bluuebunny/crossref_metadata_2025 huggingface dataset:
Dark leaf spot (Alternaria brassicicola) on Chinese cabbage: temporal spread and its influencing factors
Authors: Chen L. Y. , Price T. V.
Published: March 2003

Temporal spread of dark leaf spot on Chinese cabbage was studied in experimental plots for 2 years. The effect of row orientation, the orientation of inoculated plants, and irrigation system on disease incidence and the effect of average wind direction on disease spread were investigated. A line source of inoculum in each plot was used for the 1993–94 summer and the 1994 spring–summer field trials, and 3 line sources for a 1995 autumn field trial. Disease progressed more rapidly in the 1993–94 summer than in the 1995 autumn. Disease epidemic did not develop in the 1994 spring–summer when environmental conditions were unfavourable. Disease incidence was higher in plots with row orientation parallel to the average wind direction than in plots with row orientation at right angles to the average wind direction for both the 1993–94 summer and the 1995 autumn trials. In summer 1993–94, across-row inoculation resulted in higher disease incidence than row inoculation did. No difference in disease incidence occurred between channel irrigation and overhead irrigation plots. Secondary infections always occurred adjacent to the source of inoculum and disease spread was influenced by the prevalent wind direction.
Defoliation of wall barley under sub-humid Mediterranean conditions
Authors: El-Shatnawi Moh'd Khair J. , Al-Qurran Louy Z. , Ereifej Khalil I. , Turk Munir
Published: March 2003

Wall barley (Hordeum�murinum) is a winter annual, native to Europe and the southern Mediterranean region. It can be used to establish permanent pasture in semi-arid rangeland. The crude protein content and response of wall barley to time of defoliation were investigated during 2 growing seasons in the northern mountains of Jordan. Field trials were conducted in the 1999–2000 and 2000–2001 growing seasons in Samta (32�23′N, 35�50′E) at an elevation of 1043 m. The highest crude protein content (P < 0.05) of 24.8% was recorded on 28 February and it thereafter declined gradually to reach the lowest values (4%) at maturity. The fiber content gradually increased and peaked (56.0%) when the plants reached maturity. Clipping plants on 28 February and 15 March produced shorter plants but encouraged tillering. Oven-dry shoot weights of individual plants and the population showed similar responses to time of defoliation during both years. Clipping the individuals on 28 February (8.1 and 4.7 g/plant, in respective years) and 15 March (8.2 and 4.6�g/plant, respectively) did not reduce the plant shoot weight. Forage amounts produced when plants were clipped�on 28�February and 15 March were similar to the amounts of forage produced from unclipped plants (1816 and 959�kg/ha, respective years). Clipping plants on 30 March and 15 April inhibited seed production. Defoliation during the early vegetative stage optimised seed yield and forage quantity and quality.
Variability within Kabatiella caulivora Race 1 and Race 2 revealed by cultural and molecular analyses
Authors: Bayliss K. L. , Spindler L. , Lagudah E. S. , Sivasithamparam K. , Barbetti M. J.
Published: March 2003

Kabatiella caulivora is the causal agent of clover scorch, a fungal disease of clover (Trifolium) species. Variability within and between K. caulivora Race 1 and Race 2 was determined by cultural characteristics, isozymes, and amplified fragment length polymorphisms (AFLP). Cultural studies indicated isolates from both races were highly variable. No differences were identified within or between races by isozyme analysis. Similarity coefficients, determined from AFLP analysis, indicated that isolates from different races were often more similar than isolates from the same race. Comparison of single representative isolates from Race 1 and Race 2, collected at a Denmark (Western Australia) disease site, with isolates collected from another site of clover scorch outbreak at Esperance, 300 km east of Denmark, indicated most of the isolates causing the second outbreak were similar to Race�2, confirming previously conducted pathogenicity tests. It is hypothesised that Race 2 may have evolved from Race 1, and that the level of variability in the pathogen indicates the potential for development of further new races of K. caulivora. The requirement for improved selection strategies, including the screening of new cultivars and breeding lines with multiple isolates of the pathogen, is discussed in relation to these findings.
Initial studies of the growth, nitrogen sequestering, and de-watering potential of perennial grass selections for use as nitrogen catch crops in orchards
Authors: Stork P. R. , Jerie P. H.
Published: March 2003

Two field trials were established to evaluate the ability of perennial grasses to recoup leaching losses of nitrogen in orchards. A perennial grass was considered suitable for use in orchards if it had a winter active–summer dormant growth cycle. High winter growth would ensure de-watering of the soil profile and nitrate uptake during this period, when an orchard is most vulnerable to leaching losses of nitrate. Low growth in summer would minimise competition for water and nutrients with fruit trees. These traits were studied in 14 varieties of grasses from 8 species in an open field and in an established apricot orchard. Semi-dormant summer growth was observed in species such as Dactylis glomerata L. cv. Kasbah, and Festuca arundinacea L. cv. MK88931. In the open field trial, the sequestration of NO3–-N + NH4+-N between late autumn and early spring, by Kasbah and MK88931, was estimated at 172 and 220 kg N/ha, respectively. Kasbah and MK88931 also demonstrated the driest soil profiles to a depth of 1.5 m in this period. This reflected their high water use and de-watering potential. Therefore, the performance of these grasses demonstrated a model approach to mitigate nitrate leaching below orchard root-zones. They could minimise deep percolation of rainfall and sequestered large amounts of inorganic nitrogen in soil during winter, whilst producing low growth during summer.
Early-maturing spring wheat outperforms late-maturing winter wheat in the high rainfall environment of south-western Victoria
Authors: Riffkin P. A. , Evans P. M. , Chin J. F. , Kearney G. A.
Published: March 2003

