Chapter 14

Weed Management for Organic Crops

(book excerpts)

Weed management continues to be one of the biggest challenges for organic field crop producers. Weeds can be considered a significant problem because they tend to decrease crop yields by increasing competition for water, sunlight, and nutrients while serving as host plants for pests and diseases. Farmers who wish to become organically certified are restricted from using synthetic herbicides for weed control under the Organic Foods Production Act of 1990 and the National Organic Program (NOP), section 7 of the Code of Federal Regulations (CFR), Part 205, also known as the NOP Final Rule. They meet this challenge by selecting from a wide range of acceptable techniques and strategies, all with the goal of achieving economically acceptable weed control and crop yields. The primary weed control strategies for organic systems are cultural and mechanical, focusing on prevention, crop rotation, crop competition, and cultivation. Organic weed management is a holistic system involving an entirely different approach to managing a farming system. The organic farmer is not interested in eliminating all weeds but wants to keep the weeds at a threshold that is both economical and manageable. A farmer who manages weeds organically must be intimately familiar with the type of weeds and their growth habits to determine which control methods to employ.

Click on the following topics for more information on weed management for organic crops.

Topics Within This Chapter:

  • Weed Biology
  • Life Cycle of Weeds
  • Annuals
  • Biennials
  • Perennials
  • Reproduction in Weeds
  • Weed Seed Banks
  • Weed Emergence
  • Cultural Weed Control
  • Managing Weeds with Cover Crops
  • Cover Crops as Living Mulches
  • Allelopathic Cover Crops
  • Role of Crop Rotation in Weed Management
  • Selecting Crop Varieties that Better Compete with Weeds
  • Adjust Crop Planting to Disrupt Pest Habitat
  • Altering the Planting Dates to Control Weeds
  • Adjusting Seeding Rate to Control Weeds
  • Mulches for Weed Control
  • Advantages and Disadvantages of Mulching
  • Synthetic Mulches
  • Organic Mulches
  • NOP Guidelines for Using Mulches and Weed Barriers
  • Controlling Weeds by Tillage and Cultivation
  • Tillage and Cultivation Practices in Managing Weeds
  • Annuals
  • Perennials
  • Stale (or False) Seedbed Tillage
  • Blind Cultivation
  • Crops Suitable for Blind Cultivation
  • Timing of Blind Cultivation
  • Weeds Susceptible to Blind Cultivation
  • Implements Used for Blind Cultivation
  • In-Row Cultivation
  • Finger Weeders
  • Torsion Weeders
  • Retracting Tree/Vine Cultivators
  • Between-Row Cultivation
  • Field Cultivators
  • Rolling Cultivators
  • Flex-Tine Harrows
  • Basket Weeders
  • Rotary Cultivators
  • Brush Weeders
  • Weather and Soil Conditions Suitable for Cultivation
  • Controlling Weeds by Mowing
  • Types of Mowers
  • Flame Weeding
  • Advantages and Disadvantages of Flame Weeding
  • Timing of Flame Weeding
  • Flame Weeding Treatments
  • Non-Selective Flame Weeding
  • Selective Flame Weeding
  • Equipment Used for Flame Weeding
  • Soil Solarization for Weed Control
  • Mechanism of Soil Solarization
  • Time of Solarization
  • Methods of Solarization
  • Broadcast Solarization
  • Strip Solarization
  • Solarization Practices for Controlling Weeds
  • Biorational Control of Weeds
  • NOP Requirements for Using Herbicide Products
  • Types of Biorationals Used for Weed Control
  • Acetic Acid (Vinegar)
  • Corn Gluten Meal
  • Cinnamon Oil
  • Citrus Oils and Extracts
  • Clove Oil
  • Lemongrass Oil
  • References