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Medicago Sativa (medicago + sativa)
Terms modified by Medicago Sativa Selected AbstractsThe significance of a facultative bacterium to natural populations of the pea aphid Acyrthosiphon pisumECOLOGICAL ENTOMOLOGY, Issue 2 2003A. C. Darby Abstract. 1., Laboratory studies have implicated various accessory bacteria of aphids as important determinants of aphid performance, especially on certain plant species and under certain thermal regimes. One of these accessory bacteria is PABS (also known as T-type), which is distributed widely but is not universal in natural populations of the pea aphid Acyrthosiphon pisum in the U.K. 2., To explore the impact of PABS on the performance of A. pisum , the nymphal development time and fecundity of aphids collected directly from natural populations and caged on the host plant Vicia faba in the field were quantified. Over 4 consecutive months June,September 1999, the performance of PABS-positive and PABS-negative aphids did not differ significantly. 3., Deterministic modelling of the performance data showed that the variation in simulated population increase of PABS-positive and PABS-negative aphids would overlap substantially. 4., Analysis of aphids colonising five host plants ( Lathyrus odoratus , Medicago sativa , Pisum sativum , Trifolium pratense , Vicia faba ) between April and September 2000 and 2001, identified no robust differences between the distribution of PABS-positive and PABS-negative aphids on different plants and with season or temperature. 5., It is concluded that PABS is not an important factor shaping the performance or plant range of A. pisum under the field conditions tested. Reasons for the discrepancies between this study and laboratory-based studies are considered. [source] Biodiversity and biocontrol: emergent impacts of a multi-enemy assemblage on pest suppression and crop yield in an agroecosystemECOLOGY LETTERS, Issue 9 2003Bradley J. Cardinale Abstract The suppression of agricultural pests has often been proposed as an important service of natural enemy diversity, but few experiments have tested this assertion. In this study we present empirical evidence that increasing the richness of a particular guild of natural enemies can reduce the density of a widespread group of herbivorous pests and, in turn, increase the yield of an economically important crop. We performed an experiment in large field enclosures where we manipulated the presence/absence of three of the most important natural enemies (the coccinellid beetle Harmonia axyridis, the damsel bug Nabis sp., and the parasitic wasp Aphidius ervi) of pea aphids (Acyrthosiphon pisum) that feed on alfalfa (Medicago sativa). When all three enemy species were together, the population density of the pea aphid was suppressed more than could be predicted from the summed impact of each enemy species alone. As crop yield was negatively related to pea aphid density, there was a concomitant non-additive increase in the production of alfalfa in enclosures containing the more diverse enemy guild. This trophic cascade appeared to be influenced by an indirect interaction involving a second herbivore inhabiting the system , the cowpea aphid, Aphis craccivora. Data suggest that high relative densities of cowpea aphids inhibited parasitism of pea aphids by the specialist parasitoid, A. ervi. Therefore, when natural enemies were together and densities of cowpea aphids were reduced by generalist predators, parasitism of pea aphids increased. This interaction modification is similar to other types of indirect interactions among enemy species (e.g. predator,predator facilitation) that can enhance the suppression of agricultural pests. Results of our study, and those of others performed in agroecosystems, complement the broader debate over how biodiversity influences ecosystem functioning by specifically focusing on systems that produce goods of immediate relevance to human society. [source] Seasonal changes in herbage mass and nutritive value of a range of grazed legume swards under Mediterranean and cool temperate conditionsGRASS & FORAGE SCIENCE, Issue 3 2007U. Sölter Summary Seasonal changes in herbage mass and herbage quality of legume-based swards under grazing by sheep or cattle were investigated at four locations in climatically different zones of Europe: Sardinia (Italy), southern France, northern Germany and south-west England (UK). At each location standard