It’s all about the tillers, at least when it comes to maximizing wheat profits and yields.
“Whenever you talk about maximizing wheat profits and yields, you’re really talking about managing your tillers. We have to make sure we have enough of them,” says Randy Weisz, professor of crop soil science at North Carolina State University.
At about 10 days after planting your wheat, the individual seeds start to emerge from the ground, he explained during the recent Alabama Corn/Wheat Short Course, held in Shorter.
“Then, a week or so later, where you had an individual spike, now you’ve got a plant with three leaves on it. Finally, when the fourth leaf comes on the plant, the tiller also emerges.
“The tiller basically is another stem — a semi-independent plant.
“After the fourth leaf, another tiller will emerge. From that point on, with each leaf that emerges from this main stem, a tiller will be produced between that leaf and the stem,” he says.
Ideally, whenever the vegetative growth ends, the plant will have lots of tillers on it, says Weisz.
The number of tillers matters because each tiller can produce only a single head, he says.
“So if you want to have a high-yielding crop at harvest, you’ll want a lot of tillers out there to produce a lot of heads.
“As a very basic rule of thumb, we often think you need about 60 heads per square foot at harvest time to optimize yields. And if we need 60 heads, that means we need at least 60 well-developed, large tillers per square foot at top-dress time,” says Weisz.
In early March, at least in North Carolina, some of those tillers are going to be aborted early in the spring. “That’s why if you want 60 heads to harvest, you want at least 60 well-developed tillers.”
The largest grain heads, he says, will be found in the top of the canopy at harvest. “Those are grain heads that are formed on tillers that were produced in the fall or early winter. If you look lower, you’ll see smaller heads, and those were produced on tillers that developed in the spring. We generally think that about 85 percent of your yields are produced from those large heads from fall tillers,” he says.
Spring tillers are at higher risk to drought stress, they have smaller root systems, and they’re also at risk to low test weight, says Weisz.
“The most important way to get fall tillers is through timely planting because warm temperatures drive tiller development.
“Other factors include seeding rate, good quality seed, and general overall good fertility. Wheat won’t tiller if it doesn’t have nitrogen, so some preplant nitrogen is critical.
“If you have a field that doesn’t have a history of manure application, then some preplant nitrogen — 15 to 30 pounds — is generally a good guideline.”
A late-planted crop — behind soybeans or peanuts — could be harvested with no fall tillers, while a wheat crop planted earlier will have a lot of fall tillers, he says.
“We may not like spring tillers, but we’ll need them if we have a later-planted wheat crop.”
How does a grower get spring tillers?
“In North Carolina, we have brief opportunity for spring tiller development, when weather warms up enough that we get a few days of temperatures at around 55 degrees F. That’s usually around the first part of February.
“Tillering generally ends at what we call growth stage 30, and that’s usually between March 5 and March 15 for most varieties. That’s our normal top-dress time, when most growers are putting the bulk of their nitrogen on their wheat crop. And most of our growers in North Carolina are putting out 90 to 120 pounds of nitrogen at topdress in March.
There’s a brief window of opportunity to get spring tillers on your wheat crop, between the first part of February and the first week or two or March, says Weisz.
“In an average year we have enough warm weather that we can get one or two more tillers per plant. But it requires special management, and more specifically it requires nitrogen.
“We have a general rule-of-thumb in North Carolina that in any field there is no residual nitrogen at the end of January. That may be true for a lot of fields, especially those where manure hasn’t been applied. At no later than the first part of February, you have to apply nitrogen, and that can come with some problems.”
At that time of the year, nitrogen is at a high risk of leaching, of de-nitrification, and it puts the crop at risk to winter kill because the crop begins to grow, he says.
“And then, if we have a week of freezing temperatures, it’ll likely hurt the crop. It also increases the risk of lodging and it increases the disease risk.
“In addition, it costs us money because it means an extra trip across the field, so it’s something we don’t want to do unless we have to do it.”
Growers need to decide how much nitrogen they will put out with that Feb. 1 application, says Weisz.
“The assumption is that you’re going to put out an early application and then come back somewhere around normal top-dress time and finish off the crop. You could put it all out early to stimulate tillers, or you might put out 60 pounds early and come back and put out the last half at March, at top-dress time. Or you might put out one-fourth early and the remainder at top-dress.”
There’s a combination of tiller density and nitrogen rate that’ll make you the most money, says Weisz, and there’s a combination that’ll lose you money.”
A combination of low tillers, and somewhere around 60 pounds of nitrogen applied early and then coming back and finishing off the crop at the normal top-dress time, should make money for the grower, says Weisz.
“A very low tiller count and about 60 pounds of early nitrogen will make you money. Having a high number of tillers and putting out a high nitrogen rate will lose you money compared to just putting out your nitrogen at normal top-dress time.
“It’s not just that you’re putting out nitrogen that you don’t need, but you also lose yield. You put yourself at risk to lodging and higher disease pressure. When you put out a lot of nitrogen at the first of February, it isn’t there when your crop really needs it.”
North Carolina’s basic recommendation states that if you go out at the first of February and look at your wheat, and the density is about 50 tillers per square foot, then you don’t need nitrogen.
“If it doesn’t look good, apply 45 to 60 pounds of nitrogen. If you’re in between the two scenarios, you might still need to put out about 45 pounds of nitrogen.
“If you have around 30 tillers per square foot, we’re recommending about 60 pounds of nitrogen in early February and another 60 pounds at top-dress. If you’re at about 110 tillers per square foot, you’ll actually hurt yourself with more nitrogen.”