bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduced growth and yield of wheat with conservation cropping. I. Field studies in the first year of the cropping phase
Authors: Kirkegaard JA , Angus JF , Gardner PA , Muller W
Published: November 2004

An experiment was conducted on a red earth at Harden, N.S.W., to investigate the effects of tillage and stubble management on the growth and yield of wheat in the first year of conservation cropping. Treatments involved stubble-management systems of incorporation, burning or retention combined with tillage systems of either direct drilling or minimum tillage. The experiment was conducted on an oat stubble of 3.9 t ha-1. Direct drilling and stubble retention both reduced seedling growth by 15%, compared to cultivated and stubble burnt treatments, but had no effect on plant density or tillering. The effects on shoot growth were additive and persisted until maturity, leading to grain yields which varied from 2.16 t ha-1 for the stubble-mulched, direct-drilled treatment to 3.20 t ha-1 for the burned-stubble, minimum-till treatment. Direct drilling reduced the total root length in the profile (0-160 cm) at anthesis by 40%, but there was no effect of stubble retention. Reduced shoot growth and rooting depth on direct-drilled and stubble-retained treatments reduced the recovery of water and mineral N by the crop and increased the leaching of mineral N below the root zone. Early shoot growth reductions on direct-drilled plots were not related to levels of soil water, mineral nitrogen (N) or soil temperature. Reduced shoot growth was associated with increased severity of Rhizoctonia in some direct drilled plots, but growth reductions often occurred in the absence of obvious symptoms. High soil strength (>2 MPa) in the top 10 cm of soil may have contributed to reduced growth, although the exact mechanism remains unclear. Reduced growth associated with the presence of stubble was not caused by immobilization of N or increased leaf disease, although reduced soil temperatures may have been partly responsible.
Effect of Brassica break crops on the growth and yield of wheat
Authors: Kirkegaard JA , Gardner PA , Angus JF , Koetz E
Published: November 2004

The effect of the Brassica crops, canola and Indian mustard, on the growth and yield of subsequent wheat crops was investigated in field experiments at four sites in southern New South Wales. In all experiments, shoot growth, root growth, disease incidence and water and nitrogen use of wheat following the Brassica crops were compared with wheat following wheat. Linseed and field peas were included as break crops at some sites for comparison. At one site, methyl bromide fumigation was used to investigate break crop effects in the absence of soil-borne pathogens. Growth improvements following break crops were evident at an early stage (4 leaf stage), but were not related to levels of soil mineral N or the incidence of plants affected by Gaeumannomyces graminis var. tritici (take-all) or Rhizoctonia solani. At two of the four sites, early vegetative growth was greater following Indian mustard than following canola. Treatment with methyl bromide led to increased vegetative growth of wheat following all crops, but the ranking of the break crop effect was maintained, with wheat growth after Indian mustard>canola>wheat. The average increase in shoot biomass at anthesis following the break crops was 29%, varying from 12 to 46% according to site and break crop species. The effect of break crops on grain yield was influenced by water availability after anthesis. At one site, where 89 mm of rain fell after anthesis, the early improvements in growth persisted until maturity, and yield was significantly improved following the break crops. At the other three sites, less than 20 mm of rain fell after anthesis, and the greater biomass of wheat following break crops resulted in rapid depletion of soil water. The increased water deficit during grain filling reduced grain size, and no yield benefit was observed. As a result of increased pre-anthesis growth, wheat following break crops accumulated more N at anthesis in above-ground biomass at all sites. This N was redistributed into the grain after anthesis resulting in an average increase of 1.5% in grain protein in wheat following break crops. At one site, the increased N uptake in the crop was associated with less mineral N remaining in the profile at harvest. The results indicate the potential for break crops to improve the yield and protein levels of subsequent wheat crops, although the magnitude of these effects is dependent on seasonal conditions. The nature of the early growth improvements remains uncertain. However, the results from two of the sites support a previous report of the superior break-crop effect of Indian mustard.
Effect of different direct drilling and conventional sowing techniques on soil strength, root growth and grain yield of wheat on sandplain soils in Western Australia
Authors: Schmidt CP , Belford RK , Tennant D
Published: November 2004

Experiments were conducted to compare different direct drilling and conventional sowing techniques, and describe the effects of these techniques on soil strength, root growth and grain yield of wheat on sandplain soils in the northern wheat-belt of Western Australia. Soil strength was identified as a critical factor affecting root growth; increasing the depth of soil loosening beneath seeding depth with a modified direct drill reduced soil strength relative to that found in the traditional direct drill treatments, and increased rooting density beyond the 10 cm soil depth. As loosening depth increased, there were increases in both shoot growth and grain yields, and water use efficiency also improved. Maximizing the depth of soil disturbance by deep ripping after sowing resulted in the highest grain yields, but the time and cost penalties associated with this tillage operation are substantial and likely to deter its routine use. Modifying a direct drill to loosen soil beneath sowing depth therefore combined the advantages of conventional direct drilling (timeliness, moisture conservation and lower risk of erosion), with those obtained by sowing after cultivation (improved root growth and yield) without the yield penalties associated either with direct drilling or delayed sowing on these soils.
Distribution of nitrogen and radiation use efficiency in peanut canopies
Authors: Wright GC , Hammer GL
Published: November 2004

