Lysis of soil microbial cells by CO2 or N2 high pressurization compared with chloroform fumigation

The classical chloroform fumigation-incubation (CFI) and fumigation-extraction (CFE) methods are nowadays among the most used for determining soil microbial biomass, although the chloroform lysing of microbial cells is not always complete. Here, we have tested a physical method, used for sterilizing foods but never in soil, based on N-2 or CO2 high pressurization (N2HP or CO2HP, respectively) to cause microbial cell lysis. The N2HP and CO2HP were tested on two soils differing for their organic matter content, one agricultural (AGR) and one forest (FOR), and firstly were compared with the CFI. The CO2 extra-flush from both soils during 10-d incubation by N2HP was lower than that by CFI method, whereas that by CO2HP was greater. Then, the lysis by CO2HP was compared with that by the CFE method by varying CO2 pressure and duration. The CO2HP, at proper conditions, was more efficient than CFE method to cause the lysis of soil microbial cells. Moreover, both CO2 pressure value and duration were important in increasing the extractable organic C compared to the CFE. The most successful combination of high CO2 pressure and duration was 4.13 MPa and 32 h. However, we cannot exclude that CO2HP might have caused the release of soil organic C not ascribable to living organic matter. Further studies using C-13 and/or N-15-labeled microbial cells should assess the release of abiotic organic C

Azoto

1. Introduzione p. 282 2. Determinazione dell\u2019azoto totale con analizzatore elementare p. 284 3. Determinazione dell\u2019azoto totale con metodo semi-micro-Kjeldahl p. 284 4. Determinazione dell\u2019azoto totale con metodo semi-micro-Kjeldahl modificato p. 287 5. Determinazione dell\u2019azoto totale estraibile con soluzione salina con metodo micro-Kjeldahl p. 291 6. Determinazione dell\u2019azoto totale estraibile con soluzione salina con metodo micro-Kjeldahl modificato p.294 7. Determinazione colorimetrica degli ioni ammonio estraibili p. 296 8. Determinazione colorimetrica degli ioni nitrato estraibili p. 298 9. Estrazione dell\u2019azoto totale idrolizzabile con acido cloridrico p. 300 10.Determinazione dell\u2019azoto totale idrolizzabile con acido cloridrico secondo il metodo micro-Kjeldahl p. 30

Metabolic responses of microbial community in soil amended with fresh leaves and leaf extracts from eucalyptus spp.

Field observations reveal that often large areas of soil surface beneath Eucalyptus occidentalis Endl. are completely bare or with scant vegetation. Moreover, previous studies have showed that other species of Eucalyptus, such as Eucalyptus camaldulensis Dehn, may be effective in suppressing seed germination and weed growth. Such effects have been ascribed to the large number of secondary metabolites within Eucalyptus leaves. Due to their inhibition activity against weeds, leaf extracts might be used for an integrated weed management context, in accordance with the Directive 2009/128/EC. Several studies exist about the effects of Eucalyptus leaf extracts on weeds, whereas they are lacking on soil microorganisms. Therefore, the aim of this study was to assess the effects of Eucalyptus leaf extracts on soil microbial biomass and activity, as well as on the relative abundance of main microbial groups. The extracts were obtained by hydrodistillation [essential oils (EOs) and hydrolates] and by water cold extraction (aqueous extracts) from leaves of both E. camaldulensis and E. occidentalis. Also, fresh leaves were tested. The soil was spread with EOs at doses of 2.64 or 3.52 \uf06dl g-1. They were applied by adding a proper water solution containing the given amount of EOs to 350 g of dry soil, so reaching 50% of its water holding capacity. The above solution held the emulsifier Fitoil at 0.5 mL L-1. Fresh leaves, dried at 40\ub0C for 48 hours, were chopped and applied at doses of 6.6 and 5.0 mg g-1 of dry soil for E. camaldulensis and E. occidentalis, respectively. Such litter application doses were those found, at field conditions (780 and 575 g m-2, respectively). Two controls were also prepared: one with water and another with water and Fitoil. After the addition of all the treatments, soils were incubated at room temperature (20-23\ub0C) in the dark for 35 days. At days 7 and 35, soils were analyzed for soil microbial biomass C and N. At the same days, the main microbial groups were investigated through the ester linked fatty acids (FAMEs). Moreover, 20 g of soil were incubated as above in 200 mL jars to determine the soil respiration rate (CO2 emission) during 36 days of incubation. Preliminary results showed, that EOs from the two species and at both doses exerted a significant biocidal action on soil microorganisms, while hydrolates, aqueous extracts and fresh leaves stimulated both microbial biomass and activity

