Database Research Summaries
Potential use of cover crops and green manures 1

calendar_today Year of Research: 2018
update Posted On: 05/23/2019
group Leonor Leandro (Principal Investigator, Iowa State University); Daren Mueller (Co-Investigator, Iowa State University)
bookmark Iowa Soybean Association

Research Focus

The focus of this project is to investigate how cover crops affect disease development in greenhouse and field conditions.


  • Evaluate the effect of cover crops and green manures on SDS, Fusarium root rot, white mold and iron deficiency chlorosis in field conditions.
  • Identify simple, rapid, and cost-­-effective bioassays to test efficacy of additional cover crop species on disease suppression in controlled environment conditions.
  • Identify cover crops with the most potential for inhibiting pathogen growth and sporulation in vitro and survival in soil.


  1. The experimental design for all 2018 trials consists of two cover crop treatments: 1) spring oats planted as a companion crop with soybeans and terminated at V3-V4, and 2) no oats. These treatments will be tested on two or three varieties with difference levels of susceptibility to each disease. Several of these sites will also be used to establish fall cover crops (oats and rye) to be tested for effects in disease development during the 2019 season.
  2. We have conducted a greenhouse experiment to test the ability of different cover crop amendments on suppression of SDS, caused by Fusairum virguliforme, and root rot caused by F. graminearum. Rye, oat, alfalfa, clover and corn plants were grown in the greenhouse for approximately 6 weeks. The roots and shoots of these plants were then cut into small pieces and incorporated into pasteurized sand-soil mix. Due to an infestation with fungal gnats in the soil, the data from this experiment was inconclusive, as the fungal gnats damaged the roots and consumed much of the fungal inoculum.
  3. We conducted a preliminary experiment to optimize protocols to test the effects of cover crops on pathogen growth and sporulation. Oat plants were grown in the greenhouse for 5 weeks. The roots and shoots were then macerated and the slurry was filtered to obtain a liquid oat extract. Culture media (PDA) was amended with the extract and allowed to solidify in petri dishes. Placing a plug of fungal colony on 6 replicate plates, and incubating the plates for 6 days tested the effect of the different media on F. virguliforme and F. graminearum. Preliminary results suggest that the oat extracts stimulated growth of F. graminearum but the results on F. virguliforme were inconclusive.


  • The study will clarify the risks and benefits of cover crop use in Iowa conditions in terms of their impact on three important biotic diseases (SDS, white mold, and Fusarium root rot), and one abiotic disorder (IDC).
  • The results offer an opportunity to increase soybean productivity through disease/disorder management, while also improving environmental stewardship due to the known benefits of cover crops on soil erosion and reduced nutrient runoff.

For more information about this research project, please visit the National Soybean Checkoff Research Database.

Funded in part by the soybean checkoff.