treatments were applied to legumes typical of species widely used in each locality: Medicago polymorpha in Italy, Medicago sativa in France, and Trifolium repens in Germany and in UK. At each site comparisons were made of two other legumes: Trifolium subterraneum and Hedysarum coronarium in Italy, Onobrychis sativa and Trifolium incarnatum in France, Trifolium pratense and Lotus corniculatus in Germany, and Trifolium ambiguum and L. corniculatus in UK. Legumes were sown in mixture with locally appropriate companion grasses, and measurements were made over two or three grazing periods. In Italy M. polymorpha swards gave the greatest herbage mass in grazing period 1 but H. coronarium was more persistent. At the French site all legumes established poorly with no significant herbage mass differences between treatments. At both the UK and German sites L. corniculatus maintained a high proportion of legume in the sward; T. repens showed poor persistence under continuous sheep grazing in UK but persisted under cattle grazing in Germany, while T. ambiguum was slow to establish in the UK, and T. pratense proved to be of comparable herbage mass to the standard T. repens -based sward in the last year of the experiment. The concentration of crude protein and in vitro digestibility of organic matter in the dry matter of herbage showed greater within-season variation than between treatments at each site. It is concluded that, in addition to currently used species, legume-based swards containing H. coronarium, O. sativa and L. corniculatus all have potential to contribute to forage production for low-input grazing and their use merits further consideration in systems of livestock production in Europe. [source] Environmental factors during seed development of narrow-leaved bird's-foot-trefoil (Lotus tenuis) influences subsequent dormancy and germinationGRASS & FORAGE SCIENCE, Issue 4 2003A. A. Clua Abstract Narrow-leaved bird's-foot-trefoil (Lotus tenuis) is a perennial forage legume adapted to waterlogged and heavy and infertile soils and can replace alfalfa (Medicago sativa) in areas with these soils in Argentina. Its seeds are hard and water-impermeable but the effects of environmental factors on seed dormancy and germination are not known. The objective was to evaluate the hypothesis that water availability during seed development and maturation affects the degree of hardseededness in L. tenuis by changing seed coat properties, conditioning water uptake through the seed coat; and subsequently affecting dormancy, germination and speed of germination. Seeds were harvested in December/January and in February in both 1993/1994 and 1994/1995 from a permanent pasture of L. tenuis growing in a Hapludol soil in San Miguel del Monte province of Buenos Aires. Environmental conditions of each anthesis-harvest period were determined. Seeds of each harvest were subjected to chilling, washing and mechanical scarification. After 12 months seeds from each harvest were observed in a scanning electron microscope. The water deficit of the soil and relative humidity were greater in the second than the first anthesis-harvest period in both seasons. In 1993/1994 the control treatment in December had a higher germination rate than the February control seeds (0·40 vs. 0·20) and a faster germination rate. Mechanical scarification and chilling significantly enhanced the germination rate (0·95) and its speed in seeds of both harvests. Low temperatures significantly enhanced germination rate, starting after 60 d for the seeds harvested in December, and 90 d for the seeds harvested in February. In 1994/1995 the results were similar but both the January and February control treatments had higher germination rates (0·60 vs. 0·40) than in the previous year. Seeds harvested in February were more dormant in both years. These differences could be explained by the conditions in February anthesis-harvest period in both years that could have hastened the natural dehydration process of seed, changing integument structure and enhancing its impermeability. [source] The host plant range of the pea aphid subspecies Acyrthosiphon pisum ssp. destructor (Johnson) (Hom., Aphididae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 6 2002R. I. K. McVean The plant species used were: Lotus uliginosus, Medicago sativa, Melilotus officinalis, Ononis repens, Sarothamnus scoparius, Trifolium hybridum, Trifolium pratense, Trifolium repens, Vicia cracca and Vicia faba. Vicia