Fulvia Tambone’s research while affiliated with University of Milan and other places

Background: Landscape features (LF—i.e., the natural and semi-natural areas in agricultural landscapes) positively contribute to soil organic carbon (SOC) sequestration and storage among farmlands. LF-related SOC partitioning still needs context-specific investigation to properly address climate change mitigation goals. Not many studies address LF phytocoenoses traits relation with SOC partitioning. Our study investigates SOC partitioning (total organic carbon [TOC]; labile dissolved organic carbon [DOC]; stable recalcitrant organic carbon [ROC]) between arable fields (AGR) and semi-natural/natural components (NAT: herbaceous field margins, young/mature hedgerows, young/mature woods) in a temperate alluvial pedoclimatic context (Po Plain, Northwestern Italy). Methods: We compared topsoil SOC and its fractions (0–20 cm depth) between: AGR-NAT sites; hedgerows (HED)-AGR sites; and different ecological quality degrees (phytocoenoses were classified by Biological Territorial Capacity [BTC] values and Index of Vegetation Naturalness categories [IVN]--). Results: Our results confirmed a significantly different SOC partitioning behaviour between AGR and NAT sites (NAT: +79% TOC; +409% ROC); AGR sites were negatively correlated with ROC. TOC was a robust ROC predictor. HED had significantly higher TOC (+71%) and ROC (+395%) compared to arable fields, with the highest values in mature hedgerows. DOC showed contrasted behaviours. A linear regression model on BTC and IVN (predictors) and TOC and ROC showed significant positive relationships, especially for ROC. Conclusions: Our study confirmed the LF role in long-term SOC storage among farmlands, which should be coupled with AGR management (with prevalent short-term SOC fractions). LF ecological quality was a determining factor in total and long-term SOC. Proper LF management is pivotal to aligning climate change mitigation goals with other ecological benefits.

Among the many inputs, nitrogen fertilizers are the main yield-limiting factor in agriculture. Liquid fractions of digestates can be a most promising substitute to synthetic nitrogen fertilizers, using little energy to turn waste into valuable fertilizers. In this study, the efficacy of five digestates from different origin (C, cow slurry; P, pig slurry; PCE, pig slurry, cow slurry, energy crops; SS, sewage sludge; W, organic fraction of municipal waste) were assessed as fertilizers for the cultivation of Lactuca sativa L., compared to traditional mineral fertilization. Digestates showed promising results as fertilizers for Lactuca sativa L., as yield and chemical parameters were overall comparable to the mineral fertilizer. Analysis of nitrogen evolution showed that most digestates showed higher nitrates in the substrates than the mineral fertilizers at earlier stages. Another topic investigated in the study is the effect of the digestates on the bacterial populations of the growth substrate, investigated through quantification and sequencing of 16S gene. These results varied based on the digestate considered, but, in general, an increase in biodiversity could be linked to use of digestates. These results suggest that digestates might become an alternative to mineral fertilizers, contributing to the circular economy and waste reduction.

Biorefineries aim to maximise resource recovery from organic sources that have been traditionally considered wastes. In this respect, leftovers from mollusc and seafood processing industries can be a source of multiple bioproducts such as protein hydrolysates (PH), calcium carbonate and co-composted biochar (COMBI). This study aims to evaluate different scenarios of biorefineries fed by mollusc (MW) and fish wastes (FW) to understand which is the most convenient to maximise their profitability. Results showed that the FW-based biorefinery obtained the highest revenues with respect to the amounts of waste treated, i.e., 955.1 €·t-1 and payback period (2.9 years). However, including MW in the biorefinery showed to increase total income as a higher amount of feedstock could be supplied to the system. The profitability of the biorefineries was mainly dependent on the selling price of hydrolysates (considered as 2 €·kg-1 in this study). However, it also entailed the highest operating costs (72.5-83.8% of total OPEX). This highlights the importance of producing high-quality PH in economic and sustainable way to increase the feasibility of the biorefinery.

