Pastures In South-eastern Australia Research Articles

Legume options for summer-active pastures in a temperate rainfall environment of south-eastern Australia

Context High-quality, summer-active pastures could improve meat production in south-eastern Australia by facilitating livestock finishing over summer, with legumes critical for enhancing the nutritive value of pasture mixes. Available legumes vary in their ability to withstand moisture stress and grazing. Aims We aimed to identify legumes suitable for a summer–autumn finishing system. Methods We tested pure swards of 12 cultivars across eight legume species in replicated small-plot experiments at Goulburn and Bombala, New South Wales, assessing productivity, persistence and warm-season nutritive characteristics over 2–3 years. Key results Lucerne (Medicago sativa) was clearly the most productive species during summer and outperformed the clovers (Trifolium spp.) in terms of persistence and productivity throughout most of the experimental period at both sites, except during autumn 2021 after high rainfall in March. Caucasian clover (T. ambiguum) was also highly persistent at both sites. Talish clover (T. tumens) and strawberry clover (T. fragiferum) were more persistent than white clover (T. repens) and red clover (T. pratense). White clover recovered strongly under high rainfall after drought, whereas red clover established rapidly but showed less capacity for post-drought recovery. Hybrid Caucasian × white clover was the least productive legume. Alternative clover species sometimes had slightly lower values of nutritive characteristics than white clover; red clover sometimes had distinctly lower values. Conclusions Lucerne performed best but several clovers were also productive, persistent and of high nutritive value over the summer–autumn period. Implications Talish, Caucasian and strawberry clovers warrant further investigation for inclusion in summer-active pastures in south-eastern Australia.

Beneficial invertebrates of dairy pastures in south-eastern Australia

Context The Australian dairy industry largely relies on grass-based pastures to feed cattle, yet these pastures also host dynamic invertebrate communities that can damage or benefit pasture productivity. While Australian dairy managers have traditionally focused on invertebrates that damage pastures (i.e. pests), invertebrates that provide valuable ecosystem services by acting as natural enemies to pests or delivering other beneficial functions (e.g. nutrient cycling) have received less attention. Aim Surveying the natural enemies and other beneficial invertebrate communities in pastures across seven Australian dairy regions and to explore how environmental and farm management factors impact these. Method Fifty seven pastures samples were collected during spring and autumn over two years. In doing so, we identified and counted 2 661 315 invertebrates or invertebrate colonies. Key results We found natural enemies and other beneficial invertebrate communities have a similar taxonomic composition across regions, with a small number of taxa dominating all regions, and rainfall the most consistent environmental driver in the abundance of these dominant taxa. Conclusions Farm management strategies to maintain or promote existing communities of beneficial taxa will likely be similar across regions. Associations between invertebrate communities suggest pest communities may indirectly impact the abundance and/or diversity of natural enemies and other beneficial invertebrates. Implications Although still an early step, our findings provide important baseline information that can be used to provide dairy managers with strategies to promote communities of beneficial invertebrates, and consequently maximise the benefits these invertebrates provide.

Non-Native Eragrostis curvula Impacts Diversity of Pastures in South-Eastern Australia Even When Native Themeda triandra Remains Co-Dominant.

Lowland grassy woodlands in Australia’s south-east face reductions in native plant diversity because of invasion by non-native plants. We compared the relative abundance and diversity of plant species among sites dominated by the native Kangaroo grass (KG) Themeda triandra with sites co-dominated by the non-native African lovegrass (ALG) Eragrostis curvula and KG. We found significant differences in plant species composition depending on the dominant species. Furthermore, our results revealed differences in several diversity parameters such as a lower species richness and forb diversity on sites co-dominated by ALG and KG. This was the case despite the functional similarity of both ALG and KG—both C4 perennial tussock grasses of a similar height. Therefore, our results highlight the critical function of the native KG in maintaining and enhancing the target plant species composition and diversity within these grassy woodlands. Herbivore grazing potentially impacts on the abundance of the dominant grass and forb species in various ways, but its impact likely differs depending on their evolutionary origin. Therefore, disentangling the role of individual herbivore groups (native-, non-native mammals, and invertebrates) on the plant community composition of the lowland grassy woodlands is essential to find appropriate grazing regimes for ALG management in these ecosystems.

