摘要:

Interactions between soil and aniline residues increase with temperature. Exothermic values of free energy change point out the higher affinity of the Soignies soil colloids forp-chloroaniline, in comparison to aniline, with increasing temperature. The magnitude of adsorption of these aniline residues was inversely related to their water solubilities.The temperature coefficient of the thermodynamic equilibrium constant, expressed per unit of organic matter, emphasizes the greater reactivity of Soignies soil organic matter. The net increase in entropy change, calculated for that substrate, indicates higher stability of these amine-soil colloids complexes. Results of the thermodynamic study suggest that diffusion processes ofp-chloroaniline within a porous adsorbent, like Soignies soil organic matter, must play a leading part in the overall energetic process of the adsorption reaction. This view is further supported by values of adsorption rate constant derived from the rates of adsorption ofp-chloroaniline by the two soil types.

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

An understanding of the distribution of microelements among various fractions of soils is important to understanding microelement soil chemistry and to the development of better soil extraction techniques. This study was undertaken to find methods to distinguish between chemical and physical forms of Zn, Mn, and Cu in soils and to apply these methods for eight southeastern soils. Successive extractions were made to solvate the Zn, Mn, and Cu in the exchangeable, organic matter, and Fe oxide fractions. The residue was separated into sand, silt, and clay size particles, and these, along with whole soil samples, were totally dissolved and analyzed for Zn, Mn, and Cu.The proposed fractionation scheme was satisfactory for most soils, but is still considered to be preliminary. The data for the sums of fractions agreed well with the whole soil data. The Zn, Mn, and Cu contents were higher in fine-textured, higher organic matter soils than in coarse-textured, low CEC soils. The fine-textured soils had a large proportion of their Zn and Cu in the clay fraction, but the coarse-textured soils had relatively higher percentages in the organic matter fraction. Fertilizer Mn was found mainly in the exchangeable and organic matter fractions. Percent Cu was highest in the organic matter and clay fractions when averaging the data over the eight soils studied.

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Phosphorus adsorption was investigated in two, paired soil profiles—flooded rice and irrigated pasture—to elucidate adsorptive changes of phosphorus as a consequence of long-term seasonal soil flooding. In the two concentrations studied, 10 and 50 ppm P, the adsorption of phosphorus was considerably higher in the flooded rice topsoils, 0 to 30 cm in depth, than in the upland topsoils. The differences in phosphorus adsorption gradually decreased as soil depth increased. High phosphorus adsorption in the rice topsoils was attributed to the higher content of amorphous iron resulting from reduction caused by seasonal soil submergence.Fractionation of phosphorus in the soil profiles revealed that prolonged seasonal flooding tends to increase the 0.1NNaOH-extractable phosphorus and, concomitantly, to decrease the reductant soluble and calcium phosphate contents. The lower pH and reductive conditions prevailing in the flooded rice soils appear to be responsible for the transformations of calcium and crystalline iron phosphates to amorphous. types of phosphate precipitates.No significant eluviation of iron or phosphorus was observed in the flooded rice, as compared with adjacent pasture soils. The high clay content of these soils, coupled with a virtual lack of water movement through the profiles, may restrict the movement of these two elements.

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

The behavior of CO2production, urease, phosphatase, and protease activities, amino acids, amino sugars, bacteria, and fungi was investigated during the microbial growth after the addition of a glucose-sodium nitrate solution to a red earth soil. The peak of the CO2evolution rate preceded all other tested biochemical and microbiological criteria. Urease and phosphatase activities were significantly correlated with bacterial but not with fungal biomass. All other biochemical criteria tested did not show a correlation, on normal regression analysis, with biomass. Fungal growth occurred both in the glucose-amended soil and in the control. The temporal sequence observed among the tested enzymes was due to their different roles in the soil metabolism of glucose, as well as to their different cellular locations. The newly synthesized, acid-soluble, amino acids nitrogen and protease activity were short lived. Yet, some sort of stabilization for urease and phosphatase activities occurred. The changes in total amino acids nitrogen were due to behaviors of neutral and acidic amino acids. Of the amino acids tested, lysine, histidine, arginine, valine, isoleucine, leucine, and phenylalanine showed negligible differences among values of corresponding soil samples moistened with glucosenitrate solution and with distilled water.The results show that no one measurement of activity is sufficient to interpret microbial growth in the soil system. Each of the indices measured must be used in conjunction with other tests to have a complete picture of the system.

