bluuebunny/crossref_metadata_2025 huggingface dataset:
Resistance to root-lesion nematode (Pratylenchus thornei) in Aegilops tauschii Coss., the D-genome donor to wheat
Authors: Thompson J. P. , Haak M. I.
Published: August 2004

Root-lesion nematode (Pratylenchus thornei Sher and
Allen) causes substantial loss in yield of wheat in eastern Australia. Central
Asian accessions of Aegilops tauschii Coss. were tested
to find new sources of resistance to P. thornei for use
in wheat-breeding programs. Ae. tauschii (2n =
14, DD genome) is one of the wild progenitors of wheat,
Triticum aestivum L. (2n = 42, AABBDD genomes).
Resistance was determined by nematode reproduction in the plant roots during
16 weeks of growth in pots in a glasshouse. Thirty-nine of 244 accessions of
Ae. tauschii tested in 2 replicated experiments had
lower numbers of nematodes than GS50a, a partially resistant line of wheat
used as a resistance standard. Resistance to P. thornei
was present in accessions of most taxonomic groups within
Ae. tauschii, i.e. Ae. tauschii
subsp. strangulata (Eig) Tzvel., and
Ae. tauschii subsp. tauschii var.
typica L. and var. meyeri
(Griseb.) Tzvel. Resistance was most common in subsp.
strangulata with 20 out of 40
strangulata accessions in the resistant group and none
in a highly susceptible group of 43 accessions. Accessions of var. meyeri with
the Cre3 gene for effective resistance to cereal cyst
nematode (Heterodera avenae Woll.) were also resistant
to P. thornei. The results indicate that several
resistances to P. thornei are present in
Ae. tauschii subspecies and varieties, which could be
introgressed into cultivated wheat to help control
P. thornei and increase farm profits.
Effect of Chromium Chelavite supplementation on the metabolism of glycogen and lipid in adult Merino sheep
Authors: Gardner G. E. , Smith G. , Pethick D. W.
Published: August 2004

This experiment investigated the effect of exercise and chromium
supplementation on muscle glycogen and subcutaneous fat metabolism. The design
of the experiment was a 2×2 factorial with chromium and regular exercise
as the treatments. Forty-three Merino wethers (2 years old) were maintained
for 10 weeks on a diet based on barley and lupin grain fed at 2·2 times
maintenance. The ration was supplemented with 0 or 1 mg/kg DM of chromium,
as Chromium Chelavite amino acid chelate. For regular exercise the animals
were worked at approximately 60% maximum whole body oxygen consumption
for 2 h, 3 times per week, which increased the estimated weekly energy demand
by about 9%.
Chromium increased the activity ofATP citrate lyase, a
marker of the glucose-insulin axis, by 30%, but decreased the fat depth
GR, the fat depth over the 12th rib, by 20%. There was no effect on the
activity of acetyl CoA carboxylase, the major rate-limiting enzyme of
lipogenesis. Thus the potential for glucose contribution to fat synthesis
increased but the subcutaneous fat depth decreased, indicating that chromium
may cause the redistribution of fat within the carcass due to changes in
insulin sensitivity. The chromium treatment did not effect growth rate,
carcass weight, or muscle glycogen concentration. Chromium supplementation
tended to prevent a decline in the concentration of chromium in the kidney,
caused by exercise. The level of exercise was only sufficient to cause a
glycogen loading response in one of the muscle tissues sampled, the
m. semimembranosis. Chromium Chelavite supplementation
may be a useful tool for reducing the subcutaneous fat depth of mature
ruminants, and may promote the redistribution of fat to other locations within
the carcass.
Variability and trends in sowing dates across the Australian wheatbelt
Authors: Stephens D. J. , Lyons T. J.
Published: August 2004

As sowing dates are critical for appropriate yield forecasting, a national
survey of Australian wheat farmers was undertaken. This revealed that wheat
sowing generally takes 2-4 weeks to complete between the middle of May and the
middle of June. Distinct regional differences occur in the way sowing is
completed and these are related to soil and climatic effects. In Western
Australia, sowing follows a more distinct `break in the season" and
the midpoint of farm sowing is fairly uniform across cropping areas. As one
progresses into south-eastern and then north-eastern cropping areas the
spatial variability in sowing increases. The combination of fallowing
practices, unreliable autumn rainfall, and heavier soils (that delay
operations when conditions are wet or dry), all add to the variability in
sowing date and sowing duration in north-eastern areas. The range of midpoint
in sowing (between years) generally decreases as the progression is made from
a farm, to a State, to a national scale. Reduced variability at a national
scale is enhanced by broad-scale weather patterns causing sowing opportunities
to contrast markedly on different sides of the country. During the 1980s,
sowing progressed a day earlier per year at a national scale. The most
pronounced changes occurred in Queensland and Western Australia, where a
2-3-week shift to earlier sowing was recorded. Coinciding with this was a
trend in all areas to reduced or minimum tillage techniques. Late opening
rains in South Australia restricted early sowing opportunities during this
time.
Alternaria toxins in weather-damaged wheat and sorghum in the 1995-1996 Australian harvest
Authors: Webley D. J. , Jackson K. L. , Mullins J. D. , Hocking A. D. , Pitt J. I.
Published: August 2004

