Sodium-containing detergents enhance the extraction of nematodes.

The extraction of nematodes from clay soil is difficult using flotation-sieving methods of soil-water suspensions. Aggregated soil particles trap nematodes and prevent them from passing through the top coarse sieves during decanting. Also, the soil aggregates clog the sieves which slows the decanting operation. In addition, clay particles are difficult to clean from centrifuge tubes that are used in the centrifugal-flotation extraction process (4). Soaking, stirring and agitating soil in water have been used to aid in extraction (2, 3, 5, 6), but these manipulations, although reasonably effective, are time-consuming and do not solve the problem of cleaning the clay residue from centrifuge tubes. The replacement of exchangeable calcium with sod ium on soil par t i c les causes deflocculation (dispersal) of the soil (7). The use o f Calgon®, a commercial detergent containing sodium metaphosphate and sodium carbonate, to disperse soil samples for particle size analysis has recently replaced the use of sodium hexametaphosphate or sodium silicate which were previously used for this purpose. Seinhorst (5) used sodium oxalate to aid dispersal of clay soil during elutriation. Wallace (8) suggested using Calgon to aid in the recovery of cysts of Heterodera spp. from the soil. Many soils of middle Georgia are high in clay content and are difficult to process for n e m a t o d e assays. Soaking is required to disperse these soils so that they can be washed through a 9-mesh (1.98 mm openings) screen. A particularly difficult soil to process is the