bluuebunny/crossref_metadata_2025 huggingface dataset:
Contributions of nitrogen by field pea (Pisum sativum L.) in a continuous cropping sequence compared with a lucerne (Medicago sativa L.)-based pasture ley in the Victorian Wimmera
Authors: McCallum M. H. , Peoples M. B. , Connor D. J.
Published: September 2002

The nitrogen (N) dynamics (N2 fixation inputs, changes
in soil mineral N and total N, N removed in agricultural produce) of a
lucerne-based phase farming system (grazed lucerne–annual
medic–ryegrass pastures grown in rotation with crops) was compared with
that of continuous cropping (cereal, oilseed, and legume pulse crops) in the
Victorian Wimmera. The contribution of biological N2
fixation to the N economy of these different systems was strongly linked to
biomass production by the legume components of pastures, or field pea in the
cropping sequence. The amount of fixed N present in field pea shoots or the
total amount of N2 estimated to be fixed by the whole
plant (shoots and roots) (121–175 kg N/ha.crop and 181–262 kg
N/ha.crop, respectively) was generally greater than the combined measured
annual inputs of fixed N by lucerne and annual medic during a pasture ley
(40–95 kg N/ha.year in herbage, 80–190 kg N/ha.year in
total plant), although large amounts of N were removed in the field pea grain
at harvest (115–151 kg N/ha.crop). Over 2 years (1995–96), the
seasonal rainfall patterns had a much larger impact on the growth, dry matter
production, and N2 fixation of annual medic compared
with lucerne. Winter-cleaning of ryegrass from the pasture before cropping
resulted in a greater legume content in the pasture and generally increased
amounts of fixed N in herbage (by up to 55 kg N/ha.year). Total soil N at
depth (0.5–1.0 m) was significantly greater after 2–4 years of
pasture than under continuous cropping. In one year (1996), the amount of soil
mineral N following a winter-cleaned pasture was greater (by 32–45 kg
N/ha, 0–1 m) than after either canola or wheat, producing a yield
benefit in a subsequent canola crop that was equivalent to pre-drilling 46 kg
N/ha as fertiliser. However, despite some improvements in N fertility,
large crop responses to N fertiliser were still observed following pasture.
Grain yield was increased by 0.33–0.55 t/ha in canola and by 1.0
t/ha in wheat, grain protein raised by 0.7–2.3% in canola and
by 1.3% in wheat, and oil yield in canola enhanced by 124–205
kg/ha with pre-drilled applications of fertiliser N (46 kg/ha). It is
speculated that more legume-dominant pastures (>80%) could provide
greater flow-on N benefits to farming systems in the Wimmera than the mixed
legume–grass swards used in the present study. However, it is likely
that a need will remain for supplementary fertiliser N to optimise the
nutrition of subsequent non-legume crops in the region.
Simulation studies of nitrogen concentration in the diet of sheep grazing Mitchell and mulga grasslands in western Queensland
Authors: Hall W. B. , Rickert K. G. , McKeon G. M. , Carter J. O.
Published: September 2002

This study examined the potential to simulate the quality, as indicated by
nitrogen concentration, of the diet of sheep grazing the Mitchell and mulga
grasslands of western Queensland. Development of this simulation capability
will allow pasture growth and animal production models to be more easily
coupled. Modifications and optimisation of an existing beef cattle diet
selection model, in conjunction with a single sward pasture model, accounted
for 69.1% (P < 0.001) and 41.9%
(P < 0.001) of variation in sheep dietary nitrogen
concentrations observed from grazing trials on Mitchell and mulga grasslands,
respectively. Failure to simulate some of the higher recorded dietary nitrogen
concentrations was probably associated with high forb content in the diet.
Examination of the results indicated that development of pasture growth models
which simulate major pasture species, or groups of species (e.g. perennial
grasses, annual grasses, browse, forbs, legumes), would appear to be necessary
before diet selection models will be better able to explain the variation in
dietary quality observed in grazing animals.
Gibberellic acid-sensitive dwarfing genes reduce plant height to increase kernel number and grain yield of wheat
Authors: Rebetzke G. J. , Richards R. A.
Published: September 2002

The Norin-10 dwarfing genes, Rht-B1b
(Rht1) and Rht-D1b
(Rht2), have been used to reduce plant height and
increase grain yield in wheat breeding programs worldwide. Other dwarfing
genes are available to reduce plant height of wheat but little is known of
their effects on grain yield. A set of random,
F5-derived wheat lines containing either minor genes for
reduced plant height, or major gibberellic acid (GA) sensitive
Rht8 and Rht9 dwarfing genes, were
obtained from 3 different populations. Environment mean yields ranged from 2.5
to 4.6 t/ha. Genotypic variation was large and significant
(P < 0.05) for plant height, grain yield and its
components, and kernel number and size. Approximately 30% of lines were
as short as variety Hartog, while kernel number per m2,
harvest index, and grain yield of the shortest GA-sensitive lines were not
significantly different (P < 0.05) from the
commercial semidwarf checks Janz or Hartog. Furthermore, genotypic differences
in plant height were genetically correlated (rg) with
variation in kernel number (rg
= −0.76*), harvest index (−0.71*), and grain yield
(−0.62*). These correlated effects were confirmed with retrospective
selection for height and were consistent with reported height effects of
Rht-B1b and Rht-D1b dwarfing genes
on kernel number and harvest index in wheat. Plant height differences among
GA-sensitive lines were independent of variation in seedling characteristics
(r2 = 0.01–0.02
n.s.), while a number of reduced-height lines produced 50% longer
coleoptiles and greater seedling biomass than Janz. These studies demonstrate
a correlation between the shorter height of GA-sensitive dwarfing genes and
increased grain yield, and suggest their potential for improving wheat
establishment through greater coleoptile length and early vigour.
Effect of seed zinc content on early growth of barley (Hordeum vulgare L.) under low and adequate soil zinc supply
Authors: Genc Yusuf , McDonald Glenn K. , Graham Robin D.
Published: September 2002

