bluuebunny/crossref_metadata_2025 huggingface dataset:
Metal-induced chromium(VI) sorption by two calcareous soils
Authors: Echeverría Jesús , Morera Teresa , Garrido Julián
Published: January 2006

Competing anions, notably SO 2- 4 and H2PO- 4 , reduce
Cr(VI) sorption; however, the role of cooperative cations in Cr(VI) retention
has merited less attention. This research studied the effect of Cd, Cu, Ni,
and Zn on sorption of Cr(VI) in 2 calcareous soils: Calcixerollic Xerochrept
(CX) and Paralithic Xerorthent (PX). Sorption kinetics and isotherms were
combined with sequential extractions and fractional factorial designs. Most
cation sorption took place during the first hour, whereas sorption of Cr(VI)
was slower. Without the cooperative presence of these cations, no sorption of
Cr(VI) was detected in the range 0–0·35 mM. Cd, Cu, Ni, and Zn
augmented the sorption of Cr(VI) by the calcareous soils; however, in both
soils the amount of Cr(VI) retained was much lower than cation sorption. In
the presence of cation, sorption of Cr(VI) was first observed at an
equilibrium concentration of 0·07 mM for the CX soil and 0·17 mM
for the PX soil. For higher concentrations, sorption of Cr(VI) by both soils
was described by a constant distribution isotherm. More than 80% of
Cr(VI) sorbed by soils was extracted as a non-exchangeable fraction using the
Tessier et al . sequential procedure. Fractional
factorial designs indicated that although the 4 cations favoured sorption of
Cr(VI), Cu had the greatest positive influence.
The influence of Pinus radiata, Quercus suber, and improved pasture on soil chemical properties
Authors: Noble A. D. , Little I. P. , Randall P. J.
Published: January 2006

Soil acidification and related land degradation issues are assuming increasing
importance in Australia and challenging the concept of sustainability of
current land management systems. In this study, the impacts of tree
plantations of 2 species and permanent pasture on soil chemical properties are
compared. Soil samples were collected from the top 50 cm (0–5,
5–10, 10–15, 15–20, 20–30, and 30–50 cm depths)
from 3 adjacent sites carrying pasture and monocultures of
Pinus radiata (radiata pine) and
Quercus suber (cork oak) on a deep-surfaced yellow
podzolic soil, and differences in soil pH and other soil chemical properties
were examined. In the surface 0–5 cm, pH was similar at all 3 sites.
Below that depth, soil pH was significantly lower and exchangeable Al greater
under the cork oak stand than at the other 2 sites. Consistent with a decrease
in soil pH there was significantly less exchangeable Ca under cork oak. Also,
less clay was observed under the cork oak stand and this is taken as evidence
of the degradational impact of soil acidification.
An estimate of Ca in the top 50 cm of the soil implies considerable loss of Ca
under oak, probably by leaching and loss of litter down the slope. Evidence is
presented to show that there has been more Fe and Al movement under oak than
under pasture and pine, this being ascribed in part to the greater Al and Fe
mobilising capacity of the water-soluble component extracted from freshly
fallen leaf litter of oak. The Fe and Al composition of the oxalate extract
from concretionary material at 10–30 cm under oak is consistent with a
process similar to podzolisation. Pseudogleying of Fe and Al may have
accompanied the leaching of bases from the system and a reduction of pH.
Effect of short-term legume residue decomposition on soil acidity
Authors: Sparling G. P. , McLay C. D. A. , Tang C. , Raphael C.
Published: January 2006

The accumulation of organic matter has been suggested to be one of the causes
of soil acidification. We examined the effect of applying clover shoots,
clover roots, and lupin leaves which differed in concentrations of N and
excess cations/ash alkalinity on the pH of 2 acidic soils from Western
Australia over a 28-day incubation period.
Addition of the legume residues at rates of 1·54 and 3·08
g/kg soil increased soil pH by up to 0·6 units at Day 0 and
0·7 units at Day 28 after incubation. The increase in soil pH was the
greatest with addition of lupin leaves, followed by clover shoots, and the
least with clover roots. The increase in pH correlated well with the amounts
of ash alkalinity added as plant materials. Ammonium concentrations were
generally increased by addition of the plant materials, but with time the
concentrations decreased in the Kojonup soil and increased in the Moora soil.
Nitrate concentrations were similar between the treatments, and increased with
time. Addition of legume residues slightly increased the pH buffer capacity of
both soils at Day 0 but not at Day 28. After 28 days, 37–51% of
clover shoots and 36–51% of lupin leaf had decomposed compared
with 22-38% of clover roots.
The results suggest that rapid changes in soil pH following application of
plant materials are related to the concentration of excess cations and
decomposition of the material and that the application of legume shoot
residues, which usually have high concentrations of excess cations, is not the
likely cause of soil acidification.
Amorphous alumino-silicate materials in a Brazilian hydromorphic lateritic soil
Authors: Varajão Angélica F. Drummond C. , Gilkes Robert J. , Hart Robert D.
Published: January 2006

