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Zeitschriftenartikel zum Thema "Soils South Australia Nitrogen content"
1
Lewis, DC, und LA Sparrow. „Implications of soil type, pasture composition and mineral content of pasture components for the incidence of grass tetany in the South East of South Australia“. Australian Journal of Experimental Agriculture 31, Nr. 5 (1991): 609. http://dx.doi.org/10.1071/ea9910609.
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The occurrence of grass tetany related deaths in cattle grazing pasture in the South East of South Australia is related to soil type. The greatest losses occur on the solodised solonetz soils, with few, if any, on the rendzina or siliceous sand soils in the region. Pastures from 3 soil types were sampled on 2 occasions during the growing period, and soils were sampled once. Comparisons were made for the pasture components of potassium (K), calcium (Ca) and magnesium (Mg) concentrations in soils, and K, Ca, Mg, nitrogen (N) and sulfur (S) concentrations in plants. In the July sampling, the mean herbage K/(Ca + Mg) ratio for both annual and perennial grass species grown on the solodised solonetz soils exceeded 2.2 but was below 2 for the other 2 soil types. At the same time the mean K/(Ca + Mg) ratio for soil-extractable cations was 0.10 for the solodised solonetz soils but only 0.058 and 0.025 for the rendzina and siliceous sand soils. A critical value for the K/(Ca + Mg) ratio for the soil extractable cations of 0.07-0.08 is suggested. Of the 22 sites in the investigation, grass tetany deaths had occurred on 9 within the previous 5 years; all of these were classified as solodised solonetz soils. Deaths were reported in late autumn and winter, and in all cases the dominant pasture species growing at these sites in July were grasses. It is suggested that deaths ceased in spring because there was either a change to legume dominance or an increase in air temperature.
2
O'Sullivan, Cathryn A., Steven A. Wakelin, Ian R. P. Fillery und Margaret M. Roper. „Factors affecting ammonia-oxidising microorganisms and potential nitrification rates in southern Australian agricultural soils“. Soil Research 51, Nr. 3 (2013): 240. http://dx.doi.org/10.1071/sr13039.
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Ammonia-oxidising archaea (AOA) have recently been described as having an important role in soil nitrification. However, published data on factors which influence their distribution and their impact on a soil’s potential nitrification rates (PNR) are sparse, particularly compared with the amount of information available regarding ammonia-oxidising bacteria (AOB). This study had two aims. First, to investigate which environmental factors affect the AOA : AOB ratio in soils from two agricultural regions, and second, to explore whether the abundance of either AOA or AOB correlated with PNR. Samples were collected from 45 sites within the cropping regions of Western Australia and South Australia. Soils were tested for pH, NH4+/NO3–, organic carbon (C), total nitrogen (N), C : N ratio, PNR, and electrical conductivity. Climate data were obtained from the Queensland Climate Change Centre for Excellence SILO website. Abundances of AOA and AOB were measured using real-time PCR quantification of the gene encoding the ammonia monooxygenase enzyme (amoA). Multivariate statistical analysis was applied to assess correlations between PNR, soil properties, and abundance of AOA or AOB. In the majority samples AOA were present, but their abundance, and the AOA : AOB ratio, varied considerably between sites. Multivariate analysis showed that the distribution of AOA and AOB and the AOA : AOB ratio were strongly correlated with climatic and seasonal factors. Sites where samples were collected during dry, hot periods tended to be AOA-dominated, whereas samples collected during cool, wet periods tended to be AOB-dominated or have equal abundances of AOA and AOB. The PNRs were correlated with total N content, organic C content, and soil pH. There was no clear correlation between AOA or AOB and PNR. This study shows that both AOA and AOB are widespread in Western Australian and South Australian soils and their abundance and ratio are affected by climate and season. It also shows that PNR is more strongly influenced by soil fertility factors than by the AOA : AOB ratio.
3
Latta, R. A., und A. Lyons. „The performance of lucerne - wheat rotations on Western Australian duplex soils“. Australian Journal of Agricultural Research 57, Nr. 3 (2006): 335. http://dx.doi.org/10.1071/ar04016.
