bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil responses to sodicity and salinity: challenges and opportunities
Authors: Oster J. D. , Shainberg I.
Published: September 2002

Exchangeable sodium and low salinity deteriorate the permeability of soils to
air and water. The susceptibility of soils to sodicity and low salinity depend
on both the inherent properties of the soils (e.g. texture, mineralogy, pH,
CaCO3, sesquioxides, and organic matter content) and
extrinsic, time-dependent properties (e.g. cultivation, irrigation method and
wetting rate, antecedent water content, and the time since cultivation).
Whereas the effect of inherent soil properties on the soil response to
sodicity has been studied and modelled, especially under laboratory
conditions, the effect of soil management on the physical response of soils to
sodicity has been studied very little. Consequently our ability to predict the
changes in soil permeability under field conditions is limited. Including the
effect of management on the physical response of soils to sodicity and low
salinity is the main challenge facing researchers, consultants, and farmers.
Effects of grassland afforestation on exchangeable soil and soil solution aluminium
Authors: Adams M. L. , Davis M. R. , Powell K. J.
Published: September 2002

The impact of land use change from grassland to conifer forest on the
aluminium (Al) concentrations in soils and soil solutions was examined. Soils
from grassland were compared with those from adjoining 15–19-year old
forest stands at 3 contrasting pairs of sites in South Island, New Zealand.
The site pairs were on a terrace
[Pinus nigra/P. ponderosa,
and grassland (CP)], and a hill slope
[Pseudotsuga menziesii and grassland
(CF)] in the Craigieburn range, Canterbury, and a hill slope in the
Lammerlaw Range, Otago [P. radiata and
grassland (LP)]. The sites had never been
cultivated or fertilised, and for each pair the forest and grassland were
similar in terms of soil and topography.
The 1 M KCl exchangeable and 0.02 M CaCl 2 extractable
Al levels at 0–10 cm were higher in forest than in grassland topsoil at
CP and LP (P < 0.01). In soil solutions there was
a trend for both ‘reactive Al’ and Al bound in labile organic
complexes to be higher in forest soil at all sites, but site-pair differences
were only significant at LP, and only for ‘reactive Al’. The
increase in ‘reactive Al’ at this site was linked to the low pH
and low base saturation. The ratios of exchangeable and soil solution Ca
2+ and Mg 2+ to
‘reactive Al’ were substantially lower in forest than grassland
soils at all sites.
Aluminium complexation capacity (Al-CC) values at all sites were higher in
forest soil solutions than in grassland soil solutions. For the grassland and
forest sites at LP, the Al-CC correlated strongly with the amount of soluble
fulvic and humic matter present, as estimated from soil solution UV absorbance
at 250 nm.
In soils with the lowest percentage base saturation and buffering capacity
(LP), afforestation of pastoral grassland with
Pinus radiata significantly reduced soil pH and base
cation levels, while increasing both soil and soil solution Al concentrations.
Under such conditions (base saturation <20%), the increase
in ‘reactive Al’ concentrations in soil solutions under fast
growing conifer tree species may be sufficient to affect Mg uptake.
Validation of the GLEAMS simulation model for estimating net nitrogen mineralisation and nitrate leaching under cropping in Canterbury, New Zealand
Authors: Webb T. H. , Lilburne L. R. , Francis G. S.
Published: September 2002

Simulation models require testing and calibration prior to their application
to regions beyond those involved in their development. This paper reports on
the calibration and testing of the groundwater loading effects of agricultural
management systems (GLEAMS) model for the simulation of nitrate leaching under
cropping in Canterbury. The GLEAMS model was first calibrated using crop and
nitrogen leaching data collected from 4 consecutive years (1991–94) of
spring-sown cereals following the ploughing of a temporary grass/clover
pasture. Nitrate leaching losses were calculated from a combination of
measured soil-solution nitrate concentration at 0.6 m depth, estimated
drainage, and mineral N from soil cores. These calculated leached-N values
were then used to calibrate the GLEAMS model. Parameters controlling
denitrification and mineralisation rate in the model needed modification to
provide sufficient mineral N for plant growth and nitrate leaching. The
calibrated model was then tested against 3 independent validation data sets
that were collected over 3 years from an adjacent experimental site, under the
same management practices. Predictions from the calibrated GLEAMS model
provided close agreement with measured values of mineralisation and leached N
for the validation data sets. The amount of leached N averaged 43 kg
N/ha.year and varied from 14 to 104 kg N/ha.year. The annual amount of
drainage accounted for 97% of the variance in leached N, but the
period in arable cropping was poorly correlated with leached N.
Root effects on soil carbon and nitrogen cycling in a Pinus radiata D. Don plantation on a coastal sand
Authors: Ross Des J. , Scott Neal A. , Tate Kevin R. , Rodda Natasha J. , Townsend Jackie A.
Published: September 2002

