bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth periodicity of introduced pastures on the northern tablelands of New South Wales
Authors: McPhee M. J. , Ayres J. F. , Curll M. L.
Published: August 2004

This paper reports on the growth periodicity of introduced temperate perennial
pastures in a summer-rainfall environment in the high-rainfall zone of eastern
Australia. Data were derived from an experiment (1985-87) directed at
evaluating pasture cultivars when sown in binary mixtures grazed by sheep. The
data were also simulated by using the decision support system SheepO (Version
4·0) and validated by visual techniques, deviance measures, and
statistical tests. The model simulated pasture growth rate and total biomass
with acceptable accuracy. The study provided a quantification of the growth
rhythm of temperate perennial pastures in this environment. The data show that
growth rhythm comprises a high growth rate (>50 kg DM/ha·day)
during the primary growth cycle in spring, a moderate growth rate (20-50 kg
DM/ha·day) during the secondary growth cycle in summer-autumn, and
low growth rate (<20 kg DM/ha·day) in winter. The growth
performance of introduced pastures based on cv. Demeter tall fescue
(Festuca arundinacea) exceeded that of pastures based on
cv. Sirosa phalaris (Pharlaris aquatica) in all seasons,
at low and high stocking rates, and in all 3 years. The results highlight the
potential for pasture cultivars with enhanced seasonal growth rate to increase
the pasture feed supply for grazing animals.
Seasonal changes in the morphology of wool follicles in Finewool and Strongwool Merino strains grazing at different stocking rates in southern Australia
Authors: Hynd P. I. , Hughes A. , Earl C. R. , Penno N. M.
Published: August 2004

An experiment was conducted to determine the impact of stocking rate and
Merino strain on follicle morphology before and after the break of the season
in the highly seasonal Mediterranean environment of southern Australia. Groups
of Finewool and Strongwool Merino sheep were allocated to 9 stocking rates on
mixed legume-grass pastures, and skin biopsy samples were taken at monthly
intervals from February to June. A scoring system, based on the morphology of
follicles in transverse section, was used to characterise these samples. The
proportion of follicles classified as ‘normal’ dropped markedly,
and the proportion of follicles which contained no fibre correspondingly
increased, after the break of the season in April. On average about 10%
of the follicles became inactive but there was considerable variability (range
2-63%) between animals.
The proportion of inactive follicles was significantly affected by stocking
rate but there was little difference between Merino strains. Maximum follicle
inactivity coincided with the period of minimum fibre diameter and minimum
liveweight in May, approximately 1 month after the break of the season. The
proportion of inactive follicles accounted for 27% and 28% of
the variance in staple strength of the Finewool and Strongwool strains,
respectively. Minimum fibre diameter accounted for 63% and 61%
of the variance in staple strength, and coecient of variation in fibre
diameter accounted for 49% and 58% of the staple strength
variance, respectively, in the 2 strains. Together, minimum fibre diameter and
coecient of variation in fibre diameter accounted for almost 75% of the
variance in staple strength in both strains. Addition of a term for the
proportion of inactive follicles did not remove any additional variance in
staple strength.
These results suggest that the follicles of Merino sheep in Mediterranean
environments undergo significant morphological changes throughout the year.
These changes differ from the normal sequence of events associated with the
hair cycle and appear to be associated with the break of the season in autumn.
The morphological changes which occur in the follicles are similar to those
induced by epidermal growth factor or cortisol, and may reflect a stress
response. Our results suggest that nutritional stress is at least partially
responsible for the follicular pathology described. Management strategies
aimed at reducing the decrease in fibre diameter which occurs in autumn,
shearing sheep in autumn to coincide with the minimum fibre diameter, and
selection of sheep which have a low coecient of variation of fibre diameter,
are likely to be the most effective means of preventing low staple strength in
sheep grazing in Mediterranean environments. Nevertheless, the impact of
follicle shutdown and changes in follicle morphology on wool characteristics
other than staple strength needs to be determined.
Production, persistence, and water-soluble carbohydrate accumulation in 21 contrasting populations of Dactylis glomerata L. subjected to severe drought in the south of France
Authors: Volaire F. , Lelièvre F.
Published: August 2004

In rainfed Mediterranean areas, summer drought is the main factor affecting
the persistence of perennial grasses. Most available cultivars of
Dactylis glomerata (cocksfoot) exhibit low persistence
in this environment; therefore, research is needed on the relationships
between plant physiology and recovery after severe drought. In the field, we
subjected a large range of populations and cultivars of cocksfoot to 3 months
of drought followed by 3 weeks of rewatering.
Principal component and cluster analysis discriminated 3 groups of genotypes:
(1) late heading populations and cultivars of temperate
origin (ssp. glomerata) that exhibited high tiller
mortality in summer; (2) early heading populations of
Mediterranean origin (ssp. hispanica) that survived well
but had a low growth potential; (3) very early heading
Mediterranean cultivars (ssp. glomerata ×
hispanica) that survived and recovered actively.
The study of bases of youngest enclosed leaves (surviving organs) showed that
osmotic potential in living bases was not significantly different between
groups of populations; dry matter content was higher in bases of hispanica
populations at the onset of drought; total water-soluble carbohydrate and
fructan contents increased as drought progressed and reached 35-40% of
dry matter in bases at the end of the drought.
Drought survival was best correlated with both the ratio between low and high
weight fructans in July (summer) and the heading date
(R2 = 0·75,
P < 0·001). Recovery yield after autumn
rewatering was highly correlated with both of these variables and the dry
matter content in leaf bases in June
(R2 = 0·75,
P< 0·001), which may be associated with levels
of summer dormancy. These results emphasise the role of ontogeny in drought
resistance and can be used to predict plant survival in a large range of
populations of cocksfoot.
Root production of a barrel medic (Medicago truncatula) pasture, a barley grass (Hordeum leporinum) pasture, and a faba bean (Vicia faba) crop in southern Australia
Authors: Crawford Michael C. , Grace Peter R. , Bellotti W. (Bill) D. , Oades J. Malcolm
Published: August 2004

