STRATEGIES TO INCREASE WATER PRODUCTIVITY IN IRRIGATED RICE SYSTEMS: IS REDUCING WATER INPUTS THE KEY?

La crescita della domanda mondiale di cibo e l\u2019aumentata incidenza di situazioni di carenza idrica ha notevolmente accentuato l\u2019attenzione sulla risicoltura, data la sua importanza per la nutrizione umana e il suo contributo ai prelievi idrici per fini irrigui. Pi\uf9 del 75% della produzione mondiale di riso ha infatti luogo in risaie irrigate che utilizzano circa il 40% dell\u2019acqua destinata al settore agricolo. Alla luce di questo contesto (descritto nel Capitolo 1), la Tesi si pone l\u2019obiettivo di valutare diverse tecniche di gestione dell\u2019acqua in risaia come risposta alle crescenti pressioni sugli agricoltori che sono chiamati a massimizzare le produzioni, riducendo al contempo i volumi irrigui apportati. Il lavoro \ue8 articolato su tre principali aree di indagine tra loro interconnesse: (i) ruolo delle tecniche di monitoraggio nel favorire l\u2019analisi dei fattori che determinano l\u2019efficienza d\u2019uso dell\u2019acqua; (ii) valutazione di diverse strategie irrigue alla scala di risaia; (iii) studio delle variazioni dei fabbisogni irrigui distrettuali laddove la sommersione tradizionale fosse sostituita da tecniche di risparmio idrico su larga scala. Per quanto concerne il primo punto, l\u2019attivit\ue0 di Tesi ha contribuito allo sviluppo del prototipo di un innovativo sistema per il monitoraggio delle dinamiche dell\u2019acqua in camere di risaia soggette a diverse tecniche irrigue. Svariati sensori sono stati utilizzati in maniera integrata permettendo la misura di diversi processi con alta risoluzione temporale (Capitolo 2). In aggiunta alle tecniche di monitoraggio a terra, \ue8 stata valutata la possibilit\ue0 di impiego di dati da satellite per la valutazione dello sviluppo della vegetazione nel tempo e nello spazio, informazione necessaria per lo studio di processi legati allo sviluppo vegetativo (Capitolo 3). Alla scala di campo sono stati valutati i bilanci idrici e gli indici di uso dell\u2019acqua di tre diverse tecniche di gestione: semina in acqua e sommersione continua (pratica tradizionale), e due tecniche alternative che consistono nella semina interrata e sommersione ritardata e semina interrata e irrigazione intermittente. Se, da un alto, la sommersione ritardata ha determinato riduzioni del raccolto del 3% a fronte di risparmi idrici del 20%, l\u2019irrigazione intermittente ha visto riduzioni del raccolto pari a circa il 30% come contraltare a risparmi idrici dell\u2019ordine del 65%. I valori pi\uf9 alti per quanto riguarda l\u2019indice di produttivit\ue0 dell\u2019acqua sono stati ottenuti con riso irrigato ad intermittenza, tuttavia la sua sostenibilit\ue0 economica sarebbe da valutare attentamente, date le significative perdite di raccolto osservate. Inoltre, \ue8 stata riscontrata una significativa variabilit\ue0 nei fabbisogni irrigui dei trattamenti in sommersione, i quali hanno subito variazioni comprese tra il 40% e il 50% da un anno al successivo (variazione concentrate soprattutto all\u2019inizio della stagione). Prendendo come riferimento la sommersione tradizionale, si \ue8 riscontrato un dimezzamento dei volumi irrigui necessari che sono passati da circa 3000 mm a 1500 mm. Tali variazioni sono state avvalorate da un\u2019analisi statistica e sono state attribuite alla combinazione di diversi fattori quali la profondit\ue0 di falda all\u2019inizio della stagione e modificazioni a livello delle propriet\ue0 e della struttura del suolo. Successivamente, il potenziale risparmio idrico conseguente ad un abbandono della tecnica di sommersione \ue8 stato valutato alla scala di distretto irriguo (Capitolo 5). I fabbisogni irrigui delle diverse colture del distretto (riso sommerso, mais irriguo e pioppo irriguo) sono stati stimati lungo un periodo di 4 anni grazie all\u2019applicazione, in maniera distribuita, del modello idrologico SWAP e all\u2019uso di equazioni di bilancio di massa. Successivamente, \ue8 stata individuata una relazione empirica che lega la soggiacenza alla ricarica di falda (data dall\u2019acqua di percolazione dei campi irrigati). Per lo scenario di conversione a riso irrigato, si \ue8 prestata particolare attenzione al meccanismo di feedback che lega il livello di falda ai volumi irrigui necessari. L\u2019importanza di questo legame \ue8 stata messa in luce attraverso lo sviluppo di due casi di studio. Nel primo caso, il feedback \ue8 stato trascurato e la stima dei fabbisogni irrigui \ue8 fatta sulla base degli attuali livelli di falda. Nel secondo caso invece, la stima devi volumi irrigui necessari \ue8 fatta in funzione dall\u2019equilibrio soggiacenza-ricarica che verrebbe ad instaurarsi a seguito di una consistente variazione delle pratiche irrigue. Nello scenario senza feedback sono state stimate riduzioni dei fabbisogni irrigui dopo una conversione delle tecniche irrigue pari al 65%. Tali riduzioni sono state invece del 45% quando il meccanismo di feedback \ue8 stato considerato nell\u2019analisi. Tuttavia il mantenimento di un turno irriguo per il mais di 15 giorni si \ue8 rivelato non sufficiente per il soddisfacimento dei fabbisogni idrici della coltura a causa dell\u2019aumentata soggiacenza. Accorciare il turno irriguo del mais a 10 giorni ha determinato un\u2019ulteriore riduzione dei risparmi ottenibili con una completa conversione a riso irrigato ad intermittenza (riduzione dei fabbisogni irrigui distrettuali pari al 40%). Oltre ad aspetti strettamente legati ai volumi idrici, sono state inoltre investigate le dinamiche del carbonio organico disciolto in funzione delle diverse tecniche di gestione dell\u2019acqua (Capitolo 6). Lo studio ha evidenziato un legame molto forte tra il ciclo del carbonio organico disciolto e le condizioni riducenti indotte dalla continua saturazione del suolo. Infine \ue8 stato sviluppato un caso di studio per quantificare il ruolo della falda nella riduzione dei fabbisogni irrigui di colture irrigate ad intermittenza come