Guest Editors:
Brendan R. Cullen, Mark R. Norton, and Kevin F. M. Reed
Crop and Pasture Science
Volume 72 Numbers 8 & 9 2021
Special IssuePastures for the Future
Exotic pasture seeds intentionally introduced into Australia by plant collectors have underpinned pasture improvement in many livestock grazing systems. A vast quantity and diversity of unique grasses, legumes, herbs and forbs from tropical and temperate climates and from many collections has now been centralised at the Australian Pastures Genebank. Maintaining this collection is imperative to meeting the challenges of future climates and farming systems. This paper reviews the collectors, collection missions, subsequent key cultivar development and future challenges.
In Western Australia, there has been a concerted effort to develop new perennial pasture options. Research, development, and extension have covered a range of herbaceous perennial legumes, leguminous and native shrubs, herbs and temperate and warm season grasses. Overall, this search has proved to be a considerable challenge in a Mediterranean environment with many promising species having little or no commercial impact, and only a small number of species have had widespread commercial adoption. This review explores the key requirements for perennial species to become more than a niche pasture in a Mediterranean climate.
Burr medics (Medicago polymorpha) are widely grown annual pasture legumes in southern Australia, but all cultivars are susceptible to high levels of boron in subsoils. We report on boron tolerance of several accessions, demonstrate boron tolerance is inherited in a 3 : 1 ratio and present a molecular marker for boron tolerance. This will allow for the efficient introgression of boron tolerance into widely adapted genetic backgrounds.
Messina is the only annual pasture legume persistent on saline waterlogged soil, and new cultivars superior to the current cultivar (Neptune) in terms of mechanisms of tolerance and avoidance of seasonal salinity at germination could improve saltland pasture profitability. These traits were compared among messina accessions for the first time and found to vary, with some accessions showing higher tolerance and avoidance than Neptune, demonstrating potential to select for improved persistence on saline soils prone to waterlogging in southern Australian and other regions of the world with Mediterranean-type climates.
CP20427 Abstract | CP20427 Full Text | CP20427PDF (339 KB) Open Access Article
Effectiveness and the consequence of cross–host compatibility of commercial rhizobial strains in forming root nodules with pasture legumes for N2 fixation is poorly understood. We screened current commercial rhizobial strains for their capacity to form effective nodules on pasture legume hosts and found that some rhizobial strains formed root nodules on multiple species and/or cultivars of legumes, whereas certain strains were more effective at increasing shoot biomass. The data can be used to guide rhizobial inoculant selection where multiple pasture legume species are sown in a mixture.
Increases in temperature, along with possible decreases in rainfall, will influence the production of forage on Australian dairy farms. A simulation study investigated how forage-cropping systems and pasture systems will respond to potential future climates. Overall, forage-cropping and irrigated-pasture systems appear resilient to projected changes in climate as long as there is a reliable supply of irrigation water.
The effects of restricted irrigation and summer grazing were examined in plots of perennial and short-lived ryegrass cultivars at two district sites in northern Victoria, Australia. Responses varied across sites, seasons and cultures. Perennial ryegrasses performed better than short-lived ryegrasses, but dry matter production was low and plant frequency was a better indicator of plant resilience to these conditions.
Tropical perennial grasses are an important forage option in the frost prone, summer dominant rainfall zone in eastern Australia, but their production potential is not realised owing to lack of nitrogen fertility. We evaluated a range of tropical and temperate perennial legume species in mixes with digit grass in the northern inland region of New South Wales over 4 years with below average rainfall. Under these conditions, lucerne and Desmanthus virgatus were the most productive and persistent species.
This study examined whether separating species in drill rows at sowing improved lucerne survival over a short pasture phase compared with multiple species being sown in the same row. Persistence was reduced only where lucerne was confined to every third drill row, indicating the effect of intraspecific competition on lucerne density; furthermore, interspecific competition from cover crops in the first year consistently reduced lucerne density. The study highlights the importance of narrower rather than wider row spacings in drier environments where pastures remained concentrated around the drill row, and shows that winter-active forage species are important for improving productivity of lucerne-based swards.
White clover and lucerne are among the most important perennial forage legumes in agriculture. White clover has a reputation for sensitivity to drought whereas lucerne is considered quite drought tolerant, although this tolerance is primarily conferred by its deep roots. This experiment, the first reported for these two species in which the deep rooting of lucerne was constrained, compared their dehydration tolerance.
An Australia-wide collaboration (Better Fertiliser Decisions for Pastures, BFDP) previously estimated critical soil test phosphorus (P) values for pastures based on a collation of data from historical fertiliser trials. Soil test critical values are essential to planning fertiliser applications and minimising environmental impacts off-site. We describe early results from trials aimed at validating critical soil test P values from BFDP, using contemporary pasture swards, in order to improve the quality of, confidence in, and uptake of evidence-based P fertiliser advice.
CP20236 Abstract | CP20236 Full Text | CP20236PDF (566 KB) Open Access Article
The extensive grazing systems of northern Australia are dominated by C4 grasses due to the relatively poor persistence of tropical legumes. This occurrence may be associated with the phosphorus-responsive soils of northern Australia, yet the critical phosphorus requirements of many tropical pasture legumes have not been determined. Nine Desmanthus spp. genotypes were grown to determine differences in phosphorus efficiency. There were varietal differences in shoot yield that indicated that phosphorus-efficient genotypes of Desmanthus spp. can be identified for improved pasture performance under phosphorus-limiting conditions.
Messina is a new annual pasture legume with better combined waterlogging and salt tolerance than other annual legumes, but the symbiosis is sensitive to soil acidity. At the pH level recommended as the lower limit for growing messina (pHCa 5.5), nodule number was constrained in both hydroponics and soil; however, the application of fine lime to seed consistently improved nodulation in acidic soils. The risk of suboptimal nodulation would be reduced if the recommended lower soil pH limit for growing messina is increased to pHCa 5.8.
Ground pearls are important pests of a broad range of plants predominantly belonging to the grass family (Poaceae). In eastern Australia, they cause significant damage on sugarcane and turf grasses, and have recently been found in pasture situations in Queensland, but their impacts are unknown. This work reviews Australian and international literature on the biology and management of ground pearls, finding that relatively little research has been undertaken and several knowledge gaps remain.