Researchers study ratoon crop, planting dates for grain sorghum

Frances Gould, LaBauve, Randy, Benedict, Linda F.  |  11/14/2013 11:21:33 PM

LSU AgCenter researchers are exploring the potential of a ratoon – or second – crop of grain sorghum in Louisiana.

Sorghum ratooning is practiced near the Texas Gulf Coast, but interest has increased in Louisiana.

"Research in Texas has shown that some hybrids do better than others in ratoon cropping systems," said LSU AgCenter agronomist Rick Mascagni.

LSU AgCenter researchers are gathering information on hybrids and nitrogen management to determine if ratoon cropping is adaptable to the current production system and if it’s economically feasible.

It’s important to get the first crop harvested as soon as possible and then get the ratoon crop initiated quickly, Mascagni said. The initial crop is harvested, then the stalks are clipped and fertilized for the second crop.

"We’ll hopefully be able to determine whether or not a ratoon cropping system in Louisiana will be cost-effective," said Mascagni. Results may vary between the northern and southern regions of the state, he added.

In conjunction with variety trials, large-scale farm demonstration plots are located in the three major grain sorghum-growing regions – alluvial portions of Rapides, Tensas and Bossier parishes.

These demonstrations allow research and extension specialists to work with county agents and growers to verify high-yielding hybrids from the trials on a field scale.

"The variety trials and field-scale demonstrations are the most important tools to aid producers in grain sorghum hybrid selection," said LSU AgCenter agronomist Josh Lofton.

Early-season stand establishment is one of the most critical aspects of grain sorghum production, Lofton said. "Re-emphasizing optimum planting dates and yield losses associated with delayed planting are critical for growers."

The recommended planting dates are between April 1 and May 1 for south Louisiana and between April 15 and May 15 for north Louisiana.

"We’re looking at different planting dates ranging between two weeks before or a month after optimum planting dates," said Lofton. "When you plant in the optimum window, you may get good production, but the yield reduction associated with late planting needs to be continually evaluated."

Researchers are also looking at the most effective chemicals to use in controlling insects on sorghum.

Headworms – particularly the corn earworm and the sorghum webworm – have developed resistance to pyrethroid applications. "We’re looking at alternative insecticides that might work better," said LSU AgCenter entomologist David Kerns.

LSU AgCenter entomologists continue to study the effects that seed treatments have on fire ant predation of germinating sorghum seed. Insecticides like Nipsit, Poncho, Gaucho and Cruiser are proving highly effective, Kerns said.

Another pest that can present problems with late-planted crops is the sorghum midge. Pyrethroids tend to be effective against them, but the sorghum heads continually bloom over a number of days, exposing new sections to midge larvae damage.

"The way it flowers makes it difficult to protect," said Kerns of grain sorghum. "We’re looking at data on new chemicals that provide better residuals, offering longer protection for the overall growth of the bloom."

Last year, 115,000 acres were planted in grain sorghum in Louisiana. The crop grossed almost $75 million.

Randy LaBauve

(This article was published in the 2013 Louisiana Soybean & Grain Research & Promotion Board Report.)

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