摘要:

summaryA method is described for using a quick setting epoxy resin to prepare a soil surface for infiltration measurements. It gives an unsmeared soil surface where the biological pores and structural surfaces are revealed. Experiments with an alluvial Prairie Soil and a Red Podzolic Soil, comparing steady state infiltration rates through cut smeared surfaces and resin treated ones, showed that the resin‐prepared surface permits 2.5–6 times more rapid entry of water. It is postulated that the greater rate more closely reflects the field structural condition. Apparatus, with a water reservoir remote from the hole, is also described for measuring constant head subsoil infiltration through a specially prepared auger h

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1986.tb00017.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

summarySeven mathematical models, which have been advanced for describing phosphate sorption by soils, are studied here with respect to their statistical behaviour in estimation. These seven non‐linear regression models include the Langmuir equation and two extensions of it, the Freundlich equation and two extensions of it, and Gunary's equation. Measures of non‐linear behaviour, such as the Bates&Watts (1980) curvature measure of intrinsic non‐linearity and the Lowry&Morton (1983) asymmetry measure of non‐linearity, were calculated for each model in combination with each of six data sets. It was found that the Freundlich equation and the extension of it proposed by Sibbesen behaved best, with Gunary's equation also having acceptable statistical properties, whereas the Langmuir equation and its extensions behaved worse, exhibiting properties which indicate that the estimators of their parameters would be severely biased and non‐normal in distribution. It is believed that similar conclusions may apply to other processes involving surface a

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1986.tb00018.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYThe soil acidity diffusion coefficients have been measured at two Pco2levels with values in the range 2–70 × 10−9cm2s−1. The coefficient passed through an ill‐defined minimum in the pH range 5–6.5. Theoretical values, calculated on the basis that the only significant acid‐base carriers in the soil were the H3O+‐H2O and H2CO3‐HCO−3pairs, agreed well with the experimental values over the whole pH range at Pco2= 0.005 atm. Agreement was not so good however at a CO2pressure of 0.0003 atm., especially in the neutralalkaline pH range. This was thought to be due to difficulties in maintaining this level of CO2throughou

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1986.tb00019.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYCompetition in adsorption between humic acid (HA) or fulvic acid (FA) and phosphate on synthetic goethite, gibbsite and two tropical soils was studied. The results for both goethite and gibbsite showed that HA and FA competed strongly with phosphate for adsorption sites at low pH values. The soils showed a similar result with a reduction in phosphate adsorption resulting from the addition of HA at the pH of the soils. The competition between HA and phosphate at different pH levels is illustrated by comparing the adsorption envelopes for phosphate on goethite, gibbsite and the two soils in the presence and absence of HA. The trends observed may be explained by the relative positions of the maximum buffer‐power (buffer capacity) of the organic acids and of phosphoric acid which are shown to lie in different pH range

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1986.tb00020.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYA previous study with a range of soils indicated that adsorption of copper could not be adequately described by the Freundlich equation. Adsorption curves for all but a highly calcareous soil could be divided into two straight lines with a marked increase in slope at low solution concentrations.A computer program (QELIOS) has now been used to calculate the effects of pH, CO, partial pressure and different inorganic anions on the chemical equilibria of the systems used in the adsorption experiments. At pH 6–8.5, hydrolysed species play a major role in Cu speciation whereas CO2−3species become important only at pH>8.0. The sensitivity of Cu hydrolysis to pH changes and to total Cu concentration in solution provides a possible explanation for the two surface Freundlich curves for soils of pH 6–7, and for the lack of such double surfaces for soils of

