摘要:

Analytical expressions are derived for the absorption of water from cylindrical and spherical cavities, when the flux of water at the cavity is imposed. The solution reduces to the one-dimensional case in the short time limit. After a certain time the soil around the cavity may become saturated and the growth of the saturated region with time is investigated Correction terms due to gravity are also derived in the case of a spherical cavity.

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

Formation of Kaolinite and gibbsite and their persistence in Ultisols of the Southern Region of the United States were investigated with mineralogical, chemical, and thermodynamic analysis.The results showed that the Hayesville soil, with high gibbsite and relatively low amounts of kaolinite, had high Al and very low Si content soluble in NaOH. In Cecil soil, where both kaolinite and gibbsite were well represented in the clay fraction, an increase in Si and an almost similar Al content were observed compared to those in the Hayesville soil. However, in the Tifton soil, where kaolinite was dominant over gibbsite content, the highest Si and lowest amount of Al soluble in NaOH were found.A stability diagram, developed from three calculated chemical potentials: pH - 1/3 pAl3+= 2.7; pH - 1/3 pAl3+= 1/3 pH4SiO4+ 1.1; and pH4SiO4= 4.73, intersecting at one point, showed six stability areas. It appeared that formation and stability of kaolinite and gibbsite in the Ultisols were dependent upon successively increasing/decreasing levels of H4SiO4and upon the gibbsite potential pH - 1/3 pAl3+

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

The Green and Ampt (1911) equation was used to model mass infiltration curves obtained from flooding soil monoliths. Eight runs were made on five monoliths under various antecedent moisture conditions. The input parameters, hydraulic conductivity, pressure head, and fillable porosity were measured for soil layers in the vicinity on the monoliths using simple field techniques. The infiltration into the monoliths was calculated and objectively compared with the measured infiltration. In general, the simulations were acceptable but subject to local variations.

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

Gas that is entrapped when a porous medium imbibes a liquid will eventually be expelled from the medium by molecular diffusion when the sample is kept in contact with a liquid supply. It is shown that the phenomenon can be formulated in terms of a differential equation which contains more than dependent variable. As a result, it is possible to identify the additional relationships that must be established among the dependent variables in order to make a rigorous solution possible.Because all of the required relationships are not known, an alternate approach of incorporating assumptions which eliminate the need for additional functions was used to obtain an approximate solution for the case of one-dimensional diffusion. The result is shown to be useful for estimating the times involved for the elimination of trapped gas from sandstone samples.

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

Clays from five selected soil series from the southern region of the United States were studied for their K fixation properties. The soils were very strongly to slightly acid in reaction. The CEC of the clay fractions of the soils ranged from 9.6 to 58.8 me/100 g. Kaolinite was a common clay mineral constituent of all the clays. The basal reflection intensities and the thermal peaks of kaolinite decreased in the order of Cecil > Varina ≈ Berks ≈ Iredell > Beaumont. All clays showed the high order mica reflection at 3.35 A, but not at 10 A, except in Berks clay. It is suggested that mica in Berks clay was less weathered than that in the other clays. The 14-A peak was present in all the clays, being highest in the Iredell clay. Montmorillonite was the dominant clay mineral in Beaumont and was probably also present in Iredell clay.All clays of the soils had the capacity to fix K. Potassium adsorption by the wedgezones in the interlayer surfaces of weathered mica was probably the controlling factor of K fixation in acid soils, such as Cecil, Varina, and Berks. Increased fixation of K by the clays from Cecil, Varina, and Iredell gradually increased the intensity of the 10-A peak in the X-ray diffractograms. Potassium fixation by Beaumont clay did not result in the appearance of the 10-A peak. The intensities of the 10-A diffraction of the Cecil and Varina clays were highly correlated with the amount of K added, but those of Iredell clay were not.There was no obvious disappearance of other X-ray reflections with the appearance of the 10-A peak in the X-ray diffractograms. The appearance of 10-A peaks supplemented existing 3.35-A basal reflection of mica in the clays. Potassium fixation had reconstituted the existing disordered mica in those clays. The clay mineral structure was of more importance than the CEC in determining K fixation properties of clays.

