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Soil hydraulic properties control the provision of hydrological services. Vegetation and topography influence these properties by altering soil structure and porosity. The underlying mechanisms are not yet fully understood for the high Andean region. In this study, we examined how vegetation and topographic attributes are related to soil hydraulic properties and soil pore structure in young volcanic ash soils, and further correlated them to soil texture, organic carbon, and root characteristics to explain these relationships. In a 0.7 km2 study site located in the Andean páramo of northern Ecuador, we measured soil water retention, saturated hydraulic conductivity, bulk density (BD), and pore size distribution parameters on eight soil profiles with contrasting vegetation types (cushion-forming plants vs. tussock grasses) and topographic positions (summit vs. hillslope). We observed significant differences in soil hydraulic properties and soil pore structure in the uppermost horizons by vegetation type, whereas topography had a minor effect. In the A horizons, we found higher water retention at saturation and field capacity (10%–14%), higher total available water (8%–15%), and higher saturated hydraulic conductivity (4–12 times) under cushion-forming plants compared to tussock grasses. The elevated values under cushion plants were attributed to the presence of larger pores, lower soil BD, and higher soil organic carbon content as a result of coarser root systems. Total available water was generally high (0.34–0.40 cm3 cm−3), and locally not associated with any soil property. The higher water retention in soils under cushion vegetation can enhance soil water storage for plants and the regulation of water flows during prolonged rainfall events. The saturated hydraulic conductivity of the surface horizons is high compared to rainfall intensities resulting in high infiltration capacity; whilst its decline with depth reveals the potential for generation of subsurface stormflow, especially below cushion-forming plants. Our findings highlight that soil hydraulic properties differ among vegetation types, and show the significance of vegetation types for soil hydrology.

Paddy soil management is generally thought to promote the accumulation of soil organic matter (SOM) and specifically lignin. Lignin is considered particularly susceptible to accumulation under these circumstances because of the recalcitrance of its aromatic structure to biodegradation under anaerobic conditions (i.e., during inundation of paddy fields). The present study investigates the effect of paddy soil management on SOM composition in comparison to nearby agricultural soils that are not used for rice production (non-paddy soils). Soil types typically used for rice cultivation were selected, including Alisol, Andosol and Vertisol sites in Indonesia (humid tropical climate of Java) and an Alisol site in China (humid subtropical climate, Jiangxi province). These soil types represent a range of soil properties to be expected in Asian paddy fields. All upper-most A horizons were analysed for their SOM composition by solid-state 13C nuclear magnetic resonance (NMR) spectroscopy and for lignin-derived phenols by the CuO oxidation method. The SOM composition was similar for all of the above named parent soil types (non-paddy soils) and was also not affected by paddy soil management. A substantial proportion (up to 23%) of the total aryl-carbon in some paddy and non-paddy soils was found to originate from condensed aromatic-carbon (e.g., charcoal). This may be attributed to the burning of crop residues. On average, the proportion of lignin was low and made up 20% of the total SOM, and showed no differences between straw, particulate organic matter (POM), and the bulk soil material. The results from CuO oxidation are consistent with the data obtained from solid-state 13C NMR spectroscopy. The extraction of lignin-derived phenols revealed low VSC (vanillyl, syringyl, cinnamyl) values for all investigated soils in a range (4 to 12 g kg−1 OC) that was typical for agricultural soils. In comparison to adjacent non-paddy soils, the data do not provide evidence for a substantial accumulation of phenolic lignin-derived structures in the paddy soils, even for those characterized by higher organic carbon (OC) contents (e.g., Andosol- and Alisol (China)-derived paddy soils). We conclude that the properties of the parent soil types are more important for the lignin content of the soils than the effect of paddy management itself.

The drying process of volcanic ash soils often results in the formation of shrinkage cracks with consequences for their physical properties (i.e., decrease of water retention capacity) and land use management. This study presents the soil water characteristics and shrinkage behaviour (shrinkage phases in terms of void and moisture ratio), the shrinkage potential (COLE index), and the pore shrinkage capacity (PSI) for 5 and 20 cm depth of a Haplic Arenosol (tephric) and two Silandic Andosols under pasture management along a soil gradient from the Andean mountains to the coastal range in southern Chile. The main focus of the presented study is on the effect of soil development in conjunction with the weathering of volcanic ash soils on the shrinkage properties. The water retention and shrinkage curves were continuously determined for undisturbed soil samples (100 cm(3)) during a drying process under laboratory conditions. In addition, the shrinkage curve data were modelled to distinguish different shrinkage zones. The results suggest that the investigated soil properties vary depending on soil development. The more developed Andosols had higher total porosities (up to 70 cm(3) cm(-3)) than the less developed Arenosol. The shrinkage behaviour of the Haplic Arenosol showed a wide structural shrinkage phase, whereas the Silandic Andosols revealed a more pronounced proportional shrinkage phase, which is related to the pore size distribution. In addition, wide and narrow coarse pores of the Haplic Arenosol and medium and fine pores of the Silandic Andosols determine the shrinkage potential (COLE) and the pore shrinkage capacity, respectively. The finer-grained and organic matter-rich Andosols indicate a higher COLE index (> 0.03-0.09) compared to the Arenosol (

Dissolved silica (DSi) plays an important biogeochemical role in the fjords of northern Chilean Patagonia (44–48°S), where it drives high biogenic productivity and promotes carbon burial. It is generally believed that the DSi riverine input to lakes and coastal environments is controlled by a combination of factors including lithology, climate, topography, vegetation, and meltwater input. In northern Chilean Patagonia several authors have proposed that the postglacial volcanic ash soils (andosols) may play a significant role in the high supply of DSi to the regional fjords. To assess the influence of andosols on DSi concentrations in north Patagonian rivers, we mapped andosol thickness and compared our results with river chemistry. The mineralogical and geochemical composition of three representative andosol profiles was also examined to evaluate the efficiency of weathering processes. The andosol thickness map clearly demonstrates that volcanic ash was predominantly deposited on the eastern side of the regional volcanoes, reflecting the influence of the prevailing westerly winds on the distribution of pyroclastic material. Mineralogical and geochemical results show that the andosol parent material has the typical andesitic basaltic signature of the regional volcanoes, i.e. high amounts of amorphous material, plagioclase, K-feldspar, and pyroxene. Down-profile variations in soil mineralogy and geochemistry indicate increased leaching of silica with depth, resulting from weathering of the volcanic parent material. For the five studied watersheds, a highly positive correlation (R2=0.98) was found between average andosol thickness and DSi concentrations, suggesting that andosol thickness is the main parameter affecting DSi concentrations in north Patagonian river systems. On seasonal timescales, increased precipitation (winter) and glacial meltwater (summer) input can significantly reduce DSi concentrations. We argue that the weathering of andosols constitutes the most important source of DSi to the lakes and fjords of northern Chilean Patagonia, explaining the particularly high regional rates of biogenic silica production. Copyright © 2015 John Wiley & Sons, Ltd.