Although the contribution of roots to soil carbon (C) fluxes and biochemical
processes is recognised, it is difficult to quantify. One approach to assess
their importance is the use of trenched plots, in which C inputs to the soil
and respiration by living roots has ceased. We give here an account of C and
nitrogen (N) pools and mineralisation in samples taken 27 months after
trenching in a 26-year-old Pinus radiata D. Don
plantation on a coastal sand (an Aquic Udipsamment); above-ground litter
inputs continued throughout the 27-month period.Moisture contents were higher
in FH material and mineral soil from the trenched than from the control plots.
Trenching had no effect on total organic C and N concentrations, but led to
decreases in extractable C, microbial C and N, and CO2-C production values at some depths in the soil profile. Mineral-N concentrations and gross nitrification rates were, in contrast, initially
higher in the trenched-plot samples, but were similar in both treatments after
incubation of the samples at 25°C for 57 days. Mineral-N
concentrations were also higher in the trenched than control mineral soil
after in situ incubation.
On an area basis (to 20 cm depth of mineral soil), inputs from roots were
estimated to account for about 40% of the extractable C pool,
28% of microbial C, 26% of microbial N, and
23% of heterotrophic CO2-C production
(0–7 days at 25°C) in the control soil.
Overall, our results suggest a tight connection between N cycling rates and
the labile C pools derived from below-ground inputs, with nitrification in
particular increasing as C availability declined as a result of trenching.
Surface reactivity of A horizons towards polar compounds estimated from water adsorption and water content
Authors: Parfitt R. L. , Whitton J. S. , Theng B. K. G.
Published: September 2002

The measurement of the specific surface area of soils may be useful for
ranking soils in their ability to sorb polar compounds such as some pesticides
and pollutants. For A horizons with varied mineralogy, particularly those
containing large amounts of soil organic matter, this is problematic. We have
estimated the surface area of a range of topsoils from water adsorption using
the BET equation. The values obtained were greater than those measured from
the adsorption of para-nitrophenol. There was a good
relationship between the BET water area and the CEC of the samples
(r2 = 0.83). There was
a better relationship between the BET surface area and the water content of
air-dry topsoils (r 2 =
0.98). We suggest that the air-dry water contents of topsoils could be used as
a quick method to rank soils in order of their surface reactivity towards
polar molecules, and this is preferable to more complicated methods.
Symposium report: Aeolian dust —implications for Australian mineral exploration and environmental management
Authors: Greene Richard , Gatehouse Robyn , Scott Keith , Chen X. Y.
Published: September 2002

This paper is the preface to the Aeolian dust - implications for Australian
mineral exploration and environmental management paper.
Changes in the surface charge characteristics of degraded soils in the wet tropics through the addition of beneficiated bentonite
Authors: Noble A. D. , Gillman G. P. , Nath S. , Srivastava R. J.
Published: September 2002

In their pristine state, soils of the wet tropics maintain highly productive
climax rainforests that have an intrinsically tight nutrient cycling capacity.
When these ecosystems are disturbed and placed under agronomic production,
soil organic matter is rapidly lost due to continuous stirring of surface
soils, and consequently, there is a rapid decline in fertility. In this study
a methodology is presented that quantifies the degree of degradation that an
agronomic system has undergone since land conversion. In an effort to reverse
this degradation, a glasshouse study was undertaken to evaluate the effect of
applying beneficiated bentonite clays on the surface charge characteristics of
2 degraded soils and their influence on the growth of sorghum.
The properties of an Oxisol cleared of climax rain forest 53 years previously
and currently under tea production were compared with an adjacent undisturbed
forest. Soil pH declined by approximately 0.6 unit. Organic carbon levels
decreased dramatically under the disturbed site, along with exchangeable basic
cations. The degree of degradation associated with changed land use was
estimated to be 85% for the surface soil horizon.
In an effort to remediate the aforementioned degraded Oxisol and a similarly
degraded light-textured Ultisol currently under sugarcane, varying rates
(0–40 t/ha) of beneficiated (Ca 2+ , Mg
2+ , and K + saturated
in a ratio of 8 : 4 : 1) bentonite were applied. Charge fingerprints were
produced for each treatment prior to and after the growing of a sorghum crop.
The basic cation exchange capacity at soil pH was increased from 1.15 to 3.00
cmol c /kg on a light-textured Ultisol and from 0.8 to 2.00 cmol
c /kg on the Oxisol through the addition of
beneficiated bentonites. This increase in surface charge was found to be
permanent. Concomitant with the improved charge characteristics was a
significant and sustained increase in forage sorghum biomass production with
increasing additions of bentonites on both soil types. The cumulative increase
in yield between the control and 40 t/ha bentonite application was a 7.7-
and 3.1-fold increase for the Ultisol and Oxisol soil types, respectively.
Factors affecting the change in extractable phosphorus following the application of phosphatic fertiliser on pasture soils in southern Victoria
Authors: Burkitt L. L. , Gourley C. J. P. , Sale P. W. G. , Uren N. C. , Hannah M. C.
Published: September 2002

