Organic weed management using chemically and microbially designed compost extracts

Project Overview

Project Type: Partnership
Funds awarded in 2016: $14,728.00
Projected End Date: 04/15/2017
Grant Recipient: Rodale Institute
Region: Northeast
State: Pennsylvania
Project Leader:
Dr. Gladis Zinati
Rodale Institute

Annual Reports


  • Vegetables: cabbages, turnips


  • Education and Training: on-farm/ranch research
  • Pest Management: biological control, compost extracts
  • Soil Management: soil analysis, soil microbiology, organic matter, soil quality/health

    Proposal abstract:

    Organic vegetable growers are continually on the lookout for practical and cost-effective technology that can reduce the severity of weed problems and yield losses. Laboratory and greenhouse trials conducted at Rodale Institute showed that chemically- and microbially-designed compost extracts (CMD-CE) with lower nitrate levels and higher nematode-to-protozoa ratios significantly reduced lambsquarter weed seed germination by 32% without affecting crop seed percent germination. On the other hand, compost extracts with lower nematode-to-protozoa ratios reduced pigweed seed germination by 20%. Quiet Creek Farm CSA owners Aimee and John Good are interested in effective weed management techniques that allow them reduce hand weeding cost and mechanical cultivation of soil to enhance soil health and crop yields. This will improve the overall sustainability and profitability at their farm in Kutztown, Pennsylvania. Partnering with the Goods, we will evaluate the effectiveness of CMD-CE on weed management of pigweed, foxtail, lambsquarter, and galinsoga in cabbage, turnip, and baby head lettuce crop production during spring and fall seasons in Pennsylvania. In a randomized complete block design with four replications, designed compost extracts will be applied during the growing season per crop and compared to mechanical cultivation- grower’s standard method in managing weeds. We will assess weed biomass and density, crop yield, and soil health per season. Results will be shared with growers and interested clientele through Rodale’s Annual On-Farm Field Day, a web article, presentations at grower and national conferences, and a publication in trade journals.  

    Project objectives from proposal:

    The overarching goal of this project is to find alternative methods for organic weed management that are environmentally- and economically- feasible and deemed practical and available to organic growers.

     We propose a one-year project to address the following questions:

    1. How effective are the chemically- and microbially-designed (CMD) compost extracts in reducing weed biomass and density in comparison to standard method (hand-weeding and mechanical cultivation?
    2. Would the use of designed compost extract improve crop plant growth early in the season and boost crop growth relative to weed growth?
    3. By what percent do the proposed CMD compost extract treatments enhance cabbage, lettuce and turnip yields
    4. How will the proposed and standard treatments impact soil health?

    The specific objectives of this project are to:

      1. Demonstrate that CMD-compost extracts may be used effectively as a weed suppresser to prevent early season weed germination and growth and reduce cultivation and hand weeding;
      2. Compare costs and benefits of using CMD-compost extracts on crops yields and soil health; and
      3. Transfer this knowledge to organic growers.

    Field plots will be established at our collaborator’s farm in spring and fall of 2016. In a randomized complete block design with four replications, cabbage, turnip, and lettuce will be grown on beds 5 ft x 20 ft (1.5 m x 6 m) per treatment per replicate. Dr. Zinati will prepare and spray the compost extracts in treatments that receive compost extract and will apply water in control treatments (cultivation and hand weeding without compost extract).

    The treatments are:

    1. Grower’s standard method-Mechanical cultivation and hand weeding,
    2. Four applications of CMD-CE at 1:4 dilution (compost:water) (spring application) and 1:3 dilution (fall application):
      1. After bed preparation and two weeks before transplanting (once),
      2. At transplanting (once),
      3. After the removal of row cover over on formed beds and between rows (once), and
      4. During the growing season (once).
    3. Three applications of CMD-CE at 1:4 dilution (compost:water) (spring application) and 1:3 dilution (fall application)
      1. At transplanting (once),
      2. After the removal of row cover over on formed beds and between rows (once), and
      3. During the growing season (once).

    Crop production:

    Cabbage: Cabbage seedlings ‘Tender Sweet’ and ‘Melissa’ will be established in the greenhouse in March 2016 and early July for spring and fall season plantings, respectively. Seedlings will be transplanted into two-row beds, spaced 30 inches between rows and 18 inch spacing within rows, two weeks after bed preparation - late April and late July of 2016 for spring and fall season plantings, respectively. Cabbage transplants will be covered with row covers. In spring, two major weed species (galinsoga and foxtail) compete with the young cabbage seedlings under the row cover, whereas pigweed is the major weed in the fall season. The standard practice of weeding is mechanical cultivation after the removal of row covers followed by two mechanical cultivations and hand weeding after the last cultivation to clean the rows. Mechanical cultivation includes the flex-tine weeder and duckfoot sweeps. There will be multi-picking of cabbage in June and October of 2016.

    Turnip: Turnip seeds ‘Hakurei’ will be seeded into 3-row beds, spaced 15 inches between rows with continuous bands of turnip seeds within the row in April and mid-August of 2016 for spring and fall season plantings, respectively. After seeding, beds are covered with row covers. Same weed species and standard method of weeding as cabbage. There will be two pickings in spring of 2016 (early to mid-June) and two in fall of 2016 (October).

