花岗岩风化产物中高岭石和埃洛石的粒径分布及其对土壤发生的意义

The kaolins collected from a profile of weathered granite at Yichun County, Jiangxi Province have been subjected to particle size fractionation by the conventional sedimentation method and examined by XRD, SEM and TEM. All of them exhibit a mixture phase of poorly crystallized kaolinites and halloysites (0.7 nm) occurring as the main clay minerals. Electron micrographs reveal that plate kaolinites are the principal constitution in the coarse fraction, and more tubular and curled halloysite (0.7 nm) in the fine fraction. Both of them show normal probability curves in particle size distributions. The ratios of kaolinite and halloysite (0.7 nm) in different size fractions are examined by X-ray diffraction with a series of X-ray patterns characterized by three main peaks at d(001), d(002) and d(020),varying in intensity. Therefore, an index Q_hm expressed as (I_d(001) + I_d(002))/(2×I_d(002)), is designed to indicate relative ratios of the two clay minerals in a number of mixture phases. Because kaolinite and halloysite (0.7 nm) commonly occurred, respectively, in low and medium leaching microenvironment, the index Q_hm, can be used to indicate weathering and pedogenic conditions of a weathering crust.     

Paleosols of the southern coastal plain of Israel

Paleosols of the S coastal plain of Israel were studied in a characteristic sequence situated in the Ruhama badlands area. At the upper part of the sequence, there is a Loessial Arid Brown Soil (Calciorthids), characteristic of the mildly arid climate of the area. The soil has two calcic horizons and four clayey layers alternating with four calcareous layers which are beneath them. Physical, chemical, and magnetic‐susceptibility data and micromorphological evidence indicate that each clayey layer together with the calcareous layer beneath it forms a single pedogenic unit. These units are similar to modern Grumusolic soils (Xeric Paleargids or Xererthic Calciargids) that occur in the semiarid belt of the S coastal plain and develop on eolian‐dust parent material. The calcareous layers are in fact calcic horizons formed by leaching of the carbonates from the clayey layers and accumulated in the form of in situ carbonate nodules. The leaching of the carbonates is not complete; they were never completely leached in the past. This feature together with a typical brown color is also characteristic of the modern soils developed in the semiarid water regime of the area. The four superimposed paleosols represent four cycles. It is suggested that they were formed in two phases. During a dry environment, a short phase of rapid eolian‐dust accumulation prevailed, followed by a stable phase of soil development in a somewhat wetter climate. Dating by optically stimulated luminescence and previous dating by ¹⁴C in the area suggest that the upper two paleosol cycles belong to the Last Glacial period whereas the other two cycles are of an earlier age. The magnetic‐susceptibility values decrease with age and react different from temperate areas. Below the four cycles, two totally leached paleosols developed on sandy parent material occur. Both paleosols have a reversed magnetic polarity and are hence older than 780 ky BP. The upper one is a Brown Mediterranean soil, and the lower one is a Red Mediterranean soil. Thin‐section evidence suggests that they formed on terrestrial sand dunes.     

Soil penetrating quality in cultivated and forested coastal plain sands of Southern Nigeria

Conversion of natural forest to intensive cultivation makes to soil susceptible to flooding, declining fertility and loss of organic matter (OM) and reduced water movement into and within the soil. We studied infiltration rates and related soil penetrating indicators of forested and cultivated soils in humid tropical coastal plain sands in Southern Nigeria. Results showed that mean-weight diameter (MWD) and water stability of aggregates were higher in forested than cultivated soils. Stable aggregates > 1.00 mm were 16.5% and 31.1% respectively, for cultivated and forested soils at 0–15 cm depth, indicating formation of more macro-aggregates in forested soil. Soil disturbance through cultivation decreased hydraulic conductivity and increased bulk density of the soil. Infiltration rate attained after 2 hours was higher in forested soil. Temporary infiltration rate of 178 mm hr^?1 at initial time in cultivated soil was followed by very low infiltration rate of 7 mm hr^?1 after 2 hours. Soil organic matter (SOM), saturated hydraulic conductivity, MWD and total sand correlated positively with infiltration rates are r = 0.76, 0.61, 0.57 and 0.51 respectively. Changes in these parameters are dependent on surface soil disturbance by cultivation. Cultivation of forest decreased infiltration rates and water transmission properties of the soil.     