Nine pasture soils from high rainfall zones of southern Victoria were analysed
for a range of chemical and physical properties before receiving a single
application of P fertiliser in the form of triple superphosphate (TSP), single
superphosphate (SSP), or TSP and lime (5 t/ha) at amounts ranging from 0
to 280 kg P/ha. Soils were analysed for bicarbonate-extractable P
concentration, using both the Olsen P and Colwell P methods, 6 and 12 months
after fertiliser application. A strong positive linear relationship existed at
all sites between the amount of P applied and both the Olsen P and Colwell P
concentrations. The slopes of these relationships measured the change in
extractable P concentration (Δ EP) per unit of P applied, whilst the
inverse of the ΔEP value indicated the amount of P fertiliser required
above maintenance to increase the extractable P concentration by 1 mg/kg.
These values ranged from 5 to 15 kg P/ha, depending on soil type. The
ΔEP measured by the Olsen (Δ EP Olsen )
method was closely related to selected soil properties and P sorption
measures, whilst the ΔEPColwell values were also
closely related to selected soil properties and P sorption measures, but only
when one particular site, an acidic sand, with a high organic carbon content
was excluded from the analysis. In general, simple, direct measures of soil P
sorption could allow the estimation of ΔEP values on different soil
types.
The application of P in the form of SSP resulted in a trend for higher
ΔEP values than occurred with TSP. This difference was significant on 3
sites (P < 0.05), but depended on the method of
extraction and the time after fertiliser application. The application of lime
significantly (P < 0.001) increased soil pH
(H2 O and CaCl 2 ) and decreased
the concentration of exchangeable Al, 6 months after treatments were applied,
but generally had little impact on ΔEP values.
Kinematic cell model of macropore flow from intermittent irrigation pulses
Authors: Bidwell V. J. , Thorpe H. R.
Published: September 2002

Significant fluctuations in soil water flux were observed in the drainage
hydrographs from lysimeters (1220 mm diam., 900 mm deep) of undisturbed field
soil, recorded at 5-min intervals, in response to intermittent 1-min pulses of
irrigation water (3.4 or 6.8 mm) at irregular time intervals (4–17 min).
The hypothetical process for this phenomenon was flow through soil macropores,
in association with non-linear sorption into soil micropores. The kinematic
wave approach to analysing macropore flow was modelled as a series of
bi-continuum cells, which can be expressed as a set of non-linear ordinary
differential equations. This non-linear state-space description enables the
use of MATLAB software for convenient coding of the model and numerical
integration of the model response to transient water flux input. Model
simulation of drainage response to the irrigation pulse sequences showed good
prediction of the wetting and draining fronts of the hydrograph but gave only
indicative prediction of the magnitudes and wavelengths of the flow
fluctuations. The model demonstrates the sensitivity of macropore flow to
variations in the intervals between irrigation pulses, and supports previous
evidence of fluctuations in macropore flow even for single water flux input
pulses under laboratory conditions.
Field prediction of sodicity in dryland agriculture in Central Queensland, Australia
Authors: Irvine S. A. , Reid D. J.
Published: September 2002

Field classification of Vertosols and Sodosols in Australia involves the
calculation of an exchangeable sodium percentage (ESP) of the subsoil to
estimate sodicity. ESP has historically been determined by laboratory
measurement of the cation exchange capacity (CEC) and exchangeable sodium.
This often leads to a delay in field classification and mapping and missed
extension opportunities with landholders. Recently, ion-specific electrode
field meters have been developed that allow the determination of the sodium
ion concentration within a soil solution. If field tests and/or
calculation can estimate clay percentage and sodium concentration, there is
potential for rapid field assessment of ESP. The field meter accurately
predicted exchangeable sodium (R2
= 0.83). In addition CEC was related to clay percentage
(R2 = 0.79). The estimated
ESP calculated by the field tests compared favourably with the actual ESP
measurement (R2 = 0.85).
Routine measurement of the soil water potential gradient near saturation using a pair of tube tensiometers
Authors: Hutchinson P. A. , Bond W. J.
Published: September 2002

We describe a new tensiometer for routine measurements of the soil water
potential near saturation. The device is called the
tube tensiometer because it is a long, open-topped,
vertical tube (>1 m long) that is filled with porous material. The tube
tensiometer has advantages over other known tensiometers as it does not
require maintenance when the sensing tip dries beyond its air entry pressure
and it is capable of being completely buried beyond the cultivation zone so
that it does not foul tillage and harvesting equipment. The disadvantage of
the tube tensiometer is that it only operates in the range of soil water
potentials from –L to 0 cm of water, where
L is the length of the tube tensiometer.
The output from the tube tensiometer was compared with mercury tensiometers in
a 120-day controlled field drainage and evaporation experiment. The regression
between instruments was high (r2
= 0.99) and the accuracy of the tube tensiometer was <0.5 cm of
water.
The soil water potential gradient near saturation can be measured by
installing a pair of vertically separated tube tensiometers. If the soil
hydraulic conductivity is known then the soil water flux near saturation can
be estimated using Darcy's Law. When the installation depth is below the
active rooting zone of a crop then deep drainage can be estimated. This
application of the tube tensiometer was demonstrated by measuring the vertical
soil water potential gradient at a depth of 1 m beneath a wheat field near
Harden, NSW, in response to winter rainfall. The major limitation to the use
of Darcy's Law for the routine monitoring of deep drainage remains the
estimation of the soil hydraulic conductivity. Ongoing work is focussing on
the use of tube tensiometers to provide simultaneous measurements of both
hydraulic gradient and hydraulic conductivity.
Application of VARLEACH and LEACHM models to experimental data on leaching of a non-reactive tracer and three sulfonylurea herbicides
Authors: Sarmah Ajit K. , Kookana Rai S. , Alston A. M.
Published: September 2002

