Дисертації з теми "Soils Phosphorus content"
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1
Zhang, Tiequan. "Chemical behavior of phosphorus over time in fertilized soils." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=34486.
Анотація:
Fertilizer P accumulates in soils, with potential for movement to waterways, causing eutrophication. Fertilizer P reactions in monoculture corn (Zea mays L.) production over time will determine environmentally sound soil management practices. Soil P changes over time were determined on a Chicot sandy clay loam (Grey Brown Luvisol) and a Ste. Rosalie clay (Humic Gleysol). Fertilizer P was added at 44 and 132 kg P ha$ sp{-1}$ and to the Chicot soil only, manure containing 60 kg P for the first five years. Mehlich-3 (M3) extraction, soil P fractionation, $ sp{31}$P NMR analysis, P in leaching water, and path analysis were measured. Added P increased M3 P more when manure was also added, and in clay soils. To increase M3 P by 1 kg ha$ sp{-1}$ required from 3.6 to 8.1 kg ha$ sp{-1}$ fertilizer P, and when "net" fertilizer additions were used, fertilizer required was from 1.8 to 5.3 kg P ha$ sp{-1}.$ Moderately labile organic P (Po) decreased at 0 added P. With P at the rate of plant removal, inorganic (Pi) and Po fractions were unchanged. Excess P increased labile P and resistant P through moderately labile Pi. More P remained in labile Pi fractions when manure P was added, or in the soil with the higher clay content. Soil organic P levels increased upon fertilization only in the sandy loam soil. Labile and moderately labile Po could be estimated using monoester phosphate values determined by $ sp{31}$P NMR. Inorganic P values in gravitational water increased above 0.05 mg P L$ sp{-1}$ when soil labile Pi increased above 108 mg kg$ sp{-1}$ in the sandy loam soil and 69 mg L$ sp{-1}$ in the clay soil. Thus soil P movement was related to inorganic P additions. Increased fertilizer P did not increase organic P leaching losses. Fertilizer P in corn production may result in groundwater eutrophication.
2
Abou, Nahra Joumana. "Modeling phosphorus transport in soil and water." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102946.
Анотація:
The main objective of this project was to investigate and model phosphorus (P) transport in soil column studies. A model named HYDRUS-NICA was developed, by coupling a hydrological and transport model (HYDRUS-1D model) with an aqueous chemical model (non-ideal competitive adsorption - NICA), to improve the predictions of P transport in soil and water. The HYDRUS-NICA model was developed by replacing the non-linear empirical (Freundlich and Langmuir) equations of the HYDRUS-1D model with the NICA model equations. The numerical accuracy of the HYDRUS-NICA model was then evaluated by comparing the relative errors produced by the HYDRUS-NICA and HYDRUS-1D models. The results showed that the numerical schemes of the HYDRUS-NICA code are stable.The ability of the NICA model to describe phosphate (PO4) adsorption to soil particles was tested using soils collected from agricultural fields in southern Quebec. The surface charge and PO4 adsorption capacity of these soils were measured. Results were used to estimate the NICA model parameters using a non-linear fitting function. The NICA model accurately described the surface charge of these soils and the PO4 adsorption processes.
The HYDRUS-1D model was applied to simulate water flow and PO4 transport in re-constructed soil column experiments. The HYDRUS-1D model was calibrated based on physical and chemical parameters that were estimated from different experiments. Overall, the HYDRUS-1D model successfully simulated the water flow in the columns; however, it overestimated the final adsorbed PO4 concentrations in the soil. The discrepancies in the results suggested that the HYDRUS-1D model could not account for the differences in the soil structure found in the columns, or that the Freundlich isotherm could not adequately describe PO4 adsorption.
The HYDRUS-NICA model was calibrated and validated with results from re-packed column experiments. The simulated results were then compared with results obtained by the HYDRUS-1D model. The overall goodness-of-fit for the HYDRUS-1D model simulations was classified as poor. The HYDRUS-NICA model improved significantly the prediction of PO4 transport, with the coefficient of modeling efficiency values being close to unity, and the coefficient of residual mass values being close to zero. The HYDRUS-NICA model can be used as a tool to improve the prediction of PO4 transport at the field scale.
3
Gichangi, Elias Maina. "Enhancing phosphorus availability in some phosphate fixing soils of the Transkei region, South Africa using goat manure." Thesis, University of Fort Hare, 2007. http://hdl.handle.net/10353/80.
Анотація:
Low availability of soil phosphorus (P) caused by strong sorption of P is a major constraint to agricultural production in most South African soils, particularly those from the high rainfall areas. The aim of this study was therefore to investigate whether combined addition of goat manure with inorganic P fertilizers could enhance P availability in some P fixing soils of the Transkei region, South Africa. The study addressed the following specific objectives (i) to assess P sorption capacities and requirements of selected soils and their relationship with selected soil properties and single point sorption test, (ii) to assess the effects of goat manure and lime addition on P sorption properties of selected P fixing soils (iii) to assess the temporal changes in concentration of inorganic and microbial biomass P fractions following application of inorganic fertilizer P with goat manure in a laboratory incubation experiment, and, (iv) to assess the effects of goat manure application with inorganic phosphate on inorganic and microbial biomass P fractions, P uptake and dry matter yield of maize. Sorption maxima (Smax) of seven soils examined ranged from 192.3 to 909.1 (mg P kg-1) and were highly and positively correlated with sorption affinity constant (r = 0.93, p = 0.01) and organic C (r = 0.71, p = 0.01). The amount of P required for maintaining a soil solution concentration of 0.2 mg P l-1 ranged from 2.1 to 123.5 mg P kg-1 soil. Soils collected from Qweqwe (a Cambisol), Qunu (an Acrisol), Ncihane (a Luvisol) and Bethania (a Ferralsol) had lower external P requirement values and were classified as lower sorbers, whereas soils from Ntlonyana (a Planosol), Chevy Chase (a Ferralsol) and Flagstaff (a Ferralsol) were classified as moderate sorbers. The results suggested that P availability could be compromised in 43 percent iii of the soils studied and that measures to mitigate the adverse effects of P sorption were needed to ensure that P is not a limiting factor to crop production, where such soils are found. Goat manure addition at varying rates (5, 10 and 20 tha-1 dry weight basis) to two of the moderately P fixing soils from Chevy Chase and Flagstaff, reduced P sorption maxima (Smax) compared to the control treatment. Phosphate sorption decreased with increasing amounts of goat manure in both soils but the extent of reduction was greater on Chevy Chase soil than on Flagstaff soil. The relative liming effects of the different rates of goat manure followed the order 20 t GM ha-1 > 10 t GM ha-1 > 5 t GM ha-1. In a separate experiment, addition of inorganic P at varying rates (0, 90, 180, and 360 kg P ha-1) to Flagstaff soil increased labile P fractions (resin P, biomass P and NaHCO3-Pi) and the increases were greater when goat manure was co-applied. The control treatments contained only 17.2 and 27.5 mg P kg-1 of resin extractable P in the un-amended and manure amended treatments, respectively which increased to 118.2 and 122.7 mg P kg-1 on day 28 of incubation. Biomass P concentration was increased from 16.8 to 43.9 mg P kg-1 in P alone treatments but the fraction was greatly enhanced with manure addition, increasing it from 32.6 to 97.7 mg P kg-1. NaOH-Pi was the largest extractable Pi fraction and ranged from 144.3 to 250.6 mg P kg-1 and 107.5 to 213.2 mg P kg-1 in the unamended and manure amended treatments, respectively. Dry matter yield and P uptake by maize grown in the glasshouse were highly and significantly (p = 0.05) correlated with the different P fractions in the soil. The correlations followed the order resin P (r = 0.85) > NaOH-Pi (r = 0.85) > NaHCO3-Pi (r = 0.84) >> biomass P (r = 0.56) for dry matter yield at 6 weeks after planting. At 12 weeks after planting, goat manure had iv highly significant effects on resin P and biomass P but had no effect on NaHCO3-Pi and NaOH–Pi. The combination of biomass P, resin P and NaHCO3-Pi explained 75.8 percent of the variation in dry matter yield of which 63.0 percent of the variation was explained by biomass P alone. The greatest increase in biomass P occurred when added P was co-applied with 5 or 10 tha-1 goat manure. The predictive equation for maize dry matter yield (DM) was: DM (g) = 1.897 biomass P + 0.645 resin P (r = 0.73). Resin P was the fraction that was most depleted due to plant uptake and decreased by 56 to 68 percent between the 6th week and the 12th week of sampling indicating that it played a greater role in supplying plant available P. The results therefore suggested that the use of goat manure may allow resource poor farmers to use lower levels of commercial phosphate fertilizers because of its effect to reduce soil P sorption. In addition, higher increases in biomass P due to manure addition observed at lower rates of added P indicated that goat manure has potential for enhancing bioavailability and fertilizer use efficiency of small inorganic P applications.
4
Leung, Miu-fun, and 梁妙芬. "Persistence of {221}-propeller phytase in soil and its implication in phosphorus mobilization." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B30736511.
5
Stewart, Lynda Irene. "Phosphorus effects on arbuscular mycorrhizal fungi." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102729.
Анотація:
Two field studies were conducted to assess the potential benefit of arbuscular mycorrhizal (AM) inoculation of elite strawberry plants on plant multiplication, and fruit yield, under typical nursery conditions, in particular soils classified as excessively rich in P. To study plant productivity, five commercially in vitro propagated elite strawberry cultivars ('Chambly', 'Glooscap', 'Joliette', 'Kent', and 'Sweet Charlie') were not inoculated with AM fungi or were inoculated with either a single species (Glomus intraradices), or a mixture of species (G. intraradices, Glomus mosseae, and Glomus etunicatum). AM inoculation was found to impact strawberry plant productivity in a soil with excessive P levels. The AM fungi introduced into the field by inoculated mother plants established a mycelial network in the soil through colonization of the daughter plant roots, however, persistence of colonization was determined to below (<12% in inoculated plant roots). In soils excessively rich in P, individual crop inoculation may be the only option for management of the symbiosis, as the host and non-host rotation crops, planted prior to strawberry production, had no effect on plant productivity or soil mycorrhizal potential.To study the impact of AM inoculation on fruit production, three commercially grown strawberry cultivars (Glooscap, Joliette, and Kent) were not inoculated with AM fungi or were inoculated with either G. intraradices or G. mosseae. AM fungi impacted the fruit yield, with all inoculated cultivars producing more fruit than noninoculated cultivars during the first harvest year. The percentage of root colonization could not be used to explain the differences in total fruit yield during the first harvest year, or the increase in total fruit yield the second harvest year.
We wished to examine the effects of various P treatments on C metabolism within the intraradical mycelia (IRM) of the fungus. Specific primers were developed for the Glomus intraradices glucose-6-phosphate dehydrogenase (G6PDH) gene. Real-time quantitative reverse transcriptase polymerase chain reaction (QRT-PCR) was used to measure the gene expression of the G. intrarardices G6PDH gene in response to external P conditions of colonized transformed carrot roots. The results showed a significant down-regulation of G6PDH in the IRM of G. intraradices when cultures were grown in a high P (350 muM P) medium compared to those grown in the low P (35 muM P) medium. The down-regulation may suggest a reduction in the C flow from the host to the fungus. There was no effect on G6PDH expression following a two-hour incubation with additional P applications (No P, low P and high P).
6
Croat, Samantha Jo. "Phosphorus Dynamics and Crop Productivity in Bakken Crude-Oil Remediated Soils." Thesis, North Dakota State University, 2018. https://hdl.handle.net/10365/29169.
Анотація:
Thermal desorption (TD), a remediation method used to remove hydrocarbons from contaminated soils, may cause changes in soil properties that threaten soil function and plant productivity. The goal of this research is to better understand the effect that TD treatment has on soils intended for agricultural use. A series of soil phosphorus (P) sorption and desorption experiments were conducted on soils before and after TD treatment to determine P availability for plant uptake and risk for run-off. TD-treated soils retained more P, likely due to mineral transformations of Fe- and Al-oxides. In addition, a three-year field study using mixtures of topsoil (A), crude-contaminated soil (SP), and TD-treated soils (TDU) was conducted. Yields were significantly greater in plots that included A in the mixture compared to SP and TDU soils alone. TD-treated soils can be a replacement for topsoil, but the addition of topsoil will reduce the time to successful reclamation.
