ARS | Publication request: Managing weeds in potato rotations without herbicides

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 10, 2010
Publication Date: September 20, 2010
Citation: Boydston, R.A. 2010. Managing Weeds in Potato Rotations without Herbicides. American Journal of Potato Research. 87:420-427.

Interpretive Summary: Weed management in modern conventional annual cropping systems relies heavily on synthetic herbicides. Recent consumer demand for food products with less or no pesticides has led to an increase in organic food production in the past decade. Perceived difficulty in managing weeds is often the single largest deterrent for growers to switch to organic production methods. Managing weeds with less or no herbicides requires a holistic approach to weed management and must include of a combination of tactics in order to successfully and economically reduce the negative impacts of weeds. Organic producers must utilize multiple control methods and a diverse crop rotation in order to manage weeds and deter the buildup of a few difficult to control species. Growers that successfully manage weeds take a proactive approach and attempt to understand the interactions between the cropping system and the weed community and manage the system to prevent and discourage weeds. Weed control methods can be categorized as biological, cultural, mechanical (physical), and chemical. Biological methods include use of insects and pathogens to suppress weeds. Cultural methods include a diverse crop rotation, selection of competitive cultivars, using optimum planting dates and row spacings, maintaining optimum soil fertility for the crop, cleaning weed seeds and vegetative matter from machinery, use of cover crops, and maintaining soil fertility and use of composts. There are numerous methods of mechanical control of weeds including mowing, cultivation, hoeing, flaming, mulching, and hand weeding. Chemical control of weeds consists of using herbicides and soil fumigants, most of which are not allowed in organic production. Weeds must be managed within a cropping systems perspective, emphasizing crop rotation, utilizing cover crops, managing weed seed banks, and using cultural, chemical, biological, and mechanical control methods in an integrated approach. New technologies for detecting crop rows and weeds coupled with precision cultivation, flaming, and application of nonselective organic herbicides are being developed and hold promise to reduce the need for hand weeding.

Technical Abstract: Managing weeds without herbicides requires an integration of methods and strategies and a change in how weeds are perceived. Weeds should be managed in a holistic, intentional and proactive manner. Successful weed management in organic systems attempts to understand the interactions between the cropping system and the weed community and manages the cropping system to prevent and discourage weeds and maintain a low weed seedbank. Cultural practices, including a well-planned crop rotation, planting cover crops, sanitation practices, and optimum row spacing and timing of planting are important aspects of managing weeds in organic systems. Multiple, well timed shallow cultivations or flaming can eliminate many early season weeds. Once emerged, many crops are fast growing and produce a canopy able to suppress weeds. New technologies for detecting crop rows and weeds coupled with precision cultivation, flaming, and application of nonselective organic herbicides are being developed and hold promise to reduce the need for hand weeding.