Authors: Romulo Lollato, Mary Knapp

The week of March 8 - 14 brought to most of the wheat in Kansas some colder temperatures to help slow down crop development, to a certain extent. Mean temperatures during that period ranged from slightly above 32° in the northern tier of counties, to as high as about 50° F in the southeast portion of the state (Fig. 1). Compared to the long-term normal, weekly temperatures were below average for most of the central portion of the state, but above normal in western Kansas.

Figure 1. Weekly mean (upper panel) and departure from mean (lower panel) normal temperatures for the week of March 8 – March 14.

While these cooler temperatures helped hold crop development back to a certain extent, producers are concerned with possible winterkill, as coldest air temperatures were below 20° F for most of the western third of the state, reaching values as low as 9° F near Tribune (Fig. 2). These temperatures are enough to cause damage to developing wheat, provided that the growing point is above ground (jointing or later stages).

Figure 2. Coldest minimum air temperatures during the March 8-14 period.

While the western third of the state had temperatures lower than the damage threshold for jointed wheat, the majority of the fields in that region are not yet at that stage. They are just now greening up and the growing point is well protected below ground. In regions where the crop is further along in development, such as south central and southeast Kansas, temperatures did not reach critical limits to damage the growing point. Additionally, soil temperatures were consistently above freezing, with exception of a few isolated pockets in north central Kansas (Fig. 3), which should also help insulate the growing point and protect the crop in most areas of the state. Thus, we don’t expect to see serious damage from the latest cold spell to the wheat crop.

Air temperatures were cold enough to cause leaf tissue damage, though. Many fields between Sedgwick and Saline Counties reported yellowing of the fields (Fig. 4), which is caused by leaf tip dieback from cold damage. As long as the growing point is intact, this damage should be mostly cosmetic and should not hurt yields. Thus, we believe that this cold spell will, if anything, be good for the crop by slowing its development for the time being. For a more detailed crop development by variety, please see the accompanying article on first hollow stem in this issue of the Agronomy eUpdate.

Figure 3. Weekly average (upper panel) and coldest (lower panel) soil temperatures at 2” depth.
Figure 4. Yellowing of bottom parts of the field (upper panel) caused by leaf tip dieback (bottom panel) resultant from cold temperatures. Photos by Romulo Lollato, K-State Research and Extension.

In addition to cold temperatures, moisture also remains a concern throughout the state. While the northwest and the eastern portions of Kansas received precipitation either as rainfall or snowfall during this last week (Fig. 5), totals were very limited (less than 0.15” for most of the state) and should not benefit the crop a great amount, except in far eastern Kansas. The majority of the state is still in need of more significant precipitation, which would help both relief drought stress and, in many regions, ensure the fertilizer is in the root zone.

Figure 5. Weekly precipitation (upper panel) and snowfall (lower panel) totals for the period of March 8 – 14.

Romulo Lollato, Wheat and Forages Specialist

Mary Knapp, Weather Data Library