7
A, Heskett Richard. "Determining soil phosphorus concentrations using cattail indicators." Virtual Press, 1997. http://liblink.bsu.edu/uhtbin/catkey/1048396.
Анотація:
Excess phosphorus is often identified as a major factor in the eutrophication of wetlands and lakes. Often attributed to agricultural practices, the specific source of a large part of this excess has been difficult to determine. The term "nonpoint" source is often used to broadly describe the inflow along waterways of significant amounts of this essential plant nutrient and other pollution. This research was intended to determine the effectiveness of using cattails (Typha), a common plant along waterways, as indicators of plant available phosphorus in the soil along these waterways. Two sites in the southern part of Michigan's lower peninsula (45°N,84°W) where cattails grew were systematically examined for phosphorus and certain cattail characteristics. Plant and soil data were gathered in a grid-like pattern to determine both the relationship of paired data and their spatial distribution across each site. One set of data was shown to be significant. At one site, the density of cattails is weakly correlated with Phosphorus concentrations. Of particular importance, the spatial distribution of both variables is also noticeably similar at the site. No significant correlation between other data was shown. There is also no apparent similarity in spatial distribution. Though weakly correlated, we were able to support a hypothesis that a reasonable correlation exists between cattail density and plant available phosphorus at one site. The spatial distribution of these traits are also similar suggesting that cattails may, in some cases, be useful as indicators of excess phosphorus, perhaps better defining its source than “nonprint”.Department of Biology
8
Kathuli, Peter. "The effects of 40 years of cultivation on organic phosphorus in a highly organic soil of south western British Columbia." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29034.
Анотація:
The effects of 40 years of integrated field management on soil organic phosphorus and its forms was evaluated on a highly organic B.C. soil supporting high value vegetable crops. This project was undertaken to study the effects of cultivation on the soil content of organic phosphorus, as a predictor of overall degradation effects of the soil organic matter. Organic carbon, total nitrogen, soil pH and total and inorganic phosphorus were also evaluated, due to the strong relationship of organic P and these other soil chemical properties. The forms of organic P that were evaluated were the phytic acid, inositol polyphosphates and the soil biomass phosphorus.
The biomass P was used as a predictor of the effects of cultivation on nucleic acids since the soil methods for nucleic acid determination were very complicated and time consuming.
In this study, attempts were made to find a shorter soil analytical method for phytic acid, the largest pool of soil organic phosphorus. Due to chemical structure of phytic acid and its higher negative charge, it was believed that this molecule is highly stable in the soil environment due to its adsorption and/or precipitation on mineral surfaces through cation bridging at low soil pH particularly by Iron and Aluminium salts and hydrous oxides which bear pH-dependent positive charge or through P chermsorption, and hence its turnover rate due to cultivation could be used to predict the behaviour of the rest of soil organic P and hence the organic matter in the same soil environment.
It was however realized that P analysis in soils was very cumbersome and there was a need for a shorter and precise quantitative analytical technique for this element in the soil. ³¹P NMR spectroscopy was thought to be the solution and its possibilities were evaluated in this project. Therefore the objectives of the study were;
a) To determine the effects of 40 yrs of integrated field managements on organic P and its forms.
b) To develop a shorter method for soil phytic acid analysis.
c) To attempt the use of ³¹P NMR for qualitative
and quantitative determinations of soil phytic acid.
It was found that soil pH was significantly increased from pH 4.46 to 5.28 due to liming and the increased degree of organic matter decomposition.
Total nitrogen was significantly decreased by 24% with larger significant decrease of 42% in the shallow organic cultivated soil site, and only 8% significant decrease in the highly organic, deeper cultivated soil site. The decline in soil nitrogen was attributed to mineralization of organic nitrogen followed by crop uptake and leaching losses.
Organic carbon was significantly decreased by 22%. There was a 40% decrease in this organic carbon in the cultivated shallow organic cultivated soil site, but there was no significant effect of cultivation on organic carbon (hence the organic matter) in the highly organic deeper cultivated soil site. There was no significant effect of cultivation on the C/N ratio. However, the highly organic deeper soil site had significantly wider C/N ratio than the shallow organic cultivated soil site. This observation was attributed to the degree of decomposition of soil organic matter in the two sites.
There was a significant 20% decrease in P total in the highly organic deeper cultivated soil site. There was no significant effect of cultivation on P total in the shallow organic cultivated soil site, however there were indications of 33% accumulation in total P in this soil site as determined by ignition method.
There was 179% accumulation of inorganic P in the shallow organic cultivated soil site, but there was no significant effect of cultivation on inorganic P in the deeper highly organic soil cultivated site.
Organic phosphorus was significantly decreased by 4 0 yrs of integrated field management by 31% on a soil basis and 25% on an ash free basis. The percentage of organic P in total soil P was significantly decreased from 66% to 45%. The C/orgnic P was increased significantly from 394 to 439. This reflected greater effects of cultivation on turnover of organic P than organic carbon in the organic matter and that P has a geological cycle which organic carbon does not have. The results further showed that before the field was placed under cultivation, the shallow organic soil site had a significantly larger amount (73%) of organic P in the soil total P. However cultivation had a significant decrease in organic P by 23% in the deeper highly organic soil cultivated site and 40% in the shallow organic cultivated soil site.
The study soil sites started with same the amounts of biomass P (the most labile form of organic P) , however it was found that 40 years of cultivation had no significant effects on this biomass in the highly organic soil site, but there was a significant decrease in biomass P by 86% in the shallow organic cultivated soil site.
Soil phytic acid, the largest pool of organic P was significantly decreased by 28% due to 40 yrs of integrated field management. Its turnover rate was found to be equal to the turnover rate of the other forms of organic P. It was however noted that the study soil sites started with same amount of phytic acid before the field was placed under cultivation. Phytic acid was significantly decreased due to cultivation in the shallow organic cultivated soil site by 35%, but there was no significant effect of cultivation on phytic acid in the highly organic cultivated soil site.
Inositol polyphosphates were not significantly affected by 40 years of integrated management. This form of organic P was found to have the same turnover rate as the rest of soil organic P. The slower turnover rate of inositol polyphosphates assayed by the barium acetate precipitation method of McKercher and Anderson was attributed to methodology.
In the present study, there were no significant differences in results obtained by various methods for total P determination except in a few cases where the ignition method was thought to have over-estimated total P.
A tentative new method for phytic acid analysis was developed in the on-going research. This method was proposed to be applicable in all soils. However, further research is required to confirm the purity of the phytic acid determined by this method.
³¹P NMR spectroscopy showed potential possibility for qualitative and quantitative analysis of soil phytic acid. However, it was emphasized that care should be exercised particularly during sample concentration step.
It was concluded that organic P and its forms, organic carbon, total nitrogen, soil pH and phytic acid were significantly decreased by 40 years of integrated field management more in the shallow organic cultivated soil sites than in the deeper highly organic soil sites. This observation was found very interesting and was in contrast to existing soil literature and further research was proposed in this direction to investigate this phenomenon.Land and Food Systems, Faculty of
Graduate
9
Piper, Allison. "Root Length Affects Soluble Carbon and Phosphorus in a Rotational Cropping System." Fogler Library, University of Maine, 2005. http://www.library.umaine.edu/theses/pdf/PiperA2005.pdf.
10
Ouyang, Duosheng. "New fertilizer combinations for improved nitrogen and phosphorus use efficiency and reduced environmental damage in corn production." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0004/NQ30353.pdf.
11
Xie, Xinghua. "Effects of ammonium lignosulphonate and diammonium phosphate on soil organic matter, phosphorous fractions and corn (Zea mays L.) yield in two eastern Canadian soils." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56811.
Анотація:
Phosphorous fertilizer has an efficiency of about 10 percent, and this efficiency must be improved, in order to avoid excessive loss of a non-renewable resource. Ammonium lignosulphonate (ALS), a by-product of the pulp and paper industry, is expected to improve efficiency of fertilizer phosphate (P) for corn (Zea mays L.) production. Field experiments were conducted to investigate effects of added ALS and P on soil organic matter and P fractions, as well as corn yields and nutrient uptake in a Ste. Rosalie clay soil and an Ormstown silty clay loam soil in 1990 and 1991. Incubation studies showed that added ALS increased organic matter but added P as diammonium phosphate (DAP) decreased organic matter in the fertilizer band location in both soils. Applied ALS with P increased Mehlich-III (M$ sb3$P) extractable P and bicarbonate extractable P in the fertilizer band location in both soils during early incubation periods. Soil Ca-P was decreased with increased ALS. However, soil Al-P and Fe-P compounds were increased with increased ALS. Applied P increased corn shoot P concentration at the six leaf stage, and increased grain yields, total dry matter (TDM) and N and P uptake in both soils. Applied ALS at up to 608 kg ha$ sp{-1}$ with P increased corn shoot P concentration at the six leaf stage in the Ste. Rosalie soil in 1991. Applied ALS at up to 304 kg ha$ sp{-1}$ with P increased grain yield, N and P uptake. However, applied ALS without P decreased stover N concentration. Thus, ALS may improve efficiency of fertilizer P for corn production depending on soil and application methods.
12
Misra, Rabindra Kumar. "Root growth and phosphorus uptake in relation to soil structure and strength /." Title page, table of contents and summary only, 1986. http://web4.library.adelaide.edu.au/theses/09PH/09phm6781.pdf.
13
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.
14
Liu, Aiguo 1949. "Mycorrhizal symbiosis and nutrient uptake in new maize hybrids with contrasting phenotypes as influenced by soil phosphorus level." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36820.
Анотація:
Development and functioning of arbuscular mycorrhizal (AM) symbiosis in the soil-plant system are required in sustainable agriculture. AM development of maize genotypes and uptake of nutrients as influenced by soil P levels were studied. Several experiments were conducted both in the greenhouse and in the field.In greenhouse trials, pasteurized substrates were inoculated with Glomus intraradices as mycorrhizal treatments. Mycorrhizal development varied widely among maize hybrids and inbreds. Leafy normal stature (LNS) had the highest root colonization and shoot:root ratio and was the most responsive to AM fungi. Mycorrhizal development was generally reduced at high soil P and micronutrient levels. The percentage of root colonization was correlated with the ratio of plant tissue N/P only when soil N level was intermediate. Mycorrhizal plants increased uptake of Zn and Cu only at low P and low micronutrient levels, but decreased Mn uptake at higher micronutrient level.
In field trials, soil fumigation was used to eliminate AM fungi in control plots. Again LNS was most responsive to indigenous AM fungi, closely followed by Non-leafy normal stature (NLNS). Mycorrhizae increased uptake of K, Ca and Mg only when these nutrients and available P were low in soil. Correlations between extraradicular hyphae and plant concentrations of K, Ca and Mg suggested that uptake of K was more dependent on extraradicular hyphae than uptake of Ca and Mg. Total P uptake was higher in plots where the AM symbiosis was not repressed, but soil available P was not always reduced.
There is potential for development of mycorrhiza efficient maize hybrids performing well under low input management in sustainable agriculture.
15
Coyle, Kieran. "An investigation of the role of soil micro-organisms in phosphorus mobilisation : a report submitted to fulfil the requrements of the degree of Doctor of Philosophy." Title page, table of contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09phc8814.pdf.
16
Shetterly, Benjamin James. "Soil Phosphorus Characterization and Vulnerability to Release in Urban Stormwater Bioretention Facilities." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4354.
