Winter Wheat as a Cover Crop

Benefits

• Prevent erosion
• Suppress weeds
• Scavenge excess nutrients
• Add organic matter
• Extra forage

Adaptation

Winter wheat is second in winter-hardiness to cereal rye, and can usually survive in the entire state, even when planted after soybean or corn grain harvest. It can also be planted in the spring, but it will not produce seedheads as it needs to overwinter (vernalization) to flower. Winter wheat is known for providing many similar benefits to cereal rye (erosion control, weed suppression, nutrient scavenging, carbon addition, forage), but to a lesser extent as it produces less above and belowground biomass. This can be beneficial, since wheat also matures later than rye, and is therefore easier to manage in the spring. Dry matter production for wheat planted in early September and terminated in late April to early May can exceed 3,000 lb/A (Figure 1), reaching up to 6000 lb/A in fertile soils.

Some seed retailers that specialize in cover crops may sell "cover crop wheat" or "variety not stated" (VNS) wheat that is clean and germ-tested but lacks predictable characteristics. This may be budget-friendly, but farmers seeking predictable maturity date, disease resistance, or forage yield and quality from winter wheat should seek out varieties that meet those needs.  To determine which variety is best for a particular area, consult the performance data in the

It can be more economical to use bin-run seed for cover crops, specifically with winter wheat, since it is grown as a cash crop and widely available. There are several factors to consider when using this method. First, will the seed germinate and make an adequate stand? Second, is the seed pure, or are there contaminants such as weed seeds? Third, is the seed high quality and free from pathogens to reduce spread to the next crop? Inexpensive purity and germination tests from a seed testing lab help you weigh the pros and cons of using bin-run wheat. The Pennsylvania Department of Agriculture Seed Lab charges from 15 to 19 dollars for germination tests on typical cover crop species. It is illegal to sell bin-run seed to other farmers for planting if the variety is protected under the Plant Variety Protection Act (which is commonly the case for sold varieties).

Fungicide and insecticide seed treatments are available for treating seeds on the farm. These products vary in their active ingredients, modes of action, use rates and restrictions, controlled pests (insects and diseases), and cost. Since yield protection is not a priority for cover crops, the cost of treating the bin-run seed likely outweighs the benefits.

Establishment

For best results in the northern tier of Pennsylvania, plant a winter wheat cover crop by mid to late September. In southern Pennsylvania, winter wheat cover crops may be planted up until mid-October. Winter wheat can survive if planted later but will provide negligible winter cover and have reduced spring biomass. Pure stands of winter wheat should be drill-seeded (6 to 7.5-inch rows) around deep at a rate of 1.5 – 1.7 million seeds per acre (approximately 100-120 lbs/A).  Seeding rate should be increased slightly (~20%) when planting into a poor seedbed or if the planting date is delayed until after the optimum window. Seeding rate should also be for broadcast-seeding. Broadcast seeding success is improved by following up with a cultipacker or shallow cultivation pass. Use the full seeding rate when planning to graze or harvest the wheat for forage. Seeding rate can be reduced to 40 lbs/A in high fertility fields, when seeded early in the planting window, or when planning to delay spring termination and plant green.

Similar to cereal rye, winter wheat can be broadcast interseeded into standing corn or soybeans in late September into October to maximize the window for cover crop growth in the fall using a variety of ground or aerial equipment. However, winter wheat is not recommended for early-season (V4-V5) drill interseeding into corn, due to its poor ability to survive the shading and dry conditions that can be encountered in that system. Wheat is not as competitive in a mixture as cereal rye, and mixes well with legumes like crimson clover, red clover, hairy vetch, and winter peas. In a wheat-legume mixture, reduce the wheat seeding rate to 25 to 50 percent of the monoculture rate (30-60 lbs/A), but keep the legume rate near the monoculture rate. For example, 30 lbs/A wheat + 25 lbs/A hairy vetch, 60 lbs/A wheat +15 lbs/A crimson clover, 30 lbs/A wheat + 40 lbs/A cowpea. For any cover crop mixture, start with an educated guess, plant a small acreage, observe the results, and adjust as needed to meet your cover cropping goals.

