Littérature scientifique sur le sujet « Farm risks South Australia Eyre Peninsula Management »

The emerging paradigm to manage the spread of dryland salinity is the manipulation of farming practice to provide both a reduction in recharge and a commercial return to farm enterprises. Recent work has attempted to classify the groundwater systems across Australia into distinct provinces, with the implication that the flow processes, and therefore remediation strategies, of catchments within each province are similar. This paper presents a case study of the Wanilla catchment on the Eyre Peninsula in South Australia. This catchment is in the groundwater province that includes 60% of the dryland salinity expression in Australia. The results of conceptual and numerical modelling of the catchment suggest that the land management for reduced recharge paradigm may be less effective in this groundwater province than in others. The scale of expression and salinity history of such catchments provides further impediments to management options aimed at controlling or reversing existing dryland salinity.

Dissolved organic carbon (DOC) is important to microbial activity and nutrient cycling, and its concentration is sensitive to pH. Despite the importance of alkaline soils to agricultural production in southern Australia, few studies have documented the concentrations of soil organic carbon (C) and DOC or described the effects of soil properties and management practices on DOC in these soils. A survey of 33 paddocks from the Eyre Peninsula and mid-North regions of South Australia and north-western Victoria demonstrated significant variation in pH, soil organic C and DOC. Carbon stocks in the surface 30cm were 40–55tC/ha and were lowest in paddocks from Victoria. Soils from South Australia had higher DOC concentrations in the top 20cm than soils from Victoria. Principal component analysis suggested variation in DOC was increased by high pH, electric conductivity and the concentration of exchangeable Na, and was reduced by the concentration of exchangeable Ca and clay content. Mid-infrared Fourier transform infrared spectroscopy identified regional differences in the composition of soil organic C, with high amounts of charcoal in Eyre Peninsula soils. Farm management practices had little effect on soil organic C but influenced DOC. Grain yield and DOC concentration were inversely related across and within regions which appeared to be related to the intensity of cropping having opposite influences on yield and DOC. Compared with international data, DOC concentrations were high relative to the amount of soil organic C and, in contrast to many previous studies, DOC in all regions increased with depth.

Dual-purpose cereals are employed in the high-rainfall zone of southern Australia to provide additional winter forage. Recently there has been interest in applying this technology in the drier environments of South and Western Australia. It would therefore be useful to gain an understanding of the trade-offs and risks associated with grazing wheat crops in different locations. In this study the APSIM (Agricultural Production Systems Simulator) crop and soil simulation models were linked to the GRAZPLAN pasture and livestock models and used to examine the benefits and costs of grazing cereal crops at 21 locations spanning seven of the regions participating in the Grain & Graze research, development and extension program. A self-contained part of a mixed farm (an annual pasture–wheat rotation plus permanent pastures) supporting a breeding ewe enterprise was simulated. At each location the consequences were examined of: (i) replacing a spring wheat cultivar with a dual-purpose cultivar (cv. Wedgetail or Tennant) in 1 year of the rotation; and (ii) either grazing that crop in winter, or leaving it ungrazed. The frequency of early sowing opportunities enabling the use of a dual-purpose cultivar was high. When left ungrazed the dual-purpose cultivars yielded less grain on average (by 0.1–0.9 t/ha) than spring cultivars in Western Australia and the Eyre Peninsula but more (by 0.25–0.8 t/ha) in south-eastern Australia. Stocking rate and hence animal production per ha could be increased proportionately more when a dual-purpose cultivar was used for grazing; because of the adjustments to stocking rates, grazing of the wheat had little effect on lamb sale weights. Across locations, the relative reduction in wheat yield caused by grazing the wheats was proportional to the grazing pressure upon them. Any economic advantage of moving to a dual-purpose system is likely to arise mainly from the benefit to livestock production in Western Australia, but primarily from grain production in south-eastern Australia (including the Mallee region). Between years, the relationship between increased livestock production and decreased grain yield from grazing crops shifts widely; it may therefore be possible to identify flexible grazing rules that optimise this trade-off.

In this paper we apply a conservation genomics approach to make evidence-based management recommendations for Acacia whibleyana, an endangered shrub endemic to Eyre Peninsula, South Australia. We used population genomic analysis to assess genetic connectivity, diversity, and historical inbreeding across all known stands of the species sampling remnant stands, revegetated stands of unknown origin, and a post-fire seedling cohort. Our results indicate a degree of historical connectivity across the landscape, but habitat loss and/or pollinator community disruption are potential causes of strong genetic structure across the remnant stands. Remnant stands had low genetic diversity and showed evidence of historical inbreeding, but only low levels of intra-stand relatedness indicating that risks of contemporary inbreeding are low. Analysis of a post-fire first generation cohort of seedlings showed they likely resulted from intra-stand matings, resulting in reduced genetic diversity compared to the parents. However, admixed seedlings in this cohort showed an increase in heterozygosity relative to likely sources and the non-admixed seedlings of the same stand. Assisted inter-stand gene flow may prove an effective management strategy to boost heterozygosity and corresponding increases in adapting capacity in this endangered species.

"November 2002." Bibliography: leaves 73-80. Identifies main sources of farming risk in the Upper Eyre Peninsula as climate variability and financial risk. Finds that farmers manage risk by having high equity and off-farm investment, using gross margin analysis, having farm management deposits, diversifying varieties, minimizing tillage, relying on experts for grain marketing and keeping stock for high price periods.