The aim of this experiment was to identify suitable cultivars and sowing times for winter and spring wheat types in the high rainfall environment of south-western Victoria. Spring and winter wheat cultivars with a range of flowering times were sown at 3 (April–June) and 6 (April–September) sowing times in 1997 and 1999, respectively, at Hamilton. Strong cultivar × sowing time interactions occurred. Grain yields ranged from 0.3 t/ha for a winter wheat (cv. Declic) sown in September to 8 t/ha for a spring wheat (cv. Silverstar) sown in June. The early-maturing spring wheat cultivar Silverstar, initially bred for the lower rainfall Mallee environment, produced the highest yields in both years from all sowing times except April. Our data indicate that higher yields are achieved from crops that flower earlier than is currently recommended. The optimum flowering period in south-western Victoria needs to be redefined, especially since many crops are now sown on raised beds.
Genetic and phenotypic characterisation of animal, carcass, and meat quality traits from temperate and tropically adapted beef breeds.
Authors: Johnston D. J. , Reverter A. , Burrow H. M. , Oddy V. H. , Robinson D. L.
Published: March 2003

A total of 7622 cattle were measured for several weight and body composition traits in temperate and tropically adapted breeds. Traits included: liveweight, hip height, body fat score, muscle score, flight time, ultrasound scanned fatness, and eye muscle area. Measurements were taken at 3 stages during the project: post-weaning, start of finishing, and end of finishing (i.e. pre-slaughter). Animals were finished to 3 target market-weight end-points (220, 280, or 340 kg carcass weight), either on pasture or in a feedlot, and in 2 different geographic regions for tropically adapted breeds. These data were used to estimate genetic parameters for the traits at each stage, and also to estimate the effect of market weight and finishing regimes on the phenotypic and genetic expression of each trait measured at the end of finishing stage. Results showed, for all traits, that the magnitude of the phenotypic expression increased across the stages and market-weight end-points for the end of finishing measures. Feedlot finishing decreased the age at slaughter, and increased fatness and muscling compared with pasture-finished animals. Heritabilities ranged from 0.13 to 0.58, with subjectively scored traits generally being lower than objectively measured traits. Additive genetic variances generally increased with stage of measurement, and with increasing market weight. Genetic correlations of the same measure across stages or market weights were all close to unity. Additive genetic variances of the various traits were similar for feedlot versus pasture finish groups, and the genetic correlation between each measure for feedlot and pasture finish was generally greater than 0.80. The effect of finishing geographic region (i.e. temperate versus subtropical environments) for the tropically adapted breeds had little effect on the size of the additive genetic variances or genetic correlations between traits across geographic regions.The results imply that changing the production system had a significant impact on the phenotypic expression of growth and body composition traits but little effect on the underlying genetic expression and subsequent ranking of sires (i.e. no evidence of genotype by production environment interactions). Therefore, these live animal measures could be used as selection criteria in genetic evaluation programs and may also be genetically correlated with abattoir carcass and meat quality traits.
Genetic and phenotypic characterisation of animal, carcass, and meat quality traits from temperate and tropically adapted beef breeds. 4. Correlations among animal, carcass, and meat quality traits
Authors: Reverter A. , Johnston D. J. , Ferguson D. M. , Perry D. , Goddard M. E. , Burrow H. M. , Oddy V. H. , Thompson J. M. , Bindon B. M
Published: March 2003

