On-farm Evaluation of an Innovative Anaerobic Soil Disinfestation Practice for Improving Organic Carrot Production in North Florida

Progress report for OS20-135

Project Type: On-Farm Research
Funds awarded in 2020: $19,995.00
Projected End Date: 03/31/2022
Grant Recipient: University of Florida
Region: Southern
State: Florida
Principal Investigator:
Dr. Xin Zhao
University of Florida
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Project Information


Weed management is a major challenge in organic production of direct-seeded carrots in Florida. If improperly managed, resource competition from weeds can result in economic losses of high-value crops. Our farm cooperator has expressed a strong interest to partner with us in seeking innovative solutions to overcome weed management challenges in their organic carrot production systems. This project is proposed to evaluate anaerobic soil disinfestation (ASD) as an option for managing weeds and soilborne disease in organic carrot production. While the efficacy of ASD tends to vary with carbon source, tarp type, and soil temperature, studies of more site-specific application are warranted. Despite the on-station trials conducted by researchers, many growers in Florida are new to the preplant ASD treatment. To address cost concerns from the grower, we are proposing to use locally sourced labile carbon amendments. Additionally, we are proposing the use of re-usable 6-mil silage tarp as suggested by the grower. It will allow the grower to reduce waste from using single-season plastic covers.  This on-farm project will also enable us to obtain a practical, up-to-date understanding of the costs associated with ASD application toward optimizing its benefits. By teaching the grower how to implement ASD treatment utilizing locally available resources and re-usable tarp, we expect to establish a partnership with local growers for technology and knowledge transfer which allows for a practical assessment of ASD with respect to its potential for improving high-value vegetable production systems. Furthermore, major challenges and concerns related to on-farm implementation of ASD practices will be better identified through this researcher-farmer partnership for developing future research dedicated to enhancing crop performance and long-term environmental and economic sustainability of organic farming systems.

Project Objectives:

The specific objectives of this project are to: 1) develop ASD treatments based on farmer-recommended inputs that fit within the site-specific farming system; 2) determine the effectiveness of ASD for controlling weeds and soilborne diseases in the production of organic, direct-seeded carrots; and 3) assess marketable yield and carrot quality as affected by ASD treatments.


Click linked name(s) to expand
  • Cody Galligan - Producer
  • Dr. Xin Zhao (Researcher)


Materials and methods:

We plan to conduct on-farm field experiments to evaluate ASD treatments involving different combinations of the use of feed-grade blackstrap molasses, an OMRI-approved chicken manure-based organic fertilizer Chick Magic 5-3-2, and on-farm compost. The grower typically direct seeds carrots after irrigating an area to stimulate weed seed germination then covering the area for a certain period of time to kill any emerged weeds. In this project, the proposed four treatments of ASD application consisting of different combinations of molasses, chicken manure-based organic fertilizer, and on-farm compost will be compared to the grower’s standard practices. Amendments will be incorporated into the soil using a rototiller and 2 acre-inches of irrigation water will be applied to saturate the soil prior to tarping. The 6-mil silage tarp will be securely tucked around the edges to decrease gas exchange beneath the tarp. Carrots will be directly seeded after three weeks of ASD treatment when the tarp can be removed. While we communicated with the grower regarding the setup of on-farm trials for the Fall 2020 and Spring 2021 seasons, everything had to be put on pause as we were not able to carry out on-farm research activities given the tremendous challenges brought on by the COVID-19 pandemic.

Research results and discussion:

Since we were unable to conduct on-farm research trials during this reporting period due to the COVID-19 pandemic, we don’t have any results to report at the moment. However, we have been in contact with the grower to actively discuss the on-farm field research and outreach plan for the next production season. As the situation gets improved, we plan to visit the grower in May-August 2021 to develop specific research protocols and a feasible timeline for conducting the on-farm ASD trials during the Fall 2021 and Spring 2022 seasons. We also hope to get feedback from the grower regarding project dissemination and outreach.

Participation Summary

Educational & Outreach Activities

1 Curricula, factsheets or educational tools

Participation Summary:

Education/outreach description:

Although we were not able to carry out the on-farm ASD trials due to the COVID-19 pandemic during this reporting period, we were able to develop a hands-on ASD application lab for an undergraduate course on organic and sustainable crop production at the University of Florida during the Spring 2021 semester. We hope to complete the on-farm trials for the Fall 2021 and Spring 2022 seasons and conduct a field day for project demonstration. 

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.