Total root biomass production of a grazed annual legume pasture
(Medicago truncatula), a grazed annual grass pasture
(Hordeum leporinum), and a grain legume crop
(Vicia faba) was estimated using a sequential coring and
summation technique with corrections made for root death and decomposition
during the season. Distribution of live root biomass with depth and C: N
ratios of roots were also determined. Both in a dry season and in a season of
average rainfall, total root biomass production of the 2 pasture species was
similar and always greater than the faba beans. Total root biomass production
estimated using this technique was 60-200% greater than the maximum
live root biomass, suggesting that there was significant root turnover during
the season. In the dry season, the ratios of total root production to total
shoot production were 0·55, 0·57, and 0·32 for the barrel
medic, barley grass, and faba beans, respectively, and in the wetter season,
the ratios were 0·40, 0·42, and 0·25, respectively.
Potential errors in the technique related to the recovery of root material and
the decomposition of dead roots and old organic material are discussed, as are
the implications of this information for soil organic matter dynamics.
Factors influencing transmission of alfalfa mosaic virus through seed of annual medics (Medicago spp.) and the genetic control of seed transmission rate
Authors: Pathipanawat W. , Jones R. A. C. , Sivasithamparam K.
Published: August 2004

Factors likely to influence rates of transmission of alfalfa mosaic virus
(AMV) through seed to seedlings of annual medics
(Medicago spp.) and genetic control of the magnitude of
its seed transmission rate were investigated in plants from 17 early-flowering
accessions of M. polymorpha and in progenies of crosses
involving M. murex cv. Zodiac × accession 5320 as
parents. Plants were graft-inoculated when 6 weeks old to ensure successful
and uniform infection. To exclude variation in seed transmission rates due to
virus isolate or temperature, only 1 AMV isolate was used and the plants were
kept under uniform temperature conditions. In
M. polymorpha, significant differences were found
between accessions in the levels of AMV transmitted through seed to progeny
seedlings, SA 8250 giving the highest mean level of seed transmission
(52%) and SA 4188 the lowest (3%). Neither virus concentration
nor symptom severity influenced the rates of seed transmission obtained.
However, part of the variation in seed transmission rates found in these
accessions was related to their flowering times, seed transmission rates
increasing as the interval between inoculation and owering increased. In seed
samples collected from individual graft-inoculated plants of
M. murex from (i) the
F2 generation from crosses and reciprocal crosses, and
(ii) the backcross progenies, the rates of transmission
of AMV through seed to seedlings ranged from 0 to 77% and showed a
continuous pattern of variation. Also, there was evidence of transgressive
segregation for the low seed transmission rate condition. This indicates that
the low seed transmission rate condition for AMV in medics is quantitatively
inherited and under polygenic control. In contrast, when the pods from
F2 progeny plants from the crosses and reciprocal
crosses were examined, the segregation ratios obtained revealed that the
smooth pod character from parent accession 5320 was controlled by a single
recessive gene, for which the name sp is proposed. The
presence in a plant of gene sp, or of its spiny
pod-determining allele from the other parent cv. Zodiac, was not correlated
with low seed transmission rates of AMV. It is concluded that selection for
low rates of seed transmission and a population breeding approach can be used
to produce improved M. polymorpha and
M. murex cultivars with good resistance to seed-borne
AMV
Dynamics of biologically fixed N in legume-cereal rotations: a review
Authors: Chalk P. M.
Published: August 2004

Agronomically significant N yield responses of cereals following grain legumes
compared with cereal monoculture are frequently measured. The positive N
response of the cereal has been attributed to the transfer of biologically
fixed N, to N-sparing under the antecedent legume, and to less immobilisation
of nitrate during the decomposition of legume residues. Methods for estimating
the transfer of biologically fixed N in rotations, and for separating the N
benefit into fixed N and non-fixed N components, are reviewed. Available data
indicate that both sources of N contribute to the N benefit. The role of the
grain legume in the gain or drain of soil N is evaluated by considering the
balance between symbiotic dependence and N harvest index, as well as long-term
changes in total soil N. Several 15N-based techniques
for direct estimation of inputs of biologically fixed N to the soil N pool are
reviewed. N balances in grain legume-cereal rotations may be positive or
negative depending on the legume species, symbiotic performance, and agronomic
factors.
Productivity and nitrogen use of three different wheat-based rotations in North West Syria
Authors: Wood M. , Pilbeam C. J. , Harris H. C. , Tuladhar J.
Published: August 2004