Worldwide, barley is often grown on zinc (Zn) deficient soils. Screening for
varieties tolerant of low soil Zn (Zn-efficient varieties) generally involves
assessing growth or yield of plants grown at different levels of Zn supply.
Seed nutrient reserves can influence the growth of the plant; however, there
have been no reports on the effect of seed Zn content on the growth of barley.
In 2 experiments, we studied the effect of seed Zn content on early growth of
barley in 2 genotypes, Amagi Nijo and Tantangara. In Expt 1, the amounts of Zn
in the seed ranged from 0.4 to 0.7 µg/seed, whereas in Expt 2, seed
Zn ranged from 0.7 to 5.0 µg/seed. The plants were grown in a
Zn-deficient siliceous sand with Zn added at 0, 0.04, 0.2, 0.8, and 3.2 mg
Zn/kg soil in Expt 1 and at 0, 0.04, and 0.8 mg Zn/kg soil in Expt 2,
and harvested at tillering. Growth and expression of visual symptoms were
measured.
Plants grown from seed with low Zn content developed symptoms of Zn deficiency
by the 2-leaf stage in soil with no soil-applied Zn. Symptoms were reduced
markedly as seed Zn content increased. Shoot and root growth increased as the
amount of Zn in seed increased, but the effect was most evident when soil Zn
supply was limiting plant growth (≤0.04 mg Zn/kg soil). For instance,
when no Zn was added to the soil, shoot dry weight of plants grown from
high-Zn seed was 108% greater than that of plants grown from low-Zn
seed, whereas at 0.04 and 0.8 mg Zn/kg soil, the increases were only
52% and 18%, respectively. Soil Zn application significantly
increased tissue Zn concentrations. However, the effect of seed Zn content on
tissue Zn concentrations was significant only at very high levels of seed Zn.
The results presented showed that seed Zn improves vegetative growth in
barley, especially when Zn supply is deficient for plant growth. Seed Zn
content also affected the determination of Zn efficiency of genotypes, and
comparisons of dry matter production of seedlings grown from seed with a wide
range in Zn content may alter their rankings for Zn efficiency as determined
in this pot assay. The results indicate that seed of similar Zn content needs
to be used when comparing genotypes for determination of Zn efficiency.
Water balance of annual and perennial pastures on a duplex soil in a Mediterranean environment
Authors: Ward P. R . , Dunin F. X. , Micin S. F.
Published: September 2002

Dryland salinity in southern Australia is largely due to inadequate water use
by annual agricultural crops and pastures. Perennial pastures, such as
lucerne, have been proposed as a possible means of increasing water use whilst
maintaining flexibility in agricultural rotations. In a trial located on a
duplex soil near Katanning, Western Australia, lucerne and subterranean clover
pastures both used water at rates indistinguishable from potential
evapotranspiration during the winter and early spring of 3 consecutive years
(1995–97), and completely exhausted water stored in the A horizon.
Lucerne, through a deeper rooting pattern and by maintaining activity in the
summer and autumn, used approximately 50 mm more water than the annual pasture
during each 12-month period. This resulted in reduced deep drainage below 1.2
m in the 1996 season (30 mm compared with 80 mm under annual pasture). With
average regional groundwater recharge in the range 10–50 mm, the
reductions in drainage observed under lucerne show promise in reducing the
regional impact of dryland salinity.
Barley malting quality and yield interrelationships and the effect on yield distribution of selection for malting quality in the early generations
Authors: Lu M. Q. , O'Brien L. , Stuart I. M.
Published: September 2002

Relationships between malting quality attributes and grain yield in
segregating populations can profoundly influence the intensity and sequence of
trait selection. Consequently, the interrelationships between malting quality
parameters predicted by near infrared transmittance (NIT) spectroscopy, grain
weight, and grain yield in unselected populations of F2,
F3, and F4 breeding lines from 4
barley crosses were examined. The simple and partial correlations between malt
extract, protein content, and diastatic power were similar to those reported
in previous studies except for a positive correlation between malt extract and
diastatic power in the F2 and F3
generations. This positive relationship should enhance selection for improved
malting quality in breeding programs.
There were no relationships between grain yield and malting quality
attributes, which would have an adverse impact on the intensity and sequence
of trait selection.
The effect of F2 and F3 selection
for malting quality on F3 and F4
yield distributions was estimated by comparing the F3
and F4 yield distributions of the entire unselected
population with those for the selected populations. Individual selection and
sequential independent selection in the F2 and
F3 generation for malting quality parameters predicted
by NIT spectroscopy and grain weight in 4 crosses generally did not alter the
nature of the subsequent yield distributions, yet 78–90% of lines
could be discarded and there still existed adequate genetic gain for grain
yield in the retained population of potentially good malting quality lines.
These results indicate that barley breeders could use NIT spectroscopy to
efficiently select in the early generations for malting quality prior to the
conduct of yield testing and obtain good genetic gain for both malting quality
and grain yield.
Soil audit of a long-term phosphate experiment in south-western Victoria: total phosphorus, sulfur, nitrogen, and major cations
Authors: McCaskill M. R. , Cayley J. W. D.
Published: September 2002