The effect of pasture molluscicide on small lungworm infections and the productivity of grazing lambs

The aim of this study was to assess the effect of pasture molluscicide treatment on the prevalence and severity of small lungworm infections, and the productivity of lambs grazing improved pastures in southeastern Australia. A randomised control field trial of 260 Merino-cross lambs was conducted on a commercially managed farm in South Australia with a history of high small lungworm prevalence. Separate groups of lambs rotationally grazed irrigated lucerne paddocks treated with iron chelate molluscicide or untreated control paddocks. Lambs were monitored every 2–6 weeks from weaning until slaughter with liveweight, lungworm and gastrointestinal nematode infection status measured. At slaughter indicators of small lungworm infection via inspection and carcass characteristics were assessed. The density of the intermediate host snail and lucerne pasture availability were also measured. There was a higher population of adult Prietocella barbara molluscs in the Control paddocks compared to the Treatment paddocks after molluscicide had been applied and prior to grazing commencing (206 vs. 14 snails/m2, respectively; P = 0.03; 95 % CI 8, 528). However, the overall mollusc density was similar between Control and Treatment. The prevalence of small lungworm infections was quite low during the trial (0–13 %), in both Control and Treatment lambs, except at day 94 when 48 % of 28 Control lambs were positive compared to none of 27 Treatment lambs (P < 0.001; 95 % CI 30, 66). A similar proportion of Treatment and Control lambs had evidence of small lungworm infection lesions at slaughter (both 67.8 %). Control lambs grew slightly faster than Treatment lambs, with an average daily gain of 202 (± 3 SEM) g/head/day for Control and 190 (± 4 SEM) for Treatment (P < 0.001) during the 112-day trial.Despite historic evidence of very high prevalence of lungworm infection in this region of southeastern Australia, iron chelate molluscicide treatment prior to lambs grazing the pasture had no demonstrable effect on the prevalence and severity of small lungworm infections, nor the productivity of lambs grazing these pastures. This study indicates that for a commercial sheep farm, additional molluscicide treatments of pastures after they are established, for the prevention of small lungworm infection, may not be warranted. Furthermore, requirements for more precisely monitoring snails are discussed.