Two ancient lateritic soil profiles from Brazil that are now experiencing
hydromorphic conditions were investigated by chemical extractions, X-ray
diffraction, differential thermal and thermogravimetric analysis, and
analytical transmission electron microscopy (ATEM) to identify if the
hydromorphic conditions had affected soil minerals. The soils are composed of
gibbsite and kaolinite with less quartz, anatase, goethite, pedogenic
chlorite, and amorphous alumino-silicate phases. These last 2 constituents
occur in the middle and upper horizons of both soil profiles, together with
considerable amounts of organic carbon. Analytical TEM showed that the
amorphous phases enveloped corroded gibbsite and kaolinite crystals and may
indicate the transformation of these minerals to amorphous phases. The
amorphous phases have a similar microfabric to that of allophane and ATEM
analyses of the amorphous phases gave an Al/Si atom ratio that was always
>2, and commonly about 10. These atom ratios are consistent with the bulk
chemical results obtained using pyrophosphate, oxalate, and dithionite
extractants, but not with the theoretical ratio for allophane. The Al/Si
atom ratio of the amorphous phases was related to the Al content of the
mineral enveloped by the amorphous phases, i.e. gibbsite or kaolinite. This
association supports the interpretation that the amorphous phases formed from
the crystalline minerals. The saturated condition of the profiles, together
with the high concentration of organic matter in the upper horizons, favours
dissolution of the original gibbsite and kaolinite in the laterite and their
transformation to amorphous alumino-silicate phases with a high Al content.
Potassium balance and release kinetics of non-exchangeable K in a Typic Haplustert as influenced by cattle manure application under a soybean-wheat system
Authors: Singh Muneshwar , Tripathi A. K. , Reddy D. Damodar
Published: January 2006

Potassium balance and non-exchangeable potassium release in 0.01 M
CaCl2 medium in a Typic Haplustert were studied in a
7-year-old soybean–wheat rotational experiment involving 4 levels of
cattle manure along with the recommended dose of K (66 kg/ha.year).
Continuous cropping without returning crop residues to the soil led to a
negative balance of 66–107 kg K/ha.year. Manuring at the rate of 4
and 8 t/ha did not significantly change the negative balance, but
application of 16 t/ha manure reduced the negative K balance. Continuous
cropping without cattle manure reduced cumulative K release from 236 mg/kg
(initial) to 195 mg/kg. Application of manure at 4, 8, and 16 t/ha
kept K release at 229, 245, and 246 mg/kg soil, respectively. A parabolic
diffusion equation was the best fit to describe K release. Cropping under the
present level of K input resulted in a decline in non-exchangeable K whatever
the addition of manure. Manuring at 4 and 8 t/ha has accelerated the
mining of native K, which increased the unsustainability of the system.
K balance, non-exchangeable K release kinetics, soybean–wheat
rotation, cattle manure, Typic Haplustert.
Note of clarification about: Field and laboratory calibration and test of TDR and capacitance techniques for indirect measurement of soil water content, by P.N.J. Lane and D.H. Mackenzie, Vol. 39, pp. 1371-1386
Authors: Lane P. N. J. , Mackenzie D. H. , Nadler A. D.
Published: January 2006

Time domain reflectometry (TDR) and a frequency domain sensor, the Didcot
Capacitance Probe, were tested in the field and laboratory. The results from
an undisturbed large core TDR laboratory test found the Topp equation returned
a close correspondence to thermogravimetrically derived water content,
although there was a slight underestimation. Coefficients of determination and
efficiency were >0.98 and 0.92, respectively, for individual cores, and
0.98 and 0.97 for the whole data set. The field exercise revealed the Topp
equation to be superior to the laboratory derived equation and other published
empirical equations, suggesting the Topp equation to be adequate. A field test
of the capacitance probe found poor correspondence between measured and
predicted observations of profile point soil water content. Although
81% of the variance was explained by the calibration regression, there
was a poor fit to the 1:1 line (E = 0.34), and a
non-significant relationship between measured and predicted soil water content
for the A horizon. The instrument design proved problematic for use as a
determiner of point profile soil water content, and the recommended
calibration procedure was impossible in the study site soils.
Nitrogen fluxes in surface soils of young Eucalyptus nitens plantations in Tasmania
Authors: Moroni M. T. , Smethurst P. J. , Holz G. K.
Published: January 2006

Nitrogen (N) fluxes in surface soils (0–10 cm) were measured by an
in situ soil-core technique at 5 sites supporting 1- to
4-year-old Eucalyptus nitens plantations in Tasmania.
Rates of net N mineralisation (NNM) ranged from 13 to 188 kg N/ha.year.
The highest rate was from an ex-pasture site, which was almost double the
highest rate of NNM measured on an ex-forest site. Although there was a
tendency towards lower rates of NNM in uncultivated versus cultivated soils,
and in the final versus previous year or two of measurement, these differences
were not significant. Concentrations of mineral N, however, decreased at all
study sites during the first 3–4 years, significantly at 4 of these
sites. Within the errors of measurement, most N that was mineralised was also
nitrified and leached. Seasonal patterns in NNM and concentrations of nitrate
(NO3–) occurred only at one
site, which also had the highest annual rate of NNM. The balance of mineral N
remaining in surface soil each October was 2–17 kg N/ha. We
concluded that there was little evidence of a decrease in rates of NNM between
1 and 4 years after planting, and that high rates of NNM at some sites were
accompanied by high rates of leaching that limited the accumulation of mineral
N. Sitespecific management of N fertiliser may be warranted to compliment the
wide range of N availability in eucalypt plantations.
mineralisation, nitrification, leaching, uptake, forests,
Australia.
Indigenous soil and water conservation techniques: effects on runoff, erosion, and crop yields under semi-arid conditions
Authors: Wakindiki I. I. C. , Ben-Hur M.
Published: January 2006

