Spodic Horizons Research Articles

Field Test for Spodic Character Based on pH‐Dependent Phosphorus Adsorption

AbstractA field method based on P adsorption is proposed for measuring the relative amounts of reactive organic Al in suspected spodic horizons. A soil sample to be tested is equilibrated by shaking with a pH 9.1 phosphate solution. If high in reactive Al, the sample will remove the P from the solution as indicated by the absence of blue‐colored molybdophosphate in the filtrate. Phosphorus adsorbed by soil samples under the test conditions was found to be correlated with Al extracted by pH 4.8 NH4OAc, but not by neutral KCl. It is suggested that soils be initially screened for presence of reactive hydroxy Al by testing with NaF and alizarin yellow, with the expressed caution that occasional high organic spodic horizons may give negative NaF tests.

Clay Mineral Genesis of Some New York Spodosols

AbstractSome Spodosols in northern New York previously shown to have well crystallized montmorillonite in the albic horizon but only amorphous clay sized material in the spodic horizon were studied to determine the source or genesis of the montmorillonite. The soils used to test several hypotheses of the clay mineral genesis represented Orthods, Humods, and Aquods. These soils were also shown to be deficient in mica and chlorite in the sand, silt, and clay fractions. This allowed a test of the hypothesis that montmorillonite in albic horizons weathers from mica, a process which previously has been reported to be active. The presence of only traces of mica and chlorite in the sand and silt fractions would indicate that weathering of sand and silt sized minerals directly to clay sized minerals should not be important. However, the small amount (generally less than 3%) of clay sized materials in the pedons makes this assumption inconclusive.Soil solution studies, coupled with equilibrium diagrams, provide evidence that clay mineral synthesis from ions does not occur in these soils.The well crystallized clay sized minerals detected in the upper solum of the pedons studied may have (i) weathered directly from sand and silt sized minerals, (ii) been added as dust, or (iii) weathered from minerals added as dust. There is recent evidence that appreciable amounts of montmorillonite, illite, vermiculite, and kaolinite are deposited as dust throughout the northern United States. If projected figures are valid, dust could account for most of the montmorillonite in the albic horizons studied. Concomitant additions of chlorite and mica are not detected. Chlorite and mica added as dust, as well as any traces of these minerals present as sand or silt, must be weathered to some other species in the clay fraction, because they are not detected in the clays.It is proposed that in the Spodosols studied (i) any chlorite in the albic horizon is weathered to amorphous aluminosilicates and translocated to the spodic horizon, and (ii) mica is weathered to montmorillonite in the albic horizon, to vermiculite in the Bh horizon, and to “chloritized” vermiculite in the Bir horizon.

PROPRIETES CHIMIQUES ET PHYSIQUES DE LA MATIERE ORGANIQUE NONDIALYSABLE EXTRAITE DE QUATRE PODZOLS DU QUEBEC

The physical and chemical properties of non-dialysable (>48 A) humic and fulvic fractions of four podzols from the Province of Quebec were studied. Extraction was made with 0.1 M sodium pyrophosphate. Analysis of the fractions showed that, in spite of a prolonged dialysis, considerable quantities of metallic ions remained bound to compounds of high molecular weights. The humic fraction showed, in general, a carbon and nitrogen content sensibly more even than the fulvic fraction. In the spodic horizon, humic fractions have a very similar carbon content. It is also in this horizon that are found the highest percentages of iron and aluminium. The distribution of the principal nitrogen compounds in each fraction was studied after acid hydrolysis. A great similarity in the distribution of the nitrogen was found, independently of its origin (horizon or profile). It has not been possible to find a relation between profiles, from the study of acid groups (carboxilic or phenolic). Absorption spectra with ultraviolet, visible, and infrared radiations were studied. The characterization of a profile from optical properties of high molecular weight fractions was particularly difficult, considering the great similarity between observed spectra. Differences in iron bound to the fulvic fraction were observed by means of electrophoresis. The behaviour of the humic and fulvic fractions towards H+ and Ca2+ ions was also studied.

