Evaluating Efficacy of Organic Herbicides on Common Weed Species in the North Central Region

Project Overview

Project Type: Graduate Student
Funds awarded in 2023: $14,879.00
Projected End Date: 08/31/2025
Grant Recipient: Iowa State University
Region: North Central
State: Iowa
Graduate Student:
Faculty Advisor:
Dr. Ajay Nair
Department of Horticulture, Iowa State University


No commodities identified


No practices identified

Proposal abstract:

Project Title: Evaluating Efficacy of Organic Herbicides on Common Weed Species in the North Central Region  

Weed management is a challenge, especially in organic vegetable production systems. Growers control weeds in several ways, many of which can have environmentally harmful impacts. Cultivation is a common way many organic vegetable growers manage weeds. However, soil disturbances decrease soil health, harm soil structure, and increase the likelihood of erosion. Manual weeding is extremely time-consuming and labor-intensive; many growers do not have access to these labor resources. Conventional herbicides have raised public concern for their impact on human health and the environment. Organic herbicides are naturally derived herbicides and are less toxic than conventional herbicides. Research incorporating the practical use of organic herbicides on vegetable farms has shown success; however, organic herbicides can be expensive. Additionally, there is a lack of research on organic herbicide efficacy on common weed species in the North Central region, leaving growers unable to make an informed purchase decision if they choose to use organic herbicides. This experiment will test six organic herbicides across six common weed species. This project will be conducted in the Iowa State University greenhouses. Each herbicide will be tested on a representative population of each weed species at different growth stages, 14 days after germination and repeat application at 28 days. Percent control will be measured 36-48 hours after each spraying event using TurfAnalyzer software to measure organic herbicide efficacy. 

The study will investigate organic herbicide efficacy on common weeds in the North Central region. The outcomes of this research project will provide growers with a guide to selecting an organic herbicide to use on their farms. This will allow growers to make economically informed decisions on organic herbicide purchases. Results from this experiment will be used to create outreach material, including extension publications, a scientific journal article, and a grower workshop. Grower workshop interviews, amount of interaction with online videos, extension articles, and journal publication downloads will measure project success. The experiment will bring attention to the social aspects of herbicide application safety and the effect conventional herbicides may have on human health and the environment. Growers will benefit from access to scientifically based research to support grower knowledge and decision-making on organic herbicide options. This approach will strengthen outreach and interaction with growers while helping them adopt a successful weed management plan.

Project objectives from proposal:

Learning outcome: The results of this study will aim to increase grower knowledge of organic herbicide options and their efficacy on common weed species in the North Central region. The grower workshop and on-farm extension visits will increase awareness of organic herbicide options. Growers will learn the skills and tools needed to create a weed management plan that works for their farms. They will also learn how organic herbicides can be integrated into a weed management plan. Organic herbicide cost and effectiveness will be compared to other weed management forms like tillage, conventional herbicides, and hand weeding. This project will compare the advantages and disadvantages of various weed management options, increasing growers’ skills to manage weeds effectively on their farms.

Action outcome: Outreach events will support grower decision-making regarding organic herbicide purchases and their implementation on farms. After the workshop and on-farm extension visits, exit interviews with collaborating growers will be conducted to measure action outcomes. Growers will have a better understanding of organic herbicides and how they can use them on their farms. Growers will make more informed decisions to increase overall farm profits and viability when they are in tune with the cost and time used to manage weeds on their farms. These outcomes will lead to grower education, allowing them to make the most economical decision for the specific weeds that pose challenges on their farms.

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.