A joint contribution from the Department of Soil Science, Egerton University,
PO Box 536, Njoro, Kenya, and the Agricultural Research Organization, the
Volcani Center, Israel, No. 603/01, 2001 series.
Smallholder farmers in arid and semi-arid regions use indigenous soil and
water conservation (ISWC) techniques, such as trash lines and stone lines
spaced about 15 m apart across the slope. This work evaluated the effects of
size of trash lines and decreasing the space between trash or stone lines to 2
m on runoff, erosion, and corn and cowpea yields. Big trash line (BTL), small
trash line (STL), and stone line (SL) techniques, and a control (no ISWC
technique) were evaluated in 12 runoff plots (2 by 6 m each) with 10%
slope in a semi-arid area in Kenya, during 5 consecutive rainy seasons. The
ISWC techniques significantly (P ≤ 0.05) decreased runoff and soil loss,
and increased corn and cowpea yields, compared with the control treatment in
most of the rainy seasons. The BTL was, in general, the most effective
technique; no consistent differences were found between the STL and SL
techniques. In BTL, STL, SL, and control, the seasonal average runoff for each
treatment was 25, 31, 29, and 51 mm, respectively; the seasonal average soil
loss was 0.23, 0.33, 0.3, and 0.67 Mg/ha, respectively; and the seasonal
average biomass (grain and stover of corn and cowpea) was 4.8, 4.0, 4.0, and
2.5 Mg/ha, respectively. The seasonal biomass increased linearly and
significantly (P ≤ 0.01) with increasing water infiltration. As more water
infiltrated, more water was available for crop production, and the yield was
higher.
trash lines, stone lines, steep land, seal formation.
Loss of mass and nitrogen from biosolids applied to a pine plantation
Authors: Robinson M. B. , Polglase P. J. , Weston C. J.
Published: January 2006

Application of biosolids (sewage sludge suitable for beneficial use) to tree plantations has the potential to increase productivity, but also to leach nitrogen (N) if application rates are excessive. This project aimed to determine rates and mechanisms of loss in mass and N from 3 dewatered biosolids (1 from aerobic and 2 from anaerobic digestion of waste water) applied to the surface of a radiata pine plantation. Biosolids were applied at operational rates (nominally 30�dry�t/ha), supplying between 965 and 1425 kg N/ha, of which 210–550 kg/ha was NH4+-N.

Results showed that, for mass, biosolids were characterised by 2 discrete pools, an active pool comprising 52–67% of total mass, and a pool that can be considered inert within the time frame of 5 years. Most of the active organic matter and carbon was lost within 2 years; much of the loss of total mass was derived from the inorganic pool.

There was a large and rapid loss of total N from biosolids during the first 3 weeks after application, most of which was accounted for by depletion of NH4+-N, presumably by volatilisation. Much of the subsequent release of N was apparently through mineralisation, with 300 kg/ha (anaerobically digested) to 500 kg/ha (aerobically digested) being released in the first year.

Applications at these rates have the potential to contaminate waterways with N in the first year after application, the risk being greatest from aerobically digested biosolids. In subsequent years there appears to be little risk. However, applications at lower rates appear well suited to forests, with a small proportion of the inorganic N providing an initial input to soil and mineralisation of organic N providing a steady supply to the plantation over a number of years.
Effect of soil type, exchangeable sodium percentage, water content, and organic amendments on urea hydrolysis in some tropical Indian soils
Authors: Wali Pardeep , Kumar Vinod , Singh J. P.
Published: January 2006

Urea has emerged as one of the most extensively used sources of nitrogen fertiliser in recent years because of its low cost per unit nitrogen. Urea hydrolysis in soils is an enzymatic decomposition process by the enzyme urease. The effects of soil type, exchangeable sodium percentage, moisture regime, and organic manures and their levels on the kinetics of urea hydrolysis were studied in a series of laboratory incubation experiments at 25 ± 1�C. Urea transformation followed first-order kinetics, and the first-order rate constants for soils varied from 0.0321 to 0.1182/h. The rate of urea hydrolysis in the different soils increased with greater clay content and followed the order: Gulkani clay loam > Dadupur loam > Hisar sandy loam > Jakhol silty clay loam > Bawal loamy sand > Balsamand sand. Increasing the exchangeable sodium percentage in soils decreased the rate of urea hydrolysis both at field capacity and flooded conditions (2 cm standing water). Application of vermicompost, sheep manure, poultry manure, pig manure, and urban waste to soil at the 1% level increased the rate of hydrolysis over the untreated soil.
Sulfide oxidation and acidification of acid sulfate soil materials treated with CaCO3 and seawater-neutralised bauxite refinery residue
Authors: Ward Nicholas J. , Sullivan Leigh A. , Bush Richard T.
Published: January 2006

