Winterkill and Tiller Counts

The last two days have lead to some very interesting findings in our wheat research plots at Arlington WI. Winterkill for the most part was limited to areas where ice was standing for several weeks (>2.5 weeks). Winterkill damage was greater in our early (9/14/07) and “normal” (9/28/07) winter wheat planting dates than in our late planted wheat (10/23/07). We hypothesize that this was due to differences in respiration rates. Growth in our early and normal planting dates was greater than we usually get in Wisconsin (main shoot and 2 to 8 tillers per plant); whereas late planted growth was about normal (main shoot emerged). Excessive fall growth would contribute to greater respiration rates thus the potential for increased winterkill under the ice.

One advantage of the winterkill this year for our program will be an assessment of variety tolerance to winterkill. In our variety trial we saw a range of 0 to 60% winterkill. This information will be reported in our 2008 Winter Wheat Variety Trials Results.

The wheat that survived (most of our research was unaffected by the winterkill) has a very good yield potential at this point in the season. Wheat planted on 9/28/07 has a tremendous tiller count. We averaged 7 tillers per plant with excellent stands. This would equate to a Feekes growth stage 3 or Zadoks growth stage 15 (five leaves unfolded) 27 (main shoot and 7 tillers). The delays in N application due to weather may prove beneficial to most WI wheat growers because our tiller counts are so high. Early N on these stands would promote lush growth on the main stem and tillers and would likely lead to higher disease incidence in this dense canopy.