摘要:

SUMMARYThe microbiology of soils subjected to stripping and stockpiling at opencast mine sites was investigated using a combination of and biomass fumigation plate‐count techniques. Mounds varied in age from a few weeks to 11 years, and soils included both mineral and organic variants. Results showed that after an initial stimulation of bacteria, microbial populations declined in stockpiles. Numbers of viable fungal propagules, and to a lesser extent actinomycetes, declined with depth in mounds, particularly below about 1 m, and this trend was accentuated with increased time of storage. However, stockpiled soils were highly variable in terms of microbiological status and displayed considerable lateral as well as vertical heterogeneit

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1991.tb00085.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYData from field work and pot experiments gave insight into transformations occurring in soil microbial populations at opencast coal sites during the first year of land restoration. Total bacterial biomass increased markedly immediately following restoration, while pot experiments revealed that this flush was confined to soil stored below 1 m depth in stockpiles, where anaerobic conditions develop. Fungal and actinomycete propagules declined at the outset of restoration, but rallied during the first year, while the bacterial flush subsided. Fungal hyphae, which accounted for 50% of microbial biomass in surface mound and freshly restored soils, accounted for>99% one year after restoration. Experiments involving fertilizer and ryegrass amendments showed the biomass of restored soil to be limited by carbon, rather than nitrogen or phosphorus.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1991.tb00086.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYThe activity of a purified urease, obtained from Bacillus pasteurii, was inhibited by humic and fulvic acids obtained from an agricultural soil. Enzyme kinetic studies showed that the humic substances affected the affinity of the enzyme for its substrate (Km) and the maximum velocity of the reaction (Vmax). The Vmaxwas inhibited to the same extent by both humic (HA) and fulvic (FA) acids, the precise effect depending on the pH and concentration of humic substance. At pH 4.0, HA concentrations of 25 pg cm−3and 10 μg cm−3inhibited the Vmaxby 38.5% and 20% respectively. HA and FA had similar effects on the Kmbut in this case the lowering of the affinity of the enzyme for its substrate was not concentration dependent in the range 0–25 μg cm−3of humic substance. Typically, the affinity was decreased from a KMof 50 mM in the control to 67 mM in the presence of HA and FA.The effects were not due primarily to the ash or N contents of the humic substances because de‐ashed humic acid and synthetic model humic (made from catechol, guaiacol, pyrogallol, resorcinol and protocatechuic acid) and fulvic acid (made from polymaleic acid), containing virtually no ash or N, were equally as effective. The effect was not related to the phenolic monomers which, before polymerization, had no effect on urea

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1991.tb00087.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYFulvic acids have been isolated from a sandy loam (Countesswells series) and a clay soil (Tipperty series) and the products of their reaction with different amounts of iron over a range of pH from 0.5 to 11 analyzed by Mössbauer spectroscopy. Three distinct types of spectral component were detected at 77 K, a sextet from magnetically dilute Fe(III) and doublets from Fe(II) and Fe(III), the last arising from both organic complexes and poorly crystalline oxide species.In iron‐fulvic acid mixtures the proportion of iron as Fe(II) increased as the pH was lowered from 5 to 1 by the addition of hydrochloric or nitric acid at all Fe to fulvic acid ratios (1:5 to 1:500). When the pH was lowered below 1 the amounts of Fe(II) decreased with the lower Fe to fulvic acid ratios, but increased with the higher ratios. The amounts of the Fe(III) component contributing to a doublet signal decreased with decreasing Fe:fulvic acid ratios.At low iron concentrations the iron appears to be strongly bound to the fulvic acid, but when the iron content is of the order of 1–2% uncomplexed Fe(III) species can be present. At pH>2 these are hydrolysed ions which form poorly‐crystalline oxides at higher pH. This was confirmed by analysis of spectra at 4.2 K. At pH<2 free ions are present in solution.In solutions with high fulvic acid contents (greater than 100‐fold excess) the reactions with iron are completely reversible, but in solutions with a lower proportion of fulvic acid to iron, where free ions are present, there is a lack of rever

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1991.tb00088.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYHumic acids were isolated from nine topsoils in New Zealand tussock grasslands. Cross‐polarization13C NMR spectra of solid samples were used to estimate fractions of carbon contained in different types of chemical functional groups. The degree of oxygen substitution of aromatic rings showed a strong negative correlation with soil development. Aromaticities greater than 0.25 were found in humic acids from only the two least‐developed so

