Source: UNIVERSITY OF ILLINOIS submitted to
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
Funding Source
Reporting Frequency
Accession No.
Grant No.
Project No.
Proposal No.
Multistate No.
Program Code
Project Start Date
Oct 1, 2021
Project End Date
Sep 30, 2024
Grant Year
Project Director
Mulvaney, R. L.
Recipient Organization
2001 S. Lincoln Ave.
Performing Department
Natl. Resources and Env. Sci.
Non Technical Summary
Escalating concerns over food safety and environmental protection have substantially increased consumer demand for organic products. However, these products are often in short supply due to the limited land area under organic production, and also because crop yields tend to be lower than for conventional agriculture. The importance of symbiotic dinitrogen (N2) fixation is readily apparent from the widespread use of legume rotations in organic systems, whereas very little attention has been given to non-symbiotic fixation by free-living bacteria. The latter process would be favored for these systems by the absence of synthetic nitrogen and by frequent cover-cropping that improves soil structure and augments the input of carbon from roots and residues.In the present project, a novel approach will be utilized to assess the diversity (targeted gene sequencing) and abundance (qPCR analysis) of free-living bacteria, along with their functional capacity (15N2 fixation), for a well-established organic rotation. Based on previous investigations documenting the importance of a neutral to alkaline soils with adequate calcium availability, a comparison will be made of microbial communities and free-living N2 fixation (FLNF) with and without certified organic limestone and gypsum amendments. This project addresses all three goals of the Soil Health Program Area, and has potential to provide a simple and cost-effective means to reduce nitrogen limitation in organic production systems. There are implications for enhancing economic profitability for producers, improving the commercial availability of organic products, and protecting air, soil, and water quality.
Animal Health Component
Research Effort Categories

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships;

Subject Of Investigation
0110 - Soil;

Field Of Science
1060 - Biology (whole systems);
Goals / Objectives
Goals:1. Advance scientific understanding of asymbiotic dinitrogen fixation in organic production systems.2. Improve or maintain soil health, sustainability, and productivity in organic production systems.Objectives:1. Modify and optimize the 15N2 assay method of Smercina et al. (2019) for estimating free-living N2 fixation (FLNF) in rhizospheric soil, with (potential) or without (baseline) the use of a C cocktail, relative to:1a. Incubation period; and1b. C cocktail composition.2. Compare different phases of organic rotation regarding:2a. Diazotrophic abundance and diversity using targeted genes for N2 fixation, nitrification, denitrification, and mineralization; and2b. Functional capacity of FLNF assayed using 15N2.3. Ascertain the potential of liming and the use of gypsum for increasing FLNF under organic management with respect to:3a. The abundance and composition of functional genes targeting N-cycle genes;3b. 15N2-measurements of potential and baseline (no C cocktail) FLNF; and3c. Cereal yields and N accumulation.
Project Methods
Objective 1 will be addressed by modifying and optimizing the 15N2 assay method of Smercina et al. (2019) for estimating free-living nitrogen fixation (FLNF) in rhizospheric soil with (potential) or without (baseline) the use of a C cocktail, relative to incubation period; and C cocktail composition. For Objective 2, a comparison will be made of different phases of organic rotation regarding (a) diazotrophic abundance and diversity using targeted genes for major N-cycle processes; and (b) functional capacity for FLNF assayed using 15N2. The same approach used for Objective 2, will be combined with measurements of cereal yields and N accumulation to investigate the potential of liming and the use of gypsum for increasing FLNF under organic management (Objective 3).

Progress 10/01/21 to 09/30/22

Target Audience: Nothing Reported Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Training ingas handling techniques for use with the protocol developed has been provided to the postdoctoral associate and a new MS student supported by the project. How have the results been disseminated to communities of interest?A press release regarding the current project was post by the College of ACES at the University of Illinois and is available at: What do you plan to do during the next reporting period to accomplish the goals?The protocol for estimating asymbiotic N2 fixation will be completed and employed with soil samples collected during the 2023 growing season. Soil samples will becollected periodicallyfor microbial community analysis, and measurements will be made ofgrain yield and cropN accumulation.

What was accomplished under these goals? Regarding Objective 1, a new protocol is under development that involves circulation of labeled 15N2 through a desiccator contaning bulk or rhizospheric soil samples. Current work is focused on optmization of the carbon source, incubation period, and soil moisture content for estimating potential N2 fixation. Following the project timetable for Objectives 2 and 3, subplots were stablished, georeferenced, and amended with gypsum and or limestone as detailed in the proposal.