Анотація:
Modern urban stormwater infrastructure includes vegetated bioretention facilities (BRFs) that are designed to detain water and pollutants. Phosphorus (P) is a pollutant in stormwater which can be retained in BRF soils in mineral, plant, and microbial pools. We explored soil properties and phosphorus forms in the soils of 16 operational BRFs in Portland, OR. Since soil hydrology can significantly impact P retention, we selected BRFs along an infiltration rate (IR) gradient. We conducted sequential fractionation and tests of P pools and measured P release in a subset of soils after drying and flooding samples for ten days. We hypothesized that mineral or organic soil P forms would be correlated with IR, and that vulnerability to P release would depend on the interaction of drying and flooding treatments with P forms and pools. IR did not significantly explain differences in P forms. Soil TP was elevated across all sites, compared with TP in agriculturally-impacted wetlands and was substantially composed of soil organic matter (OM)-associated P. Phosphorus sorbed to mineral Fe and Al oxides- was variable but positively correlated with water-extractable P. The concentration gradient of water-extractable P was primarily controlled by overall P pools. Experimentally induced P releases were seen in 5 of 6 soils exposed to drying conditions, presumably released through microbial mineralization of OM. Only one site showed significant P release following the flooding treatment. Our measurements supported the idea that Fe and Al oxides provide P sorption capacity in these BRF soils. Variable inputs of P to BRFs through stormwater and litterfall may contribute to variability in P profiles and P release vulnerability across sites. Design specifications and management decisions relating to bioretention soils (e.g. establishment of acceptable soil test P levels, focusing on P forms known to influence vulnerability of P release) may benefit from detailed biogeochemical investigations.
17
Medina-Ross, Jose Antonio. "Study on phosphorus desorption and availability to soybean (Glycine max L.) in two phosphorus rich Gleysolic soils under different tillage and fertilization practices." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21609.
Анотація:
Soil phosphate is essential for the development and maturity of crops. Plants absorb phosphate from the soil solution which is continuously replenished by fertilizer application and/or desorption from the soil solid phase. Anion exchange membranes (AEMs), act in a similar way to plant roots, adsorbing P from soil solution. Desorption of available P was studied in 1997 on two Gleysolic soils rich in P, a Ste. Rosalie clay soil and a Duravin sandy loam soil, using fluoride-saturated AEMs let in soil suspension for various contact periods. Determination of available P using these AEMs was compared to P extraction using the Mehlich III extractant for predicting P availability to soybean (Glycine max L.). Desorption from both soils, and subsequent adsorption by AEMs was found to decrease with time. A high P desorption rate was calculated for both soils with the Elovich equation. Different chemical and physical characteristics such as pH, Mehlich III extractable Al, Fe and Ca, sand and clay content were in some cases, positively correlated and in other cases, negatively correlated with various contact periods for both soils. The use of AEMs better predicted P availability than the Mehlich III extractant, although the most important asset of using AEMs is that they showed the desorption effect over time on P availability. It was observed that P remobilization from the vegetative part to the grain was reduced due to the high P concentration in both soils.
18
Lukhele, Nomagugu Precious. "Site-specific environmental risk assessment for phosphorus runoff." Thesis, University of Limpopo, 2014. http://hdl.handle.net/10386/1291.
Анотація:
Thesis (MSc. Agriculture (Soil Science)) -- University of Limpopo, 2014Phosphorus (P) runoff from agricultural sites and the subsequent loading into surface water bodies contribute to eutrophication. Environmental concerns associated with P loading in soil have motivated the need for the development of a proper tool that will allow farmers to identify agricultural areas or management practices that have the greatest potential to accelerate eutrophication. The objective of the study was to determine the spatial variability of soil test P, soil loss potential of the farm, P application rate and methods, and map P runoff risk across the field. This study was conducted in Vierfontein Boerdery in Kriel, Mpumalanga province, South Africa (longitude 29.11258833 and latitude -26.27104340). The field was under dryland cultivation and planted to yellow maize that was rotated with soybeans. Soil samples were taken at georeferenced locations in a 100 x 100 m grid for soil analysis. Spatial layers of soil P distribution, soil loss potential as well as application rate and method were created in ArcGIS software. These layers were used as input factors in a P index model to identify areas in the farm that are vulnerable to P runoff. Results indicated a variation in soil test P. Although soil test P variation was not statistically different at P≤0.05, variation had both agronomic and environmental implications. This variation could be attributed to differences in site-specific conditions and management practices. Furthermore, soil loss potential across the study site predicted by the Revised Universal Soil Loss Equation (RUSLE) showed variation with a range of 3-15 tons/ha/yr. This variation was attributed to differences in topographic variations in the study site. There is a need for best management practices that control soil erosion to minimize P runoff into water bodies. KEYWORDS: Eutrophication, Geographic Information System, Phosphorus best management practises, Phosphorus runoff index, Soil erosion, Site-specific management.
19
Sigrist, Andrew B. (Andrew Bernard). "Influence of incubating liquid hog manure and monocalcium phosphate on phosphorus availability and fractionation." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69518.
Анотація:
Incubation mixtures of liquid hog manure (LHM), with and without monocalcium phosphate (MCP) were added to an Ormstown silty clay loam and a Ste. Rosalie clay. Ryegrass (Lolium multiflorum Lam.) was cultivated in a pot study in order to determine yield, total P uptake and soil P content as affected by various P and manure treatments.Aeration of LHM with MCP was successful in reducing ammonia volatilization by 62.4%. However, for both soils, neither of the treatments; LHM amended and aerated with MCP and applied at 32 t ha$ sp{-1}$ LHM containing 513 kg $ rm P sb2O sb5 ha sp{-1}$ from MCP nor LHM aerated without MCP applied at 32 t ha$ sp{-1}$ LHM, plus 513 kg $ rm P sb2O sb5 ha sp{-1}$ from MCP, significantly affected ryegrass yields compared to the lone addition of MCP fertilizer (513 kg $ rm P sb2O sb5 ha sp{-1}).$ Total P uptake in ryegrass was significantly higher for the incubated treatments in the Ste. Rosalie soil alone.
Although additions of LHM or MCP and LHM-MCP combinations affected Mehlich-III and Hedley P fractions, the incubation of MCP with LHM did not significantly increase either inorganic- or organic-P fractions when compared to MCP alone. Therefore, premixing MCP with the LHM had no effect on improving P availability in either the Ormstown or Ste. Rosalie soils.
20
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.
Анотація:
[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
21
Yusran, Fadly Hairannoor. "Soil organic matter decomposition : effects of organic matter addition on phosphorus dynamics in lateritic soils." University of Western Australia. School of Earth and Geographical Sciences, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0120.
Анотація:
[Truncated abstract] Relationships between the persistence of organic matter added to soil, the dynamics of soil organic carbon (C) and phosphorus (P) were examined in four experiments on lateritic soils of Western Australia. The main objective was to quantify the release of P following organic matter application in soils which have high P adsorbing capacity. Another objective was to confirm that due to its recalcitrant materials, the effect of peat lasted longer in soil than other sources of organic matter in terms of increasing plant-available P fractions. Three experiments were conducted under glasshouse conditions for various lengths of time, with nine- to twelve-month incubations to investigate these hypotheses. As expected, organic matter with lower C:N ratios than peat (lucerne hay) decomposed more rapidly compared with peat, and the most active mineralisation took place within the first three months of incubation. Soil organic-C (extracted by 0.5 M K2SO4) had a significant positive correlation with P extracted with 0.5 M NaHCO pH 8.53. For a higher application rate (120 ton ha-1), peat was better than wheat straw and lucerne hay in increasing extractable bicarbonate-P concentrations in soil, especially at incubation times up to 12 months. Throughout the experiment, peat was associated with a steady increase in all parameters measured. In contrast to peat, nutrient release from lucerne hay and wheat straw was rapid and diminished over time. There was a tendency for organic-C (either in the form of total extractable organic-C or microbial biomass-C) to steadily increase in soil with added peat throughout the experiment. Unlike wheat straw and lucerne hay, extractable organic-C from peat remained in soil and there was less C loss in the form of respiration. Therefore, peat persisted and sequestered C to the soil system for a longer time than the other source of organic matter. Freshly added organic matter was expected to have a greater influence on P transformation from adsorbed forms in lateritic soils than existing soil organic matter. By removing the existing soil organic matter, the effect of freshly applied organic matter can be determine separately from that of the existing soil organic matter for a similar organic-C content. In order to do this, some soil samples were combusted up to 450° C to eliminate inherent soil organic matter. The release of P was greater when organic-C from fresh organic matter was applied to combusted soils than in uncombusted soils that contained the existing soil organic matter. The exception only applied for parameters related to soil micro-organisms such as biomass-C and phosphatase. For such parameters, new soil organic matter did not create conditions favourable for organisms to increase in activity despite the abundance of organic matter available. More non-extractable-P was formed in combusted soils compared to bicarbonate-P and it contributed to more than 50% of total-P. As for the first experiment, peat also showed a constant effect in increasing bicarbonate extractable-P in the soil
22
Turgeon, Julie. "Production and biodegradation of dissolved carbon, nitrogen and phosphorus from Canadian forest floors." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115710.
Анотація:
Dissolved organic matter (DOM) is operationally defined as soluble/colloidal material passing through a 0.45mum filter paper. The importance of DOM in soils relies on its role in soil formation and weathering processes, plant and microbial assimilation and soil and water acidification. However, the scientific community studying DOM still disagrees on whether fresh or humified material is the major source of DOM within the forest floor. One of the factors that could influence the overall importance of DOM production by organic horizons is its potential for biodegradability. In addition, the interaction occurring between the nutrients (i.e. nitrogen (N) and phosphorus (P)) and carbon (C) substrate is believed to be of major importance.To acquire more knowledge on the production and biodegradation of dissolved C, N and P during decomposition of organic matter (OM), I performed laboratory incubations to evaluate rates of production and transformation, the influence of the degree of OM decomposition and stand type on these rates, and the stoichiometric relationships of the different quotients during the incubations. First, I performed a 30-day incubation of coniferous and deciduous OM from 10 Canadian forest floors representing various degrees of OM decomposition and subsequently measured the amount of: dissolved organic carbon (DOC), total dissolved nitrogen (TDN), nitrate (NO3-N), ammonium (NH4-N), dissolved organic nitrogen (DON), total dissolved phosphorus (TOP) and carbon dioxide (CO2-C). I performed water extractions with the same set of samples to evaluate the biodegradability of DOC and DON and the transformations of TDN, NO3-N and NH4-N.
Fresh material produces more DOM than humified material; material in the midpoint of decomposition (F horizon) produced the largest amount of DIN. Coniferous and deciduous samples did not display different rates of DOM production, most likely because of the overshadowing effect of OM degree of decomposition. I found strong links between the organic matter and dissolved phase C and N content and C:N quotient. The biodegradation, measured as DOC disappearance and mineralization of CO2-C, showed a discrepancy, reflecting the importance of increasing microbial biomass at the beginning of the incubation in response to priming effect. The sharp decrease of TDN and DON observed in the first few days of the incubation, in addition to increasing amount of dissolved inorganic N as waste products during decomposition of DON, supports this hypothesis. A better understanding of the dynamics of dissolved C, N and P in soil is essential to further understand their role in global elemental cycles, including climate change, forest management and pollution.
23
Stämpfli, Nicolas. "The effect of water table management on the migration of phosphorus and on grain corn yields." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19763.