The allocation pattern of leaf nitrogen throughout a crop canopy can theoretically affect crop photosynthetic performance and radiation use efficiency (RUE). No information is available on the existence of leaf nitrogen gradients in peanut (Arachis hypogaea L.) canopies, nor on how these gradients might impact on RUE. Peanut crops (cv. Tifton-8) were grown in warm and cool environments, and the canopy profiles of leaf area index, light interception, specific leaf weight (SLW), leaf nitrogen concentration (LNC) and specific leaf nitrogen (SLN) were examined at 73 and 112 days after planting. Crop RUE was also measured during this period. There was a marked decline in SLN from the top to the base of the canopy in both environments. The gradient in SLN occurred due to changes in SLW and LNC in the warm environment, but only due to changes in SLW in the cool environment. The gradient appeared to be largely controlled by the light environment within the canopy, as evidenced by the commonality (across environments) of the relationship between SLN and cumulative light interception throughout the canopy. Radiation use efficiency was 33% higher in the crop grown in the warm compared to the cool environment, suggesting that cool temperatures can limit RUE in peanut. For the crop at the warm site, RUE was 32% higher than the theoretical RUE assuming a uniform SLN distribution in the canopy. It is suggested that the existence of non-uniform SLN distribution in the canopy may allow enhanced RUE compared to canopies with uniform SLN distribution.
A theoretical analysis of nitrogen and radiation effects on radiation use efficiency in peanut
Authors: Hammer GL , Wright GC
Published: November 2004

Radiation use efficiency (RUE) of well-watered crops, measured as grams of biomass accumulated for each megajoule of intercepted total solar radiation, is affected by the level of leaf nitrogen in the canopy and has been related to the canopy specific leaf nitrogen (SLN; g N m-2 leaf area). A number of field experiments on peanut have measured RUE values greater than current theories predict on the basis of their canopy SLN levels. It is possible that these discrepancies between measured and theoretical values may be caused by non-uniform distribution of SLN in the canopy, incident radiation level, and/or the influence of diffuse radiation. In this study, we developed a theoretical framework to predict the consequences of these factors on RUE in peanut and used it to explain the causes of discrepancies between theory and practice. The framework is structured to determine photosynthesis of a layered crop canopy by distributing incident radiation among sunlit and shaded leaves in each layer. It allows for variation in incident direct and diffuse radiation associated with location (latitude), time of year, time of day, and atmospheric condition, which is expressed as the degree of transmission of extra-terrestrial radiation. It also allows for variation in photosynthetic capacity associated with average SLN of the canopy and its distribution in the canopy. Daily canopy photosynthesis, intercepted radiation, and RUE are obtained by numerical integration of instantaneous values calculated at specific times of the day. The framework predicted experimentally determined RUE values accurately and quantified the contribution of each major factor to variation in RUE. On clear days, with high canopy SLN, RUE was predicted to be 1.l g MJ-1. The major cause of previous underestimation of RUE was found to be variation in RUE associated with the level of incident radiation flux density as affected by the degree of atmospheric transmission. RUE increased by up to 0.4 g MJ-1 as atmospheric transmission decreased from 0.75 (clear sky) to 0.35 (heavy cloud). However, varying incident radiation by changing time of year or latitude did not affect RUE. Partitioning incident radiation into direct and diffuse components and consideration of canopy gradients in SLN both had significant effects on RUE, but of a lesser magnitude than effects of degree of atmospheric transmission. The former caused increases in RUE of up to 0.15 g MJ-l, while the latter caused increases of up to 0.13 g MJ-1 at low canopy SLN. Hence, by quantifying the understanding of plant physiological processes and integrating appropriately to the canopy scale, this theoretical framework has explained the causes of discrepancies between measured RUE and previous theoretical estimates.
Improved growth and yield of Faba beans (Vicia faba cv. Fiord) by inoculation with strains of Rhizobium leguminosarum biovar. viciae in acid soils in south west Victoria
Authors: Carter JM , Gardner WK , Gibson AH
Published: November 2004

The response of faba beans (Vicia faba L. cv. Fiord) to seed inoculation with eight strains of Rhizobium leguminosarum biovar. viciae was examined in field experiments at six sites on acid soils in south-west Victoria. At two of the sites, two additional strains were examined, and in 1988, 14 strains were examined at one site. Very low natural populations of R. leguminosarum bv. viciae were found at the experimental sites. Most strains resulted in improved early nodulation and increased grain yield at all sites, when compared to inoculation with the commercial strain of rhizobia (SU391). Plant dry matter production and nitrogen accumulation in the plant shoot tissue was also increased at one site during the flowering period by some strains. Large visual differences between plots inoculated with SU391 and other strains were evident at most sites. Most uninoculated treatments were not nodulated and yielded very poorly. Treatments inoculated with the strain SU391 performed similarly to the uninoculated treatments.
Temperature effects on germination of Trifolium balansae and T. resupinatum with special reference to high-temperature dormancy
Authors: Jansen PI , Ison RL
Published: November 2004

