Heavy Metal Soil Testing for Hemp

— Written By

Hemp in handWEDNESDAY, MARCH 6, 2019

CONTACT: Dr. David Hardy, Ph.D.,
N.C. Department of Agriculture & Consumer Services, Agronomic Services Division

NCDA&CS heavy metal testing not designed for hemp production.

RALEIGH — Hemp is a relatively new crop to North Carolina that is attracting a lot of attention from growers looking for viable crops that may have profit potential. Some hemp company contracts are requesting soil testing for heavy metals of fields where hemp may be produced, which has led to a number of questions about testing coming into the N.C. Department of Agriculture and Consumer Services, Agronomic Services Division.

“The division’s Soil Testing Section is not accepting or analyzing soils for heavy metals for this requirement,” said Dr. David Hardy, soil testing section chief. “Growers who need soil testing for heavy metals should seek private labs and check with hemp company representatives to determine the specific method of soil testing for heavy metals to be used.”

The heavy metal soil testing that is offered by the Soil Testing Section is specifically approved for sites that are permitted for the land application of septage through the N.C. Department of Environmental Quality, Hardy said. Additionally, some waste products that may contain heavy metals, such as tobacco dust from processing plants, are permitted for land application by the state per their policy for beneficial reuse of solid waste. These state-regulated sites are the only sites where soils are analyzed for heavy metals by the Soil Testing Section.

The Soil Testing Service’s soil testing methods are designed and used to estimate the soil fertility requirements for crop growth, not to assess the risk of potential plant uptake or accumulation of a heavy metal, Hardy said. The soil test extractant is designed specifically for nutrient evaluation related to plant growth where a stronger, more acidic total metal testing method is typically used for most heavy metal evaluation of soil. Regardless of the method used for heavy metal testing, interpretation of lab results is critical for evaluation and our soil testing service does not know what limits processors may have for hemp.