Delta farmers face myriad of post-flood issues

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Published: June 5,2011

Tags: agriculture, flooding, floods, severe weather, Weather

MISSISSIPPI DELTA — Much of the flooded Delta was already planted for the 2011 season, and when it finally dries out, landowners will face challenges preparing it for planting.

Last Thursday, the Governor’s Office said total agriculture losses in Mississippi due to the flood could exceed $250 million.

Landowners of flooded acreage must manage a variety of issues, including oxygen-depleted soils, nutrient loss, soil compaction, debris removal and possible chemical contamination. Some acres may not be ready for planting again until next year.

Larry Oldham, soil specialist with the Mississippi State University Extension Service, said, “As the waters recede, a new landscape in both land and nutrient management will emerge. The soil chemistry that controls the bioavailability of most plant nutrients is very dynamic as soils transition from a normal state to flooded for several weeks, and then back to drier conditions.”

Oldham said conventional wisdom says soils are more fertile immediately after a flood, as upstream nutrients are deposited in downstream fields. But if this were true, the South Delta would not be as fertile as it is today since repeated flooding would have washed away nutrients.

Landowners must consider several things when preparing to plant again.

“Remember that flood water carries materials such as pesticides, petroleum products and other substances swept up in its downstream progress,” Oldham said.

Debris removal can include dead animals, uprooted trees and garbage.

While many will be tempted to work in the fields as soon as the water recedes, Oldham urged growers not to. Driving heavy equipment on wet soil compacts soil 10 to 20 inches below the surface.

Another management challenge is the expected phosphorus deficiencies.

“Among other factors, the deficiency problems came from the diminished activity of beneficial fungi that allow plants to take in phosphorus,” Oldham said.

Solutions to what is known as flooded soil syndrome may be to grow cover crops until planting next year if it is late in 2011 before fields can be worked. If corn is the desired crop in 2012, soil may require supplemental phosphorus fertilizer.

Wayne Ebelhar, Mississippi Agricultural and Forestry Experiment Station research professor at the Delta Research and Extension Center in Stoneville, said oxygen supply is a big issue in flooded land. Plants and organisms living in the soil need oxygen to survive.

“Soil aeration will be slow coming back to flooded land,” Ebelhar said. “Most of the flooded ground seals over with silt and clay particles, and it is slow to dry.”

In a normal wet-field situation, producers can till the soil to increase its oxygen capacity, but that is not possible in current super-saturated situations.

“We hit the flood stage in Greenville April 28 and the river kept rising. They’re predicting the river won’t drop back to flood stage until June 20,” Ebelhar said. “That’s almost eight weeks of flooding.”

Ebelhar said without oxygen for this length of time, it would take a long time for aerobic microbial populations in the soil and helpful insects and animals such as earthworms to repopulate the affected land.

“An earthworm may be pretty virile, but I’m not sure he can tread water for eight weeks,” he said.

Many living things suffocate from the lack of oxygen when the land and vegetation is covered by water for an extended time.

“Anaerobic organisms, or those that don’t require atmospheric oxygen to function, can increase and consume oxygen that is combined with such things as nitrate, resulting in subsequent nitrogen loss as a gas,” Ebelhar said. “Aerobic populations, or those that require atmospheric oxygen for life, will build back up with rapid reproduction once things dry out.”

The bottom line for many landowners in the flooded region is that the 2011 crop season simply won’t happen, and preparing for the 2012 season will require extra management.

“For a lot of producers, this flooded land may not have much cropping opportunity for this year,” Ebelhar said. “With this flood being so high, it’s going to take a long time for the water to drop and the ground to dry out. With the cost of seed, it’s an awful risky situation to plant in the middle of July or later.”

Source: MSU

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