A chromatographic model (VARLEACH) and a process-based model (LEACHM) were
evaluated under low and high water input regimes (‘rainfall’ and
‘rainfall + irrigation’, respectively) using experimental
data for a non-reactive tracer (KBr), and 3 sulfonylurea herbicides:
triasulfuron, metsulfuron-methyl, and chlorsulfuron. Both qualitative and
quantitative comparisons of predicted and measured water contents revealed
that both models performed well under ‘rainfall’, but prediction
was less satisfactory under the treatment of ‘rainfall +
irrigation’. Both models failed to simulate the bimodal distribution of
Br - and the herbicides observed under ‘rainfall
+ irrigation’ treatment. Distribution of Br
- and the 3 herbicides in the profile was over- or
under-estimated at certain depths and times, probably due to the limitations
inherent to the models (e.g. inability to deal with the macropore flow), and
to simplifications associated with some input data. Simulations for a dry (1
decile), median (5 decile), and wet year (9 decile) with LEACHM and VARLEACH
models using long-term weather data for the site showed that leaching and
persistence of the herbicides are highly dependent on the amount of rainfall
the site receives. The results indicate that the risk of injury to
herbicide-sensitive crops in the following year of application of herbicides
is likely to be greater when the herbicides are applied in a drier rather than
a wetter year.
Effects of rundown in soil hydraulic condition on crop productivity in south-eastern Queensland - a simulation study
Authors: Connolly R. D. , Freebairn D. M. , Bell M. J. , Thomas G.
Published: September 2002

Declining soil organic matter levels because of cropping have been shown to
reduce crop growth and yield, but the effects of changing infiltration and
soil hydraulic properties on crop productivity have not been widely evaluated.
Cropping systems in south-eastern Queensland have, in the past, involved
intense tillage, trafficking with heavy machinery, and changed organic matter
cycling, affecting soil aggregation, permeability, water-holding
characteristics, and organic matter. The aim of this paper is to determine how
important infiltration and soil hydraulic condition has been to the water
balance, crop growth, and yield in the past, and may be in the future if
management is not changed. Change in physical and chemical condition of the 5
most commonly cropped soils in south-east Queensland (Sodosols, Vertosols with
≤55% clay, Vertosols with >55% clay, Red Ferrosols and Red
Chromosols/Kandosols) was measured over 0–70 years of cropping and
estimated up to 200 years. The APSIM model was used to predict effects of
changing soil condition in a rain-fed, fertilised, wheat-summer fallow
cropping system with intense tillage. Decline in infiltration, restricted
internal redistribution of water, and increased evaporation reduced water
supply to the crop, causing simulated yield to decline by 29, 38, 25, 17, and
13% for the 5 soils, respectively, after 50 years of cropping. Gross
margin declined at a faster rate, falling by 36, 50, 40, 20, and 21%,
respectively after 50 years because of increasing fertiliser requirement to
compensate for declining soil fertility. Crop productivity on most soils
continued to steadily decline as period of cropping increased to 200 years. To
arrest or reverse this downward trend, it is likely that substantial changes
to current cropping systems will be needed, including reducing tillage and
trafficking, and improving organic matter levels.
Retention and plant availability of chromium in soils as affected by lime and organic matter amendments
Authors: Bolan N. S. , Thiagarajan S.
Published: September 2002

Chromium is used as Cr(III) in the tannery industry and as Cr(VI) in the
timber treatment industry. In this experiment, the effect of 2 liming
materials [fluidised bed boiler ash (FBA) and lime] and an organic
amendment (Pinus radiata bark) on the retention of Cr by
2 soils (Egmont and Tokomaru) was examined using both ‘batch’ and
‘column’ experiments. The effect of these amendments on the uptake
of Cr from the Egmont soil, treated with various levels of Cr (0–3200 mg
Cr/kg soil), was examined using sunflower
(Helianthus annuus) plants. The transformation of Cr was
examined by fractionation of Cr in soils.
Addition of FBA and lime increased the retention of Cr(III), but had the
opposite effect on the retention of Cr(VI). Addition of bark did not affect
the retention of Cr(III), but it increased the retention of Cr(VI). Increasing
additions of Cr increased Cr concentration in plants, resulting in decreased
plant growth. The liming materials were found to be effective in reducing the
phytotoxicity of Cr(III) and the Pinus radiata bark was
effective for Cr(VI). In both Cr(III)- and Cr(VI)-contaminated soils, the
concentrations of Cr were higher in the organic-bound, oxide-bound, and
residual fractions than in the soluble and the exchangeable fractions. The
concentrations of Cr in the soluble and the exchangeable fractions were higher
in the Cr(VI)-contaminated than the Cr(III)-contaminated soil. Addition of the
liming materials decreased the concentration of the soluble Cr(III) and bark
decreased soluble Cr(VI) in soil. There was evidence for the reduction of
Cr(VI) to Cr(III) in the bark-treated soils.
Effect of application of bauxite residue (red mud) to very sandy soils on subterranean clover yield and P response
Authors: Summers R. N. , Bolland M. D. A. , Clarke M. F.
Published: September 2002

