Human-altered and human-transported (HAHT) soils in the U.S. soil classification system

ABSTRACT

Human-altered and human-transported (HAHT) soils are widespread across the globe and are concentrated near where people live and work. Although some of the HAHT soils are significant because they can be hazardous to human, animal, and plant health, most are not mapped or classified to the same extent as agricultural soils. The purpose of this article is to discuss the occurrence, types, and importance of HAHT soils and to document the historical and proposed classification of HAHT soils in Soil Taxonomy. There are two main forms of materials that define HAHT soils: human-altered soils formed in human-altered materials (HAM) from the soil surface to 50 cm (or to bedrock if shallower) or more and human-transported soils formed in human-transported materials (HTM) from the soil surface to 50 cm (or to bedrock if shallower) or more. The HAHT soils mainly occur in urban areas, transportation corridors, mined lands, landfills, filled shallow water, and agricultural areas on anthropogenic landforms. Hazards include danger from radioactivity, pollution, content of hazardous artifacts, or presence on unstable landforms that may fail during heavy rains or earthquakes. The HAHT soils are extensive, and their extent is growing. In the past, few HAHT soils were described or classified adequately because the U.S. Soil Taxonomy system was established for agricultural and other naturally occurring soils. However, HAHT soils are now being recognized and classified in many soil classification systems at very high levels. A new soil order is proposed for U.S. Soil Taxonomy that would include the most obvious profoundly and intentionally altered HAHT soils. A discussion and justification is given for an unofficial proposal. Input will be collected from international groups of scientists, and modifications of the unofficial proposal are expected. The long-term result of establishing a new soil order will be to enable proper classification, allocation, and mapping of HAHT soils worldwide.     

Potassium fixation in suspensions of soils of Galicia (N.W. Spain)

Abstract

Potassium (K) fixation in soils treated with K‐rich fertilizer is important in limiting leaching of this ion, and thus the risk of high salinity in waters. We studied this capacity for aqueous suspensions of a group of soils of Galicia (N.W. Spain) and found that fixation increased with K dosage, increased slightly with contact time, and decreased with increasing temperature (between 3 and 40°C). Potassium fixation was barely influenced by the mineralogy of the clay fraction but was greater in soils with greater fine particle content. Modified Freundlich equation successfully modelled the effects of K addition, temperature, and contact time on fixation. The influence of temperature was greater in illitic soils than in mixed soils. The results indicate that Galician soils have little capacity for K fixation.     

CROSS POLARISATION 13C-N.M.R. SPECTROSCOPY OF SOME GENETICALLY RELATED NEW ZEALAND SOILS

Cross polarisation ¹³C-n.m.r. spectra of seven New Zealand soils have been determined. Some of the soils are genetically related. The results show that the aromaticity of a soil may vary widely from soil to soil even when the parent material and vegetation are similar. The youngest of the soils examined (Hokitika, 300 years), was highly aromatic, and the oldest soil (Okarito, 22,000 years) was more aliphatic.     

REACTIONS OF AMMONIA WITH SOIL. I

Heats of adsorption and adsorption isotherms of ammonia gas were measured at 300 K (27 °C) on outgassed soil saturated with Na⁺, K⁺, NH₄⁺, Ca²⁺, or Mg²⁺ ions. The Ca and Mg soils adsorbed apparently one more NH₂ molecule per exchangeable ion than the Na and K soils, mostly in the relative pressure range o to 0.005, but not much more than the NH₄ soil. The initial heat of adsorption was c. 75 kJ mol^-1 on the Ca and Mg soils and c. 60 kJ mol^-1 on the other soils. The results suggest that most NH, is sorbed on these soils through reactions not involving exchangeable cations.     

