The microstructural changes of montmorillonite and kaolinite, amended with organic debris (leaves of chestnut or beech), microbial inocula and nutrients are subjected, for 30 days at 25°C, to rewetting/air-drying cycles or kept continuously moist at water holding capacity, have been studied in order to evaluate the interactions between the decomposition processes of plant residues and clay microstructural organisation in different pore-water regime. The microstructure was studied by mercury porosimetry, nitrogen adsorption at 77 °K, and scanning electron microscopy. Some characteristics of decomposition processes were determined by measuring the residual total organic C and N, the amount of humified fractions, the relative HA and FA content and their molecular weight distribution at the end of the incubation. As expected, a different structural organisation, was observed at the end of experiments, on the different type of clays. Moreover, new poral classes were found in each clay as the result of the microbial metabolism. In turn, the debris decomposition is also significantly affected by clay physico-chemical properties. The organic matter transformation in the presence of montmorillonite occurs at rapid rate, as shown by the low amount of residual C at the end of the experiment. The humified material was mainly represented by low molecular weight fulvic acids. On the contrary, in kaolinite samples, the transformation processes were slow, as indicated by the large amount of residual C. Moreover, higher amount of humic acids were found in humified fraction. The samples submitted to cycles of air-drying and rewetting showed only small differences in their microstructural organisation in comparison with those kept continuously moist. This could be ascribed to the short time of the air-drying cycles which did not bring to a complete dryness. In the decomposition processes, the samples maintained continuously moist and amended with chestnut leaves, showed a larger amount of hum ified C. The different nature of leaves affect both, microstructural organisation, as suggest by small change in pores size distribution and the decomposition processes, as indicates by the different amount of C residues, hum ified material and by the C/N ratio.
Interactive effects among clay microstructure, decomposition of plant residues and humification processes
D'Acqui LP;
1996
Abstract
The microstructural changes of montmorillonite and kaolinite, amended with organic debris (leaves of chestnut or beech), microbial inocula and nutrients are subjected, for 30 days at 25°C, to rewetting/air-drying cycles or kept continuously moist at water holding capacity, have been studied in order to evaluate the interactions between the decomposition processes of plant residues and clay microstructural organisation in different pore-water regime. The microstructure was studied by mercury porosimetry, nitrogen adsorption at 77 °K, and scanning electron microscopy. Some characteristics of decomposition processes were determined by measuring the residual total organic C and N, the amount of humified fractions, the relative HA and FA content and their molecular weight distribution at the end of the incubation. As expected, a different structural organisation, was observed at the end of experiments, on the different type of clays. Moreover, new poral classes were found in each clay as the result of the microbial metabolism. In turn, the debris decomposition is also significantly affected by clay physico-chemical properties. The organic matter transformation in the presence of montmorillonite occurs at rapid rate, as shown by the low amount of residual C at the end of the experiment. The humified material was mainly represented by low molecular weight fulvic acids. On the contrary, in kaolinite samples, the transformation processes were slow, as indicated by the large amount of residual C. Moreover, higher amount of humic acids were found in humified fraction. The samples submitted to cycles of air-drying and rewetting showed only small differences in their microstructural organisation in comparison with those kept continuously moist. This could be ascribed to the short time of the air-drying cycles which did not bring to a complete dryness. In the decomposition processes, the samples maintained continuously moist and amended with chestnut leaves, showed a larger amount of hum ified C. The different nature of leaves affect both, microstructural organisation, as suggest by small change in pores size distribution and the decomposition processes, as indicates by the different amount of C residues, hum ified material and by the C/N ratio.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