Phosphorus (P) is a major plant nutrient, however, its availability in volcanic ash soils is presumed to be small, due to its specific sorption on short-range order minerals. We analyzed distinct P fractions in volcanic ash soils of different age (60 to > 100,000 y BP) under pine forests in Central Mexico to investigate their changes along a chronosequence of Regosols, Andosols, and Lixisols, and to evaluate if P availability limits tree growth at any particular stage. Top soil and subsoil samples were first analyzed by the Tiessen and Moir method, which failed to extract exhaustively “organic” and “occluded P”, and “P associated with apatite”. Therefore, we modified the fractionation scheme by including a “recalcitrant organic P” fraction obtained from the difference between P determined in air-dried subsamples and subsamples burned at 300°C; P adsorbed to short-range order minerals was assessed in an extraction with NH4-oxalate, and P in primary minerals by subtracting the sum of all other fractions from total P contents determined by XRF. This we did after discovering that primary P occurred in the form of fluorapatite included in plagioclase, volcanic glass or olivine. We also measured P contents in pine needles and related these with the “mobile soil P” fractions. The results show that “organic P” reaches maximum contents in 10,000-y old soil, as does P associated with short-range order minerals, while P occluded into crystalline oxides increases constantly over time. After 100,000 y, 31% of total P still remains in the form of primary P in A horizons. “Mobile P” was constant > 40 mg kg−1 in Regosols and Andosols and related positively with foliar P contents, which were within adequate nutritional ranges. Only in Lixisols small “mobile P” concentrations in soil correspond with inadequate P contents in pine needles.

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.

The assessment of benzene emissions from a soil to the atmosphere is important for the preservation of human health and the management of contaminated soils. The adequacy of a simple numerical model, assuming two-phase diffusion and linear equilibrium of liquid-solid adsorption, was investigated by comparing the changes in benzene concentration in an Andosol with predicted benzene flux in a flux chamber. Different initial benzene concentrations were applied to the soil with a water content of 25 kg kg -1 to determine the liquid phase adsorption coefficient (K D ), which was ultimately determined to have an optimum value of 1.29 mm 3 kg - 1 . In addition, the influence of varying water contents on benzene transport was investigated using the soil samples but with different initial water contents (10, 25, and 40 kg kg -1 ) and at a fixed initial benzene concentration (50 mg kg -1 ). The results showed that the simple model adequately predicted benzene transport in soil for a period of

The aim of this study was to determine the effect of land-use and forest cover depletion on the distribution of soil organic carbon (SOC) within particle-size fractions in a volcanic soil. Emphasis was given to the thermal properties of soils. Six representative sites in Mexico were selected in an area dominated by Andosols: a grassland site, four forested sites with different levels of degradation and an agricultural site. Soils were fractionated using ultrasonic energy until complete dispersion was achieved. The particle-size fractions were coarse sand, fine sand, silt, clay and particulate organic matter from the coarse sand sized fraction (POM-CS) and fine sand (POM-FS). Soil organic carbon decreased by 70% after forest conversion to cropland and long-term cultivation; forest cover loss resulted in a decrease in SOC of up to 60%. The grassland soil contained 45% more SOC than the cropland one. Soil organic carbon was mainly associated with the silt-size fraction; the most sensitive fractions to land-use change and forest cover depletion were POM followed by SOC associated with the silt and clay-sized fractions. Particulate organic matter can be used as an early indicator of SOC loss. The C lost from the clay and silt-sized fractions was thermally labile; therefore, the SOC stored in the more degraded forest soils was more recalcitrant (thermally resistant). Only the transformation of forest to agricultural land produced a similar loss of thermally stable C associated with the silt-sized fraction.

Incomplete dispersion of aggregates is a well-known difficulty when analyzing soil texture of Andosols, particularly if no fresh soil material is available. To facilitate such investigations, several dispersion procedures were carried out on air-dried samples rich in short-range-order minerals, originating from selected Andosol profiles (S Mexico). As a result, we propose an improved method based on a sequential chemical treatment with K oxalate, NH4 oxalate, and oxalic acid that reliably removes cementing agents and allows for a stable dispersion of soil particles after addition of Na pyrophosphate. This method was proved to be well reproducible and highly reliable for routine grain-size determinations. The potential error caused by the inherent risk of dissolving primary minerals or fresh volcanic glass remains far beyond the analytical error resulting from the incomplete and irreproducible dispersion of highly resistant aggregates by other commonly used techniques.

Agricultural fields are an important anthropogenic source of atmospheric nitrous oxide (N2O) and nitric oxide (NO). Although many field studies have tested the effectiveness of possible mitigation options on N2O and NO emissions, the effectiveness of each option varies across sites due to environmental factors and field management. To combine these results and evaluate the overall effectiveness of enhanced-efficiency fertilizers [i.e., nitrification inhibitors (NIs), polymer-coated fertilizers (PCFs), and urease inhibitors (UIs)] on N2O and NO emissions, we performed a meta-analysis using field experiment data (113 datasets from 35 studies) published in peer-reviewed journals through 2008. The results indicated that NIs significantly reduced N2O emissions (mean: −38%, 95% confidential interval: −44% to −31%) compared with those of conventional fertilizers. PCFs also significantly reduced N2O emissions (−35%, −58% to −14%), whereas UIs were not effective in reducing N2O. NIs and PCFs also significantly reduced NO (−46%, −65% to −35%; −40%, −76% to −10%, respectively). The effectiveness of NIs was relatively consistent across the various types of inhibitors and land uses. However, the effect of PCFs showed contrasting results across soil and land-use type: they were significantly effective for imperfectly drained Gleysol grassland (−77%, −88% to −58%), but were ineffective for well-drained Andosol upland fields. Because available data for PCFs were dominated by certain regions and soil types, additional data are needed to evaluate their effectiveness more reliably. NIs were effective in reducing N2O emission from both chemical and organic fertilizers. Moreover, the consistent effect of NIs indicates that they are potent mitigation options for N2O and NO emissions.

To investigate the potential of synchrotron-based X-ray Absorption Near-Edge Structure spectroscopy (XANES) at the sulphur (S) K-edge for a discrimination of adsorbed and precipitated sulphate in soils and soil particles, XANES spectra of ionic sulphate compounds and Al/Fe hydroxy sulphate minerals were compared with spectra of SO 4 2- adsorbed to ferrihydrite, goethite, haematite, gibbsite or allophane. Ionic sulphate and hydroxy sulphate precipitates had broader white-lines (WL) at 2482.5 eV (full width at half maximum (FWHM) of edge-normalized spectra, 2.4-4.2 eV; Al hydroxy sulphates, 3.0 eV) than SO 4 2- adsorbed to Al/Fe oxyhydroxides or allophane (FWHM, 1.8-2.4 eV). The ratio of the white-line (WL) height to the height of the post-edge feature at 2499 eV (WL/PEF) was larger for SO 4 2- adsorbed to Al/Fe oxyhydroxides or allophane (8.1-11.9) than for Al/Fe hydroxy sulphates and ionic sulphates (3.9-5.7). The WL/PEF ratio of edge-normalized S K-edge XANES spectra can be used to distinguish adsorbed from precipitated SO 4 2- in soils and also at microsites of soil particles. The contribution of adsorbed and precipitated SO 4 2- to the total SO 4 2- pool can be roughly quantified. Adsorbed ester sulphate may result in overestimation of precipitated SO 4 2- . The spectra of most soils could be fitted by linear combination fitting (LCF), yielding a similar partitioning between adsorbed and precipitated SO 4 2- as an evaluation of the WL/PEF ratio. The SO 4 2- pool of German forest soils on silicate parent material in most cases was strongly dominated by adsorbed SO 4 2- ; however, in three German forest soils subject to elevated atmospheric S deposition, a considerable portion of the SO 4 2- pool was precipitated SO 4 2- , most likely Al hydroxy sulphate. The same is true for Nicaraguan Eutric and Vitric Andosols subject to high volcanogenic S input. In the subsoil of the Vitric Andosol, adsorbed SO 4 2- and Al hydroxy sulphate coexist on a micron scale.

