Researchers study 2nd crop, planting date for grain sorghum
By Randy LaBauve
BATON ROUGE, La. – LSU AgCenter researchers are conducting a number of important grain sorghum research projects to help maximize cost-effective returns for farmers.
One important project explores the potential of a ratoon – or second – crop of grain sorghum in Louisiana. The practice of growing a second crop from the remains of a first harvest is more common for sugarcane and rice in the state.
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.
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.
Variety trials that include ratoon crops are being conducted at the AgCenter Rice Research Station in Crowley, Dean Lee Research Station in Alexandria and Northeast Research Station in St. Joseph.
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 for yield, then the remaining stalks are clipped and fertilized for the second crop.
Last year’s ratoon crops were not harvested because plant development ended because of early frost.
“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.
Starter fertilizers have proven very effective for enhancing maturity in corn. “There’s very little research information on starter fertilizers in sorghum and how well they speed up plant maturity,” Mascagni said.
Starter fertilizer is being evaluated at zero and five gallons per acre applied at planting. Other research evaluates nitrogen management – comparing broadcasting urea versus dribbling nitrogen solution.
Additionally, researchers are determining optimum nitrogen rates on Sharkey clay and sandy loam soils.
In conjunction with the 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 maybe the most important tools to aid producers in grain sorghum hybrid selection,” said LSU AgCenter agronomist Josh Lofton.
Researchers at demonstration plots are looking into how grain sorghum production is affected by both planting dates and plant populations.
Early-season stand establishment is one of the most critical aspects of grain sorghum production, Lofton said. “Reemphasizing 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. But growers sometimes have to plant earlier or later because of management or environmental factors.
“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.”
Typically, higher seed populations – recommended at 75,000 seeds per acre – are used at optimal planting dates. But when larger populations are planted later, stress level may increase along with more plant competition.
“While these populations can potentially yield very high in optimum years, they lack the flexibility of the lower populations in adverse conditions,” Lofton said.
Previous research has shown a lower population can be more drought tolerant, with the potential to increase additional stems – or tillers – in optimum growing conditions. Higher populations tend to focus on main stem growth.
“Higher populations do not have as many heads, but the heads look and feel denser,” Lofton said.
“But tillers can contribute a fair amount to total yield of lower populations – if optimum conditions exist.”
Ultimately, depending on the inputs, this might offer a potential for cost savings, he said. Researchers are also looking at the most effective chemicals to minimize the impact of various insects on sorghum crops.
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.
AgCenter entomologists continue to study the effects that seed treatments have on fire ant predation of germinating sorghum seed. To date, 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.”
The research efforts are partially funded by the Louisiana Soybean and Grain Research and Promotion Board.
The first grain sorghum crops will be harvested in early August through late September. Last year, 115,000 acres were planted in grain sorghum in Louisiana. The crops grossed almost $75 million.