Distribution of iron oxides forms on a transect of calcareous soils,north-west of Iran

The iron oxides fractions of four major physiographic units obtained from a transect of calcareous materials were studied to assess the effects of key pedogenic processes and local hydrology conditions as well as physiographic units in controlling iron oxides forms in the north-west of Iran. Samples from different horizons belonging to six pedons were selected and analyzed for soil physicochemical properties, clay minerals, and Fe oxides forms (Fe_d, Fe_o, Fe_p). In general, the soils indicated some variation in the concentration of iron oxides that could be related to rate of weathering, pedogenic accumulations, geomorphologic conditions (as results of different in physiographic units), wet and dry cycle, and organic matter. A wide relative variation in mean values of Fe_d (6.4–9.9 g kg^?1), Fe_o (2.9–4 g kg^?1), and Fe_p (0.68–1.3 g kg^?1) was observed among physiographic units. On the plateau unit, the presence of the most stable geomorphologic conditions and high rate in situ weathering (reflected in clay content), coupled with minor deposition of sediment suggest that the soils have more dynamic conditions than other units, reflecting in the greatest amount Fe_d and the lowest Fe_o/Fe_d ratio. Fe_d content of the soils containing less clay content (15–25%) was significantly different from those with greater clay content (25–35%).     

Relationships among soil p test values for soils of differing pedogenesis

Abstract

Surface samples of 78 soils from the continental U.S. and Puerto Rico were obtained from the U.S. Soil Conservation Service National Soil Survey Laboratory. Phosphorus was extracted by the Bray PI (0.03N NH₄F in 0.025N HCl), Mehlich No. 1 (0.05N HCl in 0.025N H₂SO₄), and Olsen bicarbonate (0.5N NaHCO₃) tests. Soil chemical, physical, and taxonomic data were obtained from the National Soil Survey Laboratory. On the basis of soil taxonomy and weathering, soils were divided into calcareous, slightly weathered, and highly weathered groups. Linear regression analysis was used to compare obtained soil P test values. Coefficients of determination (r²) ranged from 0.30 to 0.89. The lower coefficients were obtained between Mehlich No.l and Olsen bicarbonate tests, as these extractants were developed for differing soil types. Using independent data sets, the regression equations provided accurate estimates of soil test P by one method from another.     

The effects of flue gas desulfurization gypsum (FGD gypsum) on P fractions in a coastal plain soil

Purpose

In order to explore the possibility of using FGD gypsum in controlling P loss due to agricultural runoff, the effects of FGD gypsum on the P fraction were studied in the Yangtze River Delta coastal plains. The field experiments were conducted to identify (1) different application rates of FGD Gypsum to the P losses and (2) formation of Ca-P complexes in the soil in response to FGD gypsum applications.

Materials and methods

The field experiments consisted four rates of FGD gypsum (0, 15, 30, and 45 t/ha) in triplicate. FGD gypsum was obtained from a coal burning power plant. The “S” multi-point sampling method was used to collect samples of the uppermost soil interval in July and December of 2015. The total phosphorus (TP) in soil and plants was determined using the sulfuric acid-perchloric acid digestion method. The available phosphorus (AP) was determined using the sodium bicarbonate extraction-molybdenum-antimony anti-spectrophotometric method. The soluble reactive phosphorus (SRP) in the soil leachate was determined using the molybdenum-antimony anti-spectrophotometric method. The Visual MINTEQ 3.0 model was used to simulate the forms and distribution of the P fractions in the soil solution.

Results and discussion

The results indicated that the soil P fractions changed with application rats of FGD gypsum while the total soil P showed no significant change. The concentrations of SRP in the leachate also decreased in average of 27.5, 41.9, and 54.5%, respectively, with increasing FGD gypsum rates. The amounts of Ca₂-P, Ca₈-P, and Ca₁₀-P of the calcium phosphates in the soil were significantly increased over the ranges of 44.3–68.6, 34.1–70.1, and 7.4–17.2%, while soil AP concentrations decreased. Visual MINTEQ modeling confirmed the speciation and fractionation of Ca-P compounds under the coastal plain soil conditions. The field experiments also showed that FGD gypsum applications did not affect the absorption of P by the vegetation.

Conclusions

Experiments indicated that FGD gypsum has been shown to react with P in soil, resulting in decrease of AP and SRP and formation of insoluble Ca-P compounds and thereby decreasing the potential of P losses with surface runoff. FGD gypsum appears to be a more viable soil amendment than commercially mined gypsum to potentially achieve reductions in P losses and eutrophication of receiving waters.

