Progress report for LNC17-393

Project Type: Research and Education
Funds awarded in 2017: $149,349.00
Projected End Date: 09/30/2021
Grant Recipient: The Ohio State University
Region: North Central
State: Ohio
Project Coordinator:
Dr. Sally Miller
The Ohio State University, Dept of Plant Pathology
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Project Information

Summary:

This project, entitled “Optimizing anaerobic soil disinfestation (ASD) to manage emerging soilborne diseases in tomato protected culture systems in the North Central Region”, addresses an emerging issue in intensive vegetable farming systems. Higher demand for local produce as well as increasing weather extremes have led to expanded adoption of greenhouse and high tunnel vegetable production systems in the North Central United States. ASD is a promising approach to suppress soilborne disease and promote soil health and crop productivity. During the period covered by this progress report, research was conducted to optimize ASD for tomato production in high tunnels, focusing on carbon sources used during ASD, including agricultural plant byproducts and cover crops.  Higher rates of the plant byproducts tended to result in better outcomes (disease suppression and/or plant biomass), and soybean meal, wheat midds, and distiller’s dried grains proved to be most effective as ASD carbon sources.  These were selected for on-farm trials, conducted using the “Mother Baby Trials” approach.  Replicated Mother trials were established on six farms to evaluate these carbon sources, while Baby trials with wheat midds were established on nine farms in late summer/autumn 2018.  Post ASD bioassays and soil sampling for microbial community analysis were conducted. Farmer and Extension educator participation monitoring using Outcome Mapping has shown to date various levels of participation among individual boundary partners.

Project Objectives:

Our project will lead to both learning and action outcomes to benefit vegetable farmers in the North Central Region. We will increase farmers’ awareness and understanding of soilborne diseases and potential methods for managing these diseases through workshops and factsheets. Farmers will learn the skills to apply ASD through workshops and participatory on-farm trials. Ultimately, achievement of these learning outcomes will lead to action outcomes, including farmer adoption of ASD and integrated soilborne disease management strategies. The findings of our project will benefit farmers, extension agents, and plant health professionals.

Introduction:

Continuous production with little rotation in protected culture vegetable production systems has resulted in the emergence of soilborne disease complexes that greatly reduce yield, quality, and profitability, especially in tomato production. Key diseases in these complexes include Verticillium wilt (Verticillium dahliae), black dot root rot (Colletotrichum coccodes), corky root rot (Pyrenochaeta lycopersici), and root knot nematode (Meloidogyne spp.). Management of soilborne diseases historically relied on environmentally damaging, energy intensive methods, such as fumigation and steam sterilization. Anaerobic soil disinfestation (ASD) is a promising disease management tactic in which soil is amended with a carbon source, irrigated to saturation, and tarped for several weeks. ASD is driven by and has a tremendous impact on beneficial soil microbial communities and soil health, yet our understanding of these impacts is not complete. Nor has ASD been evaluated or optimized for the North Central Region. It is critical to counter the effects of soilborne diseases on the sustainability of protected culture systems. The objectives of this project are to 1) optimize ASD for protected tomato culture, 2) generate new knowledge about how ASD affects soilborne diseases, beneficial soil microbes, and soil health, and 3) increase awareness and adoption of ASD technology in the region. The outcomes of the project are increased 1) farmer awareness and understanding of soilborne diseases and their management, 2) farmer understanding of the uses, mechanisms and benefits of ASD for disease management, and 3) adoption of ASD and integrated soilborne disease management strategies by community farmer-leaders leading to region-wide adoption. We will achieve these objectives and outcomes through greenhouse and growth chamber trials to optimize ASD and by participatory on-farm trials using the mother and baby trial design, which will allow us to introduce, evaluate and disseminate ASD in one series of trials. The impacts of ASD on soil health and soil microbial communities will be examined in the mother portion of these trials. Project progress will be evaluated using Outcome Mapping, which fosters close collaboration between program participants.

Cooperators

Click linked name(s) to expand
  • Carri Jagger (Educator)
  • Chris Smedley (Educator)
  • Sabrina Shirtzinger (Educator)

Research

Hypothesis:
  1. Anaerobic soil disinfestation (ASD) efficacy against soilborne fungal pathogens of tomato depends on the type and rate of carbon source used.
  2. ASD suppresses plant pathogenic microorganisms while improving soil microbial community structure and soil health. 
  3. ASD suppresses soilborne diseases of tomato and increases yields in high tunnel systems.
  4. Outcome Mapping is an effective tool to monitor project progress and stakeholder engagement and predict adoption of effective technologies.
Materials and methods:

Evaluation of agricultural byproducts as ASD carbon sources. Experiments were conducted to assess the effects of anaerobic soil disinfestation (ASD) carbon sources (wheat bran, distillers’ dried grain, whey, corn gluten, and soybean meal) and rates (9 t/a and 4.5 t/a) on various soilborne diseases of tomato (corky root rot, black dot root rot, root knot nematode). Soils from three tomato high tunnels from three Ohio counties (Wayne, Erie, and Highland) with a known history of soilborne diseases were used in these experiments. Experiments were laid as randomized complete block design with 5 replications. Each experiment was conducted twice.