The presence of soils with andic properties on German territory has been suspected for decades and there are numerous reports of sites where they may potentially occur. Andic properties, however, are not adequately represented by the German soil-classification system. The German taxonomic category "Lockerbraunerde" has not been revised or reconciled with international taxonomic categories since the year 1957, when it was initially proposed. With this review, we show that there are true Andosols of both the silandic (allophane-containing) and the aluandic (Al-Humus-dominated) type in Germany and that their properties differ substantially from other soils which merely exhibit low bulk density. By (1) comparing soil carbon storage between some German Andosols, Chernozems, and nonandic Cambisols with particularly low bulk density and (2) elucidation of the differential pedogenetic pathways leading to Andosol formation, we further demonstrate that Andosols are important objects of study in research issues of contemporary interest. We propose that appropriate measures be taken to lay the foundations for the protection and conservation of these soils, because they are valuable as archives of natural history and provide opportunities to study unique soil processes.

Summary Soil temperature influences both soil formation processes and land use possibilities, and is a classification criterion in some systems. Vegetation cover is one of the factors that affects temperature. In this paper, we estimate the classes of soil temperature regimes, using Soil Taxonomy, for Andosols located in parts of the island of Tenerife, Canary Islands, Spain, which are influenced by the trade winds. The study focuses on soils under three types of natural vegetation – cloud forest, tree-heath woodland and pine forest – and adjacent plots where the vegetation has been replaced with, respectively, pine forest, herbaceous plants and cropping, and herbaceous plants. Temperature was measured monthly at 50-cm depth for a period of 2–4 years at three sites, both in the natural vegetation plots and in the plots where the vegetation was modified. Under natural vegetation the soil temperature regimes are all ‘iso’ (difference < 6°C between summer and winter temperatures) and reflect tropical conditions. The switch to shorter vegetation, and particularly to use of the land for cropping, causes the soil temperature regime to change from iso to non-iso.

Summary Andosols in the vicinity of active volcanoes receive large inputs of SO2 and HCl. We studied (i) the mechanisms of acid buffering, (ii) the effect of cation removal on the short-term acid neutralization capacity and (iii) the consequences of acid buffering for secondary mineral formation in vitric Andosols around the Central American volcanoes Poas and Masaya. Two types of short-term (24 hour) acidification experiments at pH 3 were conducted to simulate an open system in which leaching prevails (extraction with protonated cation exchange resin) and a closed system with no leaching (pHstat titration with cation accumulation). Long-term buffering under field conditions (mean soil pH: 4.6) and its effect on secondary mineral formation were studied by analysis of samples from a transect of decreasing acid input by IR spectroscopy, microscopic methods and geochemical equilibrium modelling. In Poas samples the main short-term buffering mechanisms at pH 3 are plagioclase dissolution and protonation of organic matter. Long-term acid buffering under field conditions led to weathering of plagioclase crystals but did not result in protonated carboxyl groups. In Masaya samples mineral and/or glass dissolution are the dominant acid buffering mechanisms in laboratory experiments and under field conditions. For both sites, cation accumulation during pH 3 acidification experiments led to a decrease of the effective acid neutralization capacity. Due to different climatic conditions, Al is precipitated as basaluminite at Masaya while it seems to be susceptible to leaching at Poas. Acid buffering resulted in the formation of amorphous silica at both sites.

Andosol formation involves the rapid, abundant and in situ formation of non-crystalline materials from tephra deposits. A large amount of humus complexed with Al also accumulates in the A horizons. As these materials are rich in Al or Fe compared to the parent tephra, the concentrations of the major and minor elements change significantly during Andosol formation. The objectives of this study were to examine how the rock type of the tephra and its weight loss during the formation process affect the changes in the element concentrations of Andosols. A total of 95 samples with different rock types from 18 pedons of Andosols in Japan were used to determine the total concentrations of 54 elements. Principal component analysis suggested that the degree of weathering and the rock types of parent tephra are the important factors in the variation of the element concentrations in Andosols. Three rock types, dacitic, andesitic and basaltic-andesitic, were identified from the V and Zn contents of ferromagnetic minerals separated from the Andosol samples. Basaltic Andosols were identified from the abundant coloured volcanic glass and olivine in the sand fraction. Regarding concentrations of 41 elements, at least one group based on rock type was significantly different from one to three other groups at the P = 0.05 level. The content of oxalate-extractable Si (Si o ), Al (Al o ) and Fe (Fe o ) was used as an index to show the extent of Andosol development. Relatively strong correlations between the element concentrations and Si o , Al o and Fe o as well as other weathering indices were found in the andesitic samples. Among these elements, at least 27 (Be, Al, Ti, Fe, Y, Zr, Nb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, Tl, Pb, Th and U) were enriched in the Andosols and the increases in these concentrations were related to total weight loss due to soil formation processes.

The aim of this study was to use nitrogen gas adsorption to study the complex surface properties of a wide range of Andosol Ah and Bw horizons; N 2 gas adsorption not only provides specific surface area, SSA, but it also yields complementary information about micropore volume and hydrophilic and/or hydrophobic surface properties. Total SSAs were positively related to micropore SSA which was, in its turn, positively interrelated to the dimensionless parameter C of the Brunauer-Emmett-Teller (BET) equation (micropore N 2 filling) and microporous allophane content. The more allophanic the Andosol horizon sample, the larger were its total, micropore and mesopore SSAs. On the other hand, strong negative exponential relationships were obtained between either total or micropore or mesopore SSA and soil organic carbon content, with a SSA threshold at an organic carbon content of c. 8-10%, the SSAs being extremely small at larger organic carbon content values. Both SSA BET and C BET decreased non-linearly as a function of the organic C/allophane ratio, with either a SSA BET or a C BET threshold at an organic C/allophane ratio value of 3-5, above which both SSA BET and C BET were very small (mostly the aluandic Andosol Ah horizons). The more the soil allophanes are assumed to be coated, the more hydrophobic the soil surfaces become and the smaller both SSA BET and C BET become; nitrogen gas has a permanent quadrupole moment and therefore acts as a polar probe when surfaces are sufficiently hydrophobic. The antagonistic roles played by allophanes and organic matter in both the SSAs and the values of the dimensionless parameter C in the BET equation were also highlighted by (i) multiple linear regressions between the SSAs and both allophane and organic carbon contents and (ii) principal-component analysis of SSA BET, C BET and soil constituent (allophane, ferrihydrite and organic C) contents.

Summary The purpose of the research presented here was to find an answer for the possible origin and mode of deposition of soil parent materials for Andosol formation and to link the soilscape variability to the various soil forming factors since the Last Glaciation. Soil formation was studied along a 20-km climo-toposequence in the Miocene Andesitic area of the South Gurghiu Mountains (Romania). Six representative soil profiles were chosen from a larger geopedological study on the western slope of the Seaca-Tatarca volcano. Based on the macromorphological, micromorphological and chemical properties it was possible to say that the soil profiles are composed of two major types of soil material: a relict type, with a crystalline clay fraction; and a recent type with an amorphous colloidal fraction. It was found that the present-day distribution of the Andosols on the Seaca-Tatarca volcano must be related to the rejuvenation of the soil parent material by processes of aeolian input of frost-shattered volcaniclasts and by a glacial reworking. It appears that the extension of the glaciated areas during the Pleistocene could have been larger than concluded from geomorphological studies. General Carpathian glacial features are closely related to the altitudinal distribution of the Carpathian Andosols. At the present climatic optimum, the soils of Seaca-Tatarca are influenced by pedogenetic processes of freeze-thaw, oxido-reduction, strong leaching and internal colluviation, strong accumulation of organic matter and considerable biological activity. Those Andosols that are located in special microtopographic positions with stronger water percolation tend to evolve towards Podzols.

Summary Indoor cylindrical titanium lysimeters (80 cm internal diameter × 150 cm height) filled with undisturbed soil were constructed to study the behaviour of solutes in soil. They were equipped with thermometers, tensiometers, ceramic porous cups, percolate reservoirs, and an automatic irrigation system. Soil sampling was conducted using an original drilling technique. Examination of the wetting front and downward migration of Br− in an Andosol monolith showed no artificial sidewall flow.