Productivity of 3 different 2-year crop rotations, namely continuous wheat,
wheat-chickpea, and wheat-fallow, was measured over 4 consecutive seasons
beginning in 1991-92 at the ICARDA station, Tel Hadya, Syria. Nitrogen (N)
fertiliser (30 kg N/ha at sowing) was broadcast every other year in the
continuous wheat only. 15N-labelled fertiliser was used
to quantify the amount of nitrogen supplied to the crops through current and
past applications of fertiliser and by N2 fixation. The
remaining N in the crop was assumed to come from the soil.
In any single season, wheat yields were unaffected by rotation or N level.
However, 2-year biomass production was significantly greater (32%, on
average) in the continuously cropped plots than in the wheat-fallow rotation.
On average, <10% of the N in the wheat crop came from fertiliser in
the season of application, and <1·2 kg N/ha of the residual
fertiliser was recovered by a subsequent wheat crop. Chickpea fixed 16-48 kg
N/ha, depending on the season, but a negative soil N budget was still
likely because the amount of N removed in the grain was usually greater than
the amount of atmospheric N2 fixed. Uptake of soil N was
similar in the cereal phase of all 3 rotations (38 kg N/ha, on average),
but over the whole rotation at least 33% more soil N was removed from
continuously cropped plots than from the wheat-fallow rotation, suggesting
that the latter is a more sustainable system.
A laboratory study showed that although wheat and chickpea residues enhanced
the gross rate of N mineralisation by c. 50%, net
rates of N mineralisation were usually negative. Given the high C/N ratio
of the residue, immobilisation, rather than loss processes, is the likely
cause of the decline in the mineral N content of the soil. Consequently,
decomposition of crop residues in the field may in the short term reduce
rather than increase the availability of N for crop growth.
The sulfur and selenium status of pregnant ewes grazing Mediterranean pastures
Authors: White C. L. , Kumagai H. , Barnes M. J.
Published: August 2004

Sheep require both sulfur and selenium for normal wool growth and to protect
against diseases caused by free radical damage. This work describes the
seasonal changes in the concentrations of sulfur, both as glutathione and
inorganic sulfur, and selenium, in pregnant ewes, and the effects thereon of a
multi-element supplement containing sulfate, selenium, and vitamins A and E.
Merino ewes (420) were divided into 4 equal treatment groups, control (C),
vitamins (V), minerals (M), and vitamins plus minerals (V+M), in a
22 factorial design. The control group was offered a
loose salt lick NaCl at 175 g/head· day and the mineral group an
equivalent amount of a multi-element mineral mix (Siromin). The vitamin groups
were offered either salt or the mineral mix with added vitamins E and A.
Treatments started 3 weeks prior to mating in November and lasted until 1 week
prior to lambing in May. Sheep were sampled until weaning in September.
Regardless of treatment, the concentrations of glutathione in blood and liver
declined by 60% and 40%, respectively, when sheep were grazing
dry pasture during summer. Sulfate-sulfur concentration in plasma of ewes in
the C and V groups declined by 80% in the same period to <10 mg
sulfur/L, values indicative of sulfur deficiency. The mineral supplement
(M) increased concentrations of plasma sulfate-sulfur at most sample times,
but the V+M treatment generally did not. Glutathione concentration in
blood and tissues showed little response to supplementary minerals or
vitamins.
Selenium concentration in blood of ewes was inversely related to the number of
years since receiving a selenium pellet. Mean concentration declined to the
deflcient range (0·02 mg/L) in spring in C and V ewes. Treatment
with the mineral mix raised blood selenium concentrations to 0·060
mg/L within 2 months and maintained concentrations above the deficient
range for several months after cessation of treatment.
The results provide evidence of an under supply of sulfur during the dry
summer period and of a need to administer selenium pellets at least twice in
the lifetime of ewes.
A simulation study of wheat crop response to water supply, nitrogen nutrition, stubble retention, and tillage
Authors: O'Leary G. J. , Connor D. J.
Published: August 2004

A series of simulations was made with a fallow{wheat crop simulation
model to examine the effects of stubble retention and tillage on yield for 2
semi-arid environments in north-western Victoria over a 100-200-year period.
The fallow treatments comprised 4 combinations of stubble management and
tillage in 18-month-long fallows of a fallow{wheat rotation. The 2 sites
are representative of the major soil types of the region: a chromic vertisol
at Dooen and a calcic xerosol at Walpeup.
Stubble retention had the greatest effect on yield, providing a median
increase of 0·8 and 0·6 t/ha at Dooen and Walpeup,
respectively. Zero tillage had an importantbut small advantage in the presence
of stubble at Dooen (0·2 t/ha) and no significant advantage under
any system at Walpeup. Yield response was primarily caused through increased
fallow-stored water of approximately 89 and 25 mm at Dooen and Walpeup,
respectively. The accumulation of soil mineral nitrogen (SMN) at sowing in
fallows did not show the same treatment differences as with water or yield.
There was a significant interaction between soil type and fallow method. At
Dooen, stubble depressed SMN by about 24 kg N/ha (163{185 kg
N/ha) below those without stubble (188-207 kg N/ha). Tillage reduced
SMN with or without stubble by about 20 kg N/ha. At Walpeup, on the other
hand, the highest SMN was associated with tillage and was enhanced by stubble,
but the differences were small (<10 kg N/ha). Nitrogen fertiliser
produced a small increase in yield (median 0·2 t/ha) at Dooen,
increasing to about 0·4 t/ha in wetter years when stubble was
retained and fallows were maintained with zero tillage. Over a 100-year
period, nitrogen fertiliser reduced the rate of yield decline. The use of
nitrogen fertiliser with stubble retention and zero tillage offers an
opportunity for arresting declining yield and quality in intensive cropping
systems in the Wimmera region of Victoria.
The application of RAPD markers for potato cultivar identification
Authors: Ford Rebecca , Taylor Paul W. J.
Published: August 2004