Beef cattle data from temperate (TEMP, n = 3947) and tropically (TROP, n = 4137) adapted breeds were analysed to compute estimates of genetic and phenotypic correlations between animal, abattoir carcass, and meat quality measures. Live animal traits included: liveweight (S2LWT), scanned subcutaneous rump fat depth (S2P8), scanned eye muscle area (S2EMA), flight time (S1FT), and finishing average daily gain (FADG). Carcass traits included: hot carcass weight (CWT), retail beef yield percentage (RBY), intramuscular fat percentage (IMF), subcutaneous rump fat depth (P8), eye muscle length by width (ELW), and meat colour score (MEATC). Meat quality measures taken on 2 muscles [M. longissimus thoracis et lumborum (LTL) and M. semitendinosus (ST)] included: shear force of LTL (LTL_SF) and ST (ST_SF); compression of the ST (ST_C); cooking loss % of the LTL (LTL_CL%) and ST (ST_CL%); Minolta LTL L* (LTL_L*), a* (LTL_a*), ST a* (ST_a*); and consumer-assessed LTL tenderness score (LTL_TEND). Genetic and phenotypic correlations between animal measures and related carcass traits were moderate to very high for TEMP and TROP. Genetic correlations between S2LWT and CWT were 0.89 and 0.82, between S2P8 and P8 0.80 and 0.88, and between S2EMA and ELW 0.62 and 0.68, for TEMP and TROP, respectively. Genetic correlations between animal measures and other carcass traits varied; moderate genetic correlations were estimated between S2P8 and RBY (–0.57, –0.19 for TEMP, TROP) and S2P8 and IMF (0.39, 0.23 for TEMP, TROP). Genetic correlations between animal and meat quality measures were moderate to low. For TEMP, moderate genetic correlations were estimated between S2P8 and LTL_TEND (0.38), FADG and ST_a* (–0.49), and FADG and LTL_TEND (0.45); and for TROP, S1FT and LTL_SF (–0.54), and S2EMA and LTL_L* (–0.46). Phenotypic correlations between animal and meat quality were generally low and close to zero. Several moderate to high genetic correlations existed between carcass and meat quality traits. In general, fatness measures were genetically correlated with tenderness (e.g. IMF and LTL_TEND 0.61, 0.31 for TEMP, TROP). CWT was genetically correlated with meat colour (CWT and LTL_L* 0.66, 0.60 for TEMP, TROP) and objective tenderness measures (CWT and ST_C –0.52, –0.22 for TEMP, TROP). Once again phenotypic correlations between carcass and meat quality were low, indicating that few phenotypic predictors of meat quality traits were identified. Several of the genetic correlations show that both animal and abattoir carcass traits may be of use as indirect measures for carcass and meat quality traits in multiple trait genetic evaluation systems.
Alkaloids of the sorghum ergot pathogen (Claviceps africana): assay methods for grain and feed and variation between sclerotia/sphacelia
Authors: Blaney B. J. , Maryam R. , Murray S-A. , Ryley M. J.
Published: March 2003

Assay methods for the alkaloids of sorghum ergot (Claviceps africana) are described and compared. Sorghum ergot bodies (sclerotia/sphacelia) from various regions of Queensland and New South Wales were collected in 1997 and 2001 and assayed by spectrophotometry, thin layer chromatography, or high performance liquid chromatography (HPLC). All contained dihydroergosine (DHES) as the main alkaloid component (about 80%), with smaller amounts of dihydroelymoclavine and festuclavine. The preferred method of assay for infected sorghum and mixed feeds involved extraction into dichloromethane:methanol:ethyl acetate:ammonium hydroxide (50:5:25:1) using an ultrasonic bath. After solvent removal, the extract was dissolved in diethyl ether and partitioned into 0.5 M hydrochloric acid. After adjusting the pH to 8–10 with ammonium hydroxide, the alkaloids were extracted into dichloromethane, the solvent evaporated, and the residue dissolved in methanol. HPLC separation was on a C18 column, 150 × 3.9 mm, run isocratically at 40�C, with acetonitrile:0.1% ammonium acetate:methanol (31:50:20) as the mobile phase. Detection was either by UV at 280 nm or by fluorescence with excitation at 235 nm and absorbance at 340 nm. Levels of quantitation for DHES in sorghum approached 0.1 mg/kg (UV) and 0.01 mg/kg (fluorescence). Method recoveries for DHES in the range of 0.025–7 mg/kg averaged 75%. The total alkaloid content of ergot bodies (sclerotia/sphacelia) from different batches of grain varied from 100 to 7900 mg/kg (0.79%). Within batches, there was much less variation in the alkaloid content of ergot bodies, but larger ergots tended to contain more alkaloid than smaller ergots, and those infected with Cerebella species contained even less; this probably related to the ratio of sclerotial/sphacelial tissue present. Honeydew also contained DHES (1–10 mg/kg) and might contaminate clean grain at significant levels. Tests on 4 farms showed that substantial amounts of ergot bodies and alkaloids were removed during grain harvesting.
Grain weight and malting quality in barley as affected by brief periods of increased spike temperature under field conditions
Authors: Passarella Valeria S. , Savin Roxana , Slafer Gustavo A.
Published: March 2003

High temperature is usually one of the most important stresses during grain filling affecting both yield and quality in barley crops. In the present study, an attempt was made to assess in the field the effects of short periods of high temperature, using transparent boxes covering only the spikes, with thermostatically controlled electric resistance for increasing the temperature. Treatments consisted of 2 malting cultivars and 5 heat treatments of high temperatures (8�C above the environmental temperature for 6 h/day for 5 consecutive days) over different periods during grain filling. Final grain weight was reduced by 2–14%, depending on the timing of heat stress and the genotype. There was a significant increase in grain nitrogen percentage in both cultivars, and grain β-glucans decreased with high temperatures in Logan and were unchanged in Beka. The resulting malt extract was reduced with exposure to high temperatures, depending on the cultivar, implying that even mild heat stress may change malting performance.
Sources of variation in n-alkane concentrations in the cuticular wax of two species of pasture plants
Authors: Lee G. J. , Nolan J. V.
Published: March 2003