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In field experiments on duplex soils in the south-eastern and central Western Australian wheatbelt, lucerne (Medicago sativa L.) was compared with subterranean clover (Trifolium subterraneum L.) in pasture–crop rotations. Comparative pasture plant densities and biomass, soil water content, available soil nitrogen, wheat grain yield, and protein content were measured during 2 and 3 years of pasture followed by 2 and 1 year of wheat, respectively. Lucerne densities declined by 60–90% over the 3-year pasture phase but produced up to 3 times more total annual biomass than weed-dominant annual pastures and similar total annual biomass when annual pastures were legume dominant. Lower soil water contents were measured under lucerne than under annual pastures from 6 months after establishment, with deficits up to 60 mm in the 0–1.6 m soil profile. However, significant rain events and volunteer perennial weeds periodically negated comparative deficits. Wheat yields were lower following lucerne (1.3 t/ha) than following an annual pasture (1.8 t/ha) in a low-rainfall season, higher (3.7 v. 2.9 t/ha) in a high-rainfall season, and much higher when the previous annual pastures were grass dominant (3.4 v. 1.5 t/ha). Grain protein contents were 1–2% higher in response to the lucerne pasture phase. Overcropping wheat into a lucerne pasture of 19 plants/m2 reduced wheat grain yields, but a lucerne density of 4 plants/m2 reduced yields only where rainfall was low. The study has shown that lucerne–wheat rotations provide a productive farming system option on duplex, sodic soils in both the south-eastern and central cropping regions of Western Australia. This was most evident in seasons of above-average summer and growing-season rainfall and when compared with grass-dominant annual pastures.
4
Angus, J. F., A. F. van Herwaarden, D. P. Heenan, R. A. Fischer und G. N. Howe. „The source of mineral nitrogen for cereals in south-eastern Australia“. Australian Journal of Agricultural Research 49, Nr. 3 (1998): 511. http://dx.doi.org/10.1071/a97125.
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The relative importance of soil mineral nitrogen (N) available at the time of sowing ormineralised during the growing season was investigated for 6 crops of dryland wheat. The soil mineral N in the root-zone was sampled at sowing and maturity and the rate of net mineralisation in the top 10 cm was estimated by sequential sampling throughout the growing season, using an in situ method. Mineralisation during crop growth was modelled in relation to total soil N, ambient temperature, andsoil water content. Mineral N accumulated before sowing varied by a factor of 3 between the sites (from 67 to 195 kgN/ha), while the net mineralisation during crop growth varied by a factor of 2 (from 43 to 99 kgN/ha). The model indicated that 0·092% of total N was mineralised per day when temperature and water were not limiting, with rates decreasing for lower temperatures and soil water contents. When tested with independent data, the model predicted the mineralisation rate of soil growing continuous wheat crops but underestimated mineralisation of soil in a clover-wheat rotation. For crops yielding <3 t/ha, the supply of N was mostly from mineralisation during crop growth and the contribution from mineral N accumulated before sowing was relatively small. For crops yielding >4 t/ha, thesupply of N was mostly from N present in the soil at the time of sowing. The implication is that for crops to achieve their water-limited yield, they must be supplied with an amount of N greater than can be expected from mineralisation during the growing season, either from fertiliser or from mineral N accumulated earlier.
5
Lewis, DC, TD Potter, SE Weckert und IL Grant. „Effect of nitrogen and phosphorus fertilizers on the seed yield and oil concentration of oilseed rape (Brassica napus L.) and the prediction of responses by soil tests and past paddock use“. Australian Journal of Experimental Agriculture 27, Nr. 5 (1987): 713. http://dx.doi.org/10.1071/ea9870713.
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The response of oilseed rape to applied nitrogen and phosphorus was investigated in 2 areas of the South East of South Australia. The nitrogen rates applied varied from 0 to 50 kg/ha, while phosphorus rates applied in the Mundulla area ranged from 0 to 20 kg/ha and 0 to 34 kg/ha in the Millicent area. At 9 sites in the Mundulla area, where soils were primarily sandy loam over clay, oilseed rape yields were increased significantly by applied nitrogen at 7 sites and by applied phosphorus at 2 sites. On heavy black clay and peat soils in the Millicent area, oilseed rape yields were increased significantly by applied nitrogen at 5 of the 12 sites and by applied phosphorus at 6 sites. Of the measured soil variables, anaerobic ammonium nitrogen measured in the top 10 cm best predicted responses in seed yield to applied nitrogen. The critical nutrient range was 45-65 mg/kg. The response of oilseed rape to applied nitrogen was highly correlated with past paddock use but varied between the 2 areas. From the prediction equations developed, it was concluded that, in the Mundulla area, a significant (P< 0.05) nitrogen response was likely if the oilseed rape followed 2 or more crops, the last a non-legume, but was unlikely if the oilseed rape followed 1 or more years of pasture. At Millicent, a nitrogen response was likely if the oilseed rape was grown as the sixth crop in a continuous cropping program, and was unlikely if it was the first or second crop in the rotation, provided the preceding crop was a non-legume. The response of oilseed rape to applied phosphorus was highly correlated to extractable soil phosphorus measured in the top 10 cm (Colwell). The critical nutrient range was 20-25 mg/kg for the sandy loam soils at Mundulla and 40-50 mg/kg for the black clay and peat soils at Millicent. Nitrogen applications significantly increased seed oil content at 6 sites, significantly decreased it at 2 sites and had no effect at 13 sites. Phosphorus significantly increased seed oil content at only 1 site, significantly decreased it at 3 sites, and had no effect at the other 17 sites.