A nutrient audit was conducted on a long-term grazed fertiliser experiment at
Hamilton in south-western Victoria to determine the fate of applied phosphorus
(P) and sulfur (S). Single superphosphate had been applied at rates averaging
between 1 and 33 kg P/ha.year since the start of the experiment in 1977.
Soil samples were taken in 1994 by coring to a depth of 80 cm, and analysed
for total soil nutrient concentration. Most (80%) applied P was in the
top 43 cm of the soil profile. A further 6.5% had been transferred to
sheep camp areas and 6.5% had been exported as product. It was
estimated that <0.4% of applied P left the site in surface water
movement. Unaccounted P (6.6%) was probably in the soil, but could not
be detected because of the relatively wide confidence margin for total soil P.
Only 31% of applied S was detected in the top 43 cm, 3.6% had
been transferred to sheep camps, and 4.9% exported in product.
Unaccounted S (60%) had probably moved deeper into the soil where it
could not be detected from background levels of total soil S.
Bulk density in the 0–5-cm layer increased by 1% for each
additional ewe per ha, but decreased by up to 0.4% for each
kg/ha.year of P fertiliser. Soil nitrogen (N) accumulated at 46 kg
N/ha.year at the highest P application rate.Differences in total potassium
(K) between low and high fertility treatments indicated that 20 kg
K/ha.year had moved out of the 5–19-cm soil layer of the high
fertility treatment. This was attributed to competition for exchange sites
from calcium (Ca) in the superphosphate. It was concluded that fertilisers
with a higher P : S ratio and a lower Ca content than superphosphate are more
appropriate for the basalt-derived duplex soils because they would reduce
problems associated with displacement of K in the soil profile.
Field studies on the biofumigation of take-all by Brassica break crops
Authors: Kirkegaard J. A. , Sarwar M. , Wong P. T. W. , Mead A. , Howe G. , Newell M.
Published: September 2002

Biofumigation refers to the suppression of soil-borne pathogens and pests by
biocidal compounds released by Brassica crops when
glucosinolates (GSL) in their residues decay in soil. We conducted field
studies at 2 sites to investigate the hypothesis that biofumigation by
Brassica break crops would reduce inoculum of the
take-all fungus Gaeumannomyces graminis var.
tritici (Ggt) to lower levels than
non-Brassica break crops, and thereby reduce Ggt
infection and associated yield loss in subsequent wheat crops. High and
uniform levels of Ggt were established at the sites in the first year of the
experiments by sowing wheat with sterilised ryegrass seed infested with Ggt.
Ggt inoculum declined more rapidly under Brassica crops
than under linola and this reduction coincided with the period of root decay
and reduced root glucosinolate concentrations around crop maturity. There was
no consistent difference in inoculum reduction between canola
(Brassica napus) and Indian mustard
(Brassica juncea), nor between cultivars with high and
low root GSL within each species. Despite significant inoculum reduction
attributable to biofumigation, there were no differences in the expression of
disease and associated impacts on the yield of subsequent wheat crops across
the sites. Seasonal conditions, in particular the distribution of rainfall in
both the summer–autumn fallow following the break crops and during the
subsequent wheat crop, influenced inoculum survival and subsequent disease
development. In wet summers, inoculum declined to low levels following all
break crops and no extra benefit from biofumigation was evident. In dry
summers the lower inoculum levels following brassicas persisted until the
following wheat crops were sown but subsequent development of the disease was
influenced more by seasonal conditions than by initial inoculum levels.
Significant extra benefits of biofumigation were observed in one experiment
where wheat was sown within the break crops to simulate grass weed hosts of
Ggt. Under these circumstances there was greater reduction in Ggt inoculum
under canola than linseed and an associated decrease in disease development.
For host-dependent pathogens such as Ggt, we hypothesise that the benefits of
biofumigation to subsequent wheat crops will therefore be restricted to
specific circumstances in which inoculum is preserved during and after the
break crops (i.e. dry conditions, grass hosts present) and where conditions in
the following wheat crop lead to significant disease development (early
sowing, wet autumn and spring, dry periods during grain filling).
Diurnal changes in the concentration of water-soluble carbohydrates in Phalaris aquatica L. pasture in spring, and the effect of short-term shading
Authors: Ciavarella T. A. , Simpson R. J. , Dove H. , Leury B. J. , Sims I. M.
Published: September 2002

The concentrations of water-soluble carbohydrate (WSC) and its components,
starch, total nitrogen, and dry matter of phalaris
(Phalaris aquatica L. cv. Australian) pasture were
varied by shading for periods ranging from 38.5 to 46.5 h. In unshaded
pasture, WSC concentrations were lowest at sunrise [103 mg/g dry
matter (DM)] and increased until early afternoon (to 160 mg/g DM).
Sucrose and starch increased in concentration during daylight, whilst the
concentrations of glucose, fructose, fructan, and a component of WSC
considered to be mainly the carbohydrate moiety of glycoside(s) were
relatively constant. The concentrations of starch, and all components of WSC
except sucrose, were reduced by shading, but increased to the concentrations
observed in the unshaded pasture within 2–4 h after removal of the
cover. The fructans present in phalaris were determined to be oligosaccharides
of degree of polymerisation (DP) 3 and DP 4 and high molecular mass fructans
with DP >10. Nitrogen concentration of shaded pasture was initially higher
(4.7% DM) than in unshaded pasture (3.9% DM), but decreased
after removal of the shade cover. Dry matter content was reduced in shaded
pasture, partly due to increased retention of water on the exterior of plants.
The experiment was a precursor for a grazing trial in which the WSC content of
pasture was to be altered by shading. It indicated that shading would
potentially alter WSC and N concentrations, and DM content, but would have
only a relatively small impact on the digestibility of the pasture.
The nutrition of grazing ewes during pregnancy and lactation: a comparison of alkane-based and chromium/in vitro-based estimates of herbage intake
Authors: Dove H. , Freer M. , Foot J. Z.
Published: September 2002

