Environmental Engineering Reference
In-Depth Information
Land-use stage versus soil micro-organisms and fauna
30 cm) were sampled from random points about
five metres apart for three land-use stages, namely native forest (sacred grove),
proka
-managed agroforest, and slash-and-burn annual cropping fields.
Taxonomic units of soil fauna were ants, arachnids (spiders), gastropods
(snails), and
Glyllidae
(crickets). Far fewer soil fauna were found in the slash-and-
burn soil than the
proka
and sacred grove. The most numerous soil fauna identi-
fied were ants. These occurred in all the three monoliths under the three land-use
stages.
Over 73 per cent of the ant units were identified in
proka
, 15 per cent in the slash-
and-burn annual cropping, and 11 per cent in the sacred grove. Only a single spider
was found. It occurred under the grove. Similarly, the three snails and the two earth-
worms encountered were identified in only the
proka
soil, while the only three
crickets that were found occurred in the grove. The most numerous colonies of fungi
(33
Soil monoliths (25
25
10
6
) and bacteria (36
10
6
) occurred in the
proka
, followed by the slash-
and-burn soil (30
10
6
).
The
proka
-managed agroforest was thus superior in maintaining higher diversity
of soil micro-organisms.
10
6
and 21
10
6
) and sacred grove (9
10
6
and 2
Soil physical properties versus land-use stages at Tano-Odumasi
The physical properties under the various land-use stages were assessed by
measuring bulk density and total porosity. Bulk density (Table 11.2) in all
the land-use stages was lower in the topsoil (0-15 cm) than in the subsoil
(15-30 cm). Consequently total porosity was higher in the topsoil. This is
mainly due to the higher organic matter (Table 11.3) recorded in the topsoil.
A comparison of the values for the slash-and-burn and
proka
annual cropping
systems indicated a lower bulk density and higher total porosity for the latter
management system. In all cases, the sacred grove had the least bulk density
and the highest total porosity. When averaged over the 30 cm depth, the bulk
density ranked in an increasing order of slash-and-burn
agroforest
proka
annual cropping
sacred grove with their respective values of 1.47, 1.39,
1.33, and 1.20 g/cm
3
. The converse, sacred grove
proka
annual cropping
agroforest
slash-and-burn was true for total porosity with their respective
values being 54.72, 50.08, 47.45, and 44.34 per cent. The implications for
these values are that those land-use stages with lower bulk densities and
higher total porosities have the greater potential to enhance moisture conser-
vation through increased infiltration and low runoff rates. This, together with
the mulch cover, would be more potentially effective in controlling soil erosion
by water.