6
Smiles, D. E., und C. J. Smith. „A survey of the cation content of piggery effluents and some consequences of their use to irrigate soils“. Soil Research 42, Nr. 2 (2004): 231. http://dx.doi.org/10.1071/sr03059.
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Piggery effluent contains high concentrations of potassium, and its repeated irrigation raises soil exchangeable potassium to levels, relative to divalent cations, that may degrade soil structure. We surveyed 6 big piggeries extending from south-eastern Queensland on a self-mulching Vertosol, to an Arenic Rudosol in south-eastern South Australia. We sampled effluent used for irrigation and also soil profiles to permit 'fenceline' comparisons between soils that had and had not been irrigated. The major water-soluble cations sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+) were measured in the effluent and the soil saturation extracts, and also their exchangeable forms on air-dried soil samples. Ammonium-nitrogen (NH4+-N) was also assayed. The effluents were similar, with pH values between 7.5 and 8 together with very high water-soluble NH4-N, lower values for K+ and Na+, and quite low concentrations of Ca2+ and Mg2+. Cation concentrations varied across effluents; sodium and potassium adsorption ratios (SAR and KAR) were relatively constant but smaller than an ammonium adsorption ratio (Am-AR), which we conceive to estimate the influence of NH4+-N relative to the divalent cations in the effluent. Exchangeable K+ ratios in all profiles that had been irrigated were greater than their non-irrigated partners, as were the KAR values in their saturation extracts. Despite high concentrations of NH4+-N and high values of Am-AR in the effluents, there was no evidence of exchangeable NH4+ in the soils when sampled, which, we presume, is rapidly taken up by plants or oxidised. We present data that support a useful relationship between total cation content and effluent and the soil saturation extract electrical conductivity (EC), We also observed a modest increase in the EC of the saturation extract of irrigated soils. Farm records were insufficient to permit material balance calculations.
7
Bauhus, J., PK Khanna und RJ Raison. „The effect of fire on carbon and nitrogen mineralization and nitrification in an Australian forest soil“. Soil Research 31, Nr. 5 (1993): 621. http://dx.doi.org/10.1071/sr9930621.
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The causes of onset of nitrification in a soil collected under an ashbed which was produced when heaped slash was burned, and for its absence in an unburnt soil, were investigated for an acid forest soil from south-eastern Australia. The occurrence of nitrification in ashbed soils was assessed in laboratory incubations extendig to 151 days to determine if it could be attributed to (a) an increase in pH, (b) an additional supply of P, (c) the removal of chemical inhibitors, and (d) the lack of competition with heterotrophs killed during soil heating. The treatments were: percolated and unpercolated ashbed soil from 0-5 and 5-10 cm depth; unburnt soil from 0-5 cm untreated and with added lime or added P; and burnt and unburnt soil from 5-10 cm depth. In addition, each treatment had an identical where the soil was inoculated with nitrifying garden soil. Compared with the unburnt surface soil (0-5 cm), ashbed soil had higher pH (3.6 units), higher mineral N (3 times) and slightly elevated NaHCO3-extractable P. During 151 days of incubation, microbial respiration in surface ashbed soil, measured as CO2 evolution, initially exceeded the values obtained in unburnt soil but then decreased to only 72% of unburnt soil at the end of the incubation period. In ashbed soil, the microbial biomass N content was low but its C/N ratio was high. Net N mineralization (Nmin) in ashbed soil was not significantly different from unburnt or phosphate fertilized soils (13.1, 14.7 and 17.8 mg N,in kg-' respectively) but was lower than in limed soil (59.3 mg Nmin kg-1). Percolation of surface ashbed soil with distilled water removed high amounts of salts and increased microbial respiration and N mineralization. Inoculation of soils with a slurry from a nitrifying garden soil induced nitrification in every treatment, regardless of their ammonium content, pH or other limiting component. Nitrification was also stimulated in unburnt surface soil on the addition of lime and P. Autotrophic nitriflers were active only in surface ashbed soils and probably in limed soils. P addition promoted heterotrophic nitrification. It was concluded that soil heating reduced competition between autotrophs and heterotrophs for ammonium and that ash supplies nutrients, such as K and Ca which stimulate nitrification. Low pH was not a limiting factor for nitrification but a high pH may promote the establishment of autotrophic nitrifiers.
8
Cooke, JW, GW Ford, RG Dumsday und ST Willatt. „Effect of fallowing practices on the growth and yield of wheat in south-eastern Australia“. Australian Journal of Experimental Agriculture 25, Nr. 3 (1985): 614. http://dx.doi.org/10.1071/ea9850614.
