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and infiltration rates (Mhango, 2000). However, in Zambia this mixture resulted
in poor seedling performance (Sileshi
et al.
, 2007), probably because the sawdust
had immobilized the nutrients in the soil, leading to nutrient stress. In the same
study, forest soil sterilized with heat and a mixture of unsterilized forest soil was
compared with sawdust and unsterilized forest soil. Height growth, root length,
number of leaves and shoot dry weight of seedlings were greater in unsterilized
forest soil than in sterilized forest soil or forest soil mixed with sawdust (Table
19.2). On the other hand, growth in stem diameter, number of primary roots and
root dry weight were less in unsterilized forest soil. This suggests that there is a
need for further research on appropriate soil media for different species.
There is evidence that early growth and survival of certain indigenous fruit
trees are negatively affected when they are grown without inoculation with
associated microsymbionts such as mycorrhizas (Ramachela, 2001). To achieve
the inoculation of seedlings with symbiotic microorganisms to form mycorrhizas,
forest soil from mature stands of the fruit tree species is often used in the potting
mixture. In addition, although most priority miombo indigenous fruit trees do not
belong to the family Leguminosae (Maghembe, 1995), which is highly associated
with nitrogen-fixing rhizobia, they may benefit from the associated group of
bacteria which are free-living and are found in the vicinity of grasses, and the
free-living group of bacteria which is present and active in easily available organic
Table 19.2.
Effect of potting mixture, foliar and soil applied fertilizer on the growth of
Uapaca
kirkiana
seedlings in the nursery at Msekera.
Root
Shoot
Foliar
Stem
Root
Primary
dry
dry
disease
Factor and
Height
Leaf
diameter
length
roots
weight
weight
incidence
level
(cm)
number
(mm)
(mm)
(number)
(g)
(g)
(proportion)
Potting mixture
UFS
12.3
a
7.9
a
3.4
b
27.5
a
18.3
b
2.8
b
4.1
a
0.85
FS + SD
10.9
b
6.7
b
4.4
a
20.8
b
8.3
c
9.7
a
2.8
a
0.73
SFS
10.8
b
7.6
ab
4.3
a
28.5
a
23.8
a
10.0
a
3.4
a
0.87
P value
0.008
0.009
0.001
0.0001
0.0001
0.0001
0.072
0.029
Soil fertilizer
(D-compound)
Without
10.9
b
7.5
a
4.3
a
27.7
a
20.4
a
7.6
a
3.8
a
0.79
With
12.1
a
7.5
a
3.6
b
24.8
b
15.1
b
6.2
a
3.3
a
0.85
P
value
0.025
0.635
0.002
0.001
0.0001
0.439
0.610
0.290
Foliar fertilizer
Without
10.6
b
7.2
a
3.6
a
25.5
a
18.4
a
5.7
a
2.4
b
0.83
With
12.2
a
7.7
a
4.2
a
26.9
a
17.2
b
8.0
a
4.5
a
0.80
P
value
0.027
0.493
0.153
0.743
0.033
0.120
0.001
0.136
UFS, unsterilized forest soil; FS + SD, mixture of forest soil and sawdust; SFS, sterilized
forest soil.
Treatments followed by the same letter are not significantly different at the 5% probability
level according to the
t
test (LSD).
Source: Sileshi
et al
. (2007).
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