Growth and persistence of 17 annual medic (Medicago spp.) accessions on clay soils in central Queensland

Seventeen accessions of annual medics were evaluated on clay soil sites at Emerald, Theodore, Biloela and Mundubbera, central Queensland. Successful medics could have a role in both permanent and ley pastures. However, these are marginal areas for medics with winter (June-August) rainfalls of 80-100 mm. The accessions were selected on the basis of results in southern Queensland, a more favoured area for medics. There were 9 accessions of Medicago truncatula (barrel medic), 4 of M. scutellata (snail medic), 2 of M. polymorpha (burr medic) and 1 each of M. aculeata (keg medic) and M. orbicularis (button medic). Lucerne (M. sativa) cv. Trifecta was sown at 3 sites. All sites except Theodore were irrigated in the year of establishment (1993). The medic seedlings at Theodore died in 1993 and the trial was resown in 1994. Measurements were made of seed set in the first year and whenever it occurred in later years, seedling density in most years and yield when there was adequate growth. Selected measurements were made of soil seed reserves. Measurements ceased in 1998

Can current reanalyses accurately portray changes in Southern Annular Mode structure prior to 1979?

Early reanalyses are less than optimal for investigating the regional effects of ozone depletion on Southern Hemisphere (SH) high-latitude climate because the availability of satellite sounder data from 1979 significantly improved their accuracy in data sparse regions, leading to a coincident inhomogeneity. To determine whether current reanalyses are better at SH high-latitudes in the pre-satellite era, here we examine the capabilities of the European Centre for Medium-range Weather Forecasts (ECMWF) fifth generation reanalysis (ERA5), the Twentieth Century Reanalysis version 3 (20CRv3), and the Japanese Meteorological Agency (JMA) 55-year reanalysis (JRA-55) to reproduce and help explain the pronounced change in the relationship between the Southern Annular Mode (SAM) and Antarctic near-surface air temperatures (SAT) between 1950 and 1979 (EARLY period) and 1980–2020 (LATE period). We find that ERA5 best reproduces Antarctic SAT in the EARLY period and is also the most homogeneous reanalysis across the EARLY and LATE periods. ERA5 and 20CRv3 provide a good representation of SAM in both periods with JRA-55 only similarly skilful in the LATE period. Nevertheless, all three reanalyses show the marked change in Antarctic SAM-SAT relationships between the two periods. In particular, ERA5 and 20CRv3 demonstrate the observed switch in the sign of the SAM-SAT relationship in the Antarctic Peninsula: analysis of changes in SAM structure and associated meridional wind anomalies reveal that in these reanalyses positive SAM is linked to cold southerly winds during the EARLY period and warm northerly winds in the LATE period, thus providing a simple explanation for the regional SAM-SAT relationship reversal

A Possible Crypto-Superconducting Structure in a Superconducting Ferromagnet

We have measured the dc and ac electrical and magnetic properties in various magnetic fields of the recently reported superconducting ferromagnet RuSr2GdCu2O8. Our reversible magnetization measurements demonstrate the absence of a bulk Meissner state in the compound below the superconducting transition temperature. Several scenarios that might account for the absence of a bulk Meissner state, including the possible presence of a sponge-like non-uniform superconducting or a crypto-superconducting structure in the chemically uniform Ru-1212, have been proposed and discussed.Comment: 8 pages, 5 PNG figures, submitted to Proceedings of the 9th Japan-US Workshop on High-Tc Superconductors, Yamanashi, Japan, October 13-15, 1999; accepted for publication in Physica C (December 24, 1999

The role of genetic resources in developing improved pastures in semi-arid and subhumid northern Australia

The role of introduced pasture species in the drier areas of northern Australia, and the need for genetic resource support, are reviewed. Introduced legumes are the key to improving animal production from the less fertile duplex soils, whereas introduced grasses have been of greater importance on the more fertile and heavier-textured soils. There is increasing recognition of the need for legumes adapted to clay soils. All of the successful legume and grass cultivars are of exotic species. The development of useful cultivars and the role of the Australian Tropical Forages Genetic Resource Centre are discussed, using the recently released pasture legume Desmanthus virgatus as an example

Graze to grain - measuring and modelling the effects of grazed pasture leys on soil nitrogen and sorghum yield on a Vertosol soil in the Australian subtropics

Highly productive sown pasture systems can result in high growth rates of beef cattle and lead to increases in soil nitrogen and the production of subsequent crops. The nitrogen dynamics and growth of grain sorghum following grazed annual legume leys or a grass pasture were investigated in a no-till system in the South Burnett district of Queensland. Two years of the tropical legumes Macrotyloma daltonii and Vigna trilobata (both self regenerating annual legumes) and Lablab purpureus (a resown annual legume) resulted in soil nitrate N (0-0.9 m depth), at sorghum sowing, ranging from 35 to 86 kg/ha compared with 4 kg/ha after pure grass pastures. Average grain sorghum production in the 4 cropping seasons following the grazed legume leys ranged from 2651 to 4012 kg/ha. Following the grass pasture, grain sorghum production in the first and second year was < 1900 kg/ha and by the third year grain yield was comparable to the legume systems. Simulation studies utilising the farming systems model APSIM indicated that the soil N and water dynamics following 2-year ley phases could be closely represented over 4 years and the prediction of sorghum growth during this time was reasonable. In simulated unfertilised sorghum crops grown from 1954 to 2004, grain yield did not exceed 1500 kg/ha in 50% of seasons following a grass pasture, while following 2-year legume leys, grain exceeded 3000 kg/ha in 80% of seasons. It was concluded that mixed farming systems that utilise short term legume-based pastures for beef production in rotation with crop production enterprises can be highly productive

Which grass for where?

Grasses comprise a relatively old group of flowering plants found in most of the land environments of the world. They vary from low-growing herbs to tall, woody bamboos, and have developed a variety of mechanisms to survive under a wide range of conditions. This has led to variation in growth habit, soil preferences, drought and flood tolerance etc. which humans can use to their benefit. This paper discusses the development of diversity within the grasses, and describes the characteristics of a number of exotic warm season species that can be used for forage, soil conservation and soil improvement in the subhumid subtropics of Australia

Early stage evaluation of tropical legumes on clay soils at three sites in central and southern inland Queensland

Over 150 legume accessions were evaluated in small plots at three clay soil sites in south-central inland Queensland for use in either permanent or ley pastures. Legumes were either sown alone, or more usually with a companion grass, in 1992/93, 1993/94 and 1994/95 at sites near Mundubbera, Theodore and Emerald. Annual measurements of yield and density were made until May 1998. Summer/autumn rainfall was consistently below average in the three years of sowing. Legumes best adapted for use in permanent pastures were Desmanthus spp. and Stylosanthes seabrana, both of which were released in the 1990s, and Indigofera schimperi. While I. schimperi showed outstanding persistence and productivity, it has not been released for commercial use, as it was often not adequately grazed. It has been eliminated from the trial sites. Some accessions of desmanthus showed some promise as alternatives to the three lines currently mixed together in the commercially released “Jaribu” desmanthus. None of the annual species tested was superior to Lablab purpureus for use as an annual legume in leys, but Macroptilium bracteatum showed some promise as a short term perennial for use in ley pastures

Growth responses of Desmanthus virgatus to inoculation with Rhizobium strain cb3126. II. A field trial at 4 sites in south-east Queensland

Growth of Desmanthus virgatus cvv. Marc, Bayamo and Uman, inoculated with Rhizobium strain CB3126, was compared with that of uninoculated and inoculated + nitrogen-fertilised plants at 4 sites in south-east Queensland over a 3-year period. Supplementary irrigation was used to ensure prompt establishment. The proportion of nodules due to the inoculum strain was determined using serological methods and the proportion of total plant nitrogen arising from biological fixation in the second and third years was estimated using the natural abundance method. Top growth was increased significantly by inoculation at 3 sites in the first year and at 1 site in the second year. Growth increases relative to uninoculated plants varied from 34–313% and appeared to depend on the prevalence of indigenous strains and soil nitrogen level. The inoculum accounted for few ( 94%) of the nodules formed in soils in which nodulation of uninoculated plants was high, medium and low, respectively. The proportion of total nitrogen due to biological nitrogen fixation in the second and third years ranged from 0% in a highly fertile soil to 38–98% in 3 soils of low-moderate fertility. The ability of strain CB3126 to increase growth of desmanthus in some soils was confirmed in these field trials. Inoculation of desmanthus seed with an effective strain of Rhizobium such as CB3126 is recommended

Seasonal changes in pasture quality and diet selection and their relationship with liveweight gain of steers grazing tropical grass and grass-legume pastures in northern Australia.

The variation in liveweight gain in grazing beef cattle as influenced by pasture type, season and year effects has important economic implications for mixed crop-livestock systems and the ability to better predict such variation would benefit beef producers by providing a guide for decision making. To identify key determinants of liveweight change of Brahman-cross steers grazing subtropical pastures, measurements of pasture quality and quantity, and diet quality in parallel with liveweight were made over two consecutive grazing seasons (48 and 46 weeks, respectively), on mixed Clitoria ternatea/grass, Stylosanthes seabrana/grass and grass swards (grass being a mixture of Bothriochloa insculpta cv. Bisset, Dichanthium sericeum and Panicum maximum var. trichoglume cv. Petrie). Steers grazing the legume-based pastures had the highest growth rate and gained between 64 and 142 kg more than those grazing the grass pastures in under 12 months. Using an exponential model, green leaf mass, green leaf %, adjusted green leaf % (adjusted for inedible woody legume stems), faecal near infrared reflectance spectroscopy predictions of diet crude protein and diet dry matter digestibility, accounted for 77, 74, 80, 63 and 60%, respectively, of the variation in daily weight gain when data were pooled across pasture types and grazing seasons. The standard error of the regressions indicated that 95% prediction intervals were large (+/- 0.42-0.64 kg/head.day) suggesting that derived regression relationships have limited practical application for accurately estimating growth rate. In this study, animal factors, especially compensatory growth effects, appeared to have a major influence on growth rate in relation to pasture and diet attributes. It was concluded that predictions of growth rate based only on pasture or diet attributes are unlikely to be accurate or reliable. Nevertheless, key pasture attributes such as green leaf mass and green leaf% provide a robust indication of what proportion of the potential growth rate of the grazing animals can be achieved