Littérature scientifique sur le sujet « High-salinity soil »
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Articles de revues sur le sujet "High-salinity soil"
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Bethune, M. G., et T. J. Batey. « Impact on soil hydraulic properties resulting from irrigating salinesodic soils with low salinity water ». Australian Journal of Experimental Agriculture 42, no 3 (2002) : 273. http://dx.doi.org/10.1071/ea00142.
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Irrigation-induced salinity is a serious problem facing irrigated areas in the Murray–Darling Basin of Australia. Groundwater pumping with farm re-use for irrigation is a key strategy for controlling salinity in these irrigation areas. However, the re-use of highly saline–sodic groundwater for irrigation leads to accumulation of sodium in the soil profile and can result in sodic soils. Leaching of saline–sodic soils by winter rainfall and low salinity irrigation waters are 2 management scenarios likely to exacerbate sodicity problems. Characteristic to sodic soils is poor soil structure and potentially reduced soil permeability. Two indicators of soil permeability are infiltration rate and hydraulic conductivity. A replicated plot experiment was conducted to examine the long-term impact of irrigation with saline–sodic water on soil permeability. High levels of soil sodicity (ESP up to 45%) resulted from 10 years of saline irrigation. Over this period, leaching by winter rainfall did not result in long-term impacts on soil hydraulic properties. Measured soil hydraulic properties increased linearly with the salinity of the applied irrigation water. Leaching by irrigating with low salinity water for 13 months decreased soil salinity and sodicity in the topsoil. The resulting reduction in steady-state infiltration indicates soil structural decline of the topsoil. This trial shows that groundwater re-use on pasture will result in high sodium levels in the soil. Sodicity-related soil structural problems are unlikely to develop where there is consistent groundwater irrigation of pasture. However, structural decline of these soils is likely following the cessation of groundwater re-use.
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Shaw, E. Ashley, et Diana H. Wall. « Biotic Interactions in Experimental Antarctic Soil Microcosms Vary with Abiotic Stress ». Soil Systems 3, no 3 (27 août 2019) : 57. http://dx.doi.org/10.3390/soilsystems3030057.
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Biotic interactions structure ecological communities but abiotic factors affect the strength of these relationships. These interactions are difficult to study in soils due to their vast biodiversity and the many environmental factors that affect soil species. The McMurdo Dry Valleys (MDV), Antarctica, are relatively simple soil ecosystems compared to temperate soils, making them an excellent study system for the trophic relationships of soil. Soil microbes and relatively few species of nematodes, rotifers, tardigrades, springtails, and mites are patchily distributed across the cold, dry landscape, which lacks vascular plants and terrestrial vertebrates. However, glacier and permafrost melt are expected to cause shifts in soil moisture and solutes across this ecosystem. To test how increased moisture and salinity affect soil invertebrates and their biotic interactions, we established a laboratory microcosm experiment (4 community × 2 moisture × 2 salinity treatments). Community treatments were: (1) Bacteria only (control), (2) Scottnema (S. lindsayae + bacteria), (3) Eudorylaimus (E. antarcticus + bacteria), and (4) Mixed (S. lindsayae + E. antarcticus + bacteria). Salinity and moisture treatments were control and high. High moisture reduced S. lindsayae adults, while high salinity reduced the total S. lindsayae population. We found that S. lindsayae exerted top-down control over soil bacteria populations, but this effect was dependent on salinity treatment. In the high salinity treatment, bacteria were released from top-down pressure as S. lindsayae declined. Ours was the first study to empirically demonstrate, although in lab microcosm conditions, top-down control in the MDV soil food web.
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Aboelsoud, Hesham M., Mohamed A. E. AbdelRahman, Ahmed M. S. Kheir, Mona S. M. Eid, Khalil A. Ammar, Tamer H. Khalifa et Antonio Scopa. « Quantitative Estimation of Saline-Soil Amelioration Using Remote-Sensing Indices in Arid Land for Better Management ». Land 11, no 7 (8 juillet 2022) : 1041. http://dx.doi.org/10.3390/land11071041.
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Soil salinity and sodicity are significant issues worldwide. In particular, they represent the most dominant types of degraded lands, especially in arid and semi-arid regions with minimal rainfall. Furthermore, in these areas, human activities mainly contribute to increasing the degree of soil salinity, especially in dry areas. This study developed a model for mapping soil salinity and sodicity using remote sensing and geographic information systems (GIS). It also provided salinity management techniques (leaching and gypsum requirements) to ameliorate soil and improve crop productivity. The model results showed a high correlation between the soil electrical conductivity (ECe) and remote-sensing spectral indices SIA, SI3, VSSI, and SI9 (R2 = 0.90, 0.89, 0.87, and 0.83), respectively. In contrast, it showed a low correlation between ECe and SI5 (R2 = 0.21). The salt-affected soils in the study area cover about 56% of cultivated land, of which the spatial distribution of different soil salinity levels ranged from low soil salinity of 44% of the salinized cultivated land, moderate soil salinity of 27% of salinized cultivated land, high soil salinity of 29% of the salinized cultivated land, and extreme soil salinity of 1% of the salinized cultivated land. The leaching water requirement (LR) depths ranged from 0.1 to 0.30 m ha−1, while the gypsum requirement (GR) ranged from 0.1 to 9 ton ha−1.
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Aboelsoud, Hesham, Bernard Engel et Khaled Gad. « Effect of Planting Methods and Gypsum Application on Yield and Water Productivity of Wheat under Salinity Conditions in North Nile Delta ». Agronomy 10, no 6 (16 juin 2020) : 853. http://dx.doi.org/10.3390/agronomy10060853.
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Salinity and water shortage are the most important factors limiting crop productivity, so increasing the productivity of salt-affected soils is important to address the global food gap. Two field experiments were conducted under typical farm conditions in the North Nile Delta to study the effect of planting methods and gypsum application on wheat yield and water productivity under a range of water and soil salinity levels. In the first experiment, wheat was treated with gypsum (25%, 75%, and 100% gypsum-requirement) with moderate or high salinity in soil and water. The second experiment was conducted for two seasons at two sites to test three planting methods (flat, 60-cm furrows, and 120-cm raised-beds) under normal or high salinity levels of both soil and water. The results showed that gypsum alleviated the hazardous effects of salinity stress on grain yield. Raised furrows or beds under higher salinity levels increased soil salinity, and soil salinity was slightly increased with flat plots. Higher yields, water savings, and water productivities were achieved with raised furrows or beds under normal salinity. To improve yield under normal salinity conditions, raised beds are the recommended planting method. Furthermore, gypsum application in cultivated fields can mitigate the negative effects of salinity stress.
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Knewtson, Sharon J. B., M. B. Kirkham, Rhonda R. Janke, Leigh W. Murray et Edward E. Carey. « Soil Quality After Eight Years Under High Tunnels ». HortScience 47, no 11 (novembre 2012) : 1630–33. http://dx.doi.org/10.21273/hortsci.47.11.1630.
