Tandra Fraser

Tandra Fraser

Ph.D. Candidate

Thesis topic:  Role of soil bacterial communities in phosphorus cycling and bioavailability in agroecosystems.

Changes in land management practices may have significant implications for soil microbial communities important in phosphorous (P) cycling.  Soil bacteria can increase P bioavailability through excretion of phosphatase enzymes, which catalyze the hydrolysis of ester-phosphate bonds.  Phosphatase enzymes have a key role in P cycling yet little is known about the phylogenetic distribution and abundance of genes encoding these enzymes in soil and how they are affected by management practices.  Advances in molecular biology and the design of primers for prokaryotic bacteria with the genetic potential for production of alkaline phosphatase may provide insight into the biological cycling of organic P (Po). 

The aim of my research is to determine the effect of long-term management on P bioavailability in the Canadian Prairie region, focusing on organic production.  Low inorganic P (Pi) has been reported in organically managed soils across the Canadian Prairie region.  Replacement of P is especially challenging in these systems since limited options are available under organic certification, making the turnover of Po essential.  

Objectives:
1. Examine differences in soil P bioavailability and P sorption capacity in a long-term forage-grain rotation and compare between soils under organic (ORG), compost amended organic (ORG-M), conventional (CON) and prairie (PRA) management.
2. Determine the relationship between available P, plant P uptake and final yields.
3. Examine the influence of management system on and alkaline phosphatase (ALP) activity.
4. Evaluate the influence of long-term organic systems and periodic manure application on the abundance and diversity of ALP gene harbouring bacteria and relate to ALP activity, plant P availability and P uptake.