From wastes to resources: citrus hydrolatesas natural biostimulants of soil microorganisms

The hydrolates result from the industrial extraction process of the essential oils through cold pressing of the citrus peels. Today, they are considered a waste to be disposed of. However, due to the presence of water soluble compounds (sugars, polyphenols, acids), hydrolates could be reused instead of being, due to the high economic burden, a problem in the disposal of the same, charged to the company.The aim of this work was to evaluate the effects of citrus hydrolate when directly applied as irrigation water on soil microbial biomass, activity and structure community. The soil used for the experiment was collected from the topsoil (0-10 cm) of a citrus orchard, air-dried and sieved at 2 mm. Then, 450 g of soil were placed in 1L plastic bottles and moistened up to 50% of the water holding capacity (WHC) by applying hydrolates and/or water. The tested hydrolates were obtained from three citrus species: Citrus Sinensis, Citrus Limon and Citrus Reticulata. The hydrolates were applied at three different doses to reach 1/3, 2/3 and 3/3 of the 50% of soil WHC. Respectively, 35, 70 and 105 mL of hydrolate were added to 450 g of air-dried soil. Distilled water was added when necessary to complement the 50% of WHC. Control soil was moistened up to 50% of its WHC with distilled water only. At the same time, 20 g of soil per each treatment were similarly incubated in 200 mL jars, sealed with rubber stopper holding silicon septa to monitor the emission of CO2. Four replicates per treatment were run. Soil samples were incubated in the dark at constant temperature (23.0 ± 0.5°C) and their humidity weekly adjusted up to 50% of WHC by adding distilled water. Microbial biomass C was determined according to the fumigation-extraction method after 1, 4, 8, 12 and 16 weeks of incubation. At the same time, soil fatty acid methyl esters were determined and used as indicators of the main microbial groups. The CO2 accumulated in the headspace of the jars was measured at days 2, 5, 7 during the first week, then weekly for the following month and finally bi-weekly until day 112. The preliminary results provided evidence that the three hydrolates, at different extent, stimulated the activity of soil microorganisms and affected soil microbial biomass and community structure

Monitoring of the effects of added carbon by citrus hydrolates waste in a soil.

The hydrolates are the waste to be disposed of are a product of the industrial extraction process of the essential oils through cold pressing of the citrus peels. However, due to the presence of water soluble compounds (sugars, polyphenols, acids), hydrolates could be reused instead of being, due to the high economic burden, a problem in the disposal of the same, charged to the company. The aim of this work was to evaluate the effects of citrus hydrolate when directly applied as irrigation water on soil. Was monitored soil chemical and biochemical property, in particularly effect of the high carbon addition on microbial biomass, activity and structure community and effect on carbon soil stock. The soil used for the experiment was collected from the topsoil (0-10 cm) of a citrus lemon orchard, air-dried and sieved at 2 mm. Then, 450 g of soil were placed in 1L jar and moistened up to 50% of the water holding capacity (WHC) by applying hydrolates and/or water. The tested hydrolates were obtained from three citrus species: Citrus Sinensis, Citrus Limon and Citrus Reticulata. The hydrolates were applied at three different doses to reach 1/3, 2/3 and 3/3 of the 50% of soil WHC. Respectively, 35, 70 and 105 ml of hydrolate were added to 450 g of air-dried soil. Distilled water was added when necessary to complement the 50% of WHC. Control soil was moistened up to 50% of its WHC with distilled water only. At the same time, 20 g of soil per each treatment were similarly incubated in 200 mL jars, sealed with rubber stopper holding silicon septa to monitor the emission of CO2. Four replicates per treatment were run. Soil samples were incubated in the dark at constant temperature (23.0 ± 0.5°C) and their humidity weekly adjusted up to 50% of WHC by adding distilled water. Microbial biomass C was determined according to the fumigation-extraction method after 1, 4 and 8, weeks of incubation. At the same time, soil fatty acid methyl esters (FAMEs) were determined and used as indicators of the main microbial groups. The CO2 accumulated in the headspace of the jars was measured at days 2, 5, 7 during the first week, then weekly for the following month and finally bi-weekly until day 60. This preliminary study for the possible use of citrus hydrolates as amenders and biostimulants for soil microorganisms showed that they might constitute readily available sources of carbon for microorganisms but at different extent, depending on the citrus species

