ABIOTIC AND MICROBIAL DECOMPOSITION OF PRE-BLOOM AND POST-BLOOM LEAVES OF WATER HYACINTH (EICHHORNIA-CRASSIPES (MART) SOLMS)

Rates of abiotic and microbial decomposition in pre- and post-bloom le aves of water hyacinth are determined under laboratory conditions. Dec omposition in all types of hyacinth leaves is dominated by physical le aching in an initial phase of 4 days duration, and later by microbial processes. The largest part of physical leaching takes place within th e first 4 h. Thereafter, the weight loss due to physical leaching decl ines exponentially. The weight loss by microbial decomposition is mini mal in the initial phase but increases exponentially in the later phas e. Pre-bloom leaves decompose significantly faster than post-bloom lea ves, and post-bloom green leaves decompose faster than post-bloom brow n leaves. The rate constants of abiotic decomposition are significantl y higher in post-bloom leaves as compared with pre-bloom leaves, while microbial decomposition is significantly higher in pre-bloom leaves. After 30 days, the dry mass loss by abiotic and microbial decompositio n is 15% and 55%, respectively, in pre-bloom leaves, 33% and 19% in po st-bloom green leaves, and 24% and 6% in post-bloom brown leaves.