摘要:

Semiarid grassland soils in western South Dakota may be as old as mid-Pleistocene, so that time has been sufficient for caliche to form. However, caliche is not present. Historical weather data were used to estimate leaching and secondary CaCO3accumulation. Caliche should have developed. Subsoil Ca adsorbed by roots and moved upward into the herbage probably has been deflated in the ash following prairie fires to prevent caliche formation.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

We studied properties and classification of selected volcanic ash soils formed under different vegetations on Kenai Peninsula, southcentral Alaska. Spruce (Sitka spruce) and alder soils had well-developed eluvial and spodic horizons common to most Spodosols. Fescue soil, developed under fescue-lichen tundra vegetation, showed a thick, very dark humus horizon similar to most Andisols in Japan. Bluejoint soil had an E horizon masked by organic matter, suggesting the degradation of Spodosol to Andisol.Although the four soils showed differences in vegetation and morphological properties, they shared many similarities in physical, chemical, and mineralogical properties, reflecting the properties of volcanic ash as the parent material. Nevertheless, the four soils had significant dissimilarities relating to their soil-forming processes. For example, spruce and alder soils showed humus and mineralogical characteristics, such as high humic-acid-to-fulvic-acid (HA:FA) ratios and abundance of smectite in the eluvial horizons and very low HA: FA ratios and abundance of chloritized 2:1 minerals in the illuvial horizons. Fescue soil contained humic acid with a high degree of humif ication and allophanic clay mineralogy. Bluejoint soil was nonallophanic as spruce and alder soils, but it showed the predominance of chloritized 2:1 minerals in the clay fractions throughout the profile.Both spruce and alder soils having well-developed eluvial and spodic horizons satisfied the chemical criteria for a spodic horizon and were classified as Typic Cryohumod (Soil Taxonomy). Although the two soils also satisfied andic properties, we insisted that the Andisol-Spodosol transition problem should be basically brought into settlement according to the properties reflecting the major soil-forming processes. Fescue soil satisfied the requirements of andic properties and was classified as Dystric Cryandept (Soil Taxonomy) and as Typic Haplocry and (ICOMAND proposal). Bluejoint soil had a less developed eluvial horizon, but satisfied the chemical spodic criteria using the clay contents determined by the NSSL pipette method because of incomplete dispersion of the clay fraction. However, according to the data of clay measurement by the pipette method after sonication and pH adjustment, bluejoint soil did not meet the spodic criteria and was classified as Dystric Cryandept (Soil Taxonomy) and as Typic Alicryand (ICOMAND proposal). A method of particle-size analysis should be established for volcanic ash soils, especially for the spodic criteria of (Fep+ Alp)/% clay.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Extreme variability in millet stands over very short distances (2 to 20 m) poses a major constraint to grain production in Niger and other Sahelian countries. This study was undertaken to examine the chemical properties of associated productive and unproductive soils. Soil samples (0 to 15 cm) were taken at 26 sites along a 15-m transect between a productive and an unproductive region in a field of the Labucheri soil series (sandy, siliceous, isohyperthermic Psammentic Paleustalf). Chemical properties of soil profiles at three locations along the transect were also examined. Unproductive soils were associated with low (<4.5) pH, high Al + H saturation of the cation exchange sites, and decreased amounts of exchangeable K, Ca, and Mg when compared with productive sites. These chemical properties may result in Al or Mn toxicity or deficiencies of K, Ca, Mg, and P and appear to account for the variability that exists in millet stands. All soils become acidic at depths <30 cm. We propose a scheme for the genesis of these highly variable, acidic soils in this semiarid region.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Some municipal and industrial wastes have been applied to land to recover their plant nutrients. Some of these wastes contain Cd and other heavy metal contaminants. Many studies have been conducted on Cd-Zn interactions in plants and on forms of these elements in soils. We conducted the present study to relate Cd-Zn concentrations in plants to levels of Cd and Zn in soil recovered by several extractants soon after application of Cd and Zn sources to soil. Cadmium nitrate and ZnSO4or Zn(C2H3O2)2were mixed with a Zn-deficient Crowley silt loam soil (Typic Albaqualf), cropped with corn (Zea mayaL.), and then cropped with Swiss chard (Beta vulgaria).Applied Cd significantly increased the Cd/Zn ratio in both crops, especially in Swiss chard, which accumulates heavy metals. A previously published sequential-extraction procedure was used to fractionate Cd and Zn in soil after the corn harvest. Results of statistical analyses showed the highest correlation between Cd uptake by each crop and the “carbonate” (0.05MNa2EDTA-extractable) and “sulfide” (4MHNO3-extractable) fractions of Cd in soil. Including other Cd fractions resulted in only slightly higherR2values. Zinc uptake by each crop was best related to the “organic” (0.5MNaOH-extractable) fraction of Zn in soil, and including the other Zn fractions did not affect the relationship. These results show that Cd and Zn uptake by corn or Swiss chard was not related to similar chemical fractions of these elements in soil, and that the Cd/Zn ratio in plant tops was significantly affected by both Cd and Zn applications to soil.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