The n-alkane and chromium/in vitro procedures for
estimating herbage intake were compared in grazing ewes during late pregnancy,
early lactation, and mid-lactation. To ensure differences in herbage intake,
the ewes were grazed in 4 plots of phalaris-dominant pasture at 2 levels of
stocking: 17.1 ewes/ha and 30.8 ewes/ha. To investigate whether either
procedure for estimating herbage intake was influenced by supplement
consumption, half of the ewes at each stocking level received 500 g/day
air-dry of a pelletted supplement (1 : 1 milled oat grain : sunflower meal).
Supplement intakes were estimated using tritiated gypsum as a marker. During
intake measurement periods, ewes were dosed twice daily with both alkane
capsules and capsules containing chromium sesquioxide. For the last 6 days of
the 12-day dosing period, rectal faecal samples were taken twice daily,
immediately before the dosing. Over these same periods, wether sheep fitted
with faecal collection harnesses were similarly dosed and sampled, and their
total faecal output collected to establish the faecal recovery of chromium and
the alkanes.
Herbage intakes were estimated using the C27/C28, C29/C28,
C31/C32, and C33/C32 alkane pairs. Estimates of intake based on the
shorter alkane pairs were lower than those estimated with the C33/C32
alkane pair, by amounts which differed between the periods. Evidence is
presented that estimates based on the last pair of alkanes (C33/C32) are
the most accurate and are also more accurate than those based on the
chromium/in vitro procedure. The relationship
between these 2 methods for estimating intake was different in mid-pregnancy
compared with either stage of lactation. The consumption of supplement did not
interfere with any of the methods for estimating herbage intake.
Estimates of faecal output based on the use of chromium, C28 alkane, or C32 as
an external marker were statistically identical, indicating that the
difference between the 2 methods for estimating herbage intake was not related
to a failure to accommodate the incomplete recovery of any of the markers used
or to the failure of rectal grab samples to be representative of total faeces.
Our results indicate that herbage collected by oesophageally fistulated (OF)
sheep was representative of that grazed by the ewes and could thus be used to
provide the herbage alkane data needed to estimate herbage intake by the
alkane method. However, the in vitro digestibility
values obtained from the OF samples did not represent the digestibilities
actually occurring in vivo. This was the main cause of
the observed difference between the 2 methods for estimating intake. Possible
reasons for the differences between the in vitro and
in vivo estimates of digestibility are discussed.
Responses of IsaBrown laying hens to a pre-layer diet containing additional calcium and to dietary protein and lysine concentrations during lay
Authors: Balnave D. , Gill R. J. , Li X. , Bryden W. L.
Published: September 2002

IsaBrown pullets were obtained from a commercial breeder at 15 (Expt 1) and 16
(Expt 2) weeks of age and housed in either single-bird or multiple 5-bird
cages in a high rise, windowless layer house in which temperatures were
maintained below 30˚C by computerised control of fans and evaporative
cooling pads. In Expt 1, they were fed either a grower diet or a pre-layer
diet consisting of the grower diet containing additional calcium to 18 weeks
of age and then maintained during lay to 56 weeks of age on diets containing
either 160 or 180 g crude protein (CP)/kg. In Expt 2, they were fed the
grower diet to 19 weeks of age and then 1 of 5 diets similar in all
ingredients except that the lysine concentration varied between 7.35 and 8.95
g/kg in increments of 0.4 g/kg. The L-lysine HCl supplements were
added in lieu of solka floc, an inert cellulose supplement.
In Expt 1, mortality was low (2.25%), peak egg production was high
(95–98%), and the mean rate of lay at 56 weeks of age was above
88%. The diet fed prior to lay had no significant effect on production
during lay. Feed intake and egg production were similar for hens fed both
dietary protein levels during lay, and egg weight and egg mass output were
greater for hens fed the diet containing 180 g CP/kg. Hens in
multiple-bird cages ate significantlyless feed for a significantly smaller
daily egg mass output. In Expt 2, increasing the dietary lysine concentration
significantly reduced feed intake and significantly increased lysine intake,
egg shell breaking strength, and albumen height. Multiple-caged hens had a
significantly lower hen-housed egg production as a result of a 7-fold increase
in mortality compared with hens in single cages, due mainly to cannibalism.
The daily lysine requirement formaximum egg production approximated 940 mg for
hens in single cages and 975 mg for hens in multiple-bird cages.
Incidence of ryegrass endophyte (Neotyphodium lolii) and diversity of associated alkaloid concentrations among naturalised populations of perennial ryegrass (Lolium perenne L.)
Authors: Reed K. F. M. , Leonforte A. , Cunningham P. J. , Walsh J. R. , Allen D. I. , Johnstone G. R. , Kearney G.
Published: September 2002