Samples of white clover and ryegrass were collected from 8 sites within an irrigated pasture (40 ha) to determine the extent of variation in the concentrations of individual alkanes (C25–C33) between sites, between samples (within site), and within a sample (duplicate analysis). Across both species, between-site variation accounted for 10–35% of the total variation in the concentration of the individual alkanes. There was significant variation between sites in the concentrations of the alkanes C27, C28, and C33 in ryegrass only. Between-sample (within site) variation was significant for most alkanes in both species, accounting for 50–70% of the total variation within white clover and 39–59% within ryegrass. Within the white clover samples, the within-sample repeatability (an indicator of analytical variation) was 0.64 or greater for alkanes present in moderate to high quantities. However, within the ryegrass samples the analytical repeatability was low for all but the C25 (0.71) and C27 (0.62) alkanes. The effects of within-species variation on the estimation of botanical composition of herbage and faecal samples collected from extensive grazing systems are discussed.
Performance of purebred and crossbred rabbits in Australia: Individual growth and slaughter traits
Authors: Prayaga K. C. , Eady S. J.
Published: March 2003

Data from 3 rabbit breeds, namely New Zealand White (N), Californian (C), and Flemish Giant (F), and their crosses, i.e. CN, FN, F(CN), and C(FN), were analysed for individual growth traits such as body weights at 5 (5WT), 6 (6WT), 7 (7WT), 8 (8WT), 9 (9WT), and 10 (10WT) weeks of age, and post-weaning average daily gain between 5 and 10 weeks of age (ADG), and individual slaughter traits such as liveweight at slaughter (SW), carcass weight (CW), and dressing percentage (DP). Data included records for individual body weights from 1345 to 1524 rabbits from 279 litters and records for slaughter traits from 919 rabbits from 245 litters. Significant sources of variation for individual growth and slaughter traits were breed, parity, month-year of birth, sex, and number weaned per litter (NW). However, parity and NW did not significantly affect ADG and DP. Slaughter traits were not significantly affected by sex. The overall least squares means for 5WT, 6WT, 7WT, 8WT, 9WT, 10WT, ADG, SW, CW, and DP were 836 g, 1021 g, 1215 g, 1390 g, 1577 g, 1791 g, 27.2 g/day, 2.28 kg, 1.23 kg, and 53% respectively. N and F purebred, and FN crossbred rabbits performed significantly (P < 0.05) better than C purebred and crossbreds [CN and C(FN)] in all the individual growth and slaughter traits except for DP. CN performed better (P�<�0.05) in DP than all other crosses. ADG of C rabbits was significantly (P < 0.05) lower than of all other crosses under study, with F(CN), C(FN), and CN crosses showing intermediate growth rates. Significantly (P < 0.05) higher growth rates were observed in N, F, and FN breeds. There was no significant heterosis observed in the breed crosses for any traits under study. Individual body weights at 5–10 weeks of age were significantly lower in the 1st parity born rabbits than in other higher parity born rabbits. SW and CW were significantly higher in 2nd and 3rd parity rabbits than in 1st and 4th and later parity born rabbits. Female rabbits achieved heavier weights at 5, 6, and 7 weeks of age than males and males weighed more than females after 7 weeks of age. ADG of males was significantly (P�<�0.05) higher than of females. Significant negative regression coefficients of NW on all individual body weights until slaughter age showed that larger litters had lighter rabbits. Coefficient of variation for individual growth and slaughter traits ranged between 11.1 and 20.7%. Common litter variance explained a significantly large proportion of total phenotypic variance, with the proportions ranging between 0.36 and 0.55 for individual growth traits, 0.46 for SW, and 0.35 for CW.
Macadamia responses to mild water stress at different phenological stages
Authors: Stephenson R. A. , Gallagher E. C. , Doogan V. J.
Published: March 2003

Mild water stress was imposed on bearing macadamia trees in through-draining lysimeters at various phenological stages. Water was withheld until a xylem water potential (Ψx) of –1.5 to 2.0 MPa was reached, this being maintained by partial water replenishment at 2-day intervals. Flowering, nut set, nut development, yield, and quality responses were assessed to identify critical, stress-sensitive stages. Stress during nut maturation was particularly detrimental to both yield and quality, although stress during floral development and the premature nut drop also had adverse effects. Low yields were due to reduced nut number and smaller nuts. Lower photosynthesis (c. 2 μmol CO2/m2.s) at –1.5 MPa would account for reduced yield and poorer quality during nut maturation when energy demands of active oil accumulation are high. Stress at floral initiation was generally not detrimental.Overall, stress restricted growth. The rate of girth growth was significantly lower when stress was applied during the dormant floral initiation stage. When stress coincided with normal periods of vegetative growth, flushing was delayed until after re-watering when greater foliage production was stimulated. Judiciously imposing mild stress may be used to manipulate macadamia phenology, although it may not necessarily conserve water. Further refinement would be needed to develop stress manipulation as a practical and reliable management tool to achieve higher yields. Water should be applied to alleviate stress during critical stages of nut development and maturation. Mild stress after the current crop is mature, however, is unlikely to be detrimental to macadamia yield or quality. It may, in fact, be beneficial through manipulation of flushing patterns that influence yield.
Responses of broilers at moderate or high temperatures to dietary arginine:lysine ratio and source of supplemental methionine activity
Authors: Chen J. , Hayat J. , Huang B. , Balnave D. , Brake J.
Published: March 2003

