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