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

To assess plant-available Mn in soil, seven extraction methods were evaluated by correlating data for plant Mn with soil test values. Burley tobacco (Nicotiana tabacumL. cv. ‘Burley 21’) and flooded rice (Oryza sativaL. cv. ‘Blue Bonnet 50’) were grown in the greenhouse on 15 soil types treated with either NH4NO3(448 kg N/ha) NH4NO3(448 kg N/ha) + lime (to pH 6.8), or NH4NO3(448 kg N/ha) + ground alfalfa (6720 kg/ha). Weight of dry matter and Mn content were measured at 50 and 60 days after planting for tobacco and rice, respectively. Plant Mn was then correlated with soil Mn extracted by seven methods, namely, water, 0.1NH3PO4, 0.01MCaCl2, DTPA (0.005Mdiethylenetriamine pentaacetic acid, 0.005MCaCO2, 0.1Mtriethanolamine), 0.1MNH2OH · HCL,NNaOAc, and 3NNH4H2PO4. The extractions were made on moist soil samples incubated for 10 days at 30°C either at field capacity or flooded.Based on correlations between extractable Mn and plant Mn, no significant relationship was detected for any extractant in limed soils, whereas in unlimed soil treated with NH4NO3or NH4NO3and ground alfalfa, DTPA, CaCl2, H3PO4, and water gave significant correlations. For tobacco, DTPA gave the highest correlation coefficient. For rice, DTPA, CaCl2H3PO4, and water gave significant correlation values that differed little among extractants. Adjusting the pH of DTPA to pH of 6.3 or 5.3 reduced the correlation coefficient from that of pH 7.3. Soil test values for soils extracted at moisture contents of near field capacity were more closely related to Mn concentration of both tobacco and rice than values for soils extracted after incubating under flooded conditions for 10 days.

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

The effects of four gravel concentrations (0, 20, 40, and 60 percent by weight) and three gravel size fractions (4–8 mm, 8–15 mm, and 15–40 mm) on the calibration of a neutron moisture meter and density probe was investigated for a beach sand and a clayey tropical Alfisol (Oxic Paleustalf). The slope of the regression line of the calibration curve relating neutron count ratio with volumetric moisture content of gravel-free sand was statistically significantly different from that of three gravel-sand mixtures. The calibration curve of three gravel-sand mixtures was statistically identical. For the gravel-soil mixtures, the slope of the calibration curve generally decreased with increased gravel concentration. The statistical comparison of the regression lines for the 4–8 mm gravel size fraction indicated that the slope coefficient of the calibration curve of only 60 percent gravel-soil mixture was significantly lower than that of 0, 20, and 40 gravel percentages. For the 8–15 mm gravel size fraction, the slopes of the regression lines of 40 and 60 percent gravel-soil mixtures were similar and significantly lower than that of 0 and 20 percent gravel concentrations. Gravel size had no effect on the calibration curve in the gravel-sand mixtures. In the gravel-soil mixtures, for 20 and 40 percent gravel concentrations, 4–8 mm gravel size had a significantly higher slope coefficient of the regression equations, compared with the 8–15 mm size fraction. The slope of the regression equation relating density count ratio with dry density significantly decreased with an increase in gravel concentration for 40 and 60 percent, compared with 0 and 20 percent gravels for gravel-soil mixtures. Heterogeneity of tropical soils, with regard to variations in texture and gravel concentrations, may necessitate a detailed calibration of the neutron moisture meter prior to its use on large watersheds.

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Metribuzin sorption by selected model soils, model soil components, and agronomic soils was assessed. Sorption by the model soil components gave insight into sorption by the composite substrates.Metribuzin adsorption ratios (= amount sorbed/amount applied) for inorganic substrates were independent of metribuzin concentration. Adsorption ratios for substrates containing organic matter decreased with increasing metribuzin concentration.Metribuzin sorption ratios for inorganic substrates were essentially independent of time; adsorption was wholly independent; desorption was marginally dependent in some cases. Metribuzin sorption by substrates containing organic matter increased with time; equilibrium was not reached in 104min, but extrapolation suggested it was reached before 105min.Sorption curves obtained for the agronomic soils were similar to, sometimes indistinguishable from, those obtained for peat-containing model soils.Sorption values for composite soils can be calculated, approximately, from sorption values for their components. Calculation consists of adding products of free metribuzin and sorption values obtained in the order, dominant component (e.g., peat), intermediate component (e.g., kaolinite), and subordinate component (e.g., sand).

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

The drying pattern of two soils with exchangeable sodium percentages (ESP) of 4 and 38 in the surface 0–15-cm layer was studied in the field in winter and summer seasons when the average evaporative demands were 2.5 and 12.5 mm/day respectively. ESP significantly affected the magnitude and pattern of water content changes in the profile following evaporation. The surface layers of the high ESP soil, with a low upward water flux, dried more rapidly than the surface layer of low ESP soil. The total surface-water loss under both evaporative demands was higher from the low ESP soil than from the high ESP soil because the hydraulic conductivity was greater. For both ESP soils, cumulative water loss at any time was greater under conditions of high evaporative demand than under low evaporative demand conditions. The studies indicate that the adverse effect of high ESP on plant growth is likely to be accentuated under conditions of high evaporative demand, and this would make water management more demanding.

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1979

数据来源: OVID