The mutualistic association between perennial ryegrass
(Lolium perenne L.) and the ryegrass endophyte
Neotyphodium lolii (Latch, Christensen and Samuels)
Glenn, Bacon and Hanlin, previously assigned to the genus
Acremonium, is known to have a major impact on pasture
and animal production. The perennial ryegrass ecotypes Victorian and Kangaroo
Valley are the most widely sown varieties of grass in Australian pasture. The
incidence of ryegrass endophyte (N. lolii) in these
ecotypes, and the production of alkaloids associated with theryegrass
endophyte, are largely unexplored. Fifty-six populations of Victorian and 45
of Kangaroo Valley were sampled from old pasture within the recognised zones
of naturalisation of both ecotypes. All of the 101 populations examined were
infected with ryegrass endophyte. The mean ryegrass endophyte
(N. lolii) frequency for plants within the populations
of the Victorian and Kangaroo Valley ecotypes was 88% and 93%,
respectively.
Alkaloid concentrations were determined from infected plants for 39 Kangaroo
Valley populations and, in a separate study, for 24 Victorian populations.
Ergovaline concentration was above the critical level of 0.4 mg/kg (above
which clinical symptoms are observed) for 10% of the Kangaroo Valley
populations and 17% of the Victorian populations. For lolitrem B, all
Victorian populations were below the critical level of 1.8 mg/kg, but
28% of the Kangaroo Valley populations had mean concentrations above
the critical level, 1.8 mg/kg. Concentrations for individual plants were
<5 mg/kg for ergovaline, <6 mg/kg for lolitrem B, and <48
mg/kg for peramine. Within each ecotype examined, significant variation
(P < 0.05) in the mean concentrations of ergovaline,
lolitrem B, and peramine was found between the populations of naturalised
perennial ryegrass. Mean concentrations for some of the various naturalised
populations were higher than that observed in some of the control cultivars.
Low ergovaline and lolitrem B concentrations observed for individual genotypes
indicate scope for selecting grass endophyte combinations characterised by
optimum production of alkaloids.
Lucerne removal before a cropping phase
Authors: Angus J. F. , Gault R. R. , Good A. J. , Hart A. B. , Jones T. D. , Peoples M. B.
Published: September 2002

Growing dryland crops after lucerne is known to be risky because of the lack
of residual soil water. We investigated ways of reducing this risk by removing
portions of a lucerne pasture, using either herbicides or cultivation, at
monthly intervals between November and April, before sowing a wheat crop in
May, followed by a canola crop in the following year. The experimental site
was on a red-brown earth in southern New South Wales. Lucerne removal was
incomplete when the wheat was sown, so all lucerne plants were removed from
half of each plot with a post-emergence herbicide, to allow comparisons of
intercropped wheat–lucerne and wheat monoculture. Measurements were made
on crop growth, yield, grain quality, soil water, and soil mineral nitrogen
(N) before and after both crops.
On average, each additional month between lucerne removal and wheat sowing led
to a yield increase of 8% and a grain protein increase of 0.3
percentage units. The main reason for the increases was additional soil
mineral N, associated with a longer period of mineralisation. The soil water
content at the time of wheat sowing was greater with early lucerne removal but
the growing season rainfall did not limit yields, and there was more residual
soil water at the time of wheat maturity where lucerne had been removed late
and yields were lower. Method of lucerne removal did not significantly affect
wheat yield, grain protein, soil water, or soil mineral N. The portions of the
plots containing lucerne plants that survived the initial removal attempt
produced similar wheat yields to the portions where lucerne had been totally
removed, but grain protein was lower.
The following growing season was drier, but despite less residual soil water
where lucerne had been removed earlier in the previous year, the average
canola yield was 2.5% greater for each additional month of fallow. The
increase again appeared to be due to more residual mineral N. The seed oil
concentration also decreased in response to later lucerne removal but seed
protein increased. Where lucerne plants had been retained in the previous
wheat crop, canola yield was lower than where they had been totally removed,
apparently because of less soil water at sowing.
Over the 2 years of the experiment, the net supply of mineral N was 374 kg
N/ha, equivalent to an annual net mineralisation of 2% of the total
soil N. The initial mineralisation rate was slow, suggesting that the soil may
be deficient in mineral N soon after lucerne removal.
Potential deep drainage under wheat crops in a Mediterranean climate. I. Temporal and spatial variability
Authors: Asseng S. , Fillery I. R. P. , Dunin F. X. , Keating B. A. , Meinke H.
Published: September 2002

