Institution of the Agricultural Research and Higher Education
Abstract
Nematode communities were monitored in 26 oases in Kebili under various agricultural systems.
Differences between studied oases consisted in tillage frequency, soil amendment type (manure or
manure+ mineral fertilizers), cover crops and field age. In addition, this study evaluated the importance
of the C-P (Colonizer-Persistent) triangle and the faunal profile (representation of enrichment index vs.
structure index) as a biological indicator and monitoring tools in support of soil quality assessment. The
results showed that nematode communities were composed by 10 bacterial feeders (Ba), 3 fungal feeders
(Fu), 12 plant parasites (PP), 4 omnivores (O), 1 predator (P) with the dominance of (Ba) and (PP) in all
surveyed oases. The nematode communities differed slightly depending on oases age. Bacterial feeders
and Discolaimium genus were found in both young and old ones. Plectus genus (Ba) was found only in
young oases while Xiphinema, Criconema and Trichodorus genera (PP) were absent in these oases. Few
nematode taxa were affected by soil amendment type and cover cropsincluding some bacterial and fungal
feeders. The highest taxa richness was recorded in bare soils and in field with tillage frequency of 2 or 3
years. The lower MI (Maturity index) value was recorded in old oases. Most of studied oases were
characterized either by a high soil disturbance level with a high abundance of cp-1 group (Bacterivore
nematodes with c-p value =1)as an indicator of a disturbed food web or by a stressed soil with high
abundance of cp-2 group (Bacterivore and fungivore nematodes with c-p value = 2) as an indicator of
degraded food web. Only few sites showed a maturing and structured food webs with respectively low
to moderate soil disturbance level and undisturbed soil. This study highlighted also that some nematode
genera may potentially serve as differential bio-indicators of soil disturbance