MSU Extension Wheat

With the abundance of prevented plant acres in Michigan this year, there is significant interest in planting wheat early. Early planting is always associated with higher yields, but can you plant too early? This article will provide some recommendations and context for planting wheat on prevented plant ground.

Planting date matters

Research repeatedly shows that planting wheat early increases yield potential. Data from one research trial conducted in Ontario (Fig. 1) shows that the highest yield potential is the earliest date, and the yield potential decreases the longer you delay planting. But how early can you go?

Historically, we have recommended planting wheat after the Hessian Fly-Free Date. However, it has been many years since any significant outbreak of Hessian fly has occurred, and most agronomists will tell you it is no longer a widespread problem. Even though this pest is no longer a significant concern, the fly-free date is still a good start date for planting wheat from an agronomic perspective.

The target for fall development in wheat is two to three tillers per plant before winter dormancy. This is generally achievable if planting in mid- to late September throughout Michigan. If you plant too early and get excessive tillering before winter dormancy, there is increased risk for lodging the following spring and summer. Get the plant out of the gate and started right, but not too far. Having fallow land available from prevented plant has many farmers wondering how early they can plant. Generally, I would use the Hessian Fly-Free Date as a guide. Do not plant more than a week earlier than the date for your county.

Crop rotation

It is understandable that prevented plant has caused a disruption in normal crop rotation sequences and while this provides an opportunity to get wheat planted early this fall, remember that wheat responds differently with different previous crops. Wheat has the highest yield potential following dry beans and soybeans in Michigan.

Source: Manitoba MASC Harvest Production Reports, 2010-2015.

There is growing interest in planting wheat after sugarbeets for those who are able to harvest their sugarbeets early. This could be a good rotation provided ground conditions are suitable to preparing a proper seedbed for wheat. Rainfall during and after sugarbeet harvest could hamper efforts to conduct the tillage necessary to eliminate compaction layers and prepare the final seedbed for wheat.

Growers that want to plant wheat following corn should use caution—the fusarium pathogen that causes gibberella (mycotoxin) also causes head scab in wheat. If you are planting wheat where corn is the previous crop, make sure you select a variety that has moderate head scab resistance and plan to put a fungicide on wheat at flowering to reduce the severity of head scab. Planting wheat after wheat should be avoided if possible. Mono-cropping cause’s buildup of inoculum and you should expect disease pressure to increase.

Weed management

Weeds need to be controlled prior to planting winter wheat. Weed control on prevented plant acres varies from field to field. Some fields have been treated with herbicides and have good control. Others have been tilled a couple of times and appear to be ready to plant. Fields with poor weed control, newly emerged weeds or fields that haven’t been touched all year need weed control measures prior to planting wheat. Scout fields and make a determination of the best practices for weed control for individual fields.

Below are some of the situations and potential options that can be used for weed control prior to planting winter wheat this fall.

Field has been tilled regularly throughout the season

In most cases, there will be only a few newly emerged weeds in these fields. If you want to no-till wheat in these fields, it will be important to control weeds that are present. Glyphosate (Roundup or other formulations) can be used prior to or soon after planting to control existing weeds. Do not wait too long after planting to make these applications. Waiting too long puts wheat at greater risk to exposure from glyphosate resulting in reduced wheat stands.

There is one caveat to just using only glyphosate: the presence of glyphosate-resistant horseweed (marestail). If horseweed (marestail) is present, treat with a herbicide that will control glyphosate-resistant horseweed. Options for controlling horseweed include adding 1 to 2 fluid ounces per acre of Sharpen to the glyphosate application. A methylated seed oil (MSO) at 1% v/v + ammonium sulfate should be included in these applications. This application needs to be applied prior to wheat emergence.

Using Gramoxone is another option to control weeds, including glyphosate-resistant horseweed, prior to planting. The Gramoxone rate should be based on the stage of the weeds and should include a non-ionic surfactant in the application. Larger horseweed will be difficult to control with Gramoxone. Tillage in these fields prior to planting wheat is also another option to control newly emerged weeds.

Field has been sprayed earlier in the season to control weeds in prevented plant fields

In most cases, there will likely be newly emerged weeds in these fields. Scout these fields prior to no-till planting to make sure an additional herbicide application is not warranted. While the strategies listed above are still options in these situations, look at the maximum cumulative amounts per season of the herbicides previously used. For example, if Sharpen was applied previously on the prevented plant fields, the total amount of Sharpen for the season should not exceed 4 fluid ounces per acre.

Additionally, some of the herbicides used to control weeds in these fields have plantback or rotation restrictions prior to planting wheat. For example, there is at least a one-month rotation restriction if dicamba (Clarity) was applied at 1 pint per acre, and you should wait an additional 15 days for each additional 8 fluid ounces per acre of dicamba used. If Liberty was applied, there is a 70-day plantback restriction to wheat. While there is not specific plantback restriction listed on all 2,4-D labels, some of these labels state not to plant unspecified crops (i.e., wheat) until 30 days after 2,4-D application.

Poor weed control (e.g., large horseweed) or no management on prevented plant acres

In many cases, using only herbicides to control weeds in these fields up to prior to planting wheat will not be successful. Tillage or mowing combined with an effective herbicide application will likely be needed.

Disease management

Be cautious where wheat is to be seeded on prevented planting fields that were wheat in 2018. Based on experience in Michigan, wheat in this rotation may face risks similar to where a wheat crop follows another wheat crop. In particular, there may be an elevated risk of take-all. To lessen the risk of take-all, do not plant wheat early in the fall as it gives the soil borne disease more time to infect the wheat seedlings. The chance of other diseases may also be increased, particularly if there is a “green bridge” of volunteer wheat in the field.

Population/seeding rate

When planting early, reduce seeding rates. Planting high populations early can cause increased risk for lodging potential. If planting before Sept. 15, start at one to 1.2 million seeds per acre. From Sept. 15–Oct. 5, plant 1.2 to 1.4 million seeds per acre. After that, ramp up seeding rates to 2.2 million seeds per acre by late October. Make sure you calibrate your seed drill using the seeds per pound for your seed lot as described in the Michigan State University Extension article, “Seeding the 2020 winter wheat crop.”

Fertilizer

Planting early on prevented plant ground should not change your fertility program for wheat. Follow your normal program and apply phosphorus and potassium in the fall according to soil test results. If phosphorus and potassium were applied for the previous crop but not the crop planted, make sure you account for this. Do not apply more than 10-15 pounds of nitrogen per acre.