Weather-damaged wheat from northern New South Wales in 1995-96 was heavily
infected with the fungus Alternaria alternata. The
mycotoxins tenuazonic acid, alternariol, and alternariol monomethyl ether were
detected at low levels which corresponded with the degree of A.
alternata infection and the geographical location.
Sorghum and undamaged wheat from the same region also showed moderate levels
of A. alternata infection and low levels of tenuazonic
acid but none of the other toxins. These mycotoxins were not found in
weather-damaged wheat from other areas of Australia where the primary
infection was by A. infectoria rather than
A. alternata.
Occurrence and identity of Puccinia graminis on wheat, barley, andgrasses in Australia during summer - autumn 1992-93
Authors: Park R. F.
Published: August 2004

Levels of stem rust (Puccinia graminis) in Australian
wheat and barley crops were generally low from 1980 to 1992. Exceptionally wet
conditions in South Australia (SA) during early summer 1992-93 resulted in the
establishment of vast areas of self-sown cereals, in which stem rust increased
rapidly. The disease was also more common in Western Australia during the
summer months of 1992-93. Collections from rusted wheat, barley, and selected
grass species were analysed in greenhouse tests using an array of differential
cereal genotypes. Five pathotypes of P. graminis f. sp.
tritici were recovered from SA, 3 of which had not been isolated over the
previous 10 years in Australia and for up to 20 years in SA. The recurrence of
these pathotypes highlights the need for caution in redeploying resistance
genes for which virulence has not been detected for several years. The
majority (79%) of isolates taken from stem-rusted barley in SA were
either P. graminis f. sp. secalis or
`scabrum" rust, both of which do not infect wheat. In total, 6 of 7
isolates of pathotype 21-2,7 recovered from SA came from stem-rusted barley,
and as most wheats in this region are resistant to this pathotype, it appears
that hosts other than wheat must be important in perpetuating such avirulent
pathotypes.
Sugarcane fields: sources or sinks for greenhouse gas emissions?
Authors: Weier K. L.
Published: August 2004

The quantities of greenhouse gases emitted into the atmosphere from sugarcane
fields, and their contribution to the total emissions from Australian
agriculture, have never been estimated with any degree of certainty. This
review was conducted to collate the available information on greenhouse gas
emissions from the Australian sugarcane crop. Estimates were made for the
emissions of the 3 major greenhouse gases―carbon dioxide
(CO2), methane (CH4), and nitrous
oxide (N2O)―from known or suspected sources.
Sinks for the sequestration of the gases also have been identified.
CO2 was found to be emitted during burning of the crop
and from trash-blanketed and bare sugarcane fields. Total emissions from these
sources in the 1994 season were estimated at 7·6 Mt
CO2-C/year. However, the sugarcane crop was
identified as a major sink for C, with uptake by the crop in 1994 estimated at
13· 4 Mt CO2-C/year.
N2O emanating from sugarcane soils via denitrification
following application of fertiliser accounted for 45-78% of total
gaseous N emissions. Estimates of N2O emissions from all
land under sugarcane in 1994 totalled 4·4 kt
N2O-N/year from denitrification with a further
6·3 kt N2O-N emitted from areas that are still
burnt. This review suggests changes in management procedures that should limit
the opportunities for denitrification in the soil and thus reduce
N2O emissions. Methane evolution occurs during the
smouldering phase, following burning of the crop, with production estimated at
6·7 kt CH4-C/year in 1994.
CH4 oxidation in soil was identified as an important
process for removal of atmospheric CH4, as were
trash-blanketed soils. Although these figures are our best estimate of gaseous
production from sugarcane fields, there still remains a degree of uncertainty
due to sampling variability and because of the extrapolation to the entire
sugarcane area. However, the coupling of new laser techniques with known
micrometeorological methods will allow for a more precise sampling of
greenhouse gas emissions over a larger area. Estimates would thus be more
representative, resulting in a greater degree of confidence being placed in
them by the sugar industry.
Weed control with atrazine and chlorsulfuron is determined by herbicide availability and persistence in soils
Authors: Walker S. R. , Robinson G. R. , Hargreaves P. A.
Published: August 2004

Effectiveness and length of weed control with atrazine and chlorsulfuron can
be variable in the field. While some of this may be due to climatic
variations, differences in soil properties may also be important. We tested
this by recording changes in control of mintweed
(Salvia reflexa Hornem.) and turnip weed
(Rapistrum rugosum L.) with time in different soils, and
comparing these results with the measured changes in plant-available herbicide
in the soils. Length of weed control with the same herbicide rate varied from
0 to >15 weeks. Mintweed and turnip weed were controlled (85-100%)
only when the soils had ¸ 0·1µ#9839;g
available atrazine/g and 0·8 ng available chlorsulfuron/g,
respectively. This agreed with the sensitivity data for these weeds when grown
in a soil-free system. The herbicides were initially more available in grey
clays than in black earths, and soil pH accounted for most of the variations
in the persistence of the available residues. Thus, the efficacy of these
herbicides in different soils could be estimated if the available residues in
the root-zone could be predicted and the sensitivity of different weeds was
known.
A simplification of the deuterium oxide dilution technique using FT-IR analysis of plasma, for estimating piglet milk intake
Authors: Glencross Brett D. , Mullan Bruce P. , Tuckey Robert C. , Hartmann Peter E.
Published: August 2004

