Bringing the Benefits of Legume Cover Crops to Northern Midwest Climates

Project Overview

Project Type: Research and Education
Funds awarded in 2014: $114,497.00
Projected End Date: 01/31/2019
Grant Recipient: University of Minnesota
Region: North Central
State: Minnesota
Project Coordinator:
Dr. Julie Grossman
University of Minnesota

Annual Reports


  • Agronomic: corn
  • Vegetables: sweet corn


  • Crop Production: cover crops, organic fertilizers
  • Production Systems: organic agriculture
  • Soil Management: green manures, organic matter, soil microbiology, soil quality/health
  • Sustainable Communities: urban agriculture

    Proposal abstract:

    The purpose of this project is to provide legume cover crop options to growers in the upper Midwest by examining a key soil microbial processes that regulates nitrogen (N) cycling in select winter-hardy legumes, and by designing an innovative set of educational tools showcasing exemplary farmers who successfully utilize legume cover crops in colder climates, or face challenges in doing so. Case studies will be designed in collaboration with the Midwest Cover Crop Council and the Minnesota Institute for Sustainable Agriculture. The information we propose to gather is specifically tailored to answer questions generated by farmers at national and regional workshops related to legume cover crops. Through such workshops we have learned that growers are eager to understand functioning of the belowground soil community responsible for making nitrogen available to crops, including both symbiotic nitrogen-fixing rhizobia bacteria. Competitive indigenous populations of rhizobia present in farm soils have been shown in many regions to impact the success of rhizobia inoculants added at legume planting. Since rhizobia are present in almost all soils, we hypothesize that legumes may form relationships with indigenous rhizobia that may affect nitrogen fixation rates, either increasing or decreasing its performance. To this end, our activities include 1) conducting in-depth interviews with 4-8 exemplary organic growers who successfully use legume cover crops and developing media-rich interactive case studies for educational use; 2) assessing nitrogen-fixation effectiveness of native soil nitrogen-fixing bacteria (rhizobia), and 3) extending our findings to growers in the upper Midwest via two workshops and University of Minnesota courses designed to jointly educate upper Midwest organic growers and students about soil microbial N-cycling processes in sustainable agriculture. We will develop a replicated field experiment at two on-farm locations and one UMN research station assessing the five legume cover crop species or mixes, and three inoculation treatments. Inoculation treatments will include 1) No inoculation, 2) organic fertilizer application (i.e., pelleted chicken litter) + inoculation, and 3) inoculation with the recommended commercial rhizobia inoculant strain. Legume productivity and nitrogen-fixation via stable isotope 15N natural abundance methods will be assessed, and rhizobia bacteria isolated from root nodules to determine genetic diversity and efficiency using state-of-the-art molecular methods. Each of our activities is intrinsically linked to grower and student learning and action outcomes.

    Project objectives from proposal:

    Learning outcome 1: Growers will learn if application of nitrogen fixing rhizobia inoculant is necessary with selected cover crop ecotypes. We will characterize nodule occupants among the cover crop varieties in Y1. Mature plants will then be evaluated for nodulation, total biomass N, nitrogen fixed, and rhizobia occupancy.


    Learning outcome 2:  Growers will learn basic soil ecological principles to help them manage legume cover crops for optimal function and performance. Blending farmer needs with available data on cover crop biology and soil science, we will develop two hands-on workshops including evidence-based responses to grower knowledge needs. Workshops will be taught as part of grower conferences in the region (i.e. MOSES, Sustainable Farming Association of Minnesota Annual Conference) in the final year of the project. 


    Action outcome 1:  At least 25 farmers will plan to use a legume cover crop in their farming operation in the three years following project termination. To conduct the formative evaluation, surveys will be provided to workshop attendees and undergraduate course attendees that ask about the degree to which these offerings were useful, met their needs, and what additional questions they still have. Additionally, in the months following the workshops, attendees will again be surveyed and asked to rate their knowledge about utilizing cover crops and the degree to which they are utilizing (farmers) or recommending (those who work with farmers) such practices. Those farmers who identify having most successfully implemented these approaches will be interviewed by phone to understand how and why they were able to engage in these practices. (i.e., what were drivers of their success).


    Action outcome 2: At least 60 students will be exposed to examples of legume cover crop use. To meet this action outcome we will develop 4-8 media-rich online case studies showcasing exemplary growers who use cover crops in the North Central SARE region, and highlighting both their successes and challenges in using cover crops. Dr. Grossman will be leading a course in biological principles for use in organic farm management as part of the University of Minnesota’s recently developed Food Systems major, and the development of the case studies dovetails beautifully with this new and innovative program. The case studies will be developed as a course assignment for Dr. Grossman’s class in Y1 and Y2 of the grant, with students conducting all interviews, taking video footage, editing, and developing study questions to be part of the case-study package.



    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.