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Investigating the effects of SOC on soil structure: three-dimensional visualisation and modelling
Full text linkThe quantification of soil structure is primordial to determine the effects of management
practices on soil environment. Soil structure is influenced by soil organic carbon content
(SOC), which is usually recognised as one of the main indicator of soil fertility as it
improves structure stability. Complex interactions link the soil structure and SOC that
acts as a binding agent promoting aggregation.
Several studies focussed on SOC dynamics and the relationship with soil aggregate
microporosity, which is usually considered as a surrogate of the soil matrix complexity,
neglecting the soil macropores outside aggregates. Therefore, the measures made at
aggregate scale form only a small part of the important and complex properties of soil.
Accordingly, it is important to quantify the effects that SOC exerts both is soil
aggregates and undisturbed cores.
The general aim of this work is to study the effects of different fertilisations (organic,
mineral and mixed) applied to continuous maize by means of a long-term experiment
established in 1962 in north-eastern Italy, analysing both small aggregates (few mm) and
undisturbed soil cores (5 cm diameter, 6 cm length) with innovative three-dimensional
techniques. The thesis is structured in five chapters. The first one is a review of the soil
structure-SOC interactions and innovative three-dimensional methods involved in soil
structure quantification. The second chapter analyses the effects of SOC and its humic
fraction on the mechanisms of aggregate breakdown and improves upon the knowledge
of aggregate structural properties. The third chapter compares and combines mercury
intrusion porosimetry (MIP) and X-ray computer assisted microtomography (micro-CT)
for characterising the soil structure. The fourth chapter analyses the 3D soil structure of
undisturbed soil cores and the effects of SOC. The final chapter presents the general
conclusions of the work.La quantificazione della struttura del suolo è di primaria importanza per determinare gli
effetti di diverse pratiche colturali sul terreno. La struttura è influenzata dal contenuto di
carbonio organico (SOC), il quale è ampiamente identificato come il principale
indicatore della fertilità del suolo, anche grazie alle sua attitudine di migliorarne la
struttura fisica. Le interazioni che legano la struttura al SOC sono complesse e
principalmente legate alla capacità di agire come agente aggregante tra le particelle che
compongono la matrice del suolo.
Molti studi si sono concentrati sulle dinamiche che legano il SOC e la microporosità degli
aggregati (che è riconosciuta come un surrogato della complessa struttura del suolo)
trascurando, in questo modo, la macroporosità, la quale non è individuabile in campioni
di piccole dimensioni. Le misure fatte a scala di aggregato, perciò, ricoprono solo una
parte delle importanti e complesse proprietà di un suolo. Di conseguenza è importante
valutare l’effetto che esercita il SOC sia in piccoli aggregati che in campioni
indisturbati.
L’obiettivo generale di questo lavoro è valutare gli effetti di diversi regimi di fertilizzazione
(organica, minerale e mista) in una prova di lungo periodo, iniziata nel 1962, gestita
secondo una monosuccessione di mais. Sono stati analizzati sia aggregati di piccole
dimensioni (pochi mm), che campioni indisturbati (5 cm di diametro, 6 cm di altezza),
con innovative tecniche tridimensionali. La tesi è strutturata in cinque capitoli: il primo è
una review sulle interazioni struttura del suolo-SOC e sulle tecniche tridimensionali
utilizzate per la quantificazione della struttura. Il secondo capitolo analizza gli effetti del
SOC e delle frazioni umiche sulla stabilità di struttura degli aggregati, individuando
inoltre un nuovo meccanismo, legato alla diversa distribuzione della porosità, finora non
considerato. Il terzo capitolo confronta e combina la porosimetria a intrusione di
mercurio e la microtomografia a raggi X per la caratterizzazione della struttura. Il quarto
capitolo analizza tridimensionalmente la struttura di campioni indisturbati e gli effetti
del SOC sulla struttura stessa. Infine, l’ultimo capitolo riporta le conclusioni generali del
lavoro
A comparison of 2D and 3D approach for quantifying the pore size distribution in soil aggregates
No full textBuilding 3D soil models combining X-ray ct and 3D printing Technology. First applications to a Loamy soil
No full textMunicipal wastewater treatment with Phragmites australis L. and Typha latifolia L. for irrigation reuse. Boron and heavy metals
No full textIn this work, we compared the performance of Phragmites australis and Typha latifolia for depurating primary-treated urban wastewater and evaluated their suitability for irrigation reuse. Macrophytes were planted in two pilot-scale constructed wetland systems (CWs) and monitored during a 2-year experiment (2002–2003). CW efficiency was evaluated in terms of both mass removal and water quality considering boron (B) and the following heavy metals: aluminium (Al), arsenic (As), beryllium (Be) manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), lead (Pb), selenium (Se) and vanadium (V). The accumulation of the elements, both in plant tissues and sandy substrate layer, and their offtake with the macrophyte harvest were also measured. In quantitative terms, the established CW systems showed high removal efficiency for Al (96 %), Cu (91 %), Pb (88 %) and Zn (85 %), while lower efficiencies were observed for Fe (44 %), Co (31 %) and B (40 %). The sediment played a strategic role in the adsorption and accumulation of wastewater pollutants, while plants acted as phytostabilizers since element root concentrations were generally from one to two orders of magnitude higher than those observed in the other parts. The results were less favourable in terms of water quality because the high evapotranspiration counteracted the depuration process by concentrating the elements in the outflow water. Outflow water contained more B (68 %), Mn (196 %) and, in the case of CW managed with Phragmites, also Fe (73 %) than inflow water, breaking the Italian guidelines for irrigation reuse. Integrating solutions to reduce the high evapotranspiration of CWs with more efficient pre-cleaning systems are necessary to obtain better removal efficiencies that reduce the effect of ET on water quality
7-year N and P balance of a Surface Flow Constructed Wetland in advanced stage: a case study in North-Eastern Italy
No full textA Bayesian Belief Network framework to predict SOC stock change: the Veneto region (Italy) case study
No full textCrop yield responses to water table management with different drainage systems in a long term trial
No full textStudy of the effects of long-term organic fertilizations on soil macroporosity using X-ray microtomography
No full textDual-scale micro-CT assessment of soil structure in a long-term fertilization experiment
No full textIn this study we used X-ray microtomography (micro-CT) to evaluate the 3D pore size distribution and morphology of both undisturbed soil cores (5. cm diameter, 6. cm length) and aggregates (sieved at 5-6. mm). Samples were collected in a long-term fertilization experiment, established in 1962 in northeastern Italy, which considers organic (farmyard and liquid manure) and mineral treatments. The aim of the work was to assess the dual-scale effect of soil organic carbon (SOC) to influence the pore network in the range 6.25-2000. μm and to test the sensitivity of morphological features (connectivity, degree of anisotropy, fractal dimension) as indices of soil quality to management practices. Results on pore morphology suggested that connectivity was a sensitive index to differentiate the effects of management practices. Soil structure was multifractal and did not highlight any difference between treatments. Pore size distribution was affected by SOC as it increased the pores >. 560. μm of..
Efficiency of controlled drainage and land drainage system in improving water saving and reducing non-poin source pollution in a five-year trial
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