il mais. I risultati hanno evidenziato un contributo della risalita capillare pari a circa il 50% del volume evapotraspirato dalla coltura in aree con bassa soggicanza di falda (Capitolo 7). In conclusione, nonostante la tendenza a voler proporre soluzioni di carattere generale al problema dell\u2019efficienza d\u2019uso dell\u2019acqua in agricoltura, le attivit\ue0 di ricerca proposte nella seguente Tesi hanno messo in luce come sia difficile stabilire se il risparmio idrico sia effettivamente un obiettivo da perseguire in qualsiasi contesto produttivo (Capitolo 8).In a context of increasing food demand and increasing risk of water scarcity, irrigated rice systems are receiving a specific attention because of the role of rice in food nutrition and because of the relevant share of water withdrawals required by rice farming. More than 75% of the global rice supply is in fact produced in lowland irrigated areas, which in turn require around 40% of the global water used for irrigation. Given this background (Chapter 1), the Thesis investigates the role of water management in irrigated rice system, in response to the compelling pressures on farmers to maximise crop production while reducing the amount of water used for irrigation purposes. Three interlinked focus areas have been evaluated: (i) the role of monitoring techniques in improving knowledge on processes driving water use in rice systems, (ii) field-scale evaluation of the performance of different water regimes, (iii) effects induced by a large adoption of water saving technologies on the irrigation requirements at the district scale. First, a prototype of an innovative integrated multi-sensor system was developed in order to monitor water dynamics in paddy fields under different water regimes. Several monitoring devices were effectively used in an combined way, enabling to measure different processes with a high temporal resolution (Chapter 2). In addition to on-ground devices, the opportunity offered by the use of remote sensed data to capture the spatio-temporal evolution of crop growth and study crop-related processes was investigated (Chapter 3). Focussing on the field scale (Chapter 4), water balances and water use indices of three rice water managements were compared: water seeding-continuous flooding (\u201ctraditional\u201d practice) and two alternative regimes being dry seeding-delayed flooding and dry seeding-intermittent irrigation. If delayed flooding determined average yield reductions by 3% against a decrease of water applications by 20%, the 65% reduction of water applications in intermittent irrigated rice was counterbalanced by yield losses close to 30%. Therefore, in spite of intermittent irrigation achieving the highest water productivity, the economic practicality of the method could be questioned. Moreover, the irrigation requirements of the flooded treatments were found to vary significantly between years, with variations by 40% to 50% (mostly occurred in the first part of the season). Taking as a reference the traditional flooding regime, irrigation requirements halved from 3,000 mm in the first season to 1,500 mm in the subsequent one. Variations were statically validated and they were attributed to a combination of abiotic and biotic factors including groundwater levels at the beginning of the season and soil-related aspects. Then, the extent of reductions in irrigation requirements when replacing traditional flooding with intermittent irrigation was investigated at the scale of an irrigation district (Chapter 5). Water requirements of the different crops (flooded rice, irrigated maize and irrigated poplars) were investigated over a 4-year period by the application of a distributed modelling approach (use of the SWAP model) and water balance equations. An empirical relationship between groundwater recharge (provided by percolation from irrigated fields) and the groundwater levels was thus identified. For the scenario of intermittent irrigated rice, a particular attention was paid to the role of the feedback between groundwater levels and irrigation applications. The importance of feedback effects was highlighted by developing a case study where groundwater is assumed invariant from the present state (no feedback) and a case study where the estimated irrigation requirements are congruent with the \u201cnew\u201d equilibrium state between groundwater levels and groundwater recharge. According to the estimates of the scenarios, irrigation withdrawals of the district decreased by around 65% when the feedback mechanism was neglected, while a reduction by 45% was observed when the feedback was accounted for. However, maintaining a 15-days turn for maize irrigation, like in the present state, was found to be inadequate for the full satisfaction of maize water requirements due to the decrease in the groundwater levels. Shortening the irrigation turn of maize to 10 days instead of 15 further decreased the estimate of the savings achievable with flush irrigated rice (reduction of irrigation requirements equal to 40%). In addition to implications on water balance terms, a specific attention was paid on the dynamics of dissolved organic carbon in relation to the water regime. Results of the study highlighted a strong link between the cycling of dissolved organic carbon and the reducing soil conditions resulting from field flooding (Chapter 6). Finally, the role of shallow groundwater table on the reduction of the irrigation requirements of lowland crops under intermittent irrigation was quantified via modelling simulations. Results showed a contribution of capillary rise up to 50% of the amount of water evapotranspirated by the crop (Chapter 7). In spite of the tendency to seek for general and global solutions, the research activities presented in the Thesis highlighted the difficulty to provide a univocal response to the question as to whether reductions of water consumptions in rice paddies should really represent the target to be reached regardless the specific context (Chapter 8)