Bauxite residue (red mud) is the byproduct from treatment of crushed bauxite
with caustic soda to produce alumina. When dried the residue is alkaline and
has a high capacity to retain phosphorus (P). The residue is added to pastures
on acidic sandy soils to increase the capacity of the soils to retain P so as
to reduce leaching of P into waterways and so reduce eutrophication of the
waterways.
This paper examines how red mud influences the effectiveness of P from single
superphosphate for producing subterranean clover
(Trifolium subterraneum) dry herbage, in the year of
application and in the years after application (residual value). Red mud was
applied at 0, 2, 5, 10, 20, and 40 t/ha and the P was applied at 0, 5, 10,
20, 40, 80, and 160 kg P/ha.
In the year of application and the year after application of red mud, dry
matter yields were doubled on the soil treated with 20 t/ha of red mud
compared with the untreated control. Improvements in production were initially
greater in the red mud treatments than in the lime treatment (2 t
lime/ha).
Red mud increased the maximum yield plateau for P applied in current and
previous years. When P was applied to freshly applied red mud, more P needed
to be applied to produce the same yield as the amount of red mud applied
increased. Red mud increased soil pH, and the increases in yield are
attributed to removing low soil pH as a constraint to pasture production. This
initial need for higher amounts of fertiliser P when increasing amounts of red
mud were applied may be due to increased P sorption caused by increased
precipitation of applied P when the fertiliser was in close contact with the
freshly alkaline red mud.
When P was freshly applied to red mud that had been applied to the soil 12
months ago, yield response and P content increased. This was attributed to the
reduction in sorption of P due to red mud being neutralised by the soil and
because sorption of P already present in the soil reduced the capacity of the
red mud to sorb freshly applied fertiliser P. Residues of P in the soil and pH
were also increased with application of red mud.
In the years after application of red mud and lime, relative to P applied to
nil red mud and nil lime treatment, the effectiveness of fertiliser P applied
to the red mud and lime treatments increased. This was so as determined using
plant yield, P concentration in plant tissue, and soil P test.
Fingerprinting windblown dust in south-eastern Australian soils by uranium-lead dating of detrital zircon
Authors: Gatehouse Robyn D. , Williams I. S. , Pillans B. J.
Published: September 2002

The U-Pb ages of fine-grained zircon separated from 2 dust-dominated soils in
the eastern highlands of south-eastern Australia and measured by ion
microprobe (SHRIMP) revealed a characteristic age ‘fingerprint’
from which the source of the dust has been determined and by which it will be
possible to assess the contribution of dust to other soil profiles. The 2
soils are dominated by zircon 400–600 and 1000–1200 Ma old,
derived from Palaeozoic granites and sediments of the Lachlan Fold Belt, but
also contain significant components 100–300 Ma old, characteristic of
igneous rocks in the New England Fold Belt in northern New South Wales and
Queensland. This pattern closely matches that of sediments of the
Murray-Darling Basin, especially the Mallee dunefield, suggesting that
weathering of rocks in the eastern highlands has contributed large quantities
of sediment to the arid and semi-arid inland basins via internally draining
rivers of the present and past Murray–Darling River systems, where it
has formed a major source of dust subsequently blown eastwards and deposited
in the highland soils of eastern Australia.
Effects of sodium-contaminated wastewater on soil permeability of two New Zealand soils
Authors: Menneer J. C. , McLay C. D. A. , Lee R.
Published: September 2002

There is increasing anecdotal evidence from some land treatment sites in New
Zealand that irrigating sodium-contaminated wastewaters onto soils may be
causing soil structural problems and reduced permeability. In this study, the
effect of irrigating such waste (derived from agricultural industries) on soil
physical and chemical properties was investigated in an Allophanic Soil (Te
Puninga silt loam) and a Gley Soil (Waitoa silt loam). Wastewater irrigation
at the sites investigated had taken place for the previous 5 years, with
sodium adsorption ratios (SAR) of the wastewater varying between 17 and 51
(mmol/L)0.5 . Increases in exchangeable sodium
percentage (ESP) were recorded to 300 mm depth in both soils. At the soil
surface (0–20 mm), ESP had increased to 31%, compared with
0.4% at control sites.
In laboratory studies using soil from the 0–20 mm layer in non-irrigated
sites, leaching distilled water through repacked columns of the soil
pretreated with various SAR solutions caused saturated hydraulic conductivity
(K sat) to decrease below
100% at SAR greater than 3.5 and 8.5 for the Waitoa silt loam and Te
Puninga silt loam, respectively. The decreases in K
sat coincided with an increase in dissolved organic
carbon (DOC) in collected leachate samples, and no dispersed clay was observed
in the leachate. The laboratory studies would predict that effects of past
irrigation of industrial wastewater at the study site would be measurable in
the field due to the large ESPs that were recorded.
Saturated and unsaturated hydraulic conductivity measurements carried out at
irrigated sites in the field showed no evidence of reduced conductivity in the
surface soil until a pressure head of –120 mm was applied, the decrease
being greater for the Te Puninga soil than the Waitoa. These results, along
with the laboratory studies, suggest that whereas there may have been some
structural deterioration in the soil matrix as a result of irrigation with the
wastewater, macropore flow at higher moisture contents in the field was
sufficient to overcome any adverse effects. It is suggested that laboratory
studies using repacked soil may have limited use in predicting effects of
Na-contaminated wastewater on soil hydraulic properties in structured soils.
The results also further support suggestions that organic matter dissolution
in Na-affected soils may affect soil physical properties.
Land suitability assessment in the Namoi Valley of Australia, using a continuous model
Authors: Triantafilis J. , Ward W. T. , McBratney A. B.
Published: September 2002