Distribution of four major forms of potassium in soils of Galicia (N.W. Spain)

Abstract

The potassium (K) status of a group of Galician natural soils was evaluated, and the equilibria between the four main K forms were examined. The results indicated that the Galician soils studied contained a large mineral K fraction (97% of total K), and a smaller fraction of labile K forms, composed of non‐exchangeable (2%), exchangeable K and solution K (1%). For these soils, the exchangeable K was 38% of the non‐exchangeable K, which was consistent with the moderate development of these soils. The equilibrium between solution K and exchangeable K was displaced towards solution K.     

Temporal Trends in Ca,Mg and K Concentrations of Grassland and Garden Soils in West Virginia,U.S.A. between 1986 and 1999

The effects of acidic deposition on agricultural soils have not received much attention because they are regularly limed and receive acid forming fertilizers far in excess of what would accumulate in these soils from atmospheric acidic deposition. However, not all agricultural soils are managed with equal intensity, and some may be prone to element specific effects from acidic deposition. Using data from the West Virginia University Soil Testing Laboratory and the National Atmospheric Deposition Program,it was found that soil Mg concentrations were decreasing up to 2.6% yr^-1 in hay and pasture soils where acidic deposition was the highest. Rainfall amounts and biomass removaldid not appear to be related to this effect. By comparison, no trends in Mg depletion with acidic deposition were found for the more intensely managed home garden soils. Nor were there regional trends in Ca or K for either hay and pasture or home garden soils. While the correlation Mg depletion and acidic deposition does not in and of itself indicate causality, it does suggest the Mg status of unmanaged or moderately managed grasslands may be adversely affected by acidic deposition.     

The Effect of Fire on Mercury Cycling in the Soils of Forested Watersheds: Acadia National Park,Maine, U.S.A.

This study compares mercury (Hg) and methylmercury (MeHg) distribution in the soils of two forested stream watersheds at Acadia National Park, Maine, U.S.A. Cadillac Brook watershed, which burned in 1947, has thin soils and predominantly deciduous vegetation. It was compared to the unburned Hadlock Brook watershed, with thicker soil and predominantly coniferous vegetation. Soils in both watersheds were primarily well drained. The fire had a significant impact on the Cadillac watershed, by raising the soil pH, altering the vegetation, and reducing carbon and Hg pools. Total Hg content was significantly higher (P > 0.05) in Hadlock soils (0.18 kg Hg ha^-1) compared to Cadillac soils (0.13 kg Hg ha^-1). Hadlock O horizon had an average Hg concentration of 134±48 ng Hg g^-1 dry weight, compared to 103±23 ng Hg g^-1 dry weight in Cadillac O horizon. Soil pH was significantly higher in all soil horizons at Cadillac compared to Hadlock soils. This difference was especially significant in the O horizon, where Cadillac soils had an average pH of 3.41±0.22 compared to Hadlock soils with an average pH of 2.99±0.13.To study the mobilization potential of Hg in the O horizons of the two watersheds, batch adsorption experiments were conducted, and the results were modeled using surface complexation modeling. The results of Hg adsorption experiments indicated that the dissolved Hg concentration was controlled by the dissolved organic carbon (DOC) concentration. The adsorption isotherms suggest that Hg is more mobile in the O horizon of the unburned Hadlock watershed because of higher solubility of organic carbon resulting in higher DOC concentrations in that watershed.Methylmercury concentrations, however, were consistently higher in the burned Cadillac O horizon (0.20±0.13 ng Hg g^-1 dry weight) than in the unburned Hadlock O horizon (0.07±0.07 ng Hg g^-1 dry weight). Similarly, Cadillac soils possessed a higher MeHg content (0.30 g MeHg ha^-1) than Hadlock soils (0.16 g MeHg ha^-1). The higher MeHg concentrations in Cadillac soils may reflect generally faster rates of microbial metabolism due to more rapid nutrient cycling and higher soil pH in the deciduous forest. In this research, we have shown that the amount of MeHg is not a function of the total pool of Hg in the watershed. Indeed, MeHg was inversely proportional to total Hg, suggesting that landscape factors such as soil pH, vegetation type, or land use history (e.g., fire) may be the determining factors for susceptibility to high Hg in biota.     

