Weed Management in Organic Conservation Tillage/No Tillage

2008 Annual Report for LNC04-240

Project Type: Research and Education
Funds awarded in 2004: $146,314.00
Projected End Date: 12/31/2008
Region: North Central
State: Ohio
Project Coordinator:
John Cardina
Ohio State University

Weed Management in Organic Conservation Tillage/No Tillage


Three years of studies on various extracts from seeds of many crop plants show little potential for an easily-extracted plant-derived product that could provide residual weed suppression and substitute for synthetic herbicides in a no-till organic system. Soybean yields were more affected by late planting in the no-till plots than by weeds or possible allelopathy from rye cover crops.

Objectives/Performance Targets

The specific objectives of the project were as follows:
1) Develop agronomic practices for managing allelopathic cover crops to control weeds while enhancing soil quality.
a. Evaluate planting time and methods for establishment.
b. Determine optimum proportions of mixed cover crop species for weed suppression.
c. Evaluate grower experience using cover crops for weed suppression.

2) Evaluate the effectiveness of various natural products for suppressing weeds;
a. Screen essential oils, vinegar products, organic soaps, etc. against typical grass and broadleaf weeds in greenhouse studies.
b. Evaluate effectiveness of promising natural materials for suppressing weeds that appear in a cover crop system.


Comparisons of small grain crops (rye, barley, oat, spelt, wheat, triticale) showed that rye was most effective, followed by wheat and spelt; barley and triticale were not effective. A novel design for a cover crop roller was built and tested for two growing seasons on several cover crops. Our roller is simpler to construct than those described from elsewhere, but it could be improved by using 2-inch rather than 4-inch angle-iron for crimping the cover crops. However, comparison studies showed that when weed populations are not high, the need for the roller is questionable, and simply drilling into standing rye is equally effective (one year’s data only).

We tested extracts in soil media as well as in petri dishes with filter paper to determine if the active compounds would be bound to soil and lose activity. Results showed that activity was not lost in soil. We focused on wild carrot seed extracts since this was the species that showed activity and it is one that is easily cultured and readily available. It also represents a case of making a potentially useful product from a species that is considered a weed. It is also considered a useful species for providing habitat for beneficials, and so would fit in well with farmscapes that leave borders for such habitat.

Impacts and Contributions/Outcomes

The results for the work on seed extracts are significant because they demonstrate efficacy of pre-emergence weed control based on a plant product that growers could harvest and store. This kind of product development could help reduce potential human health risks and adverse environmental effects from management strategies in production agriculture and residential and public areas. The public interest in ‘natural’ methods for weed control is very strong, but virtually no such methods have been developed for use in vegetable crops or home gardens where user exposure and environmental impacts could be substantial.


Warren Dick

School of Natural Resources
1680 Madison Ave
Wooster, OH 44691
Office Phone: 3302633877
Debbie Stinner

Research Scientist
Organic Food and Farming Education and Research
1680 Madison Ave
Wooster, OH 44691
Office Phone: 3302633534