What happened to my winter wheat?

Winter wheat is said to have nine lives. While winter wheat has repeatedly proven its toughness, the 2012-13 season has provided exceptional challenges.

Many producers chose to plant the crop into dry or marginally soil in the fall of 2012, hoping for rain. In many cases, the rains did not come and the crop went into the winter without germinating. Some fields suffered wind erosion, sealing the crop’s fate. In other cases, moisture came in the form of snow and/or rain. Some locations received just enough moisture to mold the seed; others enough to germinate and get it started growing. In some areas, both scenarios occurred, with the difference being the amount of surface residue on the field and how much snow was trapped.

When the snow melted, most of us fully expected the wheat to take off and grow. Of course the crop faced another challenge as air temperatures, and consequently, soil temperatures stayed cold for an extended period of time.

Under good growing conditions, the wheat seed will send out the main root, followed by several seminal roots, and then the coleoptile, which is a leaf sheath that encloses and protects the embryonic plant. The coleoptile continues to grow, and when it emerges from the soil, stops, and the first true leaf pushes through the tip. Leaves are then produced at a rate of about one every 4-5 days. At the 3 leaf stage, several important changes occur. The crown is developed, the first tiller is developed, and the secondary root system is initiated.

In the spring of 2013, these tender young plants were subjected to multiple stresses, long periods of cold soils, slow growth, and marginal moisture conditions. During the entire time, the plant is respiring and using energy reserves from the seed as it is unable to generate its own energy from photosynthesis until it has some green leaf tissue above ground. Seeds that were planted very shallow into no-till seedbeds and seeds planted into fields that suffered wind erosion may have tried, or are still trying to send secondary roots into a duff layer or dry soil and unable to thrive.

Each tiller relies on its own adventitious (secondary) root system, and the plant gradually becomes more dependent on the adventitious root system as it develops to become the predominant root mass. If the plant undergoes stresses during its development, it will respond by producing fewer tillers or by aborting tillers. Lost tillers can often be traced back to stresses the plant was subjected to. Late developing tillers contribute little to overall yield, and tillers that emerge after the fifth main shoot leaf are likely to abort or not produce heads.

If your wheat crop has a reasonable stand, is developing secondary roots and viable tillers, it has a chance of producing a respectable amount of grain if soil moisture isn’t severely limiting. The remaining hindrance to yield will be the inherent lateness in maturity, and the risk of high temperatures that are likely to occur in late June and early July when the grain fill period will be taking place.