     

Retention of dissolved organic matter by illitic soils and clay fractions: Influence of mineral phase properties

The dependency of the retention of dissolved organic carbon (DOC) on mineral phase properties in soils remains uncertain especially at neutral pH. To specifically elucidate the role of mineral surfaces and pedogenic oxides for DOC retention at pH 7, we sorbed DOC to bulk soil (illitic surface soils of a toposequence) and corresponding clay fraction (< 2 μm) samples after the removal of organic matter and after removal of organic matter and pedogenic oxides. The DOC retention was related to the content of dithionite‐extractable iron, specific surface area (SSA, BET‐N₂ method) and cation exchange capacity (pH 7). The reversibility of DOC sorption was determined by a desorption experiment. All samples sorbed 20–40 % of the DOC added. The DOC sorption of the clay fractions explained the total sorption of the bulk soils. None of the mineral phase properties investigated was able to solely explain the DOC retention. A sorption of 9 to 24 μg DOC m^–2 indicated that DOC interacted only with a fraction of the mineral surface, since loadings above 500 μg m^–2 would be expected for a carbon monolayer. Under the experimental conditions used, the surface of the silicate clay minerals seemed to be more important for the DOC sorption than the surface of the iron oxides. The desorption experiment removed 11 to 31 % of the DOC sorbed. Most of the DOC was strongly sorbed.     

Leaching of heavy metals from sewage sludge through coastal plain soils

Abstract

Three types of sewage sludge are applied to the surface of soil columns of Coastal Plain soils and leached with distilled water. The Zn concentrations in leachate samples from a Sassafras loamy sand soil loaded with an industrial sludge increased with sludge loading rate. All leachate samples contained very low concentrations of Cd, Cr and Cu. Hazardous amounts of Cd, Cr, Cu and Zn would not be leached to the groundwater when recommended rates of the tested sludges are applied to Coastal Plain soils under most conditions.     

Cation exchange capacity and base saturation of imperfectly drained surface coastal plain soils

Abstract

Testing three imperfectly drained forest soils (Alfisols and Ultisol) by nine methods showed that cation exchange capacities were highly pH dependent. Adding lime increased CEC values obtained by buffered and unbuffered methods but decreased CEC values when total bases were added to total acidity or salt replaceable acidity. No method tested completely explained the change in CEC caused by liming. Fractionation of the whole soil CEC Indicated an appreciable masked charge caused by an apparent complexing of amorphous metal oxides with clay or organic matter. In both buffered and unbuffered solutions, calcium saturation usually gave higher CEC values than monovalent ion saturation.     

类似但成土因素不同的土壤：巴西始成土的趋同演变

Soils result from the interaction of five independent formation factors.If one factor varies,while the others remain constant,different soils can be produced.Herein,we demonstrated an opposing trend,wherein two soils were similar,despite considerable differences in all factors of soil formation.We sampled two Inceptisols (Oxic Dystrudepts) formed on different parent materials (gneiss vs.mica schist),climate (tropical altimontane vs.warmer,drier plateau),topography (1 650 m,45％ slope vs.1000 m,8％ slope),time (rejuvenated vs.old,stable surface),and vegetation (rainforest vs.Cerrado savanna).The two soils had similar chemical properties,whereas the soil on mica schist had finer particle size distribution,lower porosity,and lower saturated hydraulic conductivity.These properties were related to a coarser blocky microstructure compared to the soil on gneiss.Both soils presented active mineral weathering and pronounced pedoplasmation,demonstrated by clay contents ＞ 300 g kg-1,although only the Dystrudept on gneiss possessed coarse rock fragments.The C horizons of both soils presented fragmented clay coatings suggestive of argilluviation,likely relict,because they were not observed in the B horizons.The similarities in many properties of the two Dystrudepts,despite contrasting factors of soil formation,suggest converging evolution and that soil classification at the subgroup level was efficient in grouping similar formative processes in tropical conditions.Moreover,this work revealed that similar pedogenic processes acting on different factors of soil formation can result in similar soil properties,at least for Inceptisols where further soil development is hindered by topographic limitations.     

A rapid method of evaluating the zinc status of coastal plain soils

Abstract

A study was made to evaluate Zn removed by extraction with a 0.075 N acid mixture (0.05 N HCl + 0.025 N H₂SO₄). A ratio of soil to extracting solution of 1 to 4 and an extracting time of 15 minutes was selected. Data obtained by the method was significantly correlated with dithizone (0.01%) extraction. The method was found to be acceptable for evaluation of the Zn status of Southern Coastal Plain soils and easily adapted to routine use in soil testing. A significant correlation was obtained between extractable soil Zn and leaf blade content of Zn for Zn‐deficient and non‐deficient corn plants.     