Previous studies estimating milk intake using deuterium oxide
(D2O) as a tracer have required sublimation of the
sample fluid (usually plasma) to remove solids and retrieve total water. This
procedure has been simplified by directly measuring the
D2O content of plasma with a Fourier transform-infrared
(FT-IR) spectrometer, removing the requirement for sample sublimation.
Comparisons of samples that were split and then analysed as water of
sublimation and as total plasma were performed. It was found that the direct
analysis of the plasma could be achieved without a loss in fidelity of the
results (sublimated v. plasma,
r2 =
0·976;n = 26). Linearity of assay
standards was very high (r2 >
0·997). The modified technique was used to determine the milk intake by
piglets from litters of 7 sows during established lactation (Days 10-15).
Water turnover (WTO) was shown to be the primary point by which differences in
the piglet milk intakes were influenced. Differences in the milk composition
had minimal effect on the milk intake determinations. Milk intake by each
piglet was shown to be strongly correlated to piglet growth
(r2 = 0·59,
P < 0·01). The relationship between milk
intake and piglet growth was even stronger when examined based on the data
from all piglet litters (r2
= 0·84, P < 0·01).
Transient high temperatures during seed growth in narrow-leafed lupin (Lupinus angustifolius L.) I. High temperatures reduce seed weight
Authors: Reader M. A. , Dracup M. , Atkins C. A.
Published: August 2004

Highly variable yields are a weakness of narrow-leafed lupins. Yield
variability could be caused by many factors, including hot days during seed
filling. This paper investigates the effects of 2 hot days at various stages
of seed filling in L. angustifoliusL. cv. Merrit. Exposing adequately watered
plants to a total of 6 h at 34, 36, or 38˚C, compared with 20˚C,
over 2 consecutive days reduced weight per seed by 4, 8, or 12% at
maturity, respectively. The 38˚C treatment, applied when seeds averaged
4% of their final weight, also caused significant seed abortion. High
temperatures reduced weight per seed at all stages of seed growth, except when
seeds were <5-12 mg dry weight (3 and 6% of final seed dry weight,
Expts 1 and 2, respectively). The reductions in weight per seed were not
associated with reduced assimilate supply because: (a)
neither photosynthesis nor leaf longevity were reduced by heat treatment;
(b) competing inflorescences and branches were not
allowed to develop; (c) the plants produced very large
seeds for this cultivar (174-190 mg); and (d) leaves
remained green well after the pods had matured. Seed N concentration decreased
and fat concentration increased by small, although statistically significant,
amounts in response to heat treatment at the last stage of seed development
tested (57% of final weight per seed when treated) but not at earlier
stages. This study indicates that hot days with pod temperatures as low as
34-36˚C during seed development can cause reductions in weight per seed,
and hence yields, in narrow-leafed lupin crops.
Field amelioration of acidic soils in south-east Queensland. II. Effect of amendments on the yield and leaf nutrient composition of maize
Authors: Dickson T. , Moody P. W. , Aitken R. L.
Published: August 2004

The yield of maize, grown on acidic soils with various rates of lime, was
measured inreplicated field trials at each of 19 sites in south-east
Queensland. Treatments comprising single rates of gypsum, phosphogypsum, and
calcium silicate (as Portland cement) were incorporated into the trialde sign
at selected sites. At 12 of the sites, lime significantly
(P < 0·05) increased grain yield. Because Ca
was applied as a basal nutrient the lime responses were attributed mainly to
the amelioration of Aland/or Mn toxicities and this was supported by the
observation that 90% maximum yield was attainedat
pHw values of around 5·0-5·5. Soil
pHw values of around 5·5 would appear to be
adequate for optimal maize growth in the region and there was little evidence
to support liming to higher pH values.
High lime rates resulted in significant (P <
0·05) grain yield reduction relative to the maximum yield at 3 sites
with concomitant soil pHw values of 6·7,
7·1, and 7·2, but leaf analysis did not provide a conclusive
explanation for the yield reductions.
Lime significantly (P < 0·05) increased leaf
tissue P concentrations at 6 sites, whereas Zn and Mn concentrations were
decreased at 7 and 10 sites, respectively. Across all sites, there were no
consistent trends with respect to the effect of lime on N, K, S, and Mg
concentrations.
Although gypsum and/or phosphogypsum increased grain yield at 3 sites,
there was little evidence that amendments other than lime or dolomite type
products would have widespread potential for ameliorating soils where Al
and/or Mn toxicities are limiting crop growth in the region.
Composition of liquid-and particle-associated bacteria and their contribution to the rumen outflow
Authors: Pérez J. F. , Fondevila M. , Balcells J. , Guada J. A.
Published: August 2004

A method is described to estimate the composition and rumen outflow of
microbes associated with liquid (LAB) and solid (SAB) digesta. Four
rumen-cannulated Rasa Aragonesa ewes were given, in random order, the
following 4 diets: (1) NaOH-treated barley straw, as a
sole diet (700 g/day, TS); (2) NaOH-treated barley
straw mixed (50 : 50) with 400 g/day of rolled barley grain (BS);
(3) Diet 1 with addition of 8 g/day of urea; and
(4) Diet 2 with addition of 16 g/day of urea.
Co-EDTA was used as a marker for the liquid phase to estimate rumen outflow of
liquid-associated purine bases (PB), and urinary purine derivatives were used
as an indirect marker of total duodenal flow of PB. Solid-associated PB were
calculated by the difference between both estimates. Urea infusion increased
ammonia-N concentration in the rumen fluid from 4·8 to 15·9
mg/100 mL (P < 0· 05) and enhanced dry
matter intake of TS diets (from 343±63· 5 to
556±41·2 g/day, P < 0·001).
Significant differences were observed in the PB/N ratio of bacteria
harvested from the liquid phase compared with that isolated from the solid
phase (1·89±0·25 v. 1·66±0·32
mol/mg in LAB and SAB, respectively). Because of the differences observed
between the liquid- and solid-associated bacteria, estimated values of
bacterial N supply varied depending on which bacterial extract was used as
reference. The fractional contribution of LAB and SAB to the postruminal
bacteria was significantly influenced by the experimental diets, mainly
through variations in the amount of LAB flowing out of the rumen.
Production and glutathione responses to rumen-protected methionine in young sheep grazing dry pastures over summer and autumn
Authors: Mata G. , Masters D. G. , Chamberlain N. L. , Young P.
Published: August 2004