In an agricultural context, land evaluation is assessment for a specified kind
of land utilisation. The final result of agricultural evaluation is a map,
which partitions the landscapes into suitable and unsuitable areas for a
particular land-use of interest. However, this approach may not represent the
continuity of land. Land suitability could be better expressed by a fuzzy
approach. In this paper a fuzzy methodology is used to evaluate land
suitability in the Edgeroi district for various crops including barley,
dryland cotton, oats, pasture, soybean, sorghum, sunflower, and wheat. This is
achieved using a membership function to derive a land-suitability membership
score ranging from non-suitable (i.e. 0) to suitable (i.e. 1). We express this
as continuous land suitability maps using punctual kriging. An expression for
overall land suitability (i.e. its versatility) and its capacity with respect
to suitability to particular rotations is introduced to highlight the most
productive units of soil.
Cotton root growth in a compacted Vertisol (Grey Vertosol). I. Prediction using strength measurements and 'limiting water ranges'
Authors: McKenzie D. C. , McBratney A. B.
Published: September 2002

The shear strength of a Vertisol under a broad range of compaction conditions
has been related to ‘non-limiting water range’ (NLWR),
‘partially limiting water range’ (PLWR), and ‘least-limiting
water range’ (LLWR) estimates for the growth of cotton roots. These
factors indicate the soil water content range that land managers should aim to
maintain so that root growth limitations caused by excessive hardness and poor
aeration are minimised. The proportion of macropores available for root
extension as the bulk soil becomes too anaerobic and/or hard for their
growth has been quantified via a re-assessment of published data that relate
oxygen flux density to air-filled porosity. A shear vane was shown to be
better than a penetrometer for distinguishing compacted and non-compacted soil
under a broad range of soil water contents on a Vertisol used for irrigated
cotton production. Published critical limits for cotton root growth based on
penetrometer data are of limited value. Nevertheless, these data have been
converted for use with a shear vane. The NLWR and PLWR estimates have also
been related to the SOILpak score, core bulk density, a clod shrinkage
parameter, and a SOLICON image analysis factor.
Nitrate accumulation under cropping in the Ferrosols of Far North Queensland wet tropics
Authors: Rasiah V. , Armour J. D.
Published: September 2002

Recent research on the fate of applied fertiliser N in the Ferrosols of the
wet tropics of Far North Queensland (FNQ) has shown that the nitrate leaching
below the crop root-zone is a major pathway of N loss from paddocks.
Information on the fate of this nitrate is essential to develop best N
fertiliser management practices and for the long-term sustainability of land
and water resources. Because of the ability of Ferrosols to adsorb anions in
the soil matrix, it was speculated that the leached nitrate may be
accumulating at depth in the Ferrosol profiles. The objectives of this study
were to (i) verify whether the leached nitrate has been
accumulating in the Ferrosols under the major cropping systems in the
Johnstone River Catchment (JRC) of FNQ, and (ii) provide
preliminary estimates for nitrate retention capacity of the Ferrosols. Soil
cores to a depth of 10 m were taken from under sugarcane
(Saccharum officinarum-S), banana
(Musa (AAA group, Cavendish subgroup) cv. Williams),
dairy pasture, and rainforest in JRC during August 1995. The cores were
segmented at 0.5-m depth increments and soil samples were analysed for
nitrate- and ammonium-N, cation- (CEC) and anion- (AEC) exchange capacities,
pH, Ca2+ , Mg 2+ , K
+ , Na + , and Cl
– . Nitrate-N concentration under sugarcane was as
high as 33 mg/kg, compared with 6.9 mg/kg for banana, 0.3 mg/kg
under rainforest, and that under pasture was below detection limit. Nitrate-N
load in the top 10 m of the profiles under sugarcane ranged from 345 to 1875
kg nitrate-N/ha compared with 145 kg/ ha for banana, and 21 kg/ha
under rainforest. Most of the nitrate accumulation was found between 2 and 8
m, i.e. well below the crop root-zone. From 7% to 70% of the
nitrate that leached below crop root-zone was retained at depths >1 m. In
general, Cl – and total cation (TC = sum of
Ca2+ , Mg 2+ , K
+ , and Na + )
concentrations in the profiles under cropping were higher than those under
rainforest, and the pH under sugarcane was more acidic. Simple correlation
analysis indicated associations existed between the accumulated nitrate and Cl
– , pH, AEC, or TC. The estimated nitrate holding
capacity of the Ferrosols ranged from 17 to 32 t N/ha. The results show
that large quantities of the nitrate that leached below crop root-zone have
accumulated at depth under long-term sugarcane and banana cropping in the
Ferrosols of FNQ.
Measurement of unsaturated hydraulic conductivity using tension and drip infiltrometers
Authors: McKenzie N. J. , Cresswell H. P. , Rath H. , Jacquier D.
Published: September 2002