Acid sulfate soil (ASS) materials that are subject to oxidation are often treated with neutralising agents to minimise the export of acidity that may result from pyrite oxidation. The effects of additions of both CaCO3 and seawater-neutralised bauxite refinery residue (SNBRR) on the oxidation of sulfides and acidification were assessed for 4 ASS materials using laboratory incubation experiments. As the application of sub-optimal rates of neutralising materials can occur for a variety of reasons, the effect of application rates were also examined. Two application rates were chosen; a sub-optimal rate [approximately 20% of the theoretical neutralising requirement (NR)] and an excessive application rate (>250% of the NR). There was minimal sulfide oxidation and no acidification after the addition of excess CaCO3 over the 180 days of incubation. The addition of excess SNBRR prevented acidification, but substantial sulfide oxidation still occurred. Following a brief initial increase in pH when sub-optimal rates of CaCO3 and SNBRR were applied, the treated ASS materials rapidly acidified. For three of the ASS materials the addition of sub-optimal amounts of CaCO3 had little impact on the rate of sulfide oxidation. However, for the other ASS material (a peat) both the rates of sulfide oxidation and acidification were accelerated by the addition of sub-optimal rates of CaCO3, resulting in higher soluble Fe and Al concentrations than in the untreated ASS materials. For some of the ASS materials, sub-optimal applications of SNBRR resulted in elevated soluble Al.
ASRIS: the database
Authors: Johnston R. M. , Barry S. J. , Bleys E. , Bui E. N. , Moran C. J. , Simon D. A. P. , Carlile P. , McKenzie N. J. , Henderson B. L. , Chapman G. , Imhoff M. , Maschmedt D. , Howe D. , Grose C. , Schoknecht N. , Powell B. , Grundy M.
Published: January 2006

The Australian Soil Resources Information System (ASRIS) database compiles the best publicly available information available across Commonwealth, State, and Territory agencies into a national database of soil profile data, digital soil and land resources maps, and climate, terrain, and lithology datasets. These datasets are described in detail in this paper. Most datasets are thematic grids that cover the intensively used agricultural zones in Australia.
A comparison of rubber-tyred and steel-tracked skidders on forest soil physical properties
Authors: Sheridan G. J.
Published: January 2006

Compaction of a silty clay loam forest soil was compared for 2 types of log-skidding equipment, a rubber-tyred skidder and a flexible-steel-tracked skidder. Experiments involved the loaded skidders traversing marked laneways at zero, 2, 4, and 10 passes. Compaction was quantified in terms of 3 parameters: (1) bulk density to 25 cm depth measured gravimetrically, (2) penetration resistance using a field penetrometer, and (3) saturated hydraulic conductivity using a field rainfall simulator. Results showed no substantial difference in soil bulk density between the experimental treatments, regardless of skidder type or number passes. Penetration resistance of the traversed laneways was significantly higher than the surrounding undisturbed areas; however, there was no difference between skidder type. Rainfall simulation showed that the saturated hydraulic conductivity of all treatments was strongly reduced by trafficking, although this did not differ with skidder type. The results from this study highlight the dangers in assuming that reduced machine static ground pressures will automatically lead to reduced soil impacts. It is important to note that while this study did not find differences between the 2 skidder types when operated in a similar manner, differences in the operation of the two skidders may also influence impacts on soil properties.
A slowly soluble, sulfur fertiliser from a by-product of mineral sands processing
Authors: Summers Robert , Clarke Martin , McCafferty Peter , Pope Tim
Published: January 2006

The effectiveness of a pelletised by-product from mineral sands processing as a sulfur fertiliser was measured on high rainfall sandy soils of Western Australia. The by-product was a lime-neutralised, low-grade, sulfuric acid effluent which produces a precipitate of gypsum containing iron and manganese. The pelletised product has been given the name 'Ironman' gypsum, reflecting its major constituents. Ironman gypsum was compared with ordinary single superphosphate and naturally occurring gypsum from Wyalkatchem (fine) and Jurien Bay (coarse) as a sulfur fertiliser in 2 field experiments.When comparing the relative rates of sulfur release as indicated by plant yield and nitrogen:sulfur ratio, the order of effectiveness was: superphosphate = Ironman gypsum pellets >> coarse gypsum ≥� unpelletised by-product >>Wyalkatchem gypsum. Laboratory leaching studies showed the Ironman pellets to leach more slowly than superphosphate, which in turn leached more slowly than coarse rock gypsum. The soil sulfur tests were of limited value in predicting yield even though they were accurate in predicting the amount of sulfur previously applied.Compared with an unfertilised control, Ironman gypsum did not result in a significant increase in the uptake of heavy metals by plants. Most of the elements of concern, mercury, cadmium, and uranium, actually showed a significant reduction in concentration in the plant matter. This was probably due to the increased growth caused by the improved sulfur nutrition resulting in dilution of these elements. There was a slight but statistically significant increase in the nickel concentration that could be attributed to Ironman gypsum, but the level was still low.
Size distributions and minimum Stokes diameters of soil particles
Authors: Emerson W. W.
Published: January 2006

Published data on the settlement of particles in soil suspensions were used to plot the percentage by weight of particles (P) with a Stokes diameter ≤D v. log D. For subsoils, P/log D plots became linear as D approached the limit of measurement of 60 nm. This allowed linear extrapolation to P = 0. The D value of a clay particle was converted to particle radius by assuming particles to be circular plates with a constant ratio of radius to thickness of 2.5. When the linear plot plus its extension covered the whole clay range, calculated surface areas of the clay were then consistent with reported values. The smallest value of D found by extrapolation was 5 nm. It was deduced to correspond to a single sheet of beidellite with 2 water layers on each surface. Plots for samples from a different horizon of the same profile were used to obtain a second estimate of the minimum value of D.Over the silt/fine sand range, plots for subsoils could also be linear, but often were partly sigmoidal due, for example, to the presence of loess. Separate plots for the clay minerals and loess were deduced from the P/log D plot for one sample using the reported mineralogical composition of different size fractions.
A laboratory study of phosphorus mobilisation from commercial fertilisers
Authors: Nash D. , Hannah M. , Clemow L. , Halliwell D. , Webb B. , Chapman D.
Published: January 2006