The aims of the experiment were to evaluate, in weaner sheep grazing dry
annual pastures, the production responses and changes in blood and tissue
glutathione concentrations to a methionine formulation (Lactet) protected from
microbial breakdown in the rumen. Two groups of 60 weaner wether sheep,
weighing 32·8 kg, were supplemented with lupin grain containing either
nil (control) or 9 g Lactet per day. Lactet provided 3 g of protected
methionine per day. The sheep grazed dry pastures and were rotated through 2
plots every week from December to June. After June the treatment ceased and
the sheep grazed as one group until shearing in September.
The sheep given Lactet grew 340 g more clean wool with a greater fibre
diameter (1·2 µm) than the control sheep. Lactet supplementation
increased liveweights during treatment and for 3 months following treatment.
Faecal dry matter output was significantly increased by Lactet supplements and
the effects were maintained in the post-treatment period, indicating that
Lactet supplementation increased dry matter intake.
Glutathione concentrations were significantly increased in whole blood, liver,
and muscle but not in skin. Changes due to season were greater than changes
due to treatment. It was concluded that glutathione in blood or tissues,
although responsive at times, was not a reliable indicator of sulfur amino
acid intake or status. Significant increases in total body water, protein,
ash, fat, and total body energy were observed relative to the control group
following Lactet supplementation.
We conclude that young sheep grazing dry annual pastures in summer and autumn
have the potential to respond to supplements of rumen-protected methionine
even at low energy intakes from low quality pastures and show improvements in
wool quality and quantity as well as liveweight and intake.
Season, nitrogen rate, and plant type affect nitrogen uptake and nitrogen use efficiency in rice
Authors: Borrell A. K. , Garside A. L. , Fukai S. , Reid D. J.
Published: August 2004

Studies were undertaken in the Burdekin River Irrigation Area of northern
Australia to improve the efficiency of nitrogen (N) use for rice
(Oryza sativa L.) production. The aim was to maximise
grain yield by optimising its functional components: N uptake, efficiency of N
use for dry matter production (NUEdm), and harvest index
(HI). The effiects of season (wet and dry), N rate (0, 70, 140, 210, and 280
kg/ha), and plant type (maturity and stature) on N uptake,
NUEdm, and HI were examined in 2 wet and 2 dry seasons.
Leaf area development was closely related to N uptake. In the wet season,
genotypes had similar rates of increase in leaf area index (LAI) with N uptake
but differed in the level of LAI (curves were parallel).
In the dry season, the relationship between N uptake and LAI was different for
each genotype (curves not parallel). In both seasons cv.
Newbonnet generally had a lower LAI per unit N uptake (i.e. leaf area
production was not excessive) than cvv. Lemont and Starbonnet. Dry matter
production and grain yield were also closely related to N uptake. At low
levels of N availability (N uptake <100 kg/ha) tissue N concentrations
were low and both total above-ground dry mass (AGDM) and grain yield were
linearly related to N uptake. As N availability increased, N uptake and tissue
N concentration increased, resulting in a deviation of the AGDM and grain
yield curves from the linear at about 100 kg/haN uptake. This finally
resulted in AGDM and grain yield plateauing at around 200 kg/ha N uptake.
Above this level some factors other than N availability limited yield.
Seasonal differences in N uptake, NUEdm, and HI were
observed. Seasonal variation in the response of grain yield to N uptake was
found. There was a trend for higher N uptake in the absence of fertiliser
application in the wet than the dry season, and the recovery fraction was less
for N rates >140 kg/ha in all seasons, i.e. fertiliser N uptake
efficiency declined with increasing N rate. Nitrogen was used more effectively
by the rice crop to produce grain compared with non-grain parts when average
daily mean temperatures were lower during the period between panicle
initiation and anthesis.
Genotypic variation was found in N uptake, NUEdm, and
HI. The ability to capture these components in crop improvement programs
depends on the extent to which genetic linkages between N uptake and both
NUEdm and HI can be broken. While our data suggest that
N uptake is generally negatively correlated with both
NUEdm and HI, there is some evidence that these linkages
can be broken. For example, the fact that HIdid not change with increasing N
uptake in Lemont and, to a lesser extent, in Newbonnet suggests that HI does
not always decline with increasing N uptake. The example of Newbonnet suggests
that, to some extent, it is possible to increase yield by increasing each of
the functional components independently within a specific genotype.
The action of ethanol in controlling superficial scald of apples
Authors: Ghahramani Farhad , Scott Kevin J.
Published: August 2004