Yield of corn as affected by potassium on a coastal plain soil

Abstract

Corn (Zea mays L.) yields were determined over a four year period on Kalmia sandy loam soil at Georgetown, Delaware. Yields were not significantly increased by the application of K fertilizer. Potassium soil test level was not significantly correlated with corn yield. Multiple extraction and leaching and changes in soil test K indicated that this soil has a K equilibrium which is reestablished sufficiently rapid to supply K to a growing corn crop.     

The PAH and organic content of sediment particle size fractions

A comparison of declining forests in Alaska, British columbia, and the Pacific Northwest United States to forest declines in eastern North America indicated that strong similarities existed and justified the use of the western forest region as an ‘acid rain’ control. The current level of wet acidic deposition over the western region was one-quarter that of eastern Canada and the United States. The onset of crown dieback on Chamaecyparis nootkatensis (1900) and Pinus monticola (1936) did not relate to the incidence of regional air pollution but to extreme climatic variation. The injury mechanism differentiating persistent decline on Pinus monticola from sporadic but transient dieback, which was observed on a larger number of conifer and deciduous tree species, was believed to be cavitation. This dysfunction of the xylem was induced by anomalous winter thaw-freeze conditions in 1936 followed by high summer temperatures and evapotranspiration stress in that and subsequent years. Similar extreme climatic conditions were present at the onset of forest declines in eastern North America and central Europe which suggests that the climate-cavitation-forest decline mechanism may be universal.     

Chemistry of soil potassium in Atlantic coastal plain soils: A review

Abstract

Literature dealing with general properties of soil K and with K relationships in Atlantic Coastal Plain Soils was discussed. Potassium, among major and secondary nutrient elements, is the most abundant in soils. It, among mineral cations required by plants, is largest in non‐hydrated size. Potassium has a polarizability equal to .88 ų and a low hydration energy of 34 kcal g^?1 ion^?1. The major K forms in soils are water soluble, exchangeable, nonexchangeable, and mineral. Various dynamic interrelationships exist between these forms with the reaction kinetics between the various phases determining the fate of applied K.

Many Atlantic Coastal Plain soils contain high levels of total K. Most of the total K in these soils is contained in mineral forms such as micas and K‐feldspars. These K forms are slowly released to solution and exchangeable forms that are available to plants. Many researchers have noted a lack of crop response to K fertilization on Atlantic Coastal Plain soils. This lack of response has been ascribed to the high indigenous levels of mineral and non‐exchangeable K in the soils which would become available to crops. Some researchers have also attributed the lack of response to K accumulations in subsoil from leaching of applied K. If the physical and chemical conditions were favorable in the subsoil horizons, e. g., no pan formation and no severe Al toxicity, plant roots could absorb K from the subsoil horizons.     

Origin and geochemical evolution of saline groundwater in the Brisbane coastal plain,Australia

Fresh, brackish and saline groundwaters of variable acidity and redox potentials occur in a coastal floodplain area, north of the Brisbane River in Southeast Queensland, Australia. The complicated spatial and vertical distribution of these groundwaters, and their tendency towards a seawater chemistry, reflect that the local groundwater system has undergone repeated episodes of hydrological adjustments in response to Quaternary sea-level fluctuations and coastal landscape modifications. Since the last major Holocene transgression, topographic changes have permitted repetition of evaporative concentration, aeration and acidification processes in near-surface groundwaters. The surface and subsurface occurrences of gypsum, pyrite and jarosite minerals, in the Brisbane coastal plain, testify to the intrinsic relationship between sea-level and topographic variations, and hydrogeochemistry of the local groundwater system.     

Physico-chemical characteristics of the soils from the coastal plain in Shanghai,China

Characterization of the physico-chemical properties of the soils collected from the coastal plain covering a total area of about 1,908 km² in the Changjiang Delta in Shanghai, China, has been conducted in order to investigate the current status of agricultural soils, with special reference to the effect of alluvial deposits on the development and utilization of the soils. The experimental results indicated that the soils of the coastal plain displayed a sandy (loam) texture. The soils from Qingcun and Guangming Towns in the Fengxian District, Shanghai, contained the highest amount of clay, showing the highest capacity to remain fertile. The soils from Xinghuo Town in the Fengxian District contained the highest amount of salts due to the strong mineralization degree from the groundwater and the effect of the marine deposits from the Hangzhou day, which resulted in the highest exchangeable sodium percentage in the soils. The soils from greenhouses (Sunqiao, Huinan, and Qingcun Towns) showed a higher salt content than others, in contrast to the paddy and orchard soils. The analysis of the soil fertility indicated that the soils from Guangming and Qingcun Towns in Fengxian were rich in organic matter, total nitrogen, and total potassium, and were fertile soils. In contrast, though the soil from Xinghuo Town was rich in potassium, it lacked other nutrients. The phosphorus content in the soils was mainly determined by the application of fertilizers, and the total and available phosphorus contents in the greenhouse soils were higher than those in the soils with other land use types.     