Phosphorus (P) exported from pastures following fertiliser application contributes to the nutrients and associated problems in the streams and rivers of south-eastern Australia. This laboratory study examined whether attributes of P fertilisers may affect P exports soon after their application to field soils; 3 commercial fertilisers [diammonium phosphate (DAP), single superphosphate (SSP), and sulfur-coated single superphosphate (CSSP)] were applied to 2 repacked soils (Arawata and Ellinbank) at 5 moisture contents.Soil type was the most important factor affecting water-extractable P (expressed as a percentage of the P added as fertiliser), accounting for 30% of the total variation. The majority of this variation is explained by the water-extractable P concentrations in the Arawata low moisture treatments. These treatments [7, 6, and 6% soil moisture when equilibrated at 99, 95, and 86.5% relative humidity (RH), respectively] contained water-extractable P concentrations c. 3 times higher than the high moisture (c. 20 and 25% soil moisture) or the Ellinbank treatments. This result probably reflects differences in soil properties including the extent of water repellency and P adsorption.Fertiliser type explained only 6.9% (P < 0.001) of the total variation in water-extractable P, partially as a result of the 86.5% RH (a low moisture) Arawata treatment. In this Arawata low moisture treatment, the mean extractable P was similar for both DAP and SSP, 13.1% [least significant interval (l.s.i.) 16.7–10.3] and 11.3% (l.s.i. 14.3–8.9), respectively, but for SSP, water-extractable P increased over time unlike any other treatment. Water-extractable P from DAP was approximately double that from SSP for the Ellinbank and high moisture treatments. The higher water-extractable P following DAP application is explained in terms of its chemical properties and reaction products. Sulfur coating the SSP granules (CSSP) increased water-extractable P, as did higher soil moisture.This study suggests that under conditions present in most pastures in south-eastern Australia and depending on soil hydrology, water-extractable P and P export from fertilisers may increase in the order DAP > CSSP > SSP if overland flow occurs soon after their application.
Soil solution chemistry of contrasting soils amended with heavy metals
Authors: Percival H. J. , Speir T. W. , Parshotam A.
Published: January 2006

The soil solution chemistry of heavy metal amended soils is of great
importance in assessing the bioavailability of heavy metals and their toxicity
to the soil biota. Three contrasting soils were amended with Cd(II), Cu(II),
Ni(II), Pb(II), Zn(II), and Cr(III) nitrate salts at rates of 10–100
mmol/kg. This concentration range was chosen to encompass a wide range of
effects on sensitive soil biochemical properties as part of a larger project.
Soil solutions were extracted and analysed for pH, and for concentrations of
heavy metals, and major cations and anions. Heavy metal speciation was
calculated with the GEOCHEM-PC model.
Heavy metal concentrations in the soil solutions increased both in absolute
terms and as a percentage of added heavy metal as amendment rates increased.
This observation is due to decreasing specific adsorption (caused by
decreasing pH induced by the amendments), and to increasing saturation of
cation exchange sites. For all 3 soils, the percentage increase commonly
follows the order Cr(III) < Pb < Cu < Ni < Cd < Zn. The
percentage of each metal held in the soil solution increased from soil to soil
as cation exchange capacity, and therefore sorptivity, decreased.
Both the concentration and activity of free heavy metal ions were
substantially lower than the corresponding total metal concentration. This was
ascribed to ion-pairing of metal ions with anions, particularly nitrate
introduced in the amending solutions, as well as to increases in ionic
strength as a result of amendment. Metal-anion species were mainly inorganic
but where Cu and Pb were relatively low in concentration because of strong
adsorption by the soils, organic complexation was likely to be significant.
Speciation trends were similar for the 3 soils but different in magnitude.
Development of soil morphological descriptors to improve field estimation of hydraulic conductivity
Authors: Griffiths E. , Webb T. H. , Watt J. P. C. , Singleton P. L.
Published: January 2006

The wide application of hydraulic conductivity data depends on linking
hydraulic parameters to soil morphology. Conventional morphology has been
found to be a poor predictor of hydraulic conductivity. In this study we
present new methods of characterising soil morphology to provide key
morphological descriptors that can be related to hydraulic conductivity.
Relationships were established between morphological properties (macrovoids,
ped size, and associated surface features), and in situ consistence (degree of
packing) with measured saturated and near-saturated hydraulic conductivity
(Ks and
K−40). These relationships
were applied to estimate Ks and
K−40 classes for soil
horizons of pedal and apedal soils. In pedal soils, K is
estimated from the area of macrovoids and from the proportions of
different-sized peds in each horizon, their closeness of fit, and their degree
of packing. Low packing and fine peds with rough surfaces is indicative of
rapid conductivity, whereas high packing and coarse peds with smooth/shiny
ped surfaces is indicative of slow conductivity. In apedal soils,
K is estimated from the area of macrovoids and from
degree of packing and particle-size class. Low packing with coarse particles
indicates rapid conductivity, whereas high packing with fine particles
indicates slow conductivity.
Field characterisation of soils to determine functional morphology requires:
(i) a dye to measure extent and continuity of cracks and
macrovoids; (ii) a metal blade (Singleton Blade) and a
hand-held penetrometer to measure soil consistence in situ; and
(iii) weighing different-sized peds and describing their
surface features.
Short rotation forestry for land treatment of effluent: a lysimeter study
Authors: Roygard J. K. F. , Bolan N. S. , Clothier B. E. , Green S. R. , Sims R. E. H.
Published: January 2006