Studies over 3 seasons with Granny Smith apples suggest that ethanol vapour
controls superficial scald by reducing the production of α-farnesene and
preventing its breakdown to conjugated trienes. Ethanol at the rate of
0·35-5·6 g/kg apples was placed in dishes together with 10
or 20 fruit in polyethylene bags (thickness 50 µm). The bags were sealed
and stored at 0º C for 16-36 weeks. The polyethylene bags were found to
be permeable to ethanol vapour. The levels of ethanol in the headspace of bag
for maximum application rate was 11 mg/L with fruit and 86 mg/L
without fruit. The maximum level in the juice for this treatment was 4.7
mg/mL. The above concentrations occurred early in storage and fell later.
The concentrations of α-farnesene and conjugated trienes rose in the
untreated apples but remained at low levels in the treated apples. There were
close and highly significant inverse relationships between the concentration
of ethanol in the juice and scald. The severity of scald was directly related
to the concentrations of α-farnesene and conjugated trienes in the skin.
After 4 months of storage at 0º C the ff-farnesene content of untreated
fruit declined during a 2-week period at 20º C and conjugated trienes
increased during this period. Fruit treated with higher amounts of ethanol
(2·8 or 5·6 g/kg fruit) at the beginning of storage
continued to accumulate α-farnesene during the post storage period at
20º C but conjugated trienes did not increase.
Sensitive detection of pea seed borne mosaic potyvirus by dot blot and tissue print hybridisation assays
Authors: Ali Akhtar , Hodgson R. A. J. , Randles J. W.
Published: August 2004

Dot blot and tissue print hybridisation assays were developed for the rapid
and sensitive detection of pea seed borne mosaic virus (PSbMV). Radioactive
(32P-labelled) and non-radioactive (DIG-labelled)
random primed cDNA probes representing the entire genome of PSbMV were used in
hybridisation assays. A comparison of detection sensitivity was made between
these probes and they were found equally sensitive. PSbMV was readily detected
in dot blots by their homologous cDNA probes to 50 fg in purified preparations
and to a 1 : 3125 dilution in purfied total nucleic acid or crude sap from
infected plants. The sensitivity of heterologous probes was significantly less
than that of homologous probes in purified preparation but nearly the same in
purified total nucleic acid or crude sap from infected plants. The virus was
also specifically detected in tissue squashes by tissue print hybridisation
using cDNA probes. Non-radioactive probes were found suitable for PSbMV
diagnosis without significant loss of detection sensitivity. There was no
non-specific hybridisation against the healthy control in hybridisation assays
using either radioactive or non-radioactive probes.
Feed intake, digestion, and renal function in Merino sheep selected for higher clean fleece weight
Authors: Faichney G. J. , Welch R. J. , Brown G. H.
Published: August 2004

Two-year-old ewes from 2 Merino lines selected for higher clean fleece weight
were compared with their control line when given a lucerne hay diet and a
lower quality diet of mixed wheaten and lucerne hays. There were no
differences between lines in voluntary feed consumption, feed digestibility,
urea synthesis and excretion, or renal function. Voluntary feed consumption,
digestibility, urea synthesis and excretion, glomerular filtration rate, and
urea and creatinine clearances were higher on the higher quality lucerne hay
diet; renal tubular function was not affected by diet. Water intake was higher
in the selection lines; consequently, these sheep produced more of a less
concentrated urine. The renal clearance of endogenous true creatinine was
significantly greater than the glomerular filtration rate, indicating that
creatinine was secreted in the kidney tubules. The results support the
conclusion that differences between selection lines in physiological
parameters not directly associated with wool follicle function are unlikely to
be consistent enough to be useful predictors of genetic merit for fleece
weight.
An interpretative model of carbon and nitrogentransformations applied to a residue incubation experiment
Authors: Trenbath B. R. , Diggle A. J.
Published: August 2004

A simple model of 3 equations was devised to simulate the rates through time
of gross mineralisation of nitrogen, nitrogen immobilisation, and microbial
respiration relating to individual inputs into soil of plant residues of any
age or type. Using published data from an incubation experiment carried out in
Iowa, we applied the model to a residue newly added to soil, to the
original soil organic matter (SOM), and to a mixture of these.
Manipulation of the model allowed the derivation from the Iowa data of a net
mineralisation index which seemed to summarise the nitrogen release
characteristics of the residue in all treatments of the experiment.
The equations and parameter values developed for the added residue were
applied to SOM using results from unamended soil. The balance between
respiration and mineralisation was found not to correspond to that expected for
old organic matter near an equilibrium carbon/nitrogen ratio.
Rate constants of mineralisation and respiration for SOM were adapted to
overcome this apparent anomaly.
To model the dynamics SOM and added residue simultaneously, the 2 sets of 3
equations were applied in parallel to 4 extreme treatments in the with-residue
series (lowest and highest nitrate levels with low and high residue
additions). To achieve the fits presented, only 2 of the 12 parameters required
in each set of equations needed to differ between the set for SOM and that for
added residue.
The model reproduces well most of the primary Iowa data and also some derived
results. Use of the model helped to interpret divergences between simulations
and data.
Blood lactose v. milk lactose as a monitorof lactogenesis and colostrum production in Merino ewes
Authors: McNeill D. M. , Murphy P. M. , Lindsay D. R.
Published: August 2004

