Between planting in the fall and Feekes 4 growth stage (beginning of erect growth) in the spring, winter wheat is vulnerable to environmental stress such as saturated soils and freeze-thaw cycles that cause soil heaving. All of which may lead to substantial stand reduction, and consequently, low grain yield. However, a stand that looks thin in the spring does not always correspond to lower grain yield. Rather than relying on a visual assessment, we suggest counting the number of wheat stems or using the mobile phone app (Canopeo) to estimate the wheat grain yield.
Wheat stem count method. Wheat stems (main stem plus tillers) should be counted at Feekes 5 growth stage (leaf sheaths strongly erect) from one linear foot of row from several areas within a field.
Canopeo mobile phone app method. Canopy cover should be measured at Feekes 5 growth stage using the mobile phone application, Canopeo (http://canopeoapp.com). After accessing the app, hold your cell phone parallel to the ground to capture three rows of wheat in the image and take a picture. The app will convert the picture to black and white and quantify (as a percentage) the number of green pixels in the image. For example, the screenshot here shows a 44.86% canopy cover. (Keep in mind, this app will quantify anything green in the image. So, if you have a weedy field, the weeds will also be quantified in the canopy cover estimate.)
After counting the number of wheat stems or measuring canopy cover using the Canopeo app, the table below can be used to estimate the wheat grain yield. For example, if an average of 51 stems is counted from the one-foot length of a row, the predicted grain yield would be 100 bu/acre. Similarly, if the average canopy cover was 35%, the predicted grain yield would be 100 bu/acre.
|Grain Yield (bu/acre)||Stem Count (number/foot of row)||Canopy Cover (%)|
This table was generated using data from two years and two locations (four different environments). During these two years, wheat grain yield was relatively high. We do not have data for wheat grain yield <85 bu/acre. However, we are continuing this work and hope to capture a wider range of yields to expand this table.
For more information, please see: https://stepupsoy.osu.edu/wheat-production/yield-estimates