• Authors:
    • Baldock, J.
    • Unkovich, M.
    • Marvanek, S.
  • Source: Crop & Pasture Science
  • Volume: 60
  • Issue: 7
  • Year: 2009
  • Summary: Dryland agriculture is both a potential source and potential sink for CO 2 and other greenhouse gases. Many carbon accounting systems apply simple emissions factors to production units to estimate greenhouse gas (GHG) fluxes. However, in Australia, substantial variation in climate, soils, and management across >20 Mha of field crop sowings and >30 Mha of sown pastures in the intensive land use zone, provides substantial challenges for a national carbon accounting system, and simple emission factors are unlikely to apply across the region. In Australia a model framework has been developed that requires estimates of crop dry matter production and harvested yield as the first step to obtain carbon (residue) inputs. We use Australian Bureau of Statistics data to identify which crops would need to be included in such a carbon accounting system. Wheat, barley, lupin, and canola accounted for >80% of field crop sowings in Australia in 2006, and a total of 22 crops account for >99% of the sowing area in all States. In some States, only four or six crops can account for 99% of the cropping area. We provide a ranking of these crops for Australia and for each Australian State as a focus for the establishment of a comprehensive carbon accounting framework. Horticultural crops, although diverse, are less important in terms of total area and thus C balances for generic viticulture, vegetables, and orchard fruit crops should suffice. The dataset of crop areas presented here is the most comprehensive account of crop sowings presented in the literature and provides a useful resource for those interested in Australian agriculture. The field crop rankings presented represent only the area of crop sowings and should not be taken as rankings of importance in terms of the magnitude of all GHG fluxes. This awaits a more detailed analysis of climate, soils, and management practices across each of the regions where the crops are grown and their relationships to CO 2, nitrous oxide and methane fluxes. For pastures, there is a need for more detailed, up to date, spatially explicit information on the predominant sown pasture types across the Australian cropping belt before C balances for these can be more reliably modelled at the desired spatial scale.
  • Authors:
    • Bernardi, A.
    • Harden, S.
    • Wilson, B.
    • Young, R.
  • Source: Australian Journal of Soil Research
  • Volume: 47
  • Issue: 3
  • Year: 2009
  • Summary: Australian agriculture contributes an estimated 16% of all national greenhouse gas emissions, and considerable attention is now focused on management approaches that reduce net emissions. One area of potential is the modification of cropping practices to increase soil carbon storage. This paper report short-medium term changes in soil carbon under zero tillage cropping systems and perennial vegetation, both in a replicated field experiment and on nearby farmers' paddocks, on carbon-depleted Black Vertosols in the upper Liverpool Plains catchment. Soil organic carbon stocks (C S ) remained unchanged under both zero tillage long fallow wheat ( Triticum aestivum)-sorghum ( Sorghum) rotations and zero tillage continuous winter cereal in a replicated field experiment from 1994 to 2000. There was some evidence of accumulation of C S under intensive (>1 crop/year) zero tillage response cropping. There was significant accumulation of C S (~0.35 tonnes/ha/year) under 3 types of perennial pasture, despite removal of aerial biomass with each harvest. Significant accumulation was detected in the 0-0.1, 0.1-0.2, and 0.2-0.4 m depth increments under lucerne and the top 2 increments under mixed pastures of lucerne and phalaris and of C3 and C4 perennial grasses. Average annual rainfall for the period of observations was 772 mm, greater than the 40-year average of 680 mm. A comparison of major attributes of cropping systems and perennial pastures showed no association between aerial biomass production and accumulation rates of C S but a positive correlation between the residence times of established plants and accumulation rates of C S . C S also remained unchanged (1998/2000-07) under zero tillage cropping on nearby farms, irrespective of paddock history before 1998/2000 (zero tillage cropping, traditional cropping, or ~10 years of sown perennial pasture). These results are consistent with previous work in Queensland and central western New South Wales suggesting that the climate (warm, semi-arid temperate, semi-arid subtropical) of much of the inland cropping country in eastern Australia is not conducive to accumulation of soil carbon under continuous cropping, although they do suggest that C S may accumulate under several years of healthy perennial pastures in rotation with zero tillage cropping.
  • Authors:
    • Hill, J.
    • Jacobs, J. L.
    • Jenkin, T.
  • Source: Animal Production Science
  • Volume: 49
  • Issue: 7
  • Year: 2009
  • Summary: The efficient production and subsequent utilisation of home-grown forage is seen as the cornerstone of profitability of the dairy industry as it leads to lower unit costs of milk production compared with purchased forage or grain supplements. Cereals such as wheat ( Triticum aestivum L.), oats ( Avena sativa L.) and triticale ( Triticum * Triticosecale) all have the potential to produce high forage dry matter (DM) yields. These forages are not widely grown within dryland Australian dairy systems and there is a paucity of information on both the agronomic requirements and subsequent ensiling and feed-out management under these conditions. The experiment reported in this paper examines the DM yield, nutritive and ensiling characteristics of three small-grain cereals (triticale, wheat and oats) cut at various stages of development and ensiled with or without silage additives. We hypothesised that: (1) delaying harvesting until later stages of growth would result in higher DM yields, but negatively impact on both nutritive and fermentation characteristics of subsequent silages; (2) ensiling wilted material at earlier harvests would improve fermentation characteristics compared with direct ensiled material; and (3) the use of silage additives at all harvests would improve fermentation characteristics of resultant silages compared with untreated silages. Apart from winter oats, the estimated metabolisable energy of forages was highest at the boot stage of growth, declined during anthesis and then rose again during milk and soft-dough stage of growth. The crude protein content of forages declined with maturity, with final values at soft dough below 90 g/kg DM. Neutral detergent fibre content was highest at anthesis and then declined, with lowest values observed at soft dough (497-555 g/kg DM). In the majority of cases silages were well preserved, with direct ensiled material having pH values generally below 4.5 and wilted material below 5.0, with limited proteolysis as assessed by ammonia-N contents in the range of 5-15% of total-N. The production of volatile fatty acids and lactic acid was influenced by wilting and the use of additives. Generally, wilted silages fermented less than the corresponding direct ensiled forages, whereas the use of Sil-All 4*4 additive resulted in a lactic acid-dominant fermentation compared with LaSil additive, which resulted in a greater proportion of acetic acid as an end product of fermentation. The findings of the present study highlight the potential of forage cereals to produce high DM yields for whole crop cereal silage. The timing of harvest directly influences nutritive characteristics of forages for ensiling. The use of silage additives can assist in controlling fermentation pathways during ensilage, ensuring the production of silages with fermentation attributes more likely to lead to higher intakes when fed to animals.