Where morphological techniques had failed, closely related potato cultivars
were differentiated using random amplified polymophic DNA (RAPD) analysis
based on the polymerase chain reaction. Total gemomic DNA was extracted from
young sprout tissue from harvested tubers. Of 63 10-mer oligonucleotide
primers screened, 51 primers produced a total of 256 amplification products of
which 33 were polymorphic between the cultivars assessed. Polymorphic bands
were selected to produce cultivar-specific markers to identify correctly
suspect material in commercial plantings. Furthermore, a cultivar-specific
RAPD marker was shown to be sufficiently robust and stringent for the
identification of potential cultivar contamination in the field. DNA titration
experiments revealed that a specific marker for cv. Sebago could be detected
in a DNA admixture at a ratio of 1× cv. Sebago to 5 × cv. Exton. A
commercial block of cv. Exton was thus randomly sampled and the level of
cultivar purity assessed.
Contribution of Rhizoctonia to reduced seedling growth of direct-drilled wheat: studies with intact cores
Authors: James, R. A. , Kirkegaard J. A. , Munns R.
Published: August 2004

Wheat seedlings were grown in intact cores of soil removed from 2 field
experiments in southern New South Wales where the soil-borne pathogen
Rhizoctonia solani had been implicated as a cause of
slower seedling growth in direct-drilled soil compared with cultivated soil.
Experiments were conducted with intact cores in controlled environments using
fumigation to assess the role of Rhizoctonia in the
growth responses. Seedling growth was lower in direct-drilled cores than
cultivated cores from both sites at a very early stage. The growth reductions
were completely removed by fumigation, confirming previous reports that
biological factors rather than physical factors were responsible for reduced
growth.
In cores from the Galong site, Rhizoctonia symptoms were
severe at the 5-leaf stage (8 on a scale of 0-10) and the reduction in leaf
growth at earlier stages coincided with the appearance of
Rhizoctonia symptoms on the roots. Seedling growth was
not reduced until the severity was >5. This corresponded with a
root-cutting experiment where shoot growth was unaffected until 3 of the 5
seminal roots of healthy seedlings were removed. Pre-sowing soil disturbance
to a depth of 5 cm in unfumigated soil increased shoot growth from 47 to
84% of the fumigated controls with no further improvement when the
depth of disturbance was increased to 10 cm, suggesting the pathogens
responsible were confined to the 0-5 cm layer and were not completely
eliminated by disturbance. Pre-sowing disturbance had no effect on shoot
growth in fumigated soil.
In cores from the Harden site, Rhizoctonia symptoms were
moderate at the 5-leaf stage; however, reductions in leaf and root growth at
earlier stages occurred 7 days before any symptoms of
Rhizoctonia or other pathogens were visible on the
roots. The results suggest that other inhibitory organisms are present at the
Harden site and cause significant reductions in seedling growth in the absence
of visible disease symptoms. Pythium spp. pathogenic to
wheat are known to be present at the site but their role has not been
confirmed. Further studies are required to identify the inhibitory organisms
and to determine the mechanisms by which they reduce early seedling growth.
'Haying-off', the negative grain yield response of dryland wheat to nitrogen fertiliser. I. Biomass, grain yield, and water use
Authors: Herwaarden A. F. van , Farquhar G. D. , Angus J. F. , Richards R. A. , Howe G. N.
Published: August 2004

"Haying-off" was studied by comparing wheat responses to applied
nitrogen (N) at 3 sites in southern New South Wales, which differed in the
amount and timing of rainfall during crop growth. At a site where the crops
encountered little water deficit, dry grain yield increased from 607
g/m2 for a low-N control crop to 798
g/m2 for a high-N crop. At a site with severe
terminal drought, dry grain yield decreased 24% from 374
g/m2 for the control, to 284
g/m2 for the highest N crop. At the third site,
yields increased with small applications of N, whereas greater applications
resulted in a negative yield response. At the 2 latter sites, the crops that
showed decreased yield with applied N had clearly hayed-off.
At all sites, irrespective of water status, N application resulted in
increases in biomass at anthesis, spike density, kernels per spike, and kernel
number. Kernel weight decreased in response to additional N at all sites, but
most markedly at the haying-off sites, where it decreased by up to 38%.
Harvest index increased in response to N at the high-rainfall site, but
decreased in crops that hayed-off. Grain protein increased in response to N at
all sites, with a range from 9% to 18% at the haying-off sites.
The apparent retranslocation of assimilates to grain contributed 37-39%
of grain yield (depending on N supply) at the high-rainfall site, compared
with 75-100% at the haying-off sites. In contrast, when apparent
retranslocation was expressed in relation to biomass at anthesis, it remained
relatively constant, amounting to 23-26% at the high-rainfall site and
24-28% when crops hayed-off.
By anthesis, high-N crops extracted more soil water than the low-N crops. By
maturity the most severely hayed-off crop had extracted 10 mm less soil water
than a low-N crop, but at the high rainfall site the high-N crops extracted 20
mm more soil water than the control crops. The weather conditions between
anthesis and physiological maturity were relatively mild, with no daily
maximum temperatures above 30ºC and no sudden increases in evaporative
demand.
Thus, there appeared to be 3 processes leading to haying-off. Firstly, the
results confirm previous studies showing that haying-off was associated with
reduced post-anthesis assimilation in response to a lack of soil water. The
water deffcit was due to vigorous vegetative growth stimulated by a high level
of soil N and was not associated with heat shocks or sudden increases in
evaporation. Secondly, the most severely hayed-off crop failed to extract soil
water fully, leading to a further reduction in post-anthesis assimilation.
Thirdly, there was inadequate apparent retranslocation of pre-anthesis
reserves to compensate for the lack of post-anthesis assimilation.
'Haying-off', the negative grain yield response of dryland wheat to nitrogen fertiliser II.Carbohydrate and protein dynamics
Authors: van Herwaarden A. F. , Angus J. F. , Richards R. A. , Farquhar G. D.
Published: August 2004