The pattern of onset of lactation and colostrum production was compared in 42
single-and twin-bearing Merino ewes of 2 genotypes, Australian Merino Society
(AMS) or Meridale (AMS with an infusion of British Breeds). The onset of
lactation was indicated by measuring changes in the concentration of lactose
in udder secretions (milk lactose) and in blood samples (blood lactose)
collected daily for at least 4 days prior to, and at 1, 3, 6, 12, and 24 h
after, parturition. Blood lactose was a novel alternative to milk lactose, as
blood was easier to collect than udder secretions. Colostrum production was
measured by milking the ewes at 1, 3, and 6 h after parturition.
Twin-bearing ewes initiated lactation later than single-bearing ewes, but both
groups produced similar volumes ofcolostrum to 1 h after birth (475
v. 371 mL, P > 0·05).
The rate of secretion of colostrum was similar for twin- and single-bearers in
the interval 1-6 h after birth (82 v. 79 mL/h,
P > 0·05). Meridale Merinos secreted colostrum
at a faster rate than the AMS Merinos at 1-6 h post-partum (94
v.67 mL/h, P <
0·05), but had similar accumulations of colostrum to the AMS Merinos
before birth. Five percent of ewes had no colostrum available 1 h after birth.
The concentration of blood lactose reflected changes in milk lactose prior to,
but not after, the first few hours post-partum. Blood lactose concentration
measured prior to birth was related to the volume of colostrum that had
accumulated in the udder up to 1 h after birth (r
= 0·60, P < 0·001), but milk
lactose measured at the sametime was not related to the accumulation of
colostrum. Blood lactose measured before birth can beused to estimate whether
treatment groups of ewes differ in the volume of colostrum available for the
lamb at birth. This may permit us to study the relationship between lamb
survival and colostrum production in the field without disturbing the ewe-lamb
bond by milking the ewe.
Sustained growth promotion of steers, using anabolic steroids
Authors: Magner T. , Hunter R. A. , Berger K. T.
Published: August 2004

This experiment tested the hypothesis that sustained growth promotion of
steers could be achieved by alternate use of oestrogenic and androgenic
anabolic steroids. Twenty-one high grade Brahman
(Bos indicus) steers were divided into 3 groups of 7 and
allocated to 1 of the following treatments: control; implantation in the ear
with 45 mg oestradiol-17β for approximately 100 days followed by treatment
with testosterone propionate (this rotation occurred twice); implantation with
45 mg oestradiol-17β at approximately 100-day intervals. Steers were
housed in individual pens in an animal house and fed a restricted diet to
regulate their growth rate to about 0·6 kg/day over a 58-week
period. At intervals during the first 30 weeks, steers were transferred to
metabolism crates and their nitrogen retentions measured. At the end of the
experiment the steers were slaughtered and their carcass characteristics
determined.
The mean growth rates of the steers treated with 2 steroids alternately
(0·75±0·06 kg/day) and of steers treated continuously
with oestradiol-17β (0·72±0·06 kg/day) were
significantly (P = 0·01) higher than that
of control steers (0·62±0·10 kg/day). Treatment with
oestradiol-17β during the first implant period was associated with higher
(P < 0·05) nitrogen retentions in the first
weeks after implantation with attenuation of the advantage at the end of the
100-day period.
At slaughter, steers from both steroid treatment strategies were almost 60 kg
heavier (P < 0·05) than the controls, with
carcasses about 30 kg heavier. Steers treated continuously with
oestradiol-17β had significantly (P <
0·05) thicker subcutaneous fat cover at the P8 rump site (19·4
mm) than the controls (12·4 mm) or those treated during the final
period with testosterone propionate (12·3 mm). It was concluded that
sustained growth promotion of steers using anabolic steroids can be achieved.
Nitrogen and water flows under pasture - wheat and lupin - wheat rotations in deep sands in Western Australia. 1. Nitrogen fixation in legumes, net N mineralisation,and utilisation of soil-derived nitrogen
Authors: Anderson G. C. , Fillery I. R. P. , Dolling P. J. , Asseng S.
Published: August 2004

Detailed studies on the eciency with which pastures and crops use soil-derived
nitrogen (N) in southern Australia are limited. Inefficiencies in the N cycle
are indicated by wide spread soilacidification and low N status in wheat
grain. The aims of this study were to document rates of
N2 fixation by subterranean clover-based pastures and
narrow-leaf lupin, plant uptake of soil-derived N, mineralisation of organic N
during legume and cereal phases, and export of N from pastures, lupin,and
wheat in relation to climate and soil water. These measurements were
undertaken in a rotation experiment conducted on a deep sand located in the
northern wheat belt of Western Australia at a site with a long-term average
rainfall of 460 mm. The rotations examined over 3 years were 2 years
pasture-wheat and lupin-wheat.
The 15N natural abundance technique was used to
differentiate soil-derived N from atmospheric Nin legumes. Biomass production,
grain yields, and N contents were standard plant measurements in all
treatments. Net N mineralisation between growing seasons was as certained by
measuring changes in soil inorganic N to 1·5 m. Growing season net N
mineralisation was determined using an in situ method in
which soil cores were isolated from plant roots. Anion exchange resin was used
to trap NO-3 leached below the
depth of the soil cores.
Nitrogen fixation by subterranean clover in a mixed pasture ranged from 29 to
162 kg N/ha whereas N2 fixation by lupins was less
variable, ranging from 90 to 151 kg N/ha. Pastures were large consumers of
soil-derived N (range 58-154 kg N/ha), with capeweed being the most
important sink (range 38-120 kg N/ha). In comparison, wheat and lupins
were inefficient users of soil N, removing 29-51 kg N/ha within a season.
Another 31-67 kg N/ha of inorganic N in soil was not utilised by wheat or
lupin.
Annual net N mineralisation ranged from 80 to 130 kg N, confirming the high
rate of decomposition of organic matter in the sandy soil. Mineralisation over
summer and autumn, when crop and pastures were not grown, supplied ~25%
of the inorganic N produced in soil profiles in 1995 and 20-40% in1996.
The study indicated that legumes used in rotations with cereals on deep sands
were able to add adequate organic N to soil to insure rates of net N
mineralisation sufficient to support cereal yieldsin excess of current shire
averages. However, in practice, the asynchrony in supply and demand for N
resulted in the inefficient use of soil-derived N by wheat.
Impact of insects and fungi on doublegee (Emex australis) in the Western Australian wheatbelt
Authors: Scott John K. , Shivas Roger G.
Published: August 2004