The effect of temperature on germination of the annual pasture legumes Trifolium balansae and T. resupinaturn was investigated. Seed of T. resupinatum lines SA 12240, SA 14433 (from South Australia), C1Z1Res-B, CPI (Commonwealth Plant Introduction number) 026202-3, CPI 026205-2, CPI 027376-2, SA 14433 (from Western Australia), SA 18904, SA 18922, SA 19851 and CPI 045887-2 and cvv. Kyambro and Maral and T. balansae cv. Paradana and lines CPI 045856-1, CPI 045856-4 and AZ 2326 was germinated at 10, 15, 20, 25, 30 and 35�C. T. subterraneum cv. Junee was included for comparison. It was found that germination in all lines except Maral was reduced at 35�C, whereas at 30�C germination was reduced significantly in all lines except Maral, ClZlRes-B, CPI 026202-3, CPI 026205-2, CPI 027376-2, SA 19851 and CPI 045887-2. Germination at 35OC in T. resupinaturn was related to thousand seed weight with the equation: Germination = -31.19+92-39 thousand seed weight (r2 = 0.76). In order to determine the mechanism responsible for the failure of seed to germinate at temperatures above 25�C, seed of T. resupinatum lines SA 12240 and SA 14433 and Maral and T. balansae cv. Paradana was allowed to germinate at temperatures of 25, 30, 35, 40, 45 and 50�C for 8 h, 1, 2, 5 and 10 days after which they were placed at 15� C for 10 days. It was found that temperatures in the 30-40�C temperature range inhibited germination in all lines except Maral, but the same seed germinated readily when placed at 15�C. This seed was considered to possess an enforced high-temperature dormancy. Seed of all lines exposed to 45 and 50�C for longer than 8 h died, but at 8 h final germination was unaffected. It was concluded that high-temperature dormancy could play a role in preventing seed from germinating in the case of a false break. It was proposed that lines should be screened for high-temperature dormancy.
Studies on Western Australian Merino sheep. II. Genetic and phenotypic parameter estimates for objectively measured traits on ram and ewe hoggets using different model types
Authors: Lewer RP , Woolaston RR , Howe RR
Published: November 2004

Data from a Western Australian experimental flock of Merino sheep were used to estimate genetic and phenotypic parameters for clean fleece weight (CFW), greasy fleece weight (GFW), average fibre diameter (FD), and clean yield (Y) from hogget fleeces as well as liveweights at birth (BWT), weaning (3WT), 8-9 months (8WT), 11-12 months (11WT) and 14-15 months (14WT) of age. The estimates were derived for male and female hoggets using restricted maximum likelihood REML. Simple models were fitted in which most environmental effects were omitted for comparison with results from models containing all recorded significant environmental effects. There were no significant differences amongst heritability estimates between models or sexes. Genetic correlations were calculated between sexes for each trait, with none being significantly different to unity. Ranges of heritability estimates across models and sexes were: GFW, 0.30-0-42; CFW, 0.26-0.44; Y, 0.46-0.59; FD, 0.47-0.59; BWT, 0.16-0.33; 3WT, 0.32-0.39; 8WT, 0.22-0.36; llWT, 0-27-0.44; 14WT, 0.27-0.50. Estimates of genetic and phenotypic correlations were in reasonable agreement with other literature values. As with the heritability estimates, the model fitted did not result in important differences in either genetic or phenotypic correlations.
Dilophospora alopecuri and decline in annual ryegrass toxicity in Western Australia
Authors: Riley IT
Published: November 2004

Biological factors contributing to the decline in the incidence of annual ryegrass toxicity (ARGT) in Western Australia were investigated. Annual ryegrass and soil samples were collected in the area where ARGT outbreaks first occurred in Western Australia, an area where the incidence of ARGT has markedly declined. The nematode vector, Anguina funesta, was found in 68% of samples, whereas the toxigenic bacterium, Clavibacter toxicus, was detected in fewer than 2% of samples. The population densities of the nematode were low, but other attributes assayed were normal. The fungus, Dilophospora alopecuri, also associated with A. funesta, was found at 58% of the sampling sites. The abundance of D. alopecuri suggests that it is an important contributor to decline in ARGT. Therefore, the distribution of D. alopecuri in Western Australia was determined in the following season. D. alopecuri was common in the southerly range of A. funesta, but absent in the northerly range where ARGT outbreaks are still common. In the south, D. alopecuri appears to have displaced C. toxicus and reduced A. funesta populations. The findings suggest that there is potential to use D. alopecuri to control ARGT
Plant population dynamics in subterranean clover and murex medic swards. I. Size and composition of the seed bank
Authors: Blumenthal MJ , Ison RL
Published: November 2004

It is possible that the use of harder-seeded varieties of sub. clover (Trifolium subterraneum) and the recently domesticated murex medic (Medicago murex) may improve annual legume persistence in pasture leys. To determine the mechanisms of production and persistence in these two species, the size and composition of the seed bank were compared in four varieties of sub. clover and two lines of murex medic over a three-year period at Forbes in central-west N.S.W. The rate of breakdown of hardseed and the loss of high temperature dormancy was also studied in the same genotypes under conditions of alternating temperature in controlled environment cabinets. In terms of the size of the total seed bank, the sub. clover cultivar with the highest level of hardseed (Dalkeith) was the most successful genotype studied. This was the result of slower rates of hardseed breakdown compared to the other sub. clover cultivars, and better seed production compared to the two murex medic lines. Losses of seed from the seed bank were substantial, and were not all accounted for by germinated seedlings or grazing over summer. The sub. clover cultivars Junee and Seaton Park had the highest levels of high temperature embryo dormancy and the lowest proportion of seedlings germinating over summer. The level of sub. clover hardseed breakdown in the field corresponded well with the 60/15�C laboratory estimates of hardseed breakdown, even though soil surface temperatures over summer at Forbes were rarely in the range of 60/15�C.
The persistence of five cultivars of phalaris after cutting during reproductive development in spring
Authors: Culvenor RA
Published: November 2004