faba and Trifolium hybridum were the plants on which aphids reached the greatest size, took the least time to reach maturity, and experienced the lowest mortality. The time taken for the aphids to develop to maturity was negatively correlated with adult size, whereas survival to maturity was positively correlated with adult size. The host preference of the aphids was also assessed. The plant species selected as hosts by alatae were those on which their offspring performed best. [source] Adaptation of Medicago sativa cv. Gabès to long-term NaCl stressJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 2 2005Néziha Boughanmi Abstract The perennial Medicago sativa cv. Gabès is widely grown on saline soils in Tunisian oases. The mechanisms by which this NaCl-tolerant cultivar maintains a positive growth balance were analyzed. In this plant of considerable agronomic interest, biochemical analyses were conducted in order to study the effects of salinity on mature leaves. Free-radical detoxification mechanisms and changes induced by the accumulation of reactive oxygen species (ROS) in response to the NaCl stress were compared between the upper (young) and lower (old) carbohydrate source leaves. Long-term NaCl (150 mM) treatment significantly reduced the size of source leaves supporting growth. Salinity damage was greater in the lower than in the upper leaves. This damage was associated with a high Na+ : K+ ratio and a decrease in the activity of H2O2 -scavenging enzymes, leading to lipid peroxidation. In lower source leaves that were mainly affected by ionic stress, superoxide dismutase (SOD) was overexpressed and guaiacol peroxidase (GPX) activity increased. In contrast, in upper source leaves that were mainly exposed to water deficit, catalase and ascorbate peroxidase (APX) activities increased whereas GPX activity was unchanged. The upper source leaves maintained adequate ionic and water status and an efficient ROS detoxification, allowing sinks to be supplied with photoassimilates and maintaining a positive growth balance in this cultivar of alfalfa. Anpassung von Medicago sativa cv. Gabès an Langzeit-Salzstress Die perennierende Art Medicago sativa, Sorte "Gabès", wird verbreitet auf Salzböden in tunesischen Oasen angebaut. Die Mechanismen, die eine positive Wachstumsbilanz in dieser NaCl-toleranten Luzernensorte gewährleisten, wurden untersucht. In dieser agronomisch außerordentlich wichtigen Pflanze wurden biochemische Analysen durchgeführt, um Salzeffekte auf ausgewachsene Blätter zu bestimmen. Die Mechanismen zur Entgiftung freier Radikale (ROS) und die durch die ROS verursachten Veränderungen wurden in jungen und alten "Source"-Blättern vergleichend unter Salzstressbedingungen untersucht. Eine andauernde Behandlung mit NaCl (150 mM) führte zu einer signifikanten Reduzierung der Blattfläche, wobei diese Abnahme deutlicher an den älteren unteren als an den oberen jüngeren Blättern war. Sie ging einher mit einem hohen Na+:K+ -Verhältnis und einer Abnahme der Aktivität der H2O2 -abbauenden Enzyme, was zu einer Peroxidation von Lipiden führte. Besonders in den unteren "Source"-Blättern führte der Ionenstress zu einer Überexprimierung der Superoxid-Dismutase (SOD) und einer Zunahme der Guaiakol- Peroxidaseaktivität (GPX). Demgegenüber nahmen in den oberen "Source"-Blättern, die starkem Wasserdefizit ausgesetzt waren, die Aktivitäten von Katalase und Ascorbat-Peroxidase (APX) zu, während die GPX-Aktivität unverändert blieb. Die oberen "Source"-Blätter waren in der Lage, einen adäquaten Ionen- und Wasserzustand mit Hilfe einer effizienten ROS-Entgiftung aufrechtzuerhalten, und somit einen Rückgang der Bereitstellung von Photoassimilaten zu kompensieren. Dadurch wurde eine positive Wachstumsbilanz in dieser Luzernensorte unter Salinität gewährleistet. [source] Condensed tannins in tropical fodder crops and their in vitro biological activity: Part 2,JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 4 2004Juan López Abstract With the aim to evaluate the biological activity of purified condensed tannins of tropical forages we conducted two in vitro experiments. In the first, using a radial diffusion technique, the protein precipitation of free condensed tannins (FCT) from Manihot esculenta, leucaena leucocephala, Arachis pintoi, Guazuma ulmyfolia, Gliricidia sepium and of tannic acid on bovine serum albumin (ASB), papain, pepsin and trypsin at pH 5.0 and 6.8 was evaluated with a three-way analysis of