High rates of deep drainage (water loss below the root-zone) in Western
Australia are contributing to groundwater recharge and secondary salinity.
However, quantifying potential drainage through measurements is hampered by
the high degree of complexity of these systems as a result of diverse soil
types, a range of crops, different rainfall regions, and in particular the
inherent season-to-season variability. Simulation models can provide the
appropriate means to extrapolate across time and space. The Agricultural
Production Systems Simulator (APSIM) was used to analyse deep drainage under
wheat crops in the Mediterranean climate of the central Western Australian
wheatbelt. In addition to rigorous model testing elsewhere, comparisons
between simulated and observed soil water loss, evapotranspiration, and deep
drainage for different soil types and seasons confirmed the reasonable
performance of the APSIM model.
The APSIM model was run with historical weather records (70–90 years)
across 2 transects from the coast (high rainfall zone) to the eastern edge of
the wheatbelt (low rainfall zone). Soils were classified as 5 major types:
deep sand, deep loamy sand, acid loamy sand, shallow duplex (waterlogging),
and clay soil (non-waterlogging). Simulations were carried out on these soil
types with historical weather records, assuming current crop management and
cultivars. Soil water profiles were reset each year to the lower limit of
plant-available water, assuming maximum water use in the previous crop.
Results stressed the high degree of seasonal variability of deep drainage
ranging from 0 to 386 mm at Moora in the high rainfall region (461 mm/year
average rainfall), from 0 to 296 mm at Wongan Hills in the medium rainfall
region (386 mm/year average rainfall), and from 0 to 234 mm at Merredin in
the low rainfall region (310 mm/year average rainfall). The largest
amounts of drainage occurred in soils with lowest extractable water-holding
capacities. Estimates of annual drainage varied with soil type and location.
For example, average (s.d.) annual drainage at Moora, Wongan Hills, and
Merredin was 134 (73), 90 (61), and 36 (43) mm on a sand, and 57 (64), 26
(43), and 4 (18) mm on a clay soil, respectively. These values are an order of
magnitude higher than drainage reported elsewhere under native vegetation.
When not resetting the soil each year, carry-over of water left behind in the
soil reduced the water storage capacity in the subsequent year, increasing
long-term average deep drainage, depending on soil type and rainfall region.
The analyses revealed the extent of the excess water problem that currently
threatens the sustainability of the wheat-based farming systems in Western
Australia.
Science Goals for Antarctic Infrared Telescopes
Authors: Burton Michael G. , Storey John W. V. , Ashley Michael C. B.
Published: September 2002

Over the past few years, site-testing at the South Pole has revealed conditions that are uniquely favourable for infrared astronomy. In particular, the exceptionally low sky brightness throughout the near and mid-infrared leads to the possibility of a modest-sized telescope achieving comparable sensitivity to that of existing 8–10 metre class telescopes. An 8 metre Antarctic telescope, if constructed, would yield performance that would be unrivalled until the advent of the NGST. In this paper we review the scientific potential of infrared telescopes in Antarctica, and discuss their complementarity with existing 8–10 metre class telescopes and future proposed space telescopes. In particular, we discuss the role that a 2 metre class infrared telescope plays in future plans for the development of an observatory on the Antarctic plateau.
Total Magnitudes of Virgo Galaxies. I. Construction of a Self-Consistent Reference Dataset Spanning 8th to 18th Magnitude
Authors: Ke-shih Young Christopher
Published: September 2002

The main objectives of this series of papers are: (1) to demonstrate the existence of serious mutual disagreements between established total (and other integrated) magnitude scales forVirgo galaxies; (2) to attempt to quantify both the systematic and random errors present within these magnitude scales; (3) to investigate the origins of any large error uncovered; and thereby (4) to encourage the general adoption of rigorous total-magnitude measurement procedures by the astronomical community. The ramifications of the findings presented in this series of papers will be discussed in detail at a later date.

In this paper, the first in the series, a self-consistent dataset of trustworthy total-magnitude measurements is compiled for a sample of Virgo galaxies spanning a range of 10 000 in apparent brightness, based on only the most reliable measurements and photometry currently available. This reference dataset, which includes luminosity profile shape information, will be used in subsequent papers as one of the bases for assessing existing magnitude scales forVirgo galaxies. As most published magnitudes are based on B–band observations, this series of papers will also focus primarily on B–bnd measurements.
Evolution of the Radio Remnant of SN 1987A: 1990-2001
Authors: Manchester R. N. , Gaensler B. M. , Wheaton V. C. , Staveley-Smith L. , Tzioumis A. K. , Bizunok N. S. , Kesteven M. J. , Reynolds J. E.
Published: September 2002

The development of the radio remnant of SN 1987A has been followed using the Australia Telescope Compact Array since its first detection in 1990 August. The remnant has been observed at four frequencies, 1.4, 2.4, 4.8, and 8.6 GHz, at intervals of 4–6 weeks since the first detection. These data are combined with the 843 MHz data set of Ball et al. (2001) obtained at Molonglo Observatory to study the spectral and temporal variations of the emission. These observations show that the remnant continues to increase in brightness, with a larger rate of increase at recent times. They also show that the radio spectrum is becoming flatter, with the spectral index changing from −0.97 to −0.88 over the 11 years. In addition, at roughly yearly intervals since 1992, the remnant has been imaged at 9 GHz using super-resolution techniques to obtain an effective synthesised beamwidth of about 0″.5. The imaging observations confirm the shell morphology of the radio remnant and show that it continues to expand at ˜3000 km s−1. The bright regions of radio emission seen on the limb of the shell do not appear to be related to the optical hot spots which have subsequently appeared in surrounding circumstellar material.
The Source Energy Spectrum of Cosmic Rays
Authors: Clay R. W.
Published: September 2002

An examination is made of the relationship between the observed energy spectrum of cosmic rays and the averaged spectrum of the cosmic rays at their sources. These spectra differ greatly, due to propagation effects. A form of the source spectrum is deduced which is a rather featureless power law over the full range of observations from 1010 eV to 1020 eV. We suggest that this lack of features is indicative of a common source for all cosmic rays over the full energy range, as opposed to lower energy Galactic and higher energy intergalactic components such as is often suggested.
The Structure of Accretion Flow at the Base of Jets in AGN
Authors: Donea Alina-C. , Biermann Peter L.
Published: September 2002

This paper discusses the boundary layer and the emission spectrum from an accretion disk having a jet anchored at its inner radius, close to the black hole. We summarise our earlier work and apply it to the accretion disks of some blazars. We suggest that the ‘accretion disk with jet’ (ADJ) model could make the bridge between standard accretion disk models (suitable for quasars and FRiisources) and low-power advection dominated accretion disk models (suitable for some of the low-power BL Lacs and FRisources).