Recent studies have shown that the relative feed intake (FI) and bodyweight gain (BWG) responses of chronically heat-stressed broilers to equimolar additions of DL-methionine (DLM) or 2-hydroxy–4-(methylthio) butanoic acid (HMB; Alimet) can be altered by changing the arginine:lysine (arg:lys) ratio of the diet. However, no information is available concerning responses of broilers during acute heat stress. Broilers were exposed to either 22�C or 30�C during 3 consecutive 5-day experimental periods between 28 and 43 days of age. Responses to equimolar additions of the 2 sources of supplemental methionine activity were similar during exposure to 22�C at 28–33 days and 38–43 days of age. However, between 33 and 38 days of age, when the temperature was 30�C, increasing the dietary arg:lys ratio from 1.04 to 1.35 significantly improved the FI and BWG of broilers fed HMB, but not DLM. At an arg:lys ratio of 1.35, the BW gain of broilers fed HMB was significantly greater than that of broilers fed DLM. Therefore, under acute heat stress conditions the choice of a supplemental source of methionine activity should be dependent upon the dietary arg:lys ratio.
The tolerance of three transgenic subterranean clover (Trifolium subterraneum L.) lines with the bxn gene to herbicides containing bromoxynil
Authors: Dear B. S. , Sandral G. A. , Spencer D. , Khan M. R. I. , Higgins T. J. V.
Published: March 2003

A bxn gene, coding for the nitilase enzyme that catalyses the detoxification of the herbicide bromoxynil, was inserted into subterranean clover (Trifolium subterraneum L. subsp. yanninicum). The agronomic characteristics of 3 transgenic lines (BXN 5, 7, 10) and their response to herbicides containing bromoxynil, were compared with that of the non-transgenic parent, cv. Gosse, in 1 glasshouse and 2 field experiments.The application of bromoxynil at 1.5 L/ha resulted in a 50% reduction in the spring herbage yield of the non-transgenic control but no reduction in BXN 5 and 7. The level of the phyto-oestrogens, genistein and biochanin A, in the leaf tissue were low in Gosse and the 2 transgenic lines, BXN 7 and 10, but the level of genistein increased significantly (P < 0.05) from 0.85% in Gosse to 1.43% dry weight in BXN 5, and biochanin A increased from 0.35% in Gosse to 0.73% in BXN 5. The application of the herbicides bromoxynil, bromoxynil+MCPA, and Jaguar (bromoxynil+diflufenican) at the cotyledon stage in a glasshouse study significantly reduced the leaf area of the non-transgenic Gosse, but did not reduce the leaf area of the 3 transgenic lines. When applied at the 4–5 leaf stage, the leaf area of Gosse was again reduced by all the herbicides, but only the bromoxynil+MCPA treatment reduced the leaf area of the transgenic lines relative to the control. The application of bromoxynil or Jaguar at the 4–5 leaf stage depressed the herbage yield of Gosse by about 62% compared with 0–24% in the 3 transgenic lines. In the field studies, BXN 5 and 10 had similar seed yields to Gosse in the absence of herbicide application, but the seed yield of BXN 7 was significantly less than the other 2 transgenic lines. The level of hard-seed in BXN 7 was also lower at 25% compared with 55–57% in the other transgenic lines and Gosse.These findings stress the need to carefully assess the agronomic qualities of transgenic lines prior to release as although tolerance to bromoxynil may be greatly increased by the bxn gene, other important agronomic characteristics, such as seed yield, hardseededness, and isoflavone content, may change as result of the gene or transformation process.
Corrigendum to: 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: March 2003

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.
An Optical Design for an Antarctic 2 m Telescope with a Near IR Imager
Authors: Gillingham P. R.
Published: March 2003

A study has been made of the optical performance to be expected from an Antarctic Ritchey Chrétien telescope with a 2 m diameter primary mirror imaging directly onto a detector array in the K and L infrared windows. Near diffraction limited performance is provided across a flat 30 arcmin diameter field by compensating the astigmatism and field curvature with a meniscus lens which also serves as the Dewar window. With baffling inside and Narcissus mirrors outside the Dewar, extraneous radiation can be kept to a low level.
The Potential of Differential Astrometric Interferometry from the High Antarctic Plateau
Authors: Lloyd James P. , Oppenheimer Ben R. , Graham James R.
Published: March 2003