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

A water-soluble neutral polysaccharide fraction was isolated from a woody peat soil. A liquid resin Amberlite LA-2 was utilized to isolate the neutral fraction of the water soluble H-peat. Gel chromatography with various Sephadex gels was used to obtain a polysaccharide. The polysaccharide was polydisperse with a most common molecular weight between 50,000 and 60,000. Gas liquid chromatography of the sugars released by hydrolysis of the polysaccharide as both the alditol acetates and the silyl ethers showed the presence of Dglucose, D-galactose, D-mannose, and D-xylose. L-Arabinose and possibly L-rhamnose were present in smaller amounts.The polysaccharide, which constituted more than 3 percent of the water-soluble H-peat, had no effect on the stability of soil aggregates.

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

Factors influencing nitrite transformation in soil were investigated and their importance was evaluated in sterile and nonsterile soil samples. For this purpose autoclaved and non-autoclaved soils to which nitrite was added were incubated under varying conditions of pH and aeration. The chemical changes were measured by the determination of nitrite and the evolvement of nitrogenous gases. It was established that chemical nitrite decomposition is predominant under sterile and nonsterile conditions at low pH in aerobiosis as well as anaerobiosis. Very little chemical decomposition of nitrite was observed in a neutral and alkaline environment under sterile or nonsterile conditions. The disappearance of nitrite occurred at a much greater rate under anaerobic, nonsterile conditions and could be attributed to microbial activity. During chemical nitrite volatilization, the major gases evolved were nitric oxide and nitrogen dioxide, but if biological activity was predominant, nitrous oxide and molecular nitrogen were evolved.

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

The distribution of different forms of N in desert soils collected at Nevada Test Site were examined. Soil profiles were sampled in 7.6-cm increments to various depths of which the maximum was 91.4 cm. Among the soil profiles examined, the different forms of N in the surface layer (0.0–7.6 cm) was always NO2-N (not detectable) < extract-able NH4,-N < NO3-N < fixed NH4+-N < organic N. In the sublayers, some variations from this order of N forms occurred in that the extractable NH4-N was greater than NO3-N with the presence of trace amount of NO2-N and/or the fixed NH4-N was greater than organic N. The amount of total N was the greatest in the surface layer and usually decreased very sharply in the second layer (7.6–15.2 cm). Below the second layer, the total-N contents generally varied slightly. In the surface layers, the total N was always accounted for primarily by organic N. Depending on the soil and the profile layer, the concentration of the total extractable inorganic N ranged from 0.00004 to 0.00586 percent by weight of oven-dry soil. Expressed as percentage of total N, the range was 0.33 to 16.17. The amount of fixed NH4+-N varied somewhat with different soils, but within any given soil profile, it generally varied slightly. The fixed NH4-N in the profiles collected in different areas and under different plant species ranged from 0.0028 to 0.0079 percent by weight. Expressed as percentage of total N, the range was 3.4 to 74.4. The exchangeable K concentration under the plant was 41 to 240 percent greater than in the bare soil. The higher exchangeable K plus the higher organic matter content was considered to cause the lower NH4-N fixation under the plant compared to its fixation in the bare soil.

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

The availability of Mg from different fractions of four Michigan soils and from one fraction each of chlorite and bentonite was determined by cropping in the greenhouse. Enough of each fraction to supply a total of 20 mg of Mg per culture was mixed with quartz sand and cropped twice with oats.The Mg concentration of the soil fractions increased as the particle size decreased, except that the concentration of the fine clay fraction tended to be less than the medium clay fraction. Magnesium concentration of fractions from the Sims soil tended to be greater than the other soil fractions.The data indicate that Mg is available for plant growth from the octahedral layer as well as from interlayer material. X-ray data suggest that sufficient interlayer material was removed from some clay fractions to convert heat-stable 14-A material to heatcollapsible 14-A material.

ISSN:0038-075X    

出版商:OVID    

年代:1973

数据来源: OVID