Agriculture Reference
In-Depth Information
sludge (Mitchell et al. 1980; Dominguez et al. 2000); agricultural resi-
dues (Bansal and Kapoor 2000); weeds (Gajalakshmi et al. 2001); cattle
dung (Gunadi et al. 2002); industrial refuse such as paper wastes (Butt
1993; Elvira et al. 1995; Gajalakshmi et al. 2002); sludge from paper mills
and dairy plants (Elvira et al. 1997; Banu et al. 2001); domestic kitchen
wastes (Sinha et al. 2002); urban residues and animal wastes (Edwards et
al. 1985; Edwards 1988) can be vermicomposted (Sharma et al. 2005).
Effects of vermicomposting on pH, electrical conductivity (EC), C:N
ratio and other nutrients have been documented. Earthworm activity
reduced pH and C:N ratio in manure (Gandhi et al. 1997; Atiyeh et al.
2000b). Chemical analysis showed vermicompost had a lower pH, EC, or-
ganic carbon (OC) (Nardi et al. 1983; Albanell et al. 1988; Mitchell 1997),
C:N ratio (Riffaldi and Levi-Minzi 1983; Albanell et al. 1988), nitrogen
and potassium and higher amounts of total phosphorous and micronutri-
ents compared to the parent material (Hashemimajd et al. 2004). Slightly
decreased pH values of vermicompost compared to traditional compost
might be attributed due to mineralization of N and P, microbial decom-
position of organic materials into intermediate organic acids, fulvic acids,
humic acids (Lazcano et al. 2008; Albanell et al. 1988; Chan and Griffi ths
1988; Subler et al. 1998) and concomitant production of CO 2 (Elvira et al.
1998; Garg et al. 2006). Vermicomposting of paper mill and dairy sludge
resulted in 1.2-1.7 fold loss of organic carbon as CO 2 (Elvira et al. 1998).
In contrast to the parent material used, vermicomposts contain higher hu-
mic acid substances (Albanell et al. 1988). Humic acid substances occur
naturally in mature animal manure, sewage sludge or paper-mill sludge,
but vermicomposting drastically increases the rate of production and their
amount from 40-60 percent compared to traditional composting. The en-
hancement in humifi cation processes is by fragmentation and size reduc-
tion of organic matter, increased microbial activity within earthworm in-
testine and soil aeration by earthworm feeding and movement (Dominguez
and Edwards, 2004). EC indicates the salinity of the organic amendment.
Minor production of soluble metabolites such as ammonium and precipi-
tation of dissolved salts during vermicomposting lead to lower EC values.
Compared to the parent material used, vermicomposts contain less soluble
salts and greater cation exchange capacity (Holtzclaw and Sposito 1979;
Albanell et al. 1988). C:N ratio is an indicator of the degree of decompo-
 
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