Cultivars of phalaris (Phalaris aquatica L.) were cut at various stages of development between the vegetative state and anthesis, or fortnightly during spring, to determine the effects on subsequent regeneration and persistence. The treatments were applied for 2 years to plants growing on a 200 mm grid at two field sites in the A.C.T. Most of the effects were established in the first year, in which late spring and summer were dry and hot. At a site which was irrigated during the first spring, there was little effect of a single cut at each stage of development. However, autumn regeneration of plants cut again after 14 days or cut frequently was affected. At a less fertile site which was not irrigated, and where dormancy was interrupted during summer in the first year, reductions in autumn regeneration growth of greater than 50% were observed in plants cut once at the early stem elongation and early boot stages. Most plants observed to be dead in autumn at the second site had been cut at the early boot stage. When cut at earlier stages of development, most plants which subsequently died had been cut twice. Unlike a previous study under artificial conditions, differences in autumn regeneration between a reputedly persistent cultivar (cv. Australian) and newer cultivars were not large, probably due to only small differences in synchrony of reproductive stem development occurring under the competitive spring growth conditions of this study. However, higher rates of tillering and tiller survival by cv. Australian observed after cutting prior to stem elongation should reduce its susceptibility to damage during spring. Avoidance of repeated heavy grazing of phalaris during spring, or sudden heavy grazing of tall stands in the stem elongation phase, is recommended to enhance persistence should seasonal factors become unfavourable for tiller survival.
Infection of alternative hosts associated with narrow-leafed lupin (Lupinus angustifolius) and subterranean clover (Trifolium subterraneum) by cucumber mosaic virus and its persistence between growing seasons
Authors: McKirdy SJ , Jones RAC
Published: November 2004

Under conditions of natural cucumber mosaic virus (CMV) spread, eight alternate host species found associated with Lupinus angustifolius (narrow-leafed lupin) and/or Trifolium subterraneum (subterranean clover) were infected commonly and another nine sporadically. Five of these were new records. Because seed of herbaceous plant hosts provides a possible route for virus persistence through dry summer conditions, CMV seed transmission was tested for in alternative hosts. Seed of seven species systemically infected following sap inoculation was tested, but CMV seed transmission was only detected in M. polymorpha (0.7%) and M. indica (0.1%). When seed of 14 potential alternative host species that became systemically infected through natural virus spread was tested, CMV seed transmission was found only in C. decumbens (0.5%). No CMV was detected in Citrullus lanatus growing as a deep-rooted, herbaceous summer weed following CMV-infected L. angustifolius crops, or in the perennial Acacia saligna growing adjacent to a previously CMV-infected L. angustifolius field. CMV persisted through seed transmission over summer for up to 5 years in grazed, self-regenerated T. subterraneum swards. It is concluded that under the conditions of broadacre agriculture, in the Mediterranean-type climate of Western Australia, weed hosts are unlikely to be an important means by which CMV persists over summer, but seed transmission in naturalized M. polymorpha and C. decumbens may occassionally play a minor role. Moreover, despite being seed-borne in T. subterraneum, CMV did not persist readily enough from year to year in grazed swards for T. subterraneum pastures to play more than a minor role as a CMV source for infection of L. angustifolius .
Seasonal development of roots under perennial and annual grass pastures
Authors: Ridley AM , Simpson RJ
Published: November 2004

Studies in the field and in a rhizotron were conducted to examine the root growth of Phalaris aquatica L. (phalaris), Dactylis glomerata L. (cocksfoot) and Lolium rigidum Gaudin (annual ryegrass). Root and tiller development of the perennial grasses in autumn was also studied. In the field, annual ryegrass developed a more extensive surface rooting system than phalaris and cocksfoot by spring in a favourable season. Early root development of annual ryegrass was poor where the first rains of the season did not occur until winter. Growth rates of annual ryegrass roots at depth were similar to phalaris in mid spring in the rhizotron. Phalaris had a higher proportion of live roots than cocksfoot prior to the first autumn rain. Cocksfoot did not regenerate a substantial new root system until it developed secondary tillers, about a month after initial rains. Collectively, these studies indicated that the seasonal development and extent of the root systems of cocksfoot and phalaris were different.
Follicular determinants of the length and diameter of wool fibres. 2. Comparison of sheep differing in thyroid hormone status
Authors: Hynd PI
Published: November 2004

