Integrated Weed Management
Weed management remains one of the biggest challenges and most resource-intensive activities for certified organic producers and farmers transitioning to organic.Rodale Institute, the global leader in advancing organic and regenerative organic agriculture, is launching a new research program to address this issue by developing Integrated Weed Management (IWM) strategies for organic systems.
What is Integrated Weed Management?
As adopted from the USDA definition of Integrated Pest Management (7 U.S.C. § 136r), Integrated Weed Management (IWM) is “a sustainable approach to managing weeds by combining biological, cultural, physical, and chemical tools in a way that minimizes economic, health, and environmental risks.”
It is a science-based decision process that combines tools and strategies to identify and manage weeds. In organic agriculture, synthetic chemicals are not a component of IWM, while bio-based chemicals could be an option.
Why is it Important?
A survey conducted by Organic Farming Research Foundation in 2016 identified weed management as the second highest priority for future research after soil health, quality, and nutrient management.
Research findings demonstrated that weed control in organic systems with corn (Zea mays L.) – soybean (Glycine max L.) rotations is a major and enduring challenge. Effective control of perennial weeds remains one of the major challenges for farmers transitioning to organic farming as well as for certified-organic growers. Weed management in organic systems requires a knowledge-based comprehensive system that relies on ecological processes, biodiversity, and natural cycles to maintain weed infestation below the economic and biologic threshold by integrating little hammers.
Relying on a single weed control method can cause weeds to develop resistance to that method and can lead to crop loss and other environment harms. For example, relying on tillage for weed control in organic production may trigger soil erosion, cause subsurface hardpan, reduce organic matter, disrupt floral and faunal habitats, and destroy soil chemical and physical properties. Thus, IWM must be a part of the organic management for season-long weed suppression while provisioning ecosystem services.
Approach and Practices
In practicing IWM, growers who are aware of the potential for weed infestation follow a four-tiered approach which includes: 1) set economic threshold when it indicates that weed control action must be taken, 2) monitor and identify weeds accurately so that appropriate control decisions can be made in conjunction with action thresholds, 3) prevent weeds from becoming a threat by using cultural practices, and 4) once the first two approaches indicate that weed control is required and the third approach is no longer available, effective and less risky control strategy must be chosen.
Techniques that improve competitiveness against weeds such as stale seed-bed technique, crop row configuration, crop rotation and cropping system, minimum or no-tillage, crop variety selection, harvest weed seed control, and planting time. Cultural methods are leading tools in organic crop production systems.
Physically removes or kills weeds using forces such as shallowly pitched interrow hoeing (with emphasis on no-till and reduced till organic systems), flaming, electrocution, hot water and foam application, soil steaming, cryogenic weed control, and air propelled abrasive grit. Mechanical methods are mainly used for organic crop production for in-season weed control.
Synthetic chemicals are not part of organic weed management. However, there are several plant-based bioherbicides available in the market listed in Organic Materials Review Institute’s (OMRI) inventory (www.omri.org) that can be used for chemical weed control in organic systems. The product must be included in the approved organic system plan for certified organic growers. The common bio-product groups include plant essential oils, corn gluten meal, microbial products, and allelopathic chemicals.
The active manipulation of antagonistic organisms to reduce weed population below the economic threshold level where the living natural enemies used to control weeds. The organisms could be phytophagous arthropods, parasites, parasitoids, pathogens (fungi, bacteria, viruses, and nematodes), and grazers. The common grazers are birds, animals (in pastures), and fish (in rice farming).
The use of Global Navigation Satellite System such as GPS has implications for precision weed management. The use of nanodevices and carriers are the new emerging technologies for use in crop protection. Private companies are developing robots and laser devices to effectively kill weeds. Unmanned aerial vehicles can also be used to monitor weed infestation and collect spectral data for precision control.
Although data science is not a direct intervention, it can be part of the weed management package. Access to data-intensive technologies can help monitor and control weeds. Data mining and analytics are essential for simulation modeling of crop-weed interaction, environmental impacts, and effectiveness of tools and tactics. Machine learning and artificial neural networks are essential for spatial statistics, thematic prescription mapping, and forecasting.
Dr. Madhav Dhakal
Crop and Weed Scientist
Dr. Dhakal is developing a research program on organic crop and weed management that may include cover crop-based no-till and continuous organic no-till farming, integrating crops and livestock, technological adoption, adaptation, and innovation, alley-cropping, intercropping, and intensification in regenerative organic systems. He received a Ph.D. from Texas Tech University in Plant and Soil Science and a master’s degree in Agronomy (weed science) and a B.S. in Agricultural Science from Tribhuvan University in Nepal. Before joining Rodale Institute, Dr. Dhakal worked for USDA-ARS and Mississippi State University overseeing a project titled Cropland Common Experiment of Long-Term Agroecosystem Research (LTAR) in Mississippi.