Pastures In South-eastern Australia Research Articles

Soil pH preferences and the influences of soil type and temperature on the survival and growth of Aporrectodea longa (Lumbricidae)The 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

Summary The potential of the deep-burrowing earthworm, Aporrectodea longa , to improve the functional diversity of soil communities, soil properties and plant production if introduced in high rainfall pastures in south-eastern Australia has been recognised previously. This paper reports on suitable soil types, pH and temperature regimes for the culturing of A. longa and develops predictions as to where A. longa might best establish. Laboratory experiments show that A. longa will survive and grow to maturity when reared in the laboratory in a commercially available sand: loam mix, supplemented with sheep dung for food. Survival, development of cocoons and growth of hatchling earthworms was, overall, optimal at 15 °C. Few cocoons survived two months in air-dried soil. Earthworms showed a strong aversion to soil pH below 4.5. The development time required for cocoons at soil temperatures likely to be experienced in the field in southern Australia (e.g. 15–20 weeks at 10 °C) is discussed in terms of likely establishment success.

Ecology of Nassella neesiana, Chilean needle grass, in pastures on the Northern Tablelands of New South Wales. I. Seed production and dispersal

Nassella neesiana (Trin. & Rupr.) Barkworth (Chilean needle grass) originated in South America and is now a widespread weed in pastures in south-eastern Australia. To date, little research on the biology of N.�neesiana has been undertaken in Australia. This study investigated several aspects of the biology of N. neesiana in pastures on the Northern Tablelands of New South Wales. The main flowering period for N. neesiana in Australia was shown to extend from November to February and is similar to that in South America. Potential for production of panicle seeds was large and varied from 1584 seeds/m2 in 1995 to 22 203 seeds/m2 in 1996 as a result of changes in the density of flowering tillers per unit area. Nassella neesiana produced a further 7.2 cleistogenes (hidden seeds in the flower stem) on average per tiller. Hence, total potential seed production (panicle seeds and cleistogenes) was 28 282 and 8036 seeds/m2 in 1996 and 1997, with the cleistogenes accounting for 21.5 and 26.1% of the total respectively. Furthermore, the production of cleistogenes was not affected by clipping flowering tillers at 3 different heights. Three possible dispersal mechanisms of N. neesiana seeds were investigated. Adherence of seeds to the wool appeared to be the most effective. Twenty-five per cent of seeds that were picked up naturally in the wool of sheep after grazing in a paddock of N. neesiana, remained after 5 months. Shearing just before seed set reduced the number of seeds adhering to the wool. An average of 1.7% of panicle seeds and 5.3% of cleistogenes fed to Angus steers passed through the animal intact within 4 days, but <50% of these seeds were viable. The majority of seeds recovered from a wind dispersal experiment were within 1 m of the parent plant and the furthermost seed was 2.8 m away. The implications of these results for management are discussed.

Influence of sewage waste on the abundance of earthworms in pastures in south-eastern Australia

The use of biosolids in pasture-based livestock production is being considered for disposal of human sewage waste in New South Wales (NSW), Australia. An experiment was commenced in 1992 near Goulburn to assess some of the risks associated with the application of dewatered biosolids (DWB) to pastures. DWB was applied to infertile, acidic soils at the rates of 30, 60 and 120 tonnes ha –1 and compared to a fertilised and limed control. In 1999, earthworm abundance was low in control plots (7.5 worms m –2). Application of DWB increased abundance, peaking at 60.0 worms m –2 in the 30 tonnes ha –1 treatment, with no significant difference between the three rates of DWB. The earthworm fauna consisted of exotic Lumbricidae and Acanthodrilidae (most commonly Aporrectodea trapezoides (Duges) and Microscolex dubius (Fletcher)) and native Megascolecidae (most commonly Spenceriella macleayi (Fletcher)). Species composition varied with rate of DWB. Two lumbricids ( A. longa (Ude) and A. caliginosa (Sav.)), which were not previously present at the site, were inoculated together in replicated cages in each of the DWB treatments. Three months later, more A. longa were recovered than A. caliginosa (90% cf. 69%), but there was no influence of DWB on the survival of either species. The total biomass of recovered worms also did not vary in relation to DWB. The inoculation of A. longa and A. caliginosa increased pasture production in all the fields (overall increase = 46%). The inoculation of A. longa and A. caliginosa also decreased the abundance and biomass of local earthworms.

