Dryland Salinity (dryland + salinity)

Distribution by Scientific Domains

Selected Abstracts

Climate Change and the Economics of Farm Management in the Face of Land Degradation: Dryland Salinity in Western Australia

Michele John
Projected changes in climate would affect not only the profitability of agriculture, but also the way it is managed, including the way issues of land conservation are managed. This study provides a detailed analysis of these effects for an extensive dryland farming system in south-west Australia. Using a whole-farm linear programming model, with discrete stochastic programming to represent climate risk, we explore the consequences of several climate scenarios. Climate change may reduce farm profitability in the study region by 50% or more compared to historical climate. Results suggest a decline in the area of crop on farms, due to greater probability of poor seasons and lower probability of very good seasons. The reduced profitability of farms would likely affect the capacity of farmers to adopt some practices that have been recommended to farmers to prevent land degradation through dryland salinization. In particular, establishment of perennial pastures (lucerne or alfalfa, Medicago sativa), woody perennials ("oil mallees", Eucalyptus spp.), and salt-tolerant shrubs for grazing ("saltland pastures", Atriplex spp.) may become slightly more attractive in the long run (i.e., relative to other enterprises) but harder to adopt due to their high establishment costs in the context of lower disposable income. Les changements climatiques prévus influeraient non seulement sur la rentabilité de l'agriculture, mais aussi sur la gestion, y compris la façon de gérer les questions de conservation des terres. La présente étude offre une analyse détaillée de ces effets sur un système d'aridoculture extensive dans le sud-ouest de l'Australie. À l'aide d'un modèle de programmation linéaire d'une exploitation, comprenant une programmation stochastique discrète pour représenter le risque lié aux changements climatiques, nous avons examiné les conséquences de plusieurs scénarios climatiques. Dans la région à l'étude, un changement climatique pourrait diminuer la rentabilité d'une exploitation de 50 p. 100 ou plus par rapport au climat historique. Les résultats ont laissé supposer un déclin dans le domaine des cultures, en raison de la probabilité accrue de connaître des saisons médiocres et de la probabilité diminuée de connaître saisons exceptionnelles. Une diminution de la rentabilité des exploitations freinerait probablement la capacité des producteurs à adopter certaines pratiques recommandées pour prévenir la dégradation des sols par la salinisation des terres arides. Certaines pratiques, telles que l'établissement de pâturages de plantes fourragères vivaces (luzerne ou Medicago sativa), de plantes ligneuses vivaces (Eucalyptus) et d'arbustes tolérants au sel (Atriplex), peuvent devenir un peu plus attrayantes à long terme (c'est-à-dire, comparativement à d'autres pratiques), mais également plus difficiles à adopter en raison des coûts d'établissement élevés dans un contexte de faible revenu disponible. [source]

Stream salinization is associated with reduced taxonomic, but not functional diversity in a riparian plant community

Abstract Dryland salinity presents an overwhelming threat to terrestrial and aquatic habitats in Australia, and yet there remains very little empirical evidence of the impacts of secondary salinization on the biodiversity of riparian communities. Here we describe the response of a riparian plant community to stream and soil salinization, 25 years after the experimental clearing of a catchment in south-western Australia. Riparian plant species diversity was inversely related to soil salinity, and plant species composition was significantly altered by increased soil salinity. Despite the evidence for an impact of salinization on the taxonomic diversity and composition of the riparian plant community, there was little evidence for any effect of salinization on functional group diversity, or on ecological functioning, as measured by the percentage of above-ground plant cover. [source]

Dryland salinity: economic, scientific, social and policy dimensions

David J. Pannell
A broad range of information relevant to salinity is reviewed in order to critically evaluate existing and prospective policy responses. The review includes issues of hydrogeology, farmer perceptions and preferences, farm-level economics of salinity management practices, spill-over benefits and costs from salinity management, and politics. The technical challenge of preventing salinity is far greater than previously recognised. The farm-level economics of currently available management practices for salinity prevention are adverse in many situations. Off-site benefits from on-farm practices are often small and long delayed. Past national salinity policies have been seriously flawed. While current policy proposals include positive elements, they have not sufficiently escaped from the past. [source]

Costing yield loss from acidity, sodicity and dryland salinity to Australian agriculture

