A second year of planting corn after wheat didn’t produce the same outstanding results as the first year did for Altheimer, Ark., farmer Felix Smart. But he’s not afraid to try the practice again, once wheat becomes a feasible crop to produce that is.

Two years ago, on June 7, 2007, Smart planted Pioneer 31G71 (HX1, LL, RR2), a drought-resistant hybrid which contains Herculex for corn borer and the LibertyLink and Roundup Ready traits, at 31,000 plants per acre into the stubble of a just-harvested wheat crop.

Double-crop corn was a risky venture, which for Smart meant additional emphasis on good management, a Bt hybrid with drought resistance, frequent irrigation and a fungicide application.

Other advantages to corn behind wheat are reduced costs and simplicity versus early corn, according to Smart. “When you plant corn in June, it’s growing so rapidly that you can use every unit of fertilizer. You plant it and it’s up in four days. It doesn’t ever quit growing.”

Smart also liked the low herbicide cost of the practice — one application of 2 quarts of atrazine and 30 ounces of Roundup, put out three days after planting.

A big key to getting good yields with the practice is a fungicide application to combat late-arriving disease. In 2007, wheat/corn plots totaling 18 acres with two fungicide applications yielded 185 to 195 bushels per acre, compared to a little under 150 bushels for the check.

Smart, who farms corn, rice and soybeans with his father, Felix Smart Sr., and brother, Jack, expanded the corn/wheat program to 300 acres in 2008.

But last season didn’t start out so ideally. Smart planted wheat/corn on June 20, compared to June 7 in 2007. “Wheat harvest ran late in 2008, but every crop was late.”

For the wheat/corn in 2008, Smart planted a Pioneer 31P42, which contained the Herculex, LibertyLink and Roundup Ready traits.

“We planted it, the corn emerged and we put out 100 units of nitrogen, 25 units of sulfur and 2 pounds of zinc. We tissue sampled and P and K levels were fine. But we think we were getting some fertility from corn stalks breaking down from the previous year’s corn stubble.”

Irrigation is a key to good yields for late-planted corn, noted Smart. He waters down every middle on wheat/corn rather than every other middle on early corn. “I’ve noticed it’s really helped,” Smart said.

Smart started irrigating corn early in 2008, but ended up scalding the crop. “That was the first time I had ever done that. The tops and the bottoms looked bad. The middles looked good. We irrigated all the way up to tassel. Then right at tassel, we got rained on. It went through pollination wet.”

Smart also had difficulty running water down the rows because of wheat stubble and noted, “I probably should have burned the wheat stubble.”

Smart’s wheat/corn continued to deal with stresses during the season including excessive heat and rain and high winds spun off from two hurricanes late in the season. “The winds didn’t break the corn over because it was still green, but it did get it leaning. Once the stalk dried, another wind could blow it over. We also had patches that blew down during the hurricane. We had 200 acres of early corn that was flattened, like a stubble roller went across it. It took us two weeks to get it harvested using pick-up bars.”

When southern rust started building in Smart’s corn, he made a fungicide application that stopped it cold. “In 2007, I noticed that good health late in the season made the corn. This year, I went with an application of (azoxystrobin) which controlled what rust was there and gave me a healthy corn plant. We left a strip off one end and it made a big difference in yield.”

Smart’s wheat/corn also attracted the attention of University of Arkansas Extension plant pathologists Scott Monfort and Michael Emerson. They conducted a fungicide study on wheat/corn to determine the value of using a fungicide on late-planted corn. Another study looked at 30 of the top hybrids planted in the Mid-South. “We’re evaluating them to see where we’re at on southern rust resistance,” Monfort said. “We had a few hybrids that showed some promise, but nothing that is going to show true resistance.”

The fungicide plots were harvested using an Ag Leader InSight grain monitoring system rather than the traditional weigh wagon. The monitor was donated by Heartland Technologies.

According to Emerson, in 2008, plots not treated with fungicides averaged 101 bushels per acre and treated plots averaged 133 bushels per acre. There were very little differences observed among commercially available fungicides.

The 32-bushel yield response observed in the fungicide trials was largely due to the favorable environment that late-planted corn (behind wheat) provided for southern corn leaf rust development and spread, Emerson said.

For the most part, corn planted before April 15 will not be as affected by southern rust; however, late-planted corn (especially double-crop corn) will be at higher risk for infection and will need to be protected by a fungicide, according to Emerson.

The study on the Smart farm also indicated that the best timing for a fungicide application on late corn is between 100 percent tassel and brown silk. “You want the fungicide to help you get through that pollination period,” Monfort said.

But researchers are still working on nailing down the exact timing. “This year (2008), brown silk was a little too late and 100 percent tassel was the best timing.

Smart harvested wheat/corn in mid-November almost a month later than his 2007 harvest. “We could have only been two weeks late, but the weather kept us out of the field.”

Wheat/corn yields were down considerably from the previous year, but so were yields in early-planted corn, soybeans and rice. Full-season corn averaged 150 bushels per acre, which was off about 40 bushels from 2007. “Our rice was off 10 bushels to 15 bushels. Wheat/corn yields came in around 100 bushels per acre.”

At the time of this writing, Smart was still trying to determine which double-crop system — wheat/corn or wheat/beans did better in 2008. But neither practice will be part of the crop mix this season because Smart decided to not plant wheat last fall. “Wheat is just a pain for us. It just throws a kink in our operation. We’re trying to irrigate rice, early beans and corn at the same time we’re trying to take wheat out of the field and worrying about planting behind it. The price is going to have to get up there for us to go back to it.”

Despite having no wheat this season, Smart, Emerson and Monfort plan to repeat their small plot fungicide study for late-planted corn. “I’ll still plant the corn in June, it just won’t be after wheat,” Smart said.

When wheat does come back into Smart’s crop mix, and he figures it will one day, he’ll be ready to jump back in with corn again. “If I planted 500 acres of wheat in 2010, I’d grow 250 acres of corn behind it,” Smart said. “I still think it would profit most years.”

e-mail: erobinson@farmpress.com