Does the deep-burrowing earthworm, Aporrectodea longa, compete with resident earthworm communities when introduced to pastures in south-eastern Australia?

Pastures in southern Australia are dominated by endogeic earthworms such as Aporrectodea caliginosa (Sav.). Introductions of the anecic earthworm, A. longa (Ude), which is mostly restricted to Tasmania at present, are likely to increase the functional diversity of local communities and thereby enhance plant production and agricultural sustainability. However, the potential impact of A. longa on resident earthworm communities first needs assessing. Glasshouse and field experiments reported here suggested that A. longa can reduce the abundance and biomass of A. caliginosa, but that these effects are likely to be offset by overall increases in worm abundance. There was no evidence to suggest that species richness was reduced by A. longa introduction.

Nitrate leaching loss under annual and perennial pastures with and without lime on a duplex (texture contrast) soil in humid southeastern Australia

SummaryMineral N accumulates in autumn under pastures in southeastern Australia and is at risk of leaching as nitrate during winter. Nitrate leaching loss and soil mineral N concentrations were measured under pastures grazed by sheep on a duplex (texture contrast) soil in southern New South Wales from 1994 to 1996. Legume (Trifolium subterraneum)‐based pastures contained either annual grass (Lolium rigidum) or perennial grasses (Phalaris aquatica and Dactylis glomerata), and had a control (soil pH 4.1 in 0.01 m CaCl2) or lime treatment (pH 5.5). One of the four replicates was monitored for surface runoff and subsurface flow (the top of the B horizon), and solution NO3– concentrations.The soil contained more mineral N in autumn (64–133 kg N ha−1 to 120 cm) than in spring (51–96 kg N ha−1), with NO3– comprising 70–77%. No NO3– leached in 1994 (475 mm rainfall). In 1995 (697 mm rainfall) and 1996 (666 mm rainfall), the solution at 20 cm depth and subsurface flow contained 20–50 mg N l−1 as NO3– initially but < 1 mg N l−1 by spring. Nitrate‐N concentrations at 120 cm ranged between 2 and 22 mg N l−1 during winter. Losses of NO3– were small in surface runoff (0–2 kg N ha−1 year−1). In 1995, 9–19 kg N ha−1 was lost in subsurface flow. Deep drainage losses were 3–12 kg N ha−1 in 1995 and 4–10 kg N ha−1 in 1996, with the most loss occurring under limed annual pasture. Averaged over 3 years, N losses were 9 and 15 kg N ha−1 year−1 under control and limed annual pastures, respectively, and 6 and 8 kg N ha−1 year−1 under control and limed perennial pastures. Nitrate losses in the wet year of 1995 were 22, 33, 13 and 19 kg N ha−1 under the four respective pastures. The increased loss of N caused by liming was of a similar amount to the decreased N loss by maintaining perennial pasture as distinct from an annual pasture.

Long-term change in the economic productivity of four major pasture categories on the south-eastern Tablelands of New South Wales

The perception of change or decline in the productivity of temperate pastures in south-eastern Australia is an important concern to livestock producers and pasture scientists. Much of this concern relates to reductions in the proportions of desirable species in the composition of pasture systems as a result of increased soil and weed problems. The purpose of this paper is to investigate trends in the long-term economic productivity of four categories of temperate pastures (all introduced pastures, introduced perennial grasses, introduced legumes and all native pastures) on the central and southern tablelands of New South Wales. The results provide evidence of economic productivity decline in the all introduced pastures category in relation to sheep production, but this has been due to productivity decline in the dominant legume component of the introduced pastures. In contrast, there has been strong growth in the economic productivity of the introduced perennial grass pastures. Abnormally high beef cattle numbers in the mid-1970s appear to have created an illusion of high productivity and subsequent decline in all introduced pastures. In contrast, the economic productivity of the native pastures which are the bulk of the region's grazing areas, has fallen substantially.