Highly stabilized digestate from sewage sludge and digestate-derived ammonium sulphate (RFs), were used in a comparison with synthetic mineral fertilizers (SF) to crop maize in a three-year plot trial in open fields. RFs and SF were dosed to ensure the same amount of mineral N (ammonia-N). In doing so, plots fertilized with digestate received much more N (+185 kg ha-1 of organic N) because digestate also contained organic N. The fate of nitrogen was studied by measuring mineral and organic N in soil at different depths, ammonia and N2O emissions, and N uptake in crops. Soil analyses indicated that at one-meter depth there was no significant difference in nitrate content between RF, SF and Unfertilized plots during crop season indicating that more N dosed with digestate did not lead to extra nitrate leaching. Ammonia emissions and N content in plants and grains measured were also similar for both RF and SF. Measuring denitrification activity by using gene makers resulted in a higher denitrification activity for RF than SF. Nevertheless, N2O measurements showed that SF emitted more N2O than RF (although it was not statistically different) (7.59 ± 3.2 kgN ha-1 for RF and 10.3 ± 6.8 kgN ha-1 for SF), suggesting that probably the addition of organic matter with digestate to RF, increased the denitrification efficiency so that N2 production was favoured. Soil analyses, although were not able detecting N differences between SF and Rf after three years of cropping, revealed a statistical increasing of total carbon, suggesting that dosing digestate lead to carbon (and maybe N) accumulation in soil. Data seem to suggest that N2O/N2 emission and organic N accumulation in soil can explain the fate of the extra N dosed (organic-N) in RF plots.

In this study, hydrochar (HC), a carbon-rich product originated from hydrothermal conversion treatment (HTC), was obtained from wastes of the wine and dairy industries. The effect of mixing secondary char and compost was tested, before and after the aerobic mixing of compost (COM) and HC at increasing doses (from 15 to 75 Mg ha−1 DM), in an effort to lower the HC phytotoxicity due to potential phytotoxic compounds of secondary char. The results indicated that, after the aerobic stabilization, the mix HC/COM was able to double the plant growth in comparison to COM alone. The presence of easily degradable organic compounds probably led to poor stability of HC, increased microbial activity and, consequently, root anoxia when used at high doses. Chemical, spectroscopic and thermal investigation confirmed this hypothesis. In particular, HC shows a high content of dissolved organic matter, characterized by the presence of small molecules, which is negatively correlated with the growth index of lettuce. Furthermore, thermal characterization suggests a higher proportion of less complex and thermally stable molecular compounds in HC in comparison to COM. Therefore, co-composting of HC allows obtaining a useful amendment to support soil organic matter and fertility.

The permanence of a buried body in soil always induces the formation of a decomposition island that can serve as a significant recording location to understand how the persistence of a clandestine grave affects soil. This study aims to analyze the elemental exchange from buried bodies to soil, with a focus on phosphorus content, and to determine the effects of environmental factors on its persistency. The experiment was carried out using eleven swine carcasses buried in an open site (northern Italy). The analyses were performed using the Olsen P method, which allowed for a recognition of the trend of the amount of phosphorus over time, due to the decomposition of phospholipids, followed by the transfer of the element from bone to soil. Additionally, microanalyses performed using a scanning electron microscope (SEM-EDS) on two different soil sample specimens (i.e., “dust” and “plug”) allowed for the identification of numerous phosphatic features (i.e., coatings, infillings, impregnations, and organo-mineral associations), which are the result of the interaction between soil and body fluids and can thus be used as indicators of the former presence of decomposing body (even in its absence). The ultramicroscopic analysis also shows increasing and decreasing amounts of P2O5 over time in the soil, which could be related to environmental conditions (i.e., soil moisture), due to the leaching of phosphorus induced by the percolation of natural rainwater. The study underlines the potential use of these methods to evaluate the possibility of a cadaver‒soil linkage and of assessing the burial in the soil for a variable period. Moreover, the study may aid in analyzing the dynamics of phosphorus migration from buried bodies to soil during and after the decomposition process.