Vertisols are characterized by their high clay content, which can hinder assessment of their soil biology. Recovery of nematodes from vertisols with active techniques has indicated that free living nematode numbers within Australian vertisols are often low. Despite this, cotton yield losses due to the reniform nematode have recently been reported in Australia. In light of this and other changes in the cotton production system, we undertook a series of experiments to determine whether passive nematode extraction techniques could be applied to high clay vertisols. Existing published passive nematode recovery methods proved to be inefficient. The use of sodium hexametaphosphate as a clay dispersant was found to further reduce effectiveness. Instead, direct extraction of soil in Ludox at 1.1 g/cm3 followed by sieving was found to be as effective at recovering nematodes using Baermann funnel extraction from fresh soil but considerably quicker and three times more effective with dried soil.
- Colloidal silica