The pest status and distribution of three cryptic blue oat mite species (Penthaleus spp.) and redlegged earth mite (Halotydeus destructor) in southeastern Australia.

Earth mites are pests of crops and pastures in southeastern Australia. Recent studies show differences between earth mite species in their mode of reproduction, preferred hosts and pesticide tolerance. This paper examines the distribution and pest status of each species. The southeastern Australian distribution for each species is mapped, incorporating new data from eastern New South Wales, South Australia and Tasmania. A new population of an undescribed species previously identified from northwestern Victoria was found in northern New South Wales. CLIMEX was used to identify climatic factors limiting the distribution of P. major and P. falcatus, the most broadly distributed species. This analysis suggests tolerance to heat and desiccation limits the inland distribution of these two species. A three-year survey of agricultural outbreaks indicates that all Penthaleus species are major agricultural pests although their pest status on crop types appears to differ. All species contributed to chemical control failures. However P. falcatus, previously identified in laboratory tests as having increased tolerance to pesticides, was the most common species associated with control failures. A laboratory experiment indicated that mites are sometimes pests on crops on which they cannot persist for a generation. Results are discussed with respect to management of these agricultural pests.

Persistence and productivity of perennial ryegrass in sheep pastures in south-western Victoria: a review

Loss of perennial ryegrass (Lolium perenne L.) from the pasture within several years of sowing is a common problem in the higher rainfall (550–750 mm annual rainfall), summer-dry regions of south-eastern Australia. This pasture grass came to Australia from northern Europe, where it mostly grows from spring to autumn under mild climatic conditions. In contrast, the summers are generally much drier and hotter in this region of south-eastern Australia. This ‘mismatch’ between genotype and environment may be the fundamental reason for the poor persistence. There is hope that the recently released cultivars, Fitzroy and Avalon, selected and developed from naturalised ryegrass pastures in south-eastern Australia for improved winter growth and persistence will improve the performance of perennial ryegrass in the region. Soon-to-be released cultivars, developed from Mediterranean germplasm, may also bridge the climatic gap between where perennial ryegrass originated and where it is grown in south-eastern Australia. Other factors that influence perennial ryegrass persistence and productivity can be managed to some extent by the landholder. Nutrient status of the soil is important since perennial ryegrass performance improves relative to many other pasture species with increasing nitrogen and phosphorus supply. It appears that high soil exchangeable aluminium levels are also reducing ryegrass performance in parts of the region. The use of lime may resolve problems with high aluminium levels. Weeds that compete with perennial ryegrass become prevalent where bare patches occur in the pasture; they have the opportunity to invade pastures at the opening rains each year. Maintaining some herbage cover over summer and autumn should reduce weed establishment. Diseases of ryegrass are best managed by using resistant cultivars. Insect pests may be best managed by understanding and monitoring their biology to ensure timely application of pesticides and by manipulating herbage mass to alter feed sources and habitat. Grazing management has potential to improve perennial ryegrass performance as frequency and intensity of defoliation affect dry matter production and have been linked to ryegrass persistence, particularly under moisture deficit and high temperature stress. There is some disagreement as to the merit of rotational stocking with sheep, since the results of grazing experiments vary markedly depending on the rotational strategy used, climate, timing of the opening rains, stock class and supplementary feeding policy. We conclude that flexibility of grazing management strategies is important. These strategies should be able to be varied during the year depending on climatic conditions, herbage mass, and plant physiology and stock requirements. Two grazing strategies that show potential are a short rest from grazing the pasture at the opening rains until the pasture has gained some leaf area, in years when the opening rains are late. The second strategy is to allow ryegrass to flower late in the season, preventing new vegetative growth, and perhaps allowing for tiller buds to be preserved in a dormant state over the summer. An extension of this strategy would be to delay grazing until after the ryegrass seed heads have matured and seed has shed from the inflorescences. This has the potential to increase ryegrass density in the following growing season from seedling recruitment. A number of research opportunities have been identified from this review for improving ryegrass persistence. One area would be to investigate the potential for using grazing management to allow late development of ryegrass seed heads to preserve tiller buds in a dormant state over the summer. Another option is to investigate the potential, and subsequently develop grazing procedures, to allow seed maturation and recruitment of ryegrass seedlings after the autumn rains.