variance. Significant effects (P , 0.05) for the tannin type, protein source, pH and their interactions were observed. Pepsin showed the highest protein precipitation (PP) at a pH of 5.0 (82.9 µg) with FCT of G ulmyfolia and the lowest (0 and 0.2 µg) of BSA with G sepium and A pintoi at pH 6.8. Experiments were then conducted using completely randomized designs in order to observe the effect of adding 0, 1.25 or 2.50 mg of FCT from M esculenta and L leucocephala to the rumen fluid-buffer in an in vitro dry matter digestibility test (IVDMD) of Medicago sativa and Brachiaria decumbens, The IVDMD value of M sativa (757 g kg,1) decreased with L leucocephala tannins, although with those of M esculenta it was increased (824 g kg,1 and 871 g kg,1, respectively) for 1.25 and 2.5 mg of FCT. The IVDMD value of B decumbens (774 g kg,1 without tannins) diminished with any tannin and any dose (P < 0.05). We conclude that there are differences in the FCT contents of fodder crops and in their biological activity measured as the capacity to precipitate proteins, which is modified by the type of tannin, the protein and the pH. The result of an IVDMD is regulated by the type of tannin and its dose. Copyright © 2004 Society of Chemical Industry [source] Chemical composition and ruminal degradability of lucerne (Medicago sativa) productsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 15 2001Arif F Mustafa Abstract A study was conducted to determine the chemical composition and in situ nutrient ruminal degradability of three lucerne products. These were dehydrated pellets, sun-cured pellets and cubes. Results of the chemical analysis showed that sun-cured pellets had the highest (P,<,0.05) neutral and acid detergent fibre as well as total carbohydrate levels, followed by cubes and dehydrated pellets respectively. Crude protein (CP) content was highest (P,<,0.05) for dehydrated pellets (204.3,g,kg,1), intermediate for sun-cured pellets (160.0,g,kg,1) and lowest for cubes (153.2,g,kg,1). Intermediately degradable CP (buffer-insoluble CP minus neutral detergent-insoluble CP) was the main protein fraction in the three products and was higher (P,<,0.05) in cubes than in dehydrated and sun-cured pellets. Estimated net energy of lactation was highest (P,<,0.05) for dehydrated pellets (5.9,MJ,kg,1), intermediate for cubes (5.23,MJ,kg,1) and lowest (P,<,0.05) for sun-cured pellets (5.15,MJ,kg,1). Results of the in situ experiment indicated that dehydrated pellets had higher (P,<,0.05) ruminal protein degradability than sun-cured pellets and cubes. The estimated ruminal escape protein values for dehydrated pellets, sun-cured pellets and cubes were 361, 420 and 498,g,kg,1 CP respectively. It was concluded that differences in chemical composition and ruminal degradability among the three lucerne products were mainly due to differences in stage of maturity. It was also concluded that the dehydration process failed to increase the ruminal escape protein value of dehydrated pellets relative to sun-cured pellets and cubes. © 2001 Society of Chemical Industry [source] Multi-site genetic modification of monolignol biosynthesis in alfalfa (Medicago sativa): effects on lignin composition in specific cell typesNEW PHYTOLOGIST, Issue 3 2008Jin Nakashima Summary ,,Independent antisense down-regulation of 10 individual enzymes in the monolignol pathway has generated a series of otherwise isogenic alfalfa (Medicago sativa) lines with varying lignin content and composition. These plants show various visible growth phenotypes, and possess significant differences in vascular cell size and number. ,,To better understand the phenotypic consequences of lignin modification, the distributions of lignin content and composition in stems of the various alfalfa lines at the cellular level were studied by confocal microscopy after staining for specific lignin components, and by chemical analysis of laser capture dissected tissue types. ,,Although all antisense transgenes were driven by the same promoter with specificity for vascular, fiber and parenchyma tissues, the impact of down-regulating a specific transgene varied in the different tissue types. For example, reducing expression of ferulate 5-hydroxylase reduced accumulation of syringyl lignin in fiber and parenchyma cells, but not in vascular elements. ,,The results support a model for cell type-specific regulation of lignin content and composition at the level of the monolignol pathway, and illustrate the use of