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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Date palms rooting study
In absence of a mechanical probe for sampling
and a study of tree root depth (R.d.) like
that of field cultures (Hansson 1987), we used
a method of measurement based on a progressive
survey of Deglet Noor date palm rooting
since 85% of the root are distributed in
the zone of 2 m deep and 2 m on both lateral
sides (Munier 1973; Zaid 2002). We used a
manual drill of 150 cm depth and a scale.
This method consisted in measuring rooting
up to 120 cm of depth, at 80 cm far from the
trunk, with a gradual survey up to 150 cm of
depth to confirm an absence of roots beyond
120 cm. For each farm, we carried out three
random measurements of rooting on adult
date palms in full production to calculate average
maximum depth of rooting. Root depths
were classified in four groups; 0-40 cm, 40-
80 cm, 80-120 cm and higher than 120 cm of
depth.
Statistical analysis
Groups of depth range for roots and water
tables were chosen for practical reasons.
Several grouping of observations for the 167
farms were formed according the tested hypotheses.
The hypotheses were that low water
table or crusts depth alone or in combination
limit root growth. Means and standard deviations
for subgroups of palm areas are shown
in Table 1. Preliminary results of regression
analyse obtained for the whole group or by
group of palm areas which gave a higher
number of outliers and lower determination
coefficients are not shown. Means, standard
deviations, regression analyse and determination
coefficient (R 2 ) were performed with
Excel 2004 software.
Results
The synthetic results (Table 1) showed that
the hydro-edaphic environment in the Ouargla
basin was degraded. The groundwater
levels had serious effects on rooting of date
palms and physico-chemical soils degradation
by waterlogging, gypseous crusts formation
and soils’ salinization.
Hydro-edaphic study
In this study, 53.9% of the palm plantations
showed a shallow water table, lowers than
1.2 m of depth, varying from 29 to 119.4 cm
(Figure 2). According to the USSL classification
(1954), modified by Durand (1958), salinity
degree of groundwater varied between
Table 1 – Synthetic results showing means with standard deviations in the date palm areas of Ouargla Basin.
Area types Date palm farms W.t.d. E.C. w.t. E.C. e1:5 E.C. i.w. G.c.d. R.d.
areas numbers (cm) (dS.m-1 ) (dS.m-1 ) (dS.m-1 ) (cm) (cm)
Deep water tables Bamendil 3 > 120 - 4.0 ± 0.7 2.20 ± 0.06 65 ± 27 65 ± 26
with gypseous crusts Beni Thour 1 > 120 - 5.8 ± 0 4 ± 0 73 ± 0 72 ± 0
Ksar 1 > 120 - 4.7 ± 0 4 ± 0 111 ± 0 114 ± 0
Total 5 > 120 - 4.5 ± 0.9 2.8 ± 0.9 76 ± 28 76 ± 28
Deep water tables Bamendil 15 > 120 - 2 ± 1 2.2 ± 0.1 - > 120
without gypseous crusts Beni Thour 3 > 120 - 3 ± 1 3.63 ± 0.08 - > 120
Ksar 8 > 120 - 2.8 ± 0.6 2.0 ± 0.2 - > 120
Mekhadma 18 > 120 - 3.1 ± 0.6 2.6 ± 0.6 - > 120
Said Otba 28 > 120 - 2.4 ± 0.7 4 ± 1 - > 120
Total 72 > 120 - 2.6 ± 0.8 3 ± 1 - > 120
Shallow water tables Bamendil 11 65 ± 27 15 ± 4 4.87 ± 1.83 2.4 ± 0.7 69 ± 17 70 ± 28
with gypseous crusts Beni Thour 1 97 ± 0 18 ± 0 2.92 ± 0 2.3 ± 0 80 ± 0 101 ± 0
Ksar 3 83 ± 25 23 ± 9 5.11 ± 0.8 4 ± 1 81 ± 31 86 ± 23
Mekhadma 3 61 ± 48 16 ± 4 5.58 ± 2.3 2.7 ± 0.8 62± 47 63 ± 45
Total 18 69 ± 30 17 ± 5 5 ± 2 2.7 ± 0.9 70 ± 24 73 ± 30
Shallow water tables Bamendil 15 66 ± 36 18 ± 6 6 ± 2 3 ± 1 - 67 ± 31
without gypseous crusts Beni Thour 11 68 ± 33 21 ± 8 6 ± 1 3 ± 1 - 79 ± 34
Ksar 13 61 ± 29 21 ± 7 6 ± 1 3 ± 1 - 68 ± 27
Mekhadma 27 65 ± 30 23 ± 8 6 ± 2 3 ± 1 - 78 ± 32
Said Otba 6 77 ± 27 21 ± 7 5.7 ± 0.9 3.3 ± 0.7 - 87 ± 29
Total 72 66 ± 31 21 ± 7 6 ± 1 3 ± 1 - 74 ± 31
ecologia mediterranea – Vol. 35 – 2009