Weed Control Challenges

Organic vegetable production is a method that does not allow synthetic fertilizers, crop protectants, or genetically modified seed. Growers cannot just substitute “organic” products, but must create a long-term farming system with healthy soil, crop rotations, cover crops, and preventative pest control via cultural, physical and mechanical means.  

Weed control in organic vegetable production can be challenging. Weeds compete for light, water, and nutrients. Sometimes, they also encourage insect and disease problems. Short-term control is the seasonal control of weed pests, but long-term control is also possible through depletion of the weed seed bank in the soil.

First things first, weeds must be correctly identified in order for control measures to be appropriate. They can be classified based on whether they are grasses or broad leaves. Weeds also can be classified based on their lifecycle. Winter annual weeds germinate in the fall, overwinter, then re-grow in the early spring and generally die back by summer.

Summer annuals are one of vegetable growers’ biggest headaches, germinating in the spring and early summer and growing along with the crop. These are weeds such as lambsquarters, pigweeds, nightshades, and velvetleaf. Biennials, such as Queen Anne’s Lace, germinate and grow vegetatively the first year, overwinter, then flower and produce seed their second year. Quackgrass, nutsedge, Canada thistle, and milkweed are perennial weeds that grow indefinitely and propagate not only by seed but by underground structures such as nutlets, rhizomes, etc.

The Practice Of Rotation

Crop rotation is one of the most essential practices of organic vegetable growers. Because crops compete differently with weeds, rotation is an important aspect of weed, insect, and disease control. It is often difficult to plan for with vegetable crops since size of plantings may vary. Growers need to know crop families (brassicas, solanaceous, umbelliferaceae, cucurbits, legumes, sweet corn, alliums, lettuces), and should rotate by crop family. Try to design a plan for your fields for the next three to five years. 

Some recommendations to follow include:

• Rotate back to a family of crops only once every three to five years.
• Have a portion of the farm fallow at any given time.
• Plan for cover crop rotations.
• Plan for double cropping, if possible.
• Take into account weed competitiveness. 

For example, carrots, parsley, and lettuces do not compete well with weeds and are delicate. Put in these types of crops after a number of years of crops that can be cultivated and compete well.

Cover crops can be an effective method of weed control, since fast-growing, thickly sown crops will out-compete weeds. Choose a weed-controlling cover crop based on your soil needs and the type of weeds prevalent in the field. 

Legume cover crops such as clover or vetches add nitrogen; non-legumes (rye, wheat) add organic matter to the soil. Some cover crops, like rye, are allelopathic, meaning they give off substances that inhibit weeds. Cover crops should be planned for in a rotation plan. 

The Mulch Advantage

Both plastic and organic mulches, such as straw, can have many advantages in addition to acting as a physical barrier to weeds in the crop rows. When using black plastic, be sure to prepare your field appropriately and have enough soil moisture so that the mulch is applied smoothly and has good contact with the soil. Disadvantages to plastic mulch include weeds in between rows and in the planting holes. Disposal is also a problem, and if possible, used mulch should be taken to a recycling facility. 

Mowing weeds is a temporary solution, but can prevent them from actively competing with the crop and from going to seed. Propane flamers can be very effective in killing small broadleaf weeds. Growers can use handheld flame weeders as well as larger, tractor pulled units for use on larger areas.  

And finally, one of the most important techniques in organic weed control is cultivation. Effective cultivation includes knowledge of the crop, the weed, and the specific implement used. There are many different tools and timings of cultivation to bury or uproot the weed. Initial tillage prepares the field for planting and removes any growing weeds. The stale seedbed technique requires that after initial preparation, the field is watered and weeds are allowed to germinate. The field is then tilled shallowly (or flamed) to remove weeds. This is repeated two or three times to deplete the weed seed bank in the germination zone. Tools, such as tine weeders and various harrows, are useful for the stale seedbed technique. 

Edge of the plastic, between row and in-row cultivation for organic weed control, is both an art and a science. Knowing the right timing for the weed and the soil conditions is very helpful but not always possible given the weather. But choosing the proper equipment, setting it correctly, and driving skillfully are all up to the operator. Traditional tools such as field cultivators are useful, but there are many other choices available including basket weeders, spyders, and finger weeders.
   In conclusion, organic weed control can be achieved by an integrated program of cover crops, crop rotations, mulches, and mechanical controls such as flaming, mowing, and most importantly, cultivation. Preventing weeds from going to seed will deplete the weed seed bank and eventually lead to lower weed pressure and cleaner fields.

Leave a Reply

Featured Stories
John Lawson of Hyrdro Harvest Farms in Ruskin, FL
Berries
February 12, 2016
Central Florida Farm Goes Vertical To Capture ‘Buy Local’ Market
Hydro Harvest Farms in Ruskin has built a loyal following by serving and engaging the community. Read More
Lynn Long talks about what this 2015 UFO Benton on Gisela 3 planting needs to get established at Riveridge Land Company in Sparta, MI, during IFTA 2016.
Fruits
February 11, 2016
Attendees Brave The Cold To Vet Hot Topics At IFTA Conference
Multileader systems, V-trellis systems on tour stops throughout the Ridge growing region in Michigan. Read More
Summer Foley gets crowned Miss Florida Citrus 2015 by 2004 winner Nikki Upthegrove Matthews and reigning Miss Florida Vicotria Cowen
Citrus
February 10, 2016
Who Will Be Crowned Miss Florida Citrus 2016?
Contestants invited to carry on a time-old industry tradition. Read More
field USDA
Disease Control
February 10, 2016
Broad-Spectrum Fungicide Approved For Specialty Crops In California
Rhyme controls powdery mildew, brown rot blossom blight, and leaf rusts. Read More
A selection of Andean dry beans, Phaseolus vulgaris, from the Andean bean diversity panel.