Changes in carbohydrate and protein in stems, leaves, spikes, and grain
between anthesis and maturity were measured in 3 dryland wheat crops whose
responses to applied nitrogen (N) ranged from increases in grain yield through
to decreases in grain yield. This decrease in grain yield, known as
haying-off, was described in Paper I in this series. Measurements reported
there showed that apparent retranslocation, defined as the decrease in weight
of vegetative organs during grain filling, was generally greater for crops of
high-N status than for those of low-N status. Retranslocation in this context
is the process of moving compounds assimilated before anthesis to the grain.
The largest source of assimilates available for retranslocation in all crops
at anthesis was water-soluble carbohydrates (WSC) contained in the stems and
spikes, and represented a potential contribution of 34-50% to yield for
the most severely hayed-off crops. The absolute amount of WSC present in
high-N crops was less than that in low-N crops, despite a greater biomass. The
lack of this form of assimilate available for retranslocation was the greatest
single contributor to the yield reduction of the crops of high-N status. The
quantity of protein retranslocated increased with crop N status, but the
amounts involved were smaller than the quantity of WSC. Virtually all of the
WSC reserves were utilised in all crops, in contrast to the protein reserves
which were poorly retranslocated in the hayed-off crops. Most of the WSC was
contained in the stems and most of the protein in the leaves.
The potential contribution of retranslocated WSC and protein from leaves was
more difficult to estimate because of an apparent loss of 40-50% of
leaf tissue after anthesis. The nature of the loss was estimated from the
amounts of acid detergent fibre (ADF; fibre not solubilised by hot acid
detergent) present at anthesis and maturity. Since ADF comprises cellulose and
lignin which decompose slowly, the loss of 30-37% of ADF was applied as
a correction factor in calculating potential retranslocation from leaves.
There was no loss of stem ADF. Using the correction, the potential
retranslocation of leaf protein and leaf WSC was equivalent to 6-15% of
yield.
The export of all WSC and protein failed to account for the total decrease in
leaf biomass, even after correction of leaf losses. We identified
hemicellulose as an additional and previously unsuspected source of
carbohydrate for retranslocation. Unlike WSC, the amount of leaf and stem
hemicellulose at anthesis increased with crop N status, and the increase in
hemicellulose between anthesis and maturity was equal to 10-17% of
yield.
Transient high temperatures during seed growth in narrow-leafed lupin (Lupinus angustifolius L.) II. Injuriously high pod temperatures are likely in Western Australia
Authors: Reader M. A. , Dracup M. , Atkins C. A.
Published: August 2004

Studies under controlled environment conditions indicate that transient high
temperatures (34-38˚C) during grain filling can significantly reduce
weight per seed in narrow-leafed lupin
(Lupinus angustifolius L.). This study has shown that on
average, lupin pods reach temperatures about 3-5˚C higher than the
maximum daily air temperature during seed filling under field cropping
conditions. These differences do not appear to be markedly influenced by the
amount of radiation intercepted by the canopy, stage of pod development, or
position of the pods in the canopy, but fluctuate more as a result of
differences in radiation intensity, wind speed, and water availability.
Trickle irrigation reduced the difference between pod and air temperature by
about 2˚C. Lupin species with larger pods (L. cosentinii and
L. atlanticus) reached higher maximum daily temperatures than those of
L. angustifolius. Long-term meteorological data indicate
that air temperatures during seed filling of lupins in Western Australia are
likely to exceed 30˚ C and will occasionally exceed 35˚ C. In
lupin-growing areas of Western Australia, pod temperatures exceeding
33-35˚ C can be expected about 1 year in every 3, and more rarely (about
1 in 10 years), pod temperatures exceeding 38-40˚ C can be expected.
These transient high temperatures are likely to increase significantly the
year to year variation in yields of lupin grain.
Impact of CIMMYT varieties on the genetic diversity of wheat in Australia, 1973-1993
Authors: Brennan John P. , Fox Paul N.
Published: August 2004

Wheats derived from germplasm developed by the International Maize and Wheat
Improvement Center (CIMMYT) have been grown widely in Australia since the
early 1970s. The impact of CIMMYT germplasm on the genetic diversity of
Australian wheats over the 20 years to 1993 is examined. On average, the
diversity at a national level remained relatively high throughout the period,
but this finding varied markedly between States. While there was significant
increase in diversity in South Australia and Western Australia, there was a
narrowing of the genetic base of varieties grown in the eastern States,
especially Victoria, accompanying the widespread use of CIMMYT germplasm.
Chickpea in wheat-based cropping systems of northern New South Wales I. N2 fixation and influence on soil nitrate and water
Authors: Marcellos H. , Felton W. L. , Herridge D. F.
Published: August 2004