AVAILABILITY OF POTASSIUM TO RYEGRASS FROM SCOTTISH SOILS I.

Scottish soils were cropped with two sowings of perennial ryegrass (Lolium perenne, cv, Dutch Barenza) in the glasshouse, without addition of potassium, until growth virtually ceased. Potassium uptake and the corresponding changes in soil K properties were examined. Uptake of K correlated well over the entire cropping period with the initially labile K predicted from the Q/I isotherms of the soils, although K uptake was at least a factor of 1.9 greater than the initially labile K. The Q/I isotherms were similar for soils from the same series, and the form of the lower part remained virtually unchanged during intensive cropping. The equilibrium activity ratio, AR₀, of soil K measured in 0.01 M calcium chloride was reduced in all soils to a narrow range close to a mean value of 3 × 10 ^?4 M^1/2. Drying-and-wetting fresh soil samples severely depleted of ryegrass-available K raised their K status. The increases were negatively correlated with the percentage K saturation of the fresh depleted soils, and a K saturation of 1.4 per cent must apparently be left in the fresh cropped soils for no K to be released. Freezing-and-thawing did not affect the K status of these soils.     

衡山土壤之研究

在阐述衡山土壤形成条件的基础上，重点阐明了衡山各类土壤的性质特征和土壤垂直分布规律、并根据诊断土层和诊断特性，对其进行系统分类。衡山土壤分布自下至上依次为湿润富铁土、黄色湿润富铁土、常湿富铁土和常湿淋溶土。在各山峰顶部和陡坡处，分布有酸性常湿雏形土。     

Colluvisols under cultivation in Schleswig-Holstein. 1. Genesis,definition and geo-ecological significance

In Schleswig-Holstein, F.R.G., two typical soil associations from loamy boulder marl and loamy pleistocene sands were mapped and ecologically characterized in order to show the necessity of an adequate classification of Colluvic Cumulic Anthrosols (Colluvisols). More than 50% of the original soils have been altered by erosion. The depth of the colluvic wM horizon ranges between 10 cm and more than 100 cm. The amounts of soil organic matter and plant available nutrients are much higher in the Colluvisols than in the haplic soils. Soil classification does not deal with all these aspects with regard to mapping of colluvic soils. In the German soil classification adequate and ecologically significant definitions and instructions of the nomenclature of colluvic soils are not available. Therefore, a proposal is presented to classify colluvic soils. In addition the threshold value of 0.6% soil organic matter in sandy parent material is too low in order to distinguish a Bv from a M horizon; 1.0% would be a more acceptable value. It would be necessary to investigate yield on erodic, non-erodic and colluvic soils in order to determine the effect of erosion and accumulation on crop yield.     

Aggregation in soils with small amounts of swelling clays. I. Aggregate stability

The respective role of organic materials and poorly-ordered Al and Fe hydrous oxides on soil aggregate stability was studied in silty soils with little swelling clay, using both multivariate analysis and physico-chemical approaches. Soil disaggregation is a function of the hydrophobic character of organic matter (OM), which depends on the nature of the organic materials, cationic environment and the aggregating effect of Al and Fe hydrous oxides.
Two kinds of aggregates >50 μm can be distinguished in organic soils, one being about six times more stable than the other. In soils poor in organic matter, weak aggregates dominate; the binding agents are Ca or Al OM rich in polysaccharides and peptides.     

Rice cultivation and its environmental conditions in the Mediterranean countries II. Soils,their fertility and mineralogy

In Italy paddy aolls have a broad varfability with respect to region and age of the parent material. The regional characteristics, however, predominate over the age relations, i.e., the Po delta soils have higher potentialities than the youngest of those in the middle reaches of the Po. Among soils of the middle reaches the older the parent material, the more depleted the bases. Some of the better drained terrace soils have the morphology of “aquorizem.”