Land treatment of wastewater using short rotation forestry (SRF) has potential
as a sustainable method for disposal of dairy-farm euent. We compared 3 SRF
species, 2 evergreen species of eucalypts
(Eucalyptus nitens, E. saligna)
and a deciduous willow (Salix kinuyanagi), in the land
treatment of dairy-farm euent. The trees were grown in lysimeters (1 . 8
m diameter, 1 . 0 m depth), and a bare soil treatment was used as a
control. The application of dairy-farm oxidation-pond euent totalled 218 g
N/lysimeter (equivalent to 870 kg N/ha) over 2 irrigation seasons
(December 1995–June 1996 and September 1996–April 1997). Euent was
applied weekly in summer at a rate of 18 . 9 mm/week. No euent was
applied during the winter period. The evapotranspiration (ET) rates of the
trees, and the volumes and nitrogen contents of the leachates are compared for
a winter period (4 weeks) and a summer period (5 weeks). The biomass
accumulation and the uptake of nitrogen by the 3 tree species were also
investigated.
The SRF trees improved the renovation levels of dairy-farm euent and produced
biomass suitable for energy conversion. Of the 3 tree species, only the
S. kinuyanagi treatments maintained leachate nitrate
concentrations below the New Zealand drinking water standard of 11 . 3 mg
NO– 3 -N/L throughout
both the winter and summer periods. The E. nitens
treatment produced significantly more oven-dry biomass (19 . 1
kg/tree) than the E. saligna trees (9 . 7
kg/tree) (P = 0 . 05). The
S. kinuyanagi treatment had intermediate production (13
. 3 kg/tree) and was not significantly different from the other 2
tree species (P = 0 . 05). The nutrient
accumulation was not significantly different among the species
(P = 0 . 05).
S. kinuyanagi was considered the best overall performer
for the land treatment of dairy-farm euent, based on the concentrations of
leachate moving beyond the root-zone.
The relationship between soil solution pH and Al3+concentrations in a range of South Island (New Zealand) soils
Authors: Adams M. L. , Hawke D. J. , Nilsson N. H. S. , Powell K. J.
Published: January 2006

Concentrations of Al3+ were calculated in soil
solutions from concentrations of the monomeric ‘reactive Al’
species ([Al3+] +
[Al(OH)2+] +
[Al(OH)2+] +
[AlF2+]) obtained using a recently
reported flow injection analysis (FIA) chelating resin technique. Soil
solution samples came from 7 sites encompassing a range of New Zealand soils
(Brown, Gley, Pallic, Podzol, and Recent Soils) and vegetation types (pasture,
shrub lands, and indigenous and exotic forest). Previously published data from
a further 7 sites, obtained using a rapid (7 s) FIA technique, were
transformed to give compatible results. The resultant data
(n = 85) covered the pH range 2.7–7.6, and
showed a single curvilinear relationship for log
[Al3+] v. soil
solution pH, regardless of vegetation or soil type. At pH >5.6, the data
had a slope of –2.98 and fell between the amorphous
Al(OH)3 and gibbsite solubility lines. At pH <5.0,
the data had a slope of –0.46; further, the soil solutions were
under-saturated with respect to both minerals. These results are interpreted
as indicating control of Al solubility by Al(OH)3 (s)
(at pH >5.6) and soil organic matter (at pH <5.0), respectively. This
interpretation is supported by data from a pH-dependent Al–fulvic acid
binding curve, for which calculated values of
[Al3+] follow the same curvilinear
relationship determined from the soil solution samples.
Effects of cattle treading on physical properties of three soils used for dairy farming in the Waikato, North Island, New Zealand
Authors: Singleton P. L. , Addison B.
Published: January 2006

A study of the physical condition of 3 soils used for intensive dairy farming
in the Waikato Region was undertaken. The study was to determine the existing
physical condition of the soil, the possible long-term changes from pugging
damage, and the most appropriate measurements and depth for monitoring change
in soil physical properties under dairying.
Four dairy farms were selected on each of 3 soils (an Allophanic Soil and 2
Gley Soils). On each farm, 3 sites that corresponded to never trodden, usual
(‘average’ paddock and pasture condition for the farm), and
previously pugged (pugged >18 months ago) pasture histories were sampled.
Undisturbed soil cores were collected at 50-mm depth increments to 250 mm for
determination of bulk density, total porosity, saturated and unsaturated
hydraulic conductivity, proportion of pores >30 and 60
µm, and aggregate size class.
Results showed pugging was having a long-term effect on soil physical
properties of all 3 soils, including the well-drained Allophanic Soil that
rarely pugged. All measurements showed a decline in values for soil properties
from never trodden to previously pugged. The greatest changes were in
hydraulic conductivity, proportion of pores, and aggregate size (>60 and
<20 mm).
The most appropriate depth increment for measuring differences between
treatments was found to be 50–100 mm. A comparison of previously pugged
to never trodden at this depth showed that hydraulic conductivity had
decreased by 80%, pore size by 46% (except for Allophanic Soil),
and the proportion of aggregates >60 mm in diameter had increased at least
4-fold.
Farming practices that minimise pugging damage, such as on/off grazing,
need to be encouraged. It is possible that such programs may permit the soil
to recover to a physical state similar to never trodden sites.
Influence of moist - dry cycles on pH changes in surface soils
Authors: Paul K. I. , Conyers M. K. , Black A. S.
Published: January 2006

