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Salt water problems for Louisiana citrus

Since 1992, researchers and agents at the LSU AgCenter's Citrus Research Station near Port Sulphur have been working to minimize the intrusion of salt into the root zone of citrus trees.

Commercial citrus production in Louisiana is conducted primarily in extreme southeastern Louisiana, but the proximity of the growing areas to the coast means the intrusion of salt water also is an issue.

Wayne Bourgeois, resident coordinator at the LSU AgCenter's Citrus Research Station, says that while the problem of saltwater intrusion is an ongoing issue, it gets even worse during drought periods.

"The first symptoms came in the mid-'1990s with that drought," Bourgeois said. "The problem now is that there was little rain here this past January and February when other parts of the state got rain."

Bourgeois said the problems now are spread across much of Plaquemines Parish – the state's major citrus-producing area – and he estimated that as much as 30 percent to 40 percent of the trees that are showing symptoms may die over time.

Researchers say the salt invades the root zone of the trees and concentrates until a little moisture comes along and helps it be absorbed by the trees. That, in turn, leads the trees to drop leaves. "What we need is regular seasonal rains to wash the salt out of the root zone," Bourgeois said.

He said the research station is using a submersible sump pump to try to move some of the salt water away from the trees at the station, but that's not a foolproof method of solving the issue.

"Our problem is that we don't know whether the salt is coming from the marsh or from the Mississippi River," he said, adding, however, "We do know that when the river is low, it gets real salty."

Alan Vaughn, LSU AgCenter county agent for Plaquemines Parish, said that during rainy years, the salt washes down below the root zone of the trees. In drought years, however, the problems are further aggravated by the lack of freshwater wells for irrigation.

Vaughn said the area's $9 million citrus industry as a whole is OK, but the salt water is causing production to rise and fall for the individual producers.

"It takes several years after the salt washes down out of the root zone for the trees to get back to good health," Vaughn said, explaining it takes two years to get a good crop after the tree has experienced the salt problem.

"The salt water is reducing production by about 50 percent, because it causes good production one year and bad the next year," Vaughn said. "This cycle is not allowing the industry to grow. We just continue to go through these up and down cycles."

Vaughn said that a chloride level of 0.2 percent is known to be toxic to the trees, and that researchers are finding chloride levels as high as 1.6 percent in the parish.

So the experts say the outcome of this year's crop comes down to how much rainfall is received to possibly wash some of the salt away.

"It's still too early to tell," Bourgeois said. "Whatever fruit is left on the trees after the 'June drop' is normally what makes the crop."

Johnny Morgan is a writer for the LSU AgCenter.

e-mail: jmorgan@agcenter.lsu.edu

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