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High mineral levels jeopardize peanut crop

BROWNFIELD, Texas -- Irrigation water quality problems can cost peanut farmers thousand of pounds in yield and thousands of dollars in lost revenue.

Justin Tuggle, a crop consultant with Crop Docs and Research Consulting in Brownfield, says peanuts are extremely sensitive to water quality problems, especially boron, chloride, electric conductivity and sodium.

High levels of these minerals could result in peanut yield reduction to 1500 pounds or less per acre. That’s for farmers who typically make better than two tons per acre, he says.

Tuggle got interested in the problem in 1997, when he worked for DeLeon Peanut Company.

"We identified problems in Terry County during a peanut tour," he recalls. "We found that no data existed about the potential adverse reaction from high levels of these minerals and we had no recommendations of what to do about it."

He said folks had assumed that if certain mineral levels in water affected soybeans a certain way they could expect similar results in peanuts.

"We needed data specific to peanuts," Tuggle says.

The Peanut Foundation, Western Peanut Growers Association, Texas Peanut Producers Board, and The American Peanut Council funded a program to find answers. Tuggle says DeLeon Peanut Company technical staff conducted a study in 2002 to determine if in water quality problems could be overcome through irrigation and crop management.

He says results from a Texas Agricultural Extension Service study conducted from 1998 through 2002 in West Texas identified limits for chlorides at 450 parts per million (ppm), boron at 0.75 ppm, sodium at 450 ppm, and electrical conductivity at 2100 micromhos/cm.

Tuggle found significant effects at a 0.05 level on yield and grade, "depending on specific mineral present in the water and interaction between minerals.

He also found that managing irrigation can offset losses especially with toxic levels of boron, chloride, and electrical. Sodium toxicities were not found in the study. "Interaction of chloride and electrical conductivity was not manageable," Tuggle says. "Boron effect on peanut grade was manageable, but other toxicities had negative effects on grade."

The key, Tuggle says is to test irrigation water, identify mineral levels and then manage accordingly.

"Water quality indicators showing boron, chloride, and electrical conductivity above threshold may be managed to achieve yields of 4,000 pounds per acre," Tuggle says. He says growers cannot expect these yields, however, with conflicting problems such as herbicide damage, disease, or other physiologic stresses.

"Growers need a minimum of 4.5 gallons of irrigation water per minute per acre to manage water quality problems successfully."

Peanut producers need a 48-inch soil probe to measure soil moisture profile weekly from plant emergence to harvest. Growers should pull water samples from an irrigation system prior to planting and deliver those samples immediately to a credible lab for analysis. Farmers should allow wells to be active for one hour before taking samples.

Management practices include:

1. Determine water quality levels.

2. Boron above 1.2 ppm should not be considered for peanut irrigation.

3. Chloride above 550 ppm should not be considered.

4. Sodium above 450 ppm should not be considered.

5. Electrical conductivity above 2,700 micromhos/cm should not be considered.

6. The soil moisture profile should be 48 inches prior to planting.

7. Proper plant populations are necessary to sustain potential yield.

8. Soil moisture profile should be monitored weekly by probing the soil in front of irrigation. A full profile of 48 inches should be maintained by adjusting weekly irrigation volume.

9. If the soil profile becomes difficult to penetrate increasing irrigation volume from 0.25 to 0.5 may be necessary to saturate the profile.

10. Nodulation should be assessed to determine if nitrogen is necessary for proper crop development.

11. Irrigate late in the season to maintain a full soil moisture profile until two weeks prior to digging.

12. If at any point during the late season the peanut canopy begins to deteriorate consider digging before peg attachment weakens or is lost.

13. Peanuts should be harvested at proper moisture with weak peg attachments on physiologically stressed plants.

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