The Morphology and Genesis of Some Alpine Soils in British Columbia, Canada: II. Physical, Chemical, and Mineralogical Determinations and Genesis

AbstractThe results of selected physical, chemical, and mineralogical analyses, carried out on five soils occurring in three alpine regions in British Columbia, Canada, are presented and discussed. An evaluation of the genesis of these soils is made in relation to the analytical results and to the literature.The soils have developed on relatively young post‐Pleistocene parent materials and are gravelly and have loamy sand to silt loam textures, in the fine earth fractions, the slight accumulations of silt and clay at the surface, are due primarily to more intense physical weathering and partly to surface additions of eolian material. Volcanic ash was found in the surface horizons at three of the sites.Physical weathering is significant in these soils and chemical weathering is taking place as evidenced by the presence of spodic horizons, abundant amorphous iron and aluminum in all horizons, and the content of secondary minerals.Several properties of these soils were correlated with total carbon contents and hence organic matter contents. Volcanic ash was believed to have had an influence, to a minor degree, on the soil properties where it occurred.With sufficient leaching, soils with spodic characteristics develop. Under a coniferous or ericaceous vegetative cover Spodosols occur; however, under a cover of grasses, sedges, and forbs the spodic characteristics may be masked by organic matter accumulations in the surface mineral horizons.

Electron microprobe analysis of plasma in an impervious horizon of a tropical groundwater podzol

The electron microprobe technique has been applied to resin-impregnated samples of the spodic horizon of a tropical groundwater podzol (Tropaquod) in Surinam. Chemical data are reported on the composition of small (25 × 25 μ) plasma areas. It appears that the lower the birefringence of a particular area, the lower is its SiO 2 Al 2O 3 ratio. The tentative conclusion is that the plasma has been derived from formerly illuviated clay by desilication in situ.

EXTRACTION DES ACIDES FULVIQUES D'UN HORIZON SPODIQUE PAR UNE RESINE ECHANGEUSE D'IONS DE TYPE H POSITIF

A resin in the H+ form (Dowex 50W-X8) was used to extract fulvic acids from a Spodic horizon. This resin has the following advantages in relation to the reagents normally used. It solubilizes organic matter while purifying it and without altering it by oxidation and hydrolysis. Furthermore, since the resin is eliminated completely from the extract, no contaminating ions remain. The soil was agitated in a mixture of water and resin. The extract obtained was filtered, centrifuged, purified by passage through a column of H+ resin and freeze-dried. The alternation of freeze-drying and resolubilization resulted in the coagulation of the silica which was removed by centrifugation. Acid organic matter with very low ash content (1%) was obtained. The fulvic acids extracted by resin and by Na-pyrophosphate were compared. Qualitatively they were practically the same, as evidenced by the similarity of the curves obtained by gel-filtration (Sephadex). Quantitatively the resin, however, was a more efficient reagent. Therefore, it is recommended for the extraction of fulvic acid and organo-mineral complexes.

The Characteristics, Classification and Genesis of Some Tropical Spodosols

AbstractMorphological, chemical, and mineralogical properties are presented for three tropical spodosols. Based on the occurrence in different climatic zones, the soils were distinguished as lowland podzols and mountain or highland podzols.The lowland podzol had a low organic matter content, a weakly developed Bh and a well developed argillic horizon below the spodic horizon. The name Humic Alfic Tropoferrod is proposed for this type of podzol. The A horizon contained predominantly amorphous clay, but the B horizon had appreciable amounts of kaolinite.Highland podzol I was high in organic matter, had a well developed Bh, but lacked an argillic horizon, and was classified as a Typic Tropohumod. Highland podzol II had similar properties, but was relatively young in degree of development and was classified as an Entic Tropohumod. The clay fraction of the humods was characterized by high amounts of amorphous clay, probably allophane. Kaolinite was not detected.

EXTRACTION ET REPARTITION DU FER ET DE L'ALUMINIUM LIES A LA MATIERE ORGANIQUE DANS QUATRE PODZOLS DU QUEBEC

When the selectivity of pyrophosphate as compared with dithionite and oxalate in the extraction of organo-metallic complexes had been established, the distribution of Fe and Al in humic and fulvic fractions of soil organic matter, before and after dialysis, was studied. A Podzolization index based on the amount of organo-metallic complexes of the spodic horizons was attempted.

