not mean that the soil can support large stresses indefinitely. Therefore, long-term investigations on the effects of grazing management on Andosol physical properties in southern Chile are strongly needed. [Copyright &y& Elsevier]

Abstract: Despite half a century of intensive research, the structure and presence of short-range ordered aluminosilicates in volcanic soils is still the focus of debate. Imogolite is easily distinguishable because of its tubular structure, whereas allophane compounds—usually described as spheres—are harder to identify, especially because of their variable structure and occurrence patterns. In addition, the local structure of allophanes can be very similar to that of proto-imogolite (imogolite precursor). Strangely, this similarity is seldom considered in most characterization studies. In this context, our study focuses on the structure of two Al-rich short range-ordered aluminosilicates of two different origins, from: (i) an Andosol B horizon (Andosol sample); and (ii) a weathered pumice grain (pumice sample). These natural samples were compared to a synthetic proto-imogolite. The three samples were analyzed using experimental tools that are commonly used for the identification of these nanophases (chemical composition, X-ray diffraction, nuclear magnetic resonance, Fourier transform infrared spectroscopy and transmission electron microscopy). The three samples exhibited the same local structure, but significant differences were observed at a larger scale. The pumice sample clearly showed ring-shaped particles, while the Andosol sample and the synthetic proto-imogolite were amorphous. Our results suggest that poorly ordered proto-imogolite, rather than Al-rich allophones and imogolites, is present in Andosol horizons. We believe that the mineralogy of these phases needs to be reassessed along with their growth mechanisms. [Copyright &y& Elsevier]

Abstract: Factors controlling soil respiration (R S) are of great interest because R S plays a critical role in determining global atmospheric carbon dioxide (CO2) concentrations. Substrate availability is one of the most important factors controlling R S. Soil microorganisms consume various substrates ranging from simple sugars supplied by aboveground photosynthesis to complex humic acids in soil organic matter; however, substrate decomposition rates depend on substrate availability. Thus, R S is partly determined by the amount and quality of available substrate. However, accurate quantification of the amount of available substrate is difficult because soil microorganisms utilize carbon (C) substrates of varying quality for R S. Water-soluble C (WSC), hot-water-soluble C (HWSC), and microbial biomass C are known as indicators of the amount of available soil C substrate. We continuously measured R S in two contrasting soils, Andosol and Fluvisol, during the cultivation of soybean and brassica crops with a 6-month fallow period between them. The total annual R S in Andosol and Fluvisol were 376±23 and 408±49g CO2-C m−2, respectively, with no significant difference between them. WSC and HWSC were measured every month during R S measurement. During the soybean growth period, R S and WSC were correlated, and soil type did not affect R S. During the fallow period, R S, HWSC and microbial biomass C in Fluvisol were higher than those in Andosol, despite the total soil C in Andosol being higher than that in Fluvisol. R S during brassica crop growth was not correlated with any of the measured substrate indicators. We therefore concluded that the relationships among the measures of available substrates and R S at the field level could provide vital information on seasonal changes in the interaction between the effects of soil type and plants on R S, thereby leading to a better understanding of belowground C dynamics. [Copyright &y& Elsevier]

Living mulch is a type of sustainable farming system that consists of cover crops planted either before or with a main crop; a living mulch is maintained as a living ground cover throughout the growing season of the main crop. Microbial biomass and abundance of mesofauna (microarthropods and enchytraeids) are important soil biological parameters in relation to soil function, plant productivity, and nutrient cycling; however, the effects of living mulch on these parameters are not fully understood. In this study we examined the effects of living mulch treatment with nitrogen fertilizer (0, 40, 160, or 200 kg ha−1) on the abundance of soil microarthropods (Oribatida, Mesostigmata, Prostigmata, and Collembola) and the effects of living mulch treatment on the dynamics of the soil biota (mesofauna, microarthropods, enchytraeids, and microbial biomass nitrogen) from spring to autumn. Our results showed that living mulch treatment significantly (p < 0.05) increased the grain weight of the main crop in both experiments. Generally, living mulch treatment had a positive effect on the abundance of mesofauna and microbial biomass nitrogen, despite pesticide usage. Nitrogen levels did not affect the number of microarthropods. The litter layer in living mulch significantly (p < 0.05) enhanced microbial biomass nitrogen and the abundance of Oribatida, Prostigmata, and Collembola. We conclude that living mulch enhances mesofaunal abundance and microbial biomass nitrogen and that the production of a litter layer by living mulch is one of the major mechanisms for this enhancement. [ABSTRACT FROM PUBLISHER]