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The sustainability of soil quality under high tunnels will influence management of high tunnels currently in use and grower decisions regarding design and management of new high tunnels to be constructed. Soil quality was quantified using measures of soil pH, salinity, total carbon, and particulate organic matter (POM) carbon in a silt loam soil that had been in vegetable production under high tunnels at the research station in Olathe, KS, for eight years. Soil under high tunnels was compared with that in adjacent fields in both a conventional and an organic management system. The eight-year presence of high tunnels under the conventional management system resulted in increased soil pH and salinity but did not affect soil carbon. In the organic management system, high tunnels did not affect soil pH, increased soil salinity, and influenced soil carbon (C) pools with an increase in POM carbon. The increases in soil salinity were not enough to be detrimental to crops. These results indicate that soil quality was not adversely affected by eight years under stationary high tunnels managed with conventionally or organically produced vegetable crops.
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Mohammadi, Mohammad Hossein, et Mahnaz Khataar. « A simple numerical model to estimate water availability in saline soils ». Soil Research 56, no 3 (2018) : 264. http://dx.doi.org/10.1071/sr17081.
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We developed a numerical model to predict soil salinity from knowledge of evapotranspiration rate, crop salt tolerance, irrigation water salinity, and soil hydraulic properties. Using the model, we introduced a new weighting function to express the limitation imposed by salinity on plant available water estimated by the integral water capacity concept. Lower and critical limits of soil water uptake by plants were also defined. We further analysed the sensitivity of model results to underlying parameters using characteristics given for corn, cowpea, and barley in the literature and two clay and sandy loam soils obtained from databases. Results showed that, between two irrigation events, soil salinity increased nonlinearly with decreasing soil water content especially when evapotranspiration and soil drainage rate were high. The salinity weighting function depended greatly on the plant sensitivity to salinity and irrigation water salinity. This research confirmed that both critical and lower limits (in terms of water content) of soil water uptake by plants increased with evapotranspiration rate and irrigation water salinity. Since the presented approach is based on a physical concept and well-known plant parameters, soil hydraulic characteristics, irrigation water salinity, and meteorological conditions, it may be useful in spatio-temporal modelling of soil water quality and quantity and prediction of crop yield.
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Krzyżaniak, M., et J. Lemanowicz. « Enzymatic activity of the Kuyavia Mollic Gleysols (Poland) against their chemical properties ; ». Plant, Soil and Environment 59, No. 8 (31 juillet 2013) : 359–65. http://dx.doi.org/10.17221/211/2013-pse.
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The research results have shown that the enzyme pH index (0.49–0.83) confirmed the neutral or alkaline nature of the soils. Neither the changes in the content of available phosphorus nor in the activity of dehydrogenases, catalase, alkaline and acid phosphatase in soil were due to the factors triggering soil salinity; they were a result of the naturally high content of carbon of organic compounds, which was statistically verified with the analysis of correlation between the parameters. There were recorded highly significant values of the coefficients of correlation between the content of available phosphorus in soil and the activity of alkaline (r = 0.96; P < 0.05) and acid phosphatase (r = 0.91; P < 0.05) as well as dehydrogenase (r = 0.90; P < 0.05). To sum up, one can state that Mollic Gleysols in Inowrocław are the soils undergoing seasonal salinity; however, a high content of ions responsible for salinity is balanced with a high content of organic carbon, humus, phosphorus and calcium directly affecting the fertility of the soils analyzed. The activity of the enzymes depended on the natural content of carbon of organic compounds and not on the factors affecting the soil salinity, which points to the potential of such tests for soil environment monitoring.
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Liang, Xiaolong, Xiaoyu Wang, Ning Zhang et Bingxue Li. « Biogeographical Patterns and Assembly of Bacterial Communities in Saline Soils of Northeast China ». Microorganisms 10, no 9 (5 septembre 2022) : 1787. http://dx.doi.org/10.3390/microorganisms10091787.
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Increasing salinity undermines soil fertility and imposes great threats to soil ecosystem productivity and ecological sustainability. Microbes with the ability to adapt to environmental adversity have gained increasing attention for maintenance and restoration of the salt-affected soil ecosystem structure and functioning; however, the characterization of microbial communities in saline–sodic soils remains limited. This study characterized the bacterial community composition and diversity in saline–sodic soils along a latitude gradient across Northeast China, aiming to reveal the mechanism of physicochemical and geographic characteristics shaping the soil bacterial communities. Our results showed that the bacterial community composition and diversity were significantly impacted by soil pH, electrical conductivity, Na+, K+, Cl−, and CO32−. Significant differences in bacterial diversity were revealed along the latitude gradient, and the soil factors accounted for 58.58% of the total variations in bacterial community composition. Proteobacteria, Actinobacteria, Gemmatimonadetes, Chloroflexi, and Bacteroidetes were dominant across all samples. Actinobacteria and Gemmatimonadetes were significantly enriched in high soil sodicity and salinity, while Acidobacteria and Proteobacteria were suppressed by high pH and salt stress in the saline–sodic soils. Increase in soil pH and salinity significantly decreased bacterial species richness and diversity. Community composition analysis indicated that bacterial taxonomic groups (e.g., Bacillus, Egicoccus, Truepera, Halomonas, and Nitrolancea) that may adapt well to high salinity were greatly enriched in the examined soils. The findings collectively evidenced that bacterial community composition and diversity in a broad biographic scale were determined by niche-based environmental characteristics and biotic interactions. The profiling of the soil bacterial communities along the latitude gradient will also provide a basis for a better understanding of the salt-affected soil ecosystem functioning and restoration of these soil ecosystems.
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Ergashovich, Kholliyev Askar, Norboyeva Umida Toshtemirovna, Jabborov Bakhtiyor Iskandarovich et Norboyeva Nargiza Toshtemirovna. « Soil Salinity And Sustainability Of Cotton Plant ». American Journal of Agriculture and Biomedical Engineering 03, no 04 (22 avril 2021) : 12–19. http://dx.doi.org/10.37547/tajabe/volume03issue04-03.
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The following article deals with the data obtained as a result of the effect of soil salinity on the physiological properties and tolerance levels of medium-fibre cotton varieties. Also, changes in physiological processes under the influence of different levels of salinity and differences in the adaptive properties of varieties have been noted. Salinity had a negative impact on all studied cotton varieties, while the radical decline in yield and its quality was observed in varieties with high levels of adaptability and hardiness.
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Zhang, Lei, Li-ping Jing, Ning-wei Wang, Chen Fang, Yong-qiang Li et Zhen-dong Shan. « Electro-Osmosis Chemical Treatment of High-Salinity Soft Marine Soils : Laboratory Tests ». Open Civil Engineering Journal 11, no 1 (31 janvier 2017) : 109–20. http://dx.doi.org/10.2174/1874149501711010109.
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The electro-osmosis chemical treatment (ECT) is a useful method for improving soil strength. Some laboratory tests on ECT for strengthening high-salinity soft marine soils were investigated using self-designed laboratory facilities in this research. This study focused on improving the mechanical properties by using ECT method and analyzed the effects of using CaCl2 solution on soil strength owing to the electrolyte is an important factor for improving the bearing capacity of the high-salinity marine soils. Three groups of tests with different time for consolidation were performed to analyze the effective consolidation time on the ECT. In addition, several practical issues, including the current, voltage, energy consumption and the bearing capacity of the treated soils before and after experiments, were considered in the tests. The laboratory tests results demonstrated that the ECT technique is an effective method for improving the high-salinity marine soft soils. Furthermore, the definition of the effective time for consolidation was proposed for the ECT of high-salinity soft marine soils to improve the feasibility and economical efficiency of the ECT. This study provides some references and suggestions for practical application of the ECT technique for marine soft soils.