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The effects on crop establishment, crop development and the yield of wheat of two methods of fallow preparation, at each of three lengths of fallow were investigated over 5 years on red duplex and associated soils in north-central Victoria. The two methods of preparation were: scarifying, which involved the repeated use of a tined tillage implement; and herbicide application, which involved the repeated use of non-residual herbicides to control weeds during the fallow phase. The three lengths of fallow were winter, spring and autumn, which were approximately 10, 8 and 2 months respectively. Grain yield on the scarifier treatments was 0.26 t/ha greater (P<0.10) than on the herbicide treatments. Grain yield on winter fallow was 0.46 and 0.56 t/ha greater (Pt0.01) than on spring and autumn fallows, respectively. Crop yield was positively correlated (R2= 0.49) with soil nitrate determined at the time the crop was sown, but was independent of available soil water content determined at that time. Winter fallowing conserved 15 and 29 mm more water than did spring and autumn fallowing respectively, and mineralized 26 and 28 kg/ha more nitrogen than did spring and autumn fallows respectively. Crop establishment (No. of plants/m of row) on the herbicide treatment was 89% (P< 0.05) of that on the scarifier treatment, but this was not the reason for the reduced grain yield on the herbicide treatment. The lower yields were caused by depressed crop vigour (number of spikes/m of row) which in turn was largely a consequence of the inefficient uptake of nitrogen. The yield benefits of scarifying appear to reflect the importance of the initial two or three cultivations.
9
Pérez-Fernández, María A., und Byron B. Lamont. „Nodulation and performance of exotic and native legumes in Australian soils“. Australian Journal of Botany 51, Nr. 5 (2003): 543. http://dx.doi.org/10.1071/bt03053.
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Six Spanish legumes, Cytisus balansae, C. multiflorus, C. scoparius, C. striatus, Genista hystrix and Retama sphaerocarpa, were able to form effective nodules when grown in six south-western Australian soils. Soils and nodules were collected from beneath natural stands of six native Australian legumes, Jacksonia floribunda, Gompholobium tomentosum, Bossiaea aquifolium, Daviesia horrida, Gastrolobium spinosum and Templetonia retusa. Four combinations of soils and bacterial treatments were used as the soil treatments: sterile soil (S), sterile inoculated soils (SI), non-treated soil (N) and non-treated inoculated soils (NI). Seedlings of the Australian species were inoculated with rhizobia cultured from nodules of the same species, while seedlings of the Spanish species were inoculated with cultures from each of the Australian species. All Australian rhizobia infected all the Spanish species, suggesting a high degree of 'promiscuity' among the bacteria and plant species. The results from comparing six Spanish and six Australian species according to their biomass and total nitrogen in the presence (NI) or absence (S) of rhizobia showed that all species benefitted from nodulation (1.02–12.94 times), with R.�sphaerocarpa and C. striatus benefiting more than the native species. Inoculation (SI and NI) was just as effective as, or more effective than the non-treated soil (i.e. non-sterile) in inducing nodules. Nodules formed on the Spanish legumes were just as efficient at fixing N2 as were those formed on the Australian legumes. Inoculation was less effective than non-treated soil at increasing biomass but just as effective as the soil at increasing nitrogen content. Promiscuity in the legume–bacteria symbiosis should increase the ability of legumes to spread into new habitats throughout the world.
10
Chen, Wen, Graeme Blair, Jim Scott und Rod Lefroy. „Nitrogen and sulfur dynamics of contrasting grazed pastures“. Australian Journal of Agricultural Research 50, Nr. 8 (1999): 1381. http://dx.doi.org/10.1071/ar98104.
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The experimental area was located at the Big Ridge 2 site, CSIRO, Chiswick (30°31′S, 151°39′E), 20 km south of Armidale, New South Wales, Australia. The site was established in 1955. In March 1966, phalaris and white clover were sown and pastures were fertilised annually with superphosphate until 1993. There were 3 pasture treatments, each with 2 replicates: degraded pasture (low phalaris content), phalaris dominant, and phalaris–white clover. Each of 6 experimental plots was divided into 3 strata. Two representative areas 1 m by 0.5 m were selected in each stratum of each treatment. The selected areas were labelled with 34S-enriched (90%) elemental sulfur and 15N-enriched (99%) NH4Cl solution. All plots were grazed continuously by sheep. No effect of pasture type on N leaching was apparent in this experiment. Seasonal variation of total soil mineral N in different soil layers, low 15N recovery down to 60 cm soil depth, and low nitrate-N concentrations in drainage water obtained in this experiment suggest that synchronisation of pasture growth with mineralisation and nitrification, together with ammonium domination of the soil N system, is the key ecological feature in preventing N leaching in this environment. Unlike N, potential S leaching was found with evidence of a large amount of sulfate stored deeper in the soil profile and high S concentrations in drainage water. High KCl-40 extractable S concentration in the top 20 cm soil layers was associated with the long history of superphosphate application. Long-term applications of superphosphate (1967–93), together with an increase in sulfate sorption capacity at lower soil depths, resulted in a large amount of sulfate stored at greater depth. However, retention of the 34S applied in 1995 in the top 10 cm soils suggests that sulfate-S movement down the soil profile is slow.
