Effects of Vermicast Extract and Cover Cropping on the Soil Food Web and Crop Health as Compared to Beds Treated with Conventionally Applied Compost

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2023: $8,433.00
Projected End Date: 03/31/2025
Grant Recipient: Samaritan Community Center
Region: Southern
State: Arkansas
Principal Investigator:
Megan Thomas
Samaritan Community Center


Not commodity specific


  • Crop Production: cover crops
  • Soil Management: composting, soil quality/health

    Proposal summary:

    This project will test the repeated use of biologically rich vermicast extracts and mixed cover cropping to identify changes in soil health and quantify changes in crop yields or quality post amendments. We will also identify disease and pest prevalence pre and post introduction of amendments to the soil.

    The practice of planting crops in field blocks that are lacking a complete soil food web removes essential plant nutrients from the soil without replenishing them via plant root exudates working in tandem with proper soil biology. This leads to a diminishing yield each year as the soil continues to lose structure and available nutrients. We have observed that adding compost and rotating crops are efficacious practices for improving yields, but these practices rely on an endless reapplication of soil amendments (bulk broadcasted compost, manures, and agro-chemicals) which can be costly and labor intensive for farmers. Regenerative agriculture advocates report comparable yields with fewer yearly inputs by utilizing biological soil inoculants and diverse cover crops to cycle nutrients, increase soil carbon and sustain a balanced and complete soil food web. Vermicompost (worm castings) is as much as 60-70 times more efficient than conventional manure [1]. In a study testing vermicompost vs municipal compost, the vermicompost had significantly larger nutrient concentrations than the compost; when mixed with the soil, the vermicompost also had higher microbial population size and activity and produced increased ryegrass yields [2]. It would be beneficial to test the efficacy of preparing and applying extracts of microbial rich vermicast in a real market garden setting with more biodiversity than academic agriculture settings to better evaluate practical implications.

    Combined with testing for vermicast use, studying how cover cropping can impact soil health with and without vermicompost or organic compost would be beneficial in understanding how these two practices work together to impact yields. In studies at the University of California, after two years of cover cropping, productivity was highest after cover crops with high nitrogen content and productivity significantly correlated with the structure of the soil fauna [3]. We will be using a smartmix developed by Green Cover based specifically on our soil needs as our diverse cover crop test. 

    We will have multiple test plots to combine usage of organic compost with vermicast extract, both in isolation and with neither amendment, all accompanied by diverse cover cropping, to identify the outcome of each of these practices in conjunction in a market garden setting. 

    [1] Joshi, R., Singh, J. & Vig, A.P. Vermicompost as an effective organic fertilizer and biocontrol agent: effect on growth, yield and quality of plants. Rev Environ Sci Biotechnol 14, 137–159 (2015). https://doi.org/10.1007/s11157-014-9347-1

    [2] Tognetti C, Laos F, Mazzarino M & Hernández T (2013). Composting vs. Vermicomposting: A Comparison of End Product Quality. Compost Science & Utilization. 13. 6-13. 10.1080/1065657X.2005.10702212. 

    [3] DuPont T. S, Ferris H, Van Horn M (2009). Effects of Cover Crop Quality and Quantity on Nematode-based Soil Food Webs and Nutrient Cycling. Applied Soil Ecology. 41,2. 157-167. https://doi.org/10.1016/j.apsoil.2008.10.004

    Project objectives from proposal:

    Hypothesis: The composted plots will initially outperform the plots that are only amended with vermicast extract but as the immediately available nutrients are used up in the compost the extracted plots will outperform in growth, brix levels as well as show less susceptibility to pests and disease.
    Health of the cover crops will be measured by brix levels, soil tilth will be evaluated using a penetrometer, and prevalence of pests and disease will be ranked using the Daubenmire cover class method.

    If our hypothesis is supported by the results of our experiment, this would address our problem of having to administer costly and labor intensive soil amendments to maintain soil health by validating the alternative approach of applying liquid extracts of biologically rich vermicast to our farmland.

    Experimental Design Plot Layout: Our test plots will each be 5 feet by 15 feet to make it easy to observe and access the center of the patches from either side without stepping into the growing area. Each plot will have a total area of 75 square feet which should be large enough to account for any pockets of soil anomalies and still small enough to where we can have a minimum of 5 replications of each plot condition without taking away from too much of the total farmable area of our site.

    A representative sample will be collected from each test plot prior to commencing with soil treatments to establish a baseline of the starting biology in the soil. 

    Most commercially available, packaged worm castings are devoid of life, having become inert through lack of moisture, oxygen, or sterilization practices. The vermicast we will use for this experiment will be fresh, living material, that has been inspected by Biodesic via a microscopy assessment to determine the castings we use for our extract has living bacteria, protozoa, nematodes, fungi, and microarthropods in adequate numbers. The appropriate strainer bag will be used to filter our extract to ensure no living worms or cocoons are introduced to the test plots during application.

    Rainwater will be used to prepare the extracts to avoid the negative impacts of chlorine in the city water on the biology we seek to extract.
    We will check the rainwater under the microscope prior to making extract to ensure there is no buildup of anaerobic organisms that would contaminate the extract.
    After an extract is made we will check a sample of it under the microscope to ensure adequate levels and categories of soil food web organisms have been dislodged from the organic matter into our soil drench.

    Once an extract has been prepared and approved by Biodesic we will apply the extract to the appropriate plots within 30 minutes of making it to prevent the organisms from depleting all of the oxygen in the water and dying off.

    With each application of vermicast extract our control plots will receive the same amount of pure rainwater applied in the same manner as our soil drench extract is distributed but using a different vessel to avoid any biological contamination of the control. This will account for the additional moisture being a factor that will affect cover crop growth.

    Data on the plots will be collected at regular intervals and we will apply statistical analysis on our results to understand any differences in outcomes for each test condition.

    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.