bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of applied nitrogen on weed invasion of Lolium perenne pastures in a subtropical environment
Authors: McKenzie FR
Published: March 2005

Lolium perenne L. (perennial ryegrass) exhibits poor persistence in subtropical environments and this is often characterised by weed invasion. The effect of applied nitrogen (N) (120-720 kg/ha.year), on weed invasion of perennial ryegrass was examined during the establishment year. Weed tiller densities ranged from 50 tillers/m2 (at 360 kg N/ha.year) during November 1993, to 2400 tillers/m2 (at 120 kg N/ha.year) during February 1994. Increasing levels of applied N up to 360 kg/ha.year reduced both weed tiller densities and relative frequencies in perennial ryegrass pastures. Seasonally, high weed tiller densities (up to 2400 tillers/m2 at 120 kg N/ha.year) and high frequencies (46-82% for 120 and 600 kg N/ha.year, respectively) were observed over midsummer (December) to autumn (May). Applying N at levels above 360 kg/ha.year (or 30 kg/ha.month) is useful in minimising weed invasion of perennial ryegrass during its establishment under subtropical conditions.
Sustaining productivity of a Vertisol at Warra, Queensland, with fertilisers, no-tillage or legumes. 3. Effects of nitrate accumulated in fertilised soil on crop response and profitability
Authors: Strong WM , Dalal RC , Cahill MJ , Weston EJ , Cooper JE , Lehane KJ , King AJ , Chicken CJ
Published: March 2005

Unreliable rainfall during the crop growing season leads to a variable use of applied fertiliser nitrogen (N) by the crop, which may leave substantial fertiliser N residue in the soil. Residual effects of fertiliser N (0-150 kg/ha) applied to a succession of wheat crops over the period 1987-94 were studied in terms of increased crop returns ($A/ha) from fertiliser application and increased soil mineral N for the subsequent crop. In spite of the unreliability of wheat responses to applied N in this region, increases in financial returns over this sequence of crops suggest that a strategy of routine N application to wheat was highly profitable on this fertility-depleted soil. When increases in returns from 1 fertiliser application were summed over successive crops, financial returns generally increased with increasing rate of N applied up to the highest N rate (100 or 150 kg/ha). When N was applied to each successive crop, financial returns were similarly increased but applications >50 kg/ha were less profitable than rates <50 kg/ha. Increased financial returns for the 7 crops grown with conventional tillage increased by $A306/ha, $794/ha, $867/ha and $867/ha for fertiliser N applied at rates of 12.5, 25, 50 and 75 kg N/ha to each crop, respectively. Total N fertiliser costs for the 7 crops were $A63ha, $126ha, $253/ha and $380/ha. Increased financial returns of $608/ha and $962/ha were derived from applications of 25 and 75 kg N/ha to each of the 7 crops with zero tillage. When N uptake by wheat was reduced by water deficit, or where a longer fallow period created much higher nitrate levels, a single fertiliser N application of 75 or 150 kg/ha resulted in nitrate accumulated to 1.2 m depth in the following May. Where N was applied to each crop in the sequence, application of 75 kg/ha increased soil nitrate to 1.2 m in the following May, except in 1989 and 1990. The 3-crop sequence, 1988-90, placed high demands on soil N supplies, with high wheat yields (about 4.5 t/ha) and grain N contents (100-115 kg/ha) in 1988 but lower yields (>2t/ha) in 1989 and 1990. Consequently, low levels (46-63 kg/ha) of soil mineral N were apparently carried over for crops in 1989 and 1990 even where 75 kg N/ha was applied to the preceding crop. Subsequent recovery of financial losses, incurred in years of water deficit, made the routine application of 75 kg N/ha to fertility-depleted soils of this region profitable.
Effectiveness of different methods of applying superphosphate for lupins grown on sandplain soils
Authors: Bolland MDA , Jarvis RJ
Published: March 2005

In 3 experiments in 1991 on very sandy soils near Eradu, Western Australia, the effectiveness of superphosphate for producing lupin (Lupinus angustifolius L.) seed (grain), was measured for fertiliser applied at 0-73 kg P/ha to the soil surface just before sowing (topdressed), or banded with the seed, or 8 cm below the seed while sowing 5 cm deep. At all sites, banding phosphorus (P) below or with the seed was equally effective as applying P to the soil surface. In a fourth experiment, on a very sandy soil near Badgingarra, Western Australia, levels of P (0-547 kg P/ha) as superphosphate, had been applied once only from 3 to 7 years previously (1985-89). The P applied in previous years was found to have leached. In 1992, superphosphate (0, 9, 18 and 36 kg P/ha) was applied across all the original plots. Fertiliser was either applied to the soil surface just before sowing lupins, or banded with the seed at 5 cm depth or at 8 cm below the seed. Grain yields from banding P below the seed exceeded those where P was topdressed when <250 kg P/ha had been applied in previous years, or where the Colwell soil-test P for the 10-20 cm depth was <10-15 mg P/g soil. When >250 kg P/ha had been applied in previous years, sufficient P had leached well below the seed, so there was little response to P and no advantage in placing freshly applied P below the seed when sowing. A possible explanation for the different results at Eradu and Badgingarra is provided.
Comparing Imperial mandarin and Silverhill satsuma mandarin as seed parents in a breeding program aimed at developing new seedless citrus cultivars for Australia
Authors: Sykes SR , Lewis WJ
Published: March 2005

In a breeding program aimed at developing new seedless citrus cultivars, crosses were conducted between Silverhill satsuma and Imperial mandarin as seed parents, and sweet orange and pummelo cultivars as pollen parents. Poncirus trifoliata pollen was also used to provide a morphological marker to compare each seed parent's ability to produce hybrid seedlings. Both Silverhill and Imperial can produce seedless fruits. Methods used to produce and identify hybrids highlighted the relative ease with which either can be used as a seed parent. Imperial mandarin produced more seeds per fruit (mean >8) than Silverhill satsuma (mean <4), thus requiring fewer controlled pollinations to produce desired numbers of hybrids. Germination rates of Imperial-cross seeds were generally greater than for Silverhill-cross seeds. A single seedling emerged from every Imperial-cross seed that germinated, demonstrating the monoembryonic nature of Imperial seeds. All Imperial x P. trifoliata seedlings were hybrids, confirmed by their trifoliate leaves. From this, all seedlings from other Imperial-cross seeds were assumed to be hybrids. By contrast, embryo rescue after in vitro germination demonstrated the polyembryonic nature of the Silverhill-cross seeds. Mean embryo number per Silverhill seed varied from 3.6 to 12.0 between crosses, and from 2 to 30 between seeds within crosses. About 50% of all embryos from Silverhill-cross seeds were rescued and retained for hybrid identification. Silverhill hybrids were identified visually and/or by isozyme banding patterns. Silverhill x pumrnelo hybrids were identified or confirmed using glutamate oxaloacetate transaminase and phosphoglucomutase isozymes. Silverhill x Sweet orange hybrids were identified using isocitrate dehydrogenase, phosphoglucoisomerase or shikimic acid dehydrogenase (SKD) isozymes, although the banding patterns for SKD isozymes were complex and difficult to interpret genetically. Thirty-three Silverhill satsuma hybrids were identified. This represented a hybrid recovery rate of 11.15% compared with >90% for every Imperial-cross combination.
Effect of hot air disinfestation treatment in combination with simulated air freight conditions on quality of 'Kensington' mango (Mangifera indica Linn.
Authors: Jacobi KK , Wong LS , Giles JE
Published: March 2005

The quality of 'Kensington' mangoes (Mangifera indica Linn.) from 2 major Queensland production regions was evaluated following a hot air [HAT, also known as vapour heat (VHT)] disinfestation treatment (46.5�C seed surface temperature held for 10 min under conditions of high humidity) combined with a disease control treatment (55�C water for 5 min) prior to HAT, and storage conditions likely to be encountered during air shipment to Japan (either 10�C for 5 days plus 22�C for 5 days, or 13�C for 5 days plus 22�C for 5 days, or 22�C for 10 days). Final quality was optimum if fruit were treated with HAT alone and stored at 22�C. Fruit injury, in the form of skin browning and lenticel spotting, was particularly severe in HAT plus disease controI fruit stored at 10/22�C. Storage at 10�C combined with heat treatments may be too stressful to fruit physiology, leading to fruit injury and reduced fruit quality at the market destination.
Effect of daylength and temperature on flowering of the cut flower species Banksia coccinea and Banksia hookeriana
Authors: Rieger MA , Sedgley M
Published: March 2005

Vegetative growth and flowering of Banksia coccinea and B. hookeriana were investigated under controlled environment conditions of 8 and 16 h daylength at 15/10 and 25/20�C (day/night). All treatments stimulated vegetative growth of B. coccinea but the 16 h, 25/20�C treatment resulted in greatest shoot growth and highest floral initiation. Only the 8 and 16 h daylength treatments at 25/20�C stimulated vegetative growth, shoot extention and floral initiation of B. hookeriana. Comparable results for floral initiation and vegetative growth were observed with plants under outside conditions. The results indicate that vegetative growth is a prerequisite for floral initiation. Floral initiation of B. coccinea was influenced by daylength whereas B. hookeriana responded to temperature.
Substitution and production responses when lactating dairy cows graze a white clover pasture supplemented with maize silage
Authors: Stockdale CR
Published: March 2005

Friesian cows (16) in late lactation grazed pure white clover (Trifolium repens cv. Haifa) swards for 32 days in autumn and were supplemented with maize (Zea mays) silage. Four groups of 4 cows were offered either 19 or 39 kg dry matter (DM)/cow.day of white clover with either 0 or 4.4 kg DM/cow.day of maize silage. All cows were individually fed maize silage and grazed the pasture as individual groups according to treatment. When maize silage was fed, total intake increased, this occurring to a greater degree at the low pasture allowance. The level of substitution of silage for pasture was 0.14 and 0.40 kg DM reduction in pasture intake per kg DM of maize silage eaten at the low and high allowances, respectively. At the low pasture allowance, milk yields were 10.1 and 13.7 kg/cow. day when 0 and 4.4 kg DM/cow.day of maize silage were fed, respectively, and were 15.5 and 15.9 kg/cow.day at the high pasture allowance. Liveweight and body condition increased as plane of nutrition increased but there were no effects of feeding on milk fat or protein contents. Feeding maize silage had little effect on any rumen or faecal variable although there was generally less ammonia nitrogen in rumen fluid when cows were supplemented with maize silage.
Diet selection by cattle grazing Stylosanthes-grass pastures in the seasonally dry tropics: effect of year, season, stylo species and botanical composition
Authors: Coates DB
Published: March 2005

The dietary preference of cattle grazing Stylosanthes-based pastures in the seasonally dry tropics of North Queensland was studied using faecal carbon ratios (S13C) to determine grass-legume proportions. Estimates were made at monthly intervals for several years in 1 experiment to determine the effect of year, season and botanical composition on dietary stylo proportions. In another experiment, the effect of stylo cultivars (Verano and Seca) on dietary preference was monitored for 17 months. Where pastures provided ample opportunity for selection, cattle showed a strong preference for grass in the early wet season and in the late dry season. The proportion of stylo in the diet increased during the wet season and reached peak proportions (as high as 80%) in the late wet season or early dry season. Dietary stylo proportions decreased as pastures dried off and as the stylo shed leaf or became more stemmy. The length of the wet season and the amount and distribution of rainfall had a major influence on the seasonal pattern of diet selection. Stylo rarely fell below 20% in the diet. On an annual basis, stylo accounted for about 45% of the diet which was appreciably higher than the proportion of stylo in the pasture. Dietary stylo proportions were higher on Seca-based pasture than on Verano-based pasture. The avoidance of stylo in the early wet season was less pronounced with Seca compared with Verano. Later in the season Seca was the dominant dietary component for a much longer period than Verano. The effect of botanical composition on dietary grass-legume proportions varied between and within years. Correlations between grass-legume proportions in the pasture and in the diet were highest in the late dry season and early wet season when preference for grass was strongest. At the end of the wet season when cattle preferred stylo, dietary stylo was not related to pasture stylo content except in a drought year. Averaged over the full year, dietary stylo content was significantly correlated with pasture stylo content in all years and the correlation was highest in a drought year when there was a high level of utilisation and less opportunity for selection. A simple model relating dietary stylo to pasture stylo was developed and is discussed.
Nutritive value of subterranean clover in a temperate environment
Authors: Mulholland JG , Nandra KS , Scott GB , Jones AW , Coombes NE
Published: March 2005

A study was made over 2 years of the nutritive value of the subterranean clover (Trifolium subterraneum L.) cultivars, Trikkala, Larisa and Goulburn, in grazing experiments with Border Leicester x Merino lambs. Liveweight gain was similar for all cultivars in the first year and in the second year was higher on Larisa (153 g/day) compared with Goulburn and Trikkala (131 and 103 g/day, respectively). Wool growth was not significantly different between cultivars. Both the digestibility and water-soluble carbohydrate content of the petiole and stem plant fraction were significantly (P<0.05) higher than those of the leaf fraction, even though the leaf had a lower level of cell wall organic matter. The ratio of lignin to cell wall organic matter was also higher in the leaf fraction. Samples obtained via oesophageal fistula showed that petioles comprised most of the dry matter in the diet and, thus, were the major contributor to energy supply. Differences were found in the degradability characteristics of the 3 cultivars which led to significant (P<0.05) differences in the concentration of rumen degradable dry matter and effective rumen degradable protein (ERDP). During the vegetative and early flowering stages, the concentration of ERDP exceeded the supply of fermentable metabolisable energy required for microbial protein synthesis. In mature clover, the concentration of ERDP was low and limiting microbial protein synthesis. The degradation characteristics of protein were highly correlated with liveweight gain (r2 = 0.90) and wool growth (r2 = 0.70). It is suggested that increasing the petiole : leaf ratio could increase the efficiency of utilisation of subterranean clover diets.
Bioassay and baiting methods for determining occurrence of races of Phytophthora clandestina in soil
Authors: Purwantara A , Flett SP , Keane PJ
Published: March 2005

The method currently used for determining races of Phytophthora clandestina requires isolation of pure cultures of the pathogen and testing of their pathogenicity on a range of differential cultivars. To date, the pathogen has not been isolated directly from soil and isolation of the pathogen from naturally infected seedlings is laborious. A bioassay involving the planting of differential cultivars in soil samples in small planting trays was developed to identify races of P. clandestina in soil. The specific races of the pathogen in the soil were determined by assessing the disease severity and the extent of sporulation of the pathogen on the roots of the differential cultivars. A more rapid baiting method using cotyledons of differential cultivars in flooded soil samples was also developed to determine the presence of different races in the samples. Both bioassays were used to confirm the presence of race 0 and race 1 in separate paddocks at Rutherglen, northern Victoria, over 4 seasons. The presence in field soil of another root rot pathogen of subterranean clover, Aphanomyces euteiches, was also detected using these techniques.
Influence of sowing time on grain quality characters of wheat grown in north-western Victoria
Authors: Flood RG , Martin PJ , Panozzo JF
Published: March 2005

Grain from sowing time experiments at 1 site in 1984 and 2 sites in 1986 and 1987 in northwestern Victoria were tested for several grain and flour characters. The tests included grain protein percentage, sodium dodecyl sulfate (SDS) sedimentation volume, particle size index, milling yield, test weight and Pelshenke wholemeal fermentation time, although not all tests were carried out in all years at both sites. The findings are reported without analysis of the underlying processes involved. The effect of sowing time on grain protein percentage was variable; at Dooen in 1984 there was a slight decrease, at Dooen and Walpeup in 1986 there was an increase but there was no change at Dooen in 1987, as sowing time was delayed. Sowing time had a significant effect on SDS at Dooen in 1984 and Dooen and Walpeup in 1986. There were no marked trends at Dooen in 1984, but significant differences between individual sowing times, and in 1986 there was an inconsistent increase as sowing time was delayed. At Walpeup in 1986 there was a substantial increase in values as sowing time was delayed. Partial correlation coefficients, however, indicated that at Dooen in both years and Walpeup in 1986, variation for SDS was due almost entirely to differences in grain protein percentage, although at Walpeup in 1986 there was a slight additional effect of sowing time. Particle size index was significantly affected by sowing time at both sites in 1986; at Dooen there was a decrease as sowing time was delayed and then an increase for the last sowing time, and at Walpeup there was an increase as sowing time was delayed. Although some effects of sowing time on milling yield and test weight were statistically significant, only one had commercial significance-milling yield at Walpeup in 1986. Pelshenke time was affected by sowing time at Dooen in 1984 and Walpeup in 1986, but there were no obvious trends. Sowing time x cultivar interactions have implications for quality testing of wheat crossbreds. Grain growers can be reassured that sowing crops over an extended period appears to have little or no detrimental effect on grain quality with respect to bread baking properties. In some seasons, however, there may be substantial increases in grain protein percentage in later sown crops, although this would generally be associated with lower yields.
Yield and seasonal growth flushing of Protea 'Pink Ice' and Leucadendron 'Silvan Red' in South Australia
Authors: Barth GE , Maier NA , Cecil JS , Chyvl WL , Bartetzko MN
Published: March 2005

Data on yield and growth flushing of 2 protea varieties were collected at commercial sites in South Australia over 3 years. Mean (� s.e.) yield of Protea 'Pink Ice' in terms of marketable stems averaged 63 (�) stems/plant on a highly fertile soil to 39 (�1) stemslplant on an infertile site. On the same sites, Leucadendron 'Silvan Red' yielded means (�se.) of 314 (�13) and 219 (�5) marketable stems/plant. Data are presented in marketing classes based on stem length. Monthly increases in stem length and diameter were used to determine seasonal growth flushing patterns in the 2 cultivars. Pink Ice commenced annual growth in August-September, reached peak growth rate in October and fell to low levels in December. Silvan Red commenced growth between October and November, reached peak growth rate in December and continued stem elongation until March when all growth ceased until the following year.
Evaluation of tropical pasture species as leys in the semi-arid tropics of northern Australia
Authors: Cameron AG
Published: March 2005

Testing of pasture plants as leys in the semiarid tropics of northern Australia has been limited. Characteristics of successful ley pasture plants are discussed. The most important characteristic is the ability to contribute nitrogen to subsequent crops, which has been demonstrated for a number of legumes but not for grasses. Over 2300 legume and grass introductions have been evaluated as permanent pastures. Of the genera which are adapted to the environment of northern Australia, 14 grass cultivars (including Brachiaria, Cenchrus and Digitaria spp.) and 11 legume cultivars (including Aeschynomene, Centrosema and Stylosanthes spp.) are productive and are currently recommended for use as permanent pasture plants. Field experiments and commercial practice have shown that Centrosema pascuorum (cvv. Bundey, Cavalcade) is well adapted for use as a ley pasture plant. Other legumes which are suitable for use in leys are Alysicarpus vaginalis, Chamaecrista rotundifolia cv. Wynn, Macroptilium gracile cv. Maldonado and Stylosanthes hamata cvv. Amiga and Verano. The grasses are generally not suitable for ley pastures as they are strong perennials which are difficult to control in cropping areas. The exception is Urochloa mosambicensis which may be suitable as a break crop to control broadleaf weeds such as Sida acuta, Senna obtusifolia and Hyptis suaveolens. This species can be controlled with economic rates of herbicide and has seed dormancy characteristics which allow it to regenerate following a cropping phase.
Legume-based pasture options for the live cattle trade from the Australian semi-arid tropics
Authors: Winter WH , McCown RL , Zuill D
Published: March 2005

The extensive beef industry in the Northern Territory has been based almost exclusively upon native grass pastures for over a century. The recent development of an export trade for live cattle of specific age, weight and type, has increased returns over chilled manufacturing beef exports and has resulted in a demand for improved pastures that can support rapid growth of young cattle. This paper compares the potential of native grass pastures, legume ley pastures and permanent sown grass-legume pastures, in a range of configurations, to meet the market demand. Results of farming systems and sown pasture management experiments conducted at the Katherine Research Station are presented. Data from these experiments and other sources are used to explore options appropriate to the new market. Particular attention has been given to the time required for weaner steers to reach export target weights of 290-300 kg/head and the flexibility of systems to seasonal and animal variability. Permanent sown pastures are sustainable at stocking rates of about 2 steers/ha, but results indicate difficulty in maintaining legume dominance in the ley pastures, particularly if the cropping frequency is reduced. A proposal to use forage crops, rather than grain crops, to deplete soil nitrogen and reduce the incidence of weeds, is discussed. We recommend that ley pastures be retained as part of the management system, despite management difficulties, as they provide higher productivity and greater flexibility for farmers to meet the market requirements.
No-tillage planters for heavy-textured Alfisols in the semi-arid tropics of Australia
Authors: Gould NS , Peake DCI , Dalgliesh NP
Published: March 2005

This paper provides key information on 4 no-tillage planters to facilitate adoption by fanners in northern Australia. Four commercial planters (Buffalo All-Flex Convertible slot planter, Buffalo All-Flex Compact slot planter, John Deere Max-Emerge planter and Mason Spring Release (SR) Integral planter) of contrasting design were tested in various configurations under 5 different moisture regimes during drying of a heavy-textured Alfisol at Katherine Research Station, Northern Territory, Australia (14�20'S, 132�20�E, 108 m altitude) at the end of the 1982-83 wet season. Significant differences in emergence were measured between planters and between configurations under most moisture regimes. Seedling emergence was greatest in Buffalo-Compact planter treatments, less for Buffalo-Convertible and Mason SR Integral treatments and lowest for John Deere Max-Emerge treatments. The Buffalo planters, each with an effective trash cutting coulter and narrow tine slot opener, produced consistently better results under all moisture regimes than the other 2 planters. The Mason SR Integral, with its wide tine opener, created a high incidence of clods which restricted emergence and led to increased occurrence of unimbibed seeds. Generally, for the 3 tine opener planters, the looser the soil in the furrow, the poorer the emergence. The John Deere Max-Emerge double-disc opener, whilst performing well under moist conditions, generally performed poorly when soil conditions were dry. This planter was on most occasions unable to maintain effective depth control under excessively wet or dry conditions, resulting in lower in-furrow soil moisture and significantly poorer and slower emergence than occurred with the other planters. In-furrow seed-firming presswheels, applying a contact pressure of approximately 4-5 kg/cm of presswheel tyre width, ensured better seed-soil contact and higher emergence levels than twin-inclined overfurrow presswheels. The over-furrow presswheels fitted to the John Deere Max-Emerge planter were often unable to close the slot effectively, resulting in the creation of voids and caps with resultant high seedling mortality.
Coping with soil and climatic hazards during crop establishment in the semi-arid tropics
Authors: Abrecht DG , Bristow KL
Published: March 2005

Climatic induced hazards (e.g. water deficit, high soil temperature and high soil strength) that adversely affect seedling emergence and establishment of annual crops on red earth soils (Kandsols) at Katherine in the Daly basin of the Northern Territory are reviewed and results of some recent simulation studies and experiments are presented. Simulation studies, using 100 years of historical weather data, have shown that maize and sorghum density at Katherine is rarely reduced by water deficit during crop establishment. However, the median number of days between 1 December and 20 January during which seedlings may be exposed to damagingly high soil temperature (>55�C between 2 and 7 days after sowing) was 5.5, out of an estimated 21 days suitable for sowing. While the exposure of a crop to inclement conditions during establishment may have immediate and dramatic effects on the mortality of pre-emergent and post-emergent seedlings, there may also be longer-term and less evident adverse effects on crop growth and development. The responses of developing seedlings to inclement conditions following sowing are described and management options (eg adjusting planting dates, changing crop species, changing seedbed configurations, using surface mulch) for the amelioration of the seedbed environment are discussed. Of the possible management options for ameliorating adverse seedbed conditions during crop establishment in the semi-arid tropics (SAT), it appears that the best practice is to maintain a soil surface cover (mulch) in close proximity to the emerging seedlings. The presence of surface mulch extends the window of opportunity for establishing crops by slowing soil drying, delaying the onset of high soil temperatures and high soil impedance, and by improving the availability of water to the young seedlings at this critical stage.
Surface runoff, soil and nutrient losses from farming systems in the Australian semi-arid tropics
Authors: Dilshad M , Motha JA , Peel LJ
Published: March 2005

Most soils suitable for dryland agriculture in north-west Australia occur in the Daly Basin. These are sesquioxidic soils which include red, yellow and grey earths, and soils related to yellow and red earths. The potential, for these arable soils to be degraded by highly erosive rainfalls, common to the region, is high. Farming practices strongly influence the soil surface characteristics (vegetation cover, roughness, soil strength), which in turn control surface runoff, and sediment detachment and transport. In studies conducted during 1984-89 in the Daly Basin, conventionally tilled catchments, produced 1.5-2 times more runoff and lost 1.5-6 times more soil than their no-tillage counterparts (all catchments were within soil conservation banks). In these conventionally tilled catchments, soil loss was <8.1 t/ha.year. Other studies in the region have shown that, without soil conservation banks, soil loss can be around 100/ha.year under conventional tillage. Little work, however, has been undertaken on farms in the Australian semi-arid tropics to study the movement of nutrients and herbicides (in ionic and adsorbed forms) and further research is warranted.
Operational aspects of ley farming systems in the semi-arid tropics of northern Australia: a review
Authors: Yeates SJ , Abrecht DG , Price TP , Mollah WS , Hausler P
Published: March 2005

The ley farming systems proposed for the Australian semi-arid tropics involve rotating an annual pasture (usually legume) with crops sown using no-tillage. These systems were developed to overcome many of the climatic constraints that beset previous attempts at cropping in the region. However, difficulties in the timing of farm operations also contributed to past failures. No analysis of the operational aspects of ley farming had been made; this was the objective of this paper. During the transition between wet and dry seasons rainfall is extremely variable. These periods were shown to be the most critical time for operations in ley farming systems. During the dry-wet transition, management of ley pastures is very difficult because pastures must provide grazing for livestock as well as sufficient soil cover for timely sowing of a following crop. Legume pastures have reduced grazing value at this time due to spoilage by early rain. Similarly, during the wet-dry transition annual pastures must be allowed to set seed at a time when crops are yet to be harvested and stubbles are not available for grazing. It was suggested that including separate paddocks of perennial pasture could reduce the demand on annual pastures during the seasonal transitions. A limited number of days to sow a crop combined with severe yield penalties for late sowing restrict the area that can be sown in any season. Sowing opportunities were determined for 3 locations in the Northern Territory. No-tillage was shown to increase the potential number of sowing days. However, the time available to apply glyphosate before sowing using no-tillage was confined to the morning due to risk of afternoon rainshowers reducing efficacy. The number of seasons where a particular crop or cultivar could not be sown was independent of the method of tillage. The wet-dry transition was shown to be important for harvest operations. Our analysis of 3 sites in the Northern Territory suggests that for mungbean and sorghum, later maturity combined with prompt harvest will reduce the risk of poor seed quality due to weathering and could permit earlier sowing. However, for sorghum, an economic assessment of these practices required research that can quantify the interaction between sowing date, time-to-maturity and grain yield.
Commercial experience in developing ley farming systems for the Katherine-Darwin region, Northern Territory
Authors: Price TP , O'Gara F , Smith ESC , Pitkethley R , Hausler P
Published: March 2005

This paper examines the past, present and likely future commercial development and adoption of ley farming systems in the Katherine-Darwin region(about 12-14�S, 131-132�E, elevation 30-1 10 m) of the Northern Territory. Producers' current practices, adaptations and the extent to which they have adopted a systems approach are reported. Advantages of ley farming and the constraints to its more rapid adoption are described. Also discussed are aspects of crop, cattle and hay production; weed, insect and plant disease control, and management; on-farm demonstrations and the economics of crop production, from the producer's perspective, in the context of ley farming.
Being realistic about no-tillage, legume ley farming for the Australian semi-arid tropics
Authors: McCown RL
Published: March 2005

There is a long tradition of expectation that, in time, land use in the better-endowed areas of Australia's semi-arid tropics would intensify from beef production on grassy woodlands to broadacre production of dryland crops. However, successive development attempts have yet to result in a substantial field crop industry. This paper reflects on a recent 20-year research and development episode in which ley farming, so successful in the wheat-sheep zone of southern Australia, was adapted and trialed in the tropical north. The system tested in the tropics was one which featured (i) coarse grain crops in rotation with legume leys and (ii) cattle grazing native pasture in the crop growing season and ley and crop residues in the dry season. It can be concluded that this system is technically successful. But compared with the ley system in southern Australia, the benefits of pasture legumes are less efficiently captured, both in the animal and the crop production enterprises. In addition, in this climate and on these soils, pastures with the high legume composition needed to substantially substitute for nitrogen fertiliser in the crop phase pose a serious threat of soil acidification. In contrast to legume leys, the advantage of no-tillage, mulch farming practices over conventional cultivation is much greater in this semi-arid tropical region than in temperate or Mediterranean areas: by slowing evaporation, mulch is often crucial in reducing high temperature injury or impedance to emerging seedlings as well as reducing the deleterious effects of intensive summer rainfall. But even with this improvement the climatic risks in dryland grain cropping remain a strong deterrent to crop industry development. Today, the findings from past experimentation, accrued farming experience, and new information products combine to provide what seem to be more realistic expectations for agriculture in this region. Even with the 'best' technology, this region suffers comparative disadvantage with respect to dryland field crop production and marketing. However, the region enjoys comparative advantages in the production of several other types of commodities, and a more realistic approach to 'Research and Development' includes a shift of resources toward activities with production and marketing advantages.
Kaposi's sarcoma-associated herpesvirus expresses an array of viral microRNAs in latently infected cells
Authors: Cai Xuezhong , Lu Shihua , Zhang Zhihong , Gonzalez Carlos M. , Damania Blossom , Cullen Bryan R.
Published: March 2005

MicroRNAs (miRNAs) are an endogenously encoded class of small RNAs that have been proposed to function as key posttranscriptional regulators of gene expression in a range of eukaryotic species, including humans. The small size of miRNA precursors makes them potentially ideal for use by viruses as inhibitors of host cell defense pathways. Here, we demonstrate that the pathogenic human herpesvirus Kaposi's sarcoma-associated herpesvirus (KSHV) encodes an array of 11 distinct miRNAs, all of which are expressed at readily detectable levels in latently KSHV infected cells. Individual KSHV miRNAs were expressed at up to 2,200 copies per cell. The KSHV miRNAs are expressed from what appears to be a single genetic locus that largely coincides with an ≈4-kb noncoding sequence located between the KSHV
v-cyclin
and
K12
/
Kaposin
genes, both of which are also expressed in latently infected cells. Computer analysis of potential mRNA targets for these viral miRNAs identified a number of interesting candidate genes, including several mRNAs previously shown to be down-regulated in KSHV-infected cells. We hypothesize that these viral miRNAs play a critical role in the establishment and/or maintenance of KSHV latent infection
in vivo
and, hence, in KSHV-induced oncogenesis.
Simulations of the pressure and temperature unfolding of an α-helical peptide
Authors: Paschek Dietmar , Gnanakaran S. , Garcia Angel E.
Published: March 2005

We study by molecular simulations the reversible folding/unfolding equilibrium as a function of density and temperature of a solvated α-helical peptide. We use an extension of the replica exchange molecular dynamics method that allows for density and temperature Monte Carlo exchange moves. We studied 360 thermodynamic states, covering a density range from 0.96 to 1.14 g·cm
–3
and a temperature range from 300 to 547.6 K. We simulated 10 ns per replica for a total simulation time of 3.6 μs. We characterize the structural, thermodynamic, and hydration changes as a function of temperature and pressure. We also calculate the compressibility and expansivity of unfolding. We find that pressure does not affect the helix–coil equilibrium significantly and that the volume change upon pressure unfolding is small and negative (–2.3 ml/mol). However, we find significant changes in the coordination of water molecules to the backbone carbonyls. This finding predicts that changes in the chemical shifts and IR spectra with pressure can be due to changes in coordination and not only changes in the helical content. A simulation of the IR spectrum shows that water coordination effects on frequency shifts are larger than changes due to elastic structural changes in the peptide.
Protein folding pathways from replica exchange simulations and a kinetic network model
Authors: Andrec Michael , Felts Anthony K. , Gallicchio Emilio , Levy Ronald M.
Published: March 2005

We present an approach to the study of protein folding that uses the combined power of replica exchange simulations and a network model for the kinetics. We carry out replica exchange simulations to generate a large (≈10
6
) set of states with an all-atom effective potential function and construct a kinetic model for folding, using an ansatz that allows kinetic transitions between states based on structural similarity. We use this network to perform random walks in the state space and examine the overall network structure. Results are presented for the C-terminal peptide from the B1 domain of protein G. The kinetics is two-state after small temperature perturbations. However, the coil-to-hairpin folding is dominated by pathways that visit metastable helical conformations. We propose possible mechanisms for the α-helix/β-hairpin interconversion.
Modeling gene and genome duplications in eukaryotes
Authors: Maere Steven , De Bodt Stefanie , Raes Jeroen , Casneuf Tineke , Van Montagu Marc , Kuiper Martin , Van de Peer Yves
Published: March 2005

Recent analysis of complete eukaryotic genome sequences has revealed that gene duplication has been rampant. Moreover, next to a continuous mode of gene duplication, in many eukaryotic organisms the complete genome has been duplicated in their evolutionary past. Such large-scale gene duplication events have been associated with important evolutionary transitions or major leaps in development and adaptive radiations of species. Here, we present an evolutionary model that simulates the duplication dynamics of genes, considering genome-wide duplication events and a continuous mode of gene duplication. Modeling the evolution of the different functional categories of genes assesses the importance of different duplication events for gene families involved in specific functions or processes. By applying our model to the
Arabidopsis
genome, for which there is compelling evidence for three whole-genome duplications, we show that gene loss is strikingly different for large-scale and small-scale duplication events and highly biased toward certain functional classes. We provide evidence that some categories of genes were almost exclusively expanded through large-scale gene duplication events. In particular, we show that the three whole-genome duplications in
Arabidopsis
have been directly responsible for >90% of the increase in transcription factors, signal transducers, and developmental genes in the last 350 million years. Our evolutionary model is widely applicable and can be used to evaluate different assumptions regarding small- or large-scale gene duplication events in eukaryotic genomes.
Color-blind fluorescence detection for four-color DNA sequencing
Authors: Lewis Ernest K. , Haaland Wade C. , Nguyen Freddy , Heller Daniel A. , Allen Matthew J. , MacGregor Robert R. , Berger C. Scott , Willingham Britain , Burns Lori A. , Scott Graham B. I. , Kittrell Carter , Johnson Bruce R. , Curl Robert F. , Metzker Michael L.
Published: March 2005

We present an approach called pulsed multiline excitation (PME) for measurements of multicomponent, fluorescence species and demonstrate its application in capillary electrophoresis for DNA sequencing. To fully demonstrate the advantages of PME, a fluorescent dye set has been developed whose absorption maxima span virtually the entire visible spectrum. Unlike emission wavelength-dependent approaches for identifying fluorescent species, the removal of the spectral component in PME confers a number of advantages including higher and normalized signals from all dyes present in the assay, the elimination of spectral cross-talk between dyes, and higher signal collection efficiency. Base-calling is unambiguously determined once dye mobility corrections are made. These advantages translate into significantly enhanced signal quality as illustrated in the primary DNA sequencing data and provide a means for achieving accurate base-calling at lower reagent concentrations.
Polarized Gene Expression Determines Woronin Body Formation at the Leading Edge of the Fungal Colony
Authors: Tey Wei Kiat , North Alison J. , Reyes Jose L. , Lu Yan Fen , Jedd Gregory
Published: March 2005

The Woronin body (WB) is a peroxisome-related organelle that is centered on a crystalline core of the HEX-1 protein, which functions to seal septal pores of filamentous ascomycetes in response to cellular damage. Here, we investigate the cellular and genetic control of WB-formation and show that polarized hex-1 gene expression determines WB-biogenesis at the growing hyphal apex. We find that intron splicing is coupled to efficient hex-1 gene expression and strikingly, when the yellow fluorescent protein was expressed from hex-1 regulatory sequences, we observed a fluorescent gradient that was maximal in apical cells. Moreover, endogenous hex-1 transcripts were specifically enriched at the leading edge of the fungal colony, whereas other transcripts accumulated in basal regions. Time-lapse confocal microscopy showed that HEX-1 crystals normally formed in the vicinity of the hyphal apex in large peroxisomes, which matured and were immobilized at the cell periphery as cells underwent septation. When the hex-1 structural gene was expressed from regulatory sequences of an abundant, basally localized transcript, WB-core formation was redetermined to basal regions of the colony, and these strains displayed loss-of-function phenotypes specifically in apical hyphal compartments. These results show that apically localized gene expression is a key determinant of spatially restricted WB-assembly. We suggest that this type of regulation may be widely used to determine cellular activity in apical regions of the fungal hypha.
DictyosteliumLIS1 Is a Centrosomal Protein Required for Microtubule/Cell Cortex Interactions, Nucleus/Centrosome Linkage, and Actin Dynamics
Authors: Rehberg Markus , Kleylein-Sohn Julia , Faix Jan , Ho Thi-Hieu , Schulz Irene , Gräf Ralph
Published: March 2005

The widespread LIS1-proteins were originally identified as the target for sporadic mutations causing lissencephaly in humans. Dictyostelium LIS1 (DdLIS1) is a microtubule-associated protein exhibiting 53% identity to human LIS1. It colocalizes with dynein at isolated, microtubule-free centrosomes, suggesting that both are integral centrosomal components. Replacement of the DdLIS1 gene by the hypomorphic D327H allele or overexpression of an MBP-DdLIS1 fusion disrupted various dynein-associated functions. Microtubules lost contact with the cell cortex and were dragged behind an unusually motile centrosome. Previously, this phenotype was observed in cells overexpressing fragments of dynein or the XMAP215-homologue DdCP224. DdLIS1 was coprecipitated with DdCP224, suggesting that both act together in dynein-mediated cortical attachment of microtubules. Furthermore, DdLIS1-D327H mutants showed Golgi dispersal and reduced centrosome/nucleus association. Defects in DdLIS1 function also altered actin dynamics characterized by traveling waves of actin polymerization correlated with a reduced F-actin content. DdLIS1 could be involved in actin dynamics through Rho-GTPases, because DdLIS1 interacted directly with Rac1A in vitro. Our results show that DdLIS1 is required for maintenance of the microtubule cytoskeleton, Golgi apparatus and nucleus/centrosome association, and they suggest that LIS1-dependent alterations of actin dynamics could also contribute to defects in neuronal migration in lissencephaly patients.
Mineralization of soft-part anatomy and invading microbes in the horseshoe crabMesolimulusfrom the Upper Jurassic Lagerstätte of Nusplingen, Germany
Authors: Briggs Derek E.G , Moore Rachel A , Shultz Jeffrey W , Schweigert Günter
Published: March 2005

A remarkable specimen ofMesolimulusfrom the Upper Jurassic (Kimmeridgian) of Nusplingen, Germany, preserves the musculature of the prosoma and associated microbes in three dimensions in calcium phosphate (apatite). The musculature ofMesolimulusconforms closely to that of modern horseshoe crabs. Associated with the muscles are patches of mineralized biofilm with spiral and coccoid forms. This discovery emphasizes the potential of soft-bodied fossils as a source for increasing our knowledge of the diversity of fossil microbes in particular settings.
Effects of temperature, body size and feeding on rates of metabolism in young‐of‐the‐year haddock
Authors: Peck M. A. , Buckley L. J. , Bengtson D. A.
Published: March 2005

The mean rate of oxygen consumption (routine respiration rate, RR, mg O2 fish−1 h−1), measured for individual or small groups of haddock Melanogrammus aeglefinus(3–12 cm standard length, LS) maintained for 5 days within flow‐through respiratory chambers at four different temperatures, increased with increasing dry mass (MD). The relationship between RR and MD was allometric (RR = α Mb) with b values of 0·631, 0·606, 0·655 and 0·650 at 5·0, 8·0, 12·0 and 15·0° C, respectively. The effect of temperature (T) and MD on mean RR was described by indicating a Q10 of 2·27 between 5 and 15° C. Juvenile haddock routine metabolic scope, calculated as the ratio of the mean of highest and lowest deciles of RR measured in each chamber, significantly decreased with temperature such that the routine scope at 15° C was half that at 5° C. The cost of feeding (RSDA) was c. 3% of consumed food energy, a value half that found for larger gadoid juveniles and adults.
Goosander predation and its potential impact on Atlantic salmon smolts in the River Tana estuary, northern Norway
Authors: Svenning M.‐A. , Fagermo S. E. , Barrett R. T. , Borgstrøm R. , Vader W. , Pedersen T. , Sandring S.
Published: March 2005

In the summers of 1981 and 2000, 288 goosandersMergus merganserwere sampled in the estuary of the River Tana in northern Norway, which has the largest wild Atlantic salmonSalmo salarstock in the world. Based on 2308 otoliths found in their stomach contents, sandeelsAmmodytessp. were found to be the dominant prey, and only one pair of Atlantic salmon otoliths was found. This suggested that goosanders were not significant predators on Atlantic salmon smolts in the estuary, probably because of the high abundance of sandeels and other marine prey fishes, at least in these particular years.