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Agronomic Services — News Release


Contact: J. Kent Messick, field services chief
NCDA&CS Agronomic Division
(919) 733-2655

Irrigation water with low pH can harm plants

Frankie Jones of Willow Oak Nursery and regional agronomist Dianne Farrer worked together to solve a nutrient and media pH problem.
Frankie Jones of Willow Oak Nursery and regional agronomist Dianne Farrer worked together to solve a nutrient and media pH problem.

HOOKERTON—Last May, plants were dying at Willow Oak Nursery in Greene County. Manager Frankie Jones suspected that unseasonably warm weather had stimulated his slow-release fertilizer to react too quickly. However, tests recommended by Dianne Farrer, a regional agronomist with the N.C. Department of Agriculture and Consumer Services, soon identified a very different problem. Jones' well water, which he uses for irrigation, is abnormally acidic with a pH of 3.0.

Water with low pH is problematic for several reasons. It can interfere with plant root growth by making the potting material too acidic. It can increase or decrease the solubility and availability of micronutrients. It can also cause minerals like iron to precipitate out and clog irrigation equipment. In Jones' case, it may even have contributed to a rapid breakdown of his "slow-release" fertilizer.

"Acidic well water is a relatively sporadic problem in eastern North Carolina," Farrer said. "A single property may have several wells and only one be affected. There is no standard or uniquely cost-effective treatment. Each situation is different."

Farrer and Jones decided to address the water quality problem by raising the pH of the potting material. Dr. Ted Bilderback, a nursery crops extension specialist and professor at N.C. State University, made suggestions about how much additional lime would be appropriate to mix in. Jones then made a special request to his potting material supplier for the change in formulation.

When the new mix arrived, Farrer performed a test known in the nursery industry as "pour-through." Pots containing planting media are irrigated. The water that drains from the bottom of a pot is collected and sent to the NCDA&CS Agronomic Division for solution analysis. Based on the test results, which are available within a few days, growers get a good idea of how suitable the potting material is for growing plants. The report provides an accurate measure of important parameters such as pH, soluble salts and nutrient levels.

Farrer tested the new media upon delivery to the nursery and again at intervals over several weeks. Based on those results, she advised Jones to let the newly limed media sit for at least a couple of weeks before potting plants. This waiting period provides the time necessary for lime to react, which results in a more beneficial environment for plants.

Jones continues to monitor the pH situation regularly. "I collect pour-through samples from all new batches of media," Jones said, "and from newly potted plants once a month. In the spring, I'll submit another well-water sample. Dianne has really helped me handle this problem and turn it around. She's shown me what kind of samples to collect, how to fill out the paperwork and how to use the results."

The NCDA&CS Field Services section has been helping N.C. growers manage fertilization and other nutrient-related issues for nearly 30 years. The division's 13 regional agronomists visit growers; evaluate suspected nutrient and/or nematode problems; and give advice on sampling, liming and fertilization. For the agronomist in your area, go to or call the Agronomic Division at (919) 733-2655.

Farrer provides advice on fertilization, nutrient management and nematode problems for growers in Craven, Carteret, Greene, Jones, Lenoir and Pitt counties. She can be reached by phone at (252) 830-1718 or by e-mail at


Last Update June 11, 2009


NCDA&CS Agronomic Services Division, Colleen M. Hudak-Wise, Ph.D., Director
Mailing Address: 1040 Mail Service Center, Raleigh NC 27699-1040
Physical Address: 4300 Reedy Creek Road, Raleigh NC 27607-6465
Phone: (919) 733-2655; FAX: (919) 733-2837

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