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Microbial Biostimulants in Organic Farming Systems: Patterns of Current Use and an Investigation of Their Efficacy in Different Soil Environments

Laudick, Julia Ann
http://orcid.org/0000-0002-1282-722X
http://rave.ohiolink.edu/etdc/view?acc_num=osu1483689529339271

Abstract Details

2017, Master of Science, Ohio State University, Environmental Science.
Microbial biostimulants (MBS) contain microorganisms that have the capacity to promote plant growth by one or more mechanisms. Decades of research on plant-beneficial microorganisms have demonstrated their potential role in sustainable agriculture, but the extent to which they are effectively applied remains unclear. The main objectives of this study were (1) to survey the current use of MBS products in organic farming systems, (2) to review the existing literature on the performance of plant growth promoting rhizobacteria (PGPR) in different soil environments, and (3) to test the effects of commercially available MBS products on plant growth under different soil conditions in on-farm and controlled settings. Factors associated with MBS use, along with the type and frequency of MBS products, were determined over a six-year period by aggregating and analyzing data from the organic certification records of 86 Ohio organic vegetable farms. MBS products accounted for 5% of all inputs by number, and 51% of farmers reported using them. The diversity and popularity of products used in Ohio is consistent with what is available on the market nationally. Mixed inoculants were most popular, but little research-based information is available on their efficacy. Thus, trials of six MBS products were conducted at four organic farms across Ohio. The products did not produce any significant, or even numerically consistent yield increases when applied to tomato under normal organic nutrient management practices. An on-farm factorial experiment was conduced with broccoli as a test crop, and had the following treatments: plus and minus two kinds of organic soil amendments, and plus and minus four MBS products. MBS inoculants increased yield by 13%-65% where no soil amendments were added. In the presence of both soil amendments, no additive effects of inoculation and compost amendment were observed. In order to better understand plot-to-plot variation in response to inoculation, the yield of the non-inoculated control was used an integrative proxy for background soil quality and other factors that affect plant growth. Plotting the percent yield increase due to inoculation against the control yield revealed a clear negative linear relationship between plant growth response to inoculation and the quality of the soil environment. Similar results were obtained in a full factorial experiment testing the effects MBS inoculants on spinach growth. These results are consistent with the PGPR literature. A majority of studies found in the literature with a full factorial design of high and low soil nutrient environment with and without inoculation indicated that plant growth response to inoculation was greatest in low to intermediate soil nutrient levels. Finally, a full factorial greenhouse study was designed to test the effects of a mixed inoculant on lettuce under low and high recent and historical compost application. The inoculant had no effect on plant growth under any of the test conditions, possibly due to low inoculum concentration. MBS products have many potential ecological and economic benefits, but more systematic research into factors that explain variability in their performance is needed for farmers to benefit from them more reliably.
Matthew Kleinhenz, PhD (Advisor)
Enrico Bonello, PhD (Committee Member)
Richard Dick, PhD (Committee Member)
Michelle Jones, PhD (Committee Member)
123 p.
Agriculture; Ecology; Horticulture; Microbiology; Soil Sciences
microbial biostimulants; plant growth promoting rhizobacteria; biofertilizers; organic amendments; agroecology

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Citations

  • Laudick, J. A. (2017). Microbial Biostimulants in Organic Farming Systems: Patterns of Current Use and an Investigation of Their Efficacy in Different Soil Environments [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1483689529339271

    APA Style (7th edition)

  • Laudick, Julia. Microbial Biostimulants in Organic Farming Systems: Patterns of Current Use and an Investigation of Their Efficacy in Different Soil Environments. 2017. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1483689529339271.

    MLA Style (8th edition)

  • Laudick, Julia. "Microbial Biostimulants in Organic Farming Systems: Patterns of Current Use and an Investigation of Their Efficacy in Different Soil Environments." Master's thesis, Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1483689529339271

    Chicago Manual of Style (17th edition)

osu1483689529339271
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This open access ETD is published by The Ohio State University and OhioLINK.