Chemistry Reference
In-Depth Information
term application of combined farmyard manure and fertiliser (FYM +F)
resulted in increased soil C concentration, providing food sources for
earthworms and mulching effect on their habitat and also stimulating plant
growth and litter return,
58
resulting in higher earthworm biomass.
d
n
1
r
2
n
g
|
4
5.2
Soil Macrofauna in Tropical Agroecosystems
In large parts of sub-Saharan Africa (SSA), pests, weeds, diseases and soil
fertility decline are major biophysical causes of low per capita food
production.
59
Degradation processes, such as loss of soil carbon and nutrient
depletion in general, can occur quickly and are difficult to reverse.
60
Moreover,
loss in yield cannot be corrected by the use of fertilisers in economies where
cash flow is minimal. Under such circumstances, Integrated Soil Fertility
Management (ISFM), i.e. integration of fertilisers with organic resources, has
been regarded as a feasible alternative in low-input systems, compensating for
the high costs of fertilisers.
52
Manipulation of the soil environment via tillage,
application of organic residues and manipulating soil fauna are among the
factors affecting SOM dynamics under cropping systems.
61,62
In low-input
agricultural systems, soil fauna have been found to play a crucial role in soil
organic matter dynamics, in soil physical properties improvement, and in
nutrient release for crop production.
63
However, soil macrofauna composition,
abundance and activity, and hence their impacts on soil processes, vary
depending on residue inputs and soil management practices.
25,64,65
Climate,
soil texture and management have been indicated to influence the activity of
soil macrofauna (e.g. earthworms and termites) that produce biogenic
structures.
66
It can therefore be postulated that differential land-management
effects on soil fauna functional groups can translate into differential effects on
the structures they produce, thus affecting soil organic matter, soil aggrega-
tion, porosity and water and nutrient availability to plants.
Figure 3 shows a hierarchical model of inter-correlated factors that
determine soil biodiversity and processes. Management practices (e.g. crop
rotation, tillage, organic resource use and application of agrochemicals such as
pesticides, herbicides and inorganic fertilisers) can cause positive or negative
changes in species composition, community structure and population sizes.
Some of the negative effects of management practices may be long-lasting and
result in a decline in the abundance and/or biomass of soil macrofauna
populations, or eliminate or reduce key species, i.e. species that play a
disproportionate role in ecosystem processes.
67,68
The use of organic inputs
and crop diversification through rotation favours macrofauna diversity due to
improvement in the abiotic conditions and increased substrate supply.
58,69-71
Agroforestry technologies, such as alley cropping, natural fallows (bush
fallows), planted fallows and biomass transfer systems can restore activities of
organisms such as earthworms, termites, ants and other microarthropods.
72-74
Ayuke et al.
69,72
found that organic residues from Senna spectabilis and
Tithonia diversifolia increased the population of earthworms by 400% and