To identify the important soil components involved in 2,4-dichlorophenoxyacetic acid (2,4-D) adsorption on Andosols, 2,4-D adsorption on a surface horizon of an Andosol was compared with that on hydrogen peroxide (H2O2)-treated (soil organic matter [SOM] was removed), acid-oxalate (OX)-treated (active metal hydroxides and SOM were removed), and dithionite-citrate-bicarbonate (DCB)-treated (free and active metal [hydr]oxides and SOM were removed) soil samples at equilibrium pHs ranging from 4 to 8. Although the untreated soil contained a large amount of organic C (71.9 g kg-1), removal of SOM had little effect on 2,4-D adsorption. Active surface hydroxyls, which were attached to the active and free metal (hydr)oxides and metal SOM complexes, were identified as the most important soil functional group for 2,4-D adsorption. The dominant mechanism of the 2,4-D adsorption was a ligand exchange reaction in which the carboxylic group of 2,4-D displaced the active surface hydroxyl associated with metals and formed a strong coordination bond between the 2,4-D molecule and soil solid phase. The ligand exchange reaction reasonably accounted for the selective adsorption of 2,4-D over Cl-, competitive adsorption of phosphate over 2,4-D, reduction in plant-growth-inhibitory activity of soil-adsorbed 2,4-D, and the high 2,4-D adsorption ability of Andosols. Although a humic acid purified from the soil did not adsorb 2,4-D, the presence of the humic acid increased 2,4-D adsorption on Al and Fe, probably by inhibiting the hydrolysis and polymerization of Al and Fe resulting in the preservation of available adsorption sites on these metals. The adsorption behavior of 2,4-D on soils could be a good index for predicting the adsorption behavior of other organic acids in soils.

Two model systems were constructed to measure horizontal and vertical movement of bacteria in soil. These systems were applied to measuring movement of Ralstonia solanacearum (race 1, biovar 3), a causal agent of bacterial wilt of tomato, in andosol and sand at 28°C. The first system was used to measure horizontal movement of the bacteria in soil packed in a narrow horizontal frame. Suspension of the pathogen was applied to soil at one end of the frame, and bacterial number per gram of soil was measured over distance from the inoculation point after 4 days. Horizontal movement of R. solanacearum in supersaturated soil, but without flow, was possibly due to diffusion and the front advanced at 2.2 cm/day in andosol, and at 8.1 cm/day in sand. Using the same experimental system, but applying water inflow to one end of the frame only, the bacterium was detected at the front of water in andosol and sand. The front of the distribution advanced at 20.4 cm/h in andosol and 66.3 cm/h in sand. In the second experimental system, a cylinder of soil packed in a short tube was soaked with water, and soil at the top of the tube was inoculated with bacterial suspension. Immediately, soil cylinders were turned upward, and the bacterial number per gram of soil was measured along vertical distance from the inoculation point after 7 days. Using the system with andosol, the capillary water front rose to 32.5 cm over 7 days after inoculation, and R. solanacearum reached to 18.8 cm height. In sand, capillary water rose to 20.0 cm and the bacteria reached to 16.3 cm height.

The effect of land use on the water retention capacity of Umbric Andosols in south Ecuador was studied. The objective was to acquire a better insight into the hydrological processes of the ecosystem and the role of the soil, in order to assess the impact of changing soil properties due to land use change on the hydrology of the high Andes region. Field data on the water retention capacity at wilting point of Umbric Andosols were collected for both cultivated field conditions and original bush vegetation. The pH in water and in NaF, texture, organic matter content and dry bulk density were measured to show which physicochemical soil characteristics are responsible for the water retention of the Umbric Andosols and for the irreversible loss in water retention due to air drying. Organic matter content appears to be very important and certainly more important than allophane clay content. Water retention of the organic litter layer was calculated to be 16 mm, this would be lost when vegetation was cleared and the land cultivated.

A number of soils are described in the literature as having andic and spodic soil properties, but have developed in nonvolcanic and nonallophanic materials and lack typical Podzol eluvial and illuvial horizons. They cover a wide range of parent materials and different types of climate. They have always been regarded as restricted to small areas. They were assigned to Andisols/Andosols, Podzols/Spodosols, or andic Inceptisols in the WRB and Soil Taxonomy and sometimes also named Cryptopodzols or Lockerbraunerden. Recent soil surveys in Bhutan, E Himalayas, show these soils are widespread at altitudes between 2200–3500 m asl and are spanning several bioclimatic zones. The aim of this study is the detailed characterization of specific properties and processes of formation by physical and chemical analyses, NMR spectroscopy, column experiments, SEM, XRD, and 14C dating in one of these soils in E central Bhutan. The results indicate advanced soil development with high amounts of oxidic Fe and Al compounds, low bulk densities (partly 85%, and a dominance of Al-hydroxy-interlayered phyllosilicates. Scanning electron microscopy of sand fractions indicate microaggregates highly resistant to dispersion. Column experiments show podzolization with mobilization and translocation of DOM, Fe, and Al. Nuclear-magnetic resonance spectroscopy and 14C ages of 16,000 BP indicate stabilization of DOM. Applying classification criteria, these soils appear to have andic and spodic features, but are neither Andosols nor Podzols senso strictu. Especially the role of Fe seems to be underestimated with regard to the specific soil-forming processes. Because of their widespread occurrence and distinct properties, we suggest either a simplification of the criteria for existing soil types or a clearly defined separation of volcanic and nonvolcanic/nonallophanic Andosols. Andische Eigenschaften in Boden aus nicht vulkanischem Material in Zentralbhutan In der Literatur werden Boden mit andischen und podsolischen Eigenschaften aus nicht vulkanischem und nicht allophanischem Material beschrieben, die keine podsoltypischen Eluvial- und Illuvial-Horizonte aufweisen. Sie sind aus unterschiedlichen Ausgangsmaterialien entstanden, kommen in verschiedenen Klimaten vor und galten bisher als wenig verbreitet. Sie wurden in die Gruppe der Andisols/Andosols, Podzols/Spodosols oder andic Inceptisols nach WRB und Soil Taxonomy eingeordnet sowie im deutschen Sprachraum als Cryptopodsole oder Lockerbraunerden klassifiziert. Neuere bodenkundliche Untersuchungen in Bhutan im ostlichen Himalaya zeigen, dass diese Boden uber mehrere bioklimatische Hohenzonen hinweg zwischen 2200 m und 3500 m u. NN flachenhaft vorkommen. Ziel der Arbeit ist es, an einem dieser Boden die spezifischen Eigenschaften und Bildungsprozesse mittels physikalischer und chemischer Analysen, NMR-Spektroskopie, Saulenexperimenten, Elektronenmikroskopie, Tonmineralanalyse und 14C-Datierungen detailliert zu beschreiben. Die Ergebnisse deuten auf fortgeschrittene Bodenentwicklung mit hohen Gehalten an oxidischen Fe- und Al-Verbindungen, niedrigen Lagerungsdichten (teils 85 % sowie einer Dominanz von Tonmineralen mit Al-Hydroxo-Zwischenschichteinlagerungen hin. Elektronenmikroskopische Aufnahmen zeigen, dass die Sandfraktion uberwiegend aus extrem stabilen Mikroaggregaten besteht. Die Saulenexperimente deuten auf Podsolierungsdynamik mit einer Mobilisierung und Verlagerung von DOM, Fe und Al hin. NMR-Spektroskopie und 14C-Alter um 16.000 a vor heute weisen ferner auf Stabilisierung organischer Verbindungen hin. Im Hinblick auf eine Klassifizierung erfullen die untersuchten Boden andische wie podsolische Kriterien, sind im engeren Sinne weder Andosole noch Podsole. Insbesondere die Rolle von Fe scheint bei der spezifischen Bodenbildungsbedingungen bisher unterschatzt worden zu sein. Aufgrund ihrer weiten Verbreitung und den spezifischen Eigenschaften wird eine Vereinfachung der Kriterien fur bereits bestehende Bodentypen oder eine klare Trennung von Andosolen aus vulkanischen und nicht vulkanischen/nicht allophanhaltigen Materialien vorgeschlagen.