The low infrared background and high atmospheric transparency are the principal advantages of Antarctic Plateau sites for astronomy. However, the poor seeing (between 1 and 3 as) negates much of the sensitivity improvements that the Antarctic atmosphere offers, compared to mid-latitude sites such as Mauna Kea or Cerro Paranal. The seeing at mid-latitude sites, though smaller in amplitude, is dominated by turbulence at altitudes of 10–20 km. Over the Antarctic Plateau, virtually no high altitude turbulence is present in the winter. The mean square error for an astrometric measurement with a dual-beam, differential astrometric interferometer in the very narrow angle regime is proportional to the integral ofh2C2N(h). Therefore, sites at which the turbulence occurs only at low altitudes offer large gains in astrometric precision. We show that a modest interferometer at the South Pole can achieve 10 μ as differential astrometry 300 times faster than a comparable interferometer at a good mid-latitude site, in median conditions. Science programs that would benefit from such an instrument include planet detection and orbit determination, and astrometric observation of stars microlensed by dark matter candidates.
MASTER: A Triple Heterodyne Receiver for Astronomy in the Millimetre and Submillimetre Domain
Authors: Battistelli E. , Zannoni M. , Boella G. , Gervasi M. , Passerini A. , Sironi G. , Andreone D. , Brunetti L. , Lacquaniti V. , Maggi S. , Steni R. , Natale E. , Thorpe J. R.
Published: March 2003

A progress report of the MASTER project is presented here. MASTER is a system of three heterodyne receivers based on SIS (superconductor–insulator–superconductor) tunnel junction mixers. In our instrument these mixers will allow direct down-conversion from 94, 225, and 345 to 1.5 GHz, the IF where the signal will be detected. This instrument, coupled to a 2–4 m telescope like the one proposed for the DOME C base in Antarctica and in conjunction with an Acusto Optical Spectrometer, can be used to detect emission lines associated with molecular clouds in the interstellar medium. The current status of a 94 GHz receiver, the prototype of MASTER, will be presented too. The study of the optical coupling between the receiver and MITO telescope in the Italian Alps will also be described.
Polarimetry of the Cosmic Microwave Background from the Antarctic Plateau
Authors: Sironi G. , Battistelli E. , Boella G. , Cavaliere F. , Gervasi M. , Passerini A. , Spiga D. , Zannoni M.
Published: March 2003

Detection of linear polarisation at a level of 1 ppm or less, associated to the anisotropy of the cosmic microwave background, will confirm the cosmological origin of the observed anisotropy and provide information on the thermal history of the universe between the recombination epoch and now. In particular, detection of polarisation can help in deciding if the evolution of the universe included a reionisation epoch. We present the Mk3 model of our correlation polarimeter, an improved version of a system which has already been used for observations of the region of sky around the South Celestial Pole from Antarctica (in 1994 at Terra Nova Bay and in 1998 at Dome C).
The IRAIT Project
Authors: Busso M. , Tosti G. , Persi P. , Ferrari-Toniolo M. , Ciprini S. , Corcione L. , Gasparoni F. , Dabalá M.
Published: March 2003

We present the status of the project IRAIT (the Italian Robotic Antarctic Infrared Telescope) that will be hosted at Dome C in the Italo-French Concordia station. We review the main scientific motivations of the effort, and describe the characteristics of the telescope, which has been completed and is now under test at the Coloti-Montone site operated by the University of Perugia. Then we describe the design of the mid-IR camera that is under construction, showing some examples of the applications on the basis of the twin instrument TIRCAMII, now operating at the Italian Infrared Telescope TIRGO.
A Catalogue of Damped Lyman Alpha Absorption Systems and Radio Flux Densities of the Background Quasars
Authors: Curran S. J. , Webb J. K. , Murphy M. T. , Bandiera R. , Corbelli E. , Flambaum V. V.
Published: March 2003

We present a catalogue of the 322 damped Lyman alpha absorbers taken from the literature. All damped Lyman alpha absorbers are included, with no selection on redshift or quasar magnitude. Of these, 123 are candidates and await confirmation using high resolution spectroscopy. For all 322 objects we catalogue the radio properties of the background quasars, where known. Around 60 quasars have radio flux densities above 0.1 Jy and approximately half of these have optical magnitudes brighter than V = 18. This compilation should prove useful in several areas of extragalactic/cosmological research.
A Spectral Line Survey of IRAS 17470-2853 from 86.1 to 92.1 GHz
Authors: Kim Hun-Dae , Balasubramanyam Ramesh , Burton Michael G.
Published: March 2003

We present results from a spectral line survey of the young stellar object IRAS 17470-2853, undertaken to examine chemical changes during the evolution from hot molecular cores to ultracompact HII regions. Observations were carried out with the Mopra 22 m radio telescope in the frequency range from 86.1 to 92.1 GHz. A total of 21 lines from 9 molecules were detected. Except for CH3CN they are all simple molecules. We compare the results to the ultracompact HII region G34.3+0.15, where spectral line surveys in the frequency range 80–115 GHz and 330–360 GHz have been performed. While the molecular lines detected are similar, their widths and intensities are somewhat narrower and lower, respectively, in IRAS 17470-2853. The typical line width of ˜5 km s−1 indicates relatively quiet or quasi-thermal emission. On the other hand, a significant difference in TA* (HNC)/TA*(HCN) has been found: 0.8 for IRAS 17470-2853 compared to 2.6 for G34.3+0.15. The broad line width of SiO (υ=0, J=2–1), ˜9 km s−1, suggests that IRAS 17470-2853 is experiencing a shock generated by the embedded object. Column densities, or lower limits to them, are derived for observed molecules.
Powerful Water Masers in Active Galactic Nuclei
Authors: Maloney Philip R.
Published: March 2003