Changes over time and changes yet to come

Change over time is of primary interest for ecologists and managers. Change can be positive and is often part of nature's flux, but it can also be negative if arising from impacts that push ecosystems beyond net sustainability. Researchers work long and hard to develop methodologies to gain insight into how much change is part of acceptable flux and how much is unacceptable impact; and monitoring change is also essential to identify levels of recovery over time after restorative management interventions and, in many cases, to fully test hypotheses. This issue's interview with Mike Dodkin, retired naturalist ranger and pest species officer, touches on all these themes as he recollects projects over a 40-year period. Mike was there during the period of social change that saw mineral sand mining on Australia's east coast sites destined for dedication as national parks post-mining. His role not only included finding ways to reduce mining impacts and attain recovery, but also involved starting up new restoration projects to overcome damage that occurred many decades previously – all such projects which will take many decades hence to be fully realized. In a similar vein in this issue, Brad Farmilio and colleagues report about changes in plant composition after 10 years of monitoring in grazed native pastures in south-eastern Australia after an incentive scheme to reduce impacts on grassland remnants; Richard van Dongen and colleagues observe changes in native vegetation on Dirk Hartog Island, Western Australia many years after removal of non-native herbivores; and, Andrew Carter and Laura Ruykys document a gradual eradication of introduced predators in a fenced reserve in South Australia The passage of time is also important to fully test new hypotheses. Hannah Franklin and colleagues in New Zealand tested the capacity of a range of native riparian plants to take up nitrogen and propose a framework for selecting species that can best buffer farm runoff into streams. Longer term study of riparian plantings based on this model will provide valuable insights, as will application of the value-based arguments for seascape repair put forward by Vishnu Prahalad and colleagues in this issue's second feature and Linda Luck and colleagues’ longer term testing of residual herbicides to reduce Gamba Grass populations in northern Australia. Indeed, all our interventions to improve the functionality of impaired ecosystems could be considered tests of hypotheses, including the core hypothesis that interventions can make a positive difference. Ian McLeod and colleagues acted on an informed hunch in North Queensland that relocation of coral colonies displaced by a cyclone would result in recovery, and all the indicators are pointing to success in this case and many others. In this and many cases involving lower-to-establish species or processes, only time and ongoing monitoring will tell. For example, longer time frames have proven to be useful in the detection by Tai White-Tony and colleagues of long-term patterns of establishment of tree species after mine site restoration in the Jarrah Forest in Western Australia – as well as to allow Kimberly McCallum and colleagues to assess the relationship between the configuration of planted species and their effective pollination in South Australian revegetation sites, many years after plant establishment. With the passage of time also comes change in personnel, such that longitudinal studies and ongoing nurturing of long-term recovery require commitments by institutions that persist beyond the working lives of individuals. It is hard to overstate the need for future managers and researchers to recognize the amount of past work that has gone into many studies and into securing the current condition of many sites. We need to firmly but gently remind current and future generations that long-term effort in these areas is a multi-generational compact.

Phosphorus fertiliser management for pastures based on native grasses in south-eastern Australia

Approximately 3.1 Mha (22%) of the agricultural area of south-eastern Australia can be classified as native pasture. There is the assumption that, owing to the widespread occurrence of low-fertility soils in Australia, native grass species do not respond to increased phosphorus (P) fertility. Currently, there are no industry recommendations of target soil-test P values for native-grass-based pastures. This paper reviews the responses of perennial native pasture species endemic to south-eastern Australia to P application in controlled environments, surveys, replicated experiments and paired-paddock trials. Eighty-seven site-years of trial data where different levels of P were applied, conducted over the last two decades, on native-based pastures in south-eastern Australia are reviewed. Data indicate that application of P fertilisers to native grass pastures can increase dry matter (DM) production and maintain pasture stability. However, minimum targets for herbage mass (800 kg DM/ha) and groundcover (80%) are required to ensure persistence of perennial native grasses. Stocking rates also need to match carrying capacity of the pasture. Based on previous research, we recommend target soil-test (Olsen; 0–10 cm) P levels for fertility-tolerant native grass pastures, based on Microlaena stipoides, Rytidosperma caespitosum, R. fulvum, R. richardsonii, R. duttonianum and R. racemosum, of 10–13 mg/kg, whereas for pastures based on fertility-intolerant species such as Themeda triandra, lower levels of &amp;lt;6 mg/kg are required to ensure botanical stability.

Parent material and climate affect soil organic carbon fractions under pastures in south-eastern Australia

In the present field survey, 72 sites were sampled to assess the effect of climate (Monaro, Boorowa and Coleambally regions) and parent material (Monaro region only; basalt and granite) on soil organic carbon (OC) under perennial pastures. In the higher-rainfall zone (Monaro and Boorowa; &gt;500mm mean annual rainfall), OC stocks under introduced and native perennial pastures were compared, whereas in the lower-rainfall zone (Coleambally; &lt;500mm mean annual rainfall) OC stocks under crops and pastures were compared. Carbon fractions included total OC (TOC), particulate OC (POC), resistant OC (ROC) and humic OC (HUM). Higher OC stocks were associated with higher spring and summer rainfall and lower annual temperatures. Within a climatic zone, parent material affected the stock of OC fractions in the 0–30cm soil layer. Within a climatic zone, when grouped by parent material, there was no difference in OC stock with vegetation type. There were significant correlations between soil factors associated with parent material and OC concentration, including negative correlations between SiO2 and HUM (P&lt;0.05) and positive correlations between cation exchange capacity and TOC, POC and ROC (P&lt;0.01). TOC was also positively correlated with total nitrogen (N) and available sulfur (S; P&lt;0.05), indicating organic matter in soil is important for N and S supply for plant production in the studied regions, and vice versa. Although ensuring adequate available S may increase OC stocks in south-eastern Australia, the large stock of OC in the soil under perennial pastures, and the dominating effect of climate and parent material on this stock, may mean that modest increases in soil OC due to management factors go undetected.