We determined concentrations of Ag, In, Sn, Sb and Bi, and fractionated them by sequential extraction procedures, in five Japanese soils: Andosol-1 (grassland), Andosol-2 (forest), Cambisol (forest), Fluvisol (vegetable garden) and Regosol (forest). Average concentrations of Ag, In, Sn, Sb and Bi were 0.17 ± 0.08, 0.081 ± 0.019, 2.2 ± 0.5, 0.83 ± 0.32 and 0.32 ± 0.12 mg kg -1 , respectively. Average distributions of the chemical fractions (omitting those with an abundance H 2 O 2 -extractable, organically bound (H 2 O 2 -Org) (18%) > metal-organic complex-bound (Me-Org) (10%) > amorphous metal oxide-bound (am-MeOx) (8.3%); In, residual (61%) > H 2 O 2 -Org (12%) > Me-Org (8.7%) > crystalline Fe oxide-bound (cr-FeOx) (8.2%) > am-MeOx (7.4%); Sn, residual (40%) > Me-Org (19%) > carbonate-bound (12%) > cr-FeOx (9.0%) > H 2 O 2 -Org (7.8%) > am-MeOx (6.9%); Sb, residual (34%) > Me-Org (18%) > am-MeOx (16%) > cr-FeOx (8.9%) > H 2 O 2 -Org (8.7%) > easily reducible metal oxide-bound (re-MeOx) (6.8%) > carbonate-bound (6.1%); Bi, am-MeOx (26%) > H 2 O 2 -Org (26%) > Me-Org (19%) > residual (17%) > cr-FeOx (12%). Proportions of the mobilizable (exchangeable + carbonate-bound + Me-Org + re-MeOx) metal fractions were in the order Sn > Sb > Bi > Ag ≅ In, and Cambisol > Andosol-2 > Regosol > Andosol-1 > Fluvisol. The proportions were predicted by multiple regression equations including pH, surface area, C contents, cation exchange capacity and clay content of the soils as independent variables (R 2 > 0.96, P < 0.02).

In a corn (Zea mays L)-rye (Secale cereale L) rotation field, the N output (plant uptake) and N input (crop residue and fertilizer applied) were measured for two years in order to evaluate the N balance in a forage production field. The soil was Low-humic Andosol (mesic Typic Hapludand). The disappearance of crop residues on both a dry matter and N basis, and the seasonal fluctuations of total, inorganic, and available soil N content in the field were investigated. The interaction between the nitrogen balance and the soil N contents are discussed. The total plant N uptake of the corn and rye exceeded the sum of the N input of the fertilizer applied and the N from crop residues, so the N balance of the corn-rye rotation had a negative value (two year average: −8.4 gN m−2). After the gradual disappearance of crop residue on the dry matter basis, rapid disappearance on the N basis was observed. At the same time, the C/N ratio decreased to less than 20. The soil available (38.4–55.3 mg kg−1) and inorganic (21.5–45.2 mg kg−1) N had their lowest values in spring. After they increased in early summer, they decreased in late summer and increased in autumn. The total N (0.5–0.7%) gradually decreased during the experimental period. The results indicated that the soil-available N and inorganic N in the present study were highly dependent on the fertilizer-applied N. The relation among management practices, N input and soil available N contents are discussed. It is suggested that the negative N balance is one of the causes for a decrease in soil total N.

The south Ecuadorian Andean mountain belt between 3500 and 4500 m altitude is covered by a highly endemic and fragile ecosystem called pThe Histic Andosols covering this region have highly developed hydric properties and exert a key function in the hydrological regulation of the p´ aramo ecosystem. Unlike most Andosols, their extreme water retention capacity is not due to the presence of typical minerals such as allophane or imogolite. Although these minerals are virtually absent, the large organic carbon content, due to organometallic complexation, gives rise to similar properties. The water content at 1500 kPa can exceed 2000 g kg � 1 , and the high hydraulic conductivity at saturation (about 15 mm h � 1 ) drops sharply when low suction is applied. The three methods applied, i.e. the inverted auger hole, the tension infiltrometer and the constant-head permeameter method, give very similar results. The p´ aramo is characterized by a slow hydrological response and a good water regulation, caused by the combination of a high water storage capacity and high conductivity. The wide pore size distribution of the organometallic complexes results in a water retention curve that differs significantly from the classic Mualem-Van Genuchten description, but can better be described with a simple linear or semilogarithmic model. The soils investigated are very prone to irreversible structural changes caused by land-use changes. The conversion of natural land for cultivation has a large impact on the hydrological function of the region. The water storage capacity increases by 5 to 30%, and the hydraulic conductivity is 31% higher in cultivated catchments. These changes are related to a larger peak flow, a smaller base flow and generally a smaller discharge buffering capacity, despite the higher storage capacity. Copyright  2005 John Wiley & Sons, Ltd. aramo; Andosols; runoff response; infiltration; water retention; land-use changes; hydraulic conductivity

Multiple or split N fertilizer applications during a single cropping period is a recommended practice for controlling N (specifically NO 3 –N) leaching into groundwater. Here, we demonstrate the benefit of split fertilizer applications in two typical upland soils of Japan (sand and Andosol) using a combination of a laboratory experiment and modeling. Soil water flow and N transport properties of the soils were measured using standard procedures. Transient N and water transport experiments were conducted in cylindrical soil columns under single (lumped) and split NH 4 –N applications. The column experiments were successfully simulated using Richards9 equation and an advection–dispersion model with equilibrium nonlinear sorption conditions and first-order transformation for N speciation. Using the model for the two soils, several irrigation and fertilizer management scenarios were then simulated based on 1992 through 2000 meteorological data to investigate the long-term effects of lumped and split fertilization schedules for a representative set of crop and irrigation conditions. In comparison with lumped applications, split fertilizer applications were found to consistently reduce the amount of N leaching, even though year-to-year differences of N leaching reductions between sand and Andosol were significant. For unstressed crops, the actual reduction in N leaching are shown to depend on the timing of precipitation and irrigation events, on soil type, and on plant N uptake behavior. However, across all scenarios, two split applications instead of a single, lumped application reduced the N leaching fraction by approximately one-third. In the sandy soil, a three-way split resulted in further leaching reductions compared with the two-way split. Six-way split applications did not result in further N leaching improvements in either sand or Andosol. After adjusting N application rates to account for reduced N use efficiency, N leaching rates for unstressed crops under lumped fertilization were found to be several times higher than under split applications.

The surface composition of particles present in the fine earth (< 2 mm) of 50 soil horizons differing in composition and pedogenetic origin (13 soil profiles) was analysed by X-ray photoelectron spectroscopy (XPS) to assess the capability and limitations of this technique and to gain better knowledge of the soil samples. The surfaces were systematically enriched in carbon, sometimes up to 1000 times, indicating that the soil particle surfaces are coated with organic substances, even in horizons where the bulk organic content is less than 0.1 g kg(-1). The distribution of carbon in the various oxidation states was 0.569 +/- 0.008 C-[0], 0.275 +/- 0.004 C[+1], 0.089 +/- 0.003 C[+2] and 0.066 +/- 0.002 C[+3] for most horizons (mean +/- standard error, 69 data). Only Andosol surface horizons systematically had surface organic matter in a more oxidized state. After correcting the results for the presence of organic coatings, we found that Si was generally depleted and Al enriched at the surface of soil particles, while Fe was either depleted or enriched depending on the sample considered. However, the coating of the coarser soil particles by the finer ones and their differential composition explained this observation and limits the interest of XPS for characterizing the surface enrichment of inorganic elements in crude soil samples. These limitations should be considered when interpreting XPS results in future work. Nevertheless, XPS can analyse the adsorbed organic matter and its functional composition of carbon without the need for any chemical or physical extraction that might alter the structure and composition of the organic molecules.

