Assessing the Spring 2019 Kentucky Winter Wheat Condition
Dr. Carrie Knott— Extension Grain Crops Specialist
Most of Kentucky is reeling from the “unusual” weather conditions we have had since last fall. In general, the fall was much cooler and wetter for much of Kentucky than the 30-year averages would have predicted. There have also been periods of >60°F temperatures, such as Christmas and this past week, which are not all that unusual for Kentucky. However, the temperature swing from 4°F to 60°F in just a couple of days this past week is a bit unusual.
These conditions have resulted in many wheat fields that were planted “early” this fall to be the fields with “adequate” growth (Figure 1). And unfortunately, the fields that were planted “on time”, i.e. within the University of Kentucky’s recommended planting window, to be developmentally delayed (Figure 2). In addition, the considerable precipitation, cool temperatures, and limited sunlight this winter have resulted in many wheat fields with considerable yellowing (Figure 3), reduced stands, and the potential for plants heaving out of the ground.
In general, wheat plants are extremely resilient and can recover from considerable stressors endured during the winter. As such, it is typically not profitable to terminate wheat fields to plant full-season soybean. However, given the extreme conditions this fall and winter, coupled with the fact that many fields planted in late October and even into November have barely emerged from the soil, there may be some wheat fields that may be more profitable in a full-season soybean production system rather than a wheat/double-crop system.
To determine the condition of wheat fields, and ultimately whether to continue with a wheat crop or to change to a full-season soybean crop, tiller counts will be necessary at Green-Up (Feekes 3). In general, the number of tillers for a 3 foot section of row are counted at several representative locations throughout the field. Only count tillers that have at least 3 leaves per plant. To convert tiller counts to tillers per square foot, first multiply your average tiller counts by 4, then divide by the row width in inches.
Example:
Average tiller counts of 200 for a 3 foot length of row with 7.5” row widths
(200 x 4)/7.5” = 107 tillers per square foot
Generalized estimates of the expected yield potential based upon the number of tillers (and plants) per square foot at green-up can be found in Table 1. Additional information on tiller and stand counts can be found in Section 3: Cultural Practices in A Comprehensive Guide to Wheat Management in Kentucky.
Table 1. Wheat yield potential for a range of tillers and plants per square foot.
Figure 1. Wheat stands in winter of 2019 that were planted in early October 2018, Princeton, KY.
Figure 2. Wheat stands in winter of 2019 that were planted the third week of October 2018, Princeton, KY
Figure 3. Wheat stands with yellow and drowned areas in the field.