We conducted laboratory research to determine the effects of exchangeable Mg-to-Ca ratios on the accumulation of exchangeable Na and K. Soil samples were washed with solutions containing Na at 60 or 120 mmol L−1or K at 10 or 20 mmol L−1and Mg-to-Ca ratios ranging from 0 to 1 with a constant concentration of Ca + M g of 8 mmol L−1. The results showed that as the ratio of Mg to Ca increased, the exchangeable Na or K increased. In these soils the exchange between Mg and Ca indicated a preference for Ca, which explains why Na and K are more competitive against Mg than against Ca. The exchangeable Na ratio (ESR) was negatively correlated with organic C contents of soils for both Ca-Na and Mg-Na systems, but the relative preference for Na in Mg-Na systems compared with Ca-Na systems was not consistently related to organic C.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Using F potentiometry, we analyzed samples of ultrafiltered organic material obtained from lysimeter solutions during a growing season in two forest soils of different acidity. F potentiometry is a newly developed technique that allows the speciation of A1 in the presence of complexes of unknown thermodynamic characteristics. The samples were analyzed for the amount of bound A1 after known amounts had been added. All samples were separately studied with gel chromatography, to quantify the occurrence of precipitation and flocculation phenomena. These were performed after buffering the samples to the pH ranges usually occurring in the soil solution during a growing season. The original pH of the samples and the A1 content were also measured.Results regarding the intensity of A1 binding and the formation of precipitates in 62 samples are shown. The variance of the variable describing the intensity of precipitation was significantly split among the different factors affecting it, namely the pH of the treatment, the amounts of bound and free A1, and a covariant representing unspecified site differences.One can conclude that all these factors are important in defining the precipitation and mobility of the organic matter in the solution of the upper forest soils studied. These have implications for the interpretation of processes related to organic matter turnover and A1 mobility in the upper soil.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

We characterized the organic matter associated with the fine clay fraction separated from the Ae horizon of a Typic Haplorthod, using chemical, infrared, carbon-13 nuclear magnetic resonance, and gas chromatographic-mass spectrometric methods. Infrared and13C NMR spectra of the initial clay-organic complex showed the prominence of long-chain aliphatics. Extraction with 0.5MNaOH removed substantial amounts of fulvic acid.n-Hexane and chloroform extracts containedn-alkanes, ranging from C16to C35, long-chain alcohols, and more complex aliphatics. About half of the clay-associated organic matter consisted of humic materials; the other half was composed mainly of long-chain aliphatics. From the characteristics of the materials isolated and identified, it appears that the long-chain aliphatics have low mobilities in soils and that it is fulvic acid that is capable of penetrating clay interlayers. If aliphatics are present in clay interlayers, they have most likely been transported there by fulvic acid or other humic materials within which they are captured and that act as vehicles for the transport of hydrolphobics within soil profiles.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

We used mercury-intrusion porosimetry in a study on modification of total porosity and pore-size distribution (PSD) at different depths (5, 10, 15, and 20 cm) in a rice soil puddled by three different mechanical implements. All treatments caused a layer of reduced porosity to form at the soil surface. At rice harvest time the porosity along the profile was similar to that found in the soil before puddling. Pore-size distributions were similar for the different treatments. Pores larger than 50 μm equivalent cylindrical diameter (ECD) decreased by about 50% at the 5-cm depth immediately after puddling.

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1988

数据来源: OVID