It is well established that in the moderately acidic soils of southern
Australia, the 0–2 cm layer commonly has a higher pH than soil layers
between 2 and 10 cm depth. The surface 2 cm of soil is also exposed to much
greater fluctuations of moisture content than deeper soil layers. There are
contradictory or speculative reports in the literature on how soil moisture
fluctuation affects pH and processes which influence pH. Therefore, the aim of
this study was to determine the effect of moist–dry cycles on pH, and on
processes involving H+ transformations, in 3
surface soils (0–2 cm) sampled from southern New South Wales.
Following a pre-incubation, the 3 surface soils were incubated for 28 days at
30°C and were: (i) maintained continuously dry, (ii) subjected to short (2
days dry, 5 days moist) or long (7 days dry, 7 days moist) moist–dry
cycles, or (iii) maintained continuously moist.
During the incubation, the pH of continuously dry soil slightly increased by
0.03–0.10 units, while the pH of continuously moist soil decreased by
0.16–0.39 units. In soils subject to both short and long moist–dry
cycles, the pH decreased by 0.06–0.34 units. However, relative to soils
maintained moist, exposure to moist–dry cycles suppressed acidification
by 0.05–0.26 pH units.
In dry soils the pH increased, since some of the
NH4+-N produced by net N
mineralisation was not subsequently nitrified, and there was a net reduction
of Mn. In soils which received water, acidification was predominately
attributed to nitrification. Relative to soils maintained moist, acidification
was suppressed by 1.6–6.5 mmol H+/kg due
to the 11–35% decrease of nitrification on exposure to
moist–dry cycles. In acidic surface soils (pH <5.5), acidification
rates were further suppressed by 0.1–1.0 mmol
H+/kg due to the 1.06–2.06 times greater
net Mn reduction in moist–dry soils than in continuously moist soils.
Differences in particle density between field-moist and oven-dry samples from Allophanic Soils
Authors: Addison B. , Boyes M. , Singleton P. L.
Published: January 2006

Particle density is used to calculate total soil porosity and related
measurements such as macroporosity and water storage capacity. Methods for
measuring particle density often advise using dry samples. This study measured
particle density by displacement of water using both field-moist and oven-dry
samples from 4 New Zealand Allophanic Soils. There were significant
differences in particle density between the 2 methods. Oven-dry samples
under-estimated particle density by up to 0.33 Mg/m
3 and as a result, calculations of porosity were
under-estimated by up to 0.05 m 3/m
3 . Under-estimation of porosity can result in incorrect
interpretation of a soil's aeration and water holding status. Allophanic
Soils are known to undergo irreversible physical changes on drying and it is
likely that these changes caused the difference in measurements. Only
field-moist samples should be used to determine particle density of Allophanic
Soils to ensure accurate calculation of soil porosity.
Clay mineralogy as affecting disaggregation in some palygorskite containing soils of the Jordan and Bet-She'an Valleys
Authors: Neaman Alexander , Singer Arieh , Stahr Karl
Published: January 2006

The influence of clay mineralogy on disaggregation in some
palygorskite-containing soils of the Jordan and Bet-She'an Valleys was
examined. The disaggregation potential of different minerals in the soil clay
fraction was investigated by establishing differences in the mineral suite
between the original and disaggregated clay fractions. By shaking the soil
with distilled water, calcite, dolomite, feldspar, and palygorskite were
disaggregated preferentially. The pattern for quartz was inconsistent. Among
phyllosilicates, palygorskite was the most strongly, disaggregated, while
smectite was the least disaggregated mineral. The disaggregation potential of
kaolinite was of intermediate value. By shaking the soil with 0 ⋅ 01 N
NaCl, calcite and dolomite were released preferentially, and were the dominant
minerals in the disaggregated clay fraction. Scanning electron microscopy
observations indicate that palygorskite fibres do not associate into
aggregates in soils and suspensions, even when saturated with calcium ions.
The present findings are relevant for soils with low exchangeable sodium
percentage. These soils can be expected under rain-fed agriculture or
irrigation with high quality water which has a low sodium adsorption ratio.
Isotopic dilution methods to determine the gross transformation rates of nitrogen, phosphorus, and sulfur in soil: a review of the theory, methodologies, and limitations
Authors: Di H. J. , Cameron K. C. , McLaren R. G.
Published: January 2006

