Crop and Pasture Science
Volume 65 Number 8 2014
Perennial Grasses in Pasture Production Systems
CP13284Perennial pasture grasses—an historical review of their introduction, use and development for southern Australia
Species such as perennial ryegrass and phalaris are vital contributors to the competitive productivity of Australia’s livestock industries, underpinning an estimated 9 M ha of high carrying-capacity pasture. Their adoption, in conjunction with inoculated clover, rose steadily in Australian systems, designed with an appreciation of the marginal environment, and stimulated by advances in agronomic practice. Early forecasts for the area of improved pasture have not yet been realised. The history of influential collaborations, plant breeding, evaluation and adoption of perennial grasses, reveals opportunities for improving the direction of research and significantly expanding livestock industries in the high rainfall zone of temperate Australia.
Determining the most profitable life of pastures involves technical and economic considerations, with pasture persistence meaning profitable persistence. To maximize profit over time, pastures should be renewed when the profit from one further year is less than the average annual profit of a replacement cycle of the pasture. The challenge for management and plant breeding is to have pastures producing near peak production for longer as this is the key to profitable persistence.
The quality of pastures for animals can be described in terms of feeding value (FV) which is a combination of feed nutritive value (NV) and voluntary intake. There are numerous, complex interactions between plant physiology and pasture FV and NV. This review focuses on these interactions in four key areas (plant growth strategies, phenological development, pasture regrowth, and response to environmental stress), extracting key principles and illustrating how plant breeding or management may be used to manipulate such interactions to improve FV.
CP13453Quantifying the interactions between grazing interval, grazing intensity, and nitrogen on the yield and growth rate of dryland and irrigated perennial ryegrass
Grazing management is a key drive of dairy business success. Conjecture exits regarding the agreed grazing principles and this study explores the interaction between grazing management, nitrogen and irrigation inputs on the production of perennial ryegrass. This study concluded that grazing of perennial ryegrass should always occur between the second and third leaf regrowth stage, with the interval closer to the third leaf stage during periods of low growth rate and closer to second leaf during periods of high growth.
CP13383Agronomic advantages conferred by endophyte infection of perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.) in Australia
Perennial ryegrass and tall fescue are key grasses of sown pastures in the high-rainfall zone of south-eastern Australia. They may be infected by microscopic Neotyphodium endophytic fungi which are an essential component of the agronomic performance of these grasses in long-lived pastures. The best outcomes for Australian farmers will be achieved through a combination of elite selected endophytes and elite plant genetics adapted to each region, so that perennial ryegrass endophyte toxicosis is eliminated or greatly reduced, and the endophyte-enhancing effects on grass performance are captured.
CP13408Use of modelling to identify perennial ryegrass plant traits for future warmer and drier climates
Perennial ryegrass pasture production is likely to be negatively impacted by projected warmer and drier climates across southern Australia, but the capacity to select plants better adapted to these conditions has not been explored. A modelling approach was used to assess the production benefits of selecting for deeper roots, increased heat tolerance and greater growth responses under elevated carbon dioxide concentrations. Results indicated that all three traits have potential to increase pasture production in future climates, but that the most effective traits differed across regions.
Microlaena stipoides, a Australian native perennial grass, is common within 3 million ha of grazed pastures in south eastern Australia. This paper reports the results of studies into the key attributes of the population dynamics of this species in grazed pastures. The research demonstrates that persistence of Microlaena is due to a combination of perennation of adult plants and seedling recruitment. The latter being a rare event, due to seed predation.
The molecular phylogeny of the genus Dactylis provides a clear evolutionary history of the diploids from which modern tetraploid germplasm and cultivars have evolved. This will allow breeders to systematically use a wider range of both diploid and tetraploid germplasm for improvement of cocksfoot. Germplasm of many diploid and tetraploid forms are poorly represented in genebanks and require urgent collection, as many are under serious threat from habitat degradation and climate change.
Non-edible feeds like grass-based pastures can be converted efficiently into high quality edible food like milk. ‘Kikuyu’ is a very productive subtropical grass with enormous potential to convert non-edible fibre into milk; yet quality aspects and utilisation losses, mainly due to inadequate input and grazing management, impair its use. This review attempts to identify the main losses in utilization of kikuyu-based pastures and proposes management approaches that can overcome its main limitations and result in substantial increases in milk production from kikuyu-based pastures.
CP13424Production and persistence of subtropical grasses in environments with Mediterranean climates
Growing subtropical perennial grasses in regions with Mediterranean climates may both increase production and have multiple environmental benefits. This paper addresses the shortage of information on the persistence of different species and their expected seasonal production and feed quality in these environments. The results suggest there is considerable potential for growing subtropical perennial grasses in many regions with a Mediterranean environment.
CP13449Spatial variability in pH and key soil nutrients: is this an opportunity to increase fertiliser and lime-use efficiency in grazing systems?
Fertiliser-use efficiency is a key issue for grazing systems in Australia. This study found considerable spatial variability in soil pH, P, K and S at the sub-paddock scale which may affect the efficiency of utilisation of lime and fertiliser. The results suggest that site specific management of fertiliser and soil ameliorants could provide substantial improvements in pasture productivity as well as reductions in the total amounts applied.
Pasture grasses typically employ 3 strategies to survive periods of severe drought, dehydration avoidance, dehydration tolerance and summer dormancy. Deep rooting is the best example of dehydration avoidance while the ability of some grasses to become dormant over summer is also well known. Less is known about dehydration tolerance, allowing plants to tolerate low tissue water content. This work compared varieties of cocksfoot, tall fescue and phalaris for the trait. The highest levels of dehydration tolerance occurred in cocksfoot varieties of semi-arid origin with a similar observation made in tall fescue. Little dehydration tolerance was seen across the phalaris varieties. This is a powerful drought-survival trait, warranting increasing attention in plant breeding programs.