Thèses sur le sujet "High-salinity soil"
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Fahy, Brian Patrick. « The influence of salinity on the mechanical behavior of high plasticity soils ». Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90049.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 235-238).
This thesis investigates the influence of salinity on the mechanical behavior of smectitic rich high plasticity soils resedimented with pore fluid salinities ranging from 0 to 256 g/L. An extensive laboratory testing program involving Constant Rate of Strain (CRS) and K₀ consolidated undrained shear in compression triaxial testing (CK₀UC) was undertaken. Specimens tested in the modified CRS device reached axial effective stresses between 30 and 40 MPa. Triaxial testing was performed over a very wide range of effective stresses from 0.125 to 10 MPa, with one test consolidated to 63 MPa. Behavior is examined at pore fluid salinities of 4, 64, and 256 g/L. The shear behavior of all specimens was obtained in the normally consolidated region. Six different soils from the Gulf of Mexico region, ranging in liquid limit from 62 % to 90 %, were tested to determine the impact of varying salinity on one dimensional consolidation and permeability properties. The majority of testing was carried out on Gulf of Mexico - Eugene Island (GOM EI). This material was used to examine the behavior of a soil whose fabric has been changed by the removal of the natural salts via leaching. Both leached and natural GOM El were tested to investigate the influence of salinity on strength properties. CRS results show similar trends for each soil. Compressibility decreases and permeability increases significantly with increasing salinity. Increasing consolidation stresses to 40 MPa decreased the influence of salinity on compressibility to negligible levels while stress dependent permeability behavior varied amongst the soils tested. Significant decreases in both normalized undrained shear strength and critical state friction angle of GOM El with increasing stress level were observed, corresponding with an increase in the value of KO. An increase in shear strength and critical state friction angle was observed with increasing salinity at a consolidation stress of 0.4 MPa. No definitive trend was evident between the strength properties of leached and natural GOM El. The strength behavior of GOM El is consistent with that observed for other materials from a wide variety of geologic backgrounds and is in agreement with correlations between critical state friction angle and undrained strength to liquid limit.
by Brian Patrick Fahy.
S.M.
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LIN, CHING-JIE, et 林清傑. « Effect of high electrical conductivity and sodium adsorption ratio irrigation water on soil salinity and rice yields ». Thesis, 1992. http://ndltd.ncl.edu.tw/handle/08170057322177943754.
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Bellabarba, Agnese. « Into the wild : how rhizobia compete and survive in the early stage of symbiosis ». Doctoral thesis, 2022. http://hdl.handle.net/2158/1280999.
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Associations between leguminous plants and symbiotic nitrogen-fixing bacteria (rhizobia) are a classic example of mutualism between a eukaryotic host and a specific group of prokaryotic microbes. Rhizobia improve plant yield furnishing fixed nitrogen; therefore, they are highly used as inoculants, especially in sustainable agriculture. Though this association is species-specific, legume roots are exposed to heterogeneous rhizobial populations where different compatible strains are present and, could be infected by more than one strain. It is known that within the same rhizobial species different strains may have different competition capabilities, but detailed analyses able to predict the rhizobial competitive phenotype based exclusively on their genome are still lacking. In this thesis, we performed a bacterial genome-wide association analysis (GWAS) to define which genetic traits are responsible for an improved competitive phenotype in the model species Sinorhizobium meliloti. A panel of thirteen S. meliloti strains, whose genome is completely sequenced, has been selected and tested against three S. meliloti reference competitor strains (Rm1021, AK83 and BL225C) in a Medicago sativa nodule occupancy test. The measure of competition phenotypes previously obtained in the competition tests, in combination with strains genomic sequences of strains tested, were used to build-up a k-mer-based statistical models for each set of competition experiments. The obtained models were then applied to evaluate the accuracy in predicting the competition abilities of strains in the three competition patterns (vsRm1021, vsAK83 and vsBL225C). The competitive abilities of S. meliloti strains against two partners, BL225C and Rm1021, were well predict by the predictive models, as shown by the coefficient of determination R2 (equal to 0.96 and 0.84, respectively). Four strains showing the highest competition phenotypes (> 60% single strain nodule occupancy; GR4, KH35c, KH46 and SM11) versus BL225C were used to identify k-mers associated with the competition phenotype. The most significantly associated k-mers (p <0.05) were mapped on the genomic sequences of the S. meliloti strains used. Most of the k-mers were located on the symbiosis-related megaplasmid pSymA and on genes coding for transporters, proteins involved in the biosynthesis of cofactors and proteins related to metabolism (i.e. glycerol, fatty acids) suggesting that competition abilities reside in multiple genetic determinants comprising several cellular components. The identification of the best rhizobial inoculants in two new effective breeding lines of pea (Pisum sativum) used in Lithuania (DS 3637-2 and DS 3795-3) was also investigated. Six rhizobial strains, isolated from pea plants, which could be used as potential inoculants, were phylogenetically identified and extensive phenotypically characterized by Phenotype Microarray. All the strains belonged to the Rhizobium leguminosarum group, and were subdivided into three groups related to Rhizobium anhuiense, Rhizobium leguminosarum bv. viciae and R. sophorae/R. laguerreae. Differences observed with Phenotype microarray were linked to different phylogeny of the strains. In terms of symbiotic efficiency, six strains showed different symbiotic performances depending on the breeding line used. In particular, Rhizobium anhuiense strain Z1 (the reference strain) and Rhizobium leguminosarum bv. viciae 14ZE were the best symbiotic inoculants with breeding lines DS 3637-2 and DS 3795-3, respectively.
Livres sur le sujet "High-salinity soil"
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Dasgupta, Susmita, Md Moqbul Hossain, Mainul Huq et David Wheeler. Climate Change, Soil Salinity, and the Economics of High-Yield Rice Production in Coastal Bangladesh. The World Bank, 2014. http://dx.doi.org/10.1596/1813-9450-7140.
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Masoom, A. A. Al, et Helmut Lieth. Towards the Rational Use of High Salinity Tolerant Plants : Vol 2 : Agriculture and Forestry under Marginal Soil Water Conditions. Springer, 2012.
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Masoom, A. A. Al, et Helmut Lieth. Towards the Rational Use of High Salinity Tolerant Plants : Vol 2 : Agriculture and Forestry under Marginal Soil Water Conditions. Springer Netherlands, 2012.
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Aldous, David E., et Ian H. Chivers. Sports Turf and Amenity Grasses. CSIRO Publishing, 2002. http://dx.doi.org/10.1071/9780643090019.
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Sports Turf and Amenity Grasses is a comprehensive reference for anyone involved with the selection and maintenance of grasses used in sports and amenity areas in all areas. It provides a means to identify these grasses through keys, descriptions and photographs, and also provides detailed information on sowing, oversowing, stolonising and mowing heights.