Анотація:
Due to recent research suggesting that water table management (WTM) can significantly reduce nitrate (NO3") loads in agricultural drainage, a study was carried out in 2001 and 2002 in Coteau-du-Lac, 60 km west of Montreal, to investigate the effect of water table management on the migration of phosphorus (P) via tile drainage and surface runoff. The second main objective was to study the influence of WTM on grain corn yields. Two drainage treatments were compared: conventional free drainage and WTM (combined controlled drainage and subirrigation) with a design water table depth at 0.6 m below the ground surface. Tile drainage and surface runoff were monitored and sampled automatically. Increased outflow volumes and concentrations - and therefore increased P loads - were measured in drainage water from plots under WTM. Plots under WTM also generally exhibited higher P loads in surface runoff. Higher P concentrations in surface runoff from plots under WTM were observed in surface runoff, especially during winter. Phosphorus loads from combined tile drainage and surface runoff were low compared with literature data (<0.4 kg/ha/year). However, the mean P concentrations in tile drainage were above Quebec's surface water quality standard of 0.03 mg total P/L during both growing seasons in plots under WTM, but not in plots with conventional free drainage. Mean P concentrations in surface runoff water routinely exceeded the criteria, except in plots with conventional free drainage in winter 2002. Therefore, P from tile drainage and surface runoff could contribute to the eutrophication of surface water. Based on these results, WTM increases P loads from the field, both in tile drainage and surface runoff. However, the well water used for subirrigation was found to contain P concentrations above Quebec's surface water quality standard, and this could partly explain the higher P concentrations found in water from plots under WTM. Water table management increased grain corn yields by 35% in both years. The growing seasons of 2001 and 2002 were among the driest ever recorded in Canada.
24
Nuruzzaman, Mohammad. "Phosphorus benefits of white lupin, field pea and faba bean to wheat production in Western Australian soils." University of Western Australia. School of Plant Biology, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0094.
Анотація:
[Truncated abstract] Soils of Western Australian cropping regions are very low in phosphorous. White lupin, chickpea, and faba bean are being increasingly used in rotations with wheat on these soils. Yield of wheat after a legume crop is frequently higher than its yield after wheat. It has been reported that in addition to nitrogen, legumes can also contribute to improve the availability of phosphorous for the subsequent crops. This PhD research project aimed at optimising the economic returns of wheat-legume rotations through more efficient use of P fertiliser in the legume phase as well as enhanced availability of soil P in the subsequent wheat phase
25
MacDonald, Tim. "The effects of excessive liquid hog manure applications on phosphorus concentrations in soil and surface runoff from corn and forage crops." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0033/MQ64398.pdf.
26
Simpson, Lisa G. "Impact of long-term manure application on soil macronutrient levels in Southern Alberta." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Geography, c2010, 2010. http://hdl.handle.net/10133/3098.
Анотація:
The role of manure applications on soil nutrient dynamics in years after manure applications cease has not been extensively studied. An investigation of two long-term manure trials in the Battersea Drain watershed in southern Alberta was undertaken in 2004 to determine changes in soil nutrient status three years after the initial study was completed. The investigation of the nutrient status of an intensive livestock operation was another component of the study. There was a significant decrease in levels of soil nitrogen, phosphorus and potassium in the plots that received manure application rates over 60 Mg ha-1. The nutrient status of the farm showed a net export of nitrogen and an accumulation of phosphorus and potassium in the soil. Recommendations for alternate methods for handling manure were presented.x, 120 leaves : ill (some col.), col. maps ; 29 cm
27
Mutter, Rodney N. "An assessment of cropland application of alum sludge." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-07212009-040409/.
28
Turgeon, Julie. "Production and Biodegradation of Dissolved Carbon, Nitrogen and Phosphorous from Canadian Forest Floors." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=105310.
Анотація:
Dissolved organic matter (DOM) is operationally defined as soluble/colloidal material passing through a 0.45~m filter paper. The importance of DOM in soils relies on its role in soil formation and weathering processes, plant and microbial assimilation and soil and water acidification. However, the scientific community studying DOM still disagrees on whether fresh or humified material is the major source of DOM within the forest floor.[...]La matière organique dissoute (DOM) est composée de particules dissoutes et colloïdales passant au travers un filtre de 0.45 Ilm. L'importance de DOM dans les sols est liée à son rôle dans la pédogenèse, les processus d'altération des minéraux, l'assimilation par les plantes et microbes, ainsi que l'acidification des plans d'eau et des sols.[...]
29
Cosme, Marco Paulo Rebeca. "Effects of interaction between arbuscular mycorrhizal fungi, rhizobacteria, soil phosphorus and plant cytokinin content on tobacco growth." Master's thesis, ISA, 2010. http://hdl.handle.net/10400.5/15193.
Анотація:
Mestrado em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de AgronomiaA rizosfera é uma zona importante em termos de actividade e diversidade microbiana, onde ocorrem associações benéficas entre plantas e microorganismos, e é fundamental na produção agrícola. Ao proliferarem num meio complexo e heterogéneo como o solo, as raízes desenvolvem-se de forma estruturada, mas flexível, por forma a optimizar suas funções. Factores endógenos, como fisiologia e genética da planta, bem como factores exógenos abióticos e bióticos são elementos determinantes. Neste estudo proponho testar a hipótese de que os efeitos dos microorganismos do solo sobre o crescimento da planta estão associados a efeitos sobre a morfologia radicular e dependentes dos níveis endógenos de fitohormonas e disponibilidade de nutrientes no solo. Uma experiência factorial foi instalada na estufa, com a presença ou ausência de Glomus intraradices ou Pseudomonas fluorescens, com dois regimes de fertilização de fósforo, e com a linhagem selvagem de tabaco (Nicotiana tabacum) ou a transgénica 35S:CKX2 com teor de citoquinina reduzido. Os efeitos dos microorganismos sobre a biomassa alternaram entre o negativo, neutro ou positivo, dependendo da linhagem, do regime de fertilização e a presença de microorganismos, e explicam-se parcialmente com alterações na morfologia da raiz. A micorrização aumentou na linhagem 35S:CKX2 ou em presença de P. fluorescens-------------------------------------------------ABSTRACT - The rhizosphere is an important zone for microbial activity and diversity, where several beneficial associations between roots and microorganism occur, and is fundamental in terms of defining terrestrial food production. When growing in a complex and heterogeneous medium such as soil, roots develop in a structured but flexible manner to optimize their functions. Endogenous factor, such as plant physiology and genetics, as well as abiotic and biotic exogenous factors are important determinants. In the present study I hypothesized that the effects of soil microorganisms on root morphology are associated with plant growth and differ depending on endogenous phytohormone levels and soil nutrient availability. A full factorial experiment was set up in the greenhouse, with presence or absence of Glomus intraradices or Pseudomonas fluorescens, with two phosphorus amendments, and with the tobacco wild type (Nicotiana tabacum) or the 35S:CKX2 transgenic line with reduced cytokinin content. The effects of microorganisms on plant biomass changed from negative to neutral and positive depending on plant type, phosphorus amendment and microorganism presence, and are partially explained by alteration on root morphology. Mycorrhization was enhanced in the 35S:CKX2 mutant or in presence of P. fluorescens
N/A
30
Novais, Sarah Vieira. "Desgaste dos extratores Mehlich-1 e Fosfato Monocálcico e fatores que controlam a solubilização do fosfato de Bayóvar." Universidade Federal de Viçosa, 2014. http://locus.ufv.br/handle/123456789/5538.
Анотація:
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Previous issue date: 2014-07-07The low availability of phosphorus (P) in tropical soils makes it one of the most studied plant nutrients in the world. Phosphorus fertilization is essential for economically satisfactory yields and the assessment of its long-term availability has become indispensable for the management of this nutrient in agricultural systems. This study was based on two experiments: experiment I, to evaluate the wear of Mehlich-1 (M-1), used in routine analyses of soil available P, and the resulting changes in the currently used critical P levels. For comparison, extractor wear of available sulfur (S) was tested in the same way, using the same soil samples. Twenty soil samples were selected to cover the range of remaining P (P-rem) from 0 to 60 mg L-1 P, as a measure of the phosphate buffering capacity (PBC) in the soil. The extractors M-1 and monocalcium phosphate in acetic acid (MCPa) were routinely applied to determine P and S, respectively, according to protocols used in the Department of Soil Science, Federal University of Viçosa. The pH variation of the two extractors, SO42- of M-1 and of H2PO4- of MCPa, was determined in the soil extract after a rest period of 16 h. A slight but significant wear of acidity (increase in pH) occurred with increasing PBC (decrease in P-rem). On the other hand, SO42- of M -1 was exhausted with increasing PBC, according to a linear-plateau model. This fact indicates the need to adopt an equally discontinuous model for the interpretation of P-available soil with different values of P-rem or PBC. On the other hand, S extractor wear was continuous, linear, with decreased P-rem or increased PBC, which proves that the currently adopted relationship between available S and PBC is correct. For experiment II, samples of Bayovar Rock Phosphate (RP) in an aqueous suspension were placed in a dialysis cassette (Slide-A-Lyzer Dialysis Cassette G2) and this in a 200 mL beaker with 150 mL of an aqueous suspension with drains of P and/or Ca:anionic resin (AR), cationic resin (CR), mixed resin (MR), goethite (Goe), Goe+AR, Goe + RC, and a control treatment (only natural RP). The pH of all treatments was adjusted to 4.5 or 6.0, in five replications. These treatments were stirred for 12 h daily for 18 days, in a horizontal shaker at 130 opm, and then left to stand until completing 30 days of equilibrium due to mechanical deterioration (breaking) of the membranes. In each treatment, solution P, labile P residual P, and total P (the sum of the previous and fractions) were determined. Goethite as P drain caused greater RP solubilization than the other drains at pH 4.5 and than the other drains containing no additional AR or RC. Similarly, AR (P drain) caused similar solubilization to that of RC (Ca drain), indicating that the P drain was as effective in solubilizing RP as the Ca drain. The presence of AR and RC strongly inhibited the action of Goe at pH 4.5, as solubilizing agent of RP. The higher solubilization generally caused by Goe resulted in lower levels of labile P. The effect of higher acidity solubilizing RP was generally less effective than that of the separate or combined drains.
A baixa disponibilidade de fósforo (P) em solos tropicais o torna um dos nutrientes para as plantas mais pesquisados no mundo. A adubação com P é prática essencial para a obtenção de produtividades economicamente satisfatórias e a avaliação de sua disponibilidade ao longo dos anos tem sido imprescindível para o manejo desse nutriente nos sistemas agrícolas. Assim, para este trabalho, foram conduzidos dois experimentos, um (experimento I) com o objetivo de avaliar o desgaste do extrator Mehlich-1 (M-1), utilizado em análises de rotina do P disponível de solos, e a consequente alteração dos níveis críticos deste nutriente atualmente utilizado. Comparativamente, foi conduzido um estudo semelhante com o enxofre (S) disponível, com o mesmo objetivo, utilizando as mesmas amostras de solos. Vinte amostras de solos foram escolhidas de modo a cobrir a faixa de amplitude do P remanescente (P-rem), de 0 a 60 mg L-1 de P, como uma medida do Poder Tampão de Fosfato (PTF) do solo. Nas determinações de rotina de P e de S, foram utilizados os extratores M-1 e fosfato monocálcico em ácido acético (FMCa), respectivamente, segundo protocolos adotados no Departamento de Solos da Universidade Federal de Viçosa. A variação do pH dos dois extratores, de SO42- do M-1 e de H2PO4- do FMCa, foram determinados no extrato solo-extrator após um período de repouso de 16 h. O desgaste da acidez (aumento dos valores de pH) ocorreu com o aumento do PTF (diminuição do P-rem), embora pouco expressiva, mas significativa. Por outro lado, houve o desgaste do SO42- do M-1 com o aumento do PTF, segundo um modelo linear-plateau. Este fato indica a necessidade de adoção de um modelo igualmente descontínuo para a interpretação do P-disponível de solos com diferentes valores de P-rem ou de PTF. Por outro, lado o desgaste do extrator de S foi contínuo, linear, com a diminuição do P-rem ou aumento do PTF, o que mostra ser correta a relação entre S disponível e PTF, atualmente adotada. Para o experimento II, amostras do fosfato natural reativo de bayóvar (FN), em uma suspensão aquosa, foram colocadas em um compartimento de diálise (Slide-A-Lyzer G2 Dialysis Cassette) e este em um becker de 200 mL com 150 mL de uma suspensão aquosa com os drenos de P e, ou, de Ca: resina aniônica (RA), resina catiônica (RC), resina mista (RM), goethita (Goe), Goe+RA, Goe+RC e um tratamento controle (FN natural apenas), com todos estes tratamentos com os valores de pH ajustados em 4,5 ou 6,0, em cinco repetições. Esses tratamentos foram agitados por 12 h diárias, durante 18 dias, em agitador horizontal a 130 opm e não mais até completar 30 dias de equilíbrio, devido a deterioração mecânica (rompimento) das membranas. Foram determinados P-solução, P- lábil, P-residual, e P-total (este como somatória das frações anteriores) de cada tratamento. A Goe, como dreno-P, causou a maior solubilização do FN, em comparação aos demais drenos, a pH 4,5, e aos demais drenos que não continham RA ou RC adicionalmente. De modo semelhante, a RA (dreno-P) causou solubilização semelhante à da RC (dreno Ca), indicando ser o dreno-P tão efetivo na solubilização do FN quanto o dreno- Ca. As presenças das RA e RC inibiram fortemente a ação da Goe, a pH 4,5, como agente solubilizador do FN. A maior solubilização causada, de modo geral, pela Goe causou os menores teores de P-lábil. O efeito da maior acidez solubilizando o FN mostrou-se, de modo geral, menos efetivo que os drenos individualmente ou combinados.