  • Authors:
    • Penfold, C. M.
    • McNeill, A. M.
  • Source: Crop and Pasture Science
  • Volume: 60
  • Issue: 2
  • Year: 2009
  • Summary: Maintenance of available phosphorus (P) is a problem faced by both conventional and organic systems but it is exacerbated in the latter given that manufactured inorganic sources of P fertiliser are not permitted under the International Federation of Organic Agriculture Movements certification guidelines. The focus of this paper is a discussion of potential agronomic strategies to assist in sustainable management of the soil P resource in organic and low-input broadacre farming systems within the Australian rain-fed cereal-livestock belt. The paper considers three broad strategies for agronomic management of P in this context and draws on reported research from overseas and within Australia. An analysis of the current knowledge suggests that the option most likely to ensure that soluble P is not a limitation in the system is the importation of allowable inputs that contain P from off-farm, although for much of the Australian cereal-livestock belt the immediate issue may be access to economically viable sources. Research targeted at quantifying the economic and biological benefits to the whole-farm system associated with the adoption of these practices is required. Improving the P-use efficiency of the system by incorporating species into rotation or intercropping systems that are able to use P from less soluble sources has been a successful strategy in parts of the world with climate similar to much of the Australian cereal-sheep belt, and deserves further research effort in Australia. Agronomic management to maximise quantity and quality of pasture and crop plant residues undoubtedly builds labile soil organic matter and facilitates P cycling, but the strategy may be of limited benefit in low-rainfall areas that do not have the capacity to produce large biomass inputs. Evidence that organic or low-input systems naturally increase the numbers and diversity of soil organisms is sparse and published studies from Australian systems suggest that P nutrition is not enhanced. However, seed and soil microbial inoculants to facilitate improved P uptake have been developed and are currently being field tested in Australia. Progress in selection and breeding for cereal genotypes that are more P efficient and other plant genotypes that can use less labile P sources, is gaining momentum but still remains a long-term prospect, and may involve genetic modification which will not be acceptable for organic systems.
  • Authors:
    • Kelly,K.
    • Graham,J.
    • Biswas,W. K.
    • John,M. B.
  • Source: 6th Australian Conference on Life Cycle Assessment
  • Year: 2009
  • Authors:
    • Chen,Deli
    • Walker,Charlie
    • Wang,Weijing
    • Kelly,Kevin
    • Turner,Debra
    • Edis,Robert
    • Suter,Helen
  • Source: Annual Meeting of the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
  • Year: 2009
  • Authors:
    • Eckard, R.
    • Henry, B.
  • Source: Tropical Grasslands
  • Volume: 43
  • Year: 2009
  • Summary: Agriculture is responsible for a significant proportion of total anthropogenic greenhouse gas emissions (perhaps 18% globally), and therefore has the potential to contribute to efforts to reduce emissions as a means of minimising the risk of dangerous climate change. The largest contributions to emissions are attributed to ruminant methane production and nitrous oxide from animal waste and fertilised soils. Further, livestock, including ruminants, are an important component of global and Australian food production and there is a growing demand for animal protein sources. At the same time as governments and the community strengthen objectives to reduce greenhouse gas emissions, there are growing concerns about global food security. This paper provides an overview of a number of options for reducing methane and nitrous oxide emissions from ruminant production systems in Australia, while maintaining productivity to contribute to both objectives. Options include strategies for feed modification, animal breeding and herd management, rumen manipulation and animal waste and fertiliser management. Using currently available strategies, some reductions in emissions can be achieved, but practical commercially available techniques for significant reductions in methane emissions, particularly from extensive livestock production systems, will require greater time and resource investment. Decreases in the levels of emissions from these ruminant systems (i.e., the amount of emissions per unit of product such as meat) have already been achieved. However, the technology has not yet been developed for eliminating production of methane from the rumen of cattle and sheep digesting the cellulose and lignin-rich grasses that make up a large part of the diet of animals grazing natural pastures, particularly in arid and semi-arid grazing lands. Nevertheless, the abatement that can be achieved will contribute significantly towards reaching greenhouse gas emissions reduction targets
  • Authors:
    • Graham, J.
    • Phelan, A.
    • Kelly, K. B.
    • Officer, S. J.
  • Source: Climate Change and Resources
  • Year: 2009
  • Authors:
    • White, I.
    • Denmead, O. T.
    • Macdonald, B. C. T.
  • Source: Proceedings of the Australian Society of Sugar Cane Technologists
  • Volume: 31
  • Year: 2009
  • Authors:
    • Graham, J.
    • Kelly, K.
    • Armstrong, R.
    • Phillips, F.
    • Officer, S.
  • Source: Proceedings of Greenhouse 2009
  • Year: 2009