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The effects of soil conditions on nematode populations were investigated in a field study at the Avdat Research Farm, Israel. Soil samples from the upper soil layer (0-10 cm) were collected monthly during November 1997 and October 1998, under the canopy of three halophyte shrubs: Zygophyllum dumousum, Hammadetum scopariae and Reaumuria negevensis. Ecological indices such as fungivore to bacterivore ratio (F/B), ratio of fungivores and bacterivores to plant parasites (WI) trophic diversity (TD) and Shannon index (H’) were used to assess and compare the response of nematode populations to the soil conditions. The mean numbers of total nematodes during January 1998-April 1998 were less under Z. dumosum than under H. scoparia, and those of total nematodes during Apr il 1998-October 1998 were higher under R. negevensis than under the control soil. Bacterivores under the three shrubs were the most abundant trophic group. Significant differences were found between months and between treatments for total nematodes, bacterivores and plant parasites. The content of K+ exhibited a positive correlation with total nematodes, bacterivores, plant parasites and omnivores-predators, and that of Ca2+ presented a negative correlation with bacterivores. F/B, WI, TD, and H’ were effective in distinguishing differences in nematode populations during the study period.