31
Claycomb, Peter T. "Measurement of microbial biomass phosphorus in Oregon soils." Thesis, 1992. http://hdl.handle.net/1957/37135.
32
Mayakaduwage, Sonia Samanthi. "Influence of pH, phosphorus addition and soil water content on phosphorus pools in acid sulfate soils." Thesis, 2020. http://hdl.handle.net/2440/128818.
Анотація:
Acid sulfate soils (ASS) are common in wetlands and important for crop production. However, little is known about P availability in ASS which is constrained due to high Fe content and changing redox potential. This thesis aimed to investigate the effect of P addition, pH and soil water content on P pools in ASS. A sandy sulfuric ASS (pH 3.2) was used in the experiments. In the first experiment, the ASS was amended with NaOH or Ca(OH)2) to achieve soil pH 4 or 5.5, without or with addition of inorganic P equivalent to 20 kg ha−1. Soils were incubated in either submerged or moist conditions (100% of maximum water holding capacity). After two weeks, P pools and Fe /Al oxides were determined. P pools were higher with P addition than without. The increase in pH enhanced Fe oxides but had little effect on labile P. Added soluble P was available after two weeks of addition under submerged conditions. In Experiment 2, the ASS (pH adjusted to 5.5) was amended with phosphate at 0, 96, 385, 578 and 770 mg P kg−1 and incubated under submerged conditions. P pools were measured after two and four weeks. Sorption and release of P were determined in incubated soils and jarosite, separately. The maximum sorption capacity of the soil was 350 mg P kg-1. Jarosite had a high capacity to bind P and contributed about 50% to P binding in this soil. Labile P represented more than 50% of added P at P rates above 350 mg P kg-1. The third chapter included two experiments. In the first experiment, the ASS (pH adjusted to 5.5) was amended with 400 mg P kg-1 as inorganic P, manure or combinations of inorganic P/manure and was incubated submerged. After two and four weeks, labile P was measured. Labile P in treatments with 50% of P added as manure was about half of that in treatments with a greater proportion of inorganic P. In the second experiment, treatments (inorganic P alone: 100F, manure alone: 100M, combination of manure and inorganic P: 50M/50F and unamended control) were kept submerged, then moist, followed by resubmergence. At the end of first submergence, labile P was two-fold higher in 100F than in manure treatments. But in the moist period and after resubmergence, labile P did not differ between 100F and 100M. Oxalate extractable Fe was higher in 100M than 100F and remained unchanged until the end of the experiment. In experiment 4, the ASS (without or with pH increase to 5.5) was amended with mangrove roots to achieve an organic carbon (OC) addition of 50% or 150% of native soil OC and incubated under submerged, moist and then resubmerged conditions. At the end of each four-week period, P pools, amorphous Fe/Al and potential P sorption were measured. Mangrove roots addition decreased the redox potential and increased labile P under submerged conditions, but only at pH 5.5. P binding was enhanced by root addition during the first 8 weeks, but not after re-submergence.Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2020
33
"Nitrogen and phosphorus dynamics in Hong Kong urban park soils." 2005. http://library.cuhk.edu.hk/record=b5892382.
Анотація:
Liu Wing Ting.Thesis submitted in: November 2004.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2005.
Includes bibliographical references (leaves 141-156).
Abstracts in English and Chinese.
Abstract (English) --- p.i
Abstract (Chinese) --- p.iii
Acknowledgments --- p.v
List of Tables --- p.vii
List of Figures --- p.ix
List of Plates --- p.x
List of Appendices --- p.xi
Chapter CHAPTER 1 --- INTRODUCTION
Chapter 1.1 --- Urban ecological environment and the urban parks in Hong Kong --- p.1
Chapter 1.2 --- Conceptual framework of the study --- p.4
Chapter 1.3 --- Objectives of the study --- p.9
Chapter 1.4 --- Scope of the study --- p.10
Chapter 1.5 --- Significance of the study --- p.11
Chapter 1.6 --- Organization of the thesis --- p.12
Chapter CHAPTER 2 --- LITERATURE REVIEW
Chapter 2.1 --- Introduction --- p.13
Chapter 2.2 --- Urban parks and urban soils --- p.13
Chapter 2.3 --- Urban soils: properties and problems --- p.14
Chapter 2.3.1 --- Overseas studies about urban soils --- p.15
Chapter 2.3.2 --- Urban soils in Hong Kong --- p.16
Chapter 2.4 --- Nitrogen dynamics --- p.22
Chapter 2.4.1 --- The internal N cycle and N transformations in soil --- p.22
Chapter 2.4.2 --- Factors affecting nitrogen dynamics in soil --- p.24
Chapter (i) --- "Soil moisture and temperature, seasonality and spatial variation" --- p.24
Chapter (ii) --- Soil pH and texture --- p.26
Chapter (iii) --- Litter quality and C:N ratio --- p.26
Chapter (iv) --- Disturbance --- p.27
Chapter (v) --- Fertilizer input and management intensity --- p.27
Chapter 2.4.3 --- N dynamics in urban areas --- p.28
Chapter 2.4.4 --- Research of N dynamics in Hong Kong --- p.29
Chapter 2.5 --- Phosphorus dynamics --- p.30
Chapter 2.5.1 --- Gains and losses of P from soil system --- p.30
Chapter 2.5.2 --- Forms and transformations of phosphorus in soil --- p.31
Chapter 2.5.3 --- Factors affecting P dynamics in soil --- p.34
Chapter (i) --- Fluctuations of soil moisture --- p.34
Chapter (ii) --- Liming and pH adjustment --- p.34
Chapter (iii) --- Cultivation and management intensity --- p.35
Chapter (iv) --- Vegetation cover and disturbances --- p.35
Chapter 2.5.4 --- P dynamics in urban areas --- p.36
Chapter CHAPTER 3 --- STUDY AREA
Chapter 3.1 --- General situation of Hong Kong and the study locations --- p.37
Chapter 3.2 --- Background of the two parks: Kowloon Park and Tin Shui Wai Park --- p.40
Chapter 3.3 --- Climate --- p.43
Chapter 3.4 --- Park vegetation --- p.45
Chapter 3.5 --- Park soils --- p.47
Chapter 3.6 --- Park management and horticultural routines --- p.47
Chapter CHAPTER 4 --- BASELINE STUDY OF URBAN PARK SOIL PROPERTIES
Chapter 4.1 --- Introduction --- p.52
Chapter 4.2 --- Methodology --- p.54
Chapter 4.2.1 --- Sampling --- p.54
Chapter 4.2.2 --- Soil texture --- p.55
Chapter 4.2.3 --- Soil reaction --- p.55
Chapter 4.2.4 --- Total Kjeldahl nitrogen (TKN) --- p.55
Chapter 4.2.5 --- Mineral nitrogen (ammonium and nitrate nitrogen) --- p.55
Chapter 4.2.6 --- Total phosphorus --- p.56
Chapter 4.2.7 --- Available phosphorus --- p.56
Chapter 4.2.8 --- Organic carbon --- p.56
Chapter 4.2.9 --- "Exchangeable cations (K, Na, Ca, Mg)" --- p.57
Chapter 4.2.10 --- Carbon: nitrogen ratio and carbon: phosphorus ratio --- p.57
Chapter 4.3 --- Statistical analysis --- p.57
Chapter 4.4 --- Results --- p.58
Chapter 4.4.1 --- Texture --- p.58
Chapter 4.4.2 --- Soil pH --- p.58
Chapter 4.4.3 --- Organic matter --- p.59
Chapter 4.4.4 --- Total Kjeldahl nitrogen and C:N ratio --- p.60
Chapter 4.4.5 --- Ammonium nitrogen and nitrate nitrogen --- p.61
Chapter 4.4.6 --- Total phosphorus and C:P ratio --- p.62
Chapter 4.4.7 --- Available phosphorus --- p.64
Chapter 4.4.8 --- Exchangeable cations --- p.65
Chapter 4.5 --- Discussion --- p.66
Chapter 4.5.1 --- Park soils under different vegetation covers --- p.67
Chapter 4.5.2 --- Duration of park management and influence of land use outside the parks --- p.72
Chapter 4.5.3 --- Quality of substrates in Kowloon Park and Tin Shui Wai Park --- p.76
Chapter 4.5.4 --- C:N ratio and C:P ratio --- p.83
Chapter 4.6 --- Conclusion --- p.84
Chapter CHAPTER 5 --- NITROGEN DYNAMICS OF URBAN PARK SOILS
Chapter 5.1 --- Introduction --- p.87
Chapter 5.2 --- Methodology --- p.89
Chapter 5.2.1 --- In situ incubation --- p.89
Chapter 5.2.2 --- "Determination of N mineralization, leaching and uptake" --- p.91
Chapter 5.3 --- Results --- p.94
Chapter 5.3.1 --- "Net ammonification, NH4-N leaching and uptake" --- p.94
Chapter 5.3.2 --- "Net nitrification, NO3-N leaching and uptake" --- p.95
Chapter 5.3.3 --- "Net N mineralization, N leaching and uptake" --- p.96
Chapter 5.4 --- Discussion --- p.97
Chapter 5.4.1 --- Nitrogen mineralization and immobilization --- p.98
Chapter 5.4.2 --- Comparison with other studies --- p.100
Chapter 5.4.3 --- Nitrogen leaching and uptake --- p.103
Chapter 5.5 --- Conclusion --- p.108
Chapter CHAPTER 6 --- PHOSPHORUS DYNAMICS OF URBAN PARK SOILS
Chapter 6.1 --- Introduction --- p.110
Chapter 6.2 --- Methodology --- p.112
Chapter 6.3 --- Results --- p.113
Chapter 6.4 --- Discussion --- p.115
Chapter 6.4.1 --- Phosphorus mineralization and immobilization --- p.115
Chapter 6.4.2 --- Phosphorus leaching and uptake --- p.118
Chapter 6.4.3 --- Comparison with other studies --- p.120
Chapter 6.5 --- Conclusion --- p.122
Chapter CHAPTER 7 --- CONCLUSION
Chapter 7.1 --- Summary of findings --- p.124
Chapter 7.2 --- Implications of the study --- p.128
Chapter 7.2.1 --- Chemical characteristics of urban park soils and their relationship to management --- p.128
Chapter 7.2.2 --- Management practices for different vegetation types and species --- p.133
Chapter 7.3 --- Limitations of the study --- p.136
Chapter 7.4 --- Suggestions for future study --- p.139
REFERENCES --- p.141
APPENDICES --- p.157
34
Mokolobate, Motlogeloa Salathiel. "An evaluation of the use of organic amandments to ameliorate aluminium toxicity and phosphorus deficiency in an acid soil." Thesis, 2000. http://hdl.handle.net/10413/4952.
