bluuebunny/crossref_metadata_2025 huggingface dataset:
Water and bromide movement in a Vertosol under four fallow management systems
Authors: Turpin J. E. , Thompson J. P. , Bridge B. J. , Orange D.
Published: January 2006

Recent work on the Hermitage long-term fallow management found increased rates
of anion movement under zero tillage systems compared with conventional
tillage. Four separate experiments have been used to determine relative rates
of water movement through different fallow management treatments on the
Hermitage long-term fallow management trial and the causes of any differences.
Photography of the aggregation patterns at the depth of tillage (approx. 15
cm) showed that conventional tillage combined with stubble burning has led to
the formation of large massive peds up to 20 cm across below the tillage
layer, whereas zero-tillage with stubble retention has maintained much smaller
aggregates in this zone. Measurements of hydraulic conductivity at 15 cm under
both dry and moist conditions indicated that, when the soil is dry and
cracked, all tillage treatments have similar conductivities, but when the soil
swells and cracks close, zero tillage–stubble retention maintains a
greater volume of large pores and thereby greater conductivity. This effect
was further demonstrated when a bromide tracer solution was applied to a
relatively wet soil by ring infiltrometer, where only 15% of the
solution moved below 15 cm in conventional tillage–stubble burning
compared with 26% and 38% in zero tillage{stubble
retention. In the final experiment, which followed the movement of surface
applied bromide over a 6-month fallow, there were no significant differences
in rates of leaching between management treatments.
A lysimeter study of the impact of cow urine, dairy shed euent, and nitrogen fertiliser on nitrate leaching
Authors: Silva R. G. , Cameron K. C. , Di H. J. , Hendry T.
Published: January 2006

The effect of cow urine, dairy shed effluent (DE), and urea fertiliser on
nitrate leaching was determined using undisturbed soil lysimeters (500 mm
diameter by 700 mm deep) with ryegrass
(Lolium perenne)–white clover
(Trifolium repens) pasture. Cow urine was applied to the
lysimeters, at rates of 0 and 1000 kg N/ha in May 1996. Urea and DE were
applied to urine-applied and non-urine-applied lysimeters at rates of 0, 200,
and 400 kg N/ha in 4 split equal applications in May, August, and November
1996 and February 1997. Natural rainfall was supplemented with simulated
rainfall in winter and spring (May–October) to achieve the 75th
percentile of winter–spring rainfall records in the region. Flood
irrigation was applied 6 times during summer–autumn
(November–April) at 100 mm per application, which is a typical practice
used by dairy farmers in the region. Drainage water was collected and analysed
for nitrate, nitrite, bromide (added tracer), and ammonium.
Over the first year of the experiment (May 1996–April 1997), 12%
of the urine-N applied was lost through leaching, mainly in nitrate form. When
urine (1000 kg N/ha) was applied in combination with DE (200 kg N/ha)
and urea (200 kg N/ha), the mineral N leaching loss increased to
14% of the total N applied. The annual average nitrate concentrations
in the drainage from the lysimeters that received urine alone, or
urine+DE and/or urea, were 33–57 mg N/L, with a mean peak
concentration of 110 mg N/L. These nitrate concentrations were
significantly higher than in those treatments that did not receive urine
(1–5 mg N/L).
Because, on average, about 25% of the area of a grazed dairy paddock
receives urine per year, the field-scale leaching losses were calculated by
taking into account the dilution effect of drainage water from non-urine patch
areas of the paddock. The calculated annual paddock losses were 33–60 kg
N/ha, and on average the annual paddock nitrate concentrations were
10–17 mg N/L. This demonstrates the importance of accounting for the
dilution of nitrate in the leachate from non-urine patch areas of the paddock.
The annual average concentration from the treatment DE at 400 kg N/ha was
significantly lower than that from the urea treatment at the same rate. This
was probably because of the different chemical forms of N in each material,
and needs to be taken into account when developing regional rules for land
application of urea and effluents.
Formation, ecology, and geography of Cryosols of an ice-free oasis in Coastal East Antarctica near Casey Station (Wilkes Land)
Authors: Beyer Lothar , Bölter Manfred
Published: January 2006

New soil studies in the cold suggest that in the terrestrial ecosystems of the
coastal regions of the antarctic continent, soil formation and chemical
weathering occur to a greater extent than previously expected. This paper
summarises the pedogenic results of an Australian-funded expedition to Casey
Station and presents a soil formation sequence on a small-scale database. The
accumulation of soil organic matter and podzolisation are important
soil-forming processes up to the antarctic polar desert. This study has
revealed a high variability in soil geography and soil properties at both a
profile and landscape level. However, previous results indicate a correlation
between soil cover and vegetation pattern. Nutrient supply in soil is affected
by high contents and availability of nitrogen, phosphate, potassium, and
magnesium due to the presence of seabirds.
Prediction of cadmium concentrations in potato tubers (Solanum tuberosum L.) by pre-plant soil and irrigation water analyses
Authors: McLaughlin M. J. , Maier N. A. , L.Correll R. , Smart M. K. , Sparrow L. A. , McKay A.
Published: January 2006

Potato tubers can accumulate high concentrations of cadmium (Cd) in edible
portions, so that techniques to determine high risk Cd environments are
required by growers. The use of combined soil and irrigation water analyses
prior to crop planting was investigated as a means to predict risks of Cd
accumulation in tubers. Soils and irrigation waters were analysed at 134 sites
in the major potato production areas in Western Australia, South Australia,
Tasmania, Victoria, and New South Wales. Irrigation waters were analysed for
electrical conductivity (EC), major cations, and anions. Cadmium was extracted
from soil using aqua regia (1 : 3 HNO3: HCl), EDTA
(ethylenediamine-N,N,N′,N′-tetraacetate), DTPA
(diethylene-triamine-pentaacetate), 0·01 M CaCl2,
0·01 M Ca(NO3)2, 0·1 M
CaCl2, and 1·0 M
NH4NO3. The preferred test
procedure was validated in a subsequent sampling and analysis program at 39
sites.
Irrigation water quality (EC or Cl concentration), measured prior to planting,
explained the greatest variation in tuber Cd concentrations. Of the soil test
procedures, only Cd extracted by 0·01 M CaCl2
significantly improved the predictive capacity of water EC. These 2 measures
explained >55% of the variance in tuber Cd concentrations. The data
set were transformed to generate a probability curve for exceeding Cd
concentrations of either 0·05 or 0·1 mg/kg fresh weight, the
latter being the current maximum permitted concentration (MPC) in Australia
for potato tubers.
The probability of producing potato tubers exceeding 0·05 and
0·1 mg/kg fresh weight was >50% once irrigation water EC
increased above 1·4 and 3·0 dS/m, respectively. Using the
relationships developed, growers should be able to quantify Cd risks by a
simple test of irrigation water EC prior to planting and, if further precision
is needed, also determine CaCl2-extractable Cd in soil.
Use of on-ground gamma-ray spectrometry to measure plant-available potassium and other topsoil attributes
Authors: Wong M. T. F. , Harper R. J.
Published: January 2006

The incidence of potassium (K) deficiency is increasing in crops, pastures,
and forestry in south-western Australia. Although soil K can be measured using
soil sampling and analysis, γ-ray spectrometry offers a potentially
cheaper and spatially more precise alternative. This could be particularly
useful in precision agriculture, where inputs are applied according to need
rather than by general prescription.
In a study of topsoils near Jerramungup, Western Australia, strong
relationships (r2 =
0·9) were found between on-ground counts of γ-rays derived from
40K (γ-K) and both total K and plant-available K.
The success of γ-ray spectrometry in predicting available K relied on a
strong relationship (r2 =
0·9) between total K and available K which may not hold in all areas.
Although the relationship between γ-K and available K held over the range
of 36–1012 mg/kg, crop response to K fertilisers is only expected
when the available K content is <100 mg/kg. Estimates of available K
from γ-K were unreliable at this lower end of the regression curve.
Separate analysis with a subset of the data with available K <100 mg/kg
showed a poor relationship between γ-K and available K
(r2 = 0·05; d.f.
11). The usefulness of γ-ray spectrometry may therefore be restricted to
defining areas where response to fertiliser K may occur, and where further
soil sampling and analysis are required to predict the fertiliser requirement.
Strong relationships (r2 =
0·9) were also found between γ-K and a range of other soil
attributes, including clay, silt, and organic carbon content. These
relationships depended on the locally strong relationship between total K and
these soil attributes. Since such relationships do not hold everywhere, the
utility of γ-ray spectrometry will likewise be limited. Site-specific
calibrations are required if γ-ray spectrometry is to be used for soil
property mapping.
Urban soil contamination in Bangkok: concentrations and patterns of polychlorinated biphenyls (PCBs) in topsoils
Authors: Wilcke Wolfgang , Müller Silke , Kanchanakool Nualsri , Niamskul Chalinee , Zech Wolfgang
Published: January 2006

Little is known about the polychlorinated biphenyl (PCB) pollution of tropical
environments, although part of the contribution to global PCB contamination
originates in the tropics. The objective of this study was to compare PCB
concentrations and patterns in urban soils of Bangkok with data from the
temperate zone to detect indications for possible differences in sources and
fate of PCBs.
The sum of congeners 1, 8, 20, 28, 52, 101, 118, 138, 153, 180, 206, and 209
(=Σ12PCBs) ranged from 0·19 to 11·4
µg/kg, which was lower than values reported for urban soils in the
temperate zone. On average, the hexa-chlorinated PCBs 138 (mean of Σ12
PCBs± s.d., 22·7 ± 8·1%) and 153
(19·9 ± 9·0%) were most abundant. The Bangkok
soils contained higher percentages of lower chlorinated PCBs (≤ 4 Cl) and
correspondingly lower percentages of higher chlorinated PCBs (>4 Cl) than
soils in 3 temperate cities. The differences may be explained by different
sources, a lower age of contamination and therefore lower volatilisation, or
anaerobic dechlorination during water-stagnant periods.
The comparison of the PCB profiles in Bangkok soils with those of widely used
commercial PCB mixtures indicated that the major PCB sources of Bangkok soils
were the highly chlorinated Clophen A60, Aroclor 1260, or similar mixtures
dominated by hexa-chlorinated PCBs.
Cadmium phytoavailability in some New Zealand soils
Authors: Gray C. W. , McLaren R. G. , Roberts A. H. C. , Condron L. M.
Published: January 2006

The suitability of 8 common soil extractants to predict plant uptake of
cadmium (Cd) from 10 New Zealand soils at low Cd concentrations was
investigated in a glasshouse experiment. In addition, a study of Cd uptake by
several vegetable, cereal, and pasture species in relation to different soil
types was undertaken. The concentrations of Cd extracted from soils varied
with each extractant: 0·05 acid ammonium acetate-EDTA (pH 4·65)
extracted the greatest concentration of Cd, whereas 0·01
CaCl2 extracted the least. Results indicate that for all
extractants tested, there were significant relationships between the
concentration of Cd extracted and the concentration of Cd in plant material;
however, the level of significance depended on the plant species and
individual soil extractant. When all plants were considered together, it was
found that 0·05 Ca(NO3)2
was the best predictor of plant Cd concentrations. Total Cd concentration was
found to be the most important soil parameter influencing plant Cd
concentrations. Plant Cd concentrations varied greatly among different plant
species. The greatest uptake was found in lettuce and to a lesser extent
carrot tops, and least in ryegrass, clover, and barley. All plants examined
were within the maximum residue limit (MRL) in New Zealand for the Cd content
of all foodstuffs intended for human consumption (i.e. 1 mg Cd/kg fresh
weight).
Turnover of nitrogen from components of lupin stubble to wheat in sandy soil
Authors: Russell C. A. , Fillery I. R. P.
Published: January 2006

The rate of decomposition of 15N-labelled lupin
(Lupinus angustifolius) stubble and the use of
mineralised 15N by wheat were determined in field
experiments on a deep loamy sand previously cropped to lupin. In one
experiment, leaf, stem, and pod (pod-valve) components were applied separately
to mini-plots that were either left unplanted or subsequently planted to
wheat. In the second experiment, leaf and stem components, each of either low
or high N concentration, were applied separately to mini-plots which were
subsequently planted to wheat. Soil was recovered in layers to a maximum depth
of 1 m and subsequently analysed for 15N in NH + 4
, NO-3 , and total N. The net mineralisation of stubble
15N was estimated from the decrease in soil organic
15N (total 15N – inorganic
15N), and the uptake of 15N by
wheat was measured periodically.
All treatments were characterised by the high retention of lupin stubble
15N in the soil organic matter. Between 9 and 34%
of stem and pod 15N, and 19–49% of leaf
15N, was mineralised within a 10-month period. From
these data the annual net mineralisation of a typical lupin stubble was
estimated at 25–42 kg N/ha, an N benefit similar to that estimated
from agronomic trials.
Wheat uptake of lupin-stubble 15N ranged from 9 to
27%. Of the stubble components, only the leaf contained sufficient
quantities of mineralisable N to be an important source of N for wheat. At
wheat maturity in the first experiment, losses of stubble
15N ranged from 13% (leaf) to 7% (stem).
In the second experiment, losses of 15N were only
observed from the high N treatments (leaf 8%, stem
15·5%).
Stubble component chemistry appeared to affect net mineralisation and plant
uptake differently. Across both experiments, annual net mineralisation best
correlated (R = 0·69) with the N
concentration of the stubble components. Wheat N uptake was strongly
positively correlated with polysaccharide content (R
= 0·89) but negatively correlated with lignin content
(R = – 0·79).
Although large quantities (58 and 98 kg N/ha) of soil-derived inorganic N
were found in the root-zone (–1·0 m) of wheat sown after lupins,
and attributed to the decomposition of lupin root systems and surface residues
prior to the establishment of each experiment, it is concluded that the
short-term decomposition of lupin stubble 15N results in
a modest release of inorganic N. Consequently, the primary value of lupin
stubble in the N economy of lupin : cereal rotations is to replenish the soil
organic N reserve.
Losses of nitrogen from an effluent-irrigated plantation
Authors: Smith C. J. , Bond W. J.
Published: January 2006

Effluent-irrigated tree plantations are becoming a popular alternative to the
direct discharge of sewerage effluent into inland rivers. However, when
irrigated at the water-use rate of the plantation, nitrogen (N) applied in the
effluent often exceeds the demand of the trees both in the early stages of
growth and after canopy closure when much of the N is supplied from the
decomposition of litter. With the ample supply of water and large loadings of
N, conditions are conducive to significant N losses. The principal potential N
loss mechanisms are leaching of nitrate-N to groundwater and biological
denitrification. In 4 separate experiments between winter 1992 and summer
1994, 15N-labelled N (total application of 2 g
N/m2; 30 atom%) was applied to
1-m2 subplots or small plastic (PVC) cylinders. In the
first 2 experiments, using 1-m2 subplots, the
conservative tracer Br was applied as KBr with the 15N
at a total application of 12·8 g
Br-/m2. In Expt 1, the high
recovery of the 15N-labelled N, and the comparable
distribution of 15N and Br- in the
soil profile, implied that there was little loss of N by denitrification, even
though the soil was sufficiently wet for leaching of both tracers. Although
less conclusive, the other experiments also showed a high potential for
leaching and minimal loss of applied 15N-labelled N by
denitrification. The small contribution to N loss of denitrification, despite
conditions being otherwise suitable for it, is attributed to the free-draining
nature of the soil, which meant that aeration was rarely sufficiently limited
to encourage denitrification. Similar results are expected at other effluent
irrigation sites on freely draining soils.
A study of atrazine transport through a soil profile on the Gnangara Mound, Western Australia, using LEACHP and Monte Carlo techniques
Authors: Pollock Daniel , Salama Ramsis , Kookana Rai
Published: January 2006

A preliminary risk assessment of atrazine leaching at a strawberry farm on the
Gnangara Mound, Western Australia, was performed using LEACHP in conjunction
with Monte Carlo techniques. Monte Carlo techniques were also used to
implement a sensitivity analysis of LEACHP to determine influential
parameters. As an extension to the sensitivity analysis, a model comparison
was performed with similar models, in order to quantify differences arising
from the use of different models.
The Monte Carlo risk assessment involved simultaneous variation of
LEACHP's soil parameters and selected chemical parameters to assess the
risk of atrazine leaching past the root-zone at the experimental site. This
Monte Carlo risk assessment predicted that of the 100
mg/m2 of atrazine applied at the experimental site,
the mean cumulative mass per unit area of atrazine to leach below the
root-zone after 263 days was 49 mg/m2, with a
standard deviation of 4.1 and a range from 37 to 62
mg/m2.
The Monte Carlo sensitivity analysis of LEACHP tested selected soil and
chemical parameters, one at a time, to determine the influence of each
parameter on the models predictions of cumulative mass per unit area of
atrazine to leach below the root-zone. The chemical parameters organic carbon
partition coefficient (Koc) and degradation rate
constants were found to be more influential than the soil parameters, with
Koc being the most influential parameter. The most
influential of the soil parameters was organic carbon content, followed by
bulk density.
The model comparison involved 4 separate simulations: LEACHP using
Richards' equation (LEACHP (Richards)), LEACHP using Addiscott's
model of water and solute movement (LEACHP (Addiscott), MACRODB, and GLEAMS.
The results from this exercise showed that LEACHP (Richards) and MACRODB made
similar predictions for the cumulative mass per unit area of atrazine to leach
below the root-zone (49 and 50 mg/m2, respectively),
while GLEAMS and LEACHP (Addiscott) made significantly lower predictions (35
and 38 mg/m2, respectively).
The results from this study indicate there is a significant risk of atrazine
leaching at the experimental site; however, more detailed field measurements
and further modelling would enable more accurate predictions.
Subsoil bulk density and organic carbon stock in relation to land use for a Western Australian Sodosol
Authors: Bruand Ary , Gilkes Robert J.
Published: January 2006

It has been demonstrated that the high bulk densities of clayey subsoils of Sodosols can result from a process involving shrink/swell cycles and the development of ped coatings containing topsoil material. Our objective was to study this process according to land use and to compute the amount of organic carbon introduced into the subsoil as a consequence of ped coating in the subsoil. In an area located east of Katanning, we carried out an intensive soil survey and selected 2 closely adjacent sites with similar soils but differing in their land use: a cultivated soil and a never cultivated soil in an undisturbed strip of land. Pit faces and horizontal planes of the top of the subsoil were studied. The polygonal network corresponding to the cross-section of the prismatic peds was described. The clay content and bulk density of the prisms was determined. The carbon contents of the coatings and of the sandy material rich in organic carbon that corresponded to remnants of native vegetation was measured. Results showed that the coating process has occurred under native vegetation but is more active when the land has been used for agricultural and pastoral activities, as indicated by thicker sandy-clay coatings on the vertical faces of prisms and the higher bulk densities in the subsoil. The mean bulk density was 1.71 g/cm3 at 20-25 cm depth at the undisturbed site and was 1.86 and 1.82 g/cm3 at 20-25 and 25-30 cm depth, respectively, at the cultivated site. The total soil organic carbon stock was estimated to be close to 68.9 and 61.0 Mg/ha at the undisturbed and cultivated sites, respectively. The organic carbon stock in the subsoil was 38.5 and 23.3% of the respective total stocks. One fourth of the carbon stock in the subsoil corresponded to materials rich in organic carbon that originated from roots of native vegetation. The organic carbon stock in the ped coatings was <1% of the total stock at the 2 sites. Finally, our results support the adoption of zero-till agricultural system for the soil studied to restrict subsoil densification.
Effect of contrasting farm management on vegetation and biochemical, chemical, and biological condition of moist steepland soils of the South Island high country, New Zealand
Authors: McIntosh P. D. , Gibson R. S. , Saggar S. , Yeates G. W. , McGimpsey P.
Published: January 2006

A question of economic, social, and land-use importance in the predominantly
steep South Island high country tussock grasslands of New Zealand is whether
these lands can be sustainably farmed by oversowing introduced grasses and
legumes and using fertilisers. To help answer this question, we compared
vegetation and soil chemical, biochemical, and biological properties on Brown
soils (Dystrudepts) on adjacent land areas which have been differently managed
since 1978. One area had never been fertilised or oversown. The other had been
oversown with grasses and clovers and received about 1100 kg/ha of
sulfur-superphosphate between 1979 and 1997.
Oversowing and fertilising reduced the amount of bare ground and transformed
the vegetation to a species composition dominated by the introduced adventives
Anthoxanthum odoratum and
Agrostis capillaris. Fertilising raised soil carbon (C)
and nitrogen (N) content, increased A-horizon thickness, and raised
exchangeable cation values. All of the phosphorus (P) applied to the
fertilised area was accounted for in the top 15 cm of soil, but has
accumulated in the relatively unavailable organic form. Oversowing and
fertilising significantly (P < 0 . 05) increased
microbial biomass C, N, and P relative to values in unfertilised soils. The
microbial biomass C: N and C: P ratios were significantly
(P < 0 . 05) lower in fertilised soils.
Fertilised soils had significantly more (P < 0 .
05) mineralised N than unfertilised soils.
Populations of 5 groups of soil fauna (Scarabaeidae, nematodes, enchytraeids,
rotifers, tardigrades) were higher in fertilised soils. Nematode species
parasitic or pathogenic for clovers were present in greater numbers on
fertilised soils. A combination of fertility decline (in particular, P
immobilisation as organic P) and nematode damage may be the reason for the low
clover cover on fertilised sites, and may explain the widely observed clover
‘flush’ and decline common to oversown high country.
We conclude that there is no simple measure of ‘soil quality’ that
can be used as a sustainability indicator in moist New Zealand high country.
Nor can sustainability be judged purely on biological, biochemical, and
chemical critieria. Although many of the effects associated with oversowing
and fertilising, such as increased organic matter content of A horizons and
increased biological activity, are positive, these effects must be balanced
against the economic risk associated with being committed to a high-input
farming system, the loss of low-producing but resilient native species, and
increase of plant-pathogenic nematodes.
Vegetative filter strips to control sediment movement in forest plantations: validation of a simple model using field data
Authors: Loch R. J. , Espigares T. , Costantini A. , Garthe R. , Bubb K.
Published: January 2006

A field study of sediment movement through vegetative barriers was carried out
to assess the sediment-trapping effectiveness of vegetative barrier types
typically used in forest forest plantation management in south-east
Queensland, Australia, and to develop a simple methodology for predicting
sediment movement through these barriers.
For sites at the centre of Queensland's 110 000 ha
Pinus plantation and 45 000 ha
Araucaria plantation program, small field flumes (plots)
were established on a range of vegetation types and slope gradients, and
sediment-laden flows passed through them. Sediment trapping in the plots was
assessed by comparing paired samples taken from the inlet and outlet of the
plots at pre-determined sampling times. Measurements included total sediment
and equivalent size distributions of sediment particles (the latter
measurements being based on settling velocities).
For plots that did not erode, the degree of sediment trapping, if based on
total sediment only, was quite variable. However, if rates of transport were
considered in terms of the various size fractions, results were very
consistent. A simple conceptual approach equating the vegetated area to a
sedimentation pond allowed deposition to be calculated on the basis of
settling velocity, flow depth, and residence time within the vegetated area.
Estimated transport rates of sediment through the vegetated areas were in
close agreement with measured transport rates, confirming the eciency of this
approach.
The results highlight a number of issues for management of sediment movement
from forest estates.
Physical and chemical characterisation of the agricultural lands of the Soan - Sakesar Valley, Salt Range, Pakistan
Authors: Afzal Shahzad , Younas Mohammad , Hussain Khadim
Published: January 2006

Soil samples (depth, 0–20 cm) from the Soan–Sakesar Valley were
analysed for a variety of parameters: pH, electrical conductivity (ECe),
alkalinity, Na, K, Ca, Mg, Cl, SO4, Li, B, and
NO3 in saturation extracts; organic carbon (C),
NaHCO3-extractable phosphorus (P), and total P in whole
soil; and mineralogical investigations in whole-soil and separated clay
fractions. A Principal Component Analysis was carried out on the correlation
matrix (i.e. on standardised attributes) and soil samples were subdivided into
salinity groups. The mean ECe levels of Groups 1–4 were 1.27, 2.75,
2.07, and 5.67 dS/m, respectively; the corresponding sodium adsorption
ratios were 5.36, 7.9, 15.7, and 29.6 mmol0.5,
respectively. In these soil groups, suitable crops were suggested on the basis
of their salt tolerance and the salinity of the irrigation water. The low
availability of P from phosphatic fertilisers and farmyard manure as a result
of fixation by calcite, which is present in these soils to the extent of
7.8–15.2%, resulted in a lower yield of grain crops (wheat and
maize). On the other hand, higher application rate of nitrogen (N) fertilisers
together with farmyard manure to irrigated crops and vegetables resulted in N
leaching from the crop rooting zone into groundwater. The soils investigated
had mixed clay mineralogy with a dominance of chlorite, illite, and kaolinite,
whereas major non-clay minerals are predominantly albite, calcite, and quartz.
Influence of earthworms, Aporrectodea spp. (Lumbricidae), on lime burial in pasture soils in south-eastern Australia
Authors: Baker G. H. , Carter P. J. , Barrett V. J.
Published: January 2006

The relative abilities of 3 exotic lumbricid earthworms, the endogeic
Aporrectodea caliginosa and
A. trapezoides and the anecic
A. longa, to bury surface-applied lime and help
ameliorate soil acidity were measured in cages in 7 pasture soils in
south-eastern Australia. All 3 species buried lime, mostly within the top 5 cm
of the soil profile, but A. longa buried it deeper than
A. caliginosa and A. trapezoides.
A. longa significantly increased soil pH at 15–20
cm depth at some sites within 5 months (winter–spring, the earthworm
‘season’ in the Mediterranean climate of south-eastern Australia).
Lime burial varied markedly between sites. These site differences were
explained, at least in part, by variations in rainfall. Lime burial increased
with earthworm density. A minimum density of 214
A. longa/m 2 was needed to
significantly enhance lime burial within one season. Higher densities were
required for the other two species. However, per unit of biomass,
A. caliginosa and A. trapezoides
were generally more able to bury lime in the upper soil layers (2 .
5–10 cm depth) than A. longa. Agricultural soils
in south-eastern Australia are dominated by shallow burrowing species such as
A. caliginosa and A. trapezoides.
Deeper burrowers such as A. longa are rare. Introduction
of A. longa to soils in high-rainfall regions of
south-eastern Australia, where it does not presently occur, should enhance
lime burial and help reduce soil acidity.
Water retention characteristics of soils with contrasting clay mineral composition in semi-arid tropical regions
Authors: Gaiser Thomas , Graef Frieder , Cordeiro José Carvalho
Published: January 2006

In semi-arid tropical regions, the availability of reliable data for water
retention in relation to soil type, texture, and organic matter content is
low. It would be therefore desirable to develop pedotransfer functions (PTF)
in order to estimate water retention characteristics from easily available
soil parameters. In the present study, a soil database containing water
retention characteristics, particle size distribution, and total organic
carbon content of 663 horizons from semi-arid regions in NE Brazil and SE
Niger was used to investigate the effect of contrasting clay mineral
composition on water retention and PTF characteristics for soils from
semi-arid tropical regions. For soil water content at field capacity
(–33 kPa) and wilting point (–1500 kPa), PTFs were established and
validated with disturbed samples from LAC soils (soils containing
predominantly low activity clay; CEC < 24 cmol/kg clay) and non-LAC
soils. The PTFs for the LAC soil group differed considerably from the PTFs for
non-LAC soils with respect to the contribution of total organic carbon and
silt content to the prediction of soil water content at field capacity and
wilting point. For the particle size classes sand, loamy sand, sandy loam, and
sandy clay loam, the mean measured soil water contents in LAC soils were
significantly smaller than in non-LAC soils at a matric potential of –33
kPa. The results demonstrate the influence of clay mineral composition on soil
water retention and its importance for the development of pedotransfer
functions.
Effect of macropore flow on the transport of surface-applied cow urine through a soil profile
Authors: Silva R. G. , Cameron K. C. , Di H. J. , Smith N. P. , Buchan G. D.
Published: January 2006

A field lysimeter experiment was conducted to determine the effect of
macropore flow on the transport of surface-applied cow urine N through soil.
The lysimeters (500 mm diameter by 700 mm depth) used for this experiment were
collected from Templeton fine sandy loam soil (Udic Ustochrept), which had
been under ryegrass (Lolium perenne L.) and white clover
(Trifolium repens L.) pasture for 9–10 years. The
effect of macropore flow on urine-N leaching was determined by leaching
experiments under 0.5 kPa and 0 kPa water tensions (suctions) imposed on top
of the lysimeter using a disc tension infiltrometer. The 0.5 kPa suction
prevented soil pores >600 µm diameter from conducting water and
solutes, while the 0 kPa suction allowed conduction under ‘field
saturated’ condition. Pores >600 µm diameter transmitted about
98% of the total nitrogen (N) leached below 700 mm depth. The main form
of N transmitted under 0 kPa was ammonium (NH4 -N),
accounting for 10.5% of the total N applied at 0 kPa suction. This was
significantly higher than the amount of NH 4 -N leached at 0.5 kPa suction,
which accounted for 0.17% of N applied. The urea-N in the leachate
reached 16 mg/L at 0 kPa suction, and accounted for 1.6% of the
total N applied. No urea was detected in the leachate at the 0.5 kPa suction.
The concentrations and amounts of nitrate (NO3 -N)
leached were very low and did not differ between the two suctions. The forms
and amounts of N leached were affected by the interactions of macropore flow
and N transformations in the soil, and the environmental conditions during the
two leaching events. From this work, it is recommended that stock should be
removed 1–2 days before irrigation water is applied as this will allow
animal urine to diffuse into soil micropores and thus decrease N leaching by
macropore flow.
Effect of antecedent soil water regime and rice straw application time on CH4 emission from rice cultivation
Authors: Xu H. , Cai Z. C. , Li X. P. , Tsuruta H.
Published: January 2006

A pot experiment was carried out to investigate the effect of antecedent water
regime and rice straw application time on methane (CH4)
emission from rice cultivation. The results showed that water regimes of the
previous crops or fallow seasons and timing of rice straw application
significantly influenced CH4 emissions during the
wetland rice-cropping season. The mean CH4 flux of
treatment with continuously flooded fallow (FFE) in the previous crop season
was 6.06 and 5.15 times higher than that of treatment with dry fallow in 1996
and 1997, respectively. Applying rice straw just before soil was flooded for
rice growth (DFL) significantly enhanced CH4 flux by
385.96% in 1996 and 1017.46% in 1997 compared with rice straw
application just before the previous crop season (DFE).
Antecedent water regime and rice straw application time also markedly affected
temporal variation patterns of CH4 fluxes and soil redox
potential (Eh) during the period of time from soil being flooded to rice
harvest. Considerable CH4 was emitted into the
atmosphere from flooding to the early stage of the rice-growing season, and 4
emission maxima occurred several days after flooding and in the early, mid,
and late stages of the rice-growing period for treatments DFL and FFE.
However, for treatment DFE, there was almost no CH4
emission until the middle of the rice-growing season, and
CH4 fluxes in the mid and late stages of the
rice-growing period were also very low. Soil Eh values of treatments FFE and
DFL were compatible for methanogenic bacteria almost every day after flooding.
However, it took 65 days of flooding before the Eh of treatment DFE dropped to
the same level. Differences in the temporal variation patterns of soil Eh were
the main reason why variation patterns of CH4 fluxes
were different.
Amelioration of subsurface acidity in the south-west of Western Australia: downward movement and mass balance of surface-incorporated lime after 2-15 years
Authors: Whitten M. G. , Wong M. T. F. , Rate A. W.
Published: January 2006

Twenty-one lime trial sites in the south-western agricultural region of
Western Australia (WA) ranging in duration from 2 to 15 years were sampled in
1995 to a depth of 40 cm in 10-cm increments. In each case, samples were taken
from both control plots and those with highest lime rates; additionally,
samples were taken from plots with intermediate lime rates at 3 trial
locations. Lime had been incorporated at rates of 2–12 t/ha within
the top 0–10 cm layer at 20 of the sites, and at 15 t/ha within
0–20 cm at the remaining site. The following measurements were made: all
samples, pH (1 : 5 0.01 M CaCl 2 ) and exchangeable
cations (1 : 10 0.1 M BaCl 2 ); selected depths,
undissolved carbonate; selected samples, total Ca (1 : 10 0.2 M HCl) and
exchangeable Ca (1 : 10 0.1 M BaCl 2 buffered to pH
8.2).
The pH of the unlimed subsurface was between 4.0 and 4.5 at 10–20 cm for
15 sites, at 20–30 cm for 7 sites, and at 30–40 cm for 2 sites. In
addition, 3 of the unlimed sites had a pH =4.0 at all of these depths.
Where lime had been applied, the pH was significantly (P
< 0.05) higher than in the controls by at least 0.2 units for 13 sites at
depths of 10 cm below the depth of lime incorporation. The same significantly
elevated pH was found for 5 sites at depths of 20 cm and for 4 sites at depths
of 30 cm. At 5 sites that had also been sampled 3 years previously, the
subsurface pH had increased within 4–7 years of liming with 2.5–5
t/ha. Where added lime could be accounted for, the amount of lime added
explained 65% of the variation in the residual lime effect at a depth
of 10–40 cm. Over all of the wheatbelt trials this represented an
average downward movement of lime to a maximum depth of 40 cm of at least 8.3
kg/ha.year.t CaCO 3 applied (range 0–22.5).
Increased exchangeable Ca corresponded with a decrease in other base cations
in only 2 trials. Decreases in exchangeable Al corresponded with increases in
both pH and exchangeable Ca, but were less than the Ca increases.
Precipitation of exchangeable Al represented an average of about one-sixth of
the pH buffering capacity.
Mass balance for Ca was achieved in 11 out of 20 cases in the wheatbelt, if Ca
loss as nitrate was assumed to occur at rates of leaching published for WA.
Lime recovery on the basis of pH increase was lower. The quantity of lime
accounted for by Ca in the added and the residual undissolved lime, plus the
increase in exchangeable Ca, ranged from <10% to >90%,
with <50% in 9 of 19 cases at 15 trials. Non-exchangeable Ca in HCl
extracts of a subset of surface samples was from 1% to 60% of Ca
not accounted for. In 6 cases the Ca deficit exceeded plausible rates of
acidification, and at 2 of these marked decreases of about 1 t/ha
undissolved CaCO3 corresponded with episodes of high
wind speed and observations of soil erosion. The implications of possible
losses of lime by erosion are discussed.
Surface area of soils of contrasting mineralogies using para-nitrophenol adsorption and its relation to air-dry moisture content of soils
Authors: Hedley C. B. , Saggar S. , Theng B. K. G. , Whitton J. S.
Published: January 2006

The specific surface area (SSA) of a range of soils has been measured by
adsorption of para-nitrophenol
(pNP). These surface soils are representative of the
major soil groups of New Zealand, varying in mineralogy, clay and organic
carbon contents, and cation exchange capacity (CEC). All of the soils are
under pastures of introduced grasses and legumes that have been regularly
fertilised and grazed. The SSAs measured by pNP are
compared with the values calculated from the clay content, clay mineral
composition, and organic carbon content of the soils. Measured SSAs are also
related to the air-dry soil moisture contents.
There is a good 1:1 relation between measured and calculated SSAs. This
correspondence improves when allophanic and smectitic soils are omitted from
the relation. The SSAs measured by pNP are also well
correlated with the air-dry moisture content and CEC of the soils. When
allophanic soils are excluded, a highly significant correlation
(r = 0.894; P < 0.001)
is obtained between pNP surface area and moisture
content of the air-dry soils. When the same relation is applied to an
independent set of soils, 89% of the variations in SSA can be accounted
for. We suggest that the SSAs of many soils can be reasonably deduced from
their air-dry moisture content.
Irrigation of an allophanic soil with dairy factory effluent for 22 years: responses of nutrient storage and soil biota
Authors: Degens B. P. , Schipper L. A. , Claydon J. J. , Russell J. M. , Yeates G. W.
Published: January 2006

Long-term application of wastewater adds large amounts of carbon (C), nitrogen
(N), and phosphorus (P) to soils, and their effects on soil quality are not
fully known. We compared the distribution of C, N, P, and Olsen P in the top
0.75 m of an allophanic soil after 22 years irrigation with dairy factory
effluent with that in a non-irrigated soil. Earthworm species, biomass and
distribution, microbial biomass, microbial activity, and relative use of
substrates were measured to evaluate the contribution of biological processes
to cycling and redistribution of total C. Total C did not differ between
irrigated and non- irrigated soil, although there was less total C in the
0–0.1 m layer and more total C at 0.1–0.5 m in the
effluent-irrigated soil. Microbial biomass C and basal respiration activity
were increased by 4- and 1.6- fold, respectively, in the 0–0.1 m layer
of the irrigated soil. Measurements of relative use of substrates indicated
that the greater microbial biomass in the effluent-irrigated soil was
supported by the inputs of available C (particularly lactose) in the effluent
rather than by greater decomposition of the organic C in the soil. Irrigation
increased total N storage by 2.1 t/ha and total P was increased by 11.5
t/ha. Most of the increase in total N occurred in the 0.1–0.5 m
layers, whereas total P was greater at all depths. Olsen P also increased at
all depths by 1.3- to 23-fold. Approximately 8% of the N and 91%
of the P applied during the past 22 years was stored in the 0–0.75 m
layer of the profile, with the potential for further P storage. Effluent
irrigation increased the total soil nutrient stores, without detrimental
effects on total C storage. Changes in nutrient distribution at the irrigated
site can be partially attributed to leaching and the dominance (155
g/m2 ) of the earthworm
Aporrectodea longa, which forms permanent burrows to
lower depths.
Applying biosolids to acid soils in NSW: Are guideline soil metal limits from other countries appropriate?
Authors: Whatmuff M. S.
Published: January 2006