Spanish paddy soils along the Mediterranean coast are all alike, having an alkaline reaction due to the presence of free lime, and SiCL to SiC textures. Morphologically there are two types of paddy soils, one having gleyed subsoils due to groundwater influence, and the other having brown subsoils below strongly gleyed aurface soils under aubmergence.

Portugese paddy soils are generally similar to Spanish soils both in mode of occurrence and In nature, except for neutral to slightly acidic reaction and absence of free lime in the former.

The general soil potentiality aa judged from chemical and mineralogical atudies is in the order of Spanish>Portugese>Italian paddy aoils.     

Soils affected by acid mine waters in galicia (N.W. Spain)

Contaminated soils and surface waters, from copper mining in Galicia, are acidic, high in sulphate and increase appreciably in the concentration of elements such as Al, Fe, Ca, Mg, K, Mn, Cu and Zn by contact with soils and fragments of rock of an amphibolic composition. Application of activity data to mineral equilibrium diagrams illustrates the instability of Al-hydroxides and aluminosilicates compared to Al-sulphates of the alunite and jurbanite type, in the waters which are most acid and display sulphate activities close to 10^?2 M. The solution extracted from soils around the spoil heaps reflects the strong influence of the most heavily contaminated run-off waters, with little or no buffering by the solid phase. This aspect may be accounted for by both a brief time of residence and a real decrease of the acid buffering power of these soils, whose primary minerals undergo strong acidolysis. Neoformation of Al-sulphate (and Fe-sulphate) is observed both in soils and in the channels of the contaminated streams, above all the points of contact with non-acid or slightly acid waters.     

Addition of phosphorus to soils with low to medium phosphorus retention capacities. I. effect on soil phosphorus sorption properties

Abstract

Twelve soils with low‐medium phosphorus (P) retention capacities were equilibrated for 3 months with soluble phosphate at a rate of 100 mg P kg^‐1 soil. The P sorption properties of these soils both with and without added P were studied, including equilibrium P concentration (EPCo), standard P requirement (SPR), soil P sorption capacity (b), maximum buffer capacity (MBC), and P sorption index (P‐SI). In general, the soils with no added P showed low values of all the above parameters. Oxalate extractable aluminum appeared to be the major responsible element for the control of P sorption in these soils. The addition of P to these soils had a considerable effect on their P sorption properties. The changes in EPCo were well correlated with P sorption index (r=0.80; p≤0.01 ). The EPCo values of the soils with and without added P were closely correlated to bicarbonate extractable P (P_0lsen) and calcium chloride extractable P (P_CaC12), with r=0.80, and r=0.99 (p≤0.001), respectively. Ninety percent of the variability in EPCo was explained by the corresponding variability in P_Olsen when a curvilinear relationship was adopted. The P sorption properties examined appear to be useful parameters to assess the environmental impact of soil P on the quality of surface waters.     

100 Years of Pb Deposition and Transport in Soils in Champaign,Illinois, U.S.A.

In Illinois, atmospheric deposition is one major source of heavy metal inputs to agricultural land. The atmospheric Pb deposition and transport record in agricultural soils in Champaign, Illinois, was established by studying surface and subsurface soil samples collectedduring the past 100 years from the Morrow Plots on the campus of the University of Illinois at Urbana-Champaign. The Pb content in the soilsamples was measured and the Pb deposition fluxes were calculated. ThePb content in surface soils increased sharply in the first half of the20th century, and stayed invariant since. The maximum Pb flux from theatmosphere was estimated to be 27 (±14) μg cm^-2 yr^-1around 1940. The major pollution source for this increase probably was residential coal burning. It was estimated that in 50 yr, morethan 50% of the Pb input had been lost from the surface soils.     

