A study to determine the optimal sample size of sample for evaluation of nematode infestation was conducted in a field with one-month old sugarcane (H-32-8580) in its second ratoon stage. The soil was a sandy loam with slightly alkaline pH. Six different one hectare portions of the field were chosen for the study in each of which were collected 5, 10, 15, 20, 25, and 30 cores at depths of 0-30 cms and 30-60 cms. Each sample was homogenized and analyzed separately by a Baerman funnel technique. To obtain the relative optimal sample size it was assumed that a precise estimate of the nematode population could be obtained with 100 cores/ha for which sampling density the cost-benefit ratio was equal and corresponded to the maximal relative efficiency value (equal to 1.0). On the basis of these assumptions we calculated sampling efficiencies for densities varying from 5 to 100 cores/ha and determined that the relative optimal density was of 24 cores/ha in the 0-30 cms depth.