Biology and management of the redheaded pasture cockchaferAdoryphorus couloni(Burmeister) (Scarabaeidae: Dynastinae) in Australia: a review of current knowledge

The redheaded pasture cockchafer, Adoryphorus couloni (Burmeister) (Scarabaeidae: Dynastinae: Pentodontini) is a pest of semi-improved and improved pastures in south-eastern Australia. It is a native species that has adapted to managed pastures, and despite many years of research in attempts to control it, this species still causes major economic damage, especially to perennial dairy pastures in south-eastern Australia. This is a review of available information on A. couloni and identifies some basic information gaps that require addressing: correct identification of the main pasture beetles, more accurate detection and monitoring methods, and better information on its biology and ecology, especially its feeding behaviour in soil.

Effect of warming on the productivity of perennial ryegrass and kikuyu pastures in south-eastern Australia

Grazed pastures in south-eastern Australia are typically based on temperate (C3) species, such as perennial ryegrass (Lolium perenne). With predictions of warming to occur in this region, there has been growing interest in the performance of more heat-tolerant and deep-rooted subtropical (C4) pasture grasses, such as kikuyu (Pennisetum clandestinum). This study used an existing pasture model to estimate the production of kikuyu compared with the commonly used perennial ryegrass at seven sites in south-eastern Australia, using an historical baseline climate scenario between 1971 and 2010, and the daily temperature of the baseline scenario adjusted by +1, +2, and +3°C to represent potential warming in the future. The seven sites were chosen to represent the range of climatic zones and soil types in the region. First, the model predictions of monthly kikuyu dry matter (DM) production were validated with measured data at Taree, Camden, and Bega, with results showing good agreement. Second, pasture production (t DM/ha), metabolisable energy (ME, MJ/kg DM) content, and ME yield (GJ/ha) were predicted using the baseline and warmer climate scenarios. The study was based on 56 simulations of the factorial arrangement of seven sites × four temperature scenarios × two pastures. The month and annual ME yield of a kikuyu–subterranean clover (Trifolium subterraneum) pasture and a perennial ryegrass–subterranean clover pasture were compared. This study showed that in summer-dominant rainfall locations, where the average maximum temperature is &gt;23°C, kikuyu was a more productive pasture species than perennial ryegrass. In winter-dominant rainfall locations during the warmer months of December–March, kikuyu can provide a useful source of ME when perennial ryegrass is less productive. With warming of up to 3°C at the winter-dominant rainfall sites, the average ME yield per year of kikuyu was predicted to surpass that of perennial ryegrass, but inter-annual variation in kikuyu production was higher. The nutritive value, seasonal distribution of growth, total annual production, and its variability are all important considerations for producers when selecting pasture species.