 

Photo by Stephen Ausmus.
Vegetables
February 10, 2016
Pulse Crops Top The List For Research
Scientists are making global contributions by participating in the Feed the Future Grain Legumes Project. Read More
The restoration of this secondary channel of the Napa River was made possible through the Rutherford Reach Restoration Project.
Grapes
February 10, 2016
Restoring The Napa River
The Napa River, which has helped create soil perfect for grape-growing in the Napa Valley, is in danger. Fortunately, conscientious Read More
Almond Board of Calif. logo
Nuts
February 10, 2016
Almond Board Working Toward Next-Generation Sustainability Solutions
New sustainability initiatives will bring the almond industry into the 22nd century. Read More
Photo Credit: David Eddy
Nuts
February 10, 2016
Incentives Available For Low-Emission Harvesters 
Almond and walnut growers who use lower-emission harvesting equipment may be eligible for financial incentives. Beginning this year, the USDA Read More
pile of potatoes
Potatoes
February 10, 2016
Potatoes Are More Than A Good Source Of Potassium
Researchers have been investigating the enhancement of oxidative qualities through breeding potato selections that are considerably higher in antioxidants than those currently available. Read More
Make sure your tank is free of cracks or fractures to avoid loss of product.
Photos credit: Fred Whitford, Purdue University
Equipment
February 10, 2016
Get Your Sprayer Ready For Spring
Cleaning equipment, checking for damages, and ensuring proper calibration should be standard procedure before the season begins. Read More
The Latest
Berries
February 12, 2016
Central Florida Farm Goes Vertical To Ca…
Hydro Harvest Farms in Ruskin has built a loyal following by serving and engaging the community. Read More
Fruits
February 11, 2016
Attendees Brave The Cold To Vet Hot Topi…
Multileader systems, V-trellis systems on tour stops throughout the Ridge growing region in Michigan. Read More
Citrus
February 10, 2016
Who Will Be Crowned Miss Florida Citrus …
Contestants invited to carry on a time-old industry tradition. Read More
Disease Control
February 10, 2016
Broad-Spectrum Fungicide Approved For Sp…
Rhyme controls powdery mildew, brown rot blossom blight, and leaf rusts. Read More
Vegetables
February 10, 2016
Pulse Crops Top The List For Research
Scientists are making global contributions by participating in the Feed the Future Grain Legumes Project. Read More
Grapes
February 10, 2016
Restoring The Napa River
The Napa River, which has helped create soil perfect for grape-growing in the Napa Valley, is in danger. Fortunately, conscientious Read More
Nuts
February 10, 2016
Almond Board Working Toward Next-Generat…
New sustainability initiatives will bring the almond industry into the 22nd century. Read More
Nuts
February 10, 2016
Incentives Available For Low-Emission Ha…
Almond and walnut growers who use lower-emission harvesting equipment may be eligible for financial incentives. Beginning this year, the USDA Read More
Potatoes
February 10, 2016
Potatoes Are More Than A Good Source Of …
Researchers have been investigating the enhancement of oxidative qualities through breeding potato selections that are considerably higher in antioxidants than those currently available. Read More
Equipment
February 10, 2016
Get Your Sprayer Ready For Spring
Cleaning equipment, checking for damages, and ensuring proper calibration should be standard procedure before the season begins. Read More
Crop Protection
February 10, 2016
Bayer Contests EPA’s Decision On Insecti…
Company seeks to stop agency’s proposed cancellation of flubendiamide. Read More
Vegetables
February 10, 2016
Vegetable Production: A Lesson In Sustai…
Thanks to the efforts of those producing vegetables, we have an abundance of healthy food options. Read More
Insect & Disease Update
February 9, 2016
University Of Florida Research Receives …
A big chunk of the federal funding will focus on growing the bacterium in a lab. Read More
Citrus
February 9, 2016
Revised Forecast Yields Small Victory Fo…
Updated USDA estimate holds serve again; hasn’t dipped since December. Read More
Apples & Pears
February 9, 2016
State Of The Fruit Industry 2016 [VIDEO]
According to an national poll of fruit growers, fruit industry suppliers, and researchers, the market is poised for growth in Read More
Crop Protection
February 9, 2016
Biopesticides And IPM
Dr. Surendra Dara, Strawberry and Vegetable Crops Advisor and Affiliated IPM Advisor with University of California Cooperative Extension, has long Read More
Fruits
February 8, 2016
Precision Fruit Growing, Business Manage…
American Fruit Grower magazine managing editor Christina Herrick posts her updates from the 59th annual gathering. Read More
Farm Marketing
February 8, 2016
Food Policy: If You Don’t Speak, O…
British Columbia's former ag minister spoke with attendees at NAFDMA's Convention about the political realities surrounding food policies. Read More
[gravityform id="62" title="false" description="false"]