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1986.tb00021.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYThe more labile forms of aluminium in a range of soils from areas of permanent grassland were determined with a number of selective extractants. The amounts of exchangeable A1 extracted with molar KCl were dependent upon pH, while the amounts exchangeable with 0.3 M LaCl3, although much greater, were not well correlated with pH. There were good correlations between soil organic C content and A1 extracted by (i) 0.5 M EDTA and (ii) 0.1 M potassium pyrophosphate. Pyrophosphate extracted greater amounts than any of the other extractants (sodium citrate/dithionite, ammonium oxalate (dark), acid oxalate (UV radiation), as well as those already mentioned). It was concluded that much of the extractable A1 in soils was associated with organic matter. Addition of lime to one of the soils reduced the amount of A1 extracted by all reagents except dithionite and acid oxalate solutions. There were considerable differences between soils in their release of A1 to continuous leaching with 0.01 M CaCl2. Despite these differences between the soils in organically bound extractable Al, the differences in the amounts and patterns of release of A1 with CaCl2did not appear to be related to organic matter contents, nor to the other determined properties.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1986.tb00022.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYThe results of fractionation and correlation studies provided evidence that cobalt in soils is associated predominantly with the soil oxide fraction, particularly the manganese oxides. Only a small proportion of the total cobalt present in soils was extracted by acetic acid, EDTA, pyrophosphate or hydroxylamine. Cobalt extracted with these reagents was considered to be derived principally from easily reducible manganese oxides, although the origin of the cobalt extracted by acetic acid in particular was not well defined. The bulk of the cobalt present in soils appeared to be occluded by more highly crystalline oxide materials or was present in the structures of primary and secondary minerals.Labile cobalt in soil was assessed by extraction with acetic acid and EDTA and by determination of isotopically exchangeable cobalt. The amounts of cobalt extracted by both EDTA and acetic acid were highly dependent on the length of extraction period and on the temperature of extraction. Neither of these reagents appeared likely to give good estimates of the quantity or intensity factors of soil cobalt supply to plants as defined by the isotopic exchange determinations.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1986.tb00023.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYThe effect of four lime levels and of five ratios of Ca: Mg on nodulation, nitrogen fixation and yield of soyabean var. UFV‐1 was studied under greenhouse conditions, using a Typic Haplorthox soil. Dry matter production of top growth was relatively constant for soil Ca: Mg ratios ranging from 0.26: 1 to 24: 1 and a similar production level was sustained for A1 saturation values from 0 to 43%. Nodulation (number and dry weight of nodules) increased with increasing A1 saturation from 0 to 43%. The greatest increase was observed when Al saturation was raised from 0 to 2 or 3%. The N accumulated in the shoots, decreased with the increase in the percent A1 saturation, showing that the largest number of nodules does not necessarily result in greatest accumulation of N in shoot

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1986.tb00024.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYFour soils with a range of clay and silt contents were incubated for 5 a with15N‐labelled (NH4)SO4and14C‐labelled hemicellulose and then fractionated according to particle size by ultrasonic dispersion and sedimentation. The distribution of labelled and native N between clay, silt and sand fractions was determined and elated to previous results on the C distributions.Between 29% and 48% of the added N was found in organic form. The15N atom percentage excess decreased in the order: clay>whole soil>silt>sand. For both clay and silt, the enrichment factor for labelled and native N decreased with increasing fraction weight. Clay enrichment was higher for labelled than for native N, the converse being true for silt. The distribution of whole soil labelled organic N was: clay 77–91%, silt 4–11%, and sand<0.5%. Corresponding values for native N were 69–74%, 16–22%, and 1–2%, respectively.All soils had higher proportions of labelled than of native N in the clay, the converse was true for the silt. The C/N ratio of the native silt organic matter was higher and that of clay organic matter lower than whole soil C/N ratios. Differences between the C/N ratio distributions of native and labelled organic matter were small.The relative distribution of labelled N and C was very similar confirming that the turnover of C and N in soil organic matter is closely

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1986.tb00025.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYAn increase in carbon (C) content of one of the more acid Palace Leas meadow hay plots (pH 4.0) is shown to occur in the>63 pm size fraction, while there is a reduction in organic matter associated with clay size fraction relative to a less acid plot (pH 5.8). Total nitrogen (N) content also is higher on the more acid plot, but the increase is smaller than for carbon, and leads to a wider overall C:N ratio in the acid plot.The lower N accumulation in the more acid plot is due to the relative increase in coarse (>2 mm) organic matter, with a high C:N ratio. The technique used for separation of the particle size fractions does not involve removal of coarse organic matter (>2 mm) or drying of the soil. In the grassland soils studied, coarse organic matter is a significant component (up to 13%) of total C, yet this fraction is frequently removed before analysis. By not drying the soil, separation into particle size fractions is facilitated.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1986.tb00026.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY