bluuebunny/crossref_metadata_2025 huggingface dataset:
The equine hypophysis: a gland for all seasons
Authors: Tortonese Domingo J. , Gregory Susan J. , Eagle Rebecca C. , Sneddon Carolyne L. , Young Claire L. , Townsend Julie
Published: September 2002

The intrahypophysial mechanisms involved in the control of gonadotrophin
secretion remain unclear. In the horse, a divergent pattern of gonadotrophins
is observed at different stages of the reproductive cycle in response to a
single secretagogue (gonadotrophin-releasing hormone), and dramatic changes in
fertility take place throughout the year in response to photoperiod. This
species thus provides a useful model to investigate the regulation of
fertility directly at the level of the hypophysis. A series of studies were
undertaken to examine the cytological arrangements and heterogeneity of
gonadotrophin storage in the pars distalis (PD) and pars tuberalis (PT) of the
hypophysis of male and female horses. Specifically, the seasonal and gonadal
effects on distribution, density and hormonal identity of gonadotrophs, the
existence of gonadotroph–lactotroph associations and the expression of
prolactin receptors (PRL-R) as possible morphological bases for the
differential control of gonadotrophin secretion were investigated. It became
apparent that both isolated and clustered gonadotrophs are normally
distributed around the pars intermedia and surrounding capillaries in the PD,
and in the caudal ventral region of the PT. In the PD, no effects of season or
of reproductive state on the density or number of gonadotrophs could be
detected in either male or female animals. In contrast, a fivefold increase in
gonadotroph density was observed in the PT during the sexually active stage.
In males, robust gonadal effects were detected on the gonadotroph population;
orchidectomy significantly reduced both the number and proportion of
gonadotrophs, in relation to other hypophysial cell types, in both the PD and
PT regions. Luteinizing hormone (LH) monohormonal, follicle-stimulating
hormone (FSH) monohormonal and bihormonal gonadotrophs were identified in the
PD and PT of male and female horses. Interestingly, in males, the relative
proportions of gonadotroph subtypes and the LH/FSH monohormonal
gonadotroph ratio were not affected by either season or the presence of the
gonads. In contrast, a larger proportion of monohormonal gonadotrophs was
clearly observed in sexually active females. Specific
gonadotroph–lactotroph associations and expression of PRL-R in cells
other than gonadotrophs were detected in the PD throughout the annual
reproductive cycle. In addition to a stimulatory gonadal effect on lactotroph
density, a substantial gonadal-independent effect of season was apparent on
this variable. The findings have revealed important seasonal and gonadal
effects on the cytological configuration of the equine hypophysis, which may
provide the morphological basis for the intrahypophysial control of fertility.
Genetics, biotechnology and population management of over-abundant mammalian wildlife in Australasia
Authors: Cooper Desmond W. , Herbert Catherine A.
Published: September 2002

Wildlife management involves regulation of population numbers of wild
vertebrate species. In some cases there are too many animals and in others
there are too few. Genetic issues arise in both instances. The historical and
genetic evidence for the number of mammals that were in the founder
populations of successful colonizing species in Australia and New Zealand is
reviewed here. Small numbers have often given rise to large populations,
despite the concomitant loss of genetic variability. Restriction of the number
of over-abundant and pest species by either physical or chemical methods
frequently constitutes very strong artificial selection, which leads to rapid
genetic change; an example of major importance in the two countries is sodium
monofluoroacetate (compound 1080). Pathogenic agents, surgical sterilization,
hormonal contraceptives and translocation have all been used with varying
degrees of success. The strengths and weaknesses of these techniques are
assessed. A method that has received much attention is immunocontraception. We
argue that this attempt to use the animals’ own immune system to
modulate reproduction is incompatible with the basic biological function of
protection against infectious disease. Immune function genes are highly
variable in vertebrates, and so often genetic change in the population
subjected to immunocontraception is likely to be even more rapid than is the
case with lethal agents. Selection for failure to respond to the
immunocontraceptive will occur, and will change immune function in general.
Poor scientific description of ecosystem complexity makes it difficult to
predict the consequences of immunocontraception on wildlife populations.
The irritable male syndrome
Authors: Lincoln Gerald A.
Published: September 2002

The irritable male syndrome (IMS) is a behavioural state of nervousness,
irritability, lethargy and depression that occurs in adult male mammals
following withdrawal of testosterone (T). The negative mood state has been
described in men following withdrawal of androgens and is a striking feature
in male seasonally breeding mammals associated with the end of the mating
season. The Soay ram provides an animal model for IMS. Rams exposed to
alternating 16-week periods of long and short days inactivate the reproductive
axis in response to the switch to long days; the rapid decrease in T secretion
provokes the symptoms of IMS. The animals appear agitated and fearful, and the
incidence of physical wounding owing to fractious inter-male fighting peaks at
this time. Androgen and oestrogen receptors expressed in cells in the preoptic
area and ventromedial/arcuate nuclei appear to relay the effects of T on
behaviour and gonadotrophin secretion, and melatonin receptors expressed in
the premammillary area relay the effects of melatonin/photoperiod. Changes
in the activity of hypothalamic opioidergic, dopaminergic and serotonergic
neural networks may dictate the interactive effects of T and photoperiod. The
working hypothesis is that IMS is a transition state associated with low
hypothalamic amine levels triggered, in part, by the withdrawal of opioid
peptides.
Genetic mutations influencing ovulation rate in sheep
Authors: McNatty K. P. , Juengel J. L. , Wilson T. , Galloway S. M. , Davis G. H.
Published: September 2002

Ovulation rate in mammals is determined by a complex exchange of endocrine
signals between the pituitary gland and the ovary, and by paracrine signals
within ovarian follicles between the oocyte and its adjacent somatic cells.
One approach to identifying factors regulating ovulation rate is to find
mutations that influence the target phenotype and, in this context, sheep are
proving to be remarkable experimental models. Recently, in three sheep
families, namely Inverdale, Hanna and Booroola, the inherited mutation was
mapped to a specific region of the sheep X chromosome (Inverdale, Hanna) or
sheep chromosome 6 (Booroola) and in each, a point mutation was identified in
genes from the bone morphogenetic protein (BMP) relatives of the transforming
growth factor ‚ superfamily or their receptors. In Inverdale (I) and
Hanna (H) sheep, separate point mutations were identified in the BMP15 gene
corresponding to sites in the mature peptide coding region of the BMP15 growth
factor (also known as growth differentiation factor 9B; GDF9B). Expression of
the BMP15 gene was located exclusively in oocytes from the primary stage of
follicular growth. There is a complete block of normal follicular development
in females carrying two copies of the Inverdale mutation (II), two copies of
the Hanna mutation (HH), or one copy of each mutation (HI). Increased
ovulation rates are found in females with only one copy of either mutation
(I+ or H+). In Booroola sheep, a point mutation was identified in
the highly conserved intracellular serine threonine kinase signalling domain
of the BMP-1B receptor. Within the ovary, this gene is expressed in oocytes in
primordial and pre-antral follicles and in granulosa cells from the primary
stage of growth as well as in corpora lutea. The effect of the Booroola
mutation is additive for ovulation rate: animals with one copy of the mutation
have an ovulation rate of 3 or 4, whereas those with two copies have an
ovulation rate of between 5 and 14. Physiological studies of the above
mutations demonstrate that the oocyte plays an active role with respect to its
adjacent somatic cells during follicular development and support the
hypothesis that the oocyte has a significant influence on the number of
follicles that proceed to ovulation.
Germ cells and pluripotent stem cells in the mouse
Authors: McLaren Anne , Durcova-Hills Gabriela
Published: September 2002

For many years, attempts to achieve long-term culture of mouse primordial germ
cells (PGCs) proved unsuccessful, even when feeder layers were used and
individual growth factors were added to the medium. However, when three growth
factors were added simultaneously to the medium, some of the cells continued
to proliferate indefinitely. Similar to embryonic stem cell lines, these
embryonic germ (EG) cell lines were capable of giving rise to embryoid bodies
in vitro, and colonizing all cell lineages in chimeras,
including the germline. Initially, EG cells were made from PGCs before
migration, 8.5 days post coitum (dpc), and after entry into the genital ridge,
11.5 and 12.5 dpc. New EG cell lines from 9.5 dpc (migrating) and 11.5 dpc
PGCs, carrying either a LacZ or GFP transgene, are described here. The
developmental potential of the new EG cell lines
in vitro, in vivoin chimeras, and
in tissue aggregates in organ culture was studied. The EG cells were compared
with PGCs at the stage from which the EG cells were derived. The two cell
types show several similarities, but also some differences in gene expression
and cell behaviour, which require further exploration.
AIDS and sex education for young people in China
Authors: Gao Y. , Lu Z. Z. , Shi R. , Sun X. Y. , Cai Y.
Published: September 2002

Although China has had a rich sexual culture for thousands of years, Chinese
people are usually unwilling to openly discuss issues of sex. Some parents are
quite ignorant of the change in their children’s sexual attitude and
behaviour. In China today, adolescents are becoming much more sexually
liberated. Premarital sex and unplanned pregnancies among teenagers are
increasing. Sexually transmitted diseases (STD) including HIV/AIDS are
also spreading rapidly. However, young people lack basic information on
AIDS/STD and do not know how to protect themselves from these diseases or
how to avoid unintended pregnancies. Several major youth peer education
programmes in China are mentioned in this paper. Among them, a four-year
programme entitled the Australian–Chinese AIDS/STD/Safer Sex
Peer Education Programme for Youth, is discussed in some detail. The programme
has so far reached over 40000 university and school students. Evaluation
results show that the programme is effective in both significantly increasing
students’ knowledge about AIDS/STDs and changing their attitude
towards AIDS patients. In addition, the programme is highly praised by the
students.
Fetal control of parturition in marsupials
Authors: Shaw Geoffrey , Renfree Marilyn B.
Published: September 2002

Among marsupials, the control of birth is best understood in the tammar
wallaby. The young is tiny relative to the mother and is highly altricial.
Adult female tammar wallabies weigh 5 kg, whereas the neonate weighs about 400
mg. However, despite this small size, there is clear evidence that the fetus
provides the signal that sets the timing of birth through several mechanisms.
A fetal signal activates a nitric oxide–guanylate cyclase system in the
myometrium that may maintain myometrial inactivity, and this is down-regulated
at term. There is also up-regulation of prostaglandin (PG) production in the
gravid endometrium during the last two days of gestation that parallels
increased placental PG synthesis, and a pregnancy-specific up-regulation of
oxytocin receptors in the gravid myometrium that increases the responsiveness
of the gravid uterus to mesotocin. These changes facilitate parturition, but
an acute fetus-derived signal appears to trigger parturition. The fetal signal
is probably related to glucocorticoid production. The fetal adrenal matures
and is able to synthesize cortisol by Day 22 of the 26-day gestation. The
fetal adrenals double in size between Day 24 and term, and their cortisol
content increases over 10-fold. The pituitary of the neonate contains
presumptive corticotrophs, and the adrenals increase cortisol production in
response to adrenocorticotrophin. Prostaglandin E2,
which is produced by the placenta, is also a potent stimulant of fetal adrenal
cortisol synthesis. Treatment of tammars in late gestation with the cortisol
agonist, dexamethasone, triggers birth around 23 h later. There is thus a
strong case that fetal adrenal cortisol plays a key role in the preparation
for birth and the timing of it. Further studies are in progress to more
clearly define the mechanisms behind these actions of cortisol.
The derivation and potential use of human embryonic stem cells
Authors: Trounson Alan O.
Published: September 2002

Human embryonic stem cells lines can be derived from human blastocysts at high
efficiency (>50%) by immunosurgical isolation of the inner cell mass
and culture on embryonic fibroblast cell lines. These cells will spontaneously
differentiate into all the primary embryonic lineages
in vitro and in vivo, but they are
unable to form an integrated embryo or body plan by themselves or when
combined with trophectoderm cells. They may be directed into a number of
specific cell types and this enrichment process requires specific growth
factors, cell-surface molecules, matrix molecules and secreted products of
other cell types. Embryonic stem (ES) cells are immortal and represent a major
potential for cell therapies for regenerative medicine. Their use in
transplantation may depend on the formation of a large bank of suitable human
leucocyte antigen (HLA) types or the genetic erasure of their HLA expression.
Successful transplantation may also require induction of tolerance in
recipients and ongoing immune suppression. Although it is possible to
customize ES cells by therapeutic cloning or cytoplasmic transfer, it would
appear unlikely that these strategies will be used extensively for producing
ES cells compatible for transplantation. Embryonic stem cell research may
deliver a new pathway for regenerative medicine.
Sexual reproduction by Phytophthora macrochlamydospora: a group VI species
Authors: Irwin J. A. G. , Mackie J. M.
Published: September 2002

The description of Phytophthora macrochlamydospora
J.A.G.Irwin is emended, following further taxonomic studies with additional
isolates of the organism.
Phytophthora macrochlamydospora is a Group VI
Phytophthora species, producing non-papillate sporangia,
and sex organs in paired culture with
Phytophthora cambivora (Petri) Buisman,
A1 mating type. Sex organs have never previously been
described for P. macrochlamydospora, and this research
has shown that P. cambivora A1
induces selfing in P. macrochlamydospora. Antheridia of
P. macrochlamydospora are always amphigynous.
Phytophthora macrochlamydospora produces large (up to 90
µm), thick-walled chlamydospores that distinguish it from all other
Group VI species.
Dacrycarpus (Podocarpaceae) macrofossils from Miocene sediments at Elands, eastern Australia
Authors: Hill Robert S. , Whang Sung Soo
Published: September 2002

Vegetative remains and male cones containing pollen grains from Miocene
sediments at Elands in northern New South Wales are assigned to the new
Podocarpaceae species Dacrycarpus elandensis. This
species represents the most complete and best preserved
Dacrycarpus macrofossil remains known. These fossils are
morphologically most similar to extant D. imbricatus and
fossil D. latrobensis and
D. linifolius, but the phylogenetic significance of many
of the characters used to make this comparison is unknown.
Dacrycarpus is now extinct in Australia, but
D. elandensis confirms a presence for it in eastern
Australia at a time when rainforest was drying and retracting and
Eucalyptus was expanding its range in the region.
Genetic relationships between Australian fireweed and South African and Madagascan populations of Senecio madagascariensis Poir. and closely related Senecio species
Authors: Radford I. J. , Muller P. , Fiffer S. , Michael P. W.
Published: September 2002

An isozyme and morphological study of
Senecio madagascariensis Poir. and closely related
species in Australia, South Africa and Madagascar was used to investigate the
most likely region of origin for Australian plants known as fireweed.
Collections of seed and voucher specimens were made in New South Wales,
KwaZulu-Natal, East and West Cape Provinces and southern Madagascar and
specimens classified according to recognised taxa or descriptive variants.
Plants were characterised by using isozyme analyses and morphological
observations of both voucher specimens and achenes. Australian fireweed
populations were found to be most closely related to populations of
S. madagascariensis from KwaZulu-Natal in South Africa,
and to be more distantly related to populations from East and West Cape
Provinces in South Africa and from Madagascar. The implications of these
findings are discussed in relation to efforts to locate host-specific
biological control agents for fireweed.
Anetholea (Myrtaceae), a new genus for Backhousia anisata: a cryptic member of the Acmena alliance
Authors: Wilson Peter G. , O'Brien Marcelle M. , Quinn Christopher J.
Published: September 2002

The taxonomic position of Backhousia anisata is
reassessed on morphological and anatomical grounds and its affinities found to
lie with the Acmena alliance.
Backhousia anisata is glabrous and has a suite of wood
anatomical character-states that are more consistent with a phylogenetic
position in or near the Acmena alliance than with other
Backhousia species; molecular data also support this
placement. Since this species lacks the fleshy fruit, thick cotyledons and
hypogeal germination characteristic of other members of the
Acmena alliance, a new genus
Anetholea Peter G.Wilson is described to accommodate it,
and the new combination Anetholea anisata (Vickery)
Peter G.Wilson made.
Auranticarpa, a new genus of Pittosporaceae from northern Australia
Authors: Cayzer Lindy W. , Crisp Michael D. , Telford Ian R. H.
Published: September 2002

Following the revision of the family Pittosporaceae in Australia, a new genus,
Auranticarpa, is described and monographed here to
accommodate a monophyletic group excluded from
Pittosporum in cladistic analyses.
Auranticarpa occurs mostly in monsoonal northern
Australia, and has six species. New combinations are provided for three taxa
previously placed in Pittosporum:
A. melanosperma, A. resinosa
(reinstated this analysis) and A. rhombifolia; and three
are described for the first time: A. edentata,
A. ilicifolia and A. papyracea.
New horizons in soil fertility management
Authors: Price G. H.
Published: September 2002

As the 21st century dawns, we can reflect on the progress made during the 20th
century in the fields broadly covered by soil fertility and its management and
see that progress has been truly amazing. When we consider the many aspects of
soil fertility measurement, the management practices, the changes in
productivity, the awareness of the off-site effects of management practices,
and the speed with which changes can be implemented, we can but wonder what
advances the next 100 years will bring.
We can cast our minds back to where the science of soil fertility and its
management was at the turn of the 20th century, track the progress since then,
and finally discuss where the major advances in the next 10 years are likely
to occur.
Soil microbial biomass, metabolic quotient, and carbon and nitrogen mineralisation in 25-year-old Pinus radiata agroforestry regimes
Authors: Saggar S. , Hedley C. B. , Salt G. J.
Published: September 2002

To understand the effects of agroforestry on soil biological processes we
assessed the conditions in Pinus radiata plantations of
50, 100, 200, and 400 stems/ha after 25 years of growth, and in a
grassland. Agroforestry resulted in a 15–25% decline in soil
organic C and N compared with grassland, and had a significant negative
influence on soil microbial biomass. There was less microbial C and N in soils
under 50–400 stems/ha of P. radiata than in
soils under grassland (0 stems/ha). Soil carbon decomposition and
microbial activity were measured by trapping the carbon dioxide produced by
incubating soils over a 60-week period. The results showed that soil C
decomposition rates were ~1.5 times as much (c. 15 mg
CO2-C/kg soil) in soil from grassland as in that
from plots with 50 or100 stems/ha (c. 10 mg
CO2-C/kg soil), and were further reduced to one half
(c. 5.5 mg CO2-C/kg soil) in
the plots with 200 or 400 stems/ha. The soils under
P. radiata gave off less carbon dioxide per unit of
biomass (the metabolic quotient) than soils under grassland. These shifts in
microbial biomass and its metabolic quotients appear to be associated with
differences in the quantity and ‘quality’ of inputs and soil
organic matter decomposition rates, and to reflect the land use change from
grassland to forest. Given the general ability of soil microbial biomass to
recolonise depopulated areas after tree harvest, we see no problem in
restoring populations of these soil organisms vital in controlling nutrient
cycling after tree felling, provided adequate adjustments to soil pH are made.
Traffic and residue cover effects on infiltration
Authors: Li Yuxia , Tullberg J. N. , Freebairn D. M.
Published: September 2002

Wheel traffic can lead to compaction and degradation of soil physical
properties. This study, as part of a study of controlled traffic farming,
assessed the impact of compaction from wheel traffic on soil that had not been
trafficked for 5 years. A tractor of 40 kN rear axle weight was used to apply
traffic at varying wheelslip on a clay soil with varying residue cover to
simulate effects of traffic typical of grain production operations in the
northern Australian grain belt. A rainfall simulator was used to determine
infiltration characteristics.
Wheel traffic significantly reduced time to ponding, steady infiltration rate,
and total infiltration compared with non-wheeled soil, with or without residue
cover. Non-wheeled soil had 4—5 times greater steady infiltration
rate than wheeled soil, irrespective of residue cover. Wheelslip greater than
10% further reduced steady infiltration rate and total infiltration
compared with that measured for self-propulsion wheeling (3% wheelslip)
under residue-protected conditions. Where there was no compaction from wheel
traffic, residue cover had a greater effect on infiltration capacity, with
steady infiltration rate increasing proportionally with residue cover
(R 2 = 0.98). Residue
cover, however, had much less effect on inf iltration when wheeling was
imposed.
These results demonstrated that the infiltration rate for the non-wheeled soil
under a controlled traffic zero-till system was similar to that of virgin
soil. However, when the soil was wheeled by a medium tractor wheel,
infiltration rate was reduced to that of long-term cropped soil. These results
suggest that wheel traffic, rather than tillage and cropping, might be the
major factor governing infiltration. The exclusion of wheel traffic under a
controlled traffic farming system, combined with conservation tillage,
provides a way to enhance the sustainability of cropping this soil for
improved infiltration, increased plant-available water, and reduced
runoff-driven soil erosion.
Changes in organic and inorganic sulfur fractions and S mineralisation in a Typic Haplustert after long-term cropping with different fertiliser and organic manure inputs
Authors: Reddy K. Sammi , Singh Muneshwar , Tripathi A. K. , Swarup A. , Dwivedi A. K.
Published: September 2002

Changes in the status of organic and inorganic pools of soil sulfur (S), total
nitrogen (N), and organic carbon, and their interrelationships and S
mineralisation were examined on a Typic Haplustert soil after a 27-year
long-term cropping. The results indicated that NPK(+S) applied for 27
years at 50%, 100%, and 150% of optimum recommended rates
and 100% NPK(+S) with farmyard manure (FYM) increased the
organic C and total N status of soil compared with the control and the initial
status of the soil. Intensive cropping with continuous use of 100% NPK
without S resulted in depletion of total, organic, and inorganic S
concentrations by 18.13%, 17.80%, and 21.72%,
respectively, over the control, while the status of total, organic and
inorganic S improved in plots that received graded rates of S with NPK and NPK
plus FYM. Intensive cropping with continuous use of S-free NPK fertiliser
(100% NPK-S) resulted in the widest C: N: S ratio in the soil. NaHCO
3 -extractable total, inorganic, and organic S fractions
and NaOH-extractable total and inorganic S fractions were found to be better
indices of soil S mineralisation than CaCl 2 -extractable inorganic S.
Cumulative amounts of S mineralised during a 14-week incubation period varied
between 2.3 and 21.3 mg S/kg soil and increased with an increase in the
rates of S applied, along with NPK fertilisers. Incorporation of FYM with
100% NPK(+S) resulted in greater cumulative mineralised S over
100% NPK(+S) alone. The cumulative mineralised S showed a
quadratic relationship with the duration of incubation in all the treatments.
Soil organic matter composition, transformation, and microbial colonisation of Gelic Podzols in the coastal region of East Antarctica
Authors: Beyer Lothar , White Daniel M. , Bölter Manfred
Published: September 2002

During recent soil geographical expeditions to Casey Station (Coastal
Antarctica), soils with the morphological features of Gelic Podzols (WRB:
Spodic Haplic Cryosols) were found to be widespread. The purpose of this paper
is to provide further information on these unique soils with respect to soil
organic matter (SOM), microbiology, and soil formation. Antarctic Podzols
develop on solid rock, outwash sediments, and abandoned penguin rookeries. A
comparison of different SOM depth profiles, however, revealed carbon (C) and
nitrogen (N) of unknown origin. The SOM composition was characterised by a
mean C/N ratio of 10, with a high content of carboxyl-C units, probably
derived from amino acids, organic acids, and oxidised carbohydrates.
Pyrolysis-GC/MS and NMR showed a notable variation between SOM in depth
profiles and the horizons within each profile. Microbial colonisation was
affected by the surface vegetation, content of organic C, and the influence of
seabirds. Correlations between selected SOM compounds and bacteria on the
vegetated soils suggested that algal and moss C influence SOM to a great
extent. Most of the long-chain C moieties in the antarctic Podzols appeared to
contain multiple oxygen- and N-containing functional groups, cyclic ionised
and heterocyclic structures, and alkylations. Data suggest that, along with
the podzolisation process, organic acids, non-humified carbohydrates, and
N-containing moieties migrated from the topsoil into the spodic horizons. The
results are discussed with respect to (i) soil formation
and (ii) microbial colonisation in the cold climate. The
Gelic Podzols hold huge amounts of C and N but their origin is poorly
understood. Explaining the origin of the SOM should be a focus for future
research in antarctic soil biogeochemistry.
Soil degradation under cropping and its influence on wheat yield on a weakly structured New Zealand silt loam
Authors: Francis G. S. , Tabley F. J. , White K. M.
Published: September 2002

Results from the first phase of a long-term experiment showed that, after 6
years under pasture, several soil quality attributes had improved compared
with soil cropped annually. The objectives of this study were to quantify the
effects of pasture-induced increases in structural stability and organic
matter (N fertility) on wheat grown in 3 successive seasons following pasture
cultivation. Growing winter wheat after the ploughing of land that had
previously grown perennial grass resulted in gradual reductions in soil
organic C and total N. Reductions in soil microbial biomass C and earthworm
populations were much more rapid. Soil aggregate stability declined rapidly in
the first year after ploughing, but more slowly after that. Soil macroporosity
increased after ploughing, mainly due to the relief of compaction caused by
sheep treading during grazing. The contrasting soil conditions that existed at
the end of the first experimental phase significantly affected the harvest
yield of the first and second wheat crops, with yields 2—3 t/ha
greater after perennial grasses than after annual crops. Variations in harvest
yield and N uptake were explained by differences in soil N fertility and soil
structural conditions. Treatment effects on yield were not detected in the
third wheat crop. For the structural condition and N fertility of this soil,
the extent of improvement during 3 years under perennial pasture was similar
to the extent of decline under 3 years of cropping. This suggests that similar
lengths of pastoral and arable cropping are needed in crop rotations for the
long-term maintenance of these properties in weakly structured silt loam soils
in New Zealand.
Carbon and nitrogen mineralisation in sand, silt, and clay fractions of soils under maize and pasture
Authors: Parfitt R. L. , Salt G. J.
Published: September 2002

