Enhancing soil quality, plant health, and disease management in organic production with Brassica cover crops used as biofumigants

Final Report Submitted to the Ceres Trust Organic Research Initiative
September 07, 2014

  • Professor: Mathieu Ngouajio, PhD · Michigan State University – Department of Horticulture
  • Assistant Professor: Jianjun Hao · Department of Plant, Soil and Microbial Sciences
  • Organic Extension Specialist: Vicki Morrone · Department of CARRS
  • Technician: Drey Clark · Department of Horticulture
  • Postdoctoral Research Associate: Noah Rosenzweig · Department of Plant, Soil and Microbial Sciences
  • Graduate Student: Aaron Yoder · Department of Horticulture

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Brassica cover crops are cool season species that fit nicely into many crop rotation systems, especially where there is a short growing season (as in the North Central region of the U.S.). These cover crops produce natural antimicrobial compounds (glucosinolates) that suppress soilborne pathogens and weeds, and they have been shown to change soil biology through selective activity on specific soil microorganisms. Unfortunately, their performance has been inconsistent, and can be negative, with several extreme cases of 100% crop-stand reduction. To better understand the cover crops’ impact in organic production systems, studies were conducted at an MSU research field and Michigan organic farmer’s field to (1) Determine the role of native soil biology of the Brassica cover crops and subsequent cash crop performances, (2) Determine the role of allelopathy (plant growth inhibition due to natural compounds produced by the cover crops) on the performance of Brassica cover crops in cropping systems and identify safe plant back periods for susceptible crops, (3) Determine the change in populations of major soilborne pathogens and soil microbial activity following Brassica biofumigation, (4) Quantify the nutrient cycling potential of Brassica cover crops for use in crop nutrient management programs, and (5) Deliver the results and observations to growers through extension activities.

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