Andosols and the soil components (allophanes, humic acids, and goethite) had been autoclaved to destroy the nuclease activity of soil microflora. DNA adsorption by allophanes and Andosols was decreased by increasing the amount of α-casein added to the allophanes and to soils up to casein concentration of 5 mg ml. DNA adsorption by humic acids was significantly increased by increasing the amount of α-casein up to 1.0 mg ml, whereas the addition of 20 mg α-casein ml completely blocked DNA adsorption. These results can explain why the addition of excess skim milk is operationally needed for effective DNA extraction from Andosols. The amount of DNA adsorbed by Andosols treated with dephosphorylated α-casein was significantly higher than that of not treated Andosols ( p < 0.01), thus showing an opposite behavior than α-casein addition, implying that phosphate groups of the protein can contribute to the decrease in the DNA adsorption by soil components. These results explain that the usefulness of skim milk as an additive for the extraction of DNA from Andosols is due to the presence of phosphate groups and hydrophobic components of casein, the main constituent of skim milk. [ABSTRACT FROM AUTHOR]

Andosols are characterised by high organic matter (OM) content throughout the soil profile, which is mainly due to the stabilisation of soil organic matter (SOM) by mineral interactions. The aim of the study was to examine whether there were differences in the chemical composition of mineral-associated SOM and free OM in the top A horizon and in the subsoil (horizons below the A11 horizon). Our experimental approach included the replicated sampling of a fulvic and an umbic Andosol under pine and laurel forest located on the island of Tenerife with a Mediterranean sub-humid climate. We determined the extent of the organo-mineral interactions by comparing the sizes of the light (free) and heavy (dense) soil fractions obtained by physical separation through flotation in a liquid with a density of 1.9 g cm. We determined the elemental and isotopic composition of both fractions and analysed their chemical composition by analytical pyrolysis. The elemental and isotopic composition showed similar values with depth despite the different vegetation and climatic conditions prevailing at the two sites. Carbon (C) stabilised by mineral interactions increased with depth and represented 80-90% of the total C in the lowest horizons. The heavy fractions mainly released N-containing compounds upon analytical pyrolysis, whereas lignin-derived and alkyl compounds were the principal pyrolysis products released from the light fractions of the top- and subsoil horizons. Principal component analysis showed that the chemical composition of OM stabilised by mineral interaction differs in the different horizons of the soil profile. In the A horizons, the chemical composition of this OM was similar to those of the light fractions, i.e. litter input. There was a gradual change in the bulk molecular composition from a higher contribution of plant-derived molecules in the light and heavy fractions of the A horizon to more microbial-derived molecules as well as black C-derived molecules at depth. We conclude that transport processes in addition to decomposition and possibly in situ ageing affect the chemical composition of mineral-associated OM in subsoils. [ABSTRACT FROM AUTHOR]