Spin-dependent direct gap emission in tensile-strained Ge films on Si substrates

The circular polarization of direct gap emission of Ge is studied in optically-excited tensile-strained Ge-on-Si heterostructures as a function of doping and temperature. Owing to the spin-dependent optical selection rules, the radiative recombinations involving strain-split light (cG-LH) and heavy hole (cG-HH) bands are unambiguously resolved. The fundamental cG-LH transition is found to have a low temperature circular polarization degree of about 85% despite an off-resonance excitation of more than 300 meV. By photoluminescence (PL) measurements and tight binding calculations we show that this exceptionally high value is due to the peculiar energy dependence of the optically-induced electron spin population. Finally, our observation of the direct gap doublet clarifies that the light hole contribution, previously considered to be negligible, can dominate the room temperature PL even at low tensile strain values of about 0.2%

Towards an integrated model to explain the factors affecting collaborative innovation processes – insights from the agrifood sector

This study explores the relevant factors to involve multiple actors who develop and implement new technologies to build sustainable agrifood systems. By examining 11 cases, we found that technological, organization, environmental, behavioural and interorganizational factors (all mentioned in current literature) as well as collaborative business models (not mentioned in current literature) affect such initiatives. Based on this, we propose an integrated model. The agrifood sector is one of the first sectors in which a collaborative transition unfolds. As other sectors are likely to undergo similar transitions in the near future, lessons learnt from the agrifood sector can guide these transitions

Spin-coherent dynamics and carrier lifetime in strained Ge1−xSnx semiconductors on silicon

We demonstrate an effective epitaxial route for the manipulation and further enrichment of the intriguing spin-dependent phenomena boasted by germanium. We show optical initialization and readout of spins in Ge-rich germanium-tin alloys and report on spin quantum beats between Zeeman-split levels under an external magnetic field. While heavy Sn atoms can be readily utilized to strengthen the spin-orbit coupling, our experiments reveal robust spin orientation in a wide temperature range and a persistent spin lifetime that noticeably approaches the nanosecond regime at room temperature. In addition, time decay photoluminescence experiments evidence a temperature-induced monotonic decrease of the carrier lifetime, eventually providing crucial insights also into nonradiative recombination mechanisms

Laboratory determination of soil hydraulic conductivity for paddy soils: effects of different soil sample saturation methods