The small-scale variability (0.5 m) of atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) concentrations and soil water contents in a volcanic silt loam soil (Haplic Andosol, FAO system) was studied in an area of 0.1 ha. Descriptive and spatial statistics were used to analyse the data. On average we recovered 102% of the applied atrazine 2 h after the herbicide application (CV = 35%). An increase in the CV of the concentrations with depth could be ascribed to a combination of extrinsic and intrinsic factors. Both variables, atrazine concentrations and soil water content, showed a high horizontal variability. The semivariograms of the atrazine concentrations exhibited the pure nugget effect, no pattern could be determined along the 15.5-m long transects on any of the seven sampling days over a 55-day period. Soil water content had a weak spatial autocorrelation with a range of 6-10 m. The dissipation of atrazine analysed using a high vertical sampling resolution of 0.02 m to 0.2 m showed that 70% of the applied atrazine persisted in the upper 0.02-m layer of the soil for 12 days. After 55 days and 410 mm of rainfall the centre of the pesticide mass was still at a soil depth of 0.021 m. The special characteristics of the soil (high organic carbon content, allophanic clay) had a strong influence on atrazine sorption and mobility. The mass recovery after 55 days was low. The laboratory degradation rate for atrazine, determined in a complementary incubation study and corrected for the actual field temperature using the Arrhenius equation, only accounted for about 35% of the losses that occurred in the field. Results suggest field degradation rates to be more changeable in time and much faster than under controlled conditions. Preferential flow is discussed as a component of the field transport process.

We tested whether a ‘Lockerbraunerde’ from the heights of the Zittauer Gebirge in Eastern Saxony exhibited andic properties and classified it according to the rules of the World Reference Base for Soil Resources (WRB, 1998). To achieve this, we characterized a selected soil by means of routine soil analysis; selective dissolution procedures; X-ray diffraction (XRD); X-ray fluorescence (XRF), and Transmission Electron Microscopy (TEM). We used field criteria (Thixotropy; NaF-field test) to obtain a map of the spatial distribution of soils with potential andic properties. We found that the soil fulfilled all requirements to be classified as an Andosol. The composition of the colloidal phases was exactly intermediate between sil-andic and alu-andic. At the same time, the soil had a spodic horizon [determined through the depth function of the Alo+½Feo criterion]. As there was no indication of vertical translocation of metal-organic complexes, but sufficient evidence to suggest the downward movement of mobile Al/Si-phases, we maintain to classify the soil as an Endoskeleti-Umbric Andosol and propose the existence of a pedogenetic pathway intermediate between Podsolisation and Andosolization. We conclude that the spodic horizon in the WRB is not well defined because of the dominance of the Alo+½Feo criterion over morphological evidence. We further suggest the German soil taxonomy to be modified to better represent soils containing short range order minerals. Ein Andosol aus Sachsen Diese Arbeit behandelt das Problem, wie deutsche Lockerbraunerden nach den Kriterien der World Reference Base for Soil Resources (WRB, 1998) einzustufen sind. Dazu haben wir uberpruft, ob eine Lockerbraunerde aus dem Zittauer Gebirge uber ‘andic properties’ im Sinne der WRB verfugt, und den Boden nach den Vorgaben der WRB klassifiziert. Dazu setzten wir Routineverfahren der Bodenanalyse, sowie Rontgendiffraktometrie (XRD), Rontgenfluoreszensanalyse (XRF), Transmissionselektronenmikroskopie (TEM) und Verfahren zur selektiven Auflosung von ‘short range order Mineralen’ ein. Fur den Landschaftsausschnitt ‘Hochwald’ wurde eine Karte der Verteilung potenzieller Andosole angefertigt, die auf Feldmethoden (Thixotropie; NaF-Feldtest) zur Bestimmung von ‘short-range order’ Mineralen gestutzt wurde. Das untersuchte Bodenprofil wurde als Endoskeleti-Umbric Andosol klassifiziert. Die kolloidalen Bestandteile in diesem Profil nahmen eine Zwischenstellung zwischen den Kategorien sil-andic und alu-andic ein. Gleichzeitig wurde auf der Basis des Alo+½Feo-Verhaltnisses zwischen Ober- und Unterboden die Gegenwart eines spodic horizon diagnostiziert. Da jedoch kein Hinweis auf die vertikale Verlagerung von metallorganischen Komplexen gefunden werden konnte, aber gleichzeitig sichere Hinweise auf die unabhangige Verlagerung und Wiederausfallung von mobilen Al/Si-Phasen auftraten, wurde die Klassifikation als Andosol beibehalten. Wir vermuten fur das Profil “Lausche” das Vorliegen eines pedogenetischen Prozessgeschehens, das zwischen Podsolierung und Andosolbildung anzusiedeln ist. Wir folgern ferner, dass der ‘spodic horion’ der WRB nicht hinreichend vom ‘andic horizon’ abgegrenzt ist. Dies fuhren wir auf die in der WRB hohere Wichtung des Alo+½Feo-Kriteriums gegenuber morphologischen Eigenschaften zuruck. Wir schlagen auserdem vor, die deutsche Bodensystematik hinsichtlich ihrer Aussagekraft gegenuber Boden mit ‘short-range order’ Mineralen zu aktualisieren.

Summary Andosols developed on basaltic material are naturally rich in metals. Organic matter and allophane, the key colloids of these soils, have a strong affinity for trace metals, but are intimately mixed so that speciation of trace metal is difficult to determine. We used three complementary approaches, namely physical fractionation, chemical extraction and potentiometric measurement, to distinguish them. Physical particle-size separations and chemical selective dissolution of allophanes and organic matter were combined to demonstrate relations between the occurrence of colloids and contents of Cu and Zn in an andic B horizon. About 22% of total soil Cu and 7% of total soil Zn were present in the

We evaluated the effectiveness of capillary-wick samplers (PCAPS) for continuous monitoring of resident nitrate concentration in three 'soil-crop-climate' systems differing in soil type, land use and climate. These systems involved: (i) acid silty soils under a beech-oak forest affected by heavy N-NH4+ deposition in Belgium; (ii) silty soils under wheat cropping and a short rotation willow coppice plantation (SRC) in Belgium; and (iii) volcanic ash soils under plantain cultivation with and without urea fertilization in Colombia. The PCAPS continuously applied a suction of 0 to 5.4 kPa to the soil water below the effective rooting zone without the need for an auxiliary vacuum source. The nitrate concentrations showed large variations over time and ranged between 6-192 mg l(-1) under forest, 19-143 mg l(-1) under wheat, 11-47 mg l(-1) under SRC and 3-138 mg l(-1) under fertilized plantain. The analysis of the soil leachates collected with PCAPS confirms previous results dealing with leaching of nitrate and alkaline and alkaline-earth cations in similar 'soil-crop-climate' systems. It was concluded that PCAPS was a suitable tool to collect soil solutions and that it could help to assess nitrate leaching losses in various ecological or cropping conditions.

