Microbe-Containing Biostimulants/Biofertilizers in Vegetable Production

Vegetable growers look to enhance and maintain the vigor of their crops and health of their soils. Some growers apply certain bacteria and/or fungi, in the form of commercial or home-made inoculants, to assist in the process. Establishing specific microbe-crop plant interactions with these applications is sometimes credited with increasing the reach, activity, and effectiveness of plant root systems (enhancing access to nutrients and water and the production of phytohormones). Inoculated crops can also show greater stress tolerance and some microbes can enhance soil nutrient availability.

Still, of the many thousands of different types of microbes that can inhabit agricultural soils, a small percentage has been tested and found to have the potential to help growers. An even smaller percentage is included in commercial microbe-containing biostimulants/biofertilizers (MC BSs/BFs) advertised to enhance crop growth, especially in organic vegetable production.

Grower and researcher experiences with commercial MC BSs/BFs have been mixed. Product applications typically have positive to neutral effects on crop growth and yield, although decreased yields have been reported in rare cases. Growers, product manufacturers, researchers, and others offer various explanations for the mixed, inconsistent, and sometimes weakly positive results. Some suggest that the product was stored, handled, or used incorrectly. Others suggest that the product was inherently defective (e.g., contains too few, inactive, or the ‘wrong’ type of microbe). Others doubt that any inoculant is likely to result in significant growth and/or yield increases, given the complexity and quick-changing nature of soil, microbe, and crop interactions and environments. Regardless, two things appear to be true: MC BS/BF production and use continue to climb in the U.S. and world and growers have many questions about selecting, using, and evaluating the effects of microbe-containing biostimulants/biofertilizers.

Questions about selecting, using, and evaluating the effects of MC BSs/BFs are expected. These products are less regulated than biopesticides, sometimes costly to use, often minimally labeled, very numerous and diverse, and generally not discussed in extension and similar objective resources. Growers wonder how to use MC BSs/BFs most effectively.

We are taking several steps to address grower questions about microbe-containing biostimulants/biofertilizers. First, we created and maintain an interactive database of OMRI-listed products. The database is updated periodically and now contains information on 173 products. Second, we partner with vegetable growers, product manufacturers, and others in evaluating products and assisting people in completing their own evaluations. Currently, there are several projects underway on-station at the OARDC in Wooster, OH as well as on-farm at locations throughout the Midwest. Projects are supported by  USDA-NIFA Organic Transitions and NCR-SARE. Past projects have been supported by the Paul C. and Edna H. Warner Endowment Fund for Sustainable Agriculture, the OSU-Center for Applied Plant Sciences (CAPS), and the OSU Department of Horticulture and Crop Science. The Ohio Ecological Food and Farm Association (OEFFA) and product manufacturers have also assisted with the projects. Finally, we also share the results from work involving MC BSs/BFs widely and in many formats, including conferences, articles, workshops, and personal consultations.

Please click here for details about ongoing projects and available resources.

Research Team

Completed Projects