    Lettuce: Baby Head Salad Mix lettuce ‘Salanova’ seeds will be established in the greenhouse in late April/early May and August 2016 for spring and fall season plantings, respectively. Lettuce seedlings will be transplanted into three-row beds with 15 inch centers between rows. Standard weeding management includes using the flex-tine weeder twice. Two successions of lettuce will be planted. Common weeds are galinsoga and foxtail in the spring, whereas, pigweed is a major weed in the fall. Lettuce leaves will be harvested about 2-4 times in spring of 2016 (mid- June) and similarly in fall of 2016 (mid- September).

    Compost and compost extracts:

    Three replicated samples from each compost pile (2) will be assessed before being used for compost extract dilutions. They will be analyzed chemically at the Agricultural Analytical Services Laboratory (AASL) at Penn State University (PSU) for Total C, Organic Carbon, Total solids, Total N, Total P, and available macro and micronutrients, pH, and EC.

    Another set of three replicated moist compost samples will be sent to two laboratories (Ward Laboratory and Earthfort Laboratory) for biological assessment (bacteria, fungi, nematode, and protozoa).

    Compost extracts will be prepared at 1:4 dilution (compost:water) for spring application. The compost will be bubbled in water for 24 hours and then used for spraying. Similarly, a 1:3 dilution will be prepared for fall application. Similarly, samples of compost extracts will be sent to above-mentioned laboratories for chemical and biological analyses.

    Weed density and biomass:

    Assessment of weed density (number per area) and biomass (weight per area) will be conducted in two randomly located sections in each plot before transplanting and after removal of row cover and before the next compost extract application during the growing season for each crop. Weeds in 0.5 m2 (5.4 ft2) quadrants will be counted and cut, dried at 65 C and weighed.

    Soil health assessment:

    Composite soil samples (eight cores) from 0-20 cm deep will be collected, air-dried, sieved through 2-mm sieve and sent for chemical analysis (pH, EC, macro and micro nutrients, organic matter, carbon and nitrogen) to the AASL at Penn State University. For biological analysis, moist soil cores collected from top 0-8 cm deep will be put on ice in ice chest and sent to two laboratories (Ward Laboratory and Earthfort Laboratory) for biological assessments.

    Crop Yield:

    At harvest, Dr. Zinati will harvest and record each treatment per replication and give the harvest to the Goods for their CSA share. She will evaluate the crop for its quality as size and color.

    Statistics and data presentation:

    Dr. Zinati will assess weed biomass and density, crop yield, and soil health per crop per season.

    Collected data on weed, yield, soil quality indicators, and profitability will be compiled, and analyzed by standard ANOVA using the generalized linear model (GLM) of SAS® 9.3[14]. A chart of cost benefit will be prepared based on inputs such as hours and cost of weeding, cultivation, farmer return, profit and benefits gained for soil health. Analyzed data will be presented in tables and graphs and written in technical and scientific formats.

    Expectation of proposed method:

    In this project, we will demonstrate the effectiveness of the proposed method of using CMD-compost extracts at 1:3 and 1:4 dilutions in reducing weed expression, and thus reducing cultivation and time spent on hand weeding and its potential integration into organic management cropping systems.

    John and Aimee Good have been engaged in discussions with Dr. Zinati to address the need of finding and evaluating alternative methods to cultivation and hand weeding to reduce labor and energy cost, improve soil health and improve crop yields. From the beginning, the Goods have been working with Dr. Zinati on designing the project. Both the Goods and Dr. Zinati will collaboratively carry out field and greenhouse activities, as well as outreach events at various venues.

    The project will run for one year. Specifically, between March and October 2016, the Goods will be involved in preparing the field site, bed formation, direct seeding of turnip, transplanting cabbage and lettuce seedlings into beds, applying and removing the row covers, cultivating and hand weeding, and helping in harvesting and weighing per each crop in spring and fall seasons.

    Between March 2016 and March 2017, Dr. Zinati will collaborate with the Goods on establishment of the field site and greenhouse activities. Dr. Zinati will oversee the project execution and deliverables. She will be involved in laying out the treatments in the field, collecting data on weed density and biomass and crops yields, preparing and applying compost extracts from chemically- and microbially- designed composts, sending samples to laboratories for chemical and biological analysis, and compiling, analyzing and presenting project data.

    Outreach is vital to this project. We plan to disseminate project information and results in person to at least 500 people through the following outreach activities:

    1. The Goods will co-present with Dr. Zinati at Rodale Institute’s Annual On-Farm Field Day (July 2016). Commonly this activity attracts about 100 people.
    2. The Goods will be involved in two field days: i) Collaborative Regional Alliance for Farmer Training (CRAFT) during October 2016 and ii) Penn State University Extension (Spring 2017). These two activities attract about 50 people.
    3. Dr. Zinati will make presentations at the American Society of Agronomy Annual Conference (Phoenix, Arizona; November 2016), NOFA-NJ Winter Conference (January 2017), and Mid-Atlantic Fruit and Vegetable Conference (February 2017). These conferences attract a minimum of 400 people who are interested in organic weed management.
    4. Dr. Zinati will write a web article on the objectives and results from research and outreach activities, to be posted on Rodale Institute’s website.
    5. Dr. Zinati and the Goods will distribute hard copies of the project summary to the audience during Rodale Institute’s Annual On-Farm Field Day.
    6. Dr. Zinati will publish an article in a trade magazine (e.g. Biocycle) between January and March 2017.
    7. Dr. Zinati will write and submit the final report to NE SARE.

    We will distribute evaluation forms during local and regional conferences and field days to gather information and assess the project’s impact and intent of organic growers in adopting the newly-proposed approach.


    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.