The jet is collimated within a very narrow region close to the black hole (nozzle). In our model it is assumed that the boundary layer of the disk is the region between radius Rms— the last marginally stable circular orbit calculated for a Kerr geometry — and the radius Rjet, which gives the thickness of the ‘footring’, i.e. the base of the jet. We analyse the size of the boundary layer of the disk where the jet is fed with energy, mass, and angular momentum. As a consequence of the angular momentum extraction, the accretion disk beyond Rjetno longer has a Keplerian flow. A hot corona usually surrounds the disk, and entrainment of the corona along the flow could also be important for the energy and mass budget of the jet.

We assume that the gravitational energy available at the footring of the jet goes into the jet, and so the spectrum from the accretion disk gives a total luminosity smaller than that of a ‘standard’ accretion disk, and our ADJ model should apply for blazars with low central luminosities. Variations of the boundary layer and nozzle may account for some of the variability observed in active galactic nuclei.
AGN Variability from the USNO Radio Reference Frame Image Database
Authors: Fey Alan L.
Published: September 2002

We present results from preliminary analysis of radio interferometric data taken from the US Naval Observatory Radio Reference Frame Image Database. The results presented here reveal valuable insight into the structural variability of the two extragalactic radio sources 0552+398 and 1308+326. We are actively pursuing analysis of additional objects.
Near Infrared Micro-variability of Radio-loud Quasars
Authors: Whiting Matthew , Oshlack Alicia , Webster Rachel
Published: September 2002

We observed three AGN from the Parkes Half-Jansky Flat-spectrum Sample at near infrared (NIR) wavelengths to search for micro-variability. In one source, the blue quasar PKS 2243–123, good evidence for NIR micro-variability was found. In the other two sources, PKS 2240–260 and PKS 2233–148, both BL Lacertae objects, no such evidence of variability was detected. We discuss the implications of these observations for the various mechanisms that have been proposed for micro-variability.
Intraday Optical Variability of S5 0716+714
Authors: Nesci Roberto , Massaro Enrico , Montagni Franco
Published: September 2002

We present an optical intraday variability (IDV) study of S5 0716+714 carried out over 52 nights. The source showed detectable variations (>0.05 mag) in 80% of the nights. Typical variation rates of 0.02 mag/hour have been found to last on average 4 hours, with the average rising rate faster than the decreasing one. A maximum rising rate of 0.16 mag/hour has been observed. If the luminosity variation is due to jittering in the jet direction, a comoving dθ/dt rate of ∼100 arcsec/hour is required, assuming for the jet θ ∼ 7° and Γ ∼ 14.
The 2001 Australian Galaxy Cluster Workshop
Authors: Drinkwater Michael J.
Published: September 2002

The first ‘Australian Cluster Workshop’ was held at the Australia Telescope National Facility in Sydney on 2001 February 6. The aim of the workshop was to bring together the many and varied groups working on clusters of galaxies in Australia, to forge new multi-disciplinary links, and to generate enthusiasm and support for new cluster work and further cluster meetings in Australia. In this paper I present a summary of the workshop as well as some additional review material intended to place current Australian research in a broader perspective, looking ahead to the major issues still to be addressed.
Variability of Water Megamasers in AGN
Authors: Maloney Philip
Published: September 2002

Powerful water masers have been detected in 23 active galactic nuclei (AGN) to date. Most of the sources that have been monitored show evidence for variability, which may be either intrinsic (response of the masers to a time-varying pump or background source) or extrinsic (the effects of scintillation in the interstellar medium of the Galaxy). I briefly review the examples in which these mechanisms may be operating (interstellar scintillation in the Circinus galaxy, a time-varying background source in Mrk 348, and a time-varying AGN luminosity in NGC 1068).
The Parsec-scale Jets of Extragalactic TeV Gamma-ray Sources
Authors: Piner B. G. , Edwards P. G. , Fodor S. , Rector T. A.
Published: September 2002

We present results of VLBI monitoring observations of the blazars detected by ground-based TeV gamma-ray telescopes. Preliminary results have shown that the apparent speeds of the parsec-scale jet features in these sources are predominantly subluminal, and significantly slower than those in the GeV-peaked (EGRET) gamma-ray blazars. Here we add results from additional sources and additional epochs that increase the statistical significance of this comparison. These slower speeds may indicate rapid deceleration of the jets in TeV blazars between the TeV gamma-ray emitting scales and VLBI scales.
Interstellar Scintillation Explains the Intraday Variations in the Linear Polarisation of Quasar PKS 0405-385 at cm-wavelengths
Authors: Rickett Barney , Kedziora-Chudczer Lucyna , Jauncey David L.
Published: September 2002

During its burst of intraday variation (IDV) in June 1996 quasar PKS 0405–385 exhibited rapid changes in the Stokes parameters Q and U that were even faster than the 1 hr timescale changes in I. Auto- and cross-correlation analyses of I,Q, and U at 8.6 GHz show systematic relations between the variations in I,Q, and U. These are well modelled by interstellar scintillation (ISS) of a 14 × 20 μ as source, with about 180 degree rotation of the polarisation angle along its long dimension. This success in explaining the remarkable IDV in polarisation confirms that ISS gives rise to the IDV in this quasar.
Molecular Hydrogen in the Lagoon: H2 Line Emission from Messier 8
Authors: Burton Michael G.
Published: September 2002