Abstract: Agroforestry represents an opportunity to reduce CO2 concentrations in the atmosphere by increasing carbon (C) stocks in agricultural lands. Agroforestry practices may also promote mineral N fertilization and the use of N2-fixing legumes that favor the emission of non-CO2 greenhouse gases (GHG) (N2O and CH4). The present study evaluates the net GHG balance in two adjacent coffee plantations, both highly fertilized (250kgNha−1 year−1): a monoculture (CM) and a culture shaded by the N2-fixing legume tree species Inga densiflora (CIn). C stocks, soil N2O emissions and CH4 uptakes were measured during the first cycle of both plantations. During a 3-year period (6–9 years after the establishment of the systems), soil C in the upper 10cm remained constant in the CIn plantation (+0.09±0.58MgCha−1 year−1) and decreased slightly but not significantly in the CM plantation (−0.43±0.53MgCha−1 year−1). Aboveground carbon stocks in the coffee monoculture and the agroforestry system amounted to 9.8±0.4 and 25.2±0.6MgCha−1, respectively, at 7 years after establishment. C storage rate in the phytomass was more than twice as large in the CIn compared to the CM system (4.6±0.1 and 2.0±0.1MgCha−1 year−1, respectively). Annual soil N2O emissions were 1.3 times larger in the CIn than in the CM plantation (5.8±0.5 and 4.3±0.3kgN-N2Oha−1 year−1, respectively). The net GHG balance at the soil scale calculated from the changes in soil C stocks and N2O emissions, expressed in CO2 equivalent, was negative in both coffee plantations indicating that the soil was a net source of GHG. Nevertheless this balance was in favor of the agroforestry system. The net GHG balance at the plantation scale, which includes additionally C storage in the phytomass, was positive and about 4 times larger in the CIn (14.59±2.20MgCO2 eqha−1 year−1) than in the CM plantation (3.83±1.98MgCO2 eqha−1 year−1). Thus converting the coffee monoculture to the coffee agroforestry plantation shaded by the N2-fixing tree species I. densiflora would increase net atmospheric GHG removals by 10.76±2.96MgCO2 eqha−1 year−1 during the first cycle of 8–9 years. [Copyright &y& Elsevier]

Analysing soil microbial communities is often hampered by DNA adsorption on soil organic compounds such as humic acids. However the role of humic acids in DNA adsorption and stability in soils remains controversial. To characterize DNA-humic acid interactions, we studied DNA adsorption on two commercially available humic acids and a soil humic acid extracted from an Andosol. Desorption of the adsorbed DNA using 4 different solutions-distilled water, 0.1 M NaCl, 0.1 M sodium phosphate buffer (pH 6.0), and 1% sodium dodecyl sulfate solution-was also studied to understand the mechanism of DNA adsorption on humic acids. Here, we show that humic acids play an important role in DNA adsorption to soils. DNA molecules were adsorbed on the humic acids, with adsorption increasing proportionally with the DNA concentrations in the solution. The adsorption on all humic acid samples was fitted with Freundlich equation, and the parameters obtained from the equation indicated a high affinity between the humic acids and DNA molecules. The total amount of DNA desorbed by the 4 solutions was less than 2% of the total DNA adsorbed on all the humic acids. The results demonstrate that DNA molecules are able to bind strongly to humic acids by ligand binding, hydrophobic interaction, aggregation, or precipitation. [ABSTRACT FROM AUTHOR]

Abstract: The effect of land use change on soil physical resilience of an Andosol was quantified for a native forest (NF), 30 year old pasture (P) and 1 year old crop (C). In order to define soil deformation and resilience, we calculated the coefficient of linear extensibility (COLE) during consolidation/shrinkage and after the recuperation of the soil, i.e. when the applied stress was released. Additionally, on the same soil samples the bulk density, water retention curve and air permeability were measured. Our results show that an intensification of land use induced greater mechanical and hydraulic stresses in the soil leading to higher structure stability (e.g. the pre-compression stress increased from 34 to 61kPa between the native forest and pasture), but lower pore resilience capacity (e.g. COLEr decreased from −0.13 to −0.10). Both kinds of stresses increased the bulk density of the soil (mechanical>hydraulic). However, while the loading cycle reduced the air permeability as a consequence of a reduction of macro pores, shrinkage created more continuous macro pores between aggregates which resulted in more pronounced gas fluxes. Finally, we concluded that a detailed analysis of shrinkage and consolidation curves along with air permeability measurements can be used to evaluate the physical resilience of the soil. [Copyright &y& Elsevier]

