Farm Progress

What do research trials show?What is a good plant population?

David Bennett, Associate Editor

June 19, 2015

6 Min Read
<p>&ldquo;THE REALITY IS we have a lot more (grain sorghum) acres than the past few years combined,&rdquo; says Jason Kelley, Arkansas Extension grain sorghum agronomist.</p>

Drive up and down Delta roads and one thing is abundantly clear: grain sorghum acreage is booming.

“We have a lot more acres of grain sorghum this year in Arkansas than last year,” says Jason Kelley, Arkansas Extension sorghum agronomist. “Actually, the reality is we have a lot more acres than the past few years combined. That’s largely due to price and, right now, China is driving the market.”

The March planting intentions report had Arkansas estimated to plant about 250,000 acres. “But I believe we’ve far exceeded that number – maybe 350,000-plus. Last year, we had 160,000 so we’ve likely more than doubled that. And considering the troubles we’ve had getting planted with the wet spring that’s impressive.”

Arkansas, says Kelley, has a lot of producers that haven’t grown grain sorghum in 20 or 30 years. “Others have never grown it so it’s all new for many.”

Even when the producers hadn’t taken such a shine to the crop, University of Arkansas researchers have been researching how best to manage grain sorghum in the state.

“The Arkansas Corn and Grain Sorghum Research Promotion Board have really been pushing for research with the checkoff funds they disperse. The Arkansas checkoff has been in force since 2000. So, for the past several years we’ve had an ongoing focus on grain sorghum, looking at ways to improve yields and profitability.”

A large milo trial on the Lon Mann Cotton Research Station outside Marianna, Ark., is funded by the checkoff.

“We’ve done work on fertility, planting dates, seeding rates, diseases, all kinds of research that could improve yields. We now know what impacts yield and what doesn’t, but are always looking for ways to get that extra bump in yield.

“In the trial by the highway, we wanted to put together all of the knowledge we’ve accumulated so far. The basic goal is to find a way to grow 200-bushel grain sorghum. Is that realistic? Well, last year, there were some fields – or areas of fields – that approached that level. That was somewhat surprising since our state average yields over the past few years have been in the 85- to 100-bushel-per-acre range.”

The National Grain Sorghum Producers have a yield contest every year. The national winner for the last five years has been over 200 bushels. “It may not happen annually, but when things come together properly, those kinds of yields are achievable.

“So, we’re looking at several inputs in the trial. We’re comparing normal extension recommendations with an enhanced level program. Individually, we increased seeding rates, put out foliar fungicides, added extra fertilizer, and used deep tillage and in-furrow starter fertilizer. Then, we combined all five inputs together.”


Kelley and colleagues have done that trial for two years in two locations (Marianna and Rohwer). “So, we have four trials to draw data from. It’s interesting because our normal recommendations gave us at least 90 percent of the yield potential. Now, 90 percent may not sound that good but, in reality, for that last 10 percent we spent a lot of money and didn’t get enough of a yield boost to pay for the extra inputs.   

“We also do research verification fields around the state. The corn and grain sorghum verification program is designed as a teaching tool for county extension agents and producers to learn how to grow grain sorghum. Ultimately, that provides in-field training and gives us a database showing real-world input costs and what kind of profits we had.”

What are some typical questions Kelley is being asked?

“This year, everyone wanted to plant early. The sugarcane aphid that hit some fields last year had a lot to do with that. Many of those that did get planted early saw the crop struggle with all the cool, wet weather we’ve had. For a while, it seemed to rain every other day. Grain sorghum doesn’t do as well as corn in those conditions and that meant we saw slower grow-off. 

“I’ve fielded a lot of questions about plant population. ‘What can I expect at X level? At what number should I just start over?’ A lot of our plant population research shows the crop is pretty non-responsive to plant population. Early-planted grain sorghum can do a lot of tillering and can compensate for thin stands.

“In the trials we’ve done on irrigated grain sorghum, if I have a uniform – and that’s a tall order in some of these fields -- 40,000 to 50,000 plants per acre, I’m leaving it. That’s more than an ample plant population. Of course, it doesn’t look like much if you’ve planted at 100,000 seeds per acre. Half a stand is hard to stomach but, oftentimes, that’s perfectly adequate.”

Kelley has conducted planting date trials in Marianna for six years. Every year, when planting in April, he’s seen maximized yields. “Once we got to mid-May, the yields dropped off, even with irrigation.  June plantings are risky because of lower yield potential, sugarcane aphid concerns, and slow grain dry-down at harvest.”


Herbicide drift is also a big issue this year. “More grain sorghum acreage means more problems with glyphosate drift. We’ve had a lot of those, unfortunately. With the weather, a lot of plants turned purple – but that was a normal response in many instances. Now, there were a lot of fields that were more purple, or red, than they should have been. It turns out many of those fields were suffering from glyphosate drift as well as cold wet weather.

“Drift is one downfall we’ve seen in 2015. When the weather is poor, everyone is scrambling to make things happen. When we had a day, or two, before the next rains came a lot of spraying occurred. Unfortunately, we had a lot of fields – still do, actually – with drift injury. We’ve learned grain sorghum is very sensitive to that. It doesn’t take much to cause symptoms show up. Some fields have been destroyed and had to be replanted. Others had severe enough damage, and it was late enough in the season that soybeans were planted where atrazine had not been applied.”

Kelley comes back to the fact that the trials haven’t shown much difference between yields following normal Extension recommendations and those with enhanced inputs. “We added a lot more fertilizer -- $100 worth, -- to some of these plots and got a three-bushel response. That’s it.

“Much of this grain sorghum is developed and bred in west Texas where it’s drier and in a much more arid region. We bring hybrids into the Delta and they yield well but sometimes aren’t capable of handling the foliar disease levels. That may be why, out of all the enhanced input trials, the foliar fungicides gave us the best yield response.

“This year, many producers are putting grain sorghum on some of their good irrigated ground and treating it like a crop and I think many will be rewarded with good yields at harvest.”

About the Author(s)

David Bennett

Associate Editor, Delta Farm Press

David Bennett, associate editor for Delta Farm Press, is an Arkansan. He worked with a daily newspaper before joining Farm Press in 1994. Bennett writes about legislative and crop related issues in the Mid-South states.

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