Resources that Help Sustainable-Organic Vegetable Growers Select, Use, and Evaluate Microbe-containing Crop Stimulants (MCCSs) More Effectively

On-station experiments were completed at OSU's OARDC in Wooster, OH using two warm season fruiting crops (butternut squash and tomato) and three cool season leaf and root crops (carrot, lettuce, spinach), in certified organic or transitional sites in open field and high tunnel settings.  Crops were planted in spring, summer, and fall and managed using certifiable organic practices. These experiments tested six different microbial biostimulant products applied at specific crop development stages (timing) or at different rates (rate) based on manufacturer recommended rate. Only timing was used as a factor in high tunnel experiments while timing and rate were factors in field experiments. Experiments completed on-station are outlined in Table 1. Experimental factors are summarized in Table 2. Brief narratives of experiments are provided after Table 2.

High Tunnel Experiments

1) Carrot (Spring 2017; Spring and Fall 2018; Spring and Fall 2019)

One high tunnel (30’ x 80’, transitional) was hand-seeded with pelleted organic ‘Mokum’ carrot into (20) 12’L x 4’W x 1.5’H wood-framed raised beds to test the application of five different microbial biostimulant products (BioGenesis I™ NP, EcoFungi, MycoApply® All Purpose, MycoApply® Endomaxx, and MycoGenesis™) at three different stages of crop development (after seeding/before emergence, 1 week after 50% emergence, or 3 weeks after 50% emergence) with a control of no product application at any time. A randomized complete block design was used with four replications. Soil in raised beds was composed of loam silt field soil, Pro-Mix BX, dairy manure compost, and horticultural grade perlite and vermiculite. All raised beds were seeded with four rows, 2” in-row and 12” between row spacing. Each raised bed in a replication was assigned a single product and contained 4 plots (4’ L x 3’ W), one control and one each receiving treatment at a specified timing. Seedling stand counts were completed after emergence to determine when 50% emergence had been achieved. The crop was drip irrigated. No pest or disease controls were applied during the experiment. Carrots were harvested once with the following data collected: total count, total biomass, root and crown weight, and cull reasons; individual weight, root length, shoulder and tip diameters, internal and external colorimeter readings of 3 subsampled marketable roots per plot; % dry matter of roots and °Brix on halves of 3 subsampled marketable roots, aggregated.

*MycoApply All Purpose was discontinued by the manufacturer. MycoApply Soluble Maxx was used in the Fall 2019 experiment.

2) Lettuce

Lettuce experiments varied in the number of products and timings used across seasons and years. This variation was due to high tunnel availability and differences in high tunnel size. Each experiment maximized the number of products and timings that the size of the high tunnel could accommodate. 

A. Spring 2017 included application of all six products at all three timings

Two high tunnels (21’ x 48’ each, certified organic) were planted with six-week old organic ‘Parris Island’ transplants to test the application of six different microbial biostimulant products (BioGenesis I™ NP, EcoFungi, Environoc 401®, MycoApply® All Purpose, MycoApply® Endomaxx, and MycoGenesis™) at three different stages of crop development (at transplant, 2 weeks after transplant, or 4 weeks after transplant) with a control of no product application at any time. Three products were tested in each tunnel. A completely randomized design was used with four replications. Each high tunnel was planted with four rows (6” in-row and 8” between row spacing) per replication. The crop was transplanted into flat, Wooster silt loam bare soil and drip irrigated. Each plot (3’ L x 4’ W) received treatment at a specified timing or a control of no application. No pest or disease controls were applied during the experiment. Lettuce was harvested once with the following data collected: fresh weight of 3 marketable heads, leaf area, % dry matter of leaves, and °Brix.

B. Spring 2018 and 2019 included application of four products at two timings

One high tunnel (21’ x 48’, certified organic) was planted with six-week old, organic ‘Parris Island’ transplants to test the application of four different microbial biostimulant products (BioGenesis I™ NP, Environoc 401®, MycoApply® Endomaxx, and MycoGenesis™) at two different stages of crop development (2 weeks after transplant or 4 weeks after transplant) with a control of no product application at any time. A randomized complete block design was used with four replications. Each replication was planted with four rows (6” in-row and 8” between row spacing) per replication. Products were applied at their specified timings. The crop was transplanted into raised, Wooster silt loam bare soil and drip irrigated. Each plot (3’ L x 4’ W) received treatment at a specified timing or a control of no application. No pest or disease controls were applied during the experiment. Marketable lettuce plants were harvested once with the following data collected: total count, total fresh weight; fresh weight of plant, leaves, leaf area, % dry matter of leaves, colorimeter readings, and °Brix were collected for 3 individual subsampled plants from each plot.

C. Fall 2017 and 2018 included application of five products at all three timings

One high tunnel (30’ x 80’, transitional) was planted with 5-7 week old, organic ‘Parris Island’ transplants into (20) 12’L x 4’W x 1.5’H raised beds to test the application of five different microbial biostimulant products (BioGenesis I™ NP, EcoFungi, Environoc 401®, MycoApply® Endomaxx, and MycoGenesis™) at three different stages of crop development (at transplant, 2 weeks after transplant, or 4 weeks after transplant) with a control of no product application at any time. A randomized complete block design was used with four replications. All raised beds were planted with six rows (6” in-row and 8” between row spacing). Each raised bed in a replication was assigned a single product and contained 4 plots (4’ L x 3’ W), one control and one each receiving treatment at a specified timing. The crop was drip irrigated. No pest or disease controls were applied during the experiment. Soil in raised beds was composed of loam silt field soil, Pro-Mix BX, dairy manure compost, and horticultural grade perlite and vermiculite. Marketable lettuce plants were harvested once with the following data collected: total count, total fresh weight; fresh weight of plant, leaves, leaf area, % dry matter of leaves, colorimeter readings, and °Brix were collected for 3 individual subsampled plants from each plot.