Soils-based evidence derived from thin section micromorphology is used to explore contrasts in pre-Hispanic and Hispanic arable land management practices associated with raised fields in an inter-Andean valley of Ecuador. Differences in textural pedofeature characteristics sug- gest that, where they are found in the same locality, camellon systems were more intensively manured and cultivated than wachu systems. Both, however, were more intensively managed than traditional Hispanic arable fields. The importance of the camellon in pre-Hispanic agri- culture is emphasized by soils-based evidence that highlights the efforts made to clear these fields of volcanic ash after the Quilotoa eruption of ca. A.D. 1280. This research suggests that, in an andosol context, pre-Hispanic and Hispanic arable land management practices leave relict and fossil soil micromorphology features that can be used to interpret land use inten- sities. � 2002 Wiley Periodicals, Inc.

Buried palaeosols of central Mexico, not previously analysed from a palaeopedological standpoint, have helped to develop a reliable regional model of Late Quaternary climatic change. This paper focuses upon morphological and micromorphological properties, particle-size distribution, and extractable Fe, Al and Si of seven palaeosols (named PT1–PT7) in the vicinity of the Nevado de Toluca volcano. The characteristics of Andic Cambisol PT1, similar to those of modern soils in semi-arid environments, indicate a drier climate in the first half of the Holocene. Humic Andosols PT2–PT4 are analogous to modern volcanic soils of humid forest environments. They show evidence that a moist palaeoclimate prevailed during marine oxygen isotope stages (OIS) 2 and 3. Luvisols PT5 and PT6, which are assumed to have formed at the end of marine OIS 5 to marine OIS 4, also indicate humid conditions. We attribute the differences between Andosols PT2–PT4 and Luvisols PT5–PT7 to variations in the duration in the pedogenesis rather than to changes in palaeoclimate. Micromorphological features of Andosol to Luvisol transition confirm that these soils form an evolutionary sequence. Being for the most part consistent with lacustrine records, the palaeosol properties do not reflect the episodes of ‘drier climate’ during the Last Glacial Maximum, however, as shown by diatom and palynological data from lake sediments. Mesoclimate variations and/or incompleteness of ‘soil memory’, reflecting mostly periods of humid pedogenesis, probably provide the reason for this disagreement. Copyright © 2001 John Wiley & Sons, Ltd.

Low-activity clay soils on old planation surfaces of the tropics are generally considered as stable end points of soil formation. It is therefore surprising to find Andisols on them. We characterized the properties of six profiles representative of these soils in the western part of the Nilgiri Hills (2000-2500 m above mean sea level), Southern India, where the present climatic conditions are cool (mean annual temperature 15°C) and humid (mean annual rainfall 2500 mm). Thick (50-80 cm) dark-reddish brown topsoil overlies strongly desilicated yellowish-red materials. This horizon has andic properties to a sufficient depth and the carbon content requirement of the melanic epipedon to place these soils in the Andisol order. Our data as well as the history of the Nilgiri Hills suggest that the formation of these nonallophanic Andisols resulted from the succession of two main steps. First, a 'lateritic' weathering cycle led to the relative accumulation of secondary AI and Fe oxides. Later, the accumulation of organic matter favoured by a more recent climatic change induced complexation by organic acids of AI and Fe oxides, and the production of enough metal-humus complexes to give rise to andic properties. Such soils, in which secondary AI and Fe oxides, generally considered as indicators of an advanced weathering stage, are involved in a new cycle of soil formation, are original Andisols.

The phosphorus (P) buffer coefficient, a ratio of the increase in extractable P to the amount of applied fertilizer P, is a source of considerable uncertainty in determining the amount of fertilizer needed to meet crop P requirements. The use of clay as a predictor of the P buffer coefficient has been suggested for soils of similar mineralogy. However, it has not been satisfactory for soils with a wide range of soil mineralogies but relatively high clay content. The objective of this study was to improve the prediction of buffer coefficients using soil characteristics associated with the process of P sorption, such as mineralogy, surface area, and aggregation. The soil P sorption site density, estimated from detailed clay mineralogy, and reactive mass, the fraction of the total soil mass in the surface aggregates where newly added P can be sorbed, were used to predict the buffer coefficient. The P buffer coefficients of 10 soils with a wide range in P sorption were estimated by Mehlich 3, modified Truog, and 0.5 M NaHCO 3 extractants for incubation periods of 32 and 180 d. The inclusion of P sorption site density and reactive mass substantially improved predicting the P buffer coefficients when compared with the P buffer coefficients predicted by only soil clay content. Statistical models showed that the P buffer coefficients were negatively correlated with both log of the P sorption site density and reactive mass. Thus, soils with fewer P sorption sites, lower reactive mass, and larger aggregate size will tend to have higher buffer coefficients, indicating that a greater portion of the added P remains plant available.

Information on soil conditions in New Zealand is needed to assess soil quality at a national scale. We tested a standard set of 16 primary indicators at 29 sites (0-10 cm depth) across nine soil great groups with matched examples of indigenous forest, plantation forest, pastures, and crops. Soils under indigenous forest were acidic (pH 5.5-5.7), low in Olsen P (5-14 μg cm -3 ), with high microbial C (814-1228 μg cm -3 ), respiration (1.1-1.4 μg C cm -3 h -1 ), total C (31.8-52.9 mg cm -3 ), macroporosity (9.6-11.7% v/v), and total available water (29.2-31.5% v/v). Plantation forest soils had generally similar characteristics. Pasture soils were less acidic (pH 5.3-6.9) than forest soils, but with more available P (5.5-43.0 μg cm -3 ), higher total C (30.7-141.5 mg cm -3 ), total N (2.7-9.0 mg cm -3 ), and mineralizable N (68-175 μg cm -3 ). The physical condition was similar to forest soils. Cropped soil had low total C (20-34 mg cm -3 ), microbial C (160-956 μg cm -3 ), respiration (0.29-1.33 μg C cm -3 h -1 ), and total available water (6.7-30.1% v/v), but high pH (5.8-7.2), Olsen P (11.2-199 μg cm -3 ), and bulk density (0.96-1.3 g cm -3 ). Principal component analysis identified outlier sites and grouped land uses independently of soil great groups. Some indicators were less useful because of high variability (unsaturated hydraulic conductivity), correlation to other indicators (microbial C) or interpretation difficulties (respiration). Overall, the standardized approach provided useful information about soil conditions on a national scale.

Sulfate sorption by forest soils decreases the potential detrimental effect of S deposition on cation leaching, Twenty-four soils from the 3416-km 2 area surrounding two lignite-fueled power-generating plants in NW Spain were studied to relate SO 2 4 sorption to soil properties and ultimately to the parent material. The area contains a variety of parent materials, and has a wide range of acidic soils (Haplumbrepts, Fulvudands, and Kanhaplohumults), Total annual precipitation ranges from 1100 to 1900 mm yr -1 and mean annual temperature is 12°C. Sulfate sorption was studied by adding either 0.4 or 1.6 mM SO 2 4 solutions to soils. Sorption decreased in the following order: amphibolite > biotitic schist > granite > phyllite and was positively related to Al extractable with sodium hydroxide, oxalate, and pyrophosphate. and to Fe extractable with dithionite-citrate and oxalate, which were high in soils derived from basic materials. Organic matter apparently had counteracting effects on SO 2- 4 sorption. First, sorption was important in surface horizons with pH-NaF ≥9.7, mainly due to the presence of Al-humus complexes, which often give these soils an andic character. Second, sorption was specially low in surface horizons of soils derived from acidic materials with pH-NaF- 8.0, which may be attributed to competition between SO 2- 4 and organic acids for sorption sites, in addition to the low content of reactive surfaces, Sorption was positively related to soil pH due to the positive relation between Fe and Al oxy-hydroxides and basic materials, These results suggest the need to take into account the influence of parent material on SO 2- 4 sorption in assessing the sensitivity of soils to S deposition.