Chickpea has potential as a rotation or break crop in the northern grains
region of New South Wales and Queensland. Definition of that potential
requires information on chickpea N2 fixation and on
effects of chickpea on maintenance of soil N fertility and delivery of mineral
N for use by a following cereal crop. Results from 6 experiments in northern
NSW in which chickpea and wheat in one season were followed by wheat in
subsequent seasons indicated variable N2 fixation by
chickpea (mean 73 kg/ha; range 4-116 kg/ha), associated with variable
Pfix (percentage of chickpea N derived from
N2 fixation) (mean 57%; range 4-79%).
There were no consistent differences between chickpea and wheat in effects on
soil water, either pre-harvest or after the summer fallow. Chickpea
‘spared’ nitrate, relative to wheat (mean 15 kg/ha; range 1-35
kg/ha), and mineralised additional nitrate during the summer fallow (mean
18 kg/ha; range 5-40 kg/ha). Nitrate-N in the top 1·2 m of the
soil profile at sowing of the following wheat crop was on average 89 kg/ha
after chickpea (range 63-113 kg/ha) and 56 kg/ha after wheat (range
33-94 kg/ha). Nitrogen mineralisation rates during the summer fallow at 2
sites of 0·17 and 0· 21 kg N/ha · day (after
chickpea), although greater than the rates after wheat (0· 07 and
0·12 kg N/ha · day), were not sufficient to meet the N
requirements of a moderate to high yielding cereal crop. We concluded that
chickpea did not fix sufficient N2 or mineralise
sufficient N from residues either to maintain soil N fertility or to sustain a
productive chickpea{wheat rotation without inputs of additional
fertiliser N.
Chickpea in wheat-based cropping systems of northern New South Wales. II. Influence on biomass, grain yield, and crown rot in the following wheat crop
Authors: Felton W. L. , Marcellos H. , Alston C. , Martin R. J. , Backhouse D. , Burgess L. W. , Herridge D. F.
Published: August 2004

Rotational effects of chickpea, an important N2-fixing
pulse legume of the northern grains region, on subsequent wheat require
quantification of the contribution of the legume to soil N and the N status of
the wheat, and of suppression of soil and stubble-borne pathogens, such as
crown rot (Fusarium graminearum Schwabe Group 1).
Results from selected treatments of 10 experiments in northern New South Wales
in which chickpea and wheat in one season were followed by wheat in following
seasons indicated generally higher dry matter (DM) and grain yields of wheat
after chickpea than after wheat. Responses to chickpea were -0·8 to
3·3 t/ha (shoot DM) and -3 to 39 kg N/ha (shoot N). Responses
in wheat grain yields were -0·1 to 1·7 t/ha (mean
0·85 t/ha); grain N responses were -2 to 33 kg/ha (mean 19
kg/ha). Grain protein responses were small (0·6%) and
variable. Although these productivity responses could be explained largely in
terms of additional nitrate-N following chickpea, we measured reduced
incidences of crown rot in wheat after chickpea (range 1-36%, mean of
12%), compared with wheat after wheat (range 5-52%, mean
30%). Modelling the incidence of crown rot indicated highly significant
interactions between prior crop and total water (pre-plant soil water plus
in-crop rainfall). When wheat followed chickpea, incidence of the disease
declined sharply with increasing water. When wheat followed wheat, there was a
marginal decline in disease incidence with increasing water. Our results
support the strategy of using legumes in rotation with wheat in the northern
grains region for enhanced soil-N supply and disease-break effects.
Nitrate leaching from a Riverine clay soil under cereal rotation
Authors: Smith C. J. , Dunin F. X. , Zegelin S. J. , Poss R.
Published: August 2004

Leaching of nitrate from a Red earth (Red Kandasol) at Wagga Wagga was
measured during the wheat and lucerne phase of a crop rotation. Wheat was
grown in 1993, and the site was sown to lucerne in 1994, a drought year. The
paddock was re-sown to lucerne on 3 June 1995. In 1993, the soil water content
in the 0·25-0 ·90 m layer had been maintained near its drained
limit from previous harvest until the autumn break. With these initial
conditions, current season rainfall displaced the resident soil water.
Drainage measured at 0·25 m was 120 mm and produced 97 mm of drainage
at 0·9 m. In contrast, the soil water storage in the
0·25-0· 90 m layer at the autumn break in 1995 was about 70 mm
below the drained limit because of the drought in the preceding year. Under
these conditions, drainage response differed from 1993 in that 112 mm of
drainage at 0·90 m was generated by a much higher drainage of 178 mm at
0·25 m. These differences emphasise a need for appreciable soil water
deficits in the subsoil in order to minimise drainage from the root-zone.
Infiltration of rainfall, water redistribution, drainage, and transfer of
NO-3-N within the soil profile
were modelled using the Richard"s equation. The model gave acceptable
predictions of evapotranspiration and its partitioning for transpiration, soil
N transformations, and NO-3-N
redistribution and leaching under wheat and lucerne. Nitrate leached below
0·25 m was 31 and 77 kg N/ha in 1993 and 1995, but only 4·2
and 12 kg N/ha leached beyond the root-zone, respectively. Root growth
into the subsoil and uptake was effective in reducing the downward movement of
NO-3-N. Leaching of
NO-3-N below 0· 25 m
produced 2·2 kmol H+ /ha in 1993 and
5·5 kmol H+ /ha in 1995. Corresponding values
for net acidity production in 0-0·9 m layer were 0·3 and
0·9 kmol H+ /ha. It would appear from both
measurements and simulations that management systems, either current or
projected, cannot prevent the movement of
NO-3-N from its zone of
production.
Acidification of upper soil layers is the inevitable consequence of such
export, leading to the need for added alkalinity whenever the biomass is not
returned to the soil.
Pasture legume species differ in their capacity to acidify soil
Authors: Tang C. , Barton L. , Raphael C.
Published: August 2004

