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Don’t overgraze no-till

The drought is worsening and forage is getting harder and harder to come by. Crop residue that was once considered of little nutritional value for livestock has become a staple for Oklahoma cattle producers with depleted pasture and hay reserves. John Holman with KSU in Garden City indicated that grazing of sorghum stalks has become commonplace in western KS as well. Some crop residue can be removed without significant damage to long-term gains in soil structure associated with no-till, but overgrazing can lead to some real problems when the wind comes sweeping down the plain.

Wind erosion is commonly thought of as a conventional-till problem, but in an email exchange, Jason Warren recently indicated that there are a few scenarios where wind erosion could actually be worse in no-till than conventional till. No-till results in a relatively smooth, flat soil surface that, in the absence of residue, has few barriers to slow the wind. So, if we have an easily detached soil type (i.e. a sandy soil), a flat surface, and no residue to hold the ground, then we have a recipe for wind erosion. The same would be true for no-till wheat pasture that has been overgrazed. In a wind-erosion-fighting battle royale, I still prefer no-till to conventional till. However, no-till is not immune to wind erosion and it is important to keep some cover on the soil.

Aside from soil protection, it is important to remember that crop residues have value as reservoirs of nutrients.  An estimate of nutrient removal of grain, fiber, and forage crops can be found on one of Brian Arnall’s Pete Sheets at http://npk.okstate.edu/petesheets If the cattle are grazing the residue in-field, most of the nutrients will be returned to the soil. If the residue is being baled, the nutrients are leaving with the hay bales. You can estimate the value of these removed nutrients using the linked Pete Sheet and current fertilizer prices.

No-till practices to not make soil immune from wind erosion. Adequate cover must be maintained.

No-till practices to not make soil immune from wind erosion. Adequate cover must be maintained.

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.

How dry is it?

It was too nice of a day to stay in the office yesterday, so I checked on our wheat variety plots. I started at McLoud, moved west to Kingfisher, and ended up at Marshall. As indicated by the pictures and captions below, neither the wheat nor my mood improved as I traveled west. I am sure if I had traveled farther west, this would have gotten worse. The bottom line is that we are in desperate need of moisture in Oklahoma. Early-sown wheat is backpedaling quickly and cannot hold on too much longer. Much of the later sown wheat has yet to emerge. We are certainly not on our way to a record year, but everything could still turn out okay……..if it rains.