In New South Wales (NSW) the use of biosolids (sewage sludge) as a soil amendment has become a major issue for regulatory authorities because of the potential impact of biosolids metal contaminants on agricultural produce. Although guidelines regulating the use of biosolids in other countries are based on extensive data sets, these were collected under different soil and climatic conditions than those found locally. This experiment was carried out to determine whether guideline soil metal limits from other countries are appropriate for regulating biosolids application under acid soil conditions that occur in NSW and whether a more intensive series of field experiments needed to be carried out. The uptake of biosolids Cd and Zn by silverbeet (swiss chard, Beta vulgaris) was assessed on soils differing in pHC (4.2–5.8) (pH measured in 0.01 M CaCl2) and soil metal loading (0.53–2.82 mg Cd/kg and 54–159 mg Zn/kg) in the glasshouse and field. Metal uptake by our field-grown silverbeet was >10-fold higher for Cd and >20-fold higher for Zn than was predicted from the slope of the metal uptake response curve for leafy vegetables used in US EPA biosolids guidelines. For some treatments, leaf tissue Cd levels exceeded the maximum permissible concentration for Cd in foodstuffs, and Zn levels were above phytotoxicity thresholds (with some yield reduction) when silverbeet was grown on soils with Cd and Zn concentrations well below soil metal limit concentrations in the United States biosolids guidelines and equal to levels set in the United Kingdom. In addition, biosolids metal uptake under glasshouse conditions was more than twice that in field-grown plants. These results clearly demonstrate the importance of developing NSW-specific biosolids guidelines. Biosolids regulations in NSW should be based on uptake data for a wide range of important food chain and pasture crop species collected in the field and grown under local conditions.
A modified chromium-reducible sulfur method for reduced inorganic sulfur: optimum reaction time for acid sulfate soil
Authors: Sullivan L. A. , Bush R. T. , McConchie D. M.
Published: January 2006

Reaction times for 16 acid sulfate soil materials analysed using a modified
chromium-reducible sulfur method varied between 10 and 15 min, regardless of
whether the samples had been dried and ground prior to analysis or were
analysed without pretreatment. The reaction time for a ground (<63 mm)
pyritic rock sample was 20 min. An optimum reaction time of 20 min is
recommended for analysing acid sulfate soil using the modified method; this
reaction time is much less than the 1 h reaction time used in previous
methods.
Corrigendum to: Hydrology of swelling soils: a review
Authors: Smiles D. E.
Published: January 2006

A generally accepted theory of liquid flow in rigid systems has been used in
soil science for more than 50 years. Liquid flow in systems that change volume
with liquid content is not so well described and remains a major challenge to
soil scientists, although its application in chemical and mining engineering
and soil mechanics is increasingly accepted. Theory of water flow in swelling
soils must satisfy material continuity. It must also account for changes in
the gravitational potential energy of the system during swelling and for
anisotropic stresses that constrain the soil laterally but permit vertical
movement. A macroscopic and phenomenological analysis based on material
balance and Darcy’s law is the most useful first approach to water flow
and volume change in such soils. Use of a material coordinate based on the
solid distribution results in a flow equation analogous to that L. A. Richards
enunciated for non-swelling soils. This framework is strain-independent and
solutions to the flow equation exist for a wide range of practically important
conditions. The approach has been well tested in clay suspensions and
saturated systems such as mine tailings and sediments. It is also applied in
soil mechanics. This paper reviews central elements in application of the
analysis to swelling soils. It argues that, as with use of the Richards’
equation in rigid soils, complexities are evident, but the approach remains
the most coherent and profitable to support current need and future research.
The use of material coordinates, to ensure material balance is assessed
correctly, is simple.
Water quality of gully drainage from texture-contrast soils in the Adelaide Hills in low rainfall years
Authors: Cox J. W. , Ashley R.
Published: January 2006

The volume and quality of drainage water in a gully cutting through a series
of waterlogged, saline, sodic, and sulfidic Xeralfs in the Adelaide Hills,
South Australia, was studied over 3 years. This was done to gain a better
perspective of the relative quantities of contaminants being exported from
agricultural catchments in low rainfall agricultural environments.
It was found that in low rainfall years, when little overland flow occurs and
gully flow is predominantly groundwater discharge and throughflow, loads in
the drainage gully were up to 41 kg/ha.year of sodium and 2 kg/ha.year
of sulfur. Losses of sulfur, magnesium, and calcium followed a similar trend
to sodium losses and could be predicted with significant accuracy. The losses
of phosphorus (5–7 g/ha.year) and nitrate (<2 g/ha.year) were
less predictable. Phosphorus concentrations were of environmental concern each
year whereas nitrate concentrations were only above environmental guidelines
in the driest year. All phosphorus in the gully drainage was transported in
the dissolved form. Dissolved organic carbon concentrations were usually
>26 mg/L and will be costly to treat if used for public water supply.