Анотація:
The effects of the additions of some commonly-available organic residues to an acid, P-deficient soil (typical of those used by small-scale farmers in KwaZulu-Natal) on soil pH, exchangeable and soil solution AI, P availability and maize yield response was investigated in a number of
laboratory and glasshouse experiments. The organic amendments used were ground-up grassveld residues, household compost, filter cake (a waste product from a sugar mill) and layer poultry manure. The soil used was a Hutton form (Farmingham series) (Rhodic Ferrasol, FAO).
In an initial laboratory study, addition of all of the organic residues, at rates equivalent to 10 and 20 Mg ha¯¹, raised soil pH significantly and as a result there was a marked reduction in exchangeable AI concentrations. The increase in pH and decrease in exchangeable AI was more
pronounced at the higher rate of addition and followed the order: poultry manure> filter cake> household compost> grass residues. The major mechanism responsible for the increase in pH was thought to differ depending upon the type of organic residue being considered. Whilst the
relatively high content ofCaC0₃ was probably the main mechanism in the case of poultry manure and filter cake, the proton consuming ability of humic material probably predominated for household compost and decarboxylation of organic acids during decomposition was probably the
main mechanism in the case of grass residues.
Additions of organic amendments also decreased concentrations of total AI (AIT) in soil solution
but the concentration of monomeric AI (AIMono) as estimated by pyrocatechol violet 60 sec. method, was unchanged or even increased. This latter effect was attributed to the high cation content of residues (particularly that of poultry manure) which increased soil salinity and exchangeable AI³⁺ was consequently displaced into soil solution.Additions of amendments also increased the Olsen-extractable P levels in the order: poultry
manure> filter cake> household compost> grass residues and their addition also decreased theP adsorption capacity ofsoils. Concentrations of exchangeable Ca, Mg and K, and Na in the case of poultry manure, were increased by additions of organic amendments. In a glasshouse experiment, the four organic residues were applied to soils at a rate equivalent to 20 Mg ha¯¹ with or without the addition of either lime (equivalent to 0, 5 or 10 Mg ha¯¹) or P (equivalent to 0, 10 or 50 kg ha¯¹). Lime applications to the control (unamended) treatment resulted in a marked reduction in exchangeable AI, AIT AIMono and in the proportion of AIT present as AIMono in soil solution. The addition of organic amendments increased soil pH and
reduced AIT and AIMono to low concentrations regardless of whether lime was applied or not. There was no yield response in maize to applied lime in any of the amended treatments. There was a yield increase in response to applied P in the control, household compost and grass residue treatments but none for the filter cake and poultry manure treatments. In agreement with this, Olsen-extractable P values in soils followed the order: poultry manure> filter cake> household compost> grass residues > control. It was concluded that the addition of organic amendments to acid soils is a practicable way of liming them and reducing the potential for Al toxicity and that it can also reduce fertilizer P requirements. This research now needs to be extended into the field situation.Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.
35
Nelson, Sheila J. "The influence of phosphatase-producing bacteria on phosphatase activity and available phosphorus in soil." Thesis, 1991. http://hdl.handle.net/1957/36590.
36
Iyamuremye, Faustin. "Effects of organic and inorganic soil amendments of phosphorus sorption." Thesis, 1994. http://hdl.handle.net/1957/35679.
37
Norris, Matthew. "Phosphorus sorption behaviour of some South African water treatment residues." Thesis, 2009. http://hdl.handle.net/10413/673.
38
Coyle, Kieran. "An investigation of the role of soil micro-organisms in phosphorus mobilisation : a report submitted to fulfil the requirements of the degree of Doctor of Philosophy / Kieran Coyle." 2001. http://hdl.handle.net/2440/21787.
Анотація:
"September 2001"Includes bibliographical references (leaves 206-230)
xviii, 230 leaves : ill., plates ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 2002
39
Coyle, Kieran. "An investigation of the role of soil micro-organisms in phosphorus mobilisation : a report submitted to fulfil the requirements of the degree of Doctor of Philosophy / Kieran Coyle." Thesis, 2001. http://hdl.handle.net/2440/21787.
Анотація:
"September 2001"Includes bibliographical references (leaves 206-230)
xviii, 230 leaves : ill., plates ; 30 cm.
Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 2002
40
Matlou, Mmakgabo Cordelia. "A comparison of soil and foliar-applied silicon on nutrient availability and plant growth and soil-applied silicon on phosphorus availability." Thesis, 2006. http://hdl.handle.net/10413/3468.
Анотація:
A greenhouse study was carried out to investigate the effectiveness of soil-applied
silicon (Si) with that of foliar applications for sorghum growth. Silicon sources were
soil-applied as calmasil (calcium silicate) at two rates (4 and 8t/ha) and foliar applied
Si including pure K-silicate, K-humate and K-fulvate (all three foliar treatments at
rates of 300 and 600 ppm). Another treatment included soil applied calmasil plus low
rate of foliar applied K-humate. The soils used for the greenhouse trial were Cartref,
Glenrosa, Nomanci and Fernwood. Results indicated that application of calcium
silicate to the soil before planting increased sorghum yield and Si uptake in three of
the four soils. Silicon uptake from different experimental treatments followed the
order: Calmasil 8t/ha > calmasil 4t/ha ~ calmasil + 300 ppm K-humate> K-humate =
K-fulvate = pure-K silicate = control. Foliar sprays were ineffective at increasing
yield, Si content of the plant tissues or Si uptake. The concentrations of
exchangeable Ca, Mg as well as soil pH were significantly increased by calmasil
treatments. Extractable AI concentrations were also reduced due to the Iiming effect
of calcium silicate and also possibly formation of insoluble aluminosilicates. The yield
response to applied calmasil seemed to be primarily related to its Iiming effect and
reductions in extractable AI in the Cartref, Glenrosa and Nomanci soils. The dry
matter yield was highest in Fernwood and lowest in Cartref soil. However, there was
no significant yield response to calmasil in Fernwood soil which had an initial pH of
5.8 and insignificant extractable AI concentrations. Therefore application of calcium
silicate had no significant effect on extractable AI concentration in this soil. Yield
response to calmasil may also have been partly due to direct positive effects of
applied Si on crop growth through mechanisms such as increased photosynthetic
rate and reduced transpiration rate, Addition of calmasil increased the concentrations
of Si in the plant tissues and reduced those of N, P and Kin Nomanci and Fernwood
soils respectively. This indicates that nutrient interactions were occurring in the plant. It was concluded that foliar-application is not an effective way of applying Si to a Siresponsive
crop such as sorghum when growing in soils low in extractable soil Si.
This is because Si is accumulated in plant tissues in similar amounts to
macronutrients. It was also concluded that in future, studies of crop response to
applied Si should include the use of non-Iiming source of Si (e.g. silicic acid) so as to
separate a liming effect of calcium silicate from effect of applied Si.
In a laboratory study, the effects of applied silicic acid, calcium silicate and calcium
hydroxide on levels of extractable P in two Si-deficient soils were investigated. Two
soils (Fernwood and Nomanci soils) were treated with two rates of P and three soil
amendments (calcium silicate, calcium hydroxide and silicic acid) and incubated for
six weeks at room temperature. Phosphorus was extracted using Truog, AMBIC and
resin methods, and levels of exchangeable and solution AI and extractable and
solution Si were also measured. Application of calcium silicate and calcium
hydroxide increased soil pH in both soils while silicic acid additions had no significant
effect compared with the control. The pH increase was much greater in the
Fernwood than Nomanci soil because of the low buffering capacity of the sandy
Fernwood soil. Exchangeable AI and concentrations of monomeric and total AI in soil
solution generally followed the order: control ~ silicic acid> calcium silicate> calcium
hydroxide. The lowering of soluble AI concentrations in the silicic acid treatments
was attributed to formation of insoluble aluminosilicate compounds while that in the
calcium silicate and calcium hydroxide treatments was attributed to their Iiming
effects causing a rise in pH.
Concentrations of Si in soil solution were lower in the calcium hydroxide than the
control treatment suggesting the solubility of Si decreased with increased pH.
Additions of both Si sources increased Si concentrations in solution and the effect
was more marked for the calcium silicate treatment. This was attributed to formation
of insoluble aluminosilicates in the silicic acid treatment. Concentrations of H2S04extractable
Si with treatment did not closely follow the same trends as those for Si
concentrations in soil solution. That is, levels of extractable Si were very much higher
in the calcium silicate than silicic acid treatment in both soils. In addition, concentrations of extractable Si in the calcium hydroxide treatment were similar to
control in the Nomanci soil, while for the Fernwood soil, concentrations in the
calcium hydroxide treatment were exceptionally high. It was suggested that liming
with calcium silicate or calcium hydroxide had rendered some Si-containing
compounds in the soil acid-extractable and that the nature of acid-extractable Si
fraction need further study in future.
The quantities of P extracted from the two soils by the various extractants followed
the order: Truog> AMBle> resin. The greatest increase in extractable P induced by
additions of P was recorded for Truog P and the least for resin P. The effects of
Iiming (addition of calcium silicate or calcium hydroxide) on extractable P levels
differed depending on the soil and extractant used with increase, decrease or no
effect being recorded. Such results confirm the complexity of lime and P interactions
which occur in acid soils. Additions of silicic acid had no effect on levels of
extractable P, compared to control. It was suggested that the reason for this was that
phosphate is adsorbed to AI and Fe oxide surfaces much more strongly than silicate.
As a result, additions of Si are ineffective at increasing extractable P levels.Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.
41
Brooks, Anna. "Effects of phosphorus nutrition on photosynthetic metabolism of spinach leaves." Phd thesis, 1985. http://hdl.handle.net/1885/140654.
42
Miles, Neil. "Pasture responses to lime and phosphorus on acid soils in Natal." Thesis, 1986. http://hdl.handle.net/10413/9621.
43
"Simulation study on the effects of heat and ash on a frequently burnt soil in Hong Kong." 2005. http://library.cuhk.edu.hk/record=b5892332.
Анотація:
Lam Lai-yee.Thesis submitted in: November 2004.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2005.
Includes bibliographical references (leaves 124-140).
Abstracts in English and Chinese.