Abstract: 129Xe nuclear magnetic resonance (NMR) spectroscopic studies of xenon gas adsorbed on model systems representing soil porous components (Al (hyrd)oxides and charcoals) as well as natural soil materials (derived from a non-allophanic Andosol) were performed with the aim of characterising their micro- (<2nm) and mesopores (2–50nm). Both conventional, i.e. thermally polarised (TP), and laser-polarised or hyperpolarised (HP) 129Xe NMR was applied. The latter technique significantly increased sensitivity of the measurements. Information on the pore size range was derived from the 129Xe resonance shifts, δ, monitored as function of Xe loading, whereas the temperature dependences of δ provided information on the nature of xenon–pore surface interactions in terms of effective adsorption enthalpies. Dissolved organic matter (DOM) sorption on the mesoporous Al2O3 was shown to proceed inhomogeneously indicative by the Xe adsorption enthalpies corresponding to the co-existing “empty” pores and pores coated with organic species. In AlOOH, an interconnected system of micro- and mesopores was tested. The enhanced sensitivity of HP 129Xe NMR allowed us detecting micropores in charcoals, where N2 adsorption method underestimated porosity due to the restricted N2 diffusion at 77K. The interconnected pore structure of charcoals was attributed to the voids formed by both polyaromatic and aliphatic domains (evidenced by 13C NMR). The observed differences between the TP- and HP 129Xe NMR patterns were explained by the restricted xenon diffusion through charcoal particles caused by the constricted pore openings. Their suggested size is of the order of one or two diameters of the Xe atom. For the Andosol clay fractions, the large low-field 129Xe shifts (up to 175ppm) increasing with Xe pressure indicated a developed porosity most obviously comprised by the interconnected micro- and mesopores. Such porous network may originate from the “multi-domain” structure of soil clay particles, i.e. particles formed by agglomerated nano-sized crystallites. The latter are assumed to be the polynuclear Al x (H2O) y (OH) z clusters formed by hydrolysis reactions of Al3+ species after the destroying of Al-humus complexes by the H2O2-oxidation. [Copyright &y& Elsevier]

Abstract: Achieving high productivity using organic manure as a source of N offers new soil management possibilities in intensive agriculture. Our objective was to study the growth response of winter wheat (Triticum aestivum) to different fertilization regimes in long-term experiments in Japan. Semi-dwarf wheat varieties were grown in crop rotation with maize (Zea mays) with a high rate of organic manure (OM; 80tha−1 yr−1 for >10years, estimated N application rate is 739kgNha−1 yr−1), and standard (SF; 204–252kgNha−1 yr−1) or low (LF; 102–126kgNha−1 yr−1) rates of inorganic fertilizer for 3 years. We observed greater biomass production in OM than in SF or LF, which was attributable to a higher leaf area index, leaf N status, and stomatal conductance in OM. Grain yield in OM (6.6–8.9tha−1) was significantly higher than that in LF (3.5–6.6tha−1) for both cultivars, and comparable to that in SF (6.6–8.5tha−1). However, the dry matter partitioning during the grain-filling period suggested an imbalance in the sink–source relationship in OM: the number of grains was too large for the assimilation rate. Varietal differences in grain weight in OM resulted from differences in dry matter production during grain filling and, to a lesser extent, differences in grain density. The growth pattern of wheat under intensive manure application should be modified to favor biomass production during the post-anthesis stages. Based on our results, we discuss possible strategies for wheat improvement under high soil fertility in Japan. [ABSTRACT FROM AUTHOR]

Abstract: The shade impact by Inga densiflora on water use and drainage in a coffee agroforestry system (AFS) was compared to coffee monoculture (MC) in Costa Rica. Rainfall interception, transpiration, runoff and soil water content were monitored during 3 years. Runoff was lower in AFS than MC (5.4 and 8.4% of total rainfall, respectively) and a higher water infiltration was observed under AFS. Still, the higher combined rainfall interception+transpiration of coffee and shade trees in AFS resulted in a lower drainage than in MC. No coffee water stress was recorded either in AFS or MC as relative extractable soil water remained above 20% during the dry seasons. Time course of soil water content showed enhanced access to soil water between 100 and 200cm depth in AFS. This suggests complementarity for soil water between coffee and shade trees. The model HYDRUS 1D predicted that drainage at 200cm depth accounted for a large fraction of annual rainfall (68% for MC and 62% for AFS). Climatic scenario simulations showed (1) a potential competition for water between coffee and shade trees when the dry season was extended by 4–6 weeks compared to actual, and (2) a severe reduction in annual drainage, but without competition for water when rainfall was reduced down to 40% of the actual. [Copyright &y& Elsevier]

