Does Treatment with Chlorella vulgaris Extend the Life of Tomato Plants to Increase Tomato Sales?

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2021: $14,640.00
Projected End Date: 03/31/2023
Grant Recipient: Sweetgrass Garden Co-op
Region: Southern
State: South Carolina
Principal Investigator:
Dale Snyder
Sweetgrass Garden Co-op


  • Vegetables: tomatoes


  • Pest Management: biological control, compost extracts, prevention

    Proposal summary:

    If these initial observations are valid, treatment with live Chlorella vulgaris could make it possible to extend the life of tomato plants so that tomatoes can be harvested, where bacterial spot is endemic. Positive results will increase productivity and the length of  the harvest period which will positively impact  a farmer's bottom line.


    Project objectives from proposal:

    The test garden site has not been planted with tomatoes during the previous 7 years.  It will be divided into 2 sections:  one will be treated with 3 inches of mushroom compost before planting, and with additional compost side dressing 4 weeks later.  The other section will be treated with Chlorella vulgaris weekly beginning at the time of planting, 50,000 cells per sq foot produced on farm at Sweetgrass.   

    Assignment of which section to treat with which amendment will be done by an independent observer.

    It measures 32x32 ft (1026 sq feet), divided into four 16x16 ft test plots, which will be randomly assigned to the following treatments:
        1.   Algae
        2.   Algae + Compost
        3.   Compost
        4.   No amendment
    The 25 plant tomato grid (let's call it the "tomato patch") in each of the 4 plots has 5 rows containing 5 plants.  The rows and plants are separated by 30 inches.   Each tomato patch is situated in a corner of its test plot so there is a 4 ft area between the edge-tomato plants and the edge of the plot.  That means 8 ft of separation between each of the tomato patches.   
    There will be an untreated board barrier extending 10inches into the ground separating the 4 plots (essentially a 32-ft cross dividing the test garden into four equal-sized plots).
    To reiterate the nomenclature:  test garden = 32x32 ft.  Test plot (four of them) = 16x16ft.   Tomato patch (four of them in the corners of the plots) = 12x12 ft.

    Tomatoes: we will grow BHN1021.  Plants will be obtained from Banner Greenhouses (if plants are not available they will be grown from seed, started in our hoop house in organic potting soil).   There will be 25 plants in each of the test plots, planted at 24 inch intervals.   Lower leaves will be protected from exposure to the soil with organic matter (straw), and plants will be watered with drip irrigation (using our irrigation well).

    In addition to determining whether there is resistance to bacterial spot, we will assess the effect of chlorella on nematodes and on soil health and bacterial activity determined by Haney testing.

    End points:

    1.Plant height

    2.Plant vigor—a qualitative assessment by Zach Snipes (Clemson Extension Agent), blinded to treatment assignment. 

    3.Onset of bacterial spot (adjudicated by Zach Snipes).

    4.Tomato yield (also adjudicated by Zach Snipes), measured as tomatoes harvested per plant

    5.Nematode testing in each test section (Clemson Nematode Lab)

    6.Haney testing at the time of planting, and 2 months later (Ward Laboratories, Kearney, NB) 

    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.