The capacity of subterranean clover
(Trifolium subterraneum L. cv. Clare), medic
(Medicago murex Willd. cv. Zodiac), serradella
(Ornithopus sativus Brot. line SP1/13), biserrula
(Biserrula pelecinus L. line Mor99), and woolly clover
(Trifolium tomentosum L.) to acidify soil under
N2 fixation was compared in a pot experiment using a
poorly buffered sandy soil. The amount of acid produced per kg shoot dry
matter (specific acid production) varied betweefin species and with growth
stages, ranging from 44 to 128 cmol/kg shoot. Subterranean clover and
serradella acidied soil to a greater extent than woolly clover and medic,
whereas biserrula acidified soil least. Irrespective of pasture species and
growth stage, specific acid production correlated well with concentrations of
excess cations and calcium in shoots. Furthermore, total excess cation, ash
alkalinity, and calcium in shoots were all good indicators of total acid
production across all of the species.
Influence of liveweight, liveweight change, and diet on wool growth, staple strength, and fibre diameter in young sheep
Authors: Masters D. G. , Peterson A. D. , Mata G. , Liu S. M.
Published: August 2004

The effects of initial liveweight, liveweight change, and composition of the
diet on wool growth and staple strength in weaner sheep were investigated.
Weaner wethers (64) were allocated to treatments in a factorial design
(23). The factors were initial liveweight (heavy, 33 kg;
light, 25 kg), liveweight change (fed at maintenance for 56 days, or 28 days
at 0 ·6×maintenance then 28 days at
1·6×maintenance), and diet (lupin seed based diet or canola meal
based diet). The heavier weaners grew approximately 1·9 g/day more
wool than the light sheep during the experimental period and this resulted in
a higher clean fleece weight (1·8 v. 1·4
kg), staple strength (37 v. 27·4 N/ktex), and
fibre diameter (18·0 v. 17·4 µm).
Substituting canola meal for lupin seed increased wool growth during the
experiment and clean wool yield, but did not affect clean fleece weight or
staple strength. The weaners fed to lose and then gain weight grew wool with a
lower staple strength than the weaners fed to maintain weight through the
experiment (28·6 v. 35·8 N/ktex), but
there were no differences in any of the other fleece characteristics. The
ratio of wool growth to dry matter intake (DMI) was higher in the sheep fed
canola meal than those fed lupins (by approximately 1·5 g/kg DMI)
and higher in weaners losing weight than those fed to maintain weight (by
approximately 4·5 g/kg DMI). From a practical perspective, these
results indicate that initial liveweight and liveweight change both influence
staple strength and wool growth and need to be included in any management
strategy to improve wool quality of young sheep.
Fate of urea nitrogen in sheep urine applied to soil at different times of the year in the pasture - wheat rotation in south Western Australia
Authors: Thompson R. B. , Fillery I. R. P.
Published: August 2004

Sheep urine labelled with 15N-urea was applied toconfined micro-plots at different times of the year to follow the fate of ureaN in urine in the grazed pasture-wheat rotation in south Western Australia.Three field experiments were conducted on the same site on a loamy sand.Applications were made either to pasture residues (Expts 1 and 2) which weresubsequently sown to wheat, orto growing pasture in winter-spring, (Expt 3).In Expt 1, urine was applied in November 1990 (9·8 gN/m2) and April 1991 (46·1 gN/m2). From both applications, losses of15N attributed to NH3volatilisation were c. 50% within 2 weeks of application. Another10% loss was attributed toNO-3 leaching during the followinggrowing season and 15% was recovered by the wheat crop. In Expt 2,urine was applied in October 1991 (4·6 gN/m2), January 1992 (15·6 gN/m2), and March 1992 (13·6 gN/m2). Attributed NH3 losseswithin 2 weeks, in terms of 15N-urea applied, were40% (October and January urine) and 30% (March urine) andNO-3 leaching losses were estimated to be 20% forthe 3 applications. Recoveries in wheat (November 1992) were 4, 7, and12% of 15N applied in the October, January, andMarch urine applications. In Expt 3, urine was applied in August 1992(12·3 g N/m2) and September 1992 (25·9g N/m2). Attributed NH3 losseswere 10% of applied 15N for the August and30% for the September application. Plant uptake of15N was rapid and by mid October was 42% from theAugust application and 47% from the September application. Recovery of15N in soil organic N was generally 17-25% whenurine was applied to pasture residues and bare soil,and 21-37% whenurine was applied to growing pasture. It is suggested thatNH3 volatilisation was the predominant N loss mechanism.The amount of NO-3 leached wasprimarily influenced by summer rainfall, the length of time urine-N was insoil before the onset of winter rainfall, and the distributionof winterrainfall. Little of the 15N-labelled urine was eitherrecovered by, or available for, subsequent wheat crops, suggesting thatcalculations for estimating the N supply from pastures to cereal cropsmustdiscount most N returned in urine by grazing animals.
Barley yield and grain protein concentration as affected by assimilate and nitrogen availability
Authors: Boonchoo S. , Fukai S. , Hetherington Suzan E.
Published: August 2004

