Some farmers in Kansas and Nebraska are still planting winter wheat, and with the recent sharp drop in temperatures, they may be wondering if planting wheat is all for naught.
Romulo Lollato, Extension wheat specialist at Kansas State University, said the drop from 80 degrees on Oct. 25 to 20 degrees on Oct. 27 could have no impact on some fields, and significant injury on others. The consequences are field specific, dependent upon location, soil moisture and quality of stand establishment.
“The moisture level in the topsoil will be important to help buffer possible injuries resulting from cold temperatures,” Lollato explained.
Soil moisture is generally good in most of the state due to early-October rainfall, which will cause the soil to have a better thermal buffer capacity, compared to a dry soil. In fact, soil temperatures at the 2-inch depth did not fall below 44 degrees F at any of the K-State Mesonet (http://mesonet.k-state.edu/) weather stations as of Oct. 27 at 7 a.m. These warm soil temperatures could definitely help buffer any negative effects of the sharp temperature drop.
Exceptions could be fields planted in heavy no-till residue where the furrow might not have been closed properly at sowing, or where there was not good seed-soil contact, Lollato said.
“Under these circumstances, the lack of furrow closure results in a less protected seedling (and in some fields, crown) which might be more exposed to cold temperatures,” he said.
Producers are encouraged to start checking for possible injury on lower portions of the fields and especially in no-till fields with heavy residue. The cold temperatures also will be more likely to cause injury to wheat if the plants were showing drought stress symptoms plus areas of extreme cold. Dry soils get colder more easily than wet soils. “Additionally, the drier and looser the seed bed soil is, the greater the potential for the planting to be exposed to cold temperatures resulting in injury,” Lollato said. “Meanwhile, firmer and moister soils should help to minimize rapid fluctuations in soil temperatures allowing the wheat to better withstand cold temperatures.”
Is the wheat up yet?
“Another factor affecting wheat’s response to the cold is whether the wheat had time to become properly cold-hardened. It is important to remember that a large portion of the Kansas wheat crop has been planted recently; therefore, it is still too early to suggest that the wheat has been cold-hardened,” he said. “In fact, many fields have not even emerged at this point or are just now starting to emerge.”
In fields that have not yet emerged but in which seeds are already sprouted, no significant injury should be expected for two main reasons:
- First, recently sprouted wheat generally handles temperatures above 5-10 degrees F well, and air temperatures never reached those levels.
- Secondly, recently sprouted wheat is still below the soil surface and the warm soil temperatures will likely help buffer the seedling from being damaged by the cold.
In fields where the crop has already emerged, temperatures of around 15 degrees F or less can injure the newly emerged wheat, and these limits decrease as the crop progresses to tillering later in the fall and become more cold-hardy. Thus, some fields in western Kansas where the crop has recently emerged, especially the northwest part of the state, could sustain some level of damage. We likely won’t know for sure until temperatures warm up and give us an opportunity to scout, Lollato said.
If fields were affected, the first symptom will be burndown of the wheat from these cold temperatures. If the wheat was bigger-than-normal, the plants may look “rough” with a lot of brown, dead-looking foliage on the soil surface. That doesn’t mean the plants are dead. The important factor will be whether the crown below the soil surface remains alive. Having a well-developed secondary root system will help the plants survive. As temperatures did not drop as low in the central portion of the state, the concern with possible cold injury is not as great as fields that recently emerged in northwest Kansas.
Bill Spiegel can be reached at 785-587-7796 or firstname.lastname@example.org.