The performance of each grass is assessed and detailed comments made on positive and negative aspects of its use. A grass’s tolerance to high temperature, frost, drought, shade, wet soil, salinity, low soil fertility, wear and close mowing is given in a table with each aspect rated. Further comments are made on how well it combines with particular grasses and on issues such as seedling vigour and sowing times.
Chapitres de livres sur le sujet "High-salinity soil"
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Oster, J. D. « Sodic soil reclamation ». Dans Towards the rational use of high salinity tolerant plants, 485–90. Dordrecht : Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1858-3_51.
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Ragab, M. « Distribution pattern of soil microbial population in salt-affected soils ». Dans Towards the rational use of high salinity tolerant plants, 467–72. Dordrecht : Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1858-3_48.
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Hamid, M. Wagdi Abdel, A. A. Shiha, E. E. Kaoud et S. M. Metwally. « Effect of soil management on some physical and chemical properties of salt-affected soil ». Dans Towards the rational use of high salinity tolerant plants, 399–405. Dordrecht : Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1860-6_46.
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El-Mougith, Abdo Ahmed. « The effect of salinity on some halophilic soil fungi ». Dans Towards the rational use of high salinity tolerant plants, 473–77. Dordrecht : Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1858-3_49.
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Wagdi Abdel Hamid, M., A. A. Shiha, S. A. Hammad et S. M. Metwally. « Effect of soil management on the NPK uptake and rice production in saline-alkali soil at Sharkia Governorate ». Dans Towards the rational use of high salinity tolerant plants, 139–46. Dordrecht : Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1860-6_17.
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Ogino, Kazuhiko. « Mangrove ecosystem as soil, water and plant interactive system ». Dans Towards the rational use of high salinity tolerant plants, 135–43. Dordrecht : Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1858-3_13.
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Jayasekera, R., et H. Lieth. « Soil aeration as an ecological factor governing mangrove zonation ». Dans Towards the rational use of high salinity tolerant plants, 231–36. Dordrecht : Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1858-3_24.
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Letey, J. « Soil characteristics and irrigation management for use in highly saline waters ». Dans Towards the rational use of high salinity tolerant plants, 439–43. Dordrecht : Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1860-6_50.
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El-Hyatemy, Y., A. A. Younis, A. H. Belal et A. M. Rammah. « Chemical analysis of Atriplex species grown at Nubaria in a calcareous soil ». Dans Towards the rational use of high salinity tolerant plants, 261–63. Dordrecht : Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1858-3_29.
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Omran, M. S., N. A. Bayoumi, M. A. Negm et S. Y. Montasser. « Effect of irrigation water quality on wheat grown on a calcareous soil ». Dans Towards the rational use of high salinity tolerant plants, 107–14. Dordrecht : Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1860-6_12.
Texte intégralActes de conférences sur le sujet "High-salinity soil"
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Sabia, Roberto, Adriano Camps, Christine Gommenginger et Meric Srokosz. « Retrieved sea surface salinity spatial variability using high resolution data within the soil moisture and ocean salinity (SMOS) mission ». Dans 2007 IEEE International Geoscience and Remote Sensing Symposium. IEEE, 2007. http://dx.doi.org/10.1109/igarss.2007.4423051.
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« Correlation of individual tree nut yield, evapotranspiration, tree stem water potential, total soil salinity and chloride in a high production almond orchard ». Dans 2014 ASABE Annual International Meeting. American Society of Agricultural and Biological Engineers, 2014. http://dx.doi.org/10.13031/aim.20141912431.
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Sambuu, Anna, B. Mongush et Sh Mongush. « NATURAL AND ANTHROPOGENIC DEGRADATION PROCESSES DESERTED STEPPES OF THE UBSUNUR BASIN ». Dans Land Degradation and Desertification : Problems of Sustainable Land Management and Adaptation. LLC MAKS Press, 2020. http://dx.doi.org/10.29003/m1717.978-5-317-06490-7/240-244.
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Steppes in Tuva occupy intermountain basins with altitudes of 550-1200 m above sea level, the lower parts of mountain slopes, and high terraces of river valleys. Large massifs of steppes are typical for the Ulugh-Khem and Ubsunur basins. Studies to assess the state of soil and vegetation cover were conducted in the North-Eastern (Tuva) part of the drainless Ubsunur basin in July-August 1997-2020 using the route method. The location of the basin between the boreal landscapes of Siberia and the desert-steppe landscapes of Central Asia is characterized by a variety of landforms, heterogeneity of soil and vegetation cover, and a unique distribution of climatic factors and geological history. The source material was our own data from soil and geobotanical studies and remote materials from different observation periods. Observation data from different survey years were linked to the Landsat satellite image for July-August 1997-2019. Route studies were carried out on the main geomorphological profiles from the southern foothills of the Western and Eastern Tannu-Ola ranges to the coast of oz. Ubsa-Nur (from North to South). Reference soil sections were laid at key sites, morphological descriptions of soil profiles and horizon-based sampling were carried out. Soil samples were taken to determine the humus content, granulometric composition, size and nature of salinity-the main indicators of soil desertification. Observations also covered the Eastern and Western parts of the basin, which revealed the direction of degradation of desolate steppes in different geomorphological positions of the territory, but also with different nature and intensity of anthropogenic impact.
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Deuel, L. E., et G. H. Holliday. « Evolution of Oil and Gas Waste/Soil Remediation Regulations ». Dans ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-80460.
Texte intégralRésumé :
The meaningful United States regulation of onshore oil and gas field waste/soil commenced in the mid 1980’s in response to a series of state, federal, industry and international initiatives. Most initiatives centered on the design, construction and operation of earthen pits used in the exploration and production of oil and gas (E&P). Prior to this time, earthen pits were constructed as needed by the operator and used in all phases of E&P activity. Chief concerns of the regulators were focused on what had gone into pits historically, what was going into them currently and was the E&P exemption excluding high volume E&P wastes from the Resource Conservation and Recovery Act (RCRA) regulations justified. Several investigations, including the comprehensive field study by the Environmental Protection Agency in 1987, determined E&P wastes are ostensibly non-hazardous. EPA concluded regulation of E&P wastes under RCRA Subtitle C was not necessary. To this day there is no U. S. federal regulatory program with exclusive jurisdiction over exempt E&P wastes. Other studies, primarily industry and academic, focusing on land limiting constituents, management practices and pit closure strategies revealed sodium salts and petroleum hydrocarbon in the form of diesel range organics were the primary limiting constituents. One state, Louisiana, adopted the technical aspects of these studies and developed a comprehensive regulation known as Statewide Order 29-B, which was based on the concept of limiting constituents and defined post closure performance standards. These standards limited salinity, sodicity, total metals and total petroleum hydrocarbon (oil & grease) with values varying with respect to landform, land use and closure technique. Other states have adopted some of the concepts and criteria advanced under 29-B but none are as comprehensive. Obviously there is a need to control what goes into pits and how pits should be closed. The industry would best be served by adopting the concepts and standards set forth in the Louisiana 29-B regulation. A few of the provisions could be changed to make it more palatable to industry without sacrificing the protection afforded human and animal health, safety and the environment. Internationally, particularly countries in South America embraced USEPA protocol for testing characteristically hazardous wastes, but 1) without the framework to handle the relatively large volume of non-hazardous E&P waste generated and 2) no regulations or protocols for on-site waste management. Several operators, although partners with state owned oil companies, on their own volition, applied the concepts and standards under Louisiana’s 29-B to rainforests in South America and rice paddies in Indonesia. Canada and European oil and gas producing countries have developed stringent standards not based on science, which favor costly treatment technologies. Generally, these countries prohibit cost effective on-site waste management and closure techniques. This paper traces the evolution of waste/soil remediation within the United States and internationally. We trace the progress as a function of time; the impetus for regulation; and probable future controls.