Soil water extraction by dryland crops, annual pastures, and lucerne in south-eastern Australia

The extraction of soil water by dryland crops and pastures in south-eastern Australia was examined in 3 studies. The first was a review of 13 published measurements of soil water-use under wheat at several locations in southern New South Wales. Of these, 8 showed significantly more water extracted by crops managed with increased nitrogen supply or growing after a break crop. The mean additional soil water extraction in response to break crops was 31 mm and to additional N was 11 mm. The second study used the SIMTAG model to simulate growth and water-use by wheat in relation to crop management at Wagga Wagga. The model was set up to simulate crops that produced either average district yields or the potential yields achievable with good management. When simulated over 50 years of weather data, the combined water loss as drainage and runoff was predicted to be 67 mm/year for poorly managed crops and 37 mm for well-managed crops. Water outflow was concentrated in 70% of years for the poorly managed crops and 56% for the well-managed crops. In those years the mean losses were estimated to be 95 mm and 66 mm, respectively. The third study reports soil water measured twice each year during a phased pasture–crop sequence over 6.5 years at Junee. Mean water content of the top 2.0 m of soil under a lucerne pasture averaged 211 mm less than under a subterranean clover-based annual pasture and 101 mm less than under well-managed crops. Collectively, these results suggest that lucerne pastures and improved crop management can result in greater use of rainfall than the previous farming systems based on annual pastures, fallows, and poorly managed crops. The tactical use of lucerne-based pastures in sequence with well-managed crops can help the dewatering of the soil andreduce or eliminate the risk of groundwater recharge.

The pathogenesis and control of diarrhoea and breech soiling in adult Merino sheep

Diarrhoea and soiling of the breech with faeces (`winter scours') is a serious problem in adult Merino sheep grazing improved pastures in south-eastern Australia during winter and spring. This occurs even on farms where gastro-intestinal nematodes are effectively controlled. It was shown that winter scours was associated with the ingestion of trichostrongylid larvae, and that host factors were important in determining susceptibility to this syndrome. No differences were detected in the protective immune response of affected and unaffected sheep to gut nematodes. However, affected sheep had a hypersensitive inflammatory reaction in the pylorus and upper jejunum, characterised by the infiltration of significantly more eosinophils and changed lymphocyte populations. The changes in the lymphocyte populations included a reduced number of CD8+ cells, increased CD4+:CD8+ T-cell ratio, and significantly reduced numbers of cells reacting to interferon-gamma. High doses of infective larvae (20 000/week of Ostertagia circumcincta and Trichostrongylus vitrinus) did not induce diarrhoea in sheep not susceptible to winter scours. In contrast, only low doses (2000/week) initiated scouring in sheep selected as being susceptible to winter scours. Therefore, even considerably improved worm control programmes, including the selection of sheep with increased resistance to gut nematodes, will not prevent winter scours. Rather, phenotypic culling and genetic selection, to remove sheep susceptible to the hypersensitivity inflammatory response, is proposed as the most suitable long-term control strategy.

Survival and biomass of exotic earthworms, Aporrectodea spp. (Lumbricidae), when introduced to pastures in south-eastern Australia

The earthworm fauna of pastures in south-eastern Australia is dominated by exotic lumbricid earthworms, in particular the endogeic species, Aporrectodea caliginosa and A. trapezoides. Anecic species such as A. longa are very rare. All 3 species were introduced within cages in 10 pastures on a range of soil types within the region. Five months later, A. longa had generally survived the best and A. trapezoides the worst. The survivals and weights of individual worms varied between sites for all 3 species. The survivals of A. caliginosa and A. longa, and to a lesser extent A. trapezoides, were positively correlated with soil clay content. The weights of A. caliginosa and A. longa, but not A. trapezoides, were positively correlated with soil P content. The survivals and weights of A. longa and A. trapezoides and the weights only of A. caliginosa decreased with increasing inoculation density, suggesting increased intraspecific competition for resources, particularly in the first two species. A. longa reduced the abundance and biomass of the exotic acanthodrilid earthworm, Microscolex dubius, at one site, and the total biomass of 3 native megascolecid species at another, when these latter species occurred as contaminants in A. longa cages. The addition of lime had no effect on the survivals and weights of A. caliginosa, A. longa, and A. trapezoides, although the soils were acid at the sites tested. The addition of sheep dung increased the survival and weights of some species at some sites. Mechanical disturbance of the soil within cages reduced the survivals of A. longa and A. trapezoides. A. longa was released without being caged at 25 sites within one pasture in South Australia. Four years later, it was recovered at all release points. A. longa has the potential to colonise pastures widely throughout the higher rainfall regions of south-eastern Australia.

Agrostis castellana (Poaceae), Dominant Agrostis Species, Found in Bent Grass Pastures in South-eastern Australia

There is considerable uncertainty that the traditional identification of bent grasses in south-eastern Australia as Agrostis capillaris L. (Syn. Agrostis tenuis Sibth.) is correct, due to a history of confusing nomenclature and mis-identification. Bent grass is considered a weed of pastures in the high-rainfall zone of south-eastern Australia and thus the correct identity of bent grass may have implications for its management and control. Populations of bent grass were sampled from 42 pastures in south-eastern Australia and Agrostis castellana Boiss. et Reuter, rather than A. capillaris, was found to be the dominant species of Agrostis in 33 out of 42 bent grass pastures sampled. Five of the nine pastures sampled in Tasmania contained A. capillaris as opposed to only 1 of the 33 pastures sampled in Victoria. Agrostis castellana had not been identified in Victoria or Tasmania prior to this work. Since A. castellana grows more vigorously by rhizomes than A. capillaris, control measures recommended for A. capillaris may not be relevant for bent grass pastures in south-eastern Australia. Ligule length, ligule width and width of lamina, measured to determine whether species of bent grass could be easily distinguished in the field, did not distinguish adequately between A. castellana and A. capillaris.

Genetic variation for seasonal herbage yield, growth habit, and condensed tannins in Lotus pedunculatus Cav. and Lotus corniculatus L.

Lotus pedunculatus (greater lotus) and L. corniculatus (birdsfoot trefoil) are perennial forages with potential to improve the legume content of pastures in south-eastern Australia. A collection of 39 accessions of each species was grown at 3 localities to assess the degree of genetic and genotype locality interaction components of variance for herbage yield, plant height, and width, the rate of reproductive development, and condensed tannin concentration as a prelude to forming strategies for genetic improvement. Rhizome development in L. pedunculatus and seed yields in both species were recorded at a single locality. The genetic variance component for herbage yield, plant height, and condensed tannins was significant for all characters, whereas the genotype × locality variance component was generally of lower magnitude. Grouping of accessions by geographic origin revealed important associations between characters. These associations were supported by strong positive genetic correlations. In L. pedunculatus, Portuguese accessions combined high autumn herbage yield with a tall plant type, a sparsely rhizomatous growth habit, high seed yield, and high condensed tannins. In L. corniculatus, prostrate growth habit was associated with high condensed tannins in accessions from Spain but was associated with low condensed tannins in Russian accessions. Principal components analysis of data for geographic groups of L. pedunculatus showed a positive association between means and variances, suggesting that selection within groups should be effective in producing cultivars with high herbage yield and low condensed tannins. In L.corniculatus, the positive genetic correlation between herbage yield and plant height suggested that hybridisation and selection would be required to produce a cultivar that would be more persistent under grazing.

Distribution and forms of phosphorus and aluminum in acidic topsoils under pastures in south-eastern Australia

The vertical distributions of pH, and forms of phosphorus (P) and aluminium (Al) in acidic topsoils (0-100 mm depth) under pastures were examined at 15 sites in New South Wales and Victoria. The soils were characterized by shallow surface strata of moderate pH, high P and low Al concentrations overlying more acidic, P-deficient and Al-rich subsurface strata. Significant amounts (35-65%) of the total P in acidic pasture topsoils were present in organic forms (Po). Some 20-40% of this Po was extractable using 0.5 M NaHCO3, and is regarded as easily mineralizable and a potential source of P for plant uptake. Substantial amounts of Al were present in crystalline and non-crystalline oxides (2000- 6000 mg kg-1) and complexed to organic matter (up to 400 mg kg-1). The amount of aluminium extracted using reagents commonly accepted to indicate Al toxicity in soils (1 M KCl and 0.01 M CaCl2) was not related to the amounts of those Al forms (extracted by ammonium oxalate, sodium citrate-dithionite) typically identified in pedological and mineralogical studies. Sampling and analysis of soils for determining P fertilizer requirements and diagnosing acidity and related problems (e.g. Al toxicity, Ca deficiency) should take into account the vertical heterogeneity in soil properties in the top 100 mm of the profile.

Studies of field populations of rhizobium: Effectiveness of strains of rhizobium trifolii associated with trifolium subterraneum L. pastures in South-Eastern Australia

Field populations of Rhizobiuin trifollii from eight regions in south-eastern Australia were sampled over a period of 5 years from 1966 to 1970. The R. trifolii isolates were tested under bacteriologically-and environmentally-controlled conditions for effectiveness of nitrogen fixation in combination with Trifalium subterraneum L. cv. Bacchus Marsh; the effective strain TA1 was used as a standard of comparison. Mean effectiveness of the R. trifolii populations for any region at any sampling varied between 62 and 93 percent of the effectiveness of the standard strain. The principal feature was the large variability within sampling sites, between sites within paddocks, and between paddocks within regions. In addition there was some variability with time in the range of effectiveness values of isolates within a site and in the absolute values for both sites and paddocks. Effectiveness values were not related to soil pH, size of population of R. trifolii, inoculation procedure at sowing, age of pasture, annual rate of fertilizer application, or mean annual rainfall.

An ecological study of the pasture scarab Aphodius Howitti hope.

The larval stage of Aphodius howitti Hope is a pest of improved and sown pastures in south-eastern Australia. The great increase in pasture improvement and of stocking rates over the past 25-30 years have favoured the development of high numbers of this insect, largely because of its preference for leguminous pasture species, especially subterranean clover (Trifolium subterraneum L.). This paper describes a general study of the life-cycle, behaviour, food, and oviposition site preferences of the species and includes a discussion of the mortality factors likely to be of significance in regulating its numbers. The species has an annual life-cycle. Studies on its biology revealed that adult females lay two distinct batches of eggs. The larger batch (c. 35 eggs) is laid before the female feeds in dung, sometimes even before flight; the smaller (c . 15 eggs), after feeding. The presence of dung is therefore not necessary for the survival of the species which is often found at high densities in ungrazed turf. The factors initiating and influencing flight activity were studied in detail. Initiation is triggered by light of a particular intensity; the time of appearance of beetles in flight can be forecast accurately in relation to the time of sunset. Flights are favoured by high temperature, high soil moisture, and by low wind velocity. Unfed beetles fly upwind towards dung pads. Gravid females execute a circling, exploratory flight; they appear to seek out comparatively bare situations for oviposition and usually enter the soil through small cracks such as are made by germinating clover plants.