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Agronomic testing advised for flooded fields

Soil erosion and flooding from Hurricane Matthew may have caused changes in soil fertility, and the N.C. Department of Agriculture and Consumer Services advises farmers to account for this as they make plans for the next growing season. The department’s Agronomic Services Division can help answer questions about what was affected and how to manage it.

“Many farmers were not expecting Hurricane Matthew to have this kind of impact, and now that fields have drained and dried over the past two months, it is an excellent time to soil sample to evaluate lime and nutrient needs, especially where water was standing for several days,” said Agriculture Commissioner Steve Troxler.

In addition, flooding most likely moved harmful nematodes. Floodwater carries top soil with it, and if the soil is infested, the nematodes may be moved to areas that weren’t infested. “Anything that moves soil also moves nematodes,” Troxler said.

Dr. David Hardy, chief of the Soil Testing Section in the Agronomic Services Division, advises growers to consider several factors before sampling soil:

Wait for fields to dry out well enough to acquire good samples. Drying should have occurred in most areas where flooding happened.

Where soil movement occurred, grade and reshape those areas. Consider sampling them separately to evaluate fertility if they are large compared with other sampling zones.

Focus on soil types in relation to sampling. Leaching of nutrients such as potassium, sulfur and, to a lesser extent, magnesium occurs more readily in sandy soils with low organic matter.

Near the coast or around brackish waters, salt water intrusion or overwash may have increased sodium levels of soils significantly. Soil sampling will evaluate the need for gypsum to displace sodium from the soil and also for lime if pH is low.

Testing of agricultural water may also be necessary, said Dr. Kristin Hicks, chief of the Plant/Waste/Solution/Media Analysis Section. She advises growers to consider these factors:

Irrigation ponds and wells in coastal areas where flooding occurred should be tested to determine if sodium and chloride have affected water quality and if water pH is suitable for irrigation.

Fish ponds may have been exposed to nitrates and phosphorus from overwash, both of which can trigger algal blooms and fish die-offs if the levels are high enough. Water pH in the neutral range is also essential for fish health. Ponds that may have been acidified by flooding from brackish water should be tested. Pond water pH can be corrected by liming, but the need for lime should be determined by starting with a solution test.

Water sources, both pond and well, that are used for livestock drinking water should be checked for elevated iron, low pH or other mineral components that may affect suitability for animals.

Please note, the Agronomic Services Division does not analyze for any microbial pathogens. Analysis is for chemical parameters that can affect crop and animal health.

There are fees for solution analyses. There also is a fee for soil tests between Dec. 1 and March 31. For more information about testing services and fees, go to

NCDA&CS Public Affairs Division, Andrea Ashby, Director
Mailing Address:1001 Mail Service Center, Raleigh NC 27699-1001
Physical Address: 2 West Edenton Street, Raleigh NC 27601
Phone: (919) 707-3001; FAX: (919) 733-5047

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