Luminous water maser emission in the 616–523 line at 22GHz has been detected from two dozen galaxies. In all cases the emission is confined to the nucleus and has been found only in AGN, in particular, in Type 2 Seyferts and LINERs. I argue that most of the observed megamaser sources are powered by X-ray irradiation of dense gas by the central engine. After briefly reviewing the physics of these X-Ray Dissociation Regions, I discuss in detail the observations of the maser disk in NGC 4258, its implications, and compare alternative models for the maser emission. I then discuss the observations of the other sources that have been imaged with VLBI to date, and how they do or do not fit into the framework of a thin, rotating disk, as in NGC 4258. Finally, I briefly discuss future prospects, especially the possibility of detecting other water maser transitions.
A Search for the Potentially Hazardous Asteroid 1998 OX4: Implications for a Possible Close Encounter in 2014
Authors: Biggs James D. , Slivkoff Matthew
Published: March 2003

Small bodies of 100–500 m diameter can cause significant damage on impact with the Earth. Such objects are difficult to detect and track because they are intrinsically faint over most of their orbit. We failed to detect one such lost and potentially hazardous minor planet, 1998 OX4, during two observing sessions in 2001, January. The positions searched were those calculated by Milani et al. (2000) with their Virtual Impactors method. Using some simple assumptions we estimate the probability that we failed to detect 1998 OX4 due to it being obscured by objects in the field of our observations is <2 × 10−7. If the assumptions in the Virtual Impactor model are valid we conclude that an impact with 1998 OX4 is unlikely in 2014, January. Furthermore, given the relatively large area we searched it is also unlikely that this minor planet will have a very close encounter with Earth in 2014.
Photometric Techniques Using Small College Research Instruments for Study of the Extrasolar Planetary Transits of HD 209458
Authors: Hudgins David W. , Filipović Miroslav D.
Published: March 2003

We present the results of a program to develop techniques that enable high-resolution photometric measurements using modest research instruments available to small colleges, and then demonstrate those techniques in a pilot photometric project.

Using a 25 cm Schmidt–Cassegrain telescope and SBIG ST7E CCD camera, we develop techniques that enabled milli-magnitude photometric resolution. The pilot project studied five transits of the recently discovered gas giant planet orbiting HD 209458. We measured a flux drop of 1.46 ± 0.17% during the transit which corresponds to a planetary diameter of 1.39 ± 0.14 RJup, a transit period of 2h 48min ± 21min, and planet orbital inclination of 87.6 ± 1.3°. We determined the orbital period as 3.5234 ± 0.0026 days. These results agree well with other studies which used professional grade research instruments. We suggest a number of other challenging photometric research areas suitable for graduate and undergraduate investigation using equipment common to many small colleges.
Factors Determining Variability Time in Active Galactic Nucleus Jets
Authors: Protheroe R. J.
Published: March 2003

The relationship between observed variability time and emission region geometry is explored for the case of emission by relativistic jets.The approximate formula for the jet-frame size of the emission region, R′ = DcΔtobs, is shown to lead to large systematic errors when used together with observed luminosity and assumed or estimated Doppler factor D to estimate the jet-frame photon energy density. These results have implications for AGN models in which low-energy photons are targets for interaction of high energy particles and photons, e.g. synchrotron-self Compton models and hadronic blazar models, as well as models of intraday variable sources in which the photon energy density imposes a brightness temperature limit through Compton scattering.

The actual relationship between emission region geometry and observed variability is discussed for a variety of geometries including cylinders, spheroids, bent, helical and conical jet structures, and intrinsic variability models including shock excitation. The effects of time delays due to finite particle acceleration and radiation timescales are also discussed.
The Internal Extinction Curve of NGC 6302 and its Extraordinary Spectrum
Authors: Groves Brent , Dopita Michael A. , Williams Robert E. , Hua Chon-Trung
Published: March 2003

In this paper we present a new method for obtaining the optical wavelength-dependent reddening function of planetary nebulae (PN), using the nebular and stellar continuum. The data used was a spectrum of NGC 6302 obtained using the Double Beam Spectrograph on the 2.3 m telescope at Siding Springs Observatory over three nights. This resulted in a spectrum covering a wavelength range 3300–8600 Å with a large dynamical range and a mean signal to noise of >102 Å−1 in the nebular continuum. With such a high S/N the continuum can be accurately compared with a theoretical model of nebular plus stellar continuum. The nebular electron temperature and density used in the model are determined using ratios of prominent emission lines. The reddening function can then be obtained from the ratio of the theoretical and the observed continuum. In the case of NGC 6302, it is known that much of the reddening arises from dust within or around the nebula, so that any differences between the measured reddening law and the 'standard' interstellar reddening law will reflect differences in the nebular grain size distribution or composition. We find that for NGC 6302, the visible to IR extinction law is indistinguishable from 'standard' interstellar reddening, but that the UV extinction curve is much steeper than normal, suggesting that more small dust grains had been ejected into the nebula by the PN central star. We have detected the continuum from the central star and determined its Zanstra temperature to be of order 150,000 K. Finally, using the extinction law that we have determined, we present a complete dereddened line list of nearly 600 emission lines, and report on the detection of the He(2–10) and He(2–8) Raman features at λ4331 Å and λ4852 Å, and the detection of Raman scattered O VI features at λ6830 Å and λ7087 Å. We believe this to be the first detection of this process in a PN.
Parameterising the Third Dredge-up in Asymptotic Giant Branch Stars
Authors: Karakas A. I. , Lattanzio J. C. , Pols O. R.
Published: March 2003