Dissertationen zum Thema "Soils South Australia Nitrogen content"
1
Lotfollahi, Mohammad. „The effect of subsoil mineral nitrogen on grain protein concentration of wheat“. Title page, table of contents and summary only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phl882.pdf.
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Copy of author's previously published work inserted. Bibliography: leaves 147-189. This project examines the uptake of mineral N from the subsoil after anthesis and its effect on grain protein concentration (GPC) of wheat. The overall objective is to examine the importance of subsoil mineral N and to investigate the ability of wheat to take up N from the subsoil late in the season under different conditions of N supply and soil water availability. Greenhouse experiments investigate the importance of subsoil mineral N availability on GPC of wheat and the factors that contribute to the effective utilisation of N. The recovery of N from subsoil, the effect of split N application on GPC and short term N uptake by the wheat at different rooting densities are also studied.
2
Shrestha, Hari Ram. „Post-fire recovery of carbon and nitrogen in sub-alpine soils of South-eastern Australia /“. Connect to thesis, 2009. http://repository.unimelb.edu.au/10187/6963.
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The forests of south-eastern Australia, having evolved in one of the most fire-prone environments in the world, are characterized by many adaptations to recovery following burning. Thus forest ecosystems are characterized by rapid regenerative capacity, from either seed or re-sprouting, and mechanisms to recover nutrients volatilized, including an abundance of N2 fixing plants in natural assemblages. Soil physical, chemical and biological properties are directly altered during fire due to heating and oxidation of soil organic matter, and after fire due to changes in heat, light and moisture inputs. In natural ecosystems, carbon (C) and nitrogen (N) lost from soil due to fires are recovered through photosynthesis and biological N2 fixation (BNF) by regenerating vegetation and soil microbes.This study investigated post-fire recovery of soil C and N in four structurally different sub-alpine plant communities (grassland, heathland, Snowgum and Alpine ash) of south-eastern Australia which were extensively burnt by landscape-scale fires in 2003. The amount and isotopic concentration of C and N in soils to a depth of 20 cm from Alpine ash forest were assessed five years after fire in 2008 and results were integrated with measurements taken immediately prior to burning (2002) and annually afterwards.
Because the historical data set, comprised of three soil samplings over the years 2002 to 2005, consisted of soil total C and N values which were determined as an adjunct to 13C and 15N isotopic studies, it was necessary to establish the accuracy of these IRMS-derived measurements prior to further analysis of the dataset. Two well-established and robust methods for determining soil C (total C by LECO and oxidizable C by the Walkley-Black method) were compared with the IRMS total C measurement in a one-off sampling to establish equivalence prior to assembling a time-course change in soil C from immediately pre-fire to five years post-fire. The LECO and IRMS dry combustion measurements were essentially the same (r2 >0.99), while soil oxidizable C recovery by the Walkley-Black method (wet digestion) was 68% compared to the LECO/IRMS measurements of total C. Thus the total C measurement derived from the much smaller sample size (approximately 15 mg) combusted during IRMS are equivalent to LECO measurement which require about 150 mg of sample.
Both total C and N in the soil of Alpine ash forests were significantly higher than soils from Snowgum, heathland and grassland communities. The ratio of soil NH4+ to NO3- concentration was greater for Alpine ash forest and Snow gum woodland but both N-fractions were similar for heathland and grassland soils. The abundance of soil 15N and 13C was significantly depleted in Alpine ash but both isotopes were enriched in the heathland compared to the other ecosystems. Abundance of both 15N and 13C increased with soil depth.
The natural abundance of 15N and 13C in the foliage of a subset of non-N2 fixing and N2 fixing plants was measured as a guide to estimate BNF inputs. Foliage N concentration was significantly greater in N2 fixers than non-N2 fixers while C content and 13C abundance were similar in both functional groups. Abundance of 15N was depleted in the N2 fixing species but was not significantly different from the non-N2 fixers to confidently calculate BNF inputs based on the 15N abundance in the leaves.
The total C pool in soil (to 20 cm depth) had not yet returned to the pre-fire levels in 2008 and it was estimated that such levels of C would be reached in another 6-7 years (about 12 years after the fire). The C and N of soil organic matter were significantly enriched in 15N and 13C isotopes after fire and had not returned to the pre-fire levels five years after the fire. It is concluded that the soil organic N pool can recover faster than the total C pool after the fire in the Alpine ash forests.
3
Maqubela, Mfundo Phakama. „Bioconditioning and nitrogen fertility effects of selected cyanobacteria strains on two degraded soils in the Eastern Cape Province, South Africa“. Thesis, University of Fort Hare, 2009. http://hdl.handle.net/10353/558.
