Maria De Nobili

Relationships between soil porosity, root development and soil enzyme activity in cultivated soils

Abstract Porosity and pore size distribution from thin sections, prepared from undisturbed Ap horizon samples taken from a zero- versus conventional-tillage field experiment, were analysed by means of a Quantimet 720 image analysing computer. The length and the size distribution of plant roots were determined using the same image analyzer. Soil urease and phosphatase activity in soil samples from the plots of this field experiment was also determined. Total porosity was significantly higher in conventionally tilled plots, but the proportion of pores ranging from 30 to 500 μm in equivalent pore diameter, which are considered the most important both in soil-water-plant relationships and in the maintenance of a good soil structure, was higher in no-tilled plots. Root development showed a strict relationship with the presence of smaller pores which were more numerous in no-tilled plots. Enzyme activity was also higher in these plots than in the conventionally tilled plots. The relationships of such enzyme activities and the various pore size classes in each type of soil showed a positive common trend between the two enzyme activities and the percentage area of pores ranging from 30 to 200 μm in equivalent pore diameter. A significant correlation was observed between the degree of porosity in this range and urease activity.

Humification index (HI) as evaluation of the stabilization degree during composting

Abstract The stabilization of a pile of ground urban refuse was monitored during five months. Carbon dioxide evolution, temperature, moisture level, organic matter, and pH were measured regularly. The humification index (HI) of organic matter extracted by 0.1 M Na4P2O7 plus 0.1 M NaOH was found to decrease linearly with time during the thermophilic phase from about 1.4 to 0.4. Turning of the pile caused a drop in the HI values, but the index increased again every time the temperature of the static pile reached 65°C. The value of the humification index in water extracts (HIw) reached a maximum after 4 d in the superficial layers and after 11 d at a depth of 30 cm. HIw values were found to decrease hyperbolically with time during the thermophilic phase.

Mineralization and humification pathways in two composting processes applied to cotton wastes

Abstract We compared the end products and the time courses of mineralization and humification during the theermophilic phase of two different composting processes used to transform residues from cotton carding. The two processes were started under different conditions with respect to percentage humidity, aeration system and C/N ratio. Except for pH and the electric conductivity of aqueous extracts, most of the parameters evolved differently in the two processes examined. The following analyses were performed to assess the degree of evolution of the two composts: weight loss of the total compost mass, cellulose, hemicellulose and lignin content and amount of humified and non humified organic C in 0.1 M Na4P2O7 0.1 M NaOH extracts. At the end of the thermopholic phase, mineralization was more intense, to the detriment of humification, in the composting process that involved forced air ventilation and a lower C/N ratio (35). In the process where manual turning was used throughout the experiment, mineralization was somewhat slower notwithstanding the higher C/N ratio (80), but was accompanied by more intense humification, as shown by the electrofocusing profiles of humic substances extracted in 0.5 M NaOH. At the end of the experiment weight loss was about 50% in both processes, however the content of cellulose and hemicellulose was lower in the compost obtained from the process where manual turning was used throughout the experiment. Forced air ventilation and the lowering of the C/N ratio to 35 did not have any positive effect on the time needed for composting nor on the quality of the end product.

Organic polyanions act as complexants of prion protein in soil

The persistence of prions, the causative agents of transmissible spongiform encephalopathies, in soil constitutes an environmental concern and substantial challenge. Experiments and theoretical modeling indicate that a particular class of natural polyanions diffused in soils and waters, generally referred to as humic substances (HSs), can participate in the adsorption of prions in soil in a non-specific way, mostly driven by electrostatic interactions and hydrogen bond networks among humic acid molecules and exposed polar protein residues. Adsorption of HSs on clay surface strongly raises the adsorption capacity vs proteins suggesting new experiments in order to verify if this raises or lowers the prion infectivity.

Heavy Metal Content in Xylem Sap (Vitis Vinifera) from Mining and Smelting Areas

AbstractNo data are available on the content of heavy metals in the xylem sap of grapevines growing in contaminated areas. The aim of this work was to obtain data on the concentration of Pb, Zn, Cd and Cu in the xylem sap of grapevine (Vitis vinifera) cultivar Monica (ungrafted), growing near contaminated sites: a smelter, an abandoned and an active mine, and to investigate relationships between xylem sap mineral composition and the heavy metal content of the soil. The concentrations of Pb, Zn, Cd and Cu in the sap were enhanced compared to that of the soil, ranging from 4.3 to 611.4 µg Pb

Iron allocation in leaves of Fe-deficient cucumber plants fed with natural Fe complexes

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Plant traits shape the effects of tidal flooding on soil and plant communities in saltmarshes

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