Although several studies have quantified either C mineralisation or net N
mineralisation in particle-size fractions, no work has examined simultaneous C
and net N mineralisation. Therefore, we conducted an 18-week laboratory
incubation to compare simultaneous mineralisation in sand, silt, and clay
fractions. The soils (silt loams) were collected from fields of long-term
pasture and maize. Sand, silt, and clay were separated by mild dispersion in
water followed by centrifugation. Samples were incubated at 25°C in
the dark in a quartz matrix, and were leached every 2 weeks with 0.004 M CaCl
2 at a suction of 20 kPa to remove soluble products. C
mineralisation was determined from CO 2 -C evolved each
2 weeks, and mineral N was measured in the leachate. C mineralisation, on a C
basis, followed the order sand > clay > silt, and was related
(r 2 = 0.88) to the
proportion of O-alkyl C (carbohydrate C) estimated from
13 C NMR. The low mineralisation in the silt may also
have been a result of the physical protection of substrates in small pores in
this fraction. The rates of N release were initially rapid from the maize soil
fractions, and were consistent with the high initial mineral-N contents;
subsequently, the rates were slower, and probably related to C mineralisation.
For the pasture soil, N mineralisation followed the order
clay>silt>sand, and was inversely related to the C: N ratios.
Immobilisation appeared to take place in the sand fraction, whereas a large
part of the net N mineralisation occurred in the clay fraction. There is now
good evidence that rates of C and net N mineralisation differ within discrete
particle size fractions, and data on such fractions could be useful for
constructing soil organic matter models.
Mineralogy and potassium release from some Western Australian soils and their size fractions
Authors: Pal Y. , Gilkes R. J. , Wong M. T. F.
Published: September 2002

Seven surface horizon soils and their sand, silt, and clay fractions were
characterised for mineralogy, and K release by extracting samples with 1 mM
CaCl 2 solution daily for 10 days. The low silt content
is characteristic of many Western Australian soils, which may provide a
partial explanation of the paucity of available K in soils that contain little
silt-size primary minerals. The sand and silt fractions were dominated by
quartz and contained significant amounts of K-feldspars. The clay fraction was
dominated by kaolinite, and some samples contained illite/mica, inhibited
vermiculite, and gibbsite. On a per unit weight basis the clay-fraction
released the largest amount of K followed in sequence by the silt and sand.
The contribution of size fractions to total K release by the soil ranged from
50 to 87%, 2 to 7%, and 10 to 44% for the clay, silt, and
sand, respectively. Linear plots of K release versus time
1/2 for the soils, and the sand and silt fractions,
indicated that a parabolic diffusion equation adequately describes the K
release process. For some clay samples this diffusion controlled kinetic is
not strictly obeyed during the initial period of K desorption due to rapid
exchange of adsorbed K at sites on external surfaces. The Elovich equation
plots show a discontinuity in slope and support the hypothesis of the
multireactive nature of K exchange sites for these soils. The parabolic
diffusion rate constant closely predicted K supply to plants as it has a close
positive relationship (r = 0.99) with total K
uptake by ryegrass for 260 days of growth.
Effects of land-use change from grassland to forest on soil sulfur and arylsulfatase activity in New Zealand
Authors: Chen C. R. , Condron L. M. , Davis M. R. , Sherlock R. R.
Published: September 2002

The effects of land-use change from grassland to forest on soil sulfur (S) and
arylsulfatase enzyme activity were investigated by comparing soils under
unimproved grassland and an adjacent 19-year-old exotic forest stand (mixture
of Pinus ponderosa and P. nigra).
Results showed that concentrations of organic S in topsoil under forest were
significantly lower [418 µg/g (0–5 cm), 398
µg/g (5–10 cm)] than corresponding soil depths under
grassland [541 µg/g (0–5 cm), 468 µg/g
(5–10 cm)]. On the other hand, inorganic S concentrations were
significantly higher in soil under forest at all depths compared with
grassland. The inorganic S concentration in soil under grassland increased
with depth, but there was no significant difference observed at different
depths under forest. The decrease in organic S [and organic carbon
(C)] in soil under forest was due to the enhanced mineralisation of
organic components. The accumulation of inorganic S in the soil profile under
forest was mainly attributed to enhanced mineralisation, although decreased
leaching, increased sulfate-S adsorption, and increased atmospheric inputs by
canopy interception of aerosols could have contributed. Microbial biomass C
and S and arylsulfatase activity were higher in topsoil under grassland than
forest. Lower arylsulfatase activities under forest compared with grassland at
the time of sampling suggest that mineralisation of organic S under forest was
not currently mediated primarily by enzyme activity, although enzyme activity
may have been important at earlier stages of forest development. Arylsulfatase
activity was significantly correlated with soil organic C, water-soluble C,
microbial biomass C, total S, organic S, and microbial biomass S in soil under
grassland and forest. Significant concentrations of organic S and microbial
biomass S were present in the forest floor (litter and fermentation layers).
These pools would be important for S cycling and availability in forest
ecosystems. S mineralisation, S fractions, microbial biomass S, microbial
biomass C.
The burrowing characteristics of three common earthworm species
Authors: Francis G. S. , Tabley F. J. , Butler R. C. , Fraser P. M.
Published: September 2002