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Some cyanobacteria strains have biofertilization and bioconditioning effects in soils. The objective of this study was to identify cyanobacteria with potential to improve the N fertility and structural stability of degraded soils and evaluate their effectiveness in soils of the Eastern Cape, South Africa. Isolation and characterization of the indigenous cyanobacteria strains with desirable properties was first to be undertaken because their effects are known to differ from strain to strain. Cyanobacteria strains 3g, 3v, and 7e were identified from 97 strains isolated from selected soils. Nostoc strains 3g and 3v had greater ability to produce exocellular polysaccharides (EPS) but low potential to fix atmospheric N2 (4.7 and 1.3 nmol C2H4 μg chl-1 h-1, respectively). On the other hand, strain 7e had the highest capability to fix atmospheric N2 (16.1 nmol C2H4 μg chl-1 h-1) but had the least ability to produce EPS. Evaluation of the strains was done in glasshouse studies starting with Nostoc strain 9v isolated from a Tanzanian soil, followed by the indigenous strains isolated from soils in Hertzog and Qunu, South Africa. Inoculation was done by uniformly applying cyanobacteria on the surface of potted soils at a rate of 6 g m-2. First harvest and soil sampling took place after six weeks, and the top 25 mm of the soil was mixed, replanted, and sampled again after a further six weeks (second harvest). Inoculation with Nostoc strain 9v increased soil N by 40 percent and 17 percent in Guquka and Hertzog soils, respectively, and consequently increased maize dry matter yields by 40 and 49 percent. Soil C increased by 27 percent and 8 percent in Guquka and Hertzog soils, respectively, and this increase was significantly associated with that of soil N (R2 = 0.838). Higher contents of soil C, soil N and mineral N, however, were found in non-cropped soils. Scanning Electron Microscopy (SEM) revealed coatings of EPS on soil particles and fragments of non-cropped inoculated soils, with iii other particles enmeshed in networks of filaments, in contrast to cropped and/or non-inoculated soils. The proportion of very stable aggregates was increased by inoculation but cropping with maize reduced the aggregate stability. Inoculating Hertzog soil with indigenous strains 3g and 7e increased the nitrate N in the first cropping by 49 percent and 69 percent respectively, in cropped soils. In the second cropping increases in mineral N were 41 percent and 43 percent in 3g and 7e inoculated soils, respectively. Maize dry matter yields were higher on inoculated soils both in the first and second harvest in response to the improved N status of the soil. Increases in aggregate MWD in cropped soil as determined by fast wetting, mechanical breakdown and slow wetting were 85 percent, 33 percent, 33 percent, respectively, for 3g inoculation, 64 percent, 41 percent, and 41 percent, respectively, for 7e inoculation and 60 percent, 24 percent, 50 percent for inoculation with 9v. In non-cropped soil, increases in MWD as determined by fast wetting, mechanical breakdown and slow wetting were 11 percent, 0 percent, 7 percent, respectively for 3g inoculation, 21 percent, 11 percent, and 7 percent, respectively for 7e inoculation, and 25 percent, 36 percent, and 19 percent for strain 9v inoculation. Scanning electron microscopy observations, which were confirmed by chemical results, revealed that inoculated soils had high EPS and filaments that encouraged soil aggregation and improved aggregate stability. Results of this study show that cyanobacteria strains isolated and selected for their ability to fix atmospheric N2 and produce EPS improved the fertility status and aggregate stability of degraded soils from South Africa.
4
Bagheri, Kazemabad Abdolreza. „Boron tolerance in grain legumes with particular reference to the genetics of boron tolerance in peas“. Title page, summary and contents only, 1994. http://web4.library.adelaide.edu.au/theses/09PH/09phb144.pdf.
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5
Crawford, Michael Cameron. „Quantification of the belowground inputs of organic carbon by the annual pasture legume barrel medic (Medicago truncatula Gaertn.)“. Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phc8988.pdf.
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Bibliography: leaves 164-193. This study aims to quantify the belowground input of organic carbon by barrel medic using techniques that account for root death and decomposition as well as root secretion and exudation. It also investigates the effect of defoliation on carbon allocation within the plant so as to determine the potential for optimising carbon input to the soil through grazing management.
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George, Suman Jacob. „Effects of land-use change on phosphorus forms in South-West Australian soils“. University of Western Australia. School of Earth and Geographical Sciences, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0078.
