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
Crop ProtectionResources For Knowing Your Soil
July 30, 2015
Getting to know your soil and learning other environmental and natural resources data can be downloaded and is available for use with many computer software platforms for general resource analysis and farm management. Read More
money
CitrusBankrupt Florida Farm To Yield Plenty Of Land, Equipment In Upcoming Auction
July 30, 2015
As many as seven different buyers could be part of this Chapter 11 proceeding. Read More
Sanjay Shukla
ProductionGeometrically Speaking, Thinking Smaller Might Produce Big Savings For Vegetable Growers
July 30, 2015
University of Florida scientist develops compact planting bed formula that cuts water, fertilizer, and pesticide use in half. Read More
GrapesDrought’s Impact On California Winegrapes
July 30, 2015
The impact is minimal this year, but the future is uncertain if the drought continues. Read More
Apples & PearsEPA Approves New 1-MCP Technology
July 30, 2015
EPA approved Fysium, a new 1-MCP product from Pace International LLC. Considered new technology, this product is produced on-site by Read More
Crop ProtectionNew Fungicide Targets Key Diseases
July 30, 2015
This disease control tool hits two different parts of the fungal life cycle. Read More
CitrusWestern Growers Praises Introduction Of California Emergency Drought Relief Act
July 30, 2015
Legislation contains short- and long-term provisions to deal with the historic drought. Read More
Farm ManagementFour Great Pricing Tips From U-Pick Experts
July 30, 2015
Although each of the growers I talked to has his or her own take on a pricing structure, they all Read More
BerriesUC-Davis Responds To California Auditor’s Recommended Improvements To Strawberry Program
July 30, 2015
Following a six-month review of the University of California (UC)-Davis Strawberry breeding program, the California state auditor’s office has released Read More
Farm ManagementHow To Find Your Perfect U-Pick Pricing Structure
July 30, 2015
If there’s one mission impossible for pick-your-own operations, it might just be how to set a pricing structure. Odds are you’ve Read More
The Latest
Crop ProtectionResources For Knowing Your Soil
July 30, 2015
Getting to know your soil and learning other environmental and natural resources data can be downloaded and is available for use with many computer software platforms for general resource analysis and farm management. Read More
money
CitrusBankrupt Florida Farm To Yield Plenty Of Land, Equipmen…
July 30, 2015
As many as seven different buyers could be part of this Chapter 11 proceeding. Read More
Sanjay Shukla
ProductionGeometrically Speaking, Thinking Smaller Might Produce …
July 30, 2015
University of Florida scientist develops compact planting bed formula that cuts water, fertilizer, and pesticide use in half. Read More
GrapesDrought’s Impact On California Winegrapes
July 30, 2015
The impact is minimal this year, but the future is uncertain if the drought continues. Read More
Apples & PearsEPA Approves New 1-MCP Technology
July 30, 2015
EPA approved Fysium, a new 1-MCP product from Pace International LLC. Considered new technology, this product is produced on-site by Read More
Crop ProtectionNew Fungicide Targets Key Diseases
July 30, 2015
This disease control tool hits two different parts of the fungal life cycle. Read More
CitrusWestern Growers Praises Introduction Of California Emer…
July 30, 2015
Legislation contains short- and long-term provisions to deal with the historic drought. Read More
Farm ManagementFour Great Pricing Tips From U-Pick Experts
July 30, 2015
Although each of the growers I talked to has his or her own take on a pricing structure, they all Read More
BerriesUC-Davis Responds To California Auditor’s Recomme…
July 30, 2015
Following a six-month review of the University of California (UC)-Davis Strawberry breeding program, the California state auditor’s office has released Read More
Farm ManagementHow To Find Your Perfect U-Pick Pricing Structure
July 30, 2015
If there’s one mission impossible for pick-your-own operations, it might just be how to set a pricing structure. Odds are you’ve Read More
CitrusGroup Food Safety Audits May Help Prepare You For The P…
July 29, 2015
Group food safety audits, slated to be available next spring, may save small- to mid-size growers time and money. Read More
PotatoesPotato Production And The Environmental Component Of Pl…
July 29, 2015
Part of being prepared for unusual weather patterns means being on the lookout for problematic pathogens and other pests. Read More
Farm ManagementUnited Farm Workers Turns Up Heat On California Growers
July 29, 2015
With temperatures soaring into the triple digits, union organizers are focusing on heat illness regulations. Read More
Apples & PearsResearch Is Vital To Keep Asian Apple Export Markets Op…
July 29, 2015
With the large domestic production of U.S. apples in recent years, Asian export markets (China, etc.) are vital. This is Read More
Disease ControlNew Disease Control Tools For Fruit And Nut Growers
July 29, 2015
Apple scab is a big problem for growers in the Midwest and East. But, a new fungicide boasts efficacy against Read More
IrrigationRiver Point Farms Sets Standard For Water Application, …
July 28, 2015
Efficient systems help the Oregon farm, one of the largest onion growers in the U.S., achieve high yields while minimizing water inputs. Read More
Produce aisle leafy greens super market grocery store
Food SafetyLGMA Members Get High Marks In Food Safety  
July 28, 2015
The California Leafy Green Marketing Agreement’s (LGMA) annual report shows the group received the lowest number of citations in its history. Read More
FruitsFruit Grower Tour Held Next Week In New York
July 28, 2015
Registration begins at 9:30 a.m. on Aug. 5 for the 17th annual Wayne County Fruit Grower Tour presented by agr.assistance. Read More