Two Semi-automatic Elutriators for Extracting Nematodes and Certain Fungi from Soil

Abstract

Two efficient, senti-automatic elutriators for assaying soil samples for nematodes are described. The first apparatus is a four-unit elutriator which combines conventional extraction methods with the following major features: atttomatic mixing of 500- to 1,500-cm³ soil samples with water (± air); "turbinate" sample splitters from which fractions of 1/15 or greater are passed onto 26- or 38-[mu]m sieves for collection of larvae and adult nematodes; the capacity for collecting roots, intact egg ntasses, and cysts on 250-425-[mu]m sieves; and a variable speed motorized sieve-shaker. Nematodes, after being collected on 38-[mu]m sieves, are separated from debris by centrifugation or by Baermann trays. Secondary features include: air cylinders, solenoid valves, and time clock for atttomatic dumpittg residual soil and water; relay-controlled coarse spray nozzles activated for 5 sec every 30 sec for washing nematodes through 250-425-[mu]m sieves; adjustable rates of water amt air flow, and tinting. The second type of elutriator operates on similar principles but costs less to construct. It requires somewhat more operator participation; sieve spraying is carried out by the operator, anti elutriators are dumped manually. Both elutriators also show promise for monitoring populations of certain other soil microorganisms. Key Words: population dynamics, techniques.