The montane rain forest belt on Mt Kilimanjaro forms an important water source for northern Tanzania that is threatened by both logging and fire. The aim of this study was to investigate the consequences of forest fragmentation on various aspects of the water cycle. Soil properties, rainfall, throughfall and soil water suction were analysed for mature forest, secondary forest patches and large clearings. A total of 10 plots located on the south-western slopes of the mountain between 2100 and 2300 m.a.s.l. were monitored from May 2000 to June 2002. Annual rainfall amounts ranged from 2000 to 2600 mm with high spatial and inter-annual variability. Rainfall interception ranged from 3 to 9% of incident rainfall in clearings, to a maximum of 32% in forests. In general, soils under mature forest were wettest and showed only minor moisture fluctuations throughout the year. Soils of secondary forest sites were driest and soil water suction exhibited the largest fluctuations. Additionally, the finer texture of soils under mature forest compared to secondary forest sites allowed higher amounts of soil water to be stored for similar soil water suction levels. Ventilation and radiation penetration, which influence the magnitude of interception, evaporation from the forest floor and transpiration, were probably higher in fragmented secondary than in closed mature forests. In clearings, higher throughfall and presumably lower transpiration rates led to moister conditions compared to adjacent secondary forest sites. Thus, soil conditions under mature forest were most suitable for optimum water storage on Mt Kilimanjaro. The transformation of closed mature forest to a mosaic of forests in different stages of regeneration led to increased spatio-temporal variability in soil moisture. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The burrowing nematode Radopholus similis is the most damaging banana nematode. To minimize nematicide applications, cropping systems based on fallow, crop rotation, and using clean planting material have been developed in the French West Indies. The survivorship of R. similis in water and soil was evaluated to optimize the collapse of its populations during the intercropping period and to better understand the risk of dissemination of nematodes by run-off water. In both Andosols and Nitisols, survivorship was significantly higher for males than for females. After 180 days, 21.7% of males and 9.8% of females were still alive, whereas no juveniles survived after 150 days. Survivorship was much lower in water and soil solution than in soil. The mean half-life of males was 8.8 days and only 6.2 days for females, but the difference between sexes was less after 1 month: 8% of both males and females in the initial population survived after 35 days. These results suggest that resource allocation for males was directed towards reproduction, whereas females expend energy foraging and laying eggs, and are thus disadvantaged in the absence of host plants. The relatively long survivorship of males of R. similis enables them to fecundate females without competing for food after becoming adults. [Copyright &y& Elsevier]

The relationship between plant phosphorus (P) uptake and soil microbial biomass phosphorus (biomass P) or available phosphorus (Truog P) was estimated in a Gleyic Andosol in Sapporo, Hokkaido, in a 4-year field trial (2004–2007). Every year, the soil was treated in duplicate (each plot 36 m2) or triplicate (each plot 24 m2) with chemical fertilizer, cow manure compost or sewage sludge compost, and then kidney beans ( Phaseolus vulgaris) were planted. Pooled data of the shoot content of P at harvest over the 4 years was significantly correlated with biomass P determined 1 month after the application of fertilizer ( P < 0.01). A multivariate analysis revealed that the grain yield was significantly positively correlated with the shoot content of P ( P < 0.01) and significantly negatively correlated with the shoot content of calcium ( P < 0.05), but not correlated with the shoot content of either nitrogen or potassium. These results suggest that P is the most limiting element to affect the productivity of kidney bean plants in this trial and that biomass P is an important P source that explains the differences in P availability among soil amendments. Biomass P is a better indicator of P availability for kidney beans grown in Gleyic Andosols compared with Truog P, which is widely used in Japan. [ABSTRACT FROM AUTHOR]

