IMPROVEMENTS TO THE HEPTANE FLOTATION METHOD FOR COLLECTING MICROARTHROPODS FROM SILT LOAM SOIL

Microarthropods can be extracted from soil using the heptane flotation method. To determine the most efficient use of this method for silt loam soil, field-moist samples weighing 25, 50 or 100 g were treated with four variants of the method described. The variants differ with respect to magnetic-stirrer size and using or omitting the procedure of rinsing the beaker wall and sieve with alcohol. After each flotation cycle, the number of mites and springtails extracted was determined. The number of flotation cycles needed to extract > 95% of the microarthropods in a sample: (1) was not affected by stirrer size, except for the samples of 100 g (smaller stirrer size is less efficient); (2) increased with sample weight from three cycles for 25 g samples to six for 100 g samples; and (3) was not affected by omitting the rinsing procedure. There was no effect of sample size on the total number of microarthropods extracted per unit weight. It is concluded that flotation of 25 g field-moist soil samples in three cycles without the rinsing procedure is the most efficient variant. It takes about half the time to extract 25 g samples to > 95%, compared with 100 g samples.