CORVALLIS - A new soil test developed at Oregon State University may save thousands of dollars for Oregon hop growers by helping them avoid planting new acreage on contaminated soils.
The test is designed to detect the presence of heptachlor and chlordane pesticide residues in the soil. The residues are toxic to some varieties of hop plants, according to Jennifer Field, an assistant professor in the OSU Department of Agricultural Chemistry and a researcher with OSU's Agriculture Experiment Station.
Production from new hop plantings on soils containing heptachlor and chlordane residues is so low as to be barely worth harvesting. The test is intended to help growers avoid the expense of planting new acreage that is likely to fail because of soil contamination.
Field began developing the test two years ago in response to requests from Oregon hop growers. Her research was sponsored by the Oregon Hop Research Council.
Heptachlor pesticides were used for wireworm and flea beetle control in potatoes and root weevil in strawberries in the mid- to late 1950s.
"Heptachlor was one of the chlorinated pesticides," said Field. "The chlorinated pesticide group, which includes DDT, was extremely effective, but these products were found to have toxic effects in the environment that extended far beyond controlling insect pests."
Along with several other chlorinated pesticides, heptachlor was banned in 1972, but residues of this chemical have remained stable in the soil over several years. Chlordane was introduced as a substitute for heptachlor, but eventually chlordane was banned also, Field added.
Today, hop growers in the mid-Willamette Valley are expanding acreage into areas where potatoes and strawberries were once grown.
"The new acreage is being established to produce new varieties of hops," said Bruce Davidson, a hop grower near Keizer.
The heptachlor and chlordane pesticide residues in the soils of some of these new hop fields have become a costly problem because the standard soil test usually used by growers does not consistently detect the presence of heptachlor and chlordane.
"Unaware of the presence of residues, growers have put in new hop acreage on soils with pesticides residues that are toxic to hop plants," said Field. "When you consider that planting costs, including the hop trellis consisting of hundreds of wooden poles and thousands of feet of heavy wire, can reach up to $5,000 per acre, growers are left to absorb staggering losses when new crop acreage fails."
Hop growers in the Willamette Valley are aware of the situation and are careful about choosing sites for new hop yards, but problems still arise.
Davidson established new acreage on land near his home farm and was surprised to find a portion of the new hop yard growing well and the other portion stunted due to chlordane residues in the soil.
"I've lived in the Keizer area for years and felt I knew the planting history of many of these fields pretty well," said Davidson. "Even so, it's hard to be 100 percent sure about any field's crop history when you go back 30 or 40 years."
"Since farm land often changes ownership over long periods of time, complete records on the cropping history of a particular field are usually not available," said Field. "Fortunately, the development of a soil test that can detect heptachlor and chlordane pesticide residues in the soil will give hop growers a tool that will help them avoid this problem when planting new acreage."