We investigated differences between constant flux and constant potential
methods for determining unsaturated hydraulic conductivity in the laboratory.
A cheap and robust method was required. The constant flux drip infiltrometer
has been used with large intact cores on a wide range of Australian soils.
However, the method can be simplified by replacing the drip infiltrometer with
a constant potential tension infiltrometer (disc permeameter).
We conducted a series of measurements using 9 soil cores to determine whether
the measured hydraulic conductivity differed with each method at matric
potentials of –10, –20, or –50 mm. Hysteresis effects were
also examined because tension infiltrometer measurements are usually made on
the adsorption curve of the hydraulic conductivity and matric potential
[K(Ψ)] relationship. Drip infiltrometer measurements are often
made on the desorption curve. The reproducibility of measurements on a single
core was also examined.
A large decline in K(Ψ ) was observed on some cores with repeated
measurements and this effect was larger than differences between the methods.
In the absence of evidence of slaking or dispersion, the suspected cause of
the decline in K(Ψ) was clogging of pores from accumulation of microbial
biomass and their by-products. The results support the view that K(Ψ) in
some soils is a dynamic property. There were consistent differences between
the constant flux and constant potential methods on those soil cores not
exhibiting a large decline in K(Ψ) (the others were omitted from the
method comparison). The tension infiltrometer method indicated greater
hydraulic conductivity in soils with well-developed macrostructure when matric
potential was greater than –50 mm. Hysteresis effects were significant
with both methods and measurements made on desorption and adsorption curves
are not considered comparable. Overall, we concluded that the tension
infiltrometer method was more suited than the drip method for routine
processing of large numbers of samples at low cost.
The orthophosphate content of bicarbonate soil extracts
Authors: Coventry Joanne L. , Halliwell David J. , Nash David M.
Published: September 2002

The Olsen P and Colwell P bicarbonate extraction procedures are empirically
derived tests that provide an estimate of the soil P that is available for
plant uptake. This paper examines each procedure using high performance liquid
chromatography with flow injection analysis detection (HPLC-FIA) to
specifically measure orthophosphate in bicarbonate extracts. Extract solutions
from 3 soils of contrasting plant-available soil P contents were analysed for
orthophosphate, total filtered (<15—45 µm) P (TFP), and
either Olsen P or Colwell P. The amounts of P extracted by the Olsen procedure
were not statistically different from orthophosphate (HPLC-FIA)
(P > 0.05), suggesting the Olsen P test was a good
measure of orthophosphate, the most immediately plant-available form of P.
However, the average amount of P extracted by the Colwell procedure was
14% higher (P < 0.01) than the corresponding
average orthophosphate concentration, presumably due to the presence of labile
organic/condensed P, colloidal associated orthophosphate, or high
molecular weight reactive P. These results suggest that there is a pool of
non-orthophosphate P present in the molybdate reactive Colwell P extract that
is potentially plant available. Future work should focus on specific
identification of P compounds extracted from soils and soil solutions to
examine their role as a source of P to plants.
Postfire survival in south Florida slash pine: interacting effects of fire intensity, fire season, vegetation, burn size, and bark beetles
Authors: Menges Eric S. , Deyrup Mark A.
Published: September 2002

We used path analysis to examine postfire survival of south Florida slash pine
(Pinus elliottii var. densa) at
Archbold Biological Station in south-central Florida. We considered the
interacting factors of bark beetle infestation, fire intensity (estimated by
bark char, percentage of canopy green, and other measures), season of burn,
burn size, and vegetation structure and composition. Trees were sampled in 24
burned areas for 3 years after each fire. Fires on recently-burned sites
(5–19 years since previous fire) killed fewer trees (44%
mortality) than fires on sites > 25 years postfire (71%). For
long-unburned sites, we used multiple regression to examine 35 variables and
form a path model linking nine variables at four levels. Pine survival was
most affected by season of burn; fall burns decreased survival indirectly
through increases in fire intensity. Higher mortality was associated with
greater char height, larger area burned, more intense attacks by the beetle
Platypus, occurrence of hickory scrub or flatwoods
vegetation, and complete needle consumption. The final path model explained
over 90% of the variation in pine survival. It suggested that beetle
effects reflect fire intensity, and detailed many complex interactions. Both
preburn and fire intensity data were needed to explain a high amount of
variance. Analyses of survival within burns produced similar results, but
added some patterns due to vegetation differences within burns and higher
survival for larger trees. Fire-induced south Florida slash pine mortality did
not spread to trees growing in adjacent, unburned areas. Fire intensity may
influence pine densities over the upland landscape in all but the most xeric
and hydric sites. Fire management to maximize pine survival is feasible, but
management for landscape heterogeneity will tolerate variation in fire
intensity and pine survival.
Theoretical fire-interval distributions
Authors: McCarthy Michael A. , Gill A. Malcolm , Bradstock Ross A.
Published: September 2002

Models for fire interval distributions in ecological communities are proposed,
based on an understanding of the processes that influence the probability of
fire, especially changes to the amount and condition of the fuel. The models
represent changes in the probability of fire as a function of time since last
fire. Despite considerable differences in the probability distributions of
fire intervals, the models generate very similar age distributions when the
mean fire interval is the same. Therefore, fitting the theoretical
distributions to observed landscape age structure is unlikely to allow
discrimination between different models. Previously, the most commonly used
models of fire intervals have been based on the Weibull probability
distribution. We believe that this is unnecessarily restrictive, and a broader
range of models should be considered. The models may be based on an a priori
understanding of the ecosystem being studied. They should assist
interpretation of observed or inferred fire interval distributions.
Fire shelter performance in simulated wildfires: an exploratory study
Authors: Butler Bret W. , Putnam Ted
Published: September 2002