The thyroid hormone status of Corriedale sheep was manipulated in order to produce a change in the rate of fibre elongation (L) with no concomitant change in the diameter (D) of the fibres, to allow the follicular factors responsible for fibre L to be determined. Thyroidectomy resulted in a 60% decrease in wool growth per unit area of skin and a 40% decrease in the rate of fibre volume output, due largely to a decline in fibre L from 412 ,8m/day to 277 8m/day ( P < 0.0001) while fibre D was unchanged (23.9 8m v. 21.9 pm, P > 0-05). Elevation of plasma thyroxine levels to 250% of Control values had no significant effect on fibre L and D, but patch wool growth was increased ( P < 0.05). A high proportion (22.9%) of the follicles in the hypothyroid sheep was inactive in comparison to the low levels of inactivity in the control (1.2%) and hyperthyroid animals (0.1%). The rate of division of follicle bulb cells was depressed by hypothyroidism and increased by hyperthyroidism (P < 0.0001), but there was no effect of thyroid status on the size of the cortical cells released from the wool fibres. Hypothyroid sheep had slightly smaller follicle bulbs and dermal papillae than the control and hyperthyroid animals. The proportion of dividing cells entering the fibre cortex (estimated from cortical cell volume, rate of fibre volume growth and rate of cell division) was depressed by thyroidectomy suggesting that relatively more dividing cells entered the inner root sheath in the follicles of hypothyroid sheep. This is supported by the lower production ratio (ratio of area of fibre to area of fibre-plus-inner root sheath) of the hypothyroid sheep. It is concluded that the rate of fibre elongation is depressed in hypothyroid sheep as a result of both a reduction in the rate of division of cells in the follicle bulb and fewer of these dividing cells entering the fibre cortex. This mechanism allows rapid changes in the rate of fibre elongation to occur with little change in the size of the follicle bulb, and may account for a number of scenarios in which fibre length changes rapidly with no concomitant change in fibre diameter. Fibre diameter, on the other hand, appears to be closely related to the dimensions of the follicle bulb, and by association, to the rate of bulb cell production. Selection of sheep with small follicle bulbs and at the same time, high production ratios, may be means of increasing fibre length whilst maintaining low fibre diameter.
The effects of protozoa and of supplementation with nitrogen and sulfur on digestion and microbial metabolism in the rumen of sheep
Authors: Hegarty RS , Nolan JV , Leng RA
Published: November 2004

Two experiments were undertaken to study the effects of protozoa on sulfur and nitrogen availability and on fermentation and the composition of bacteria in the rumen of sheep. In Experiment 1, 12 faunated and 12 fauna-free sheep were offered a basal diet of chopped wheaten straw with or without sulfur (S) and urea-nitrogen (N) supplements. Sulfur supplementation increased the rate of straw digestion and the concentration of volatile fatty acids (VFA) in the rumen while reducing methane production. The presence of protozoa did not significantly affected this response, although it increased rumen H2S concentration. In contrast, the response of rumen fermentation to a urea supplement was affected by the presence of protozoa. Unsupplemented faunated sheep had a faster rate of in-sacco straw digestion in the rumen than did fauna free sheep (44 v. 36%DM/day). Supplementary urea increased the rate of in-sacco digestion of the basal ration in fauna free sheep (36 to 42%DM/day) but not in the faunated sheep (44 to 46%DM/day), suggesting that N availability was greater in the rumen of faunated sheep. Ammonia and total VFA concentrations in the rumen were not affected by protozoa, but the molar proportions of butyrate and isoacids in rumen VFA were greater in faunated sheep. Bacteria from the rumen fluid of faunated sheep contained a higher proportion of lipid and a lower proportion of N in their cell DM. In a second experiment, the chemical composition of rumen bacteria of faunated and fauna free sheep was further investigated. In both groups, bacteria associated with the particle-phase of digesta contained a higher proportion of lipid and a lower proportion of N than did fluid-phase bacteria. Fluid-phase bacteria from faunated sheep tended to have more lipid and less N in their DM than did those from fauna-free sheep. It was concluded that the presence of protozoa enables sustained fermentation of diets low in rumen available nitrogen and also increases the lipid content of rumen fluid-phase bacteria.
Growth and yield response of barley and chickpea to water stress under three environments in southeast Queensland. I. Light interception, crop growth and grain yield
Authors: Thomas  , Fukai S
Published: November 2004

Two barley cultivars (early-maturing Corvette and late-maturing Triumph) and one cultivar of chickpea (Amethyst at Redland Bay and Borwen at Hermitage), were grown in well-watered and water stress trials in three experiments to determine how the effect of water stress on growth and yield of these crops was modified by other environmental conditions, particularly temperature. Two experiments (experiments 1 and 2) were conducted at one location (Redland Bay) with two times of sowing (April and July), while experiment 3 (June sowing) was conducted at Hermitage Research Station, which had much lower temperatures in winter. In water stress trials, rainout shelters were used to exclude rain from plots from crop establishment to approximately maturity. In both well-watered and water stress conditions, the barley crop produced a lower yield when sown in April than in mid-winter, as grain filling occurred in late winter/early spring, when radiation and temperature were low. Chickpea in the irrigated control, however, produced the lowest yield in the July sowing at Redland Bay, because of the rapid increase in temperature in spring which hastened maturity. In water stress trials chickpea produced the lowest yield at Hermitage, as water stress severely reduced crop growth after flowering. Early-maturing Corvette produced a higher grain yield than late-maturing Triumph in one water stress trial (experiment 1), when difference in maturity time was 40 days, but not in others when the difference in maturity was less than 15 days. In most crops, development of water stress was slow during early stages of growth, and severe stress developed after maximum light interception was achieved. In these cases, water stress had a small effect on light interception but a large effect on light use efficiency (total dry matter produced per unit of solar radiation intercepted). However, for the chickpea sown in April, water stress developed during leaf area expansion, and severely reduced light interception with little adverse effect on light use efficiency. The results thus suggest that whether water stress affects light interception or light use efficiency depends on the timing of water stress in relation to the canopy development.
Forecasting wheat yield in a Mediterranean-type environment from the NOAA satellite
Authors: Smith RCG , Adams J , Stephens DJ , Hick PT
Published: November 2004