Assessment of management options for Chilean needle grass in sheep-grazing systems

Chilean needle grass [Nassella neesiana (Trin. & Rupr.) Barkworth; CNG] is a perennial spear grass that has invaded pastures in south-eastern Australia and can lead to a substantial reduction of stockcarrying capacity during the summer months. This study examined a range of grazing, herbicide and pasture resowing options, alone or in combination, on CNG and introduced pasture grass basal cover, for several CNG-infested sites in south-eastern Australia. At each site, options were chosen on the basis that they were most likely to control the CNG infestation while maintaining a productive sheep-grazing enterprise on grass pastures. After 2 years of management, the reduction in CNG basal cover in set stock plots that were sprayed with flupropanate, versus those not sprayed, ranged from non-detectable to a reduction of 80%, depending on site location. After 5 years of management, the reduction ranged from zero to 50%. Grazing management or sowing of competitive pastures did not generally reduce CNG basal cover to low levels. None of the management options maintained reasonable levels of desirable perennial species by the end of 4–5 years. We conclude that, because of the persistence of CNG, the need for regular spraying of herbicide, and the relative ineffectiveness of other control methods, management systems may need to be developed that utilize CNG while minimizing its input to the soil seedbank.

Nitrogen from Australian dryland pastures

Legume-based pastures, particularly those containing a large proportion of lucerne (alfalfa, Medicago sativa), have a prodigious capacity to fix atmospheric N2. Budgets of N show that permanent pastures in south-eastern Australia, when growing with no management limitations, can supply more N than is removed in animal products and can eventually lead to excess soil N. For a mixed crop–livestock farm, legume-dominant ley pastures occupying ~40% of the land area can maintain a stable N balance. The actual performance of pastures on farms normally falls below the potential. Pastures are being replaced by crops in the wheat-sheep zone and, to a lesser extent, in the high-rainfall zone. Pasture productivity, as indicated by the area topdressed, the mean stocking rate, input of superphosphate and sale of pasture legume seed has decreased in the period 1990–2010. It is therefore likely that N2 fixation by pastures is falling sharply in the wheat–sheep zone and is static or falling slightly in the high-rainfall zone. Reversing the decrease in N2 fixation by pastures will become important if the real price of N fertilisers increases, as seems likely because the efficiency of fertiliser synthesis is approaching a maximum and the reserves of natural gas feedstock will eventually be depleted. Increased N2 fixation by pastures will depend on more profitable grazing industries, improved management methods and genotypes, and re-adoption of ley pastures by farmers. There is evidence that profitability of grazing enterprises is approaching that of crops so investment in pasture science is likely to lead to increased N2 fixation.

Landscape and local influences on patterns of reptile occurrence in grazed temperate woodlands of southern Australia

The woodlands of temperate south-eastern Australia are characterised by extensive historical clearing and ongoing modification of the understorey habitat through livestock grazing, fertilization and cropping. The reptile assemblage of these temperate woodlands, while relatively speciose, is believed to be in decline. We report on the abundance and diversity of terrestrial reptiles in native pastures in south-eastern Australia in relation to landscape and local factors; in particular, latitude and grazing management and tree retention. Reptiles were sampled on 24 paired farms spread widely over the south-western slopes of south-eastern Australia. Each pair comprised one farm under rotational grazing and a neighbouring farm with continuous grazing. Twenty-one species were detected, dominated numerically by several skinks and a pygopodid, with clear disparities in the biogeographic distribution of reptiles and also variation owing to survey technique, location, grazing regime, and the presence of trees. Multivariate models showed that the distribution of reptiles is influenced by factors operating at several levels and, to a lesser extent, by farm management. Reptile occurrence was regularly explained by correlations with site-level structural heterogeneity (e.g. native plant richness, number of large trees and log cover) as well as showing strong underlying latitudinal variation. The presence of woodland is critical to reptile occurrence in grazed (and fragmented) landscapes. If the reptile assemblage of this agroecosystem is to benefit from altered farm management, then different management and policy responses may be required, depending on the levels of habitat structural complexity and agricultural intensification that already exist.

Increasing amounts of crushed wheat fed with pasture hay reduced dietary fiber digestibility in lactating dairy cows

Sixteen cows in mid-lactation (milk yield of 23.8±2.3 kg/d) were individually fed diets consisting of chopped perennial ryegrass hay, offered at 3kg of dry matter (DM)/100kg of body weight (BW), fed either alone or supplemented with amounts of crushed wheat ranging from 0.4 to 1.6kg of DM/100kg of BW (increasing at nominal intervals of 0.4kg of DM/100kg of BW; 5 nominal treatments in total). Three cows were allocated to each treatment except the mid-range wheat treatment, which had 4 cows. Results were analyzed by regression because the intake of the wheat by cows within treatments varied. The hay was used to reflect the characteristics of summer pastures in southeastern Australia. Feed intake and fecal output were measured to determine digestion coefficients, feeds were incubated in nylon bags in the rumen, and rumen variables were monitored. Estimates of metabolizable energy (ME) of the hay from in vivo or in vitro digestibility were also compared. The digestibility of neutral detergent fiber (NDF) was depressed linearly as the amount of crushed wheat consumed increased to 36% of DM intake. The extent to which negative associative effects on NDF digestion were associated with the hay could not be determined, as it was not possible to distinguish between the NDF from hay and that from wheat. However, acid detergent fiber (ADF) digestion also declined, suggesting that most of the response lay with the hay because ADF was negligible in the wheat. Most data indicated that effects of proportion of wheat in the diet on the utilization of consumed nutrients were small. Despite substitution of wheat for hay reducing the forage intake of cows, there was a positive linear effect on marginal milk responses (1.3kg of energy-corrected milk/kg of DM wheat). Mean rumen fluid pH declined as the proportion of wheat in the diet increased. The lowest pH for any individual cow during a 24-h period was 5.4, and the amount of time that rumen fluid pH was <6.0 ranged from 0 to 14h depending on the amount of wheat consumed. It was concluded that these perturbations of the rumen environment were probably sufficient to result in negative associative effects. In addition, estimates of the ME content of the hay were higher when calculated from in vitro compared with in vivo digestibility, which has implications when estimating the amount of feed required for production.

Nitrogen balances in temperate perennial grass and clover dairy pastures in south-eastern Australia

Nitrogen (N) fertiliser use on dairy pastures in south-eastern Australia has increased exponentially over the past 15 years. Concurrently, imports of supplementary feed onto dairy farms have increased, adding further nutrients to the system. These trends raise questions about the environmental effects of higher nutrient inputs to dairy farms. To gauge possible effects, annual N balances were calculated from an experiment where N inputs and losses were measured for 3 years from non-irrigated grass/clover pastures receiving either no N fertiliser (Control) or 200 kg N/ha applied annually as ammonium nitrate or urea. Estimated total N inputs, averaged over the 3 years, were 154, 314, and 321 kg N/ha.year for the control, ammonium nitrate, and urea treatments, respectively, while N outputs in meat and milk were 75, 99, and 103 kg N/ha.year, respectively. The corresponding calculated N surplus was 79, 215, and 218 kg N/ha.year for the 3 treatments, respectively, and the ratio of product N/total-N inputs for the 3 treatments ranged from 50% in the control to 32% for both N treatments. Total N losses averaged 56, 102, and 119 kg N/ha.year, leaving a positive N balance of 23, 112, and 99 kg N/ha.year for the control, ammonium nitrate, and urea treatments, respectively. The ratio of product N/total-N inputs or the N surplus may be useful in monitoring the efficiency of conversion of N into animal products and the potential environmental effect at a whole-farm scale. However, additional decision support or modelling tools are required to provide information on specific N losses for a given set of conditions and management inputs. Given the large range in N losses there is opportunity for improving N-use efficiency in dairy pastures through a range of management practices and more tactical use of grain and N fertiliser.

A comparison of some surface soil phosphorus tests that could be used to assess P export potential

Phosphorus (P) exports from agricultural land are a problem world-wide and soil tests are often used to identify high risk areas. A recent study investigated changes in soil (0–20 mm), soil water and overland flow in 4 recently laser-graded (&lt;1 year) and 4 established (laser-graded &gt;10 years) irrigated pastures in south-eastern Australia before and after 3 years of irrigated dairy production. We use the results from that study to briefly examine the relationships between a series of ‘agronomic’ (Olsen P, Colwell P), environmental (water-extractable P, calcium chloride extractable P, P sorption saturation, and P sorption), and other (total P, organic P) soil P tests. Of the 2 ‘agronomic’ soil P tests, Colwell P explained 91% of the variation in Olsen P, and Colwell P was better correlated with the other soil tests. With the exception of P sorption, all soil P tests explained 57% or more of the total variation in Colwell P, while they explained 61% or less of Olsen P possibly due to the importance of organic P in this soil. Variations in total P were best explained by the organic P (85%), Calcium chloride extractable P (83%), water-extractable P (78%), and P sorption saturation (76%). None of the tests adequately predicted the variation in P sorption at 5 mg P/L equilibrating solution concentration. The results of this limited study highlight the variability between soil P tests that may be used to estimate P loss potential. Moreover, these results suggest that empirical relationships between specific soil P tests and P export potential will have limited resolution where different soil tests are used, as the errors in the relationship between soil test P and P loss potential are compounded by between test variation. We conclude that broader study is needed to determine the relationships between soil P tests for Australian soils, and based on that study a standard protocol for assessing the potential for P loss should be developed.

The effect of fertiliser and grazing on nitrogen export in surface runoff from rain-fed and irrigated pastures in south-eastern Australia

Nutrients, including nitrogen (N), exported from agricultural systems contribute to eutrophication and the development of algal blooms. Understanding the relative effect of farm management on nutrient export will indicate the extent to which farmers can potentially mitigate this process. Six years of monitoring surface runoff from rain-fed and irrigated dairy pastures was carried out in south-eastern Australia. Over the monitoring period, the flow-weighted mean annual total N (TN) concentrations in runoff varied between 8.2 and 29 mg/l for rain-fed pasture and 8.7 and 58 mg/l for irrigated pasture. An additive component model describing N concentrations separated the management (grazing and fertiliser) and year effects from other processes. The model accounted for 40 and 47% of the variation in N concentrations for the rain-fed and irrigated pastures, respectively. While fertiliser application, grazing and year had a significant effect on concentrations, other variables that are not necessarily under management control significantly affected N export. With current knowledge, improved management of pasture-based systems such as improved timing of fertiliser application and grazing relative to runoff may only result in a small decrease in N export. The remainder of the variability was attributed to environmentally mediated changes of N concentrations in runoff water. The collection of more detailed information on environmental parameters including soil moisture and soil temperature is proposed, to enable a better prediction of N concentrations and therefore improved understanding of potential management strategies.

Excess cation concentrations in shoots and roots of pasture species of importance in south-eastern Australia

Excess cation concentrations (total cations – total inorganic anions) are reported for roots and shoots of 16 plant species of importance in pastures in south-eastern Australia. This information is required for the calculation of acidification in grazed pasture systems. The excess cation concentrations for shoots at flowering were [cmol(+)/kg]: perennial grasses — Lolium perenne (perennial ryegrass) 50, Phalaris aquatic (phalaris) 51, Danthonia richardsonii (wallaby grass) 30, Dactylus glomerata (cocksfoot) 62, Holcus lanatus (Fog grass) 60; annual grasses — Lolium rigidum 29, Vulpia bromoides (vulpia) 40, Hordeum leporinum (barley grass) 46, Bromus mollis (soft brome) 59; perennial legumes — Medicago sativa (lucerne) 115, Trifolium repens (white clover) 147; annual legumes — Trifolium subterraneum (subterranean clover) 142, Medicago truncatula (barrel medic) 114, Ornithopus sativus (serradella) 137; weeds — Arctotheca calendula (cape weed) 165, Echium plantagineum (Paterson’s curse) 169. Values for roots were in the same order as shoots in vulpia and wallaby grass but lower for the other species, varying between 26 and 62% of the shoot value in grasses and 29 and 49% in legumes. For a subset of 4 legumes and 3 grasses, the excess cation concentrations in shoots were measured over the main production period in spring. Excess cation concentrations generally declined during the season, with the change being relatively larger in grasses than legumes.