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1991.tb00089.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYNon‐steady‐state diffusion of chemicals in soil can be described by Fick's second law using suitable effective diffusion coefficients. In this study a ‘stopped elution’ method was used to determine experimentally these effective diffusion coefficients for gaseous and dissolved substances in dry and water‐saturated soil. For this purpose a high‐performance liquid chromatography (HPLC) apparatus and a gas chromatograph (GS) were used in combination with soil‐filled columns. The method is based on the observed spreading of a substance moving through a soil column. This broadening is the result of several processes, one of which is diffusion. A suitable experimental design permits the separate measurement of that part of the widening caused by diffusion.The measured effective diffusion coefficients were compared with theoretical values calculated using predictive algorithms from the literature. For liquid‐phase diffusion the maximum deviation between the calculated and the measured values was 34%. The experimental results for gaseous diffusion showed systematic upward deviation from the calculated Coefficients. This might be caused by the diffusion of molecules in the adsorbed state, a phenomenon that had been neglected in t

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1991.tb00090.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYA detailed mechanistic model of water movement and transport of non‐reactive solute in a macroporous soil is described. One important feature of the model is that it may be run in either one or two flow domains using the same values for the hydraulic properties characterizing the soil. Water and solute movement in the micropores is calculated with the Richards and convection‐dispersion equations and, in two domains, this is coupled to fluxes of water and solute in the macropores by empirical interaction terms. These interaction terms are redundant in the one‐domain model, which simply reduces to the non‐steady state convection‐dispersion equation.A sensitivity analysis is presented showing how it is possible to identify conditions under which a macropore flow domain may need to be considered. In part II (Jarviset al., 1991), the model is evaluated under field conditions in chloride breakthrough experiments in soil monolith l

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1991.tb00091.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYA model of water and solute transport in macroporous soils (Jarviset al., 1991) has been evaluated in column breakthrough experiments under field conditions. Hydraulic properties were first measured in replicate soil monolith lysimeters sampled from grass ley and continuous barley treatments in a clay soil. A pulse input of 0.05 M KCl was then supplied by drip irrigation and measurements made of the water discharge and chloride leaching resulting from the natural rainfall over a 1‐month period.The results showed that the macropores constituted the dominant flow pathway (accounting for 80% of the total water outflow) and that diffusive exchange of chloride between the two flow domains was the main factor causing variability in leaching. Larger hydraulic conductivities and macroporosities in the lower topsoil and at plough depth in the grass ley monoliths were taken as evidence of structural amelioration. Less of the applied chloride was leached in the grass monoliths than in the barley (means of 20% and 31% respectively). This was mainly due to a smaller effective aggregate size and thus a more efficient diffusion‐controlled retent

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1991.tb00092.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYThis article deals with the extraction of soil water using the suction‐cup method and its accompanying problems. This method has become well‐developed over the past 20 years. It allows continuous sampling during any period and, if necessary, at several different depths of a soil profile. The installation of the suction probe is easy and the profile is only negligibly disturbed. Some problems may occur when this technique is used. The spatial variability of the properties investigated is often underestimated and must be clarified by sufficient replication. An important point of discussion is the by passing of water flowing through macropores. The problems of alteration of the sample by the sampling system also deserve attention. These can be the ‘filter effect’ as regards macromolecules and colloids, the sorption of trace substances, and the gas exchange between the sample and the atmosphere of the sampling

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1991.tb00093.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYEquivalent salt solution series have been previously defined as solutions with combinations of sodium absorption ratio (SAR) and electrolyte concentration (Ec) producing the same extent of clay swelling in a given soil. The present study shows that there is a high (r2>0.96) positive correlation between logEcand logSARof equivalent salt solutions series, in the equation:where a1and b1are constants for each equivalent salt solution series for a given soil.Log a1could also be represented as a linear function of b1resulting in the equation:wherea2andb2are constants for a given soil. Solving this equation using any given value ofb1yields the combinations ofSARandEcwhich make up each equivalent salt solution series for a given soil. The relationship between log a1andb2for three soils from western United States, namely Waukena, Pachappa and Grangeville, was similar, with their combined data having ar2value of 0.96. This indicated that a single set of equivalent salt solution series values could be used for these three soils which have different clay contents and clay mineralogy.Prediction of hydraulic conductivity decreases withEcreduction at given values ofSARin red‐brown and alluvial soils from southern Tasmania, using the equivalent salt solution series values for Waukena soil, showed similar patterns to measured values and also to those predicted using the equivalent salt solution values applicable to the respective Tasmanian soils.Thus, available data indicate that the same set of equivalent salt series could be applied to the five soils studied. If further testing shows that a single set of equivalent salt solutions values could be applied to all or large groups of soils, this would facilitate the application of the equivalent salt solution concept to predict salt solution flow in the fiel

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1991.tb00094.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY