2015
Effects of soil conservation practice (cover crop, crop rotations and tillage) on soybean SDS
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Contributor/Checkoff:
Iowa Soybean Association
Category:
Sustainable Production
Keywords:
Field management Soil healthTillage
Parent Project:
Effects of soil conservation practice (cover crop, crop rotations and tillage) on soybean SDS
Lead Principal Investigator:
Leonor Leandro, Iowa State University
Co-Principal Investigators:
Matthew Helmers, Iowa State University
Natasha Hoover, Iowa State University
Thomas Moorman, Iowa State University
+2 More
Project Code:
Contributing Organization (Checkoff):
Iowa Soybean Association
(n/a)
Institution Funded:
Iowa State University
(n/a)
Brief Project Summary:

Adoption of cover crops is increasing, and this practice could potentially increase risk of sudden death syndrome, the crops are hosts to Fusarium virguliforme, or suppress SDS if they enhance antagonistic microorganisms or excrete chemicals that inhibit the pathogen. No-till or reduced-till practices have also become a predominant practice due to environmental benefits for soil conservation. The effect of long-term tillage practices on SDS is not known. This study determines the host range of Fusarium virguliforme on 15 cover crop species and tests if a select number of these species affect SDS development. It also tests the effects of long-term tillage on SDS by comparing three tillage practices.

Key Benefactors:
farmers, agronomists, Extension agents

Information And Results
Project Deliverables

~Identification of crops that can be infected by F. virguliforme, thereby increasing pathogen density in soil.
~Identification of crops that are suppressive to F. virguliforme, thereby being good options as cover crops in fields with a history of SDS.
~Information about crops suppressive to F. virguliforme can be used to direct research efforts to test if they can be used as curative measures in high-risk SDS patches in fields.
~Clarification if conservation tillage practices reduce or increase risk of SDS, resulting in information growers can use in disease management plans.
~Recommendations to growers about the best cover crop and tillage options in fields with a history of SDS.

Final Project Results

Cover crop trials:
In the greenhouse host range trial, Fusarium virguliforme (Fv) caused root rot on all legume cover crops tested, but no root rot was observed on the brassica and grass crops. This shows that legume cover crop can be hosts to Fv and have the potential to increase SDS risk, whereas rye, ryegrass, triticale, and wheat have the least probability to increase Fv inoculum if used as cover crops.

In the microplot host range trial, no root rot was observed in any of the crops, including soybean, when plants were sampled 4-6 weeks after planting. We were unable to complete this trial and sample a second time later in the season due to flooding at the Hinds farm that compromised the trial.

In preliminary greenhouse tests of soil suppressiveness, no differences were found in SDS severity between plants grown in soil with long-term cover crop history and plots with no cover crop history.

Crop rotation trial:
SDS incidence and severity was significantly greater in the corn-soybean rotation plots, than on the plots with 3 and 4 year rotations. Maps of the spatial distribution of SDS incidence showed that the disease pressure is variable within each plot. These maps will be used to select sampling points for studies on host range and to study the effect of cropping history on Fv density in soil.

Fv soil population density in soil was correlated wih SDS incidence when incidence was above 50% , showing that the disease is inoculum dependent. However, we could not detect Fv in soil in plots with incidence lower than 50%. This revealed a limitation of the qPCR assay used in detecting low amounts of Fv in soil. The sampling and quantification protocol will need to be optimized before it can be used to monitor changes in Fv density in soil in reponse to crops or other factors.

Fv coud not be isolated from corn roots sampled from high and low SDS plots of the crop rotation trial. This suggests that corn plants do not get infected by the SDS pathogen in field conditions. This result is consistent with the greenhouse host range experiment.

Tillage field trial:
SDS disease index was low in the 2015 season. Tillage treatments did not significantly affect SDS index, root rot severity, stand count or yield this season

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.