Gaseous nitrogen loss from temperate perennial grass and clover dairy pastures in south-eastern Australia

The use of nitrogen (N) fertiliser on dairy pastures in south-eastern Australia has increased exponentially over the past 15 years. Concerns have been raised about the economic and environmental impact of N loss through volatilisation and denitrification. Emissions of NH3, N2, and N2O were measured for 3 years in the 4 different seasons from a grazed grass/clover pasture, with or without 200 kg N fertiliser/ha, applied as ammonium nitrate and urea.Nitrogen-fertilised treatments lost significantly more N than the control treatments in all cases. More NH3 was lost from urea-fertilised treatments than from either the control or ammonium nitrate treatments, whereas ammonium nitrate treatments lost significantly more N through denitrification than the control or urea treatments in all seasons, except for summer. More NH3 was lost in summer than in the other seasons, whereas denitrification and N2O losses were highest in winter and lowest in summer. The total annual NH3 loss from the control, ammonium nitrate, and urea treatments averaged 17, 32, and 57 kg N/ha.year, respectively. Annual denitrification losses were estimated at around 6, 15, and 13 kg N/ha.year for the control, ammonium nitrate, and urea treatments, respectively. Total gaseous N losses were estimated to be 23, 47, and 70 kg N/ha.year from the control, ammonium nitrate, and urea treatments respectively.Although the use of ammonium nitrate fertiliser would significantly reduce NH3 volatilisation losses in summer, this fertiliser costs 45% more per unit N than urea, so there is no economic justification for recommending its use over urea for the other seasons. However, the use of urea during the cooler, wetter months may result in significantly less denitrification loss. The results are discussed in terms of potential management strategies to improve fertiliser efficiency and reduce adverse effects on the environment.

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

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.

A laboratory study of phosphorus mobilisation from commercial fertilisers

Phosphorus (P) exported from pastures following fertiliser application contributes to the nutrients and associated problems in the streams and rivers of south-eastern Australia. This laboratory study examined whether attributes of P fertilisers may affect P exports soon after their application to field soils; 3 commercial fertilisers [diammonium phosphate (DAP), single superphosphate (SSP), and sulfur-coated single superphosphate (CSSP)] were applied to 2 repacked soils (Arawata and Ellinbank) at 5 moisture contents.Soil type was the most important factor affecting water-extractable P (expressed as a percentage of the P added as fertiliser), accounting for 30% of the total variation. The majority of this variation is explained by the water-extractable P concentrations in the Arawata low moisture treatments. These treatments [7, 6, and 6% soil moisture when equilibrated at 99, 95, and 86.5% relative humidity (RH), respectively] contained water-extractable P concentrations c. 3 times higher than the high moisture (c. 20 and 25% soil moisture) or the Ellinbank treatments. This result probably reflects differences in soil properties including the extent of water repellency and P adsorption.Fertiliser type explained only 6.9% (P &lt; 0.001) of the total variation in water-extractable P, partially as a result of the 86.5% RH (a low moisture) Arawata treatment. In this Arawata low moisture treatment, the mean extractable P was similar for both DAP and SSP, 13.1% [least significant interval (l.s.i.) 16.7–10.3] and 11.3% (l.s.i. 14.3–8.9), respectively, but for SSP, water-extractable P increased over time unlike any other treatment. Water-extractable P from DAP was approximately double that from SSP for the Ellinbank and high moisture treatments. The higher water-extractable P following DAP application is explained in terms of its chemical properties and reaction products. Sulfur coating the SSP granules (CSSP) increased water-extractable P, as did higher soil moisture.This study suggests that under conditions present in most pastures in south-eastern Australia and depending on soil hydrology, water-extractable P and P export from fertilisers may increase in the order DAP &gt; CSSP &gt; SSP if overland flow occurs soon after their application.