Roberto Cardelli

A comparison of soil quality in adjacent cultivated, forest and native grassland soils

Changes in soil quality after 45 years of continuous production of corn (Zea mays L.) by the conventional tillage method (C) compared with adjacent poplar forest (F) and native grassland (G) sites were examined. The investigated parameters were: total and humified organic C, total N, light fraction content and composition, water-soluble organic C (WSOC), water-soluble carbohydrates (WSC), phenolic substances, biomass C, cumulative CO2-C (soil respiration) (Cm), enzyme activities (alkaline phosphatase, protease, β-glucosidase, urease, catalase and dehydrogenase). Empirical indexes of soil quality were also calculated: biomass C/organic C, specific respiration of biomass C (qCO2), death rate quotient (qD), metabolic potential (MP), biological index of fertility (BIF), enzyme activity number (EAN) and hydrolysing coefficient (HC). Results indicate that long-term corn production at an intensive level caused a marked decline in all examined parameters. Between the undisturbed systems, native grassland showed higher values of soil quality parameters than forest site. The indexes most responsive to management practices that may provide indications of the effects of soil cultivation, as well as of the differently undisturbed ecosystems were: organic C, WSC, Cm, protease, β-glucosidase, urease and HC. Soil enzyme activities were well related with, and not more sensitive than organic carbon.

Cocomposting of olive oil mill by-products: chemical and microbiological evaluations

An experiment was performed to evaluate the possibility of cocomposting wet husk and wastewater, the two main olive oil mill by-products. The pH, E.C., total C and N, humic substances, phenolics, volatile acids, lipids, P and K plus yeast, fungi, heterotrophic-, cellulolytic- and nitrifying bacteria and phytotoxicological parameters were monitored during a 120-day stabilization process. Performances of the composting system adopted, together with physicochemical characteristics of starting material and final product, are reported. Composting was found to induce a high level of organic matter change, with decrease of organic carbon, total nitrogen and C/N ratio, as well as of the easily biodegradable lipids. Good metabolic activity of the microbiological population, with the exception of the nitrifying bacteria, and a complete detoxification of starting material were also observed. The results obtained suggested that composting might be an adequate low-cost strategy for the recycling of olive oil by-products.

Biochemical properties of a Mediterranean soil as affected by long-term crop management systems

Soil biochemical properties under long-term crop management systems may be useful indicators of soil quality. We measured seven enzyme activities and six calculated biological indices at four adjacent study sites on an andosol in a semiarid area of eastern Sicily. Soils were sampled under natural grassland (NG), orange-grove (OG), winter wheat (WW) and horticultural crop (HC) managed according to local agricultural usage. The enzymes investigated were dehydrogenase, catalase, protease, alkaline phosphatase, β-glucosidase and amylase. The calculated biological indices were hydrolyzing coefficient, enzyme activity number, biological index of fertility, metabolic potential, lability index and C management index. Tilled management systems (WW and HC) were lower in total organic C and N and in all the enzyme activities and biological indices than in untilled management systems (NG and OG). Catalase activity and hydrolyzing coefficient were the most suitable soil biochemical properties for differentiating between the effects of different crop management systems, because of their analytical simplicity and rapidity.

Impact of Salinity on Soil Biological Activities: A Laboratory Experiment

In a laboratory study, the impact of sodium chloride (NaCl) on soil quality was examined through the monitoring of soil biological activity. Artificially salinized samples were prepared from the nonsaline soil by adding NaCl at electrical conductivities (EC) 2, 4, and 8 dS·m−1 in saturated extracts. The samples were kept at 25 °C and at 50% field capacity during an incubation period of 40 days. The ATP, soil basal respiration, protease, amylase, alkaline phosphatase, dehydrogenase, and catalase activities were monitored. The biological index of fertility (BIF), the enzyme activity number (EAN), and the metabolic potential (MP) were calculated. A regression analysis was used to calculate parameters from cumulative data of carbon dioxide (CO2) evolution. The size of microbial biomass, measured throughout the determination of ATP, was decreased by increasing salinity. Increasing concentrations of salt up to an EC of 4 dS·m−1 led to an increase of soil respiration. During incubation, protease and dehydrogenase were inhibited by NaCl; however, amylase, alkaline phosphatase, and catalase were not affected by the salt addition. Between indices, EAN confirmed the general depressive effect of NaCl on the biological properties of soil, while MP showed a pattern similar to that of soil respiration. Results of this study chiefly indicate that ATP, soil respiration, protease, dehydrogenase, EAN, and MP were able to put in evidence the effects of NaCl on soil biological activity and may be regarded as suitable tools to show the physiological reaction of soil microbial biomass under saline stress.

Evolution of biochemical parameters during composting of urban wastes

An experiment was performed for evaluating the most suitable biochemical parameters to measure dynamics of substrate transformation during composting of the organic fraction derived from preselected urban wastes and wood bark mixture. Changes of chemical (organic C, hydrosoluble sugars, total and mineral N, humified fraction, volatile acids and phenolic compounds) and biochemical (microbial respiration, biomass C, qCO2, dehydrogenase, catalase, urease activities, FDA, and BIF) parameters were monitored for 120 days. Limited changes in organic C, total nitrogen, and humification characteristics were observed during composting. Dehydrogenase and catalase activities, BIF and FDA showed small changes during composting. Urease activity and, with some limitations regarding the early stages of composting, microbial respiration and qCO2, were found to be the most suitable parameters to measure dynamics of substrate transformation during composting of preselected urban wastes.