Soils were placed in 9 oz plastic cups, amended with a carbon source, flooded with sterile distilled water, covered with black plastic mulch, and sealed with rubber bands and electrical tape. Two controls were used in these experiments, a non-amended, flooded, covered control (anaerobic control) and a non-amended, flooded, and uncovered control (aerobic control). An IRIS (Indicator of Reduction in Soil) rod was inserted into the soil in each cup. Cups were placed in growth chamber at 77°F (25° C) with no light for four weeks. After four weeks, cups were taken from the growth chamber, five holes were punched into the bottom of the cups using a nail, and cups were returned to the growth chamber for one week to dry. After one week of drying, soils were placed in a plastic bag and homogenized with a rubber mallet. Homogenized soils were returned to cups and two-week-old tomato ‘Moneymaker’ seedlings were placed in each pot. Tomatoes were grown in the greenhouse for 9 weeks at which time plants were harvested and roots were washed. Roots were evaluated for root rot (percent of roots rotten or discolored) and taproot rot using a 1 to 5 scale (1: no root rot, 2: 1 to 2 small lesions on the taproot, 3: multiple lesions covering less than 50% of the taproot, 4: multiple lesions covering more than 50% of the taproot, 5: taproot completely rotten or missing). No nematode galls were present so nematodes were not rated.

Following root rating, a subsample of roots from each plant was plated onto three plates of half strength potato dextrose agar. After two weeks, fungi growing on the medium were identified morphologically.

Evaluation of cover crops as ASD carbon sources. Eight cover crops were assessed for efficacy as ASD carbon sources: two grasses (Sorghum sudangrass and winter rye), three legumes (cowpea, crimson clover, and white clover), two Brassicas (mustard and oilseed radish), and buckwheat. Cover crops were direct seeded (5-7 seeds per pot) in a topsoil blend in Deepots (D40H) and were fertilized weekly with a 20-20-20 fertilizer. After seven weeks, the aboveground portion of the cover crop was harvested and cut by hand into 0.25-0.75 cm pieces. The cover crops were mixed at a rate of 9 t/a with soil obtained from a high tunnel in Highland County, OH and placed into 9 oz cups. Wheat midds were included as a separate treatment as a known effective ASD carbon source. IRIS rods were placed into cups and cups were sealed and placed in the growth chamber as described above. Soils, planting, and assessment occurred as described above for the carbon source trials. Experiments were laid as randomized complete block design with 5 replications. Each experiment was conducted twice.

On-farm evaluation of ASD. Trials were established using the mother and baby trial design. Mother trials are large, randomized complete block design trials with multiple treatments laid by researchers on a farm and managed by the farmer, while baby trials are small, farmer-laid completely randomized trials with usually only one treatment. Quantitative data on treatment performance is gathered by researchers from mother trials, while farmers’ opinions on their experience with ASD treatment are gathered from baby trials. The mother and baby trial method is an efficient means of introducing, evaluating and disseminating a new disease management strategy.

Larger, compensated on-farm “mother” trials were established in high tunnels on six Amish farms in four Ohio counties (Wayne, Holmes, Knox, Morrow). In these trials, the effects of ASD with wheat midds (nutritionally equivalent to wheat bran but less expensive), soybean meal, or distillers’ dried grains on soilborne diseases of tomatoes are being compared to non-amended soils. On-farm trials were laid as a randomized complete block design with four replications. Plots were 0.91 m wide and ranged in length from 3.1-9.3 m depending on the size of the high tunnel. Carbon sources were spread over the treated area and incorporated to a depth of 10-15 cm using a walk behind rototiller. Beds were formed by hand and then two lines of drip tape were laid on top of each bed. Black plastic mulch was laid over each bed and the sides of the mulch were covered with soil to prevent air exchange. Non-amended, covered plots serve as the controls. The irrigation was turned on until soils were saturated to a depth of 20 cm. Plots remained covered for 4-6 weeks, depending on the weather. Temperatures in treated and control soils were monitored using HOBO pendant temperature data loggers (Onset Computer Corporation, Bourne, MA), buried 15 cm deep in each of two plots per treatment.

Soil samples were collected immediately after the end of ASD treatment from a depth of 15 cm. Soil samples were divided for soil testing, soil health testing, post-ASD bioassays, and DNA extraction. For DNA extractions, soil samples were air dried in sealed coin envelopes in a fume hood for 12 hours. DNA was extracted from homogenized soil samples after the brief drying period using the MoBio Powersoil DNA extraction kit (Mobio Laboratories, Inc. a Qiagen Company, Carlsbad, CA) with two DNA extractions (0.25 g dry soil) were performed per soil sample.