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Muntyan, Victoria S., Alla S. Saksaganskaia, Alexey N. Muntyan, Mariia E. Vladimirova et Marina L. Roumiantseva. « STRESS AND IMMUNITY OF NODULE BACTERIA SINORHIZOBIUM MELILOTI : LOCALIZATION, POLYMORPHISM AND PHYLOGENY OF GENETIC DETERMINANTS ». Dans 22nd SGEM International Multidisciplinary Scientific GeoConference 2022. STEF92 Technology, 2022. http://dx.doi.org/10.5593/sgem2022/6.1/s25.15.
Texte intégralRésumé :
Sinorhizobium meliloti are agriculturally valuable species of soil bacteria that form nitrogen-fixing symbiosis with alfalfa plants. Global climate changes lead to an increase of agricultural areas subjected to salinity. Current knowledge about about high-salt stress impact on soil saprophitic root nodulated microsymbionts of legumes is weakly studied and rhizobia gene pool responsible for salt tolerance are fragment and far from clear. An increase of bacteria nonspecific resistance (immune status) to unfavorable stress factors can occur through the induction of defense mechanisms like restrictionmodification systems and CRISPR/cas systems which are aimed to protect bacteria cells from bacteriophages widespread in soil microbiome. The aim of this research was to evaluate the role of the megaplasmid pSymA in the formation of ecological genome of S. meliloti, which is related to stress tolerance and to determine the location of elements of adaptive immune systems protecting root nodule bacteria against external foreign DNA. The analysis was done on 11 genes, products of which involved in response to ion stress and synthesis of osmoprotectors. It was found that 6 out of 11 genes were found in the genomes of all analyzed S. meliloti strains, while it was not a case for other 5 genes. It was found that, unlike chromosome, megaplasmid I of S. meliloti accumulated copies of 4 from 5 genes, except kdpA gene, which is represented by a single copy and localized on megaplasmid I in all so far studied strains. It was predicted that closest phylogenetic relatives of genes whose products are involved in response to ion stress as well in synthesis of osmoprotectors are homologous genes of closely related S. medicae species. The exception was for betI2, for which the closest phylogenetic relative was homologous gene of Klebsiella pneumonia, and another exception is kdpA gene introduced onto megaplasmid-I from actinobacteria. Regarding elements of immune systems it was revealed that nonsymbiotic plasmids of S. meliloti harbored incomplete elements of RMS-I, -II, and - III systems, while the 4 complete RMS-IV systems were detected on a single plasmid. It was found out that corresponding methylases had similarities with similar enzymes detected in nitrogen-fixing strains of Agrobacterium tumefaciens, Mezorhizobium sp., Bradyrhizobium sp. CRISPR sequences were not detected on megaplasmid-I, while they were on chromosome, megaplasmid-II and on cryptic plasmids. So, it was concluded that megaplasmid-I of S. meliloti are enriched in copies of genes related to osmotic stress tolerance, but it role in immune status of rhizobia is requested further elucidation.
6
Regmi, Susan, et Ning Zhang. « Testing the Salinity Control Designs in Calcasieu Lake Using Hydrodynamic and Salinity Transport Models ». Dans ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-67767.
Texte intégralRésumé :
An in-house hydrodynamic and salinity transport model was used to test the performance of several salinity control designs in Calcasieu Lake, Louisiana. The 256 sq.km shallow water lake is located in southwest Louisiana, with a 5 mile waterway (Calcasieu Pass) connecting to the Gulf. The salt water in the lake comes from the Gulf due to daily high tide and due to storm surges. In the south west part of the lake, called West Cove, has unique flow circulations and has relatively high salinity concentration comparing to the other part of the lake. A deep Calcasieu Ship Channel is the eastern border of West Cove. The surrounding wetlands of West Cove are disappearing due to the salt water intrusion. The vegetation is dying due to the high salinity concentration, and the soils are eroded quickly without the surface vegetation. The design goal is to reduce the salinity concentration in West Cove without reducing too much flow. The proposed designs include installing a levee and flow and salinity control stations at the eastern border of West Cove separating the water body with Calcasieu Ship Channel. The optimal length and location of the levee and the flow control structure are the objectives of the research. The in-house code was used to simulate the hydrodynamics and salinity transport with the different designs. The results were used to show the effectiveness of the designs on reducing the average salinity concentration in the area and maintaining reasonable flow speed in and out of the area. In the implementation of the designs, the flow and salinity control stations were also included in the simulation. The main function of the stations is to block the salt water from the Gulf during high tide, and direct the fresh water from the north into the area during low tide. This action can keep maintain a single direction fresh water flow from north to south in order to keep salt water out of the system.
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K.H.I, Gamage, Wickramasinghe R.S.R et Gamage I.M.C. « Groundwater Quality Assessment in Anuradhapura for Domestic Purposes ». Dans 2nd International Conference on Agriculture, Food Security and Safety. iConferences (Pvt) Ltd, 2021. http://dx.doi.org/10.32789/agrofood.2021.1006.
Texte intégralRésumé :
The North central province plays the main agricultural role in Sri Lanka as a developing agricultural-based economy country in the world. Excessive amount of nitrate and fluoride in groundwater consumption is becoming a crucial issue on human health in Sri Lanka, especially in the North Central part of the country. Dental fluorosis and skeleton fluorosis are the major health impacts based on an excessive amount of fluoride as well as presumption on causing chronic kidney disease (CKD). Nitrogenous compounds in groundwater for drinking have been considered possible risk factors for oesophageal cancer and haemoglobinemia or blue baby syndrome. Human activities and natural processes have polluted groundwater. Having a lack of understanding of the actual need for fertilizer, farmers usually tend to apply the surplus amount, thus increasing nitrogen pollution. Accordingly, this research was conducted to deepen the understanding of the distribution of fluoride and nitrate in groundwater in the Anuradhapura area in terms of geological and anthropogenic influences on groundwater quality. Well water samples were collected from intensive agricultural activity areas in Anuradhapura. Physical and chemical parameters were analyzed to identify whether the higher nitrate and fluoride or any compound of a mixture of heavy metals such as cadmium and/ or arsenic is the actual cause for kidney and other health-related issues among the community. Water samples' pHs were in the range of 6.7-7.7. All the wells can be categorized as low salinity water. Turbidity average of 3.51 NTU range of 1-8 NTU was found to be mainly contributed by nitrate at the average of 28.725 mg/L and ranged from (22-131) mg/L of nitrate. In addition, fluorite was found high in Anuradhapura with an average of 0.6 mg/L and ranged from (0.4 - 1.7) mg/L. Sulphate level was also high with an average of 178mg/L and ranged from (58-505 mg/L). There was no significant effect of heavy metals such as cadmium, arsenic, iron, and copper concentrations which were below the permissible level of 0.01mg/L. The research clearly indicates the abundance of nitrate and fluoride in groundwater, especially in the dry zone. The major sources are fluoride-bearing minerals in bedrock and soil zone. In addition to that, the influence of agriculture which causes excessive nitrate levels in groundwater, is apparent, irrespective of climatic zones.