Effect of grinding on the decomposition of soil organic matter—I. The mineralization of organic nitrogen in relation to soil type

The effect of grinding on aerobic nitrogen mineralization in ten soils of widely different properties was studied. The aerobic mineralization of nitrogen was increased in seven of ten soils when they were ground to < 0.18 mm and < 0.05 mm; these seven soils contained more clay than the other three soils. Five soils with montmorillonite clay showed larger proportional increases in mineralization due to grinding than did the two soils with kaolin clay. The implications of these findings are discussed in terms of the inability of some previous workers to find increases in the rate of organic matter decomposition when soils are physically disrupted and the importance of clay protection in the resistance of soil organic matter to decomposition.     

Schätzung der Denitrifikation in landwirtschaftlich genutzten Böden. II. Ergebnisse und Bewertung

Estimating denitrification in agriculturally used soils: II. Results and evaluation This is the second of two papers describing a denitrification model. Whereas in the first paper the model approach was described, the second paper deals with results obtained with the model. To evaluate the model's performance, 14 profiles in the catchment area of a water-work were studied in detail. For each site the potential and the actual annual denitrification rates were estimated. It was found that the least favorable conditions for denitrification occurred in the sandy soils of the study area. Consequently, estimated denitrification rates were lowest (< 10 kg N ha^?1 a^?1) in these soils. Estimated denitrification rates were highest (50 kg N ha^?1 a^?1) in peal and river plain soils, with either a high amount of organic matter and/or a high groundwater table. In silty loess soils, denitrification losses were estimated to be 20 to 35 kg N ha^?1 a^?1. With use of the anion concentrations in the surface layer of the groundwater, a plausibility study was conducted to evaluate the estimated denitrification losses. Its results show that the values obtained are realistic. However, a true calibration of the model is still necessary.     

Mikrobiologische und biochemische Charakterisierung landwirtschaftlich genutzter Böden. II. Mitteilung. Beziehungen zum Humusgehalt

Microbiological and biochemical characteristics of agricultural soils Part. II. Relations to the organic matter content A soil microbiological index for 33 tested samples of 11 agricultural soils with different origin and management history was correlated with the corresponding organic carbon content. The soils tested showed a highly significant correlation coefficient (r = 0.93) between the microbiological index and the total organic carbon content. According to our working hypothesis, there seems to be a connection between the quotient which is derived from the microbiological index and humus content to the turnover of organic matter in soils. In individual soils or groups of soils the deviations from the general function calculated from all tested soils are not caused by errors in the analytical procedure. They seem to indicate changes in the humusstatus (intensity of humus synthesis or humus decomposition) occuring during the time of investigation.     

土壤中积累态磷活化动力学的研究Ⅰ.有机质的影响

研究了潮土和红壤中积累态磷的活化动力学及其有机质的影响。四种动力学方程均能很好地描述积累态磷的活化。用H2 O2 去除有机质加快了潮土中积累态磷的活化 ,对红壤影响不明显。施加 2 %葡萄糖培育促进了红壤中积累态磷的活化 ,对潮土影响不大     

Studies on the mechanisms of fixation and release of ammonium in paddy soils after flooding. I. Effect of iron oxides on ammonium fixation

Experiments were conducted with two typical paddy soils from China and a vermiculite to study the influence of iron oxides on the fixation and release of ammonium. Removing iron oxides, especially amorphous iron oxides, from the soils favoured the release of non-exchangeable NH₄-N and stimulated the fixation of NH₄-N in the presence of added (NH₄)₂SO₄. Addition of artificial goethite and hematite to the original soils or to the soils free of iron oxides reduced the fixation of NH₄⁺-ions. This effect was also observed with vermiculite. We conclude that the coating of clay minerals with iron oxides has an impact on the diffusion of NH₄⁺-ions into and out of the interlayers of the clay minerals. The reduction and dissolution of iron oxides induced by low redox potential (E_h) after flooding of paddy soils is assumed to be an important mechanism controlling NH₄⁺-fixation in paddy fields.