Biotic influences on doublegee(Emex australis Steinheil) seed production wereinvestigated as a precursor to the introduction of new insect biologicalcontrol agents for this weed, and to investigate the cause of doublegeedecline in the northern and central wheatbelt of Western Australia since 1990.The symptoms of the decline are doublegee plants of reduced size withdistorted leaves, collapsed stems, and smaller achenes(the spiny seed-bearing fruit) that crumble when mature.Three sites were investigated in 1992 by surveys for insects and fungi, andinsect and fungus exclusion experiments.Emex stem blight (Phomopsis emicis R. G. Shivas) waspresent at the 3 study sites. The Watheroo site had comparatively high levelsof dock aphids (Brachycaudus rumexicolens Patch) ondoublegee plants, the Badgingarra site had a comparatively high density ofdock sawfly (Lophyrotoma analis Costa) on doublegee, andvery few insects were present on doublegee at the Wongan Hills site. Viruseswere not detected in samples of plants showing the effects of decline.The exclusion experiment showed a significant effect of removing insects andfungi on achene dry weight at the Watheroo site. There was no treatment effectat the Badgingarra and Wongan Hills sites. The biology of the fungus and theaphid lead to the conclusion that the primary cause of doublegee decline isthe dock aphid. This indicates that biological control againstE. australis might be achieved by using insects thatindirectly affect seed quality.
Prognosis of boron deficiency in oilseed rape (Brassica napus) by plant analysis
Authors: Wei Youzhang , Bell R. W. , Yang Yuai , Ye Zhengqian , Wang Ke , Huang Longbin
Published: August 2004

In areas where soils are low in boron (B), the ability to predict B deficiency
by plant analysis depends on the development of calibrated standards and
offers the potential of preventing or minimising losses in seed yield. The
present study aimed at establishing relationships between seed yield in winter
oilseed rape (Brassica napus) and B concentrations in
defined leaves during growth before fiowering and from them to determine
critical values for the prognosis of B deficiency. Oilseed rape cv. Zheyouyou
2 was grown in 10 field experiments in Zhejiang province, south-east China,
with B rates from 0 to 3· 3 kg/ha. At 4 of the sites, oilseed rape
was resown in the following year to assess seasonal effects on critical
concentrations. Experiments were conducted on the 3 main soil groups on which
oilseed rape is grown in south-east China. The youngest open leaf (YOL) was
selected as the sampling part because its B concentrations were strongly
responsive to increasing B supply and well correlated with seed yield
response. In this study, the best model of the relationship between YOL B
concentration and yield was the Mitscherlich equation, which explained
68-89% of the variation in the data. The calculated critical range in
the YOL at seedling stage was 20-25 mg B/kg and appeared to be valid in 2
seasons and on 3 soil types. The critical B range for prognosis of B
deficiency was found to predict consistently those crops in farmers"
fields that had low seed yield and low soil B, but needs to be evaluated in
other growing environments especially those for spring rape.
Cultivar and environmental effects on quality characters in wheat. I. Starch
Authors: Panozzo J. F. , Eagles H. A.
Published: August 2004

The composition of starch in wheat is an important determinant of grain
quality, especially for white-salted noodles. Starch consists of 2 types of
polymer, amylose and amylopectin, and occurs in predominantly larger A-type
and smaller B-type granules. High starch pasting peak viscosity is desirable
for white-salted noodles, and is influenced by the waxy genes coding for
granule-bound-starch synthase (GBSS), which are involved in the synthesis of
amylose.
To study cultivar and environmental effects on the proportion of A-type
granules, the proportion of amylose in starch, starch pasting peak viscosity,
and grain hardness, 7 cultivars were grown in 15 environments which differed
for temperature during grain filling. These cultivars varied in grain hardness
classification and for the presence of GBSS coded by the Wx-B1 locus.
Cultivars null for Wx-B1 GBSS had higher pasting viscosity than those with
Wx-B1 GBSS, verifying the null requirement for cultivars suitable for
white-salted noodles. However, the relationship between amylose concentration
and pasting viscosity was complex, indicating that Wx-B1 influences pasting
viscosity beyond its influence on the proportion of amylose and amylopectin.
Environments with a high level of accumulated temperatures above 30ºC
during the first 14 days after anthesis produced grain with a high proportion
of A-type granules, even when irrigated. The proportion of amylose also
increased with increasing accumulation of temperatures above 30ºC during
the first 14 days, but was not influenced by temperature to the same extent as
granule type. Environmental variation in pasting peak viscosity was large, but
not related to high temperature. The hardness of grain was related to
accumulated temperatures above 30ºC during the second 14 days after
anthesis, with the increase in hardness much greater in soft-grained than
hard-grained cultivars.
Responses of faba bean (Vicia faba L.) to sowing rate in south-western Australia. I. Seed yield and economic optimum plant density
Authors: Jettner R. , Loss S. P. , Martin L. D. , Siddique K. H. M.
Published: August 2004