The rates at which nutrients are released to, and removed from, the mineral
nutrient pool are important in regulating the nutrient supply to plants. These
nutrient transformation rates need to be taken into account when developing
nutrient management strategies for economical and sustainable production. A
method that is gaining popularity for determining the gross transformation
rates of nutrients in the soil is the isotopic dilution technique. The
technique involves labelling a soil mineral nutrient pool, e.g.
NH4+,
NO3−,
PO43−, or
SO42−, and monitoring the
changes with time of the size of the labelled nutrient pool and the excess
tracer abundance (atom%, if stable isotope tracer is used) or specific
activity (if radioisotope is used) in the nutrient pool. Because of the
complexity of the concepts and procedures involved, the method has sometimes
been used incorrectly, and results misinterpreted. This paper discusses the
isotopic dilution technique, including the theoretical background, the
methodologies to determine the gross flux rates of nitrogen, phosphorus, and
sulfur, and the limitations of the technique. The assumptions, conceptual
models, experimental procedures, and compounding factors are discussed.
Possible effects on the results by factors such as the uniformity of tracer
distribution in the soil, changes in soil moisture content, substrate
concentration, and aeration status, and duration of the experiment are also
discussed. The influx and out-flux transformation rates derived from this
technique are often contributed by several processes simultaneously, and thus
cannot always be attributed to a particular nutrient transformation process.
Despite the various constraints or possible compounding factors, the technique
is a valuable tool that can provide important quantitative information on
nutrient dynamics in the soil–plant system.
Corrigendum to: A comparison using the caesium-137 technique of the relative importance of cultivation and overland flow on soil erosion in a steep semi-tropical sub-catchment
Authors: Wiranatha A. S. , Rose C. W. , Salama M. S.
Published: January 2006

The spatial pattern of net soil loss on 6 downslope transects in a small
semi-tropical sub-catchment was measured in 1990—91 using the
resident caesium-137 deficit technique. The sub-catchment consisted of 2
opposing hillslopes which shed water to an intermittent stream in the valley
bottom of the sub-catchment. There were 3 transects on each of the opposing
hillslopes, and measurement indicated net soil loss from all 6 transects.
Furthermore, the spatial pattern of caesium-137 deficit did not indicate the
accumulation of soil expected due to the slope decrease toward the bottom of
the valley. Possible explanations of this finding could be the effect of
periodic flooding of the intermittent valley stream, or seepage-accelerated
erosion.
Pineapple cultivation in the sub-catchment since 1950 included intensive
cultivation at 4-year intervals by downslope-moving rotary hoe. The paper
develops a theoretical prediction of the spatial pattern of net soil loss
expected due to such cultivation, as well as the expected pattern of soil loss
due to overland flow on the hillslopes. The spatial patterns of soil loss due
to these 2 different soil erosion mechanisms were then compared with the
pattern of net soil loss indicated by caesium-137 depletion to provide an
assessment of their likely relative importance in contributing to soil loss.
In the upper part of each hillslope, this comparison of spatial trends did not
allow the dominant cause of soil erosion to be distinguished. Both the model
of erosion due to cultivation and that due to hillside overland flow predicted
soil accumulation in the lower valley sides where slope decreased. Neither
model represented the net loss of such accumulated soil indicated by
caesium-137 deficit, and this loss possibly occurred during periodically
observed flooding of the valley floor, or due to surface burial with
caesium-137 depleted subsoil.
Soil moisture profile estimation from surface measurements at multiple frequencies
Authors: Keam R. B. , Holdem J. R. , Schoonees J. A.
Published: January 2006

It is possible to obtain estimates in situ of volumetric
soil moisture content (SMC) as a function of depth using measurements of radio
wave reflection at the soil surface at several discrete frequencies. The
feasibility of the method was demonstrated through computer simulation by
deriving empirical relationships between the number of frequencies, the
frequency range, and the number of soil layers for which the SMC is estimated.
The SMC profile was obtained to a depth of 1.5 m by inverting, through
function minimisation, a simulation of the reflection coefficient from layered
dielectric materials. The number of soil layers in which SMC could be resolved
was found to be twice the number of frequencies used. The required bandwidth
increased with the number of soil layers from 20 MHz for 6 layers to 140 MHz
for 16 layers. Within some assumptions about the nature of the radio wave
propagation, the theoretical accuracy of the estimate depended only on the
quantisation error introduced by having to consider discrete layers of uniform
soil with finite thicknesses. The method may have potential for enabling
sensitive measurements of SMC profiles at lower cost and lower complexity than
methods which use analysis of steps or pulses, such as time-domain
reflectometry, and should be well suited for routine use by horticulturists
and soil researchers.
Restorative crops for the amelioration of degraded soil conditions in New Zealand
Authors: Francis G. S. , Tabley F. J. , White K. M.
Published: January 2006

The effects of restorative crops on the amelioration of a degraded soil were
investigated in a 6-year field experiment. Treatments included perennial
pastures, annual pastures, and arable crops. Improvements in some aspects of
chemical, biological, and physical fertility were related to the amount of
herbage dry matter returned to the soil and root production. Beneficial
effects associated with returned organic matter were partly negated by the
degradative effect of tillage. Treatments that returned most organic material
to the soil showed the greatest increase in aggregate stability and supported
the largest earthworm populations, especially without annual tillage.
Differences between treatments in soil organic C content were not generally
significant until the sixth year. In contrast, differences between treatments
in microbial biomass C were apparent by the third year. Compaction by sheep
during grazing appeared to result in a loss of soil macroporosity. In the
sixth year, soil macroporosity was greatest in the annually cultivated,
ungrazed treatments. The grazed perennial ryegrass and ryegrass/white
clover treatments were the most effective in ameliorating degraded soil
conditions. The rate of soil amelioration declined with depth, and was mainly
confined to the top 10 cm of soil. The rate of amelioration was relatively
slow, with, for example, 3 years needed for most of the increase in aggregate
stability at 0–5 cm depth.