Agriculture Reference
In-Depth Information
The reduction in total solids (TS) of biomass is directly related to the extent of
biodegradation. Variation in C:N ratio is another important parameter to determine
the qualitative status of the compost. The C:N ratio of mature compost is found to
be low as compared to the initial ratio of 40:1 in GAB mixed with slurry and urea.
The assimilation of C in microbial cell and volatilization of CO
2
considered as the
possible reasons of decline in C:N ratio. The assimilation is further followed by
mineralization of C and N (Alexander
1983
).
The temperature is one of the most important physical conditions in determin-
ing how rapid natural materials are degraded, assimilated and mobilized. In case
of water hyacinth, author observed that maximum biodegradation occurred in the
range of 30-40 °C because, mesophilic microorganisms remains more active at this
temperature range. On increasing temperature, decline in rapidity of composting
was recorded. At high temperature, all reactive compounds such as sugars, fats etc.
denatured and microbes are killed and great deal of energy released because of
oxidation of carbon to CO
2
(Dalzell
1979
). Further, Khandelwal (
1995
) noticed that
composting process absorbed heat energy from the surroundings and its entrapment
in the compost bed cannot be ruled out.
In fact, after mulching the compost, the nutrient status of eroded soil showed
remarkable increase of total organic C content by six times. The nitrogen contents
were 2.5 times and phosphorus exhibited 3 times higher than that of eroded or sub-
standard soil. The potassium contents on after mixing compost was observed to be
4 fold higher that leads to a significant increase in its mineral status and correspond
to soil fertility. The increase in net primary productivity (NPP) and gross primary
productivity (GPP) is thus, directly related to the improved status of soil due to bet-
ter availability of solubilized nutrients after addition of compost. Several workers
(Biswas et al.
1971
; Gaur et al.
1972
) reported improvement of soil structure and
chemical characteristics, texture and appearance by using agro-compost. Naskar
et al. (
1986
) observed increase in productivity on application of water hyacinth
compost in agriculture. Howard and Lee (
1993
) observed increase yield of sweet
potato using EC compost. Water holding capacity is an important parameter and
compost also increased water holding capacity of soil.
The chemical composition of both
E. crassipes
and
I. aquatica
showed that
along with sufficient quantity of hemicellulose, quite good amount of lignin was
also present which makes the residue unsuitable for hydrolysis due to its recalcitrant
nature. It is also reported to be toxic to micro-organisms so alters the process of deg-
radation, the greater need of today is to evolve appropriate pretreatment method that
may diminish the protective effect of lignin as most of the potential aquatic biomass
residues are heavily lignified. The pretreatment is essential to enhance the suscepti-
bility of lignocelluloses to ligno-cellulolytic enzyme action. Over the years, several
pretreatments methods including physical, chemical and biological treatments have
been proposed by many workers to modify the substrates and render them as more
susceptible for bioconversion and enzymatic processing. Physical methods e.g., ball
milling (Fan et al.
1980
), Hammer milling (Mandels et al.
1974
), Vibroenergy mill-
ing (Ghose
1969
), Extrusion (Han and Callihan
1970
), Pyrolysis (Shafizadeh
1977
),
Irradiation (Kunz and LaRur
1975
), Steaming (Bender et al.
1970
) etc. Chemical