laser capture microdissection as a new approach to spatially resolved lignin compositional analysis. [source] Growth and maintenance respiration for individual plants in hierarchically structured canopies of Medicago sativa and Helianthus annuus: the contribution of current and old assimilatesNEW PHYTOLOGIST, Issue 2 2004Markus Lötscher Summary ,,Respiratory costs of Medicago sativa and Helianthus annuus individuals growing in hierarchically structured stands in a controlled environment were analysed with regard to the daily rate of carbon (C) assimilation. ,,Net assimilation of new C (An, g C d,1) and respiration rates of new (Rnew, g C d,1) and old C (Rold, g C d,1) were assessed by 13CO2 labelling and gas exchange measurements. ,,Specific respiration rate of old C (rold, g C g,1 C d,1) decreased exponentially with increasing shoot biomass, but was not affected by the instantaneous relative growth rate (,wi). The growth coefficient g (Rnew: An) was c. 0.32. In the most severely shaded subordinate plants, g was < 0.2, but low g stimulated rold. The contribution of Rnew to total respiraton (fR, new) and the carbon use efficiency CUE (1 , R/(An +Rnew)) were c. 0.68 and 0.62 for ,wi > 0.1, respectively. For ,wi < 0.1, fR, new and CUE decreased with decreasing ,wi in both dominant and subordinate plants. ,,The results suggest that Rold was closely related to maintenance, whereas Rnew was primarily involved in growth. [source] Time-course of lipoxygenase, antioxidant enzyme activities and H2O2 accumulation during the early stages of Rhizobium,legume symbiosisNEW PHYTOLOGIST, Issue 1 2001Pablo Bueno Summary ,,The involvement of lipoxygenase and antioxidant enzyme activities as well as hydrogen peroxide (H2O2) accumulation are reported during early infection steps in alfalfa (Medicago sativa) roots inoculated either with a wild type Sinorhizobium meliloti or with a mutant defective in Nod-factor synthesis (Nod C,). ,,Compatibility between M. sativa and Rhizobium correlates, at least in part, with an increase in the activities of these enzymes, particularly catalase and lipoxygenase, during the preinfection period (up to 12 h). The mutant strain, defective in Nod-factor biosynthesis, showed a decrease in all enzyme activities assayed, and an increase in H2O2 accumulation. ,,Enhancement of scavenging activities for several reactive oxygen species correlated with compatibility of the S. meliloti,alfalfa symbiosis, whereas the Nod C, strain triggered a defence response. Nod factors were essential to suppress this response. ,,Increase in lipoxygenase and lipid hydroperoxide decomposing activities, observed during the first hours after inoculation with a compatible strain, could be related to tissue differentiation and/or the production of signal molecules involved in autoregulation of nodulation by the plant. [source] Cloning of nodule-specific cDNAs of Galega orientalisPHYSIOLOGIA PLANTARUM, Issue 4 2002Seppo Kaijalainen Differential display was applied in order to clone cDNAs expressed exclusively or predominantly in nodules, compared to uninoculated root tissue of Galega orientalis. Forty-five fragments were unique for nodule RNA. These fragments were reamplified and cloned. Six of them produced a nodule-specific signal on Northern hybridization. These six fragments were sequenced. Five of the sequenced fragments showed homology to nodulin-gene sequences in databases, among them Vicia faba mRNA for protein showing partial homology with Medicago sativa nodulin-25 (Nms25), Pisum sativum PsN466, V. faba CCP2 and CCP4, P. sativum ENOD3, and Maackia amurensis ENOD2. The remaining sequence had no significant homology with sequences in the databanks. Full-size cDNA for the homologue to V. faba mRNA for the protein showing partial homology with M. sativa nodulin-25 (Nms25) and P. sativum PsN466 were cloned and sequenced. [source] Use of RAPD and microsatellite (SSR) variation to assess genetic relationships among populations of tetraploid alfalfa, Medicago sativaPLANT BREEDING, Issue 4 2000A. Mengoni Abstract The level of random amplified polymorphic DNA (RAPD) and microsatellite variation present in four ecotypes and two varieties of alfalfa (lucerne) from Italian and Egyptian germplasm sources was evaluated. A sample of 100 plants from 10 populations was analysed by means of 41 RAPD markers and 37 simple sequence repeat (SSR) markers. Both molecular approaches revealed a high degree of genetic diversity within each of the