Agriculture Reference
In-Depth Information
like cellulose, hemicellulose and lignin (Martínez et al.
2010
; Bugg et al.
2011
).
Available literature revealed that, there is little information earned on these aspects
of decomposition of aquatic macrophytes.
The decomposition in aquatic macrophytes generally initiates with natural se-
nescence and is caused by abiotic and biotic processes. The abiotic process includes
physical breakdown i.e., leaching and fragmentations. On the other hand, the biotic
process includes autolysis and microbial breakdown i.e., degradation of structural
polymers into smaller units. The different genera of bacteria and fungi and con-
sumption of debris by macro invertebrates perform the process of decomposition.
Earlier studies on water hyacinth decomposition revealed that the decay rates may
vary with tissue nitrogen and fiber content. About 30 % of initial dry weight is lost
solely by abiotic processes and remainder by microbial processes (Gaur
1987
).
The relative contributions of the bacteria and fungi to the overall decay of water
hyacinth (
E. crassipes
(Mart.) Solms) determined by Gaur (
1987
). Less number of
bacteria (13) and more number of fungi (24) associated with in-situ decaying of
litter of water hyacinth (Singhal et al.
1992
). Most bacteria were Gram-negative,
facultative anaerobes, and able to degrade polysaccharides and proteins. The ter-
restrial fungi were predominant. Six fungi grew well on water hyacinth leaves and
were actively involved in the degradation of lignocellulose. Rest of the fungi grew
slowly or failed to grow on water hyacinth leaves. Decomposition experiments
have demonstrated that the first 4 days of decay are dominated by non-microbial
processes (Singhal et al.
1992
). Scientists have observed rates of abiotic and mi-
crobial decomposition in all types of hyacinth leaves is dominated by physical
leaching in initial phase of 4 days duration and later by microbial processes. The
largest part of physical leaching takes place within the first 4 days. Thereafter, the
weight loss occurs due to physical leaching that declines exponentially. The weight
loss by microbial decomposition is minimal in the initial phase but increased expo-
nentially in the later phase. The bloom leaves decompose significantly faster than
post bloom leaves, and post bloom green leaves decompose faster than post-bloom
brown leaves. The rate constants of abiotic decomposition recorded significantly
higher in post bloom leaves and microbial decomposition is 15 and 55 %, respec-
tively, on the other hand, in pre-bloom leaves it was 33 and 19 % where as in post
bloom green leaves and 24 and 6 % in post bloom leaves (Singhal et al.
1992
). The
variation in rate of decomposition is due to age of the leaves but role of other fac-
tors cannot be ruled out.
The compost maturity is generally observed by color appearance showing yel-
lowish coloration and without precipitation with starch—iodine test indicating the
presence of simple sugars. Absence of sulfides can be depicted by no coloration
on lead acetate strip. On the other hand, presence of nitrate is possible to detect by
red coloration. Change in C:N ratio during biodegradation revealed that the total
organic carbon content in mature compost should be declined by 50 % and total N
contents must be increased in composed to that of green biomass.
Although initial pH of the compost remain in acidic range as it is found in cell
sap of most plant. The production of organic acids during early stages of compost-
ing, initial pH turned towards acidic range but with rise in temperature, shift in pH