This paper reports the relationship between the spatial variation in mean wheat yield/ha of 50 Local Government Areas in Western Australia and satellite measures of the Normalized Difference Vegetation Index (NDVI). Yield/ha was based on estimates of the area harvested and actual grain received by the Cooperative Bulk Handling Ltd. The study area covered 16.3 million ha, in which 2.9 million ha of wheat were sown and 4.66 million tonnes of grain harvested. This was 78% of the total Western Australian wheat crop. Spatial variations in NDVI in early July, at around stem elongation, accounted for 46% of the spatial variation in final yield. This increased to 56% of yield variance around the onset of anthesis at the end of August. It remained high until early November (48%) when crops were senescing or senescent. A combination of NDVI from late August and early November accounted for 70% of the yield variance. In comparison, total rainfall during the 1992 growing season from April to October, the main determinant of yield variations, accounted for 28% of the yield variation. The significant correlation of NDVI with final yield by the middle of the growing season 3 to 5 months before harvest indicates the feasibility of making useful yield forecasts from this time onwards. In addition, the NDVI could provide useful spatial information on the significance of the yield/canopy development/water use relationship which underlies this correlation.
Pathogenic specialization of Puccinia hordei Otth. in Australia, 1966-1990
Authors: Cotterill PJ , Park RF , Rees RG
Published: November 2004

One hundred and fifty-four isolates of the leaf rust pathogen (Puccinia hordei), collected from infected barley plants in Australia between 1966 and 1990, were typed to determine virulence with respect to the resistance genes Rphl to Rph9, Rphl2 (Triumph) and several uncharacterized resistance sources. The Australian cultivar, Prior, reacted differentially to the isolates examined, and is believed to possess a gene which is also present in addition to Rph2 in Reka 1. Virulence and avirulence on Prior were designated P+ and P- respectively. Eleven distinct pathotypes (pt) were identified, with pt 243 P+ and 243 P- predominating in samples collected between 1966 and 1979. In the 1980s, pt 210 P+ was most commonly isolated from samples collected in Queensland and northern New South Wales, and although a range of different pathotypes was present in southern Australia, pt 200 P+ was most frequent in this region. Virulences to genes Rphl, Rph2, Rph4, Rph5, Rph6, Rph8, Rph9 and Rphl2 have been detected, and only Rph3 and Rph7 are likely to be of value in protecting future Australian barleys from the disease.
Reduction of mitotic rate in the wool follicle by cortisol
Authors: Scobie DR , Hynd PI
Published: November 2004

Cortisol reduces wool growth at the systemic and local level, but the minimum time for a response to take place has never been reported because the methods used to measure the changes require at least 4 days of wool growth. A technique using local intradermal colchicines to estimate mitotic rate in wool follicles has been used in the present study, and can measure changes in mitotic rate over periods as short as 2 h. Within the dose range 0 to 1000 8g, intradermal injections of cortisol into adrenalectomized sheep had no effect on mitotic rate in wool follicles within 6 h. Stimulation of endogenous release of cortisol using exogenous adrenocorticotrophic hormone in entire sheep, was similarly ineffective within 5 h. Further investigations using adrenalectomized sheep revealed that bolus injections of hydrocortisone also had no effect on mitotic rate within 5 h. A fourth experiment was conducted, in which 15 adrenalectomized sheep were infused with: a control infusate for 4 days, followed by this infusate containing cortisol at a rate equivalent to 0, 0.87 or 1-82 mg kg-1 day-1 for 4 days, followed by a further 4 days of control infusate. Five hours after the change from control to the cortisol infusate, there was no significant difference in mitotic rate between treatment groups when adjusted using mean mitotic rate in the pre-cortisol period as a covariate (P = 0.887). However, 29 h of infusion with cortisol was sufficient to bring about a significant reduction in mitotic rate (P = 0.034). During the following 3 days of cortisol infusion, mitotic rate was maintained at a significantly lower level in the treated groups (P = 0.018), with the greatest effect apparent in the group which received the highest dose of cortisol. At 53 h post-cortisol infusion, there was a significant recovery in both cortisol treated groups to mitotic rates significantly above those recorded in the pre-cortisol infusion period (P = 0.003), while mitotic rate remained unchanged in the group which received no cortisol. It is concluded that acute changes in plasma cortisol concentration are not likely to produce acute changes in wool growth, but a sustained elevation of plasma cortisol concentration will reduce the rate of wool growth by reducing mitotic rate in wool follicles.
Field evaluation of the entomogenous fungus Metarhizium anisopliae (DAT F-001) as a biocontrol agent for the redheaded pasture cockchafer, Adoryphorus couloni (Coleoptera: Scarabaeidae)
Authors: Rath AC , Koen TB , Anderson GC , Worledge D
Published: November 2004

