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OSC Activity A.1

Characterizing soil phosphorus dynamics and availability under organic crop production

Activity Researchers

Name Affiliation
Derek Lynch, Lead Researcher
derek.lynch@dal.ca

Canada Research Chair in Organic Agriculture
Dalhousie University
Faculty of Agriculture
PO Box 550
Truro, NS B2N 5E3

Diane Knight, Co-applicant
diane.knight@usask.ca

Associate Professor
Department of Soil Science
University of Saskatchewan
5E82-51 Campus Drive
Saskatoon, SK S7N 5A8

Chantal Hamel, Co-applicant
hamelc@agr.gc.ca

Research Scientist
Agriculture and Agri-Food Canada
Semiarid Prairie Agricultural Research Centre
PO Box 1030
Swift Current, SK S9H 3X2
Paul Voroney, Co-applicant
pvoroney@uoguelph.ca

Professor
Land Resource Science
University of Guelph
Guelph, ON N1G 2W1

Objectives

  1. To characterize soil phosphorus dynamics and availability under organic crop production and relationship to yield and P uptake, specifically
    • To examine soil N and P cycling under both annual and perennial legume-based systems under organic management.
    • Characterize the relative influence of legumes and organic amendments on soil organic and labile P fractions and crop P uptake.
    • Characterize the species richness, and contribution of native AM fungi to legume crop P nutrition and productivity based and crop management practices.
  2. To develop recommendations for improved practices to enhance soil fertility and P availability in organic production systems and contribute to a refined model or soil test for farm-level monitoring of P availability on organic farms.

Activity Summary

Canadian organic farmers have identified promoting biologically-based soil fertility management strategies under legume-based crop production systems as a high research priority. In a recent (OACC, 2009) survey of Canadian organic farmers, their top six research priorities were research focused on (i) soil fertility and crop rotations (ii) consumer education on organic system benefits (iii) beneficial rotations for specific problems and (iv,v,vi) rotation impact on soil quality, ecological interactions and soil life. However, recent research has raised concerns about potential depletion of soil phosphorus across organic production systems nationally. Organic cropping systems change both the quantity, distribution and quality of soil organic matter, but studies are lacking that have examined how contrasting cropping systems affect crop performance, soil quality, microbial processes, and soil phosphorus dynamics. Organic crop rotations range from forage or green manure-based systems with several years of perennial legumes in rotation to annual cropping sequences often including grain legumes. Inadequate plant available soil P can in turn lead to poor legume nodulation, low biological nitrogen fixation, and reduced forage or green manure growth.

This project directly addresses these priorities by characterizing the contributions of soil organic and inorganic phosphorus pools, and biologically mediated phosphorus turnover, to crop P (and N) availability as a function of soil type, and organic field crop management regime.  Multi-site, multi-year sampling of soil and crop at research sites and commercial organic farm sites throughout Prairie regions and eastern Canada will be conducted to characterize the relationship between rotation sequence, tillage intensity, crop residue management, fertility management, soil parent material and type, soil profile organic and inorganic P fractions and indices of P fertility status, including microbial biomass P, phosphatase activity, mycorrhizal colonization and effectiveness, and crop yield and P (and N) uptake. 

Sub-Projects will include:

  1. Examination of soil N and P cycling under both annual and perennial legume-based systems under organic management.
  2. Characterization of the relative influence of legumes and organic amendments on soil organic and labile P fractions and crop P uptake.
  3. Characterization of the species richness, and contribution of native AM fungi to legume crop P nutrition and productivity based on crop management practices

Combined with linked science cluster projects targeting AMF effectiveness and P availability under wheat, the goal is to develop recommendations for improved practices to enhance soil fertility and P availability in organic production systems and contribute to a refined model or soil test for farm-level monitoring of P availability on organic farms.

Background and Supporting Documents