Roadmapping the Transition to Water Resource Recovery Facilities: The Two Demonstration Case Studies of Corleone and Marineo (Italy)

The current exploitation of freshwater, as well as the significant increase in sewage sludge production from wastewater treatment plants (WWTPs), represent nowadays a critical issue for the implementation of sustainable development consistent with the circular economy concept. There is an urgent need to rethink the concept of WWTPs from the conventional approach consisting in pollutant removal plants to water resource recovery facilities (WRRFs). The aim of this paper is to provide an overview of the demonstration case studies at the Marineo and Corleone WRRFs in Sicily (IT), with the final aim showing the effectiveness of the resources recovery systems, as well as the importance of plant optimization to reduce greenhouse gas (GHG) emissions from WRRFs. This study is part of the H2020 European Project “Achieving wider uptake of water-smart solutions—Wider-Uptake”, which final aim is to demonstrate the water-smart solution feasibility in the wastewater sector. The main project goal is to overcome the existing barriers that hamper the transition to circularity through the implementation of a governance analysis tool. The preliminary actions in the two demonstration cases are first presented, while, subsequently, the water-smart solutions to be implemented are thoroughly described, highlighting their roles in the transition process. The achieved preliminary results underlined the significant potential of WRRF application, a great chance to demonstrate the feasibility of innovative solutions in the wastewater sector to overcome the existing social, administrative and technical barriers

Herbicidal activity of essential oils extracted from different Mediterranean species against Echinochloa crus galli

Weed infestation in agricultural fields can cause huge economic losses and low-quality crop yields. Echinochloa crus-galli (L.) P.Beauv. (barnyardgrass) is one of the greatest yields limiting weeds in rice cultivation systems. It is a cosmopolitan weed in both temperate and tropical regions and is reported as a weed in 36 different crops in 61 countries. The success of this weed may be attributed to the production of large numbers of small, easily dispersed seeds per plant, possession of seed dormancy, rapid development and ability to flower under a wide range of photoperiods, and relative resistance of mature plants to herbicide sprays. Thus, the best way to control barnyardgrass in an environmentally acceptable and sustainable approach is to develop eco-friendly and effective alternative means based on natural allelochemicals. Among the natural plant products, essential oils (EOs) constitute an important group. EOs may help reducing the use of synthetic herbicides and lead to less pollution and more safe agricultural products. Recently, the interest in exploring EOs with phytotoxic effects from aromatic plants for weed control has increased tremendously, because they do not persist in soil and do not leach into ground water. EOs extracted from Thymbra capitata (L.) Cav.; Mentha x piperita L.; and Santolina chamaecyparissus L. were reported to reduce the emergence and seedling growth of many weeds. The present investigation allows for a more detailed insight into the herbicidal activity of the previously mentioned EOs during spray foliar and irrigation application in post-emergence on E. crus-galli plants. T. capitata M. piperita and S. chamaecyparissus EOs were purchased from “Bordas Chinchurreta”, “Sigma-Aldrich” and and “Aromas de Ademuz”, respectively. Soil for the experiments was collected from the topsoil of a citrus field not treated with herbicides (Valencia, Spain), that was air-dried and sieved at 1 cm. E.crus-galli seeds were purchased from Herbiseed (England), and germinated in a germination-growth chamber at 30 ± 0.1 °C, 16 h in light and 20 ± 0.1 °C, 8 h in dark. Once the seedlings of E.crus-galli emerged, they were placed on pots (8x8x7 cm) filled with 2 cm of perlite at the bottom and 5 cm of the collected soil. Ten pots per treatment were prepared and placed in the greenhouse. In order to find the most effective dose of EOs and its adequate mode of application, different concentrations were used: 12, 16 and 20 µL/mL for Mentha and Santolina EOs and 4, 8 and 12 µL/mL for Thymbra EO. Fitoil was used as emulsifier at a concentration of 0.05% (v/v). Plants of barnyardgrass were treated at two-leaf stage by irrigating and spraying mode of application. To monitor the experiments, photos were taken after 24, 48 and 72 hours; and then once a week. The photos were processed with Digimizer software to obtain different data: efficacy of the treatment, level of damage, height of plants, weed plant fresh and dry weight