cultivated populations and enabled each of the plants considered to be uniquely fingerprinted. The genetic relationships among plants and populations were analysed by computing AMOVA (analysis of molecular variance) and FST analyses. RAPDs were able to separate the Italian populations from the Egyptian variety. SSRs allowed strong separation of the four Italian alfalfa ecotypes. It was concluded that RAPD and microsatellites could be useful and powerful tools for assessing genetic variation and genetic relationships in tetraploid alfalfa. [source] Multi-site genetic modulation of monolignol biosynthesis suggests new routes for formation of syringyl lignin and wall-bound ferulic acid in alfalfa (Medicago sativa L.)THE PLANT JOURNAL, Issue 1 2006Fang Chen Summary Genes encoding seven enzymes of the monolignol pathway were independently downregulated in alfalfa (Medicago sativa) using antisense and/or RNA interference. In each case, total flux into lignin was reduced, with the largest effects arising from the downregulation of earlier enzymes in the pathway. The downregulation of l -phenylalanine ammonia-lyase, 4-coumarate 3-hydroxylase, hydroxycinnamoyl CoA quinate/shikimate hydroxycinnamoyl transferase, ferulate 5-hydroxylase or caffeic acid 3- O -methyltransferase resulted in compositional changes in lignin and wall-bound hydroxycinnamic acids consistent with the current models of the monolignol pathway. However, downregulating caffeoyl CoA 3- O -methyltransferase neither reduced syringyl (S) lignin units nor wall-bound ferulate, inconsistent with a role for this enzyme in 3- O -methylation ofS monolignol precursors and hydroxycinnamic acids. Paradoxically, lignin composition differed in plants downregulated in either cinnamate 4-hydroxylase or phenylalanine ammonia-lyase. No changes in the levels of acylated flavonoids were observed in the various transgenic lines. The current model for monolignol and ferulate biosynthesis appears to be an over-simplification, at least in alfalfa, and additional enzymes may be needed for the 3- O -methylation reactions of S lignin and ferulate biosynthesis. [source] Effect of different levels of Quebracho tannin on nitrogen utilization and growth performance of Najdi sheep fed alfalfa (Medicago sativa) hay as a sole dietANIMAL SCIENCE JOURNAL, Issue 5 2009Soliman N. AL-DOBAIB ABSTRACT A commercial tannin source (Quebracho tannin, QT), containing 75% condensed tannins (CT) in dry matter (DM) was used to evaluate the effects of addition of different levels of QT to alfalfa hay on the in vitro degradation kinetics of organic matter (OM) and nitrogen (N) in experiment 1 (Exp. 1), N utilization and microbial N synthesis (MNS) in experiment 2 (Exp. 2) and growth performance of growing Najdi lambs in experiment 3 (Exp. 3). Alfalfa hay was treated with QT at the levels of 0, 1, 2 and 3% of DM to form four treatments of QT0, QT1, QT2 and QT3 to have actual levels of CT being 0, 0.75, 1.5 and 2.25% of DM, respectively. Degradation rate and the effective degradability of N were significantly decreased (P < 0.05) for QT2 and QT3 as compared with the QT0. In Exp. 2, digestibility coefficients for OM, neutral detergent fiber and acid detergent fiber were significantly decreased (P < 0.05) at QT3, whereas QT1 and QT2 showed no difference toQT0. In the metabolism trial (Exp. 2), digested N (DN) and urinary N (UN) excretion for QT2 and QT3 were significantly decreased (P < 0.05) compared to QT0 and QT1. The DN and UN as percentage of N intake were 79.2, 76.9, 75.5 and 69.8%; and 24.4, 22.6, 19.9 and 19.6% for QT0, QT1, QT2 and QT3, respectively. QT2 had the highest MNS and the lowest value was in QT3, the MNS of the treatments were 18.1, 18.7, 19.2 and 15.8 g/day for QT0, QT1, QT2 and QT3, respectively. In the growth trial of 56 days duration (Exp. 3, n = 24 lambs), the addition of QT at the level of QT2 enhanced (P < 0.05) the average daily gain and feed conversion rate compared with the QT0, while, QT1 and QT3 had intermediate values. It is concluded that alfalfa hay treated with QT at the level of 2% of DM could be used to protect alfalfa N from ruminal degradation that would lead to improve growth performance of lambs. [source] Climate Change and the Economics of Farm Management in the Face of Land Degradation: Dryland Salinity in Western AustraliaCANADIAN JOURNAL OF AGRICULTURAL ECONOMICS, Issue 4 2005Michele 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] | |||||||||||||||||||||||||