Two types of experiments were conducted with the malting barley cv. Grimmett
to examine how assimilate and nitrogen (N) availability at different growth
stages determined yield and grain protein concentration (GPC) in south-east
Queensland. In one series of experiments, plants were sown in April, June, and
August so that they would experience different growing conditions, and
responses to N application rate were examined. Another experiment examined
response of growth, yield, and GPC to variation of assimilate production pre
and post anthesis, caused by the canopy manipulation treatments of opening,
closure, and 50% shading at 3 different growth stages.
Without N application all 3 sowings produced similar yields
(1·9-2·3 t/ha), but when N was applied, yield was higher and
responded more to applied N in the June sowing than in the other sowings.The
different responses of grain yield to N application rate among the 3 sowing
dates were not due to differences in N uptake but to the efficiency of N use;
with favourable temperatures throughout crop growth, the crop sown in June
utilised N most eciently to develop a large number of grainsand to produce
sufficient as similates to fill these grains. When yield had a positive
response to low N application rates, then there was generally no response of
GPC, whereas when there was no response of grain yield to further rate of N
application then GPC increased.
The results of the second experiment show that N uptake depended on plant N
demand at early stages of growth when N was still available in the soil, but
total N content of tops at maturity was similar among canopy manipulation
treatments. Canopy opening at any stage of growth tended to increase tiller
number, leaf area index, and above-ground dry matter, but the effect was
greater attillering stage which produced the highest yield because of the
greatest number of heads. Shading reduced yield at all stages, but
particularly at pre-anthesis. Shading and canopy closure during grain filling
reduced grain yield, but with similar N uptake these treatments significantly
increased GPC
.These results indicate that GPC depends on both assimilate and N availability
to grain, and GPC can increase sharply when grain yield is reduced with low
assimilate availability as a result of adverse growing conditions. Responses
of grain yield to applied N depended on environmental conditions, particularly
the patterns of air temperature during growth, and the crop utilised N more
efficiently to produce higher yield when it was not exposed to extreme
temperatures during the latter stages of growth.
Effects of phosphorus fertiliser and rate of stocking on the seasonal pasture production of perennial ryegrass-subterranean clover pasture
Authors: Cayley J. W. D. , Hannah M. C. , Kearney G. A. , Clark S. G.
Published: August 2004

The response of pastures based on Lolium perenne L. and
Trifolium subterraneum L. to single superphosphate was
assessed at Hamilton, Victoria, by measuring the growth of pastures during
winter, spring, and summer over 7 years from 1979 to 1987. The seasons were
defined by the pattern of pasture production, rather than by calendar months.
Winter was the period of constant growth rate following the autumn rain;
spring was the period of accelerating growth rate until growth rate changed
abruptly following the onset of dry summer weather. Pastures were grazed with
sheep at a low, medium, or high grazing pressure, corresponding generally to
stocking rates of 10, 14, or 18 sheep/ha. At each level of grazing
pressure, single superphosphate was applied at 5 rates from 1979 to 1982; the
highest rate, expressed as elemental phosphorus (P), was reduced from 100 to
40 kg/ha during this time. In addition there was an unfertilised
treatment. In 1984, fertiliser was applied at 6 rates from 4 to 40 kg
P/ha. No fertiliser was applied in the remaining years, including 1983.
Pasture production was measured from 1979 to 1982 and from 1985 to 1987.
Total pasture dry matter (DM) accumulation per year at the highest stocking
rate was less than the other treatments in 4 of the years. Averaged over all
years and fertiliser treatments, the annual net production was 10·1,
10·1, and 9·0 t DM/ha (P <
0·05) for plots grazed at low, medium, and high stocking rates,
respectively. The amount of fertiliser required to reach a given proportion of
maximum yield response did not vary between winter and spring in any year, but
the greater potential yield in spring (P < 0
·001) meant that as more fertiliser was applied, the disparity between
pasture grown in winter and pasture grown in spring increased. Differences in
this disparity between extreme levels of P ranged from 1·4 t DM/ha
in a drought to about 7 t DM/ha in a good season.
The implications for managing farms when pastures are fertilised at higher
rates than currently practised by district farmers are that systems of animal
production with a requirement for plentiful good quality pasture in spring,
such as ewes lambing in spring, should be used. The benefit of spring lambing
over autumn lambing was supported when the 2 systems were compared over 26
years using the GrassGro decision support system. Well fertilised pasture
systems will also allow more scope for conserving pasture as hay or silage,
and increase opportunities for diversification in the farming enterprise, such
as spring-growing crops.
Occurrence of alfalfa mosaic, clover yellow vein, subterranean clover red leaf, and white clover mosaic viruses in white clover throughout Australia
Authors: Norton M. R. , Johnstone G. R.
Published: August 2004

The levels of infection with 4 viruses in young white clover
(Trifolium repens L.) plots sown in 1991 or 1992 were
monitored at a total of 17 sites across the 6 States of Australia. Tests were
undertaken for alfalfa mosaic (AMV), clover yellow vein (ClYVV), subterranean
clover red leaf (SCRLV) (syn. soybean dwarf), and white clover mosaic (WClMV)
viruses on field samples of 17 different cultivars, plus a local naturalised
ecotype at each location, twice yearly over 3 years. The tests were undertaken
using double antibody sandwich enzyme-linked immunosorbent assay (DASELISA).
AMV and WClMV were the most common and widespread viruses. They infected
plants atmany sites soon after establishment and then rapidly increased to
high levels, occasionally exceeding 90% of plants. In contrast, at some
sites, no infection with these viruses was detected. Analysis of the infection
data at 4 sites, where significant spread of AMV occurred, indicated that the
epidemics developed like compound interest models. Tests for SCRLV were done
only in 1994 when moderate levels of infection were found at most southern,
winter-rainfall dominant sites. The occurrence o fClYVV was sporadic and
infection levels were always low.