Interaction entre la mobilite de plusieurs acides organiques et de divers cations dans un sol a mull et dans un sol a mor

An investigation has been made of the movement and transformations of the more abundant, low molecular weight organic acids encountered in soil and also of their effects on exchangeable cations. In soils with mull (humus) an abundance of exchangeable cations combined with vigorous biological activity favoured physico-chemical retention and decomposition in situ of organic acids and hindered their movement into the B horizon. In soils with mor (humus), especially those with a cold and wet climate, there was a pronounced movement of citric, oxalic and vanillic acids into the lower soil horizons during all seasons of the year whereas p-hydroxybenzoic and p-coumaric acids moved during the winter. Among these simple compounds, only the aliphatic acids were involved in the formation of complexes with iron and aluminium and the transport of these sesquioxides into the B h horizon. In the spodic horizon all the acids studied, whether aromatic or aliphatic were in part mineralized to carbon dioxide but a major proportion was incorporated into polymeric compounds.

Canopy Drip: A Source of Mobile Soil Organic Matter for Mobilization of Iron and Aluminum

AbstractLeaf leachates, simulating canopy drip during rainfall, were collected from southern red oak (Quercus falcata var. pagodaefoliz Ell.), live oak (Quercus virginiana Mill.), and longleaf pine (Pinus palustris Mill.), which were the principal tree species growing on soils with spodic horizons on the North Carolina Coastal Plain near Ft. Caswell. The samples of canopy drip were immediately chilled, filtered, and freeze‐dried. From the representative canopy drip sampled it was estimated that approximately 20 kg/ha per year of organic matter could be contributed to the soil from this source. In the laboratory, 139 to 1,480µ moles of Fe or 460 to 1,450µ moles of Al/g of freeze‐dried canopy drip were complexed from nitrate salt solutions depending on the concentration of the leachate solution. This amounts to a possible field mobilization of 0.15–1.53 and 0.22–0.70 kg/ha per year of Fe or Al, respectively.The active components responsible for Fe and Al mobilization were determined to be polyphenols, reducing sugars, and organic acids. Paper chromatograms and reducing‐sugar analyses indicated that the polyphenol and reducing‐sugar contributions to soil as canopy drip were approximately 1 kg and 4kg/ha per year, respectively. Organic acids were not quantitatively determined. Thus, canopy drip was shown to be an important source of mobile soil organic matter for podzolization and other pedogenic processes.

Use of Amorphous Material to Identify Spodic Horizons

AbstractThe illuvial amorphous material that occurs as pellets or grain coatings in the B horizons of some New York Podzols contains much carbon, iron, and aluminum. This amorphous material has high cation‐exchange capacity (CEC) that can be destroyed by heat treatment or extraction with solutions of a complexing agent (citrate or pyrophosphate) combined with a reducing agent (dithionite). Most of the carbon, iron, and aluminum of the amorphous material is removed with extracting solutions.The study included 19 New York soils, ranging from those with strong spodic horizons to those with cambic horizons. In the uppermost B2 horizon of each profile, the CEC loss caused by 240C heating is highly correlated with total organic carbon (r=0.99), with the amount of carbon extracted (r=0.98), and fairly well correlated with the amount of iron plus aluminum extracted (r=0.88). The degree of Podzol development, as judged in the field, is related to the loss of CEC caused by heating or extraction, and also to the amounts of carbon, iron, and aluminum extracted. These relationships are used as the basis for proposed quantitative limits that would separate spodic horizons from cambic and other diagnostic horizons.

On soil genesis in temperate humid climate. V. The formation of the "albic" and "spodic" horizon.

With the aid of parahydroxybenzoic acid as a model substance, some suggestions are given on the formation of the albic and spodic horizons under well-aerated conditions in very poor and acid parent materials. The acid forms soluble complexes with Fe, while insoluble compounds are formed with Al. The stability constants of the Fe complexes and the solubility product of the Al complex were determined. Hydrolysis of the Fe complexes formed in the A horizon, and formation of an insoluble Al complex are the most important mechanisms in the formation of the B2ir and B2h horizons, respectively. (Abstract retrieved from CAB Abstracts by CABI’s permission)

On soil genesis in temperate humid climate. IV. The "low humus podzols".

"Low humus podzols" do not possess a spodic horizon; podzol formation in conjunction with predominantly reducing conditions give rise to an eluviated profile. Low humus podzols have an umbric epipedon, the Fe and Al contents of the B horizon are intermediate between those of the A and C horizon, and their humus is mostly dispersed. Psammic Umbraquepts is proposed as a fifth subgroup for these soils. (Abstract retrieved from CAB Abstracts by CABI’s permission)