Fire shelters are required equipment for most wildland firefighters in the
United States. In this study we report flame emissive power and temperatures
inside and outside fire shelters placed in one prescribed fire, five
experimental field fires, and one laboratory fire. Energy levels radiated by
flames varied from 70 to 150 kW m–2 and lasted
less than 10 min. Maximum fire shelter internal air temperatures reached
250˚C and occurred during the test with the maximum external air
temperatures (1000˚C). Air temperatures inside the fire shelters did not
show a strong dependence on flame radiant power, rather they correlated most
strongly with external air temperature. We compare measurements from these
tests with results reported by others. The data clearly indicate (1) the
capability of the fire shelter to protect the occupant from radiant heating;
(2) the susceptibility of the current design to convective heating; and (3)
the significant decrease in burn injury when fire shelters are used.
Surface burning in a mature stand of Pinus resinosa and Pinus strobus in Michigan: effects on understory vegetation
Authors: Neumann David D. , Dickmann Donald I.
Published: September 2002

Beginning in 1991, periodic surface fires (frontal fire intensities <200 kW
m–1) were introduced into a mixed red pine
(Pinus resinosa Ait.) and white pine
(P. strobus L.) plantation (dbh 16–60 cm).
Replicated plots of 0.4–0.5 ha were either burned three times at
biennial intervals (early May of 1991, 1993, and 1995), burned once (early May
1991), or not burned. Measurements were conducted during the 1994 and 1995
growing seasons. The pine overstory was largely unaffected by the fires. The
understory on unburned plots contained 16 111 large seedlings (>1 m, ≤
1.9 cm dbh) and 3944 saplings (2.0–5.9 cm dbh) per ha, consisting of 23
woody angiosperm taxa. Plots burned once contained 60% of the large
seedlings, 7% of the saplings, and 6 fewer taxa than unburned plots. No
large seedlings and few saplings were found in plots burned biennially. Cover
of low (<1 m) woody and herbaceous vegetation in plots burned once or three
times was twice that of unburned plots, even in the growing season immediately
following the May 1995 re-burn. Recovery of low vegetative cover in the
re-burned plots was rapid, exceeding that in once-burned or unburned plots by
late summer following the burn. Species richness of low vegetation was
20–25% higher in burned than unburned plots, except in the year
immediately following reburning. Taxa dominating this site following burning
were Sassafras albidum (Nutt.) Nees,
Rubus spp., Phytolacca americana
L., and Dryopteris spinulosa (O.F. MÜll.) Watt.
Restoration of low-intensity surface fires to ecosystems dominated by mature
red pine or white pine is feasible, but major changes in understory structure
and composition will occur.
A qualitative study of collaborative information seeking
Authors: Prekop Paul
Published: September 2002

Much of the existing information seeking literature only considers information seeking when performed by an individual information seeker. This paper describes a study that explicitly considers information seeking from a collaborative perspective. The study used a grounded theory approach of a complex, real world, example of collaborative information seeking activity, drawn from the military domain.
Using Dewey decimal classification scheme (DDC) for building taxonomies for knowledge organisation
Authors: Saeed Hamid , Sattar Chaudhry Abdus
Published: September 2002

Terms drawn from DDC indexes and IEEE Web Thesaurus were merged with DDC hierarchies to build a taxonomy in the domain of computer science. When displayed as a directory structure using a shareware tool MyInfo, the resultant taxonomy appeared to be a promising tool for categorisation that can facilitate browsing of information resources in an electronic environment.
Criteria for the success of automated library systems: Iranian experience (application and test of the related scale)
Authors: Hossein Farajpahlou A.
Published: September 2002

Refers to a 1999 Australian survey which examined a 26 item scale developed regarding three major automated library systems issues, which approved 23 items that represented criteria for the success of automated library systems, and rejection of the remaining three items. The same scale was translated into Farsi in the year 2000 and distributed among 240 library managers and systems librarians in 120 Iranian institutions of higher education. Results of the Iranian survey were acceptance of 24 out of the 26 scale items by university librarians and systems managers, and rejection of two items. The rejected items were not identical in the two studies, and the discrepancies mainly raised by “boundary” issues. However, Australian and Iranian colleagues seem to be identical in their attitudes towards management, technicalities and usage of automated library systems. The scale, so far, has proved to be reliable and valid, at least with 21 of its items.
The comparative attractiveness of international business locations: the role of labor law
Authors: Pull Kerstin
Published: September 2002

At a time of intensifying uncertainty, managerial flexibility to adapt to changes in the economic environment is increasingly important. Different business locations, it is frequently argued, offer this flexibility to differing degrees, labor law being one essential factor in determining the resulting attractiveness of a country as a business location. This paper takes an options perspective in order to grasp the potential effect of labor law on location decisions. The option value of an investment, it is argued, is influenced, among other factors, by labor law provisions. Depending on their preference for a certain set of options, different investors will prefer different labor market settings. The ability of the options perspective to assess the role of labor law for the attractiveness of international business locations is exemplified in a British‐German comparison and confronted with data on the composition of foreign direct investment in the two countries.