Relationships between mineralogical composition, water absorption and hydric dilatation in the “Macigno” sandstones from Lunigiana (Massa, Tuscany)

Despite its good technical properties, the “Macigno” sandstone undergoes a typical process of decay when used outdoor, consisting prevalently in a flaking of the stone surface with detachment of rock fragments. In order to understand the causes of this decay, the relationships between mineralogy and physical rock properties were investigated. Twenty-six rock samples were collected from quarries situated near the villages of Fivizzano and Pontremoli (the Lunigiana area of northwestern Tuscany, Italy) and examined for their chemical (XRF), mineralogical (XRPD) and petrographic (optical microscopy) characteristics, as well as physical properties such as real and bulk densities, water absorption capacity and linear dilatation coefficient of water-saturated samples. The phyllosilicate minerals of the sandstone were studied on oriented aggregates of the <4 μm fractions by X-ray powder diffraction, and their chemical composition determined by EDS microprobe analyses. The cationic exchange capacity (C.E.C.) was measured on fifteen selected samples. The studied sandstones are fine- to coarse-grained, arkoses and lithic arkoses whose colour ranges from grey to yellowish. The normative carbonate fraction consists essentially of calcite; its amount is generally low (<1–10%), with the exception of three samples collected in the Turlago-Labiano quarry, which contained calcite concentrations of up to 14, 15 and 38%, respectively. The normative non-carbonate fraction is made up of quartz (19–34%), K-feldspars (7–13%), plagioclase (14–33%), mica-like minerals (4–10%) and chlorite s.l. (5–26%). Mica-like minerals include muscovite (illite), minor amounts of biotite and sporadic illite/smectite mixed-layers (I/S). Chlorite s.l. includes chlorite s.s. and chlorite/smectite mixed-layer phases (Chl/S). The content of the sandstone smectitic component, predominantly associated to Chl/S, ranges from 1 to 7 (wt.%). C.E.C. varies from 2.4 to 11.1 meq/100g. Water absorption capacity (wt.% of dry samples) as well as hydric dilatation of the stone upon water saturation increase with increasing smectite content, indicating that this swelling component may play an important role in the “Macigno” sandstones decay.

Suitability of a winery-sludge as soil amendment

Abstract A laboratory study was carried out to assess the suitability as soil amendment of a sludge obtained through aerobic depuration of wastewaters from a winery (‘winery-sludge’). During a 180-day incubation period, changes in chemical and biological properties of a soil amended with 0·5 and 2·5% of sludge were evaluated. At the end of the experiment, winery-sludge increased the amount of available N, P, K and S, organic and potentially mineralizable carbon, and total microbial activity, while pH, biomass C, dehydrogenase activity, decomposition rate, water-soluble sugars, phenolic compounds and chemical oxygen demand (COD) were not affected by the sludge application. A germination test indicated that the winery-sludge did not show toxicity even immediately after its addition to soil. The great build-up of salinity in soil amended with the highest dose could give rise to risks to crops and environment, so there is a need for field tests.

Microbially-enhanced composting of wet olive husks

The production of a compost from olive wet husks is described. The process is enhanced through the use of starters prepared with virgin husks enriched with selected microbial cultures. This approach, with respect to composting without the use of starters, allows to achieve faster start of the process (10 vs. 45 days), deeper humification (humification rate 19.2 vs. 12.2), shorter maturation time (2 vs. 4-5 months) and better detoxification of the starting material. Furthermore, the compost produced can effectively substitute for turf as a cultivation substrate in horticulture at greenhouse level, with beneficial effects on nutraceutical traits of tomato fruits.

Organically and conventionally managed soils: biochemical characteristics

ABSTRACT The objective of this study was to determine the effect of organic farming, in field (OF) and in glass-house (OFG), on selected soil biochemical properties compared with conventional farming (CF) in a horticultural area characterized by the same climate, soil type and topography. Results show that all soil enzyme activities were generally higher in OFG compared with OF and CF systems. Because of the different conditions of temperature, OFG presented a major loss of organic matter too. Catalase activity, metabolic potential (MP) and biological index of fertility (BIF) are suggested as the most suitable soil biological indicators for differentiating between organic (OF and OFG) and conventional (CF) farming systems. Organic farming systems, because of application of organic amendments and less deep tillage, showed a greater capacity to improve soil quality as compared with conventional production practices.

Microbially-enhanced composting of olive mill solid waste (wet husk): Bacterial and fungal community dynamics at industrial pilot and farm level.

Bacterial and fungal community dynamics during microbially-enhanced composting of olive mill solid waste (wet husk), used as a sole raw material, were analysed in a process carried out at industrial pilot and at farm level by the PCR-DGGE profiling of the 16 and 26S rRNA genes. The use of microbial starters enhanced the biotransformation process leading to an earlier and increased level of bacterial diversity. The bacterial community showed a change within 15 days during the first phases of composting. Without microbial starters bacterial biodiversity increased within 60 days. Moreover, the thermophilic phase was characterized by the highest bacterial biodiversity. By contrast, the biodiversity of fungal communities in the piles composted with the starters decreased during the thermophilic phase. The biodiversity of the microbial populations, along with physico-chemical traits, evolved similarly at industrial pilot and farm level, showing different maturation times.