Vol. 35 – 2009 - Ecologia Mediterranea - Université d'Avignon et des ...

MUSTAPHA DADDI BOUHOUN, LOUHICHI BRINIS, MOHAMED LAKHDAR SAKER, MARC COTE, JACQUES RABIER
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hydro-édaphique sur l’enracinement du palmier
dattier Déglet Nour dans les périmètres phœnicicoles
de la cuvette d’Ouargla.
Les résultats obtenus montrent que 53,9 % des
exploitations phoenicicoles présentent une
nappe phréatique ayant une profondeur comprise
entre 29 et 119,4 cm. L’étude de l’enracinement
du palmier dattier, à 80 cm du tronc, a
montré que 56,9 % des palmeraies présentent
un enracinement compris entre 27 et 119 cm de
profondeur, dont 3 % à cause des croûtes gypseuses
et gypso-calcaires, 10,8 % à cause de la
nappe et des croûtes gypseuses et gypso-calcaires
et enfin 43,1 % à cause de la nappe
phréatique. La conductivité électrique des eaux
phréatiques varie de 10 à 39,7 dS.m-1 .
L’étude des corrélations montre que la faible
profondeur de la nappe phréatique ainsi que
des croûtes gypseuses et calcaires diminuent la
profondeur d’enracinement. Les racines fuient
la zone de saturation en eau et la résistance
mécanique des croûtes pour se développer dans
le sens latéral. La salinité des eaux phréatiques
présente moins d’effet sur l’enracinement du
palmier dattier comparée au niveau de la nappe
phréatique.
Introduction
Excess water in soils is a global environment
problem and contribute to the degradation of
595 millions km 2 of soil, corresponding to
approximately 5% of non-productive grounds.
Soil clogging is caused by bad water irrigation
management, nature of soil and, water
table rise (Robert & Cheverry 1996).
Rise of subsoil water, produced by bad drainage,
causes edaphic degradation of agricultural
ecosystems and shortening of crop root
depths (Hatton & Nulsen 1999). Lowering
water table depths trigger harmful consequences
in the sub-Saharan (Bertrand et al.
1993) and Saharan environment (Durand
1958).
The phreatic groundwater table is close to the
soil surface in some Algerian south-east areas,
like Oued Righ and Ouargla; it varies from 0
to 1.2 m depth (Dubost et al. 1983; Dubost
1991; Saker 2000; Hamdi Aïssa 2001).
Problem of groundwater rise in the Ouargla
basin developed over the last few years as a
result of the anarchic multiplication of
drillings, bad drainage of agricultural water
and bad management of worn water. According
to Côte (1998), after the XXth century
drillings made it possible to double the planted
surfaces; but waste waters contributed to
the groundwater rise, in parts of the basin. The
drainage remains partly ineffective caused by
absence of discharge system.
Surface ground water, in hyper-arid climate
supports capillary increase of soluble salts and
accumulation of gypsum in the water table
(Durand 1958; Halitim 1988). This situation
causes harmful root asphyxiation and limits
crop rooting at the Saharan oasis level (Dutil
1971; Bahri 1987). This malfunction of the
date palm crop heritage leads to drop in date
yields quality.
Deglet Noor dates, produced on South-East
Algerian palm (Phoenix dactylifera L.) plantations,
are very sensitive to the bayoud
disease but until now, they have been leaved
unscathed. That seems to be related to different
parameters such as salinity (Amir et al.
1996). However, particular nature of salted
soils of these palm plantations also seems to
contribute to resistance (Laville & Lossois
1963; Kada et al. 1972).
Date palm grows badly in compact soils and
areas of bad drainage (Monciero 1961) which
presents harmful consequences on soil structure,
ventilation, biological activity, assimilation
of some mineral nutrients and consequently
date palm growth (Djerbi 1994).
According to Dutil (1971), rooting of the date
palm in soils of Ouargla is subjected to a
stressful environment caused by soil salinity,
bad groundwater drainage and gypseous or
calcareous encrusting. High root activity of
date palm favours concentration of soil solution
and precipitation of less soluble salts.
In the Maghreb, studies on tree rooting are
rare, especially for the date palm (Phoenix
dactylifera L.). Most of studies are American
and were carried out using pot cultures or on
soil profiles next to date palms; search were
related to root systems and impact of moisture
on rooting (Went and Darley 1953), water
table (Simmons 1926; Weeks 1957; Furr
1975; Dubost 1991) or irrigation and soil
(Armstrong & Furr 1959).
In this context, our study investigated the
impact of hydro-edaphic environment in the
Ouargla basin on root system of the Deglet
Noor date palm. Deglet Noor is a very widespread
cultivar in this area and it is of important
economic interest for Algeria.
ecologia mediterranea – Vol. 35 – 2009