S. Hajkowicz
Abstract Salinity, sodicity and acidity are three major soil constraints that limit crop and pasture yields in Australia. In this paper estimates are made of the potential benefits arising from their treatment by measuring and mapping their impact on agricultural profit. This is achieved by estimating the increase in profit for Australia's main commodities that would occur if the three soil constraints were costlessly ameliorated. These estimates reveal the upper achievable limit on investment returns. They are also indicative of each soil constraint's economic significance to Australian agriculture. It was found that costless removal of salinity would increase annual profits by A$187 million, sodicity by A$1034·6 million and acidity by A$1584·5 million. This equates to 2·9,per,cent, 15·8,per,cent and 24·2,per,cent of total net economic return. It was also found that worsening salinity extent and severity over 2000,2020 has a present value of A$496,A$712 million. Although soil salinity is currently the focus of much public attention, this analysis suggests that from a production viewpoint the correction of sodic and acidic soils may create greater private economic benefit. Opportunities vary considerably among industries. In particular, there is considerable opportunity for the horticultural and viticultural sector to address acidity issues. Whether gross benefits translate into net benefits is a complex question requiring access to context and location-specific information. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Diversity and salt tolerance of native Acacia rhizobia isolated from saline and non-saline soils

Abstract Re-establishing native vegetation in stressed soils is of considerable importance in many parts of the world, leading to significant interest in using plant,soil symbiont interactions to increase the cost-effectiveness of large-scale restoration. However, effective use of soil microbes in revegetation requires knowledge of how microbe communities vary along environmental stress gradients, as well as how such variation relates to symbiont effectiveness. In Australia, shrubby legumes dominate many ecosystems where dryland salinity is a major issue, and improving plant establishment in saline soils is a priority of regional management agencies. In this study, strains of rhizobial bacteria were isolated from a range of Acacia spp. growing in saline and non-saline soils. Replicates of each strain were grown under several salinity levels in liquid culture and characterized for growth and salt tolerance. Genetic characterization of rhizobia showed considerable variation among strains, with salt tolerance and growth generally higher in rhizobial populations derived from more saline soils. These strains showed markedly different genetic profiles and generic affiliations to those from more temperate soils, suggesting community differentiation in relation to salt stress. The identification of novel genomic species from saline soils suggests that the diversity of rhizobia associated with Australian Acacia spp. is significantly greater than previously described. Overall, the ability of some symbiotically effective strains to tolerate high salinity is promising with regard to improving host plant re-establishment in these soils. [source]

Establishment of native perennial shrubs in an agricultural landscape

Abstract Native vegetation has been destroyed or dramatically modified throughout agricultural regions of southern Australia. Extensive restoration of native perennial vegetation is likely to be crucial in these areas for the persistence of native plant and animal species, to ameliorate dryland salinity and soil degradation, and to maintain long-term agricultural production. The long-term resilience of these systems will be dependent on the ability of key functional taxa, such as perennial shrubs, to recruit and persist. In this study, we examine the factors limiting establishment of two perennial shrubs in formerly cropped land, the rare Maireana rohrlachii and the common Maireana decalvans. Field and laboratory observations suggest that establishment of both species is not limited by life-history traits following cultivation. Both species established and persisted under varying levels of plant competition. Similarities existed between species in their initial germination rates. Weak differences were found between species in the growth and survival rates under different levels of competition. The main difference between the two species was in the decline of germinability of fruits with increasing fruit age. From the data, it is difficult to determine what factors limit the establishment of perennial shrubs in these landscapes. The main hypothesis that can be advanced is that establishment of shrub species appears to be limited by propagule availability and this is likely to be a function of past and present grazing management rather than cultivation per se. Further investigation of these land-use practices may give greater insight into the factors affecting the establishment of this life form across these landscapes. [source]

Evaluating combined land conservation benefits from perennial pasture: lucerne (Medicago sativa L.) for management of dryland salinity and herbicide resistance in Western Australia,

Graeme J. Doole
The inclusion of perennial pasture phases in cropping rotations has been widely promoted throughout Australia for reducing the incidence of dryland salinity. To a lesser extent, they have also been promoted to enhance the management of herbicide-resistant weeds. No previous economic analysis of perennial pasture has considered both of these benefits. This study combines a dynamic linear programming model to estimate the magnitude of salinity-related benefits and a complex simulation model to assess the economics of herbicide-resistance management. We present a case study of the perennial pasture lucerne (Medicago sativa L.) in the Wheatbelt of Western Australia, where the weed annual ryegrass (Lolium rigidum Gaudin) is resistant to multiple herbicide groups. Sequences incorporating lucerne are the most profitable land use at the standard set of parameter values if (i) annual ryegrass is resistant to all selective herbicides, (ii) the water table is so shallow (approximately < 3.5 m deep) that frequent rotation with perennials is required to avert soil salinisation, (iii) sheep production is highly profitable, or (iv) there is a combination of less extreme cases. The value of perennial pasture is sufficient under these circumstances to overcome its high establishment cost and the displacement of multiple years of crop. Consideration of dryland salinity and herbicide resistance are about equally important in evaluating the economics of lucerne; neither should be neglected. [source]