Post-ASD bioassays were conducted on soil samples collected after ASD treatment.  Tomato ‘Moneymaker’ seeds was planted in pots (Deepots, 262 mL) containing ASD-treated or control soils collected from field plots. Plants were fertilized once weekly with a 20-20-20 N-P-K fertilizer. Tomatoes were grown in the greenhouse for nine weeks. Plants were harvested and roots were rinsed in running tap water to remove soil. Plants were assessed for dry shoot and root biomass, root rot severity, root knot nematode galling (if applicable) and taproot rot severity as described above. The experiment was laid as a randomized complete block design with four reps. Fungi were isolated from root systems as described above and plated onto two plates 1/2APDA per root system.

Soil samples were collected again in March-April 2019 and August 2019, representing pre-planting and late season sampling times. Soil samples were processed as before for soil testing and DNA extraction, but were not used for bioassays for these later sampling points.

Participating farmers recorded yield data from three plants at the center of each plot during the growing season. At season’s end, roots were collected from these three plants and assessed for root rot.

Nine farmers were provided with supplies to conduct baby trials. Four trials were in the vicinity of Knox and Morrow counties and five trials were in the vicinity of Wayne and Holmes counties. A survey was sent to baby trial participants in fall 2019 and responses were recorded.

Outcome Mapping. Outcome challenges and progress markers were created for three sets of boundary partners: mother trial farmer participants, baby trial participants, and Extension educators. Following the end of the mother trial setup, mother trial participants and Extension educators were evaluated for applicable progress markers. Evaluation of mother trials and extension agents is ongoing. Mother trial participants will be evaluated by survey in early summer 2020 to determine which progress markers were met.

Research results and discussion:

Evaluation of agricultural byproducts as ASD carbon sources. ASD using any of the carbon sources and rates tested led to the development of reducing conditions in the treated soils compared to the control soils, as indicated by percentage paint loss from IRIS tubes (Table 1). Root rot was significantly lower in tomatoes grown in ASD-treated soil regardless of carbon source and rate than in the non-ASD controls, but taproot rot was not significantly affected by treatment. The lowest root rot values were observed for plants grown in soils treated with the high rates of distiller’s dried grains (12.9%), soybean meal (13.9%), corn gluten (14.8%), and wheat bran (15.7%). Dry shoot and root biomass were significantly affected by ASD treatment. The highest root and shoot biomasses were observed in plants grown in soils treated with the high rates of soybean meal and corn gluten.

Although ASD with corn gluten significantly reduced tomato root rot and increased tomato biomass, phytotoxic effects were observed on tomato seedlings produced in soil amended with corn gluten. For this reason, corn gluten was not selected as a carbon source for the field trials.

Table 1. Effect of anaerobic soil disinfestation (ASD) agricultural byproducts carbon sources on development of reducing conditions (percent iron oxide paint loss from Indicator of Reduction in Soil (IRIS) rods), percentage tomato ‘Moneymaker’ root rot, taproot rot, and dry shoot and root biomass. 

<td style=”height: 56px;width

Carbon Source

Rate2

IRIS 

(% paint loss)

Root rot

(%)

Taproot rot

rating2

Dry shoot biomass (g)

Dry root biomass (g)

Corn gluten

Low

83.8bc

19.8bcde

2.4

4.3abcd

0.46abcd

Corn gluten

High

90.8ab

14.8de

1.8

4.8ab

0.54ab

Distiller’s dried grains

Low

89.1ab

21.4bcd

2.6

3.8abcd

0.40bcde

Distiller’s dried grains

High

92.8a

12.9e

1.7

4.6abc

0.53abc

Soybean meal

Low

87.1ab

23.0bc

2.5

4.5abcd

0.48abcd

Soybean meal

High

87.3ab

13.9de

1.8

5.0a

0.56a

Wheat bran

Low

82.5bc

19.5cde

2.7

3.1d

0.30e

Wheat bran

High

87.3ab

15.7cde

2.3

3.5bcd

0.39cde

Whey

Low

60.8d

27.0b

3.1

3.4bcd

0.36de

Whey

High

77.7c

Participation Summary
15 Farmers participating in research

Education

Educational approach:

Our educational approach is multi-faceted.  First, we present information on the use and efficacy of anaerobic soil disinfestation (ASD) to manage soilborne diseases and weeds to farmers, Extension educators, consultants and other researchers in grower meetings and technical conferences in several states.  Secondly, we provide farmers with hands-on experience using ASD through the “Mother and Baby Trial” approach, maintaining close contacts with participating farmers and Extension educators, and monitoring progress through Outcome Mapping.  Finally, we develop fact sheets, blog posts/newsletter articles and scientific publications on ASD to reach a broad cross-section of the specialty crop community.