We present new evolutionary sequences for low and intermediate mass stars (1−6M⊙) for three different metallicities, Z = 0.02, 0.008, and 0.004. We evolve the models from the pre-main sequence to the thermally-pulsing asymptotic giant branch phase. We have two sequences of models for each mass, one which includes mass loss and one without mass loss. Typically 20 or more pulses have been followed for each model, allowing us to calculate the third dredge-up parameter for each case. Using the results from this large and homogeneous set of models, we present an approximate fit for the core mass at the first thermal pulse, Mc1, as well as for the third dredge-up efficiency parameter, λ, and the core mass at the first dredge-up episode, Mcmin, as a function of metallicity and total mass. We also examine the effect of a reduced envelope mass on the value of λ.
Millimetre Science with the Upgraded Australia Telescope
Authors: Wong T. , Melatos A.
Published: March 2003

A new astronomical window into the southern skies has been opened with the high-frequency upgrade to the Australia Telescope Compact Array (ATCA), which allows radio-interferometric mapping of sources at wavelengths as short as 3 mm. In anticipation of the upgrade's completion, a two-day workshop was held at the University of Melbourne in November 2001. The workshop covered a diverse range of fields, tied together by a common theme of identifying key areas where ATCA observations can have an impact. More than half of the talks were concerned with molecular clouds and star formation, with the remainder covering topics such as molecular gas in the Galactic Centre, Seyfert nuclei, and high-redshift objects. Some early results from the 3 and 12 mm prototype systems were also presented. In consultation with the speakers, we are presenting in this article a summary of the talks. The original slides are available from the ATNF website.
Molecular Masers in Variable Stars
Authors: Rudnitskij Georgij M.
Published: March 2003

When a star with a mass of one to a few solar masses enters the red giant stage of its evolution, the radius of its atmosphere reaches several astronomical units. Pulsational instability is typical for this stage. Most stars become Mira-type or semiregular variables with light cycles of a few hundred days. Red giants lose mass at a rate M = 10−7−10−5M⊙ yr−1. Extensive gas–dust circumstellar envelopes form. These envelopes contain various molecular species. Some of these molecules (OH, H2O, SiO, HCN) manifest themselves in maser radio emission. Data on the H2O maser variability and its connection with the stellar brightness variations are discussed. In the H2O line circumstellar masers can be divided into ‘stable’ (showing persistent emission — R Aql, U Her, S CrB, X Hya) and ‘transient’ (appearing in the H2O line once per 10–15 stellar light cycles — R Leo, R Cas, U Aur). Physical mechanisms of the maser variability are discussed. The most probable process explaining the observed visual–H2O correlation is the influence of shock waves on the masing region. Usually it is assumed that shocks in Mira atmospheres are driven by stellar pulsations. Here an alternative explanation is proposed. If a star during its main sequence life possessed a planetary system, similar to the solar system, the planets will be embedded in a rather dense and hot medium. Effects of a planet revolving around a red giant at a short distance (inside its circumstellar envelope) are discussed. A shock produced by the supersonic motion of a planet can account for the correlated variability of the Hα line emission and H2O maser. If the planetary orbit is highly eccentric, then the connected Hα–H2O flare episodes may be explained by the periastron passage of the planet. New tasks for the upgraded ATCA are discussed.
Operation of the Near Infrared Sky Monitor at the South Pole
Authors: Lawrence J. S. , Ashley M. C. B. , Burton M. G. , Calisse P. G. , Everett J. R. , Pernic R. J. , Phillips A. , Storey J. W. V.
Published: March 2003

The near infrared sky spectral brightness has been measured at the South Pole with the Near Infrared Sky Monitor (NISM) throughout the 2001 winter season. The sky is found to be typically more than an order of magnitude darker than at temperate latitude sites, consistent with previous South Pole observations. Reliable robotic operation of the NISM, a low power, autonomous instrument, has been demonstrated throughout the Antarctic winter. Data analysis yields a median winter value of the 2.4μm (Kdark) sky spectral brightness of ˜120μJy arcsec−2 and an average of 210 ± 80μJy arcsec−2. The 75%, 50%, and 25% quartile values are 270 ± 100, 155 ± 60, and 80 ± 30μJy arcsec−2, respectively.