A farm survey of phosphorus in bulk and rhizosphere soil of organically managed soybean plots across Prince Edward Island, Canada

T. D. Fraser1, D. H. Lynch2 and K. E. Dunfield1


Widespread phosphorus shortages have been reported in organically managed soils across Canada. As certified organic acreage continues to increase, optimising soil P fertility becomes increasingly important. Since plant available orthophosphate fertilizer is not approved in organic production, a detailed understanding of P cycling is essential.

Soybeans fields under organic management were sampled at twelve locations throughout Prince Edward Island, Canada during the 2010 growing season. At soybean pod initiation, composite soil samples were collected (n=20) and nine soybean plants taken from each plot with the roots and shoots separated. The rhizosphere soil, defined as soil adhering to roots after shaking, was collected for soil test P (Mehlich 3 extraction) and acid phosphatase analysis.

Preliminary results indicate higher STP and phosphatase activity in the rhizosphere compared to the bulk soil. Results from plant P uptake and total organic and inorganic P will also be discussed. Sampling will be continued in 2011
combined with greenhouse studies to intensively study changes in P forms over the life cycle of the plant. Relative abundance and diversity of active bacterial communities as related to changes in P will be investigated using 16S rRNA DGGE and real-time PCR.


Poster presentation at Plant Canada Conference. Saint Mary's University, Halifax, NS. July 17-21, 2011

Author Locations and Affiliations

(1) School of Environmental Science, University of Guelph, Ontario, Canada N1H 2W1
(2) Department of Plant and Animal Sciences, Nova Scotia Agricultural College, Truro, Nova Scotia, Canada B2N 5E3
* Corresponding author, E-mail tandra@uoguelph.ca

Posted May 2012