Germida: Nitrogen Fixing Rhizobacteria as Biofertilizers for Canada
Date: March 1998
Term: 3 years
Status: Completed
Researchers: Dr. Jim Germida and Dr. J. de Freitas, Department of Soil Science, University of Saskatchewan
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: n/a
Project Summary
Nitrogen fertilizer is one of the most important external inputs for improving crop growth and yields. Researchers were interested in finding biological alternatives that could optimize and/or replace N-fertilizers, and in 1996 a three-year project was initiated at the University of Saskatchewan to isolate rhizobacteria able to fix atmospheric nitrogen for canola. In three integrated growth chamber and field trials, researchers screened 800 isolates, established a collection of 37 nitrogen-fixing rhizobacteria isolates and identified three promising diaxotrophic bacteria. In the field trial, one Bacillus polymyxa RSN17 strain proved to be the promising diazotroph rhizobacteria that could be economically important for canola growers.
For canola growers, nitrogen fertilizers are one of the most important external inputs for improving crop growth and yields. Researchers were interested in finding biological alternatives that could optimize and/or replace N-fertilizers. Rhizobacteria living in the vicinity of plant roots (rhizosphere) were thought to benefit plant development, so researchers were interested in finding out if specific bacteria isolated from canola rhizosphere might be used as seed-applied inoculants to enhance plant growth and yield of canola through nitrogen fixation.
Researchers at the University of Saskatchewan conducted a three-year project in 1995 and 1997 to isolate rhizobacteria able to fix atmospheric nitrogen for canola. The objective of the project was to assess the potential use of nitrogen-fixing bacterial inoculants to promote canola growth and reduce dependency on N-fertilizers. Three integrated growth chamber and field studies were conducted to: isolate, characterize and assess bacteria found in the rhizosphere as nitrogen-fixing rhizobacteria collected from three sites in Saskatchewan, Bellevue, Allan and Watrous; to validate candidate diazotrophic bacteria strains in growth chamber assays; and to develop a suitable method for introduction and establishment in canola fields.
The results obtained from this research project indicated that nitrogen-fixing bacteria were active members of the bacteria community in canola fields and could be readily isolated from several parts of canola plants and rhizosphere soil. Over 800 isolates obtained from canola plants were screened for nitrogen-fixing activity associated with canola, with only about 5% of the isolates showing nitrogen-fixing ability. In the second growth chamber trial, a collection of 37 nitrogen-fixing rhizobacteria isolates were established. The most promising diaxotrophic bacteria of the collection were two Bacillus polymyxa strains (ES600A and RSN17) and one Xanthomonas-maltophila strain RSC466A. When tested, these three diazotrophs promoted significant accumulation of N in the shoots of canola plants, suggesting that the quantity of nitrogen fixed by these rhizobacteria could be significant.
Researchers then conducted a small-plot field study to assess the ability of these three strains to enhance the growth and yields of canola (var. Legend) through nitrogen fixation. Although overall the results showed neutral and/or no significant effects on canola grain yield, seed inoculation with B. polymyza-RSN17 produced a grain yield increase of approximately 20% compared to uninoculated controls. Therefore, B. polymyza-RSN17 strain constitutes a promising diazotroph rhizobacteria that could be economically important for canola growers.
Full Report PDF: Nitrogen Fixing Rhizobacteria as Biofertilizers for Canada