The adsorption of DNA by two andosols was investigated as function of solution pH, ionic strength in solution and some solutes, so as to understand the behavior of extracellular DNA molecules in two andosols. DNA adsorptions greatly decreased by increasing pH of suspensions in a pH range of 3.0–9.0. The adsorption of DNA molecules by both andosols was not affected by ionic strength from 0.1 to 0.5 mol L−1 NaCl. However, the DNA adsorption increased proportionally by increasing Mg2+ concentration in the suspension. Addition of phosphate decreased DNA adsorption, indicating competition between DNA molecules and phosphate ion in the adsorption by andosols. These results suggest that there are several DNA adsorption mechanisms in soil. [ABSTRACT FROM AUTHOR]

Abstract: We quantified the carbon contents of grassland and forest soil using conventional methods and studied the changes in their dynamics by measuring δ13C and Δ14C. Soil samples were taken from a neighboring Miscanthus sinensis grassland and Pinus densiflora forest in central Japan. Both had been maintained as grassland until the 1960s, when the latter was abandoned and became a pine forest by natural succession. The soil carbon content of the forest was much lower than that of the grassland, implying that the soil carbon decreased as the grassland became forest. The δ13C values were very similar in the grassland and forest, at approximately −20‰, suggesting that M. sinensis (a C4 plant) contributed to carbon storage, whereas there was little carbon accumulation from P. densiflora (a C3 plant) in forest soil. The Δ14C values and calculated soil carbon mean residence time (MRT) showed that the soil carbon in the upper A horizon was older, and that in the lower A horizon was younger in forest than in grassland. From these results, we conclude that young, fast-MRT soil carbon is decomposed in the upper A horizon, and old, stable soil carbon was decomposed in the lower A horizon after the pine invasion. [Copyright &y& Elsevier]

Abstract: The burrowing nematode, Radopholus similis (Cobb.) Thorne, causes the most damage to bananas. To minimize nematicide applications, cropping systems that use fallow, crop rotation and clean planting material have been developed in the French West Indies. In order to optimize the benefit of the intercropping period, we studied the survivorship of R. similis in different soil types and conditions. We monitored the survivorship of calibrated populations of R. similis in the laboratory on a Nitisol and on an Andosol, two soils derived from volcanic ashes and pumices. We studied water potentials ranging from 0 to −700kPa on undisturbed soil and on soil previously frozen to get rid of living nematodes. Mortality of adult R. similis decreased regularly, and was fairly well described by Teissier''s model. In the previously frozen soils, R. similis survived longer in wet soils (half-life of 21–46 days at 0 to −5kPa) than in dry soils (half-life of less than 10 days between −80 and −250kPa). In contrast, in undisturbed soils, R. similis survived longer in dry soils: half-lives ranged from 57 days at −273kPa to 17 days at water saturation in the Andosol, and 36 days at −660kPa to 14 days at water saturation in the Nitisol. These results are consistent with the absence of anhydrobiosis in R. similis, unlike Pratylenchus coffeae. P. coffeae survivorship curves over time do not follow a model derived from exponential decrease like Teissier''s model. These results also show that the recommended one year host-free period required to sanitize soils cannot be shortened without risk, even if flooding the soil could improve it. [Copyright &y& Elsevier]

We measured nitrous oxide (N2O) and carbon dioxide (CO2) fluxes from the soil surface and in the soil through to a depth of 0.3 m, and their concentration profiles through to a depth of 0.6 m in both a Gray Lowland soil with macropores and cracks and an Andosol with undeveloped soil structure in central Hokkaido, Japan. The objective of the present study was to elucidate any differences in N2O production and flux in the soil profile between these two soil types. In the Gray Lowland soil, the N2O concentration above 0.4 m increased with an increase in soil depth. In the Andosol, there were no distinctive N2O concentration gradients in the topsoil when the N2O flux did not increase. However, the N2O concentration at a depth of 0.1 m significantly increased and this concentration was higher than the concentration below 0.2 m when the N2O flux greatly increased. Thus, the N2O concentration profiles were different between these two soils. The contribution ratios of the N2O produced in the top soil (0–0.3 m depth) to the total N2O emitted from the soil to the atmosphere in the Gray Lowland soil and the Andosol were 0.86 and 1.00, respectively, indicating that the N2O emitted from the soil to the atmosphere was mainly produced in the top soil. However, the contribution ratio of the subsoil to the N2O emitted from the Gray Lowland soil was higher than that of the Andosol. There was a significant positive correlation between the N2O flux through to a 0.3 m depth and the flux from the soil to the atmosphere in the Gray Lowland soil only. These results suggest that N2O production in the subsoil of the Gray Lowland soil could have been activated by NO3− leaching through macropores and cracks, and subsequently the N2O produced in the subsoil could have been rapidly emitted to the atmosphere through the macropores and cracks. [ABSTRACT FROM AUTHOR]