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[Truncated abstract] Eleven sites, each with the trio of land uses: Eucalyptus globulus plantation, pasture and natural vegetation, representing from the Mediterranean climate, high rainfall region (<550 mm annually) of south-western Australia were investigated to assess medium-term changes in the P-supplying capacity of soils in eucalypt plantations growing on agricultural land. The natural vegetation soils were a benchmark for comparing soil P change since land clearing and development for agriculture. The experimental framework provided an ideal basis for studying changes in P forms since land clearing and fertilization for agriculture and the ensuing conversion to plantations (on an average 9 years ago). Conventional soil P indices measure plant available P that is more relevant to short duration annual crops and pastures. To predict medium-term P availability, P forms were determined using Hedley et al.’s (1982) fractionation scheme and fractions were grouped using the Guo and Youst (1998) criteria into readily, moderately and sparingly available P. The P species were also determined by 31P NMR spectroscopy of 0.5M NaOH-0.1M EDTA extracts. Hedley et al.’s (1982) inorganic P extracted by anion exchange resin and by NaHCO3 are widely considered to be approximations to the actual plant available P. The availability to plants of other P fractions is less certain and this is examined in an experiment to compare the plant availability of various P fractions in soils from fertilized and unfertilized land uses following exhaustive cropping in the glasshouse. The soil texture for the sites studied included coarse sand, loamy sand, clayey sand, and sandy loam. Surface soils (0-10 cm) have pH(CaCl2) in the acidic range (mean 4.4) and there is no significant difference due to differences in land use (P<0.05). The soils are of low EC (1:5 H2O) - 6 mS m-1. There is an almost 5-fold variation in organic C among sites (from 1.4% to 8%) but organic C values did not show any significant effect (P<0.05) of changes in land use. To evaluate the degree of similarity of soils within each triplet set at a site principal component analysis was carried out on those soil chemical⁄mineralogical characteristics that were least likely to be affected by changes in land use practices. This analysis showed good matching of the triplet of sub-sites on the whole, especially for the duo of pasture and plantation land uses. This degree of matching of the trio of land uses was considered while interpreting the effects of land use on the forms and behaviour of soil P, and variations due to various extents of mismatch were mostly addressed using statistical techniques including regression analysis to interpret sub-site difference
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Hoyle, Frances Carmen. „The effect of soluble organic carbon substrates, and environmental modulators on soil microbial function and diversity“. University of Western Australia. School of Earth and Geographical Sciences, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0050.
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[Truncated abstract] The principal aim of this thesis was to examine the response of the microbial community to the addition of small amounts (<50 μg C g-1 soil) of organic C substrates (‘trigger molecules’) to soil. This addition is comparative to indigenous soluble C concentrations for a range of soil types in Western Australia (typically measured between 20 and 55 μg C g-1 soil). Previously it has been reported that the application of trigger molecules to European soils has caused more CO2-C to be evolved (up to six fold) than was applied . . . Findings from this study indicated that there was an additional CO2 release (i.e. greater than the C added) on application of organic C substrates to some soil treatments. However, findings from this study indicate that the response of the microbial community to small additions of soluble C substrate is not consistent for all soil types and may vary due to greater availability of C, and supports the premise that microbial responses vary in a yet to be predicted manner between soil type and ecosystems. Differences in microbial response to the addition of soluble organic C are likely attributable to differences in soil attributes and environmental factors influencing both the diversity of microbes present and the frequency of food events. Theoretically, trigger molecules could also provide a possible control mechanism for microorganisms in arable farming systems. These mechanisms include stimulating either targeted pathogenic microorganisms that starve after depletion of a suitable substrate; or stimulating beneficial microorganisms to manipulate nutrient cycling, by targeting specific functional groups and altering mineralisation and immobilisation turnover rates.
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Huang, Chunyuan. „Mechanisms of Mn efficiency in barley“. 1996, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phh8739.pdf.
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Bibliography: leaves 131-153. This thesis investigates the mechanisms of manganese (Mn) efficiency (genetic tolerance to Mn-deficient soils) in barley (Hordeum vulgare L.) at both physiological and molecular levels.
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Lalor, Briony Maree. „An assessment of the recovery of the microbial community in jarrah forest soils after bauxite mining and prescription burning“. University of Western Australia. School of Earth and Geographical Sciences, 2009. http://theses.library.uwa.edu.au/adt-WU2010.0037.