Project Activities

Soilborne disease diagnostics
Managing soilborne diseases in high tunnels using anaerobic soil disinfestation
Mastering the anaerobic soil disinfestation technique
County Line Produce Auction Crop Walk
Mount Hope Produce Auction Crop Walk
Captina Produce Auction Crop Walk
Owl Creek Produce Auction Crop Walk
Hardin County Crop Walk

Educational & Outreach Activities

5 Consultations
1 Journal articles
1 Online trainings
8 Webinars / talks / presentations
5 Workshop field days

Participation Summary

625 Farmers
60 Ag professionals participated
Education/outreach description:

During 2018, we interacted with farmers, consultants, Extension educators and researchers on the benefits and utilization of anaerobic soil disinfestation (ASD) for suppression of soilborne diseases and weeds in vegetable crops.  We participated in five Crop Walks in five Ohio counties (total 450 participants) and made presentations to the Great Lakes Expo (Grand Rapids, MI; 100 participants) and the Southern Ohio Specialty Crop School (Loveland, OH; 20 participants.  Technical presentations on ASD were made during the 33rd Annual Tomato Disease Workshop (Chincoteague, VA). the 9th International IPM Symposium (Baltimore, MD), and the International Congress of Plant Pathology (ICPP2018), Boston, MA (two ASD presentations and one presentation on Outcome Mapping). 

In 2019 we participated in crop walks, grower meetings, workshops and seminars. Below are Extension outputs and seminars for 2019.

Extension presentations

Miller, S. A. 2019. Managing soilborne diseases of tomatoes in high tunnels using anaerobic soil disinfestation and grafting. Mid-Atlantic Fruit and Vegetable Convention, Hershey, PA. 215 participants.

Miller, S. A. 2019. Managing root knot nematode and other soilborne diseases using ASD. Ohio Produce Network, Columbus, OH. 35 participants.

Miller, S. A. 2019. Managing soilborne diseases. Mid-Ohio Growers Meeting, Mt. Hope, OH. 125 participants.

Miller, S. A. and Testen, A. L. ASD: Anaerobic soil disinfestation – greenhouse. Great Lakes Expo Fruit, Vegetable and Farm Market, Grand Rapids, MI, December 10-11, 2019. 75 participants.

Miller, S. A. and Testen, A. L. ASD: Anaerobic soil disinfestation – high tunnels. Great Lakes Expo Fruit, Vegetable and Farm Market, Grand Rapids, MI, December 10-11, 2019. 30 participants.

 Extension publications

Miller, S. A. and Testen, A. L. 2019. Managing soilborne diseases of tomatoes in high tunnels using anaerobic soil disinfestation and grafting. Proceedings, Mid-Atlantic Fruit and Vegetable Convention, Hershey, PA.

Miller, S. A. and Testen, A. L. 2019. ASD: Anaerobic soil disinfestation. Great Lakes Expo Fruit, Vegetable and Farm Market, Grand Rapids, MI, December 10-11.

Invited Seminars

Miller, S. A. Benefits and challenges of on-farm research to solve vegetable crop management problems. The Ohio State University Dept. Horticulture and Crop Science Seminar, Wooster, OH, February 27, 2019. 40 attendees.

Testen, A. 2019. Anaerobic soil disinfestation to manage soilborne diseases in Midwestern vegetable production systems. Iowa State University Department of Plant Pathology and Microbiology, Ames, IA. October 22, 2019. 50 attendees.

In 2020, due to pandemic restrictions on travel and face-to-face interactions, interactions with stakeholders were virtual after mid-March.

Extension presentations

Miller, S. A., Testen, A. L. and Khadka, R. Anaerobic soil disinfestation (ASD) to control soilborne diseases. Ohio Produce Network Grower Meeting, Columbus, OH. January 23, 2020. (in person; 35 attendees)

Rotondo, F. and Miller, S. A. Utilizing OSU Diagnostic Services for Specialty Crops – Vegetable Insect, Disease & Weed Update. OSU Agriculture and Natural Resources Ag Madness Webinar series. April 23, 2020. (virtual, 40 attendees)

Invited Seminars

Miller, S. A. Harnessing beneficial microbes for soilborne disease management in small- to mid-scale vegetable production systems. UC Davis Dept. Plant Pathology Seminar, Davis, CA, March 2, 2020 (in-person; 35 attendees).

Journal Articles

Testen, A. L., Rotondo, F., Mills, M. P. Horvat, M. M. and Miller, S. A. 2021. Evaluation of agricultural byproducts and cover crops as anaerobic soil disinfestation carbon sources for managing a soilborne disease complex in high tunnel tomatoes. Frontiers in Sustainable Food Systems doi: 10.3389/fsufs.2021.645197.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.