Rapports d'organisations sur le sujet "High-salinity soil"
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Miyamoto, Seiichi, et Rami Keren. Improving Efficiency of Reclamation of Sodium-Affected Soils. United States Department of Agriculture, décembre 2000. http://dx.doi.org/10.32747/2000.7570569.bard.
Texte intégralRésumé :
Sodium affected soils, along with salt-affected soils, are distributed widely in irrigated areas of the arid and semi-arid region of the world. Some of these soils can and must be reclaimed to meet the increasing demand for food, and existing irrigated lands must be managed to reduce salinization and alkalization associated with deteriorating irrigation water quality. This project was conducted for examining ways to reduce the use of chemical amendments and large quantities of leaching water for reclaiming sodic soils or for preventing soil sodification, We hypothesized that sodicity of calcareous soils irrigated with moderately sodic irrigation water can be controlled by maximizing dissolution of soil CaCO3. The work performed in Israel has shown that dissolution of CaCO3 can be enhanced by elevating the CO2 partial pressure in soils, and by increasing pore water velocity. The concentration of Ca in pore water was at an order of 1.5 mmolc L-1 at a CO2 partial pressure of 5 kPa, which is sufficient to maintain SAR below 4 at salinity of irrigation water of 0.5 dS m-1 or less. Incorporation of crop residue at a flesh weight of 100 Mg ha-1 reduced the exchangeable Na percentage from 19 to 5%, while it remained 14% without crop residue application These findings indicate a possibility of preventing soil sodification with appropriate crop rotation and residue management without chemical amendments, provided that soils remain permeable. In the case of highly sodic soils, dissolution of CaCO3 alone is usually insufficient to maintain soil permeability during initial leaching. We examined the effect of salinity and sodicity on water infiltration, then developed a way to estimate the amendments required on the basis of water infiltration and drainage characteristics, rather than the traditional idea of reducing the exchangeable Na percentage to a pre-fixed value. Initial indications from soil column and lysimeter study are that the proposed method provides realistic estimates of amendment requirements. We further hypothesized that cultivation of salt-tolerant plants with water of elevated salinity can enhance reclamation of severely Na-affected soils primarily through improved water infiltration and increased dissolution of CaCO3 through respiration. An outdoor lysimeter experiment using two saline sodic Entisols sodded with saltgrass for two seasons did not necessarily support this hypothesis. While there was an evidence of increased removal of the exchangeable Na originally present in the soils, the final salinity and sodicity measured were lowest without sod, and highest when sodded. High transpiration rates, coupled with low permeability and/or inadequate leaching seemed to have offset the potential benefits of increased CaCO3 dissolution and subsequent removal of exchangeable Na. Although vegetative means of reclaiming sodic soils had been reported to be effective in sandy soils with sufficient permeability, additional study is needed for its use in saline sodic soils under the high evaporative demand. The use of cool season grass after initial salt leaching with CaCl2 should be explored. Results obtained from this project have several potential applications, which include the use of crop residues for maintaining sodium balance, the use of CaCl2 for initial leaching of poorly permeable clayey sodic soils, and appraisal of sodicity effects, and appropriate rates and types of amendments required for reclamation
2
Dudley, Lynn M., Uri Shani et Moshe Shenker. Modeling Plant Response to Deficit Irrigation with Saline Water : Separating the Effects of Water and Salt Stress in the Root Uptake Function. United States Department of Agriculture, mars 2003. http://dx.doi.org/10.32747/2003.7586468.bard.
Texte intégralRésumé :
Standard salinity management theory, derived from blending thermodynamic and semi- empirical considerations leads to an erroneous perception regarding compensative interaction among salinity stress factors. The current approach treats matric and osmotic components of soil water potential separately and then combines their effects to compute overall response. With deficit water a severe yield decrease is expected under high salinity, yet little or no reduction is predicted for excess irrigation, irrespective of salinity level. Similarly, considerations of competition between chloride and nitrate ions have lead to compensation hypothesis and to application of excess nitrate under saline conditions. The premise of compensative interaction of growth factors behind present practices (that an increase in water application alleviates salinity stress) may result in collateral environmental damage. Over-irrigation resulting in salinization and elevated ground water threatens productivity on a global scale. Other repercussions include excessive application of nitrate to compensate for salinity, unwillingness to practice deficit irrigation with saline water, and under-utilization of marginal water. The objectives for the project were as follows: 1) To develop a database for model parameterization and validation by studying yield and transpiration response to water availability, excessive salinity and salt composition. 2) To modify the root sink terms of an existing mechanism-based model(s) of water flow, transpiration, crop yield, salt transport, and salt chemistry. 3) To develop conceptual and quantitative models of ion uptake that considers the soil solution concentration and composition. 4) To develop a conceptual and quantitative models of effects of NaCl and boron accumulation on yield and transpiration. 5) To add a user interface to the water flow, transpiration, crop yield, salt transport, chemistry model to make it easy for others to use. We conducted experiments in field plots and lysimeters to study biomass production and transpiration of com (Zeamays cv. Jubilee), melon (Cucumismelo subsp. melo cv. Galia), tomato (Lycopersiconesculentum Mill. cv. 5656), onion (Alliumcepa L. cv. HA 944), and date palms (Phoenix Dactylifera L. cv. Medjool) under salinity combined with water or with nitrate (growth promoters) or with boron (growth inhibitor). All factors ranged from levels not limiting to plant function to severe inhibition. For cases of combined salinity with water stress, or excess boron, we observed neither additive nor compensative effects on plant yield and transpiration. In fact, yield and transpiration at each combination of the various factors were primarily controlled by one of them, the most limiting factor to plant activity. We proposed a crop production model of the form Yr = min{gi(xi), where Yr = Yi ym-1 is relative yield,Ym is the maximum yield obtained in each experiment, Xi is an environmental factor, gi is a piecewise-linear response function, Yi is yield of a particular treatment. We selected a piecewise-linear approach because it highlights the irrigation level where the response to one factor ceases and a second factor begins. The production functions generate response "envelopes" containing possible yields with diagonal lines represent response to Xi alone and the lines parallel to the X-axis represent response to salinity alone. A multiplicative model was also derived approximating the limiting behaviour for incorporation in a hydrochemical model. The multiplicative model was selected because the response function was required to be continuous. The hydrochemical model was a better predictor of field-measured water content and salt profiles than models based on an additive and compensative model of crop response to salinity and water stress.