The 2.12 μm v = 1−0 S(1) line of molecular hydrogen has been imaged in the Hourglass region of M8. The line is emitted from a roughly bipolar region, centred around the O7 star Herschel 36. The peak H2 1−0 S(1) line intensity is 8.2 × 10−15 erg s−1 cm−2arcsec−2. The line centre emission velocity varies from −25 kms−1 in the SE lobe to +45 kms−1 in the NW lobe. The distribution is similar to that of the CO J = 3−2 line. The H2 line appears to be shock-excited when a bipolar outflow from Herschel 36 interacts with the ambient molecular cloud. The total luminosity of all H2 lines is estimated to be ˜16 L⊙ and the mass of the hot molecular gas ˜9 × 10−4 M⊙ (without any correction for extinction).
AAT/WFI Observations of the Extragalactic HI Cloud HIPASS J1712-64
Authors: Lewis Geraint F. , Irwin Michael J. , Ibata Rodrigo A. , Gibson Brad K.
Published: September 2002

AAT/WFI optical images of a candidate extragalactic HI cloud, HIPASS J1712–64, are presented. The g and r band CCD mosaic camera frames were processed using a new data pipeline recently installed at the AAO. The resultant stacked images reach significantly deeper levels than those of previous published optical imaging of this candidate, providing a detection limit Mg ˜ −7 at a distance of 3 Mpc, the inferred distance to HIPASS J1712–64. However, detailed analysis of the images fails to uncover any stellar population associated with the HI emission. If this system is a member of the Local Group then it is pathologically different to other members. Hence, our observations reinforce earlier suggestions that this HI cloud is most likely Galactic in origin and not a Local Volume dwarf galaxy.
Reversion of floral development under adverse ecological conditions in Whytockia bijieensis (Gesneriaceae)
Authors: Wang Y. Z.
Published: September 2002

The reversion of floral development in
Whytockia bijieensis Y.Z.Wang et Z.Y.Li occurs after the
normal initiation of mid-adaxial sepals, which implies that the floral organs
are not determined at the initiation of the floral primordium, but
progressively determined during its development. Both low humidity (less than
75%) and low night temperature (12–14˚C) contribute to the
reversion of floral development. However, the low humidity or low night
temperature alone do not greatly affect the normal flowering process. The
combination of these two ecological factors seems to considerably disturb the
normal flowering process, greatly strengthening the reversion process of
flowering. High humidity and moderate temperature or at least one of the two
are necessary for the normal flowering process of
W. bijieensis. It is likely that low humidity and low
night temperature trigger the reversal to vegetative growth during floral
development. The change of a flower into a bract-like organ in the flower
pairs indicates that a transition from pair-flowered to normal cymes is
possible.
Fates of fruits and seeds of Ligustrum lucidum W.T.Ait. and L. sinense Lour. maintained under natural rainfall or irrigation
Authors: Panetta F. D.
Published: September 2002

Factors influencing germination and seed survival of
Ligustrum lucidum W.T.Ait. and
L. sinense Lour., two serious environmental weeds in
subcoastal eastern Australia, were investigated in a series of experiments
conducted under natural rainfall regimes (field experiments) and under
irrigation in a growth tunnel. In the field experiments, no seedlings of
either species were observed where seeds and intact fruits had been
surface-sown; seedlings originated only from shallowly buried seeds and
fruits, with generally higher levels of emergence from seeds. Where soil
moisture levels were maintained at or above field capacity, however, moderate
to high levels of germination occurred from surface-sown seeds and fruits of
both species. Total seedling emergence varied considerably between years for
each moisture regime. Seeds of both species were short-lived, with most
(>95%) not persisting for 12 months in any case.
Effects of temperature, light and stratification on seed germination of Wollemi pine (Wollemia nobilis, Araucariaceae)
Authors: Offord C. A. , Meagher P. F.
Published: September 2002

Wollemia nobilis W.G.Jones, K.D.Hill D J.M.Allen isrepresented in the wild by about 40 adult trees; therefore, understanding therequirements for seed germination is important for the conservation of thismonotypic Australian conifer. Constant-temperature experiments found that seedgermination proceeded most rapidly at temperatures between 24 and 30˚C.Few seeds germinated when incubated for 112 days at 10 and 16˚C but latergerminated when transferred to 24˚C, whereas seeds initially incubated at35˚C were killed. Unstratified seeds showed a pattern of prolongedgermination taking 130 days to achieve 40% germination at 24˚C and40 days at 27˚C. Seeds stratified at 6˚C for 14 days and incubatedat 27˚C in the light achieved 40% germination within 20 days whilethose incubated at 10 and 16˚C for 112 days and transferred to 24˚Cachieved 40% germination by 15 and 24 days, respectively. Initialgermination of unstratified seeds was fastest when incubated at 30˚C inthe light, averaging 23 days. Exposure to 12-h diurnal periods of 10–15mol m–2 s–1 lightsignificantly increased 28-dayincubation germination percentages, but for onlythose incubated at 30˚C. Additions of gibberellic acid(GA3) at 1 mM had no effect on seed germination ofW. nobilis. The field observations and laboratoryexperiments indicate that following seed shed in summer and early autumn whentemperatures are high, W. nobilis seeds germinate,especially if exposed to light. The seeds that remain ungerminated or that areshed late in the season survive over winter, but germinate rapidly oncetemperatures rise in the next spring.