Agriculture Reference
In-Depth Information
A
B
MANURE
MANURE + EARTHWORMS
200
12000
SEWAGE
SEWAGE + EARTHWORMS
180
F p
Earthworm 7.9 0.023
Time 5.5 0.000
Ew
160
10000
140
8000
120
×
Time 3.8 0.003
100
6000
80
4000
60
40
2000
20
0
0
0 2 4 6 8 10 12 14 16
0 2 4 6 8 10 12 14 16
Time (weeks)
Time (weeks)
FIGURE 20.4 (A) Bacterivore and (B) fungivore nematode abundance (mean ° SE) in presence and absence
of the earthworm Eisenia andrei during vermicomposting of cow manure and sewage sludge. (From
Domnguez et al. 2003.)
The density of bacterivorous nematodes increased with time during the first 6 weeks in sewage
sludge in the presence or the absence of earthworms; after week 6, the density of bacterivorous
nematodes started to decline independently of the presence of E. andrei in the culture boxes.
However, it was remarkable that the number of bacterivorous nematodes was always considerably
lower in the presence of earthworms, and that these differences were statistically significant after
10 weeks (Figure 20.4A). Fungivorous nematodes did not appear in the sewage sludge during the
16 weeks of the experiment, but fungivorous nematodes appeared in cow manure after 6 weeks;
their numbers increased strongly in the absence of earthworms and remained constantly low in the
presence of E. andrei . After 16 weeks, the density of fungivorous nematodes was 150 ° 30
nematodes g −1 dry weight in the treatment with no earthworms and only 10 ° 2 nematodes g −1 dry
weight in the treatment with earthworms (Figure 20.4B).
APPLICATIONS OF VERMICOMPOSTING
From the point of view of its commercial development and application, vermicomposting and any
other biological treatment of organic wastes can be considered two-step processes. The first step
is to convert the organic wastes into nontoxic products, eliminating or reducing human pathogen
content and the concentrations of heavy metals and organic pollutants. A second step takes the
process further by converting the new stable product into a valuable organic soil amendment with
greatly increased microbial activities and by the humification of the organic material, which
enhances the presence of plant growth promoters (Atiyeh et al. 2002b) (see Chapter 18 this volume)
( Figure 20.5 ) . So, a decision must be made, and the main criterion for this is the quality of the
organic waste. If the residue is Ñbad,Ò then it may just be stabilized; if it is Ñgood,Ò then there is
the possibility of transforming it into a valuable organic soil amendment. A bad waste is, for
example, sewage sludge because of its heterogeneous and highly variable composition and high
concentration of human pathogens and organic and inorganic contaminants. In this case, the
objective of the treatment should be to rapidly stabilize the material, and probably regular com-
posting is a better solution than vermicomposting. A good waste, for example, is most animal
wastes, wine residues, food wastes, or milk industry sludges. They are good because they have no
pollutants, have a homogeneous composition, and have a good balance of nutrients; in this case,
the objective could be to obtain a good organic soil amendment, and vermicomposting is probably
the better choice (Figure 20.5).
 
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