The field efficacy of Metarhizium anisopliae DAT F-001 for L3 larvae of Adoryphorus couloni was examined on two sheep grazing properties in central Tasmania ('Glenmorey' and 'Warringa'). Experiments included application timing and dose rate studies. All experiments significantly (P < 0.05) reduced survival of L3 larvae. At 'Warringa' DAT F-001 reduced the survival of L3 larvae by 81.5% in late spring following incorporation of 6.3x104 sp/g soil into pasture soils the previous autumn. The experiments showed that autumn application was unlikely to sufficiently reduce the L3 larval population quickly enough to avoid pasture damage in the first year. However, the following year, the overlapping larval populations in the treated plots at 'Warringa7 were reduced by 80% and the subsequent generation of L3 larvae at 'Glenmorey' 2 years after application was reduced by 47%. Additionally, the level of DAT F-001 in the soil remained at or near the original application levels over the experimental periods (12-30 months). We conclude that there are limited opportunities to use DAT F-001 to control an initial pest population, but the fungus has the potential to provide longer-term suppression of subsequent pest generations.
A survey of the effects of high temperature during grain filling on yield and quality of 75 wheat cultivars
Authors: Stone PJ , Nicolas ME
Published: November 2004

The responses of 75 cultivars of wheat to a short (3 day) period of very high temperature (40�C max.) applied at either 10 or 30 days after anthesis were examined under controlled conditions. The effect of high temperature on a number of yield (grain number, individual kernel mass and N per kernel) and quality components (protein composition, apparent amylose content and noodle swelling power) is described for the sample population and for a number of varieties which were either particularly heat tolerant or sensitive. Genotypic variation of response to high temperature of the order of 20% was recorded for the majority of yield and quality components. The fact that responses of this magnitude were caused by exposure to high temperatures lasting only 5 to 6% of the grain filling period demonstrates the extent to which short periods of very high temperature may affect wheat yield and quality.
Estimates of nitrogen fixations by legumes in alternate cropping systems at Warra, Queensland, using enriched - 15N dilution and natural 15N abundance techniques
Authors: Hossain SA , Waring SA , Strong WM , Dalal RC , Weston EJ
Published: November 2004

Nitrogen fixation was measured using two isotopic techniques over 2 years as part of a long-term field experiment established to test alternative management strategies for restoring fertility in a vertisol at Warra, Southern Queensland. Treatments containing legumes were: grass- legume ley (purple pigeon grass and Rhodes grass, lucerne and annual medics) for 4 years followed by 4 years of wheat; a 2-year rotation of lucerne and wheat; a 2-year rotation of medic and wheat; and a 2-year rotation of chickpea and wheat. For the enriched-15N procedure, the proportion of N derived from air (% Ndfa) for the grass-legume and lucerne and medic leys ranged from 67 to 97%, and averaged 85%, with little evidence for effects of season, pasture establishment, time or species. The % Ndfa for chickpea was significantly lower (62%). Values for the natural abundance 15N procedure were mostly lower and more variable than for the enriched method, ranging from 62 to 91% for the grass-legume, lucerne and medic leys, and averaged 76%. It was concluded that the enriched procedure provided more reliable estimates of N2 fixed by the legumes. N2 fixation measured by the enriched-15N dilution method in the grass-legume ley averaged 80 kg N ha-1 during 2 years. A similar amount of N was fixed by the lucerne ley during 1 year (83 kg N ha-1 but medic ley fixed less (56 kg N ha-1 The amount of N2 fixed by chickpea was 72 kg N ha-lyear-1. The dry matter yield of the legumes in leys, mainly lucerne, was closely associated with the amount of N2 fixed, with a value of 28 kg of N2 fixed for each tonne of dry matter produced.
Amelioration of soil compaction by a cover-crop for no-tillage lettuce production
Authors: Stirzaker RJ , White I
Published: November 2004

Excessive cultivation in many horticultural areas results in soil structural decline and poor utilization of water and nutrients. There are no reliable techniques for growing irrigated vegetables without cultivation. This work explores the hypothesis that a winter legume cover-crop can overcome the soil limitations of no-tillage and provide an alternative to excessive cultivation in the vegetable industry. We grew lettuce (Lactuca sativa) under no-tillage in field trials on a sandy loam soil following a bare winter fallow or a cover-crop of subterranean clover (Trifolium subterraneum), and compared this with cultivation by rotary hoe. The clover died naturally in early summer or was desiccated in the spring to form a mulch of at least 5 t ha-1 on the soil surface. The experiment was carried out over a 2.5 year period. The first crop was grown during hot weather and the soil in the no-tillage treatments was only moderately compacted. The yield of lettuce was similar in the no-tillage and cultivated treatments, and increased by about 30% when a mulch was added to each treatment. The soil was artificially compacted after the first crop. The second crop was grown 18 months later, during cooler spring weather, and following two further cover-crops. The yield of no-tillage lettuce was only 40% of that obtained with cultivation. Yield in the no-tillage treatment was doubled in two different ways: (1) by the addition of a surface mulch, and (2) through changes to soil structure stimulated by a cover-crop in the absence of a mulch. The experiments showed that a well-managed cover-crop can significantly ameliorate a compacted sandy soil by modifying soil temperature, soil strength, and by stimulating the formation of biopores.
Occurrence of alfalfa mosaic and subterranean clover red leaf viruses in legume pastures in Western Australia
Authors: McKirdy SJ , Jones RAC
Published: November 2004