Sowing rate influences plant establishment, growth, seed yield, and the
profitability of a crop. However, there is limited published information on
the optimum sowing rate and plant density for faba bean in Australia. The
response of the growth and seed yield of faba bean (cv. Fiord) to sowing rate
(70-270 kg/ha) was examined in 19 field experiments conducted over 3 years
in south-western Australia. The economic optimum plant density was estimated
at each site by fitting an asymptotic model to the data and calculating the
point where the cost of extra seed equalled the return from additional seed
yield, allowing a 10% opportunity cost for the extra investment.
On average across all sites and seasons, only 71% of the seeds sown
emerged. Increasing sowing rate resulted in more dry matter production at
first flower and at maturity, and at about half of the sites there was a small
trend of reduced harvest index. In general, the mean number of seeds per pod
(1·8-2·6) and mean seed weight (32-45 g/100 seeds) were
unaffected by sowing rate. As sowing rate increased, the number of pods per
plant (5-35) generally decreased, but this was compensated by the large plant
population and more pods per unit area. The asymptotic models fitted to the
seed yield data accounted for 15-81% of the variance. In 8 experiments,
the models indicated that yield was continuing to increase substantially as
sowing rate increased at the largest sowing rate treatment. The estimated
optimum plant densities in these experiments were beyond the range of the data
or had large standard errors and, hence, were excluded from any further
consideration. Among the remaining 11 experiments, the estimated optimum plant
densities varied from 31 to 63 plants/m2, with a
mean of 45 plants/m2. This study demonstrates that
targeting sowing rates greater than the current commercial practice for faba
bean in southern Australia of 15-30 plants/m2
results in more yield and profit. Additional experiments are required with
sowing rates in excess of 270 kg/ha to estimate accurately the optimum
plant density for faba bean. Fungal diseases were either absent or controlled
with fungicides in these experiments but the interactions between disease,
time of sowing, and sowing rates also deserve further attention.
Compudose® : its effects on the growth, offspring performance, lactational performance, and carcass characteristics of Hereford × Friesian heifers at pasture
Authors: Burke J. L. , Burke J. L. , Morris S. T. , Morris S. T. , McCutcheon S. N. , Parker W. J. , Parker W. J. , McCutcheon S. N.
Published: August 2004

This study investigated the effects of Compudose® on
growth, lactational performance, carcass characteristics, and offspring
performance of Hereford × Friesian (H×F) once-bred heifers (OBH)
under pastoral conditions. Nineteen H×F heifers were implanted with
Compudose 400 at 90 days of age (Compudose 90), 19 were implanted with
Compudose 400 at 210 days of age (Compudose 210), and 19 were not implanted
(control). Neither Compudose group differed significantly in liveweight from
the controls. However, there was a tendency for the Compudose 90 group to be
slightly heavier, and the Compudose 210 group slightly lighter, than the
controls so that the only significant differences in liveweight were between
the two Compudose groups. Similarly, there were no consistent effects of
Compudose on measures of body or skeletal size. The effects of Compudose on
carcass characteristics were small and related mainly to a tendency for
increased muscling.
Compudose delayed conception slightly but had no effects on calf birthweight.
However, calves born to control heifers were 15·3 kg and 16·2 kg
heavier (P < 0·05) at weaning than calves born
to Compudose 90 and Compudose 210 heifers, respectively. Most of this
difference in liveweight was established by Week 4 of lactation. This implies
that Compudose treatment inhibited milk production of the dams, particularly
in the early part of lactation, an effect not detected by the
weigh-nurse-weigh (WNW) method. Implanting heifers with Compudose at 90 or 210
days of age is unlikely to be beneficial, both because it has little positive
effect on liveweight gain or carcass characteristics and because it may
inhibit lactational performance.
Length of rhizome and depth of burial affects the regeneration of bent grass (Agrostis castellana Boiss. et Reuter)
Authors: Batson M-G.
Published: August 2004

Renovation of pastures dominated by bent grass
(Agrostis castellana), by killing the vegetation with
herbicides followed by cultivation and re-sowing, according to current
recommendations, can kill up to 95% of the bent grass. To improve the
success of killing bent grass and reducing the likelihood of regeneration from
rhizomes after renovation, the behaviour of rhizomes after fragmentation was
studied in pots. Rhizomes were cut into different lengths (15, 40, and 100 mm)
to contain 1, 3, and 8 nodes per section and planted at depths of 25, 50, 75,
100, and 200 mm in cultivated soil, with or without competition from
establishing seedlings of perennial ryegrass and white clover. The proportion
of bent grass shoots developing from buried rhizomes was reduced to
<10% when rhizomes were broken into sections containing only a
single node and buried at or below 75 mm. Even after 3 months burial, an
average of 0, 0·2, and 0·4 nodes in 1-node, 3-node, and 8-node
sections, respectively, were still viable after fragmentation and could
potentially develop, should conditions change, ensuring regeneration. The
presence of newly sown pasture did not affect either the development of nodes
or the vigour of shoots of bent grass during the 3-month measurement period.
Pasture production, however, was reduced with increasing bent grass shoot
production such that 8-node sections buried at 25 and 50 mm produced up to 3
times more dry matter per pot than other pasture components, giving bent grass
a competitive advantage.