Plant mobilization of trace organochlorine residues in vegetable cropping systems

Soil testing has long been a part of Organic Certification. As part of the certification process, each grower must submit soil tests for lab analysis. The soil is subjected to chromatography tests to determine the extent of contamination by organochlorine insecticides. These compounds classify a wide range of noxious agricultural pesticides, many with half lives exceeding twenty years. Unfortunately for conventional and organic growers, even at hardly detectable levels these contaminants are finding their way into agricultural products. The Food and Drug Administration has established levels for taking legal action to remove contaminated products Organic standards are five and ten percent of federal limits respectively for Oregon Tilth and Oregon's organic statutes.

Rates of plant concentration of soil contaminants are not well known. Many crops are not included in the surveys. Much of the information is based upon recent applications of a contaminant, not trace residues. How reliable are currently accepted rates of uptake? Are there trends within a crop, or within a crop type or family? And are there any safe crops to grow on contaminated soils? Over a two year period, seventeen annual vegetable crops were grown in a four block experiment to determine pesticide uptake. Following are the procedures, results, and discussion of this on-farm experiment. Two years of soil contaminant level tests and nutrient tests from the experiment are included.