Posted September 20, 2019
Wheat's potential is affected by soil temperature, moisture, timing, depth and seeding rates
by Mary Marsh, Communications Intern
It’s September, so you know what that means: time to break out the drills and air seeders and plant some wheat. As you go out, coffee in hand, lunch (that will end up being more or less ‘brunch’) in your little cooler, you have quite a few factors to be concerned about in regards to soil conditions and making sure your wheat has the best chances of surviving.
The basics of picking your planting times and how to ensure the best start for your wheat crop revolve around soil temperature, moisture, timing, depth and seeding rates.
In September we can get a wide variety of weather activities going on. We get some scorching hot and dry days, musty and humid days, chilly days, or sometimes all of the above. With all of this going on, picking the right time to plant is like hitting a moving target. Pair it with the extra whacky weather we have been dealing with, finding a good time to plant will be nothing short of a challenge.
According to Kansas State University’s Agronomy eUpdate from October 7, 2016, the ideal soil temperature for germination is between 54 and 77 degrees Fahrenheit. Anything hotter than around 90 degrees, seeds might not germinate until soil temperatures reach the right levels for germination. Since planting and the beginning part of the growing process for wheat are a race against time, it is important to get the seed in with enough time for it to begin root development and grow a couple of tillers.
Thankfully, the latest seed innovations have helped reduce the chances of having winter damage to the wheat, so being a tad bit late is not as big of an issue as it once was. Still, despite these advancements, having the right moisture at planting is key to proper germination and a successful wheat crop.
The point when the wheat seed begins to take in water is called imbibing. According to Michigan State University Extension, soil should have a moisture content of around 35 to 45% in order to supply the seed with enough moisture to imbibe and germinate.
There is some debate and some strategies when it comes to planting so moisture is just right. Some wait for it to rain and then they plant. This way, there is moisture for certain, and you can go for it right away. Unfortunately, there might be some problems with getting equipment in. On the flip side, you can dust it in and hope for rain, but unless you have a tried-and-true rain dance, this is a risky option. Finally, you can plant seeds deeper to reach the moisture zone, but depending on the depth and amount of moisture in that layer, this too might be an issue. The coleoptile might grow to its full potential and still not break through the soil surface.
Like anything else, timing is key. During planting, you might hear a lot about the “fly-free date” and the different zones that spread out across the state. The “fly-free date” is when the pesky Hessian fly reaches the adult stage and would be unable to lay eggs in the wheat plant. Although waiting a little bit longer can mean avoiding the Hessian fly or aphids that might spread barley yellow dwarf virus, waiting too long may result in a drop in yield.
There are four zones of ideal planting in Kansas. K-State’s extension wheat specialist Dr. Romulo Lollato has done research and concluded that sowing date plays a major role in crop yields. Planting after recommended dates can mean a whopping decrease in yields of up to 3.5 bushels an acre per day.
Recommended planting dates by zone are listed below.
- Zone 1: September 10-30
- Zone 2: September 15-October 20
- Zone 3: September 25-October 20
- Zone 4: October 5-25
Depth is another factor to consider. Ideal placement would be around one inch deep. This allows enough seed coverage and access to enough moisture. Shallower than about 0.5 inch might leave your seed wide open to the elements. You run the risk of exposing the crown to potential winterkill. However, if you have your wheat planted too deep, generally over 2 inches deep, the wheat’s coleoptile that encases the first true leaf might finish growing before even busting through the soil’s surface.
To add another layer of complications, seeding rate is another factor to consider. Seeding rates should be increased if the crop is irrigated or planted later. For every week beyond October 10 in western Kansas, increase seeding by 10 to 15 pounds per acre and in eastern Kansas, 15 to 20 pounds an acre. That being said, there should not be more than 1.35 million seeds per acre. Late seeded wheat can require a 30 to 60% increase in seeding rates. Since the window of opportunity to grow tillers has been decreased, planting more seeds means more primary tillers to compensate.
As planting season begins in some parts of Kansas, choosing the right date to plant is way harder than just putting seeds into the ground. It boils down to having the right climate, moisture and depth. Keep these factors in mind as you plant this season.