Differences in crop and fertilizer management are known to influence P retention by soils. An experiment was conducted to study the effect of soil characteristics and management practices on P sorptoin behavior of the highland plateau soils of Ethiopia. Surface samples from two Vertisols, an Andisol, and an Alfisol were collected from farmers' fields, research station farms, and from non-cultivated-non-fertilized areas. Phosphorus sorption data were obtained by equilibrating 3-g soil samples in 30 mL of 0.01 M CaCl 2 containing various amounts of KH 2 PO 4 . Inorganic P fractions were determined by the Hedley P fractionation scheme. There was little variation in P sorption among Vertisol samples of alluvial origin as a result of cultivation-fertilization practices. For soils of volcanic origin (Vertisol2 and Andisols), and the Alfisol, samples collected from farmers' fields sorbed more P than the non-cultivated and research station samples. Least amounts of applied P sorbed by the non-cultivated Andisol samples reflect the relatively large amounts of resin extractable P initially present in these soils and demonstrate that labile P initially present in the soil can influence subsequent P sorption. Stepwise regression analysis of the P sorption data showed that resin P accounts for 81% of the variation in P sorption at 0.2 mg P L -1 in solution. The highest amount of P was sorbed by samples collected from farmers' fields and was mainly due to the practice of continuous cropping with minimal P fertilization, which depletes labile P, and therefore requires higher levels of P fertilization for optimum crop yield.

Arsenic is known to be immobilized in soils through oxyanion sorption reactions involving metal (hydr)oxides. While the mechanisms involved in oxyanion sorption are relatively well characterized in aerobic systems, the response of (hydr)oxides to fluctuating soil redox conditions, and its impact on As sorption, is poorly understood. This study investigated the influence of soil flooding and drying on As sorption and Fe fractionation. Four soils exhibiting a range in As sorption capacity were incubated under flooded (anaerobic) conditions. After the flooding period, the pH and redox potentials of each soil suspension were measured and saturation indices were calculated for standard soil minerals. The suspensions were air dried at room temperature and the short-range order Fe (oxalate-extractable) and crystalline Fe (dithionite-extractable) fractions determined. Separate flooded-dried samples were resuspended in 0.1 M NaCI for AsO 4 sorption measurements. Prolonged soil flooding resulted in a decrease in soil redox potential and an increase in dissolved Al, Fe, Mn, and Si. Drying the previously flooded soils resulted in an increase in As sorption. Selective extraction indicated that the flooding-drying treatments increased the short-range order Fe fraction while depleting the free oxide fraction. These changes in Fe mineralogy most likely increased the surface area and number of potential As sorption sites.

Predicting P sorption by weathered soils in order to manage soil, crop, and natural resources has been an important but elusive goal of soil science for decades. This study evaluated several soil properties, including mineralogy, of weathered Hawaiian soils in terms of their utility as predictors of P sorption. Chemical and physical properties associated with P sorption were measured and correlated. In addition, a theoretical quantity, potential P-sorption sites, was estimated from the mineralogical characteristics of the clay fraction. Rietveld refinement was used to determine the quantity of soil minerals. Crystallite size was determined by curve-fitting of selected x-ray diffraction peaks. These parameters were then used to predict the soil P-sorption potential by estimating the density of A-hydroxyl sites per gram of soil. This estimate of potential P-sorption sites provided the best correlation (R 2 = 0.94) with measured P-sorption capacity in 0.001 M CaCl 2 , which varied from 79 to 3280 mg P kg -1 soil at an equilibrium solution-P concentration of 0.2 mg P L -1 . Other bulk soil properties such as the moisture content at 1.5 MPa, specific surface area (glycerol retention), and the amount of amorphous (i.e., oxalate extractable) soil material, also correlated well with P sorption but yielded lower R 2 values. Clay content and soil chemical properties alone were not good predictors of P-sorption capacity across the full range of soils. Better estimates of the quantity of sorption sites, especially those contributed by amorphous oxides, would yield further improvements in this approach.

Phosphorus deficiency is a primary constraint to common bean (Phaseolus vulgaris L.) production in the tropics. Bean genotypes differ in their P efficiency, defined as growth and yield in low P soil. The objectives of this study were to evaluate genetic variation in diverse bean germplasm for P efficiency in soil types with contrasting P chemistry and to assess possible relationships between dry matter distribution, P partitioning, and yield. Experiments were conducted at two sites in Colombia, one an Andosol in which P availability is limited by allophane and recalcitrant organic matter and the other an Ultisol in which P availability is limited by Fe and Al oxides, with three levels of P fertilization. Twelve contrasting genotypes were evaluated for yield components, harvest index, and P partitioning. Genotypes yielded differently under P stress. Andean germplasm was often higher yielding under P stress than Mesoamerican germplasm but less responsive to added P fertility. Genotypic rankings for P efficiency did not differ in the two soil types. Reproductive parameters such as harvest index, yield components, and P allocation among plant parts at maturity were not related to P efficiency. We conclude that (i) there is no evidence for specific adaptation to low P availability in volcanic or mineral soils in beans; (ii) Mesoamerican and Andean genotypes respond differently to P availability; and (iii) vegetative and reproductive responses to low P availability are not always correlated. Further studies of P acquisition mechanisms related to root traits and efficiency of P use are warranted.

The spatial and temporal distributions of 17 elements in basaltic pyroclastic materials originating from Mt. Fuji, Japan, were investigated. The relatedness of the profiles was established tephrochronologically, which then allowed a comparison of the chemical compositions of the various weathered pyroclastic materials in terms of their spatial (distance away from the volcano) and temporal (older to younger deposits) relations. The distributions of mobile elements (e.g., Ca, Mg, Na, and Sr) and resistant elements (e.g., Ti) are strongly affected by the extent of weathering, which increases with time and increases with distance from the volcano (the effects of the thickness and specific surface area of parent material). The application of a few weathering indices based on chemical composition was successful. Furthermore, a principal component analysis statistically extracted the expected dominance of the element mobility-resistance, which accounts for 43% of the field-scale variability of the distribution of the 17 elements. The second principal component explained 21% of variability, and discriminated soils developed from similar parent materials but different weathering-soil-formation factors (agricultural activities and the impact of a river).

In order to assess the validity of conventional methods for measuring CO2 flux from soil, the relationship between soil microbial respiration and ambient CO2 concentration was studied using an open-flow infra-red gas analyser (IRGA) method. Andosol from an upland field in central Japan was used as a soil sample. Soil microbial respiration activity was depressed with the increase of CO2 concentration in ventilated air from 0 to 1000 ppmv. At 1000 ppmv, the respiration rate was less than half of that at 0 ppmv. Thus, it is likely that soil respiration rate is overestimated by the alkali absorption method, because CO2 concentration in the absorption chamber is much lower than the normal level. Metabolic responses to CO2 concentration were different among groups of soil microorganisms. The bacteria actinomycetes group cultivated on agar medium showed a more sensitive response to the CO2 concentration than the filamentous fungi group.

SUMMARY The sorption of sulphate (SO2−4) by three variable charge soils from the Canary Islands (Spain) was studied. Sulphate sorption decreased with increasing pH. Only negligible amounts of SO2−4 were sorbed above pH 6.5. When the soils were washed with an indifferent electrolyte (0.01 M KCl), more SO2−4 was recovered than had been sorbed. This indicated a release of native SO2−4 Sulphate replaced hydroxyl ions (OH) and co-ordinated H2O molecules, as well as very small amounts of silicate (Si). No measurable amount of phosphate (P) was released. On average hydroxyl release accounted for 50% of SO2−4 sorbed, the rest being accounted for by the increase in negative charge as measured by K+ adsorption. The results presented here are consistent with the sorption of SO2−4 through a ligand exchange mechanism, but in a different plane of sorption to that of phosphate.