Management

Fertility

A winter wheat cover crop can improve the nutrient cycling of nitrogen, phosphorus, and potassium. To promote nitrogen uptake, it is essential to get early growth in the fall before the freezing winter temperatures take hold. Winter wheat can help cycle up to 25 lbs of phosphorus and 60 lbs of potassium. A 4,000 lb/A wheat cover crop can take up approximately 120 lb/A of nitrogen.  

Heavy fertilizer applications for wheat grown as a cover crop are not as essential as they are when the wheat is grown for grain. However, if the goal is high biomass production and to receive maximum benefit from the wheat, applying manure or some fertilizer based on soil test results can be beneficial in fields with minimal history of manure or legumes. Up to 20 pounds of nitrogen and all the phosphorus and potassium recommended by a recent soil test may be broadcast before planting. To minimize fertilizer burn, do not apply more than 15 pounds of nitrogen per acre in the row with the seed.

Like cereal rye, mind wheat maturity preceding corn, as the more mature it gets, the higher the C:N ratio, and the more likely it is that nitrogen will be tied up (immobilization). When preceding corn, increase the proportion of N applied at planting or pre-plant, and decrease the proportion applied at side-dress, but apply the same total N needed to meet your corn yield goal. This helps supply enough N for soil microbes to break down the cover crop and feed the young corn plant.

Weeds

A good herbicide burndown program and uniform winter wheat establishment helps ensure a clean start with less competition from weeds. Burndown herbicides for no-till small grains typically start with glyphosate to provide broad-spectrum weed control. Broadleaf products such as dicamba (Clarity), thifensulfuron+tribenuron (Harmony Extra), or saflufenacil (Sharpen) may be tank-mixed to improve weed control efficacy. Certain POST herbicides may be used to selectively control broadleaf weeds after wheat establishment in the fall or after spring green-up, particularly if you plan to delay winter wheat termination in the spring (i.e., planting green). These products include (Harmony Extra), 2,4-D (2,4-D LVE 4E), and dicamba. Be sure to consult the product label for application timing and rate restrictions related to the following cash crop. Always use correct adjuvants per label guidelines, otherwise, poor weed control could result.

Disease

Managed as a winter cover crop, wheat rarely poses an insect or disease risk. Diseases can be more of a problem if the wheat is planted in the summer or very early in the fall, especially under prolonged periods of high humidity. Growing winter wheat could influence the buildup of pathogens and affect future small-grain cash crops. The use of resistant varieties and other IPM practices can avoid many pest problems in wheat grown for grain. For example, planting after the Hessian Fly Free date can help reduce infestations and their vectored diseases.

Termination

Chemical

Glyphosate is the most effective burndown herbicide for winter cereal cover crops. Actively growing cover crops, sunny warm days, and days where night temperatures exceed 40°F increase the activity of glyphosate. Under these conditions, a 0.75 - 1.5 lb ae/A rate with appropriate adjuvants (surfactant + AMS) should provide good control of winter wheat. Applications targeting wheat before the boot stage are generally effective, but higher rates are recommended if termination occurs after stem elongation. Paraquat (Gramoxone SL) at 0.75 lb ai/A can be used as an alternative to glyphosate for the termination of winter cereal cover crops when they are young but is generally less consistent. See Also: Termination Options for Cover Crops and Winter Cereal Forages (Penn State Extension)

Mechanical

Wheat can be harvested as forage or grazed in the spring, targeting the boot stage. Note that fall grazing is not recommended. If chopped or grazed, regrowth will need to be terminated with an alternative method such as plowing, disking, or mowing before the seed matures.  As with other small grain cover crops, it is safest to kill about 2-3 weeks before planting your cash crop, though winter wheat can work well for planting green because wheat grows slower than rye in the spring, so there is less need to rush to kill wheat in the spring as compared to rye.

If participating in government cover cropping programs, talk with your local NRCS office or Conservation District to be sure your management plans, including termination date, fit within the program so that you are not disqualified.  

Management Summary  

• Seeding rate: Plant wheat as low as 400,000 seeds per acre and up to 1.5-1.7 million seeds per acre(increase 25-50% for broadcast)
• Seeding depth:75-1.5” or broadcast (and incorporate) 
• Biomass accumulation: Up to 6,000 lb /A
• Burndown herbicide: Glyphosate- or paraquat-based programs
• Soil preparation and main crop planting: Apply a larger balance of N upfront before corn to compensate for N tie-up by wheat.