When leaf samples were collected from 94 Trifolium subterraneum (subterranean clover) pastures from six districts in spring 1993 in the south-west of Western Australia and tested by enzyme-linked immunosorbent assay, no alfalfa mosaic virus (AMV) or subterranean clover red leaf virus (SCRLV) was detected. In contrast, when 21 irrigated T. repens (white clover) pastures from one district (Bunbury) were sampled and tested in January (summer) 1994, AMV was detected in 16, with eight having infection levels >86%, while SCRLV was found in seven at infection levels of <12%. When a further five T. repens pastures were tested for AMV in October (spring) 1994, the virus was found in all with incidences up to 100%. None of the T. repens pastures with high levels of AMV infection had been resown with T. repens within the last 20 years, whereas those resown within the last five years had little or no infection. AMV was detected in 9/91 annual medic (Medicago spp.) pastures from seven wheatbelt districts sampled in spring 1991 or 1993; a single pasture of M. polymorpha (burr medic) cv. Serena was 21% infected, but the other eight infected ones had <3%. AMV seed transmission was detected in 1/19 commercial seed stocks of M. polymorpha harvested in 1991-93. AMV infection was followed over a 12-year period in M. murex (murex medic) cv. Zodiac seed stocks. It persisted readily through successive seed harvests during this period. It is concluded that infection with AMV and SCRLV is currently not a threat to T. subterraneum pastures in the south-west of Western Australia and that AMV seems not to be one in wheatbelt annual medic pastures provided these are sown with healthy medic seed. In contrast, AMV poses a potential threat to the productivity of irrigated T. repens pastures. SCRLV is also sometimes present in T. repens pastures, but was not found at serious levels.
Presence of a clostero-like virus and a bacilliform virus in pineapple plants in Australia
Authors: Wakman W , Teakle DS , Thomas JE , Dietzgen RG
Published: November 2004

When sap of asymptomatic or mealybug wilt-affected pineapple plants of the Smooth Cayenne group was negatively stained and examined in an electron microscope, clostero-like virus particles were occasionally seen. However, numerous clostero-like virus particles and occasionally some bacilliform particles were seen in partially purified preparations from both asymptomatic and wilted pineapple leaves. An antiserum, made by injecting partially purified preparations of clostero-like particles into a rabbit, trapped and decorated the clostero-like particles. Using this antiserum, the clostero-like particles (c. 1700 -1900x12 nm) were found in almost all plants tested of Smooth Cayenne selections C10, C13, C30 and F-180, the hybrid cv. 53-116 and a selection of the rough leaf Queen group. The particles were more readily trapped from extracts of roots of hybrid cv. 53-116 and Smooth Cayenne selection C10 than from leaves, crowns and fruits. They were not detected in seedlings of a cross between a Queen selection and the Smooth Cayenne selection C10. The clostero-like particles are similar to those reported to occur in pineapple plants in Hawaii and South Africa. This is the first report of their occurrence in Australia. Trapping and decoration tests of particles in pineapples in quarantine from Brazil, France, Malaysia and Taiwan indicated that a similar clostero-like virus occurs in all these countries. The bacilliform particles measured about 133x33 nm. They were trapped and decorated by the Queensland pineapple virus antiserum and also by an antiserum to sugarcane bacilliform badnavirus. They were detected occasionally in various smooth leaf and rough leaf pineapples in north and south Queensland and northern New South Wales. However, in one commercial planting of Smooth Cayenne selection C10 in south Queensland, bacilliform particles were trapped from 29/47 plants. This is the first report of a small bacilliform virus, probably belonging to the badnavirus group, occurring in pineapple plants. The relationship of the clostero-like and bacilliform viruses to yield loss and mealybug wilt in pineapples is unknown.
Proanthocyanidins (condensed tannin) destabilise plant protein foams in a dose dependent manner
Authors: Tanner GJ , Moate PJ , Davis LH , Laby RH , Li YuGuang , Larkin PJ , Li YG
Published: November 2004

The compressive strength and persistence of protein foams produced from extracts of legume leaves were measured. The presence of foliar proanthocyanidin (PA, condensed tannin) in species such as Onobrychis and Lotus correlated with foams of negligible compressive strength and persistence and also with a reputation for bloat safety in the field. PA purified from forage legume leaves significantly decreased the compressive strength of protein foams produced from purified red clover leaf protein. The decrease in the compressive strength was related to the concentration of added PA in a dose-dependent manner. A ratio of PA to protein of 0.1 reduced the compressive strength by approximately half relative to the strength of the PA-free control. Purified PAS with different chemical structures had similar effects on the compressive strength of protein foams. The significance of these observations to pasture bloat and forage legume improvement is discussed.