3) Spinach

One high tunnel (30’ x 80’, transitional) was seeded with organic ‘Regiment’ spinach using a Jang JP-3 three-row push seeder to test the application of four different microbial biostimulant products (BioGenesis I™ NP, Environoc 401®, MycoApply® All Purpose, and MycoGenesis™) at three different stages of crop development (after seeding/before emergence, 1 week after 50% emergence, or 3 weeks after 50% emergence) with a control of no product application at any time. A randomized complete block design was used with six replications. Each 60’ replication was seeded to four rows with a target 2” in-row and 8” between row spacing; however, in-row seeding rates were inexact and varied due to imprecision of seeder. The crop was seeded into Wooster silt loam bare soil and drip irrigated. No pest or disease controls were applied during the experiment. Products were applied to plots (3.5’L x 2.67’ W) at their specified timings with seedling stand counts completed to determine when 50% emergence had been achieved. Spinach leaves were harvested once for spring plantings and twice in fall plantings, which over-wintered. The following data was collected: total marketable fresh weight, % dry weight of leaves, leaf area, and °Brix.

Field Experiments

Butternut Squash and Tomato (Summer 2017, 2018, 2019)

One organic field (210’ x 185’) and one transitional field (210’ x 150’ in 2017; 210’ x 185’ in 2018, 2019) were planted with tomato ('BHN 589') and butternut squash ('Metro PMR') transplants (six and five weeks, respectively) in June. Rate and timing experiments were conducted on both crops in both fields for a total of eight experiments each year. The timing experiment tested the application of six different microbial biostimulant products (BioGenesis I™ NP, EcoFungi, Environoc 401®, MycoApply® All Purpose, MycoApply® Endomaxx, and MycoGenesis™) at three different stages of crop development (at transplant, 2 weeks after transplant, or 4 weeks after transplant) with a control of no product application at any time. The rate experiment tested the application of the same products at three different application rates (0.5x, 1.0x, and 1.5x the recommended manufacturer rates) with a control of no product application, applied on or the day after transplant. Crops were waterwheel transplanted, adding one gallon 2-4-1 fish fertilizer to 100 gallons of transplant water, into plastic covered raised beds, Wooster silt loam field soil, with drip irrigation. Ground cover was used in the organic field and pre-emergent herbicides in the transitional field to control weeds between the beds. A split-plot randomized complete block design was used with four replications, 3 rows per replication. Each 100’ raised bed row was planted with a single row with 2’ in-row spacing, and 6’ centers, individual plots measuring 12’ l x 3’ W. Plantings were fertigated weekly beginning mid-July through harvest with fish hydrolysate (15-2-0.5) and liquid calcium (5%). Weekly rotations of pest and disease controls were applied during the experiment until harvest.

Butternut squash was harvested once in both fields with the following data collected: total weight and fruit count, marketable fruit weight and count, primary reason to cull for marketability; individual fruit weight, length and width, internal colorimeter, % dry matter of fruit, and °Brix were collected from three subsampled fruit per plot.

Tomatoes were harvested two-five times each season with the following data collected: total weight and fruit count, green fruit weight and count (final harvests only), marketable weight and fruit count, primary reason to cull from marketability; pH, titratable acidity, and °Brix were collected from three subsampled fruit per plot at least once per season.

On Farm Evaluations

On-farm evaluations were conducted each growing season by a combination of new and repeating farmers. Growers transitioning to organic or organically certified were invited to participate in on-farm evaluations to utilize one of six pre-selected microbial biostimulants or a biostimulant of choice, if they grew:

1. one of five crops (butternut squash, carrot, lettuce, spinach, tomato)
2. in field or high tunnel
3. in the Northcentral and Great Lakes States

Growers were recruited through direct outreach and collaboration with the Ohio Ecological Food and Farming Association via mailers and publishing of articles in quarterly newsletters. Project staff worked with each grower to determine crop, product, treatments, experimental design, and agree upon expectations for return of observations and yield data, when possible. Product (if one of the six pre-selected for study on-station and on-farm) was donated by manufacturers and shipped to growers. Project staff and growers stayed in communication during the season of evaluation by phone, email, and/or mail. Growers who completed an evaluation were provided a $250 stipend. A summary of on-farm evaluation is in Table 3.

Details about planting area, including size and management (irrigation, mulch, amendments, pest/disease control), observations of the crop throughout the growing season in writing and/or in photos (comparing treated to untreated), perceived ease of use of product/application, and data (predominantly yield) were collected by growers and provided to the project team. 

Through conversations with product manufacturers and growers, the project team continually assessed strategies to best assist growers to successfully set-up and complete on-farm evaluations. Several growers experienced challenges and were unable to complete their evaluations as expected. Examples of these challenges include inability to disentangle butternut squash vines to treatment plot; over commitment and inability to work into schedule; getting behind and not planting the variety of crops or quantity of crops expected; crop failure.