Abstract --- p.i
Acknowledgement --- p.vii
Table of contents --- p.viii
List of Tables --- p.xi
List of Figures --- p.xiii
List of Plates --- p.xiv
Chapter CHAPTER ONE --- Introduction
Chapter 1.1 --- Introduction --- p.1
Chapter 1.2 --- Background and ecological impact of hill fires in Hong Kong --- p.2
Chapter 1.3 --- Conceptual framework of study --- p.4
Chapter 1.4 --- Objectives of the study --- p.10
Chapter 1.5 --- Significance --- p.11
Chapter 1.6 --- Organization of the thesis --- p.12
Chapter CHAPTER TWO --- The study area
Chapter 2.1 --- Introduction --- p.14
Chapter 2.2 --- Geographical setting of Hong Kong --- p.14
Chapter 2.2.1 --- Climate of Hong Kong --- p.14
Chapter 2.2.2 --- Geology of Hong Kong --- p.15
Chapter 2.2.3 --- Soils of Hong Kong --- p.16
Chapter 2.2.4 --- Vegetation of Hong Kong --- p.17
Chapter 2.3 --- Site selection --- p.18
Chapter 2.4 --- Grassy Hill --- p.20
Chapter CHAPTER THREE --- Heating effect on the properties of ash
Chapter 3.1 --- Introduction --- p.23
Chapter 3.2 --- Experimental design and methodology
Chapter 3.2.1 --- Selection of simulation heating --- p.26
Chapter 3.2.2 --- "Heating intensity at 200°-600°C for 1,5 and 15 minutes" --- p.27
Chapter 3.2.3 --- Field work --- p.27
Chapter 3.2.4 --- Heating method --- p.28
Chapter 3.2.5 --- Chemical analysis --- p.28
Chapter 3.2.6 --- Analysis of data --- p.32
Chapter 3.3 --- Results and Discussion
Chapter 3.3.1 --- Heating effect on ash weight and pH --- p.33
Chapter 3.3.2 --- "Heating effect on ash organic C, N and P" --- p.33
Chapter 3.3.3 --- Heating effect on ash available cations --- p.40
Chapter 3.4 --- Conclusion --- p.42
Chapter CHAPTER FOUR --- The effect of heat and ash on soil
Chapter 4.1 --- Introduction --- p.44
Chapter 4.2 --- Methodology
Chapter 4.2.1 --- Field work --- p.48
Chapter 4.2.2 --- Soil heating methods --- p.48
Chapter 4.2.3 --- Chemical analysis --- p.49
Chapter 4.2.4 --- Statistical analysis --- p.52
Chapter 4.3 --- Results and Discussion
Chapter 4.3.1 --- The effect of heat and ash on soil pH --- p.53
Chapter 4.3.2 --- "The effect of heat and ash on soil organic matter, N and P" --- p.55
Chapter 4.3.3 --- The effect of heat and ash on soil cations --- p.62
Chapter 4.4 --- Conclusion --- p.65
Chapter CHAPTER FIVE --- Nitrogen and phosphorus mineralization after heating
Chapter 5.1 --- Introduction --- p.67
Chapter 5.2 --- Methodology
Chapter 5.2.1 --- Heating and incubation method --- p.70
Chapter 5.2.2 --- Laboratory methods --- p.72
Chapter 5.2.3 --- Statistical analysis --- p.72
Chapter 5.3 --- Results and discussion
Chapter 5.3.1 --- Temporal changes of N mineralization in heated bare soils --- p.72
Chapter 5.3.2 --- The effect of ash on N mineralization --- p.78
Chapter 5.3.3 --- Comparison of N mineralization with other studies --- p.79
Chapter 5.3.4 --- Temporal changes of P mineralization in the heated bare soils --- p.81
Chapter 5.3.5 --- The effect of ash on P mineralization --- p.83
Chapter 5.3.6 --- Comparison of P mineralization to other studies --- p.84
Chapter 5.4 --- Conclusion --- p.85
Chapter CHAPTER SIX --- Vertical movement of mineral N in ash-covered soil columns
Chapter 6.1 --- Introduction --- p.87
Chapter 6.2 --- Methodology
Chapter 6.2.1 --- Package of soil columns --- p.89
Chapter 6.2.2 --- Water addition and extraction of pore water --- p.90
Chapter 6.2.3 --- Statistical analysis --- p.92
Chapter 6.3 --- Results and Discussion
Chapter 6.3.1 --- Mineral N in the pore water --- p.92
Chapter 6.3.2 --- The effect of ash on mineral N in pore water --- p.97
Chapter 6.3.3 --- The leaching loss of mineral N --- p.98
Chapter 6.3.4 --- Comparisons with other studies --- p.103
Chapter 6.4 --- Conclusion --- p.105
Chapter CHAPTER SEVEN --- Integrative discussion
Chapter 7.1 --- Summary of major findings --- p.107
Chapter 7.2 --- Clarifying some misconceptions about the effect of fire --- p.110
Chapter 7.3 --- Estimated losses of N and P from heating --- p.112
Chapter 7.4 --- Nutrient supplying capacity of soils after heating --- p.115
Chapter 7.5 --- Why are repeatedly burnt areas reduced to grassland? --- p.118
Chapter 7.6 --- Implication on the restoration of fire-affected areas --- p.119
Chapter 7.7 --- Limitations of the study --- p.121
Chapter 7.8 --- Suggestions for future research --- p.122
References --- p.124
Appendices --- p.141
44
Hayes, Julie Ellen. "Phytate as a source of phosphorus for the nutrition of pasture plants." Phd thesis, 1999. http://hdl.handle.net/1885/148002.
45
"Phosphorus retention and release characteristics of wetland sediments in Hong Kong." 2007. http://library.cuhk.edu.hk/record=b5893199.
Анотація:
Lai, Yuk Fo.Thesis (M.Phil.)--Chinese University of Hong Kong, 2007.
Includes bibliographical references (leaves 169-191).
Abstracts in English and Chinese.
Abstract --- p.i
Abstract (in Chinese) --- p.iv
Dedication --- p.v
Acknowledgement --- p.vi
Table of contents --- p.viii
List of tables --- p.xii
List of figures --- p.xiii
List of plates --- p.xv
List of symbols and abbreviations --- p.xvi
Chapter Chapter One --- Introduction
Chapter 1.1 --- Introduction --- p.1
Chapter 1.2 --- Research background --- p.1
Chapter 1.2.1 --- Wetlands and water quality --- p.1
Chapter 1.2.2 --- The role of sediments in eutrophication control --- p.3
Chapter 1.2.3 --- Wetlands in ecological mitigation --- p.4
Chapter 1.2.4 --- Previous studies of wetland pollution in Hong Kong --- p.6
Chapter 1.3 --- Conceptual framework --- p.8
Chapter 1.4 --- Objectives of the study --- p.12
Chapter 1.5 --- Significance of study --- p.13
Chapter 1.6 --- Organization of the thesis --- p.14
Chapter Chapter Two --- Literature Review
Chapter 2.1 --- Introduction --- p.15
Chapter 2.2 --- Quantification of phosphorus retention in wetlands --- p.16
Chapter 2.2.1 --- Input-output concentration approach --- p.16
Chapter 2.2.2 --- Mass balance approach --- p.18
Chapter 2.2.3 --- Phosphorus removal efficiency --- p.19
Chapter 2.3 --- Phosphorus sorption by wetland sediments --- p.20
Chapter 2.3.1 --- Sorption and its significance --- p.20
Chapter 2.3.2 --- Phosphorus sorption maxima --- p.22
Chapter 2.3.3 --- Adsorption-desorption equilibrium --- p.23
Chapter 2.3.4 --- Phosphorus sorption kinetics --- p.24
Chapter 2.4 --- Phosphorus exchange across the sediment-water interface --- p.24
Chapter 2.4.1 --- Phosphorus mobilization and transport mechanisms --- p.25
Chapter 2.4.2 --- Phosphorus flux from aquatic sediments --- p.26
Chapter 2.5 --- Phosphorus fractionation in wetland sediments --- p.29
Chapter 2.5.1 --- Major sediment phosphorus fractions --- p.29
Chapter 2.5.2 --- Phosphorus fractionation methods --- p.30
Chapter 2.5.3 --- Relationships between phosphorus fractions and bioavailability . --- p.32
Chapter 2.6 --- Factors affecting sediment-water phosphorus exchange --- p.33
Chapter 2.6.1 --- pH --- p.34
Chapter 2.6.2 --- Redox potential --- p.34
Chapter 2.6.3 --- Temperature --- p.35
Chapter 2.6.4 --- Salinity --- p.35
Chapter 2.6.5 --- Sediment properties --- p.36
Chapter Chapter Three --- Methodology
Chapter 3.1 --- Overall study approach --- p.38
Chapter 3.2 --- Geographical setting of Hong Kong --- p.41
Chapter 3.2.1 --- Climate --- p.42
Chapter 3.2.2 --- Geology and landform --- p.44
Chapter 3.2.3 --- Soil --- p.45
Chapter 3.2.4 --- Vegetation --- p.45
Chapter 3.3 --- Study sites --- p.46
Chapter 3.3.1 --- Site selection --- p.46
Chapter 3.3.2 --- Site description --- p.48
Chapter 3.3.2.1 --- The Hong Kong Wetland Park --- p.48
Chapter 3.3.2.2 --- Mai Po Marshes Nature Reserve --- p.50
Chapter 3.4 --- Sampling strategy --- p.53
Chapter 3.4.1 --- Sampling locations --- p.53
Chapter 3.4.2 --- Sampling dates --- p.57
Chapter 3.4.3 --- Sample collection and treatment --- p.58
Chapter 3.5 --- Sample analysis --- p.60
Chapter 3.5.1 --- Analysis of sediment samples --- p.61
Chapter 3.5.1.1 --- Sediment texture --- p.61
Chapter 3.5.1.2 --- Sediment pH --- p.61
Chapter 3.5.1.3 --- Redox potential --- p.61
Chapter 3.5.1.4 --- Sediment moisture --- p.62
Chapter 3.5.1.5 --- Organic matter --- p.62
Chapter 3.5.1.6 --- Total Kjeldahl nitrogen --- p.63
Chapter 3.5.1.7 --- "Total Fe, Al, and P" --- p.63
Chapter 3.5.1.8 --- "Oxalate-extractable Fe, Al, and P" --- p.63
Chapter 3.5.2 --- Analysis of water samples --- p.64
Chapter 3.5.2.1 --- "Water pH, conductivity, salinity, turbidity, temperature and DO" --- p.64
Chapter 3.5.2.2 --- Orthophosphate --- p.64
Chapter 3.5.2.3 --- Total nitrogen and phosphorus --- p.65
Chapter 3.5.3 --- Determination of phosphorus exchange characteristics --- p.65
Chapter 3.6 --- Statistical analysis --- p.65
Chapter Chapter Four --- Phosphorus Fractionation in Wetland Sediments in Hong Kong
Chapter 4.1 --- Introduction --- p.67
Chapter 4.2 --- Methodology --- p.68
Chapter 4.2.1 --- Sample collection and analysis --- p.68
Chapter 4.2.2 --- Phosphorus fractionation --- p.69
Chapter 4.2.3 --- Statistical analysis --- p.72
Chapter 4.3 --- Results and discussion --- p.72
Chapter 4.3.1 --- Physico-chemical properties of sediments --- p.72
Chapter 4.3.2 --- Physico-chemical properties of overlying water --- p.78
Chapter 4.3.3 --- Phosphorus fractionation in sediments --- p.82
Chapter 4.3.3.1 --- Phosphorus fractions in sediments of the Hong Kong Wetland Park --- p.82
Chapter 4.3.3.2 --- Phosphorus fractions in sediments of the Mai Po Marshes --- p.89
Chapter 4.3.3.3 --- Phosphorus fractions in relation to mobility and bioavailability --- p.96
Chapter 4.4 --- Conclusions --- p.100
Chapter Chapter Five --- Phosphorus Sorption by Wetland Sediments in Hong Kong
Chapter 5.1 --- Introduction --- p.103
Chapter 5.2 --- Methodology --- p.104
Chapter 5.2.1 --- Sample collection and analysis --- p.104
Chapter 5.2.2 --- Batch incubation experiments --- p.105
Chapter 5.2.3 --- Sorption kinetics --- p.106
Chapter 5.2.4 --- Effects of selected environmental factors on phosphorus sorption --- p.106
Chapter 5.2.5 --- Estimation of sorption parameters --- p.107
Chapter 5.2.6 --- Statistical analysis --- p.109
Chapter 5.3 --- Results and discussion --- p.109
Chapter 5.3.1 --- Phosphorus sorption parameters of wetland sediments --- p.109
Chapter 5.3.1.1 --- Phosphorus adsorption isotherms --- p.109
Chapter 5.3.1.2 --- The role of sediments in phosphate buffering --- p.116
Chapter 5.3.1.3 --- Relationships between phosphorus sorption parameters and physico-chemical properties of sediments --- p.121
Chapter 5.3.2 --- Kinetics of phosphorus adsorption --- p.124
Chapter 5.3.3 --- Effects of environmental factors on phosphorus sorption --- p.128
Chapter 5.3.3.1 --- Effects of pH --- p.128
Chapter 5.3.3.2 --- Effects of salinity --- p.131
Chapter 5.3.3.3 --- Effects of temperature --- p.133
Chapter 5.4 --- Conclusions --- p.136
Chapter Chapter Six --- Phosphorus Flux from Wetland Sediments in Hong Kong
Chapter 6.1 --- Introduction --- p.139
Chapter 6.2 --- Methodology --- p.140
Chapter 6.2.1 --- Sample collection and analysis --- p.140
Chapter 6.2.2 --- Core incubation experiments --- p.141
Chapter 6.2.3 --- Estimation of phosphorus flux --- p.142
Chapter 6.2.4 --- Statistical analysis --- p.142
Chapter 6.3 --- Results and discussion --- p.143
Chapter 6.3.1 --- Phosphorus flux from wetland sediments --- p.143
Chapter 6.3.1.1 --- Phosphorus flux from sediments in the Hong Kong Wetland Park --- p.143
Chapter 6.3.1.2 --- Phosphorus flux from sediments in the Mai Po Marshes --- p.147
Chapter 6.3.2 --- Effects of redox conditions on sediment phosphorus flux --- p.152
Chapter 6.4 --- Conclusions --- p.156
Chapter Chapter Seven --- Conclusion
Chapter 7.1 --- Introduction --- p.159
Chapter 7.2 --- Summary of major findings --- p.159
Chapter 7.3 --- Limitations of study --- p.166
Chapter 7.4 --- Suggestions for future study --- p.166
References --- p.169
46
Herbert, Darrell Anthony. "Primary productivity and resource use in Metrosideros polymorpha forest as influenced by nutrient availability and Hurricane Iniki." Thesis, 1995. http://hdl.handle.net/10125/9272.
