摘要:

Because conductimetric titrations and potentiometric titrations have been used to characterize acidity in soil clays, we conducted conductimetric and potentiometric titrations of H- and Al-muck to characterize the nature of acidity in H-, Al-organic matter. Four samples of muck were used as models for soil organic matter. In addition, a carboxylic resin was used for comparison with the natural materials.Results from both potentiometric and conductimetric titrations showed that Al tended to lower the acid strength compared to H-organic matter. Also, Al is hydrolyzed in organic matter, as it is in clays, producing H+ions and buffering the system against increases in pH. However, complexed Al does not seem to react with base, at least over short periods of time (1 day). Thus, the adsorbed Al is not titratable and tends to lower the effective CEC and total acidity in organic matter. Whether or not complexed Al reacts slowly with base and affects the lime requirement in mineral soil remains to be determined.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

We examined the source of peroxidase (E.C. 1.11.1.7) activity in Pahokee muck, its role in subsidence of this organic soil, the effect of exogenous nutrients in soil peroxidase levels, and oxidation of humic acid by peroxidase produced by a fungus native to Pahokee muck. Amendment of soil with ammonium, phosphate, glucose, or vitamin-free casamino acids had no effect on peroxidase activity. Amendment with glucose plus ammonium, yeast extract, or ground sugarcane leaves increased peroxidase levels two-to threefold. Solubilization of the native soil organic matter or amendment of the soil with ethylenediaminetetraacetic acid (EDTA) also stimulated the enzymic activity. A peroxidase-producing fungus was isolated from the soil. The peroxidase synthesized by this fungus increased the E4/E6ratio of the purified humic acid. These data suggest that soil peroxidase of Pahokee muck is produced by the microbial community and that this enzyme functions in humic acid oxidation.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

The effects of lime and P additions on barley yield from an acid, P-deficient soil from the southeastern United States were examined in this laboratory and glasshouse study. The soil, Brevard, was amended with P in the presence and absence of lime. Six levels of P (50 to 175 μg/g) and three levels of lime (0 to 1350 μg/g were used. At any given level of P addition, increasing levels of lime addition increased plant yield and plant uptake of Ca and P. Associated soil effects were increases in solution P, reductions in the level of Al extractable with 0.01MCaCl2, and no changes in HCl-H2SO4-NH4F-extractable P. All these effects were examined so that the increases in plant yield might be explained. Calcium was ruled out as a factor in the yield increases, because its concentrations in the plants from the unlimed soil were not growth-limiting. Most likely, the lime applications increased plant yield first by neutralizing Al toxicity in the soil and then by increasing the concentration of solution P. Liming-induced increases in the concentration of solution P, which were evident in this study, have been predicted but largely undemonstrated.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

We conducted experiments to study the effect of applied phosphorus and zinc on their absorption and distribution in chickpea plants grown up to 64 days in a loamy sand (Typic Torripsamments). In the first experiment treatments included four levels of tagged P (25, 50, 100, and 250 ppm) at 0.25 mCi/g P2O5, and in the second experiment they included 5 ppm of tagged Zn at 0.1 mCi/g Zn and five levels of P (0, 25, 50, 100, and 250 ppm) in all possible combinations. During 64 days of growth, 4.9 to 11.4 and 0.64 to 1.50 percent of fertilizer P and Zn were utilized by four chickpea plants, respectively. The absorption of fertilizer P was generally more than soil P and more with Zn than without Zn. About 75 percent of absorbed P was translocated to shoots with P up to 550 ppm, whereas at higher P levels, more P was retained in roots. Translocation of soil P to shoots decreased with 100 and 250 ppm P. Utilization and translocation of both soil and fertilizer Zn were considerably increased by 25 ppm P. At 250 ppm P, the utilization of soil and fertilizer Zn was decreased. The results showed that applied P and Zn affected absorption and distribution of soil and fertilizer P and Zn in roots and shoots, depending upon their level. These results also confirmed the occurrence of P and Zn interactions both in soil and in different plant parts, and the nature of these interactions may depend upon the soil pH and their levels.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

We took samples of Pennsylvania-age shale at various depths from a freshly exposed strip mine face. By a series of washings and screenings and heavy liquid separations, pyrite was removed from the shale matrix. We then analyzed the samples chemically and examined them by x-ray diffraction and scanning electron microscopy.Iron and sulfur contents of the pyrites isolated from the shales were nearly the same as museum-grade pyrite. The x-ray diffraction peaks of these pyrites were the same as those for museum-grade pyrite. A similar array of cubic and octahedral crystals and morphological shapes of pyrite were observed in each of the five shales examined with the electron microscope.Solid crystals and smooth irregular fragments of the various layers were usually about one-half or less of the total volume and one-quarter or less of the total surface. Conglomerate pieces of pyrite with rough surfaces made up one-half or more of the total volume and nearly three-quarters or more of the total surface. Framboidal pyrite could be found in shale from every layer; however, it was 1 percent or less of the total volume and surface of the pyrites present.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

The reducing substances in soils produce an anodic current at a graphite electrode. The diffusion current at +0.35 V versusMAg-AgCl electrode reflects ferrous iron and some easily oxidizable organic substances, and that at +0.70 V reflects, in addition, manganous ions and some organic substances that are hard to oxidize. When measured in situ, the current density at +0.7 V was used for estimating the amount of reducing substances in soil. Application of the method showed that the stronger the reduction in soil, the larger the amount of reducing substances. The amount was closely related to the growth of rice plant. There was a correlation between the logarithm of the amount of reducing substances and the Eh of the soil, with a correlation coefficient of −0.905.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

We determined phosphate-availability indices and inorganic phosphate fractions in 12 Alfisols of Himachal Pradesh, India, on air-dry and waterlogged soil samples with a view to devising a suitable method to assess the phosphate availability in waterlogged soils on the basis of air-dry soil samples. All the native inorganic phosphate fractions increased upon waterlogging, with the maximum increase of 70.7 percent in Fe-P. Waterlogging also increased the phosphate-availability indices determined by seven soil chemical extractants.The stepwise regression analyses indicate that Fe-P was the most important variable contributing to the total variation in the regression of Olsen, Bray P1, Bray P2, Truog, Peech, and Morgan's extractants and Ca-P in the regression of North Carolina's extractant both in air-dry and waterlogged soils. Aluminum phosphate was the second important variable contributing to the variation in the regression of Olsen, Bray P1Bray P2, and North Carolina's extractants and Ca-P in the regression of Peech and Morgan's extractants under both air-dry and waterlogged conditions. With the exception of Truog's extractant, six other extractants extracted phosphate from the same inorganic phosphate fractions under both air-dry and waterlogged conditions, indicating their similarity under two situations. However, their suitability needs to be judged in relation to plant growth parameters under waterlogged conditions.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

Centrifugation for long times or at high speeds resulted in progressively decreasing concentrations of iron and aluminum in 0.1Msodium pyrophosphate extracts of soil. Centrifugation at 80 000gfor 6 hours, as compared with 20 000gfor 20 minutes, decreased the Fe concentrations from 23 to 80 percent and the Al concentrations from 9 to 35 percent in nine samples of podzolic B horizons. The sediments contained Fe, Al, Si, P, and Na, as indicated by energy dispersive x-ray analysis, and carbon. Chemical analysis of some of the sediments showed that Fe was usually the dominant component, but that percentages of Al and Fe were similar in extracts of two Fe-poor B horizons. The results are discussed in relation to the concept that 0.1Msodium pyrophosphate extracts organic complexes of Al and Fe, and in relation to chemical criteria for spodic horizons.

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1982

数据来源: OVID