The burrowing characteristics of 3 common earthworm species were studied using
X-ray computed tomography (CT) scanning in large cylinders (24.1 cm diam.)
packed with topsoil (0–25 cm) and subsoil (25–50 cm) to
representative field bulk density values and sown with ryegrass. Replicated
cylinders (n = 3), kept under constant moisture
and temperature conditions, were inoculated with mature species of
Lumbricus rubellus,
Aporrectodea caliginosa, or
Octolasion cyaneum earthworms at rates similar to their
population density in the field. A non-inoculated, unreplicated control was
also included. The number, biomass, and activity of the 3 species were then
examined. CT scans were taken every 5–10 cm through the soil cylinders
20, 40, and 60 days after inoculation to measure burrow parameters. Mean pore
area was greatest for O. cyaneum
andL. rubellus, and least for
A. caliginosa. Porosity produced by both
L. rubellus and
A. caliginosadeclined with depth.
L. rubellus was most active in the top 5 cm, whereas
A. caliginosa was most active in the top 10 cm.
O. cyaneum created its burrows relatively uniformly
throughout the top 20 cm. No species created significant porosity below 20 cm.
The greatest amount of porosity and number of pores were created in the
cylinders inoculated with A. caliginosa. However,
porosity created per earthworm was least for
A. caliginosa and L. rubellusand
greatest for O. cyaneum. Porosity per biomass was least
for L. rubellus and greatest for
A. caliginosa and O. cyaneum.
A. caliginosa created mainly temporary burrows, with
72–85% of its burrows backfilled between scans.
L. rubellus burrows lasted longer (56–64%
backfilled between successive scans) and hydraulic conductivity measurements
suggested that L. rubellus burrows were
surface-connected and more continuous than those created by
A. caliginosa. It appears that, of the 3 species
studied, L. rubellus has the most beneficial effects on
the measured soil physical properties.
Contamination of soil with fluoride by long-term application of superphosphates to pastures and risk to grazing animals
Authors: McLaughlin M. J. , Stevens D. P. , Keerthisinghe D. G. , Cayley J. W. D. , Ridley A. M.
Published: September 2002

Fluoride (F) is an impurity in phosphatic fertilisers and significant amounts
of F will be added to soils with long-term application of phosphatic
fertiliser to soil. There is a risk that F concentrations in soil may increase
to levels toxic to plants or grazing animals. If F added to soil remains in
the upper soil profile, due to high reactivity with soil, grazing animals
could increase their intake of F through inadvertent ingestion of F-enriched
soil. This study determined the distribution of F in the soil profile of
medium (>8 years) and long-term permanent pastures (>50 years) where F
had been applied as an impurity in phosphatic fertiliser, and assessed the
potential bioavailability of fertiliser F in soil.
Long-term application of superphosphate was linked to increased concentrations
of the more soluble fraction of F in soil. The more soluble F fraction in the
soil surface led to increased F concentrations in herbage (from 11 to 22 mg
F/kg). Fluoride concentrations in herbage were not high enough to be toxic
to plants or grazing animals. Fluoride applied as an impurity in phosphatic
fertiliser was generally found to accumulate in the upper soil profile
(0–6 cm depth). Such increases could also increase F ingestion by
ruminants through incidental soil ingestion while grazing. The risk of
fluorosis to grazing animals is low at present, but with continued application
of fertiliser to soil containing high concentrations of F, and depending on
the bioavailability of fertiliser-derived F in soil, we estimate that
fluorosis may become an issue in the next 25–50 years in highly
fertilised pasture soils.
Changes in soil properties after application of dairy factory effluent to New Zealand volcanic ash and pumice soils
Authors: Sparling Graham P. , Schipper Louis A. , Russell John M.
Published: September 2002

In field studies, we assessed the effects of irrigation with dairy factory
effluent on the surface (0–10 cm) properties of 3 rhyolytic tephra
soils. Horotiu and Te Kowhai soils had been irrigated for 22 years and Taupo
soil for 2 years. Soil properties measured were: total organic C, total N, pH,
bulk density, unsaturated hydraulic conductivity, moisture release
characteristics, readily and totally available water, particle density,
microbial C, soil respiration, mineralisable N, denitrification enzyme
activity, and nitrification potential. Matched, non-irrigated areas were
sampled for comparison.
Average annual loadings (kg/ha) of C, N, and P since 1990 were 1120 kg N,
560 kg P, and 36 300 kg C onto Horotiu soil, and 760 kg N, 380 kg P, and 25
200 kg C onto the Te Kowhai soil. These post-1990 loadings were, on average,
23% less than pre-1990 values. Irrigation for 22 years onto the Horotiu
and Te Kowhai soils caused no change, or a slight decrease, in total C and N
in the topsoil, but microbial C and mineralisable N contents were more than
doubled, and N cycling activity much increased. Soil pH was increased by up to
1.8 units. Unsaturated hydraulic conductivity was increased from 8.5 to 49.8
mm/h on the Horotiu soil, and from 6.5 to 29.0 mm/h on the Te Kowhai
soil. Irrigation increased the volumetric water content between 10 and 100
kPa. Most of the changes in soil properties suggest current application rates
and pasture production can be maintained or increased. The high loading and
mineralisation of N in the irrigated soils raises concerns about potential
leaching of nitrate; current management practices are targeted towards
minimising N loadings from effluent.
Effects of gypsum and stubble retention on the chemical and physical properties of a sodic grey Vertosol in western Victoria
Authors: Valzano F. P. , Greene R. S. B. , Murphy B. W. , Rengasamy P. , Jarwal S. D.
Published: September 2002

