Low-cost Farm-made Indigenous Soil Microbial Inoculant: Yield Impact on High Tunnel Grown Tomatoes

Progress report for FNC22-1347

Project Type: Farmer/Rancher
Funds awarded in 2022: $7,704.00
Projected End Date: 01/15/2024
Grant Recipient: Mellowfields Farm
Region: North Central
State: Kansas
Project Coordinator:
Kevin Prather
Mellowfields Farm
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Project Information

Description of operation:

Our certified organic farming practices and direct-to-consumer marketing deliver fresh and nutritious vegetables to the eaters in Lawrence and the Kansas City area. Currently, Mellowfields Farm cultivates almost 3 acres of Kansas River bottom soil. Along with a team of 5 employees, we start, plant, cultivate, harvest and sell over 50 varieties of vegetables for sale directly to eaters through webstore and farmers market as well as through grocery stores, food hubs and restaurants.


We will be looking at how the yield of high tunnel tomatoes are affected by the use of a farm-made indigenous soil microbial inoculant similar to Korean Natural Farming methods, but simpler and cheaper to implement using locally sourced ingredients. Improving soil health in high tunnels is an on-going struggle for many. The “desert effect” from lack of rainfall in tunnels, combined with frequent tillage, can lead to the destruction of microbial diversity. Many methods of replenishing these beneficial bacteria and fungi can be expensive (purchased inoculants),  tie up valuable farm real estate (covercropping), or be laborious (vermicomposting, etc.). By producing our own farm-made microbial inoculant, we hope to increase the soil’s microbial community (ecologically sound), increase yields & decrease costs (economically viable), and save the farmers’ time through this simple system (socially responsible).

Four ingredients: potatoes, leaf mold, salt,  & water. ‘Wild caught’ soil microbes from leaf mold proliferate by feeding on a dextrose nutrient media (potato water). In this system, most ingredients would be available on-farm (potatoes & leaf mold). The only ingredient to purchase-in would be salt, which is easily accessible. If potatoes aren’t grown on-farm, they are cheaply accessible from any supermarket.

Project Objectives:
  • Develop a simple, affordable system for making and applying farm-made microbial inoculants within high tunnel-grown tomato production (Year 1)
  • Determine the effect of farm-made microbial inoculant on overall yield of tomatoes through multiple successions over the course of a full season (Year 2)
  • Share findings through field days and social media (Year 2)



Materials and methods:

In 2022, during the first year of my 2-year SARE grant, I worked on building the system that I will use to run my experiment in 2023. It consisted of two 55 gallon barrels, a Dosatron syphon fertilizer injector, an irrigation pump, 200 mesh water filter, various pieces of black poly irrigation tubing and fittings, a "bioextractor" mesh bag, and an InstantPot pressure cooker.

I set up my barrels on a stable pad in a protected location by an outbuilding near electricity. I installed the Dosatron injector on the wall behind the barrels, in a position above and between the barrels so that its siphon tube could drop into each barrel. With standard 3/4" poly tubing, I brought water from a spigot to the siphon injector, installed a cheap 200 mesh water filter, then built a bypass around the siphon injector so that I could divert the water from flowing through the injector when not in use. On the other side of the bypass, the poly tubing connected to a small irrigation pump to make sure the water pressure was high enough to get to the hoophouses where the experiment will be held. To test the system, garden hose was used to move finished and diluted microbial solution (JMS) to each of the hoophouses. I plan to use layflat hose in the future to provide better flow. Or another version might be to put the barrel system directly in a hoophouse in order to shorten the distance the JMS has to travel and avoid extra hoses laying around. In this version the barrels would need lids of some sort to protect from direct sunlight.

Testing my system went smoothly once it was installed. I filled a barrel with untreated well water (probably 50 gallons full) with a garden hose and dissolved 1 lb. of salt by stirring in with a shovel. I checked to make sure the water temperature in the barrel was above 65 degrees F before beginning the process. At that point, I cooked potatoes in the InstantPot and mashed them up in the pot after they were cooked. I added the mashed potatoes (2 lbs.) and leaf mold compost found on the property (1 lb.) in a "bioextractor" mesh bag. I put the mesh bag in the water and gently massaged the contents to encourage them to dissolve into the water. I placed a rock in the bottom of the bag and hung it on a tool handle positioned across the barrel's top so that it was suspended right below the water's surface and couldn't accidentally float up. After a couple of days (1-3 days depending on water temperature), bubbles begin forming on the water's surface, which indicates microbial activity in the water. When the bubbles thicken into a disc, the JMS microbial solution is at its peak. A clear ring begins to form around the outside of the bubbles to indicate that microbial life is beginning to run out of food and die off, which is the sign to use all of the solution while it's still teeming with life.

When the solution was ready to use, I placed the siphon tube in the finished barrel of JMS, turned both shut-off valves on the bypass to open the syphon injector, and turned water on at the spigot. The injector was set to 20:1 dilution rate (water : JMS), drawing the solution out of the barrel, into the irrigation line, out to the hoophouse. I applied the inoculated water directly and deeply to the roots of the plants using drip tape.

The goal of the system was to be quick and easy to use, and after the initial setup, I found it to be very simple to operate. After the potatoes are cooked, it takes about 10 minutes to get a batch started. I would check it a couple times a day to see if the JMS was mature and ready to apply. With the use of a float valve for filling the barrel, and an irrigation timer for shutting off the irrigation at the end, it was a very "set it and go" system. When I use farm-grown b-grade potatoes as my starter, it costs less than $1 per 50 gallon batch (only paying for the salt), which seemed to be enough JMS to apply to all three hoophouses each week. My estimation is that this will amount to about $20 per season of total cost for all 3 hoophouse successions of tomatoes. Cheap and easy, I hope. I'm looking to seeing what the experiment results reveal!

Participation Summary
1 Farmers participating in research

Educational & Outreach Activities

Participation Summary:

1 Farmers participated
Education/outreach description:

We are on track to share findings through field days and social media this fall and will share results from our outreach efforts in our final report.

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.