Phosphorus and phytoplankton dynamics in freshwater are usually thought to be tightly coupled and interdependent, yet orthophosphate uptake in situ has been observed to be mediated largely by particles of bacterial size. The purpose of this thesis is to examine the general hypothesis that freshwater bacterioplankton are markedly superior competitors for phosphorus, relative to the phytoplankton. Using isolates of three species of pelagic bacteria, and two of algae, it was shown that the bacteria possess much higher affinity orthophosphate uptake kinetics than the algae. In a Monte Carlo simulation study, the accuracy and precision of these Michaelis-Menten parameter estimates were found to depend strongly upon the experimental design matrix. Bacterial superiority in uptake was also reflected in terms of growth, in chemostat competition experiments, which also showed algal and bacterial uptake of orthophosphate to be well correlated with their relative long-term phosphorus assimilation. In parallel experiments in situ, bacterioplankton were found invariably to be responsible for more than 97% of the orthophosphate uptake. In contrast, excreted organic phosphorus was utilised almost exclusively by the phytoplankton. There is little evidence as yet that excretion and reuptake of phosphorus is important in redistributing phosphorus among the plankton.

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).

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.

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.

No description available.

Hydrolysis and adsorption-desorption reaction of pyrophosphate (PP) and orthophosphate (OP) were studied in two Quebec soils (St. Bernard and Dalhousie) and three minerals (goethite, kaolinite, and montmorillonite). Soil and soil mineral samples were fractionated by size into two separates. / Soil and goethite samples adsorbed more OP than PP whereas kaolinite and montmorillonite adsorbed similar amounts of OP and PP. Pyrophosphate and orthophosphate adsorption was found to be related significantly to extractable Fe. Furthermore, kaolinite and montmorillonite desorbed similar amounts of OP and PP whereas more OP than PP was desorbed from soil and goethite samples. Moreover, adsorption of OP and PP was found to be mainly chemical adsorption. Smaller particle size induced higher P adsorption and desorption from both P sources compared with the coarse particle size. / Goethite samples had slower rates of hydrolysis compared to soil and clay mineral samples. Furthermore, kalolinite and montmorillonite did not increase the rate of PP hydrolysis even with reduced adsorption of PP compared to soil and goethite samples. Chemical hydrolysis was found to be a significant portion of the total hydrolysis. Smaller particle size and high PP adsorption induced smaller PP hydrolysis than with coarse particles. Moreover, added OP reduced the amount of PP remaining nonhydrolyzed. First-order rates of PP hydrolysis were faster in nonautoclaved than autoclaved samples. Rate of PP hydrolysis increased with increased temperature and the effect of temperature was more obvious in the autoclaved than nonautoclaved samples.

No description available.

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

No description available.

Man-made mixing in shallow lakes will resuspend bottom sediments and increase phosphorus concentration in the water body. The increase in phosphorus content may affect the lake productivity. During the course of this study, a better understanding of the water-sediment-phosphorus relationships of some shallow lakes in Central Florida was attempted. Column studies and batch experiments were used to investigate the effect of mechanical mixing on the release of phosphorus from bottom sediments collected from Lake Claire and Jessup. The particle size distribution and density distribution of the bottom sediments were studied and the release of phosphorus from each fraction was measured. The results indicated that dissolved oxygen, turbidity and phosphorus content in the water column increased by mechanical agitation. The total phosphorus released from smaller size particles seemed to be higher than phosphorus released from larger particles. Also, the least and highest density sediment particles showed the highest release of phosphorus.