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[Truncated abstract] Recovery of soil nutrients, microbial populations and carbon (C) and nitrogen (N) cycling processes are critical to the success of rehabilitation following major ecosystem disturbance. Bauxite mining represents a major ecosystem disturbance to the jarrah (Eucalyptus marginata) forest in the south-west of Western Australia. Mining has created a mosaic of mined areas in various stages of succession surrounded by non-mined forest areas. Initial site preparations within rehabilitation areas such as contour ripping alter soil structure (creation of mound and furrows) and over time also influence the distribution of vegetation and litter. Current performance criteria developed by industry, government and other stakeholders have determined that before post-bauxite mined areas of jarrah forest can be integrated back into normal forest management practises they should be functional and demonstrate resilience to normal forest disturbances such as fire. Furthermore, resilience should be of a manner comparable to non-mined analogue forest sites. Currently little is known of the resilience of microbial communities and C and N cycling in rehabilitation sites to normal forest disturbances such as prescription burning. As such, before rehabilitated jarrah forests can be successfully integrated into broad scale forest management regimes, a more thorough knowledge of the potential impacts of burning practises on the soil microbial community and C and N cycling processes in these systems is required. ... While there are similar rates of C and N cycling the underlying microbial community structure was distinctly different; implying a high degree of functional redundancy with respect to C and N cycling. Differences in the C and N cycling and structure of the microbial communities were likely to be due to differences in soil environmental conditions (i.e. soil alkalinity/acidity, soil moisture) and C substrate availability which influence the physiological status of the microbial community and in turn are related to successional age of the forests. Results also suggest that the measurement of CLPP can be a useful approach for assessment of changes in the functional ability of microbial communities. However, the interpretation of how well these rehabilitation forests have recovered heterotrophic abilities was greatly affected by the methodological approach used (e.g. MicroRespTM or Degens and Harris, 1997). Importantly, results from Chapter 4 and 5 suggested that the effects of a moderate prescription fire on C and N processes, CLPP and microbial community structure of 18 year old rehabilitation forests are likely to be short-lived (< 2 years). Furthermore, the effects of the moderate spring prescription fire were not large enough to decouple C and N cycling processes over the short-term (< 1 years) which suggests that by 18 years of age rehabilitation forests demonstrate comparable functional resilience to a moderate prescription burn.
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McLaughlin, Michael John. „Phosphorus cycling in soil under wheat-pasture rotations /“. Title page, contents and summary only, 1986. http://web4.library.adelaide.edu.au/theses/09PH/09phm1615.pdf.
Der volle Inhalt der QuelleBücher zum Thema "Soils South Australia Nitrogen content"
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International Symposium on "Manganese in Soils and Plants" (1988 Waite Agricultural Research Institute). Manganese in soils and plants: Proceedings of the International Symposium on "Manganese in Soils and Plants" held at the Waite Agricultural Research Institute, the University of Adelaide, Glen Osmond, South Australia, August 22-26, 1988, as an Australian Bicentennial event. Dordrecht: Kluwer Academic, 1988.
Den vollen Inhalt der Quelle findenBuchteile zum Thema "Soils South Australia Nitrogen content"
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Slattery, J. F., W. J. Slattery und B. M. Carmody. „Influence of Soil Chemical Characteristics on Medic Rhizobia in the Alkaline Soils of South Eastern Australia“. In Highlights of Nitrogen Fixation Research, 243–49. Boston, MA: Springer US, 1999. http://dx.doi.org/10.1007/978-1-4615-4795-2_49.
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Schlesinger, William H., und Sandy L. Tartowski. „Nutrient Cycling within an Arid Ecosystem“. In Structure and Function of a Chihuahuan Desert Ecosystem. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780195117769.003.0010.
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Low quantities of soil nitrogen limit plant growth in the Chihuahuan Desert (Ettershank et al. 1978; Fisher et al. 1988; Lajtha and Whitford 1989; Mun and Whitford 1989) and in other deserts of the world (Wallace et al. 1980; Breman and de Wit 1983; Sharifi et al. 1988; Link et al. 1995). Indeed, although deserts are often regarded as water-limited systems, colimitation by water and N may be the more general rule (Hooper and Johnson 1999; Austin and Sala 2002). In a broad survey of desert ecosystems, Hooper and Johnson (1999) found evidence for colimitation by water and N even at the lowest levels of rainfall. In arid ecosystems, water is delivered in discrete events separated by drier periods, which restrict biological activity and uncouple plant uptake of nutrients from decomposition. Local variations in net primary production in arid and semiarid ecosystems are largely determined by processes that control the redistribution of water and soil nutrients across the landscape (Noy-Meir 1985; Schlesinger and Jones 1984; Wainwright et al. 2002; see also chapter 11). In this chapter we focus on the N cycle in different plant communities of the Jornada Basin with the recognition that after water, N is the most likely resource to determine the plant productivity of this ecosystem. Where arid environments are dominated by shrubby vegetation, the distribution of soil properties is markedly patchy with strong accumulations of plant nutrients under shrubs and relatively infertile soils in the intershrub spaces (Noy-Meir 1985). These islands of fertility are particularly well described in the Chihuahuan Desert and other areas of the American Southwest. Local accumulations of nutrients under vegetation are also documented for desert habitats on other continents, including Europe (Gallardo et al. 2000), Africa (Gerakis and Tsangarakis 1970; Belsky et al. 1989; Wezel et al. 2000), Australia (Tongway and Ludwig 1994; Facelli and Brock 2000), and South America (Rostagno et al. 1991; Mazzarino et al. 1991, 1998; Gutierrez et al. 1993). In the Jornada Basin, Schlesinger et al. (1996) used geostatistics to compare the scale of soil heterogeneity in arid habitats dominated by shrubs and in adjacent areas of arid grassland.