Advanced N management for canola, wheat and soybean: Evaluation of a new biological for N-fixation in non-legumes
Researcher(s): Diane Knight, University of Saskatchewan; Richard Farrell, University of Saskatchewan
Term: 4 years, completed Feb 2023
Status: Complete
SaskCanola Investment: $64,993
Total Project Cost: $129,985
Funding Partners: WGRF
*Special mention to Dr. Sean Hemmingsen, NRC- Saskatoon, for his contributions to this project as well.
Grower Benefits
Evaluation of EnvitaTM showed many of the root and shoot tissues tested positive for Gluconacetobacter diazotrophicus colonization, but most did not show strong evidence nitrogen (N) fixation. In many cases, the %N in the plants that were colonized was lower than the control (not inoculated) plants.
Foliar application was a successful delivery method compared to direct seed inoculation, but was less effective than inoculation at germination, which was also the least practical method.
Unfortunately, the results for canola were the most inconsistent, and more work is needed on improving the method of delivery of the inoculant and stimulating the inoculant bacteria to fix N.
Project Summary
The environmental impact of crop production has become a critical aspect of market access and crops produced with a low carbon footprint have a competitive advantage in the global marketplace. Nitrous oxide (N2O) emissions constitute a key sustainability indicator, and are important in the overall carbon (and nitrogen) footprint of a cropping system. Nitrogen in soil can be converted to N2O – a potent greenhouse gas contributing to climate change – especially when soil N is in excess of the crop’s requirement, as is often the case when fertilizer N is applied. Cost effective practices and products that help synchronize the supply of N with the crop’s demand for N will reduce the amount of N lost from a system and hence the amount needed to produce a crop and could go a long way to reducing negative environmental impacts.
There are many species of microorganisms that exist in nature that are capable of N fixation, including Gluconacetobacter diazotrophicus (now marketed as Envita™). Unlike the rhizobia that colonize the roots of legume plants, G. diazotrophicus is a free-living organism that does not require the presence of a host plant. However it often lives inside of plant tissues and evidence exists that it can fix atmospheric N to supply N to the associated plants to improve yield. The product has had success in crops like corn in the United States, but very little data exists on how it performs in western Canada.
In this project, Envita™ was tested for its ability to fix N in canola, wheat and soybean in a controlled environment. The main goal for this project was to inoculate the selected crop with Envita™ and then evaluate if the inoculated crops were acquiring N fixed by the G. diazotrophicus. 15N2 gas (labelled N for tracing into the plant tissue) was supplied to the atmosphere surrounding the plants and the plants analyzed for 15N content. Three methods of introducing G. diazotrophicus to the plant were evaluated including: 1) direct seed inoculation, 2) inoculation at germination and 3) foliar application. Treatments included no inoculant, Envita™ and heat-killed Envita™. The heat-killed treatment was included to provide a control to evaluate if the Envita™ formulation affects the 15N signal independently of the inoculant organism. Because the product was received as a dry powder, it was reconstituted with non-chlorinated, deionized water. Prior to inoculation, all of the seeds were sterilized using different protocols to achieve sterility but not compromise the seed or germination.
For the direct seed inoculation, the sterilized seeds were soaked in the reconstituted Envita™ for 10 minutes before being incubated at room temperature in a dark cabinet overnight. For seed inoculation during germination, seeds were placed onto filter paper wetted with Envita™. These were stored in a dark cabinet at room temperature for 5-7 days. Following that, five germinated seedlings were transplanted in a Leonard jar (a semi-sterile, soil-less system for growing plants) or into a pot with soil. The foliar application was a spray onto the leaves at the 2-4 leaf stage with the reconstituted Envita™ solution combined with a non-ionic surfactant.
Envita™ was able to deliver G.diazotrophicus bacteria to roots and shoots of wheat, canola and soybeans, and the bacteria could colonize the tissues in most, but not all cases. However, the presence of G.diazotrophicus in the plant tissues did not always translate into 15N2 being fixed into the plant tissues. In terms of getting G.diazotrophicus into the plant tissues, the inoculation at germination method had the most positive tests followed by foliar application and direct seed inoculation. Unfortunately, application at germination is the least practical method for farmers to use, even with changes for field scale use.
Results for canola were the most inconsistent among the three crop types. All of the plants inoculated at germination showed some slight 15N enrichment in the roots and shoots, but not all tested positive for G.diazotrophicus colonization. Even though 15N enrichment indicates the transfer of 15N fixed by some means to the canola plants, there were not consistently higher percentages of N in the tissues, nor did the plants produce more biomass.
The presence of the introduced G. diazotrophicus organism in some of the tissues tested is encouraging, but further work is need to improve colonization efficacy and to determine how to trigger the organism to fix N after it has colonized.
Other References to this Research Project
SaskCanola’s On-Farm research protocol for 2023 focuses on nitrogen fixing biologicals on canola. Find out more: On-Farm & Field-Scale Research.