Soil temperature is an important factor influencing crop growth. Within limits, a higher soil temperature will promote crop growth, particularly in cool climates. The application of compost increases the soil temperature, probably by drying the soil surface, but the relationship between soil temperature and soil water remains unclear. We conducted pot and field experiments on a bare Andosol in a cool climate region. The pot experiment examined the effects of compost application on soil temperature and evaporation, and the field experiment examined the effects of the properties and amount of compost on soil temperature. Pots with compost had a higher soil temperature and less evaporation than pots without compost. The decrease in evaporation and the increase in soil temperature by compost application were significantly correlated. The field experiment included 15 treatments: 12 compost treatments (four types of compost × three levels) and three chemical fertilizer treatments (one type of fertilizer × three levels). There was a significant correlation between soil temperature and the dry weight of the applied compost. We conclude that compost application increases soil temperature by decreasing evaporation from the soil surface. In addition, soil temperature increases with increasing dry weight of the compost applied, regardless of the chemical properties. [ABSTRACT FROM AUTHOR]

Abstract: The present study aimed to investigate the NH3 volatilization loss from field-applied compost and chemical fertilizer and evaluate the atmosphere–land exchange of NH3 and particulate NH4 + (pNH4) at an upland field with volcanic ash soil (Andosol) in Hokkaido, northern Japan. Two-step basal fertilization was conducted on the bare soil surface. First, a moderately fermented compost of cattle manure was applied by surface incorporation (mixing depth, 0–15 cm) at a rate of 117 kg N ha−1 as total nitrogen (T-N) corresponding to 9.9 kg N ha−1 as ammoniacal nitrogen (NH4–N). Twelve days later, a chemical fertilizer containing 10% (w/w) of NH4–N as a mixture of ammonium sulfate and ammonium phosphates was applied by row placement (cover depth, 3 cm) at a rate of 100 kg N ha−1 as NH4–N. The study period was divided into the first-half, beginning after the compost application (CCM period), and the second-half, beginning after the chemical fertilizer application (CF period). The mean air concentrations of NH3 and pNH4 (1.5 m height) were 7.6 and 3.0 μg N m−3, respectively, in the CCM period; the values were 3.7 and 3.9 μg N m−3, respectively, in the CF period. The composition ratios of NH3 to the sum of NH3 and pNH4 (1.5 m height) were 72% and 49% in the CCM and CF periods, respectively. The NH3 volatilization loss from the compost was 0.8% of the applied T-N (or 9.3% of the applied NH4–N) and that from the chemical fertilizer was near zero. Excluding the period immediately after the compost application, the upland field acted as a net sink for NH3 and pNH4. [Copyright &y& Elsevier]