3
Warrick, Arthur W., Gideon Oron, Mary M. Poulton, Rony Wallach et Alex Furman. Multi-Dimensional Infiltration and Distribution of Water of Different Qualities and Solutes Related Through Artificial Neural Networks. United States Department of Agriculture, janvier 2009. http://dx.doi.org/10.32747/2009.7695865.bard.
Texte intégralRésumé :
The project exploits the use of Artificial Neural Networks (ANN) to describe infiltration, water, and solute distribution in the soil during irrigation. It provides a method of simulating water and solute movement in the subsurface which, in principle, is different and has some advantages over the more common approach of numerical modeling of flow and transport equations. The five objectives were (i) Numerically develop a database for the prediction of water and solute distribution for irrigation; (ii) Develop predictive models using ANN; (iii) Develop an experimental (laboratory) database of water distribution with time; within a transparent flow cell by high resolution CCD video camera; (iv) Conduct field studies to provide basic data for developing and testing the ANN; and (v) Investigate the inclusion of water quality [salinity and organic matter (OM)] in an ANN model used for predicting infiltration and subsurface water distribution. A major accomplishment was the successful use of Moment Analysis (MA) to characterize “plumes of water” applied by various types of irrigation (including drip and gravity sources). The general idea is to describe the subsurface water patterns statistically in terms of only a few (often 3) parameters which can then be predicted by the ANN. It was shown that ellipses (in two dimensions) or ellipsoids (in three dimensions) can be depicted about the center of the plume. Any fraction of water added can be related to a ‘‘probability’’ curve relating the size of the ellipse (or ellipsoid) that contains that amount of water. The initial test of an ANN to predict the moments (and hence the water plume) was with numerically generated data for infiltration from surface and subsurface drip line and point sources in three contrasting soils. The underlying dataset consisted of 1,684,500 vectors (5 soils×5 discharge rates×3 initial conditions×1,123 nodes×20 print times) where each vector had eleven elements consisting of initial water content, hydraulic properties of the soil, flow rate, time and space coordinates. The output is an estimate of subsurface water distribution for essentially any soil property, initial condition or flow rate from a drip source. Following the formal development of the ANN, we have prepared a “user-friendly” version in a spreadsheet environment (in “Excel”). The input data are selected from appropriate values and the output is instantaneous resulting in a picture of the resulting water plume. The MA has also proven valuable, on its own merit, in the description of the flow in soil under laboratory conditions for both wettable and repellant soils. This includes non-Darcian flow examples and redistribution and well as infiltration. Field experiments were conducted in different agricultural fields and various water qualities in Israel. The obtained results will be the basis for the further ANN models development. Regions of high repellence were identified primarily under the canopy of various orchard crops, including citrus and persimmons. Also, increasing OM in the applied water lead to greater repellency. Major scientific implications are that the ANN offers an alternative to conventional flow and transport modeling and that MA is a powerful technique for describing the subsurface water distributions for normal (wettable) and repellant soil. Implications of the field measurements point to the special role of OM in affecting wettability, both from the irrigation water and from soil accumulation below canopies. Implications for agriculture are that a modified approach for drip system design should be adopted for open area crops and orchards, and taking into account the OM components both in the soil and in the applied waters.
4
Shani, Uri, Lynn Dudley, Alon Ben-Gal, Menachem Moshelion et Yajun Wu. Root Conductance, Root-soil Interface Water Potential, Water and Ion Channel Function, and Tissue Expression Profile as Affected by Environmental Conditions. United States Department of Agriculture, octobre 2007. http://dx.doi.org/10.32747/2007.7592119.bard.
Texte intégralRésumé :
Constraints on water resources and the environment necessitate more efficient use of water. The key to efficient management is an understanding of the physical and physiological processes occurring in the soil-root hydraulic continuum.While both soil and plant leaf water potentials are well understood, modeled and measured, the root-soil interface where actual uptake processes occur has not been sufficiently studied. The water potential at the root-soil interface (yᵣₒₒₜ), determined by environmental conditions and by soil and plant hydraulic properties, serves as a boundary value in soil and plant uptake equations. In this work, we propose to 1) refine and implement a method for measuring yᵣₒₒₜ; 2) measure yᵣₒₒₜ, water uptake and root hydraulic conductivity for wild type tomato and Arabidopsis under varied q, K⁺, Na⁺ and Cl⁻ levels in the root zone; 3) verify the role of MIPs and ion channels response to q, K⁺ and Na⁺ levels in Arabidopsis and tomato; 4) study the relationships between yᵣₒₒₜ and root hydraulic conductivity for various crops representing important botanical and agricultural species, under conditions of varying soil types, water contents and salinity; and 5) integrate the above to water uptake term(s) to be implemented in models. We have made significant progress toward establishing the efficacy of the emittensiometer and on the molecular biology studies. We have added an additional method for measuring ψᵣₒₒₜ. High-frequency water application through the water source while the plant emerges and becomes established encourages roots to develop towards and into the water source itself. The yᵣₒₒₜ and yₛₒᵢₗ values reflected wetting and drying processes in the rhizosphere and in the bulk soil. Thus, yᵣₒₒₜ can be manipulated by changing irrigation level and frequency. An important and surprising finding resulting from the current research is the obtained yᵣₒₒₜ value. The yᵣₒₒₜ measured using the three different methods: emittensiometer, micro-tensiometer and MRI imaging in both sunflower, tomato and corn plants fell in the same range and were higher by one to three orders of magnitude from the values of -600 to -15,000 cm suggested in the literature. We have added additional information on the regulation of aquaporins and transporters at the transcript and protein levels, particularly under stress. Our preliminary results show that overexpression of one aquaporin gene in tomato dramatically increases its transpiration level (unpublished results). Based on this information, we started screening mutants for other aquaporin genes. During the feasibility testing year, we identified homozygous mutants for eight aquaporin genes, including six mutants for five of the PIP2 genes. Including the homozygous mutants directly available at the ABRC seed stock center, we now have mutants for 11 of the 19 aquaporin genes of interest. Currently, we are screening mutants for other aquaporin genes and ion transporter genes. Understanding plant water uptake under stress is essential for the further advancement of molecular plant stress tolerance work as well as for efficient use of water in agriculture. Virtually all of Israel’s agriculture and about 40% of US agriculture is made possible by irrigation. Both countries face increasing risk of water shortages as urban requirements grow. Both countries will have to find methods of protecting the soil resource while conserving water resources—goals that appear to be in direct conflict. The climate-plant-soil-water system is nonlinear with many feedback mechanisms. Conceptual plant uptake and growth models and mechanism-based computer-simulation models will be valuable tools in developing irrigation regimes and methods that maximize the efficiency of agricultural water. This proposal will contribute to the development of these models by providing critical information on water extraction by the plant that will result in improved predictions of both water requirements and crop yields. Plant water use and plant response to environmental conditions cannot possibly be understood by using the tools and language of a single scientific discipline. This proposal links the disciplines of soil physics and soil physical chemistry with plant physiology and molecular biology in order to correctly treat and understand the soil-plant interface in terms of integrated comprehension. Results from the project will contribute to a mechanistic understanding of the SPAC and will inspire continued multidisciplinary research.
