Assessing Resilience of Pasture Production to Climatic Changes

Increasing temperatures and atmospheric carbon dioxide (CO2) concentrations, together with changes to rainfall patterns, will influence seasonal pasture production; however climate change projections for south eastern Australia are uncertain (CSIRO and BoM 2007). Despite this, climate change impact assessments generally rely on specific climate projections, but in this study an alternative approach was developed to test the resilience of production to incremental changes in climate

Early Sowing and Irrigating of Rape Crops in Cool Temperate Environments Boosts Forage Yield Potential

Forage rape is commonly grown on Tasmanian dairy farms to provide feed during periods of low pasture growth and/or low nutritive value. In these regions, forage crops are generally sown between early spring and late autumn and are commonly rainfed, though farmers may apply a single irrigation at sowing. While the effect of water availability on forage yield has been well characterised for regions in north-western Tasmania (Neilsen 2005), there is a dearth of information for other regions in Tasmania. Hence, the objectives of this study were to identify optimal sowing times for, and determine the extent to which a single irrigation at sowing influences productivity of, rainfed brassica crops across the dairy regions of Tasmania

Impact of Grazing on the Silage Yield of Forage Oat Crops

Winter forage oat crops are increasing in acreage on Tasmanian dairy farms. Such crops can be grazed multiple times during vegetative development in winter then later harvested for silage at the booting or soft dough growth stages in spring. Although effects of grazing on grain yield of winter cereal crops have been well characterised (Harrison et al. 2011), little research has been conducted on the influence of grazing on the forage and silage yield potential of oats grown in Tasmania. We aimed to explore the influence of grazing management on the yields of forage for grazing and ensiling of oat crops using a biophysical crop model

Modelling Adaptation and Mitigation Strategies for Southern Livestock Industries of Australia

Climate change will impact on the Australian grazing industries both through mitigation policies and the impact of warmer temperatures, increased atmospheric CO2 and changed rainfall patterns (Cullen et al. 2009; Eckard et al. 2010). Mechanistic models are useful tools to inform our understanding of the complex interactions between future climates and the soil, plant, animal and management in livestock production systems. This paper summarises the results of a number of whole farm systems modelling studies investigating likely impacts of climate change, adaptation options and emissions implications for livestock production in southern Australia

Effect of Nitrogen Fertiliser Applications on Botanical Composition

The diminishing returns associated with nitrogen (N) fertiliser use over time are well recognised, as are the detrimental effect to the environment of excess N fertiliser use (Eckard 1998). However, many Tasmanian dairy farmers apply continually high rates of N fertiliser (e.g. in excess of 500 kg/ha annually) to minimise risk associated with variable pasture dry matter (DM) yields, and this often occurs at the expense of white clover populations within the pasture (Frame 1990; Frame et al. 1998). The responses of botanical composition and perennial ryegrass DM yields to N fertiliser application rate were investigated in the current field plot study, to provide further information for farmers about the production-related effects of their N use

Inter-Annual Variability in Pasture Herbage Accumulation in Temperate Dairy Regions: Causes, Consequences, and Management Tools

Inter-annual variation in pasture herbage accumulation rate (HAR) is common in temperate dairy regions, posing challenges for farmers in the management of dairy cow feeding and of pasture state. This paper reviews the biophysical factors that cause inter-annual variation, considers some of its consequences for the efficient harvest of pasture, and discusses the basis for decision rules and support tools that are available to assist New Zealand and Australian farmers to help manage the consequences of an imbalance between feed supply and demand. These tools are well-grounded in scientific research and farmer experience, but are not widely used in the Australasian dairy industries. Some of the reasons for this are discussed. Inter-annual variability in HAR cannot be removed, even with inputs such as irrigation, but reliable forecasts of pasture HAR for a month or more could greatly improve the effectiveness of operational and tactical decision-making. Various approaches to pasture forecasting, based on pasture growth simulation models, are presented and discussed. Some of these appear to have reasonable predictive ability. However, considerably more development work is needed to: (1) prove their effectiveness; and (2) build the systems required to capture real-time, on farm data for critical systems variables such as pasture herbage mass and soil water content to combine with daily weather data. This technology presents an opportunity for farmers to gain greater control over variability in pasture-based dairy systems and improve the efficiency of resource use for profit and environmental outcomes

Effect of Defoliation Management on Expression of the ‘High Sugar’ Cultivar Trait in Tasmania

The proposed benefits of perennial ryegrass (Lolium perenne L.) cultivars with a high concentration of water soluble carbohydrates (WSC) for the dairy industry in Australia include enhanced rumen protein metabolism, and potential improvements in milk components (Stewart et al. 2009). Perennial ryegrass cultivars have been developed to express higher levels of WSC, and extensive trials have shown consistent trait expression in Europe (reviewed by Edwards et al. 2007a). In New Zealand and Australia, there has been less consistent expression of the high sugar trait (Smith et al. 1998; Parsons et al. 2004; Francis et al. 2006), possibly reflecting a genotype by environmental interaction (Parsons et al. 2007). The current study was developed to investigate whether the high sugar trait of cultivars Aber-Magic (developed in Aberystwyth) and SF Joule AR1 (developed in Australia), is consistently expressed in cool temperate Tasmania, Australia, and to quantify the effect of contrasting defoliation management on trait expression. It is also important to confirm that any elevation in WSC concentration does not occur at the expense of dry matter (DM) yield, and to consider the relationship between WSC and crude protein (CP) concentrations - thought to be an important contributor to more efficient nitrogen (N) partitioning (Edwards et al. 2007b)

Contrasting soil microbial abundance and diversity on and between pasture drill rows in the third growing season after sowing

Changed spatial configurations at sowing have been investigated as a strategy to minimize interspecific competition and improve the establishment and persistence of multi-species plantings in pastures, but the impact of this practice on the soil microbiome has received almost no previous research attention. Differences in populations of bacteria and fungi in the surface 10 cm of soil in the third year following pasture establishment were quantified using quantitative polymerase chain reaction and terminal restriction fragment length polymorphism methods. Populations were compared on, and between, drill rows sown to either the perennial grass phalaris (Phalaris aquatica L.), perennial legume lucerne (alfalfa; Medicago sativa L.) or the annual legume subterranean clover (Trifolium subterraneum L.). Results showed that soil microbial abundance and diversity were related to plant distribution across the field at the time of sampling and to soil chemical parameters including total carbon (C), mineral nitrogen (N), pH, and available phosphorus (P), potassium (K) and sulfur (S). Despite the 27-month lag since sowing, pasture species remained concentrated around the original drill row with very little colonization of the inter-row area. The abundance and diversity of bacterial and fungal populations were consistently greater under drill rows associated with higher total C concentrations in the surface soil compared with the inter-row areas. Our results showed that the pH and available nutrients were similar between the subterranean clover drill row and the inter-row, suggesting that soil microbial populations were not impacted directly by these soil fertility parameters, but rather were related to the presence or absence of plants. The abundance of bacteria and fungi were numerically lower under phalaris rows compared to rows sown to legumes. The richness and diversity of fungal populations were lowest between rows where lucerne was planted. Possible explanations for this observation include a lower C:N ratio of lucerne roots and/or a lack of fibrous roots at the soil surface compared to the other species, illustrating the influence of contrasting plant types on the soil microflora community. This study highlights the enduring legacy of the drill row on the spatial distribution of plants well into the pasture phase of a cropping rotation and discusses the opportunity to enhance the microbiome of cropping soils on a large scale during the pasture phase by increasing plant distribution across the landscape