Non-destructive neutron activation analysis of particle size fractions and soil extracts

Non-destructive instrumental neutron activation analysis was examined. Using long-lived isotopes, La, Sm, Ce, Sc, Fe, Co, Cs, Th, Cr, Hf, and Tb, and using short-lived isotopes, Al, V, Na, and Mn in various particle size Tractions of clay, silt, fine sand, and coarse sind, and the oxalic acid extracts of the soil were determined. Relative standard deviations (CV) were in the range of 1.7 to 12%. The reliability of the analysis was also examined. Recovery percentages ere in the range of 87 to 120%. The analytical results of geochemical reference samples of JG-1 and JB-1 showed general agreement with the other worker's results.

Distribution patterns of those elements among the six fractions of highly weathered and ively unweathered soils were briefly discussed in relation to weathering processes.     

Particle size fractionation of soil containing coal and combusted particles

Standard procedure for dispersing natural soils for particle size fractionation can be too aggressive for soil containing coal and other organic particles from coal industries. We have investigated ultrasonic dispersion for the latter in four soils differing in pedogenesis (Phaeozem, Podzol, reclaimed mine soils), carbon content (27.5–138.6 g kg^–1), clay content (80–153 g kg^–1) and sources of particles (airborne coal dust, combustion residues, lignite particles). As we found previously for natural soils, the ultrasonic energy needed for complete dispersion varies between 450 and 500 J ml^–1, but the resulting particle size distributions differ from those obtained by standard textural analysis. This is probably related to the different properties of native soil organic matter and coal and combusted particles. Coal and soot particles may partly resist oxidation with hydrogen peroxide, depending on material and particle size. The diameter of lignite particles, remaining after oxidation, is overestimated in sedimentation analysis by a factor of 1.66. Sand-sized lignite particles can be disrupted by ultrasonication and redistributed to finer particle size fractions. The ultrasonic dispersion and particle size fractionation procedure can be applied to soils containing coal and combusted particles, but caution is needed in interpreting the results if they contain large proportions of coal particles.     

Response of texas bluegrass to season of nitrogen fertilization on the Louisiana coastal plain

Texas bluegrass (Poa arachnifera Torr.) has shown potential for use as a cool‐season perennial pasture grass in the southern Great Plains, where it occurs as a natural component of rangeland plant communities, and into the western Coastal Plain. Responsiveness of this grass to nitrogen (N) fertilization appeared to be limited to the spring growing period in initial evaluations in Louisiana. A field plot experiment was conducted to assess forage production and quality responses to season of N fertilization on the Syn‐1 population of Texas bluegrass. Winter forage production responses to 50 kg N ha^‐1 were obtained in the 1997–98 growing season but not in 1998–99 after stands had been depleted by summer drought. Greatest yield increases resulted from spring N application, however, fall plus winter fertilization provided the most uniform distribution of forage through the cool season. Forage fiber fractions, in vitro digestibility, and crude protein were not affected by N fertilization. Both amount and distribution of Texas bluegrass forage, but not forage quality, can be manipulated by time of N fertilization.     

Correction of cone index for soil water content differences in a coastal plain soil

Soil penetration resistance (cone index) varies with water content. The field variation of water content could mask treatment differences. The correction of cone index data to a single water content would help prevent this. We used equations from TableCurve^™ software and from the literature to correct cone indices for differences in soil water contents. Data were taken from two field experiments where cotton (Gossypium hirsutum L.) was grown using conventional and conservation tillage without irrigation, and beans (Phaseolus vulgaris L.) were grown using conventional tillage with microirrigation. Boundary conditions based on hard, dry and soft, wet soils were imposed on the equations. Equations fit the data with coefficients of determination ranging from 0.55 to 0.92 and error mean squares from 1.37 to 6.35. After correction, cone index dependence on water content was reduced. A single-equation correction did not always fit the data across all treatments. Separate corrections, based on treatment, might be required. When corrections required multiple equations, differences may be real or may be a manifestation of the correction differences. In this case, the correction may not be feasible (unless some future work can coordinate different equations and assure a uniform correction).