5
Crowley, David E., Dror Minz et Yitzhak Hadar. Shaping Plant Beneficial Rhizosphere Communities. United States Department of Agriculture, juillet 2013. http://dx.doi.org/10.32747/2013.7594387.bard.
Texte intégralRésumé :
PGPR bacteria include taxonomically diverse bacterial species that function for improving plant mineral nutrition, stress tolerance, and disease suppression. A number of PGPR are being developed and commercialized as soil and seed inoculants, but to date, their interactions with resident bacterial populations are still poorly understood, and-almost nothing is known about the effects of soil management practices on their population size and activities. To this end, the original objectives of this research project were: 1) To examine microbial community interactions with plant-growth-promoting rhizobacteria (PGPR) and their plant hosts. 2) To explore the factors that affect PGPR population size and activity on plant root surfaces. In our original proposal, we initially prqposed the use oflow-resolution methods mainly involving the use of PCR-DGGE and PLFA profiles of community structure. However, early in the project we recognized that the methods for studying soil microbial communities were undergoing an exponential leap forward to much more high resolution methods using high-throughput sequencing. The application of these methods for studies on rhizosphere ecology thus became a central theme in these research project. Other related research by the US team focused on identifying PGPR bacterial strains and examining their effective population si~es that are required to enhance plant growth and on developing a simulation model that examines the process of root colonization. As summarized in the following report, we characterized the rhizosphere microbiome of four host plant species to determine the impact of the host (host signature effect) on resident versus active communities. Results of our studies showed a distinct plant host specific signature among wheat, maize, tomato and cucumber, based on the following three parameters: (I) each plant promoted the activity of a unique suite of soil bacterial populations; (2) significant variations were observed in the number and the degree of dominance of active populations; and (3)the level of contribution of active (rRNA-based) populations to the resident (DNA-based) community profiles. In the rhizoplane of all four plants a significant reduction of diversity was observed, relative to the bulk soil. Moreover, an increase in DNA-RNA correspondence indicated higher representation of active bacterial populations in the residing rhizoplane community. This research demonstrates that the host plant determines the bacterial community composition in its immediate vicinity, especially with respect to the active populations. Based on the studies from the US team, we suggest that the effective population size PGPR should be maintained at approximately 105 cells per gram of rhizosphere soil in the zone of elongation to obtain plant growth promotion effects, but emphasize that it is critical to also consider differences in the activity based on DNA-RNA correspondence. The results ofthis research provide fundamental new insight into the composition ofthe bacterial communities associated with plant roots, and the factors that affect their abundance and activity on root surfaces. Virtually all PGPR are multifunctional and may be expected to have diverse levels of activity with respect to production of plant growth hormones (regulation of root growth and architecture), suppression of stress ethylene (increased tolerance to drought and salinity), production of siderophores and antibiotics (disease suppression), and solubilization of phosphorus. The application of transcriptome methods pioneered in our research will ultimately lead to better understanding of how management practices such as use of compost and soil inoculants can be used to improve plant yields, stress tolerance, and disease resistance. As we look to the future, the use of metagenomic techniques combined with quantitative methods including microarrays, and quantitative peR methods that target specific genes should allow us to better classify, monitor, and manage the plant rhizosphere to improve crop yields in agricultural ecosystems. In addition, expression of several genes in rhizospheres of both cucumber and whet roots were identified, including mostly housekeeping genes. Denitrification, chemotaxis and motility genes were preferentially expressed in wheat while in cucumber roots bacterial genes involved in catalase, a large set of polysaccharide degradation and assimilatory sulfate reduction genes were preferentially expressed.
6
Cohen, Roni, Kevin Crosby, Menahem Edelstein, John Jifon, Beny Aloni, Nurit Katzir, Haim Nerson et Daniel Leskovar. Grafting as a strategy for disease and stress management in muskmelon production. United States Department of Agriculture, janvier 2004. http://dx.doi.org/10.32747/2004.7613874.bard.
Texte intégralRésumé :
The overall objective of this research was to elucidate the horticultural, pathological, physiological and molecular factors impacting melon varieties (scion) grafted onto M. cannonballus resistant melon and squash rootstocks. Specific objectives were- to compare the performance of resistant melon germplasm (grafted and non-grafted) when exposed to M. cannoballus in the Lower Rio Grande valley and the Wintergarden, Texas, and in the Arava valley, Israel; to address inter-species relationships between a Monosporascus resistant melon rootstock and susceptible melon scions in terms of fruit-set, fruit quality and yield; to study the factors which determine the compatibility between the rootstock and the scion in melon; to compare the responses of graft unions of differing compatibilities under disease stress, high temperatures, deficit irrigation, and salinity stress; and to investigate the effect of rootstock on stress related gene expression in the scion. Some revisions were- to include watermelon in the Texas investigations since it is much more economically important to the state, and also to evaluate additional vine decline pathogens Didymella bryoniae and Macrophomina phaseolina. Current strategies for managing vine decline rely heavily on soil fumigation with methyl bromide, but restrictions on its use have increased the need for alternative management strategies. Grafting of commercial melon varieties onto resistant rootstocks with vigorous root systems is an alternative to methyl bromide for Monosporascus root rot/vine decline (MRR/VD) management in melon production. Extensive selection and breeding has already produced potential melon rootstock lines with vigorous root systems and disease resistance. Melons can also be grafted onto Cucurbita spp., providing nonspecific but efficient protection from a wide range of soil-borne diseases and against some abiotic stresses, but compatibility between the scion and the rootstock can be problematic. During the first year experiments to evaluate resistance to the vine decline pathogens Monosporascus cannonballus, Didymella bryoniae, and Macrophomina phaseolina in melon and squash rootstocks proved the efficacy of these grafted plants in improving yield and quality. Sugars and fruit size were better in grafted versus non-grafted plants in both Texas and Israel. Two melons (1207 and 124104) and one pumpkin, Tetsukabuto, were identified as the best candidate rootstocks in Texas field trials, while in Israel, the pumpkin rootstock RS59 performed best. Additionally, three hybrid melon rootstocks demonstrated excellent resistance to both M. cannonballus and D. bryoniae in inoculated tests, suggesting that further screening for fruit quality and yield should be conducted. Experiments with ABA in Uvalde demonstrated a significant increase in drought stress tolerance and concurrent reduction in transplant shock due to reduced transpiration for ‘Caravelle’ plants. In Israel, auxin was implicated in reducing root development and contributing to increased hydrogen peroxide, which may explain incompatibility reactions with some squash rootstocks. However, trellised plants responded favorably to auxin (NAA) application at the time of fruit development. Gene expression analyses in Israel identified several cDNAs which may code for phloem related proteins, cyclins or other factors which impact the graft compatibility. Manipulation of these genes by transformation or traditional breeding may lead to improved rootstock cultivars. Commercial applications of the new melon rootstocks as well as the ABA and TIBA growth regulators have potential to improve the success of grafted melons in both Israel and Texas. The disease resistance, fruit quality and yield data generated by the field trials will help producers in both locations to decide what rootstock/scion combinations will be best.