Saturated soil hydraulic conductivity (Ks) is a key factor in predicting vertical percolation fluxes, especially in paddy areas, where the peculiar agricultural practices adopted (especially flooding) lead to the formation of a dense and low permeable layer below the ploughed horizon. The core method, reproducing the Darcy\u2019s experiment over large undisturbed soil samples, is considered the reference method for Ks determination. To prepare soil samples for the analysis, two different soil saturation procedures can be adopted: vessel (AtmSat) and under-vacuum saturation (VacSat). A comparison between Ks values obtained by the core method after applying the two procedures is still missing in the literature, and is presented in this work. Five soil profiles were opened in three paddy fields located close to Pavia (Northern Italy) in the context of the WATPAD project (Fondazione Cariplo, grant n 2014-1260). In particular, five couples (replicates) of large undisturbed soil samples (H 15.0 cm, \uf8 14.6 cm) were collected from the less conductive layer (LCL) of each profile. Ks was determined by the core method after the saturation of soil samples with the two procedures (AtmSat and VacSat). To assess the reliability of the resulting Ks values, vertical percolation fluxes estimated by the Darcy\u2019s law (applied by considering lab-measured Ks) for the three paddy fields were compared to the same fluxes obtained as residual terms in the water balance equation applied to the fields. The main outcomes of the study, probably justified by the peculiar characteristics of the analysed soils (low-permeability layers of paddy soils), are the following: (1) the duration of flux experiments to reach the steady-state flux at which the convergence Ks value is obtained was generally very long (up to 25 days in the case of VacSat); (2) also the time needed to reach an evident trend in the measured flux was often long (even more than 20 hours); (3) AtmSat was found to provide reasonable results only for samples with a higher sand content, while, in case of low Ks, the underestimation was found to be up to 10 fold (probably because of air entrapment); (4) when vacuum was applied slowly, VacSat provided accurate estimations of Ks at the steady-state, while a fast vacuum application may produce a relevant hydraulic gradient within the core that can lead to damaging the sample; (5) when applying VacSat, the initial estimation of Ks was misleading (often more than 10 times higher than the convergence value), which can be explained by changes in the electrical diffuse layer (EDL) due to interactions between pore water and within-aggregate water, and/or to the release of biological gasses due to vacuum conditions; (6) in case of VacSat, pouring water under vacuum (instead of before the vacuum application) increased the time needed to reach the steady-state flux, but allowed a smoother convergence to the final Ks value and an earlier evidence of the trend. Due to the low number of samples analysed, outcomes need to be further investigated by considering a larger number of samples and other soil type

Compression of frailty in adults living with HIV

BACKGROUND: Contemporary HIV care may reduce frailty in older adults living with HIV (OALWH). Objective of the study was to estimate prevalence of frailty at the age of 50 and 75 years, and build a model to quantify the burden of frailty in the year 2030. // METHODS: This study included OALWH attending Modena HIV Metabolic Clinic between 2009 and 2015. Patients are referred from more than 120 HIV clinics well distributed across Italy, therefore being country representative. Our model forecasts the new entries on yearly basis up to 2030. Changes in frailty over a one-year period using a 37-variable frailty index (FI) and death rates were modelled using a validated mathematical algorithm with parameters adjusted to best represent the changes observed at the clinic. In this study, we assessed the number of frailest individuals (defined with a FI > 0.4) at the age of 50 and at the age 75 by calendar year. // RESULTS: In the period 2015–2030 we model that frailest OALWH at age 50 will decrease from 26 to 7%, and at the age of 75 years will increase from 43 to 52%. This implies a shift of the frailty prevalence at an older age. // CONCLUSION: We have presented projections of how the burden of frailty in older adults, living with HIV will change. We project fewer people aged 50+ with severe frailty, most of whom will be older than now. These results suggest a compression of age-related frailty

Automatic speech analysis to early detect functional cognitive decline in elderly population

This study aimed at evaluating whether people with a normal cognitive function can be discriminated from subjects with a mild impairment of cognitive function based on a set of acoustic features derived from spontaneous speech. Voice recordings from 90 Italian subjects (age >65 years; group 1: 47 subjects with MMSE>26; group 2: 43 subjects with 20≤ MMSE ≤26) were collected. Voice samples were processed using a MATLAB-based custom software to derive a broad set of known acoustic features. Linear mixed model analyses were performed to select the features able to significantly distinguish between groups. The selected features (% of unvoiced segments, duration of unvoiced segments, % of voice breaks, speech rate, and duration of syllables), alone or in addition to age and years of education, were used to build a learning-based classifier. The leave-one-out cross validation was used for testing and the classifier accuracy was computed. When the voice features were used alone, an overall classification accuracy of 0.73 was achieved. When age and years of education were additionally used, the overall accuracy increased up to 0.80. These performances were lower than the accuracy of 0.86 found in a recent study. However, in that study the classification was based on several tasks, including more cognitive demanding tasks. Our results are encouraging because acoustic features, derived for the first time only from an ecologic continuous speech task, were able to discriminate people with a normal cognitive function from people with a mild cognitive decline. This study poses the basis for the development of a mobile application performing automatic voice analysis on-the-fly during phone calls, which might potentially support the detection of early signs of functional cognitive decline