Cover Crop Cold Tolerance for High Tunnels

Project Overview

Project Type: Graduate Student
Funds awarded in 2016: $10,875.00
Projected End Date: 12/31/2017
Grant Recipient: University of Minnesota
Region: North Central
State: Minnesota
Graduate Student:
Faculty Advisor:
Dr. Julie Grossman
University of Minnesota


Not commodity specific


  • Crop Production: cover crops, nutrient cycling, tissue analysis
  • Production Systems: general crop production
  • Soil Management: green manures


    High tunnels are a very popular tool, particularly among organic and sustainable farmers, used to extend the growing season. In addition to a longer growing season, high tunnels also increase both yield and quality of many fruits, vegetables, and flowers. However, high tunnel environments face particular soil health challenges due to a longer, more intensive season, irrigation under dry conditions, and increased heat. Legume cover crops can help address some of these challenges through addition of organic matter and biological nitrogen fixation. For growers in cold climates who do not grow crops in high tunnels through the winter, the late fall-early spring window is a possible time to include cover crops in high tunnel rotations. However, prior field observations found very low survival of cover crops in high tunnels in Minnesota, and high temperature fluctuations were hypothesized as a potential reason.

    To address this question, a controlled environment freezing study was designed to evaluate hairy vetch and red clover plants at different freezing temperatures after being exposed to conditions that mimicked high tunnel conditions and those used in conventional freezing studies. The results of this study showed that the high tunnel conditions increased freezing tolerance of both red clover and hairy vetch compared to the conventional cold acclimation conditions. This suggests that temperature fluctuations seen in high tunnels do not reduce freezing tolerance.

    Project objectives:

    1. Evaluate freezing tolerance of two common legume cover crops, red clover and hairy vetch, for high tunnel environments
    2. Assess freezing temperature effect on cover crop biomass and percent nitrogen
    3. Provide basic information about freezing tolerance of red clover and hairy vetch to farmers who are interested in using these legumes as winter annual cover crops in high tunnels
    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.