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Understanding Biological Contributions to Phosphorus Availability in Organic Dairy Farm Soils

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dc.contributor.advisor Voroney, R. Paul
dc.contributor.advisor Lynch, Derek Schneider, Kimberley D. 2014-09-10T16:45:52Z 2014-09-10T16:45:52Z 2014-09 2014-09-05 2014-09-10
dc.description.abstract Recent studies exploring soil phosphorus (P) fertility on dairy farms under organic management in Canada have reported low concentrations of Olsen soil test P (STP), yet the impact on crop productivity is not clear. In this thesis, soil biological and biochemical properties relating to plant P availability in perennial forage fields (Medicago sativa / Phleum pratense) of three paired organic and conventional dairy farms in southwestern Ontario, Canada were compared. Molecular approaches (PCR-DGGE and quantitative real-time PCR) were used to explore arbuscular mycorrhizal fungi (AMF) communities in these soils. Finally, an incubation experiment using the radioisotope 33P was conducted to assess biological P fluxes and microbial P uptake in select forage soils along a gradient of STP concentrations. Results of the field study found no significant differences between forage yields on organically versus conventionally managed fields, and forage yield was not correlated with STP. Plant tissue P concentrations supported that plant-available P was greater under conventional management; however organic tissue P concentrations were not lower than critical concentrations. Solution 31P NMR-spectroscopy revealed a greater organic P (Po): inorganic P (Pi) ratio and greater proportions of orthophosphate diesters in NaOH-EDTA soil extracts from organically managed systems. Mean AMF root colonization of alfalfa was also greater under organic management (37%) compared with conventional management (23%). AMF community composition was found to differ between management systems; the data indicated that organic systems may support AMF communities that promote greater host-plant P-use efficiencies. In the 33P incubation experiment gross Po mineralization contributed a mean of 35% of the total isotopically-exchangeable P after 8 days. Significant uptake of solution Pi by the microbial biomass occurred in 8 days, with 11/16 soils having greater than 20% of the initially added 33P in the microbial biomass. The proportion of 33P found in the microbial P pool was negatively related to solution P¬¬i concentrations. This research supports the importance biological processes to soil P dynamics in organic farming systems. These relevant processes need to be considered when assessing P availability in agricultural systems, which would ultimately aid in the greater goal of achieving P-use efficiency in agriculture. en_US
dc.description.sponsorship NSERC (Natural Sciences and Engineering Research Council), OMAFRA (Ontario Ministry of Agriculture, Food and Rural Affairs), Canada Research Chairs Program, Swiss Federal Institute of Technology Zurich (ETH Zurich), AAFC (Agriculture and Agri-Food Canada) en_US
dc.language.iso en en_US
dc.subject phosphorus availability en_US
dc.subject arbuscular mycorrhizal fungi en_US
dc.subject organic agriculture en_US
dc.subject forages en_US
dc.subject organic phosphorus mineralization en_US
dc.subject alfalfa en_US
dc.subject soil test phosphorus en_US
dc.subject organic phosphorus en_US
dc.subject nuclear magnetic resonance spectroscopy en_US
dc.subject NMR en_US
dc.subject PCR-DGGE en_US
dc.subject qPCR en_US
dc.subject isotopic dilution en_US
dc.subject microbial P uptake en_US
dc.subject microbial P cycling en_US
dc.subject microbial P turnover en_US
dc.subject P-use efficiency en_US
dc.subject Funneliformis mosseae en_US
dc.subject Claroideoglomus claroideum en_US
dc.subject Diversispora celata en_US
dc.subject arbuscular mycorrhizal symbiosis en_US
dc.subject AMF en_US
dc.subject AM symbiosis en_US
dc.subject AMF root colonization en_US
dc.title Understanding Biological Contributions to Phosphorus Availability in Organic Dairy Farm Soils en_US
dc.type Thesis en_US Environmental Sciences en_US Doctor of Philosophy en_US School of Environmental Sciences en_US
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