November 20, 2015
— written by Clark Neely, Small Grains Specialist
Retaining Volunteer Wheat
A unique situation is unfolding for many wheat producers across the state of Texas this fall, particularly for areas of the Blacklands, which started back in the spring. Torrential spring rains destroyed or otherwise prevented harvest of many wheat acres throughout Texas in 2015 providing a large seedbank of wheat seed in the soil. Once fields were abandoned or insured out, drought quickly set in for much of the summer months, allowing seed to sit dormant in the soil. Another round of intense and widespread rain at the end of October set the stage for a timely and uniform stand of volunteer wheat. With wet conditions continuing through November, the excessive rain this fall has prevented a number of acres from being planted and leaving many producers wondering, “Will my volunteer wheat make a grain crop?”
The short answer is “Yes it can” under the right conditions. Due to the timing of the rains in October, many of these volunteer wheat fields emerged within or close to the optimum planting window for typical wheat planting throughout the Blacklands and Central Texas. Producers need to next estimate wheat stands and uniformity. General recommendations for wheat stand establishment are between 10 and 25 plants/ ft2, though irrigated or high-rainfall environments favor the higher end of this range. Yield will generally begin to decline below 10 plants/ft2, unless favorable weather conditions (warm winter and/or cool spring) allow for additional tillering. Stand counts above this range can possibly lead to lodging, but will depend on multiple variables.
High rainfall and high fertility can exacerbate lodging problems, especially with thick stands in wheat. Straw strength also varies considerably among varieties. Fannin and Duster are two common varieties in Texas that are known to lodge more easily than other varieties, while varieties such as TAM 304 and WB Cedar are rated as very good or excellent for straw strength. Some producers may consider a growth regulator in the spring to shorten internode length and overall crop height in hopes of reducing lodging potential. While there is research showing that these products can shortened plant height under certain scenarios, results have been inconsistent on reduced lodging.
Another major consideration for growers should be disease observed in their wheat crop from the previous year. Head smuts and bunts can survive in infected seed and infect the following year’s crop. These diseases can multiply rapidly from one year to the next. They are easily treated with seed treatments, but that is not possible with volunteer wheat. Producers should also be aware that any viruses, such as Barley Yellow Dwarf and Wheat Streak Mosaic Virus, present in the previous crop will be transmitted to the following crop via the seed. These diseases can be devastating and symptoms are typically worse the earlier a field is infected.
Producers must remember that volunteer wheat is uninsurable, which does provide additional risk for their farm.
Late Planted Wheat
As mentioned earlier, acres intended to be planted in wheat this fall (that do not have volunteer wheat in them) have been or continue to be delayed. When planting after the ideal planting window, some options producers may want to consider include increased seeding rates or selecting an earlier maturing variety. Seed availability this late in the season may or may not be limited.
The general consensus is that seeding rates should increase by 30-60% for late planting wheat, so a 60 lb/a rate under an ideal planting date would now be 78 to 96 lb/a for delayed planting. Increased seeding rates are thought to compensate for reduced tillering in plants due to a shortened growing season. The majority of winter wheat planted in the Rolling Plains and Blacklands is planted between mid-October and mid-November. Producers may want to consider increasing seeding rates after December 1st. Final planting date for individual coverage plans for insurance is December 15th for the Rolling Plains and Blacklands.
Some examples of early maturing varieties include WB Cedar, Billings, TAM 401, and Fannin for hard red winter wheat and AGS 2035, USG 3120, SY Cypress, and LA 754 for soft red winter wheat.
If planting is delayed into January, producers will need to seriously consider whether it is worth planting wheat. Generally, winter wheat receives enough chilling hours to vernalize if planted on or before early January in the Blacklands or Rolling Plains; however, wheat planted in late January or later may not have enough cold to switch the plant over from vegetative to reproductive growth and prevent the formation of a seed head. In this case, spring wheat would be advised since it does not require vernalization. In either case, yield potential is greatly reduced by planting that late into the season.
Spot Sewing Wheat
Despite best efforts, wheat stands can still emerge unevenly due to weather or other factors, leaving one to wonder if spot planting should be considered. While this decision is often not clear-cut, the best tool a producer has is to take stand counts and determine if stands are less than ideal. Generally, replanting is considered once stands are below 50% of the desired level in a given area. When planting overtop of a thin stand, it is best to seed at a 45 degree angle to the original row direction. Double disk openers are preferred over hoe drills as they do not destroy what remains of the original stand. When over-seeding on a previous stand with a double-disc opener, a 40 to 60 lb/a rate may be desirable, but rates should increase slightly with hoe drills. This rate will need adjusted according to remaining stand and timing of the replanting.
When spot sewing or over-seeding poor stands of wheat, it may be advantageous to plant an earlier maturing variety to compensate for planting later; however, it is difficult to perfectly align harvest timing of the two plantings perfectly and would only work if the original variety planted was medium or later maturity.
For additional information planting/replanting decisions please refer to Texas A&M AgriLife Extension publications:
Wheat Replanting Considerations:
Stand Establishment of Small Grains and Annual Grasses for Grain and Winter Pastures (SCS-1999-23):
Wet and saturated soil conditions at germination can be a major issue with emerging wheat plants. A germinating wheat seed respires like many other living organisms, which means it needs oxygen to live and grow. Saturated soils replace the available air in the soil with water and limits oxygen availability to germinating seeds and established roots of larger plants. This can delay germination or kill seeds and seedlings, thereby reducing stands. Wet soils promote the growth of many soil borne pathogens as well, which can lead to infection. Some examples of diseases that thrive in wet conditions include root rots, take-all, soilborne mosaic virus. Although not a full-proof strategy, fungicide seed treatments can help prevent or delay many seedling diseases (excluding viruses) under these less than ideal conditions. For more information on disease identification and seed treatments please visit: http://amarillo.tamu.edu/amarillo-center-programs/extension-plant-pathology/wheat-publications/ .