Agriculture Reference
In-Depth Information
number of microorganisms (Duong et al.
2009
), the microbial degradability of plant
constituents is well documented in the literature (Insam and de Bertoldi
2007
). The
relative size of crop residue is an important issue in crop residues decomposition;
crop residues that are broken through tillage processes will have smaller size than
crop residues that is left un-disturbed on soil. The residues with smaller fraction
will have larger surface area and consequently larger microbial activities, which
makes the decomposition process faster (Vigil and Kissel
1995
). Under field condi-
tion, it is important that crop residues get in intimate touch with the decomposing
organisms and that the optimum environmental conditions are present in terms of
moisture, dissolved oxygen required for decomposition, and balanced C/N of the
residues.
1.4.3
C/N Ratio: The Fact of the Case
The C/N ratio has a great influence on the decomposition rate of organic materials
in soil. A material with narrow C/N ratio e.g., fresh manure compared to material
with a wider C/N e.g., olive pruning, would be much easier for microorganisms to
decompose given that it sustain proper supply of C and N.
The benefit of crop residues incorporation depends on the degree of suitability
of field conditions and residues characteristics. If soil is not provided with proper
moisture content then decomposition of the crop residues will be slow. Moreover,
the C/N of the crop residues might necessitate addition of external N to balance the
ratio for proper decomposition and controversially increase the cost of the opera-
tion. It is potentially possible to avoid the cost of the external N input in the case
where different crop residues are provided on the field in a planned manner in order
to have a suitable C/N. This is highly recommendable in organic farming as it favors
crop polyculture, crop diversity and agroeco systems complexation. Crop residues
incorporation into soil might require less energy and machinery than composting
process; plant residues or green manure will be incorporated or buried in subsoil
all at once while the composting process require frequent turning during the active
stages of the process.
However, the cost of the composting process varies depending on the compost-
ing method; if composting is to be carried out in a compost facility then cost will
include transportation of the crop residues from the field to the composting facility
while this cost will be ignored in on-farm composting. The cost in the composting
process should include the cost of substrate transport, storage, preparation, e.g.,
grinding and mixing, turning and operational cost for soil application. A good com-
poster might not need to add external N to adjust the C/N of the starting mixture
but can use different types of residues mixed together to provide the proper starting
C/N.
Crop residues applied directly to soil might help pathogens and weeds seeds
continue their lifecycles and establish in soil while during the composting pro-
cess high temperature, antibiotics released and antagonism between beneficial and
