1. Cover Crops & Weed Control For Vegetable Crops
Lynn Brandenberger
Department of Hort & LA

2. Why Consider Using Cover Crops?
In the vegetable world:
Lots of clean tillage
Soils in the Southern plains
Tilled soils % O.M.
Long summers
No additional O.M. added
Low O.M. in soils causes:
Poor drainage
Poor aeriation
Low ability to hold
Moisture
Plant nutrients
Loss of production

3. Cover Crops Are. . . Grow in-place O.M. Bottom line: No trucking
No spreading
No food safety concerns
No composting
Bottom line:
Easier
Less involved
But:
Reduced cash-crops

4. Potential Cover Crops Winter Cover Crops Summer Cover Crops
Winter Wheat (HR)
Austrian Winter Pea
Crimson Clover
Pea/Clover Mix
Haygrazer
Sesbania
Growing season
Winter Wheat
Cowpea
Lablab
Harvest 9/25/2015
Pea/Clover mix

5. Weed Management for Vegetable Crops
Can include:
Crop & weed history
Crop rotations
Cover crops
Crop selection
Irrigation
Mulches
Cultivation
Beneficial organisms
Herbicides
And more!
Mention potential types of tools then move on to next slides to go over each type of tool in depth. Don’t get ahead of yourself.

6. Identifying Weeds Know your enemy! Identify Growth season & habit
Annual or perennial
Control measures
Henbit/cool season
The first step in controlling any pest is to identify it. Once we’ve done that we can begin formulate a control strategy i.e. looking in our weed control toolbox and deciding what tools to put into service for controlling the problem.
Remember, a weed is merely any plant growing where we don’t want it to grow. One man’s weeds are another’s crop species.
Cool season weeds vs. warm season weeds i.e. dicot/broadleaf vs. monocot/grassy weeds

7. Crop Rotations & Cover Crops
Considerations:
Type of production system
Right crop mix
Match to field & rotation
Herbicide history
Adv. Vs. Disadv.
Crop rotations should be designed to accomplish several things. First and foremost from a weed control aspect, crops should be selected on the basis of what they will allow the grower to accomplish regarding reducing troublesome weed populations. This really has to do with either bringing in a different cultivation system that allows for reducing weed seed banks or the use of pre or postemergence herbicides that will control problem weed populations. One other approach is the use of crops that will be harvested for hay and the cutting and removal of weed species from the field after emergence.
Second, if the farm is using herbicides as part of a weed control program, consideration needs to be given to the plant-back restrictions that each material has in regard to the potential rotational crop.
Third, rotational crops may also provide other advantages to the production field i.e. addition of organic matter, fixation of nitrogen by legumes, biofumigation potential for some brassica crops such as mustard. Regarding potential biofumigation advantages, gains can be made for both weed control and some disease/nematode reduction. Although this sounds great, these effects will vary between sites because of soil types and climatic conditions.

8. Crop Selection Not all crops are equal! Growth rates Crop height
Shading ability
Cultivation options
Weed tolerance
How quickly a crop grows will have a large effect on it’s ability to compete with weed species within a given field. For example: let’s say carrot is direct seeded and it takes four weeks to emerge to a full stand, if the predominant weed species is Palmer amaranth and if it is relatively warm during the establishment period, the carrot crop will be at a major disadvantage due to Palmer’s rapid development and shading of the emerging carrot crop.
Our second scenario could be the same field seeded to okra. Okra during warm weather will emerge fairly quickly and is also a crop that will grow quickly in warm temperatures. Thus it has a much better chance of competing with Palmer amaranth than a slow and low growing carrot crop.
To be cultivated or not: This really is a good question! Several vegetable crops lend themselves to mechanical cultivation i.e. the “row-crops”. These include crops like sweet corn, snapbean, cowpea, okra, etc. that can be tractor cultivated with all sorts of machinery. This is a big advantage when a production system does not have herbicides available or has chosen not to use them.
But, I thought we couldn’t tolerate any weeds! Some can, some can’t. Crops that will produce fruit that may be handpicked or machine harvested may be able to tolerate some weeds in the field. Good example would be cucurbit crops like watermelon or pumpkin. Crops that have a very low tolerance of weeds in the field at harvest would include all the greens crops i.e. spinach, etc. Seems that most people don’t want pigweed in with their fancy salad greens!