47
Majaule, Ugele. "Phosphorous dynamics in soils under contrasting long-term agricultural management practices in the KwaZulu-Natal midlands." Thesis, 2006. http://hdl.handle.net/10413/3457.
Анотація:
Little is known regarding the effects of land use on soil organic matter and P
status of South African soils. For that reason, the effects of the main
agricultural land uses in the midlands region of KwaZulu-Natal [maize (Zea
mays), sugarcane (Saccharum spp), annual ryegrass pasture (Lolium
multiflorum), permanent kikuyu pasture (Pennisetum clandestnum), gum
(Eucalyptus grandis) and pine (Pinus patula)] on soil organic matter content,
microbial biomass C and P and inorganic and organic P pools derived from a
modified Hedley P fractionation was investigated on two sites where the longterm
history of land management was known.
In comparison with undisturbed native grassland, permanent kikuyu pasture
resulted in an increase in organic C, organic P and microbial biomass C and
P. Maize and sugarcane production resulted in a decrease in organic C,
organic P and microbial C and P. Under annual pasture, gum and pine
forests, organic matter and microbial biomass concentrations remained similar
to those under native grassland. Under native grassland, extractable organic
P accounted for 50% or more of the total P content of soils but under
agricultural management with regular applications of fertilizer P, there was an
increase in the percentage of total P present as inorganic P.
Agricultural management greatly affected the distribution of P among the
various inorganic and organic P fractions. Resin-Pi and NaHC03-Pi (the
potentially-available forms of Pi) showed similar trends with land use being
greatly elevated under kikuyu pasture at both sites and sugarcane and maize
at one site. This accumulated Pi was thought to have originated from recent
fertilizer applications and possibly recently mineralized organic P. Trends for
NaOH-Pi with land use differed greatly from those of the Resin- and NaHC03Pi
fractions. Concentrations were notably high under maize and sugarcane
production. Of the pools of soil organic P, the NaHC03-Po fraction was most
greatly affected by land use, being elevated under kikuyu and decreased
under maize and sugarcane. This supports the assertion that it is the
NaHC03-Po fraction that is the most labile soil organic P pool. It was concluded that land use greatly affects soil organic C and P status, soil
microbial biomass C and P contents, soil inorganic P concentrations and the
distribution of P among the various P fractions.
A short-term (8 weeks) laboratory incubation experiment was carried out to
compare the effects of inorganic (KH2P04) and organic (cattle manure, poultry
manure and maize crop residues) sources of P, applied at a rate equivalent to
30 kg P ha-1
, on soil inorganic and organic P fractions and the potential
availability of soil P. Additional treatments consisted of lime [Ca(OHhl at 5 ton
ha-1 and lime plus inorganic P. Applications of lime raised soil pH to a similar
extent after 1, 4 and 8 weeks incubation. After 8 weeks, a small increase in
soil pH was also noted for the cattle and poultry manure and maize residue
treatments. For the inorganic P fractions, substantial treatment effects were
observed only for the Resin-Pi fraction. The inorganic P source was more
effective than the organic ones at increasing Resin-Pi after 1 and 4 weeks
incubation and of the organic sources, cattle and poultry manure were more
effective than maize residues. Resin-Pi concentrations generally increased
between 1 and 4 weeks incubation but then declined rapidly between 4 and 8
weeks incubation. After 8 weeks incubation, treatment effects on Resin-Pi
were small. Concentrations of NaHC03-Pi, dilute HCI-Pi and concentrated
HCI-Pi all declined over the incubation period. There was no clear trend with
incubation for NaOH-Pi although for the poultry manure and maize
treatments, concentrations declined between 4 and 8 weeks incubation. In
general, concentrations of NaHC03-Po were greater for organic than
inorganic P sources after 8 weeks incubation suggesting microbial
immobilization of P in these treatments. There were increases in NaHC03-Po
and concentrated HCI-Po over the incubation period suggesting progressive
immobilization of P from the Pi fractions that declined in concentration during
the incubation. Concentrations of NaOH-Po were not greatly affected by
incubation period. The lime treatments, however, had lower NaOH-Po
concentrations than the others suggesting that liming may have stimulated
microbial mineralization of Po. Residual-P concentrations increased over the
incubation period. This was attributed to conversion of extractable Pi fractions
into recalcitrant, non-extractable Pi forms and/or immobilization of Pinto
intransigent organic forms.Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.
48
Maphoto, Patrina Nare. "Response of growth, yield and root characteristics of a determinate cowpea variety to variable phosphorus fertiliser and lime application rates." Thesis, 2018. http://hdl.handle.net/10386/2243.
Анотація:
Thesis (MSc. Agriculture(Soil Science) -- University of Limpopo, 2018Soil acidity is one of the abiotic stress factors that greatly limit the productivity of crops on farmers’ fields. A greenhouse study was carried out over two summer growing seasons to evaluate the effect of lime and phosphorus (P) application rates on the growth, yield and root attributes of a determinate cowpea variety on acid soil. The experiment was laid out as a 4x5 factorial arrangement with 4 replications. Treatment factors comprised of variable rates of Vaalburg dolomitic lime (0, 2, 4 and 6 t ha-1) and P (0, 15, 30, 45 and 60 kg ha-1) using single super phosphate, 10.5% P. The two treatment factors were combined resulting in a total of 20 treatment combinations. Data collected included cowpea growth parameters, crop phenology, yield attributes and root characteristics. While cowpea plants with no P application consistently gave the least plant height, stem diameter, number and length of trifoliate leaves, the 6 t ha1 lime rate appears to be completely disadvantaged for all measured parameters with generally lower values than in soil filled pots without lime application. Results showed that soil pH was increased with 6 t ha-1 lime application while soil electrical conductivity (EC), percent of organic matter (OM) and total organic carbon (TOC) were all increased with increasing P and lime rates. All measured cowpea growth attributes such as plant height, stem diameter, number of trifoliate leaves, and leaf area were significantly increased (p≤0.05) with increasing P and lime rates. During the two planting seasons, P and lime application resulted in reduced (p≤0.05) duration to flowering, pod formation and physiological maturity. The 6 t ha-1 lime application produced higher number of pods (2.50) compared to the other rates. Application rates of 45 kg P ha-1 and 6 t ha-1 of lime produced superior number of seeds per pod with high values of (13.71) and (12.85), respectively. However, cowpea root attributes namely number of nodules per plant, the third branching root diameter, angle of adventitious root, tap root diameter at 5 and 10 cm, shallow and deep score were significantly increased at moderate P rate of 30 kg P ha-1. Overall, findings of this study revealed that application of both P fertiliser and lime were able to ameliorate the negative effect of P deficiency from soil acidity on the evaluated cowpea variety and promoted increased yield. Keywords: Acid soil, grain cowpea, P fertiliser, lime, growth, root characteristics, yield
National Research Foundation (NRF) and Department of Agriculture, Forestry and Fisheries (DAFF)
49
Leytem, Alicia B. "Response of Striga-susceptible and Striga-resistant sorghum genotypes to soil phosphorus and colonization by an arbuscular mycorrhizal fungus." Thesis, 2012. http://hdl.handle.net/1957/29486.
Анотація:
Striga, a genus of obligate parasitic weeds in the family Orobanchaceae, has been
identified as the most important biological factor limiting agricultural productivity in sub-Saharan Africa. Germination of Striga seeds is triggered by strigolactone root exudates
from host plants. Strigolactones also induce hyphal branching in arbuscular mycorrhizal
(AM) fungi, which are important for plant uptake of phosphorus in low phosphorus soils.
Mechanisms of Striga resistance based on reduced strigolactone production may also
convey resistance to AM fungi which would require higher inputs of phosphorus fertilizer
to attain optimal crop growth. There is evidence for genetic differences in mycorrhizal
responsiveness in other grain crops; therefore it is beneficial for breeders to be aware of
these differences when developing Striga-resistant sorghum cultivars. This research aims
to determine phosphorus and mycorrhizal responsiveness of sorghum genotypes
important for or developed by breeders working on Striga resistance. Phosphorus
response curves were determined for twelve sorghum genotypes using pasteurized low
phosphorus soil amended to achieve four different phosphorus levels. Simple linear
regression was performed on root and shoot dry weight data. Results indicate variability
in phosphorus responsiveness within Striga resistant and susceptible genotypes. Seven of
these genotypes were selected for continued research, which analyzed responsiveness to
phosphorous and differences in mycorrhizal responsiveness in relation to reported
mechanisms of Striga resistance. Treatments included three levels of phosphorus
amendments and the addition of Funneliformis mosseae inoculum. All genotypes were
strongly responsive to P amendment when grown without AM fungi and showed a
decrease in responsiveness to P when inoculated with F. mosseae. Trends for all
genotypes indicate a greater uptake of P, Zn, and Mg by mycorrhizal plants as compared
to nonmycorrhizal plants. All seven genotypes were responsive to mycorrhizae, with a
significant increase in biomass for all genotypes, especially at the lowest phosphorus
level. The responsiveness to the mycorrhizal fungus does not appear to be directly related
to the susceptibility of genotypes to the parasitic weed Striga.Graduation date: 2012
50
Liu, Qianhe. "Rhizosphere processes influencing soil and fertilizer phosphorus availability to Pinus radiata : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, Palmerston North, New Zealand." 2005. http://hdl.handle.net/10179/1669.
Анотація:
Production of Pinus radiata is a major contributor to New Zealand's economy and new plantings are a valuable carbon sink. Phosphorus (P) deficiency and high P fixing capacity of some volcanic ash soils (e.g. Allophanic Soil) may constrain radiata productivity. This thesis investigates the role of ectomycorrhizal (ECM) root processes in the acquisition of P by P. radiata fiom native soil and soil fertilised with two reactive phosphate rock (RPR) fertilisers. The application of finely-divided RPRs to a P deficient Allophanic Soil significantly increased P. radiata seedling growth and P uptake in 10 month pot trials. RPR dissolution was high in this soil, and it was further enhanced by the radiata rhizosphere processes. The development and formation of ECM in radiata seedlings was stimulated by low rates of RPR application but was hindered in unfertilised soils and high rates of RPR application. The P. radiata ECM roots induced acidification and increased oxalate concentration and phosphatase activities in the rhizosphere soil. These changes in rhizosphere biochemical properties were associated with enhanced solubilisation of fertiliser and soil inorganic P and increased mineralisation of organic P, leading to increased P bioavailability in the rhizosphere. ECM inoculation of P. radiata roots with Rhizopogen rubescens and Suillus luteus stimulated production of phosphatase enzymes and oxalate and induced acidification in the rhizosphere. The extent of root-induced changes in the rhizosphere soils was associated with ECM hyphae length density. A technique using pulse labelling of radiata shoots with 14CO2 showed promise in estimating the active ECM hyphae density. The 14C activity was highly correlated with ECM hyphae density measured by an agar film technique. Overall, observations made in this thesis indicate that sparingly soluble forms of organic and inorganic P in soils low in plant-available P are readily solubilised and utilised for P. radiata growth through ECM rhizosphere processes.