Abstract: Soil moisture and gaseous N-flux (N2O, N2) dynamics in Costa Rican coffee plantations were successively simulated using a mechanistic model (PASTIS) and two process-based models (NGAS and NOE). Two fertilized (250 kg N ha−1 y−1) coffee plantations were considered, namely a monoculture and a system shaded by the N2 fixing legume species Inga densiflora. In situ N2O fluxes were previously measured in these plantations. NGAS and NOE used specific microbial activities for the soils. To parameterize NGAS, we estimated N mineralization via in situ incubations and the contribution of heterotrophic soil respiration to total soil respiration. Potential denitrification rates and the proportion of denitrified N emitted as N2O were measured in the laboratory to define the values of NOE parameters, as well as nitrification rates and related N2O production rates for parameterizing both models. Soil moisture and both NGAS and NOE N2O fluxes were best modelled on an hourly time step. Soil moisture dynamics were satisfactorily simulated by PASTIS. Simulated N2O fluxes by both NGAS and NOE (3.2 and 2.1 kg N ha−1 y−1 for NGAS; 7.1 and 3.7 kg N ha−1 y−1 for NOE, for the monoculture and shaded plantations respectively) were within a factor of about 2 of the observed annual fluxes (4.3 and 5.8 kg N ha−1 y−1, for the monoculture and shaded plantations respectively). Statistical indicators of association and coincidence between simulated and measured values were satisfactory for both models. Nevertheless, the two models differed greatly in describing the nitrification and denitrification processes. Some of the algorithms in the model NGAS were apparently not applicable to these tropical acidic Andosols. Therefore, more detailed information about microbial processes in different agroecosystems would be needed, notably if process-oriented models were to be used for testing strategies for mitigating N2O emissions. [Copyright &y& Elsevier]

To examine the bioremediation potential of Phlebia brevispora in dioxin-contaminated soil, the fungus was inoculated into autoclaved soil that was contaminated with 2,7-dichlorodibenzo-p-dioxin (2,7-DCDD) or 1,3,6,8-tetrachlorodibenzo-p-dioxin (1,3,6,8-TCDD). Three types of soils, organic-rich soil (Andosol), organic-poor soil (Granitic Regosols), and paddy soil, were used for the construction of artificially contaminated soil to understand the influence of the soil property on fungal growth and dioxin degradation ability. Under a solid-state condition, although the growth of the fungus improved in organic-rich soil, the degradation of 2,7-DCDD was inhibited. Although the degradation of 1,3,6,8-TCDD under a solid-state condition was inhibited severely, 1,3,6,8-TCDD degradation was observed under a slurry-state condition in organic-poor soil. In the case of organic-rich soil, an increase in water content improved the 1,3,6,8-TCDD degradation efficiency. When the historically contaminated paddy soil was treated with P. brevispora under a slurry-state condition, 1,3,6,8-TCDD as the main contaminant degraded 50% after 90d incubation. [Copyright &y& Elsevier]

Summary: Rainfall redistribution by plant canopy, notably the water flow down the plant stem (stemflow), modifies the incident rainfall rate at the soil surface and may affect runoff generation. To test this hypothesis, we observed and measured runoff at the plant scale with banana cultivated on tropical Andosol. Observation of runoff by video and matrix potential monitoring showed that, during a runoff event, the matrix potential increased mainly downstream from the pseudostem in line with the slope, delimiting a saturated zone of runoff propagation that appeared on video monitoring. The results indicate that rainfall redistribution by plant canopy, i.e. stemflow and dripping areas, enhances runoff even on soil with a high infiltration rate (mean hydraulic conductivity at saturation Ks of 67 mm h−1). Data analysis of 40 runoff events showed that events were composed of at least two runoff phases characterized by an abrupt increase in runoff coefficient (RC) from 0.16 to 0.65 between the first and the second phase. The change in RC was related to rainfall rate. Also, between the first and the second runoff phase, the apparent infiltration rate at the plot scale decreased from 30 to 10 mm h−1. This was related to an increase in runoff contributing areas (RCA), from an estimated 18% to 93% of the plot surface. However, data analysis and model simulations showed that the increase in mean rainfall rate in RCA due to stemflow was not sufficient to account for large runoff volumes. Hence, one must also take into account the spatial variation of hydraulic conductivity at saturation with low values relative to RCA (estimation for the second runoff phase was 7.6 mm h−1). Moreover, simulation results implied Ks decreases with time. Finally, rainfall redistribution may have an impact at a larger scale. In banana plantations, the hydraulic connectivity of runoff areas can enhance the stemflow effect up to the plot scale. From this point of view, the two-compartment scheme we chose for modeling could be applied at a larger scale: one compartment including stemflow and the relative water pathways and one compartment for the rest of the plot. [Copyright &y& Elsevier]