9. Irrigation Irrigation methods Water sources Systems
Overhead
Flood/furrow
Drip
Water sources
Well, surface, municipal
Filtered or not?
The type of irrigation system used for production affects the ability to control weeds.
Overhead irrigation systems waters both the crop rows and between crop rows. This allows weed species access to water for growth and doesn’t really do anything to help control weeds.
Flood/furrow irrigation again waters the entire field benefitting the crop and weed species.
Drip irrigation has the potential to limit water to between row spaces and thereby reduce the amount of water available for competing weed species. Also, drip irrigation water will need to be filtered which will remove most weed seed.
The source of water can have a direct affect on weed seed that may be brought into the field. Pumping water from rivers-streams-lakes or ponds can introduce weed seed into a field. Utilizing water from wells or from other closed sources can eliminate this problem.

10. Mulches Mulching: Application of a covering to soil What mulch does
Mulching is the application of a covering layer of material to the soil surface. This covering may be comprised of a variety of materials including organic materials such as hay, straw, compost, paper. Also plastic mulching materials such as reflective mulches, polyethylene mulches including different colors such as black, brown, green, white, etc.
Mulches may have several effects on the growing environment for crops including managing soil moisture, soil temperature, soil fertility, excluding light and thereby controlling the germination of weed seeds, physical barriers to most weed species.
In addition, mulches can affect soil erosion both from preventing it and also from causing more rapid drainage of fields which may result in more erosion. As one making decisions, growers will need to consider what effects different mulching materials may have.

11. Cultivation Cultivation is: Use of mechanical weed control for crops
Can be sole method
Can combine with herbicides or mulches
Spring cultivator
Cultivation is the mechanical control of weedy species in a crop. Cultivation generally refers to the use of either hand tools or powered equipment to till the soil to uproot weeds while leaving the crop relatively undisturbed. When cultivation is used there is an associated cost involved. Obviously the cost of labor and equipment, but also the cost of lost production from crop injury sustained from cultivation.
Weed control through cultivation has been used for millennia to control weedy species within crops. It is still used by many farmers for controlling weeds. People across the globe still use cultivation and in fact, in many developing countries it is the only means of weed control used. One issue that should be considered is the amount of time and labor that may go into hand weeding. In the developing world, farmers are often limited by hand weeding to a small acreage and thereby to reduced profit potential. In the developed countries this is often not the case because of the availability of capital and equipment for weed control.

12. Herbicides for Weed Control
Why are there so few?
Vegetables are:
Often very sensitive
High value/high risk crops
Low acreage crops (Minor use crops)
Adds up for chem. company
High risk for lawsuits
Low potential for profit
What is being done?
USDA IR-4 project
Works with EPA to register pesticides for minor use crops
24C SLN labels for pesticides
Check County Agent’s handbook
It really boils down to this: Because vegetables are often very sensitive to herbicides and because any specific vegetable has relatively few acres in the U.S. chemical companies are reluctant to develop and register herbicides for use in these crops. Bottom line: for the Chemical companies vegetables are a high risk and low profit potential group of crops, therefore USDA uses the IR-4 project and collaborates with EPA to research and work towards registration of all pesticides for minor use crops i.e. vegetables and fruits.

13. Conclusions Identify Understand production system Control strategy
Multiple aspects
Cultural
Biological
Chemical

14. 2018 Horticulture Industry Show
Friday & Saturday January 5-6, 2018
At: TCC in Tulsa, OK Registration open November
Contact: Becky Sellers at or or

15. Perkins Spray Day Spring 2018 Sprayer set-up Sprayer tune-up
Sprayer calibration
Pesticide rates & calculations
Pesticide Safety