It’s all about tillers and tiller survival

In order to maximize grain yield, we need between 500 and 900 heads/sq. yd. at harvest.  Wheat sown at 1 bu/ac will generally result in about 175 seeds/sq. yd. meaning that we will need at least three tillers per seed that go on to make a wheat head. Not just any tiller will suffice. If a tiller does not have three large, unfolded leaves by jointing, there is a good shot that it will not make a head.

One of my primary concerns right now is  tillering in many Oklahoma wheat fields will be insufficient to reach the critical 500 heads/sq. yd. number. Even though most of our wheat was sown in October, a lot of it will have a November or December (if we are lucky) germination date. A K-State study from 1995 showed that wheat emerging on November 30th produced an average of only 1.8 viable heads per plant at harvest. If we had known that our emergence date would be in November or December, we would have compensated by doubling or tripling our seeding rate.

September-sown wheat that got a good start but is now backpedaling due to a lack of moisture is a different issue. In the same study mentioned above, wheat emerging October 12 produced 1,850 tillers per plant on average. Only 476 (26%) of these tillers made it to harvest, so it is normal for early-sown wheat to slough off several tillers. This has an energy cost to the plant and is one reason early-sown wheat generally yields less than October sown wheat. We have enough tillers present in our early-sown wheat but are losing them quickly. Rain is needed quickly to stop the losses.

Agronomists are second only to lawyers in including disclaimers and qualifying statements, and there is a lot of wiggle room in the numbers I have provided. A variety that typically produces larger heads (e.g. Billings) can be on the lower end of the 500 – 900 head range and a variety with smaller heads (e.g. Duster) will need to be on the upper end.With a warm winter and rainfall, we could still hit these targets. However, to borrow some terminology from Vegas, I think there are fairly low odds that our wheat will cover the spread when it comes to tillering this year.

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About Amanda De Oliveira Silva

I have served as an Assistant Professor and Small Grains Extension Specialist at Oklahoma State University since August 2019. I believe that close interaction with producers is vital to understand their production strategies and to establish realistic research goals. My program focuses on developing science-based information to improve the agronomic and economic viability of small grains production in Oklahoma and in the Southern Great Plains.

6 thoughts on “It’s all about tillers and tiller survival

  1. Jeff, Nice topic to point out. So, is it best to redrill anything that has marginal stands and run the risk of stand damage to thicken it or leave it and see how the spring treats us. I think back to Western Kansas and Eastern Colorado work that showed that you don’t need many plants in the fall, you just need potential to create productive tillers. This always ran the line of thought to minimize soil moisture utilization as a means of survival to capitalize on improved conditions when or if they came. It is an interesting dynamic. Another question, we realize duster has smaller heads, but since it has such a great tillering ability, will it compensate somewhat for thinner stands or is this ability of flexing tiller numbers going to hurt duster this year. May be convenient for many that they base seeding rates on pounds and not seeds – get more seeds in the ground with duster :).

  2. Hmmmm…1850 tillers per plant?? Even over here in the wilderness of the northeast corner that seems a bit high.

    Thanks for this blog, Jeff. Definitely a nice way to exchange ideas and interact.

  3. Kent, I have debated the concept of redrilling. With no soil moisture present and none on the horizon, I don’t think the added expense of drilling in additional seed would have much chance of paying off. If we get moisture and have a mild winter, we can still get a few tillers. The catch is that spring tillers generally produce smaller heads with less grain. Tillers are easier to discuss, but what we really need is complete canopy closure by jointing.

    You pointed out the two advantages of Duster in this scenario. More seeds per lb = more seeds per acre and it is a prolific tillerer (if that is a word). It will do a better job of compensating than something like Overley but will still not be able to regain full yield potential.

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