The effects of gypsum (0 and 10 t/ha) and stubble management
[retained (SR) or burnt (SB)] on a range of soil chemical, physical,
and micromorphological properties were investigated on a grey Vertosol soil
near Natimuk, Victoria, Australia.
After 2.5 years and 3 winter crops, gypsum, and to a lesser extent the stubble
treatments, resulted in significant changes to the composition of the
exchangeable and soluble cations, and to soil physical properties. When gypsum
was combined with SR, the beneficial effects of this ameliorant on soil
properties were present in both the A and B horizons of the soil. When
combined with SB, the gypsum treatments were only effective in the A horizon.
Organic carbon levels in the A and B horizons were not significantly affected
by the gypsum or stubble treatments. However, micromorphological evidence
indicated that in the A horizon, biological activity was greater in SR plots
than SB plots.
Soil dispersion, penetrometer resistance, and bulk density were reduced in
plots treated with gypsum compared with plots without gypsum. A stubble
management effect was also present, showing lower dispersion scores,
penetrometer resistance values, and bulk densities in SR plots than SB plots.
The available water holding capacity of the soil from Natimuk was
significantly (P < 0.05) higher in the gypsum-treated
plots than in plots without gypsum. This effect was limited to the A horizon
of the SB plots, but was apparent for the A and B horizons of the plots
treated with SR.
The use of gypsum in combination with SR (and break crops) may improve soil
physical and chemical properties at a greater depth than the use of gypsum
with SB alone.
A review of the effects of wastewater sodium on soil physical properties and their implications for irrigation systems
Authors: Halliwell David J. , Barlow Kirsten M. , Nash David M.
Published: September 2002

This paper reviews the effects of wastewater sodium on soil physical
properties, particularly with respect to irrigation systems. Fundamental
sodicity concepts are examined including (i) sodicity
definitions, (ii) the effects of sodium on soil
properties, (iii) a discussion of factors that impede
the infiltration rate and hydraulic conductivity, (iv)
the changes that occur in ionic strength of percolating water in soil, and
(v) consideration of the wastewater and soil
constituents that modify the effective sodium adsorption ratio. Importantly,
the ability for soils to assimilate wastewater over time changes, but these
changes are not often considered prior to the planning of such irrigation
systems, or after the irrigation systems are operating. The general lack of
understanding of sodicity is in part due to the considerable variation in
sodicity definitions. Exchangeable sodium percentage (ESP) values that are
reported to pose a sodicity problem vary around the world due to the different
mineralogy of the soils investigated, but variations in threshold ESP values
have also been caused by a lack of consideration of the solution electrolyte
concentration when determining ESP. In practice, the effects of sodicity may
be evident in soils that are well under reported threshold values. When the
effects of sodicity are identified, the landholder at least has the
opportunity to implement remediation practices. However, more often than not,
the effects of sodium from irrigation water are latent, leading to
considerable problems following the cessation of effluent irrigation and
changed land use.
Sodicity, conventional drainage and bio-drainage in Israel
Authors: Gafni Avi , Zohar Yechiel
Published: September 2002

Years of intensive irrigated farming in the inland valleys of northern Israel
have caused secondary salinity in vast areas. Soil salinity/sodicity
surveys, conducted after the problem was recognised, showed relatively high
levels of sodium adsorption ratio (SAR) in the active soil layers. In a sample
of 7 affected fields, 92.5% of the 1584 SAR measurements on cored soil
samples had values >5, and 39% had values >15. Two ameliorative
approaches were conceived to reverse the evident salinity/sodicity trends
in the Yizre’el Valley: (a) a gravitational, newly
engineered, subsurface drainage system; and (b)
bio-drainage, using eucalypts as a means to control the high water tables.
Both approaches were very successful according to the chosen criteria. The
drainage system, comprising 3 drain components, effectively controlled excess
water from 3 sources: direct infiltration, lateral subsurface flow, and a
deep, presumably upward-seeping, artesian aquifer. The groundwater table
response to the installation of the applied drainage system was immediate. In
the next rainy season, there was an associated and appreciable deep leaching
of Cl– and somewhat less of
Na+. More than 3000 ha of land has been drained in
this way in the past 10 years in the northern, salinity-prone, inland valleys.
The bio-drainage approach, tested in 5 different waterlogged and
salinity-affected sites in the Yizre’el Valley, also proved very
successful. The rates of growth of
Eucalyptus camaldulensis provenances was impressive from
the first year. In the best plot, in the fifth year, biomass production
reached 30 t/ha.year for the Broken-Hill ecotype (NSW) and peaked at 57
t/ha.year for the Hadera (Israel) ecotype. The annual transpiration of
selected trees at Nahalal was 1360 mm, or 3 times the local average annual
precipitation. The groundwater table dropped to below 3 m in the summer of the
fifth year—sufficient to provide saltflushing conditions. In a related
study at the Nahalal site, it was demonstrated that
E. camaldulensis screens out the salts while consuming
soil water. That, coupled with prolonged stresses of salinity and flooding,
can be detrimental to eucalypts. In conclusion, despite sodic conditions,
which are ‘formal’ by definition and which prevail in much of the
area of our northern valleys, drainage, whether conventional or biological, if
well-designed and implemented, is a viable means for controlling local
hydrology and restraining salinitysodicity trends.