Winterkill in wheat and potential yield loss
With the recent warm weather and wheat greenup, it should be a little more apparent now where stands have suffered winter damage. If damage has occurred, how much affect might this have on yield potential?
Wheat is a resilient crop, so there is no way to be precise about yield loss based on a certain level of damage from winter injury or a freeze. But a K-State study at four locations (Belleville, Hays, Hutchinson, and Manhattan) over five years (2002, 2003, 2006, 2011, and 2012) gathered data on this topic. The results allow us to make some general conclusions.
To simulate winter damage and late-season freeze injury, we blended a Clearfield and non-Clearfield variety then sprayed the blend at different times of the year with Beyond. This killed the non-Clearfield variety. One limitation of the study is the stand was reduced uniformly within the row as opposed to large areas being damaged.
The blends consisted of different ratios of the two varieties. As a results, we simulated winter damage levels of 0, 33, 50, 67, and 100 percent. We also tested different timings of the damage: fall, spring greenup, and flag leaf.
Compiling the 20 site-years of data, we found the following:
- Fall damage had a small negative impact on yield (8-27 percent), but only when stand reductions were greater than 50 percent. This suggests there is usually time for wheat to compensate and recover from stand loss in the fall.
- Damage at spring greenup had a larger negative impact on yield (10-41 percent). The maximum reduction occurred when stand loss was greater than 50 percent.
- Late spring damage at the flag leaf stage resulted in the largest yield decrease (14-60 percent) at all stand reduction levels. This shows that any late-season damage can decrease grain yield.
Jim Shroyer, Crop Production Specialist Emeritus
Kyle Shroyer, Agronomy Graduate Research Assistant