Effects of irrigation on n2o emissions in a maize crop grown on different soil types in two contrasting seasons

Crop management and soil properties affect greenhouse gas (GHG) emissions from cropping systems. Irrigation is one of the agronomical management practices that deeply affects soil nitrous oxide (N2O) emissions. Careful management of irrigation, also concerning to soil type, might mitigate the emissions of this powerful GHG from agricultural soils. In the Mediterranean area, despite the relevance of the agricultural sector to the overall economy and sustainable development, the topic of N2O emissions does not have the same importance as N2O fluxes in temperate agricultural areas. Only some research has discussed N2O emissions from Mediterranean cropping systems. Therefore, in this study, N2O emissions from different soil types (sandy‐loam and clay soils) were analyzed in relation to the irrigation of a maize crop grown in two contrasting seasons (2009–2010). The irrigation was done using a center pivot irrigation system about twice a week. The N2O emissions were monitored throughout the two‐years of maize crop growth. The emissions were measured with the accumulation technique using eight static chambers (four chambers per site). Nitrogen fertilizer was applied in the form of ammonium sulphate and urea with 3,4 dimethylpyrazole phosphate (DMPP) nitrification inhibitors. In 2009, the N2O emissions and crop biomass measured in both soil types were lower than those measured in 2010. This situation was a lower amount of water and nitrogen (N) available to the crop. In 2010, the N2O fluxes were higher in the clay site than those in the sandy‐loam site after the first fertilization, whereas an opposite trend was found after the second fertilization. The soil temperature, N content, and soil humidity were the main drivers for N2O emission during 2009, whereas during 2010, only the N content and soil humidity affected the nitrous oxide emissions. The research has demonstrated that crop water management deeply affects soil N2O emissions, acting differently for denitrification and nitrification. The soil properties affect N2O emission by influencing the microclimate conditions in the root zone, conditioning the N2O production

Fertilizer type influences tomato yield and soil N2O emissions

Improvements in crop management for a more sustainable agriculture are fundamental to reduce environmental impacts of cropland and to mitigate effects on global climate change. In this study three fertilization types – ammonium nitrate (control); mineral fertilizer added with a nitrification inhibitor (3,4-dimethylpyrazole phosphate (DMPP)), and an organo-mineral fertilizer (OM) – were tested on a tomato crop in order to evaluate effects both on crop production and soil N2O emissions. Plants grown under OM fertilization had a greater relative growth rate compared to mineral fertilization, due to a higher net assimilation rate, which was related to a greater light interception rather than to a higher photosynthetic efficiency. OM fertilization determined the highest fruit production and lower soil N2O fluxes compared to NH4NO3, although the lowest soil N2O fluxes were found in response to mineral fertilizer added with a nitrification inhibitor. It can be concluded that organo-mineral fertilizer is a better nutrient source compared to mineral fertilizers able to improve crop yield and to mitigate soil N2O emission

ISO-LWS study of pre-main sequence sources

We present the results obtained with the ISO Long Wavelength Spectrometer on a sample of Pre-MS sources, where several molecular lines of CO, H2O and OH have been detected. The analysis of the CO lines indicates that gas temperatures as low as 200 K are consistent with the data. This would be in agreement with the relatively low abundance of water in the gas phase measured in most of the objects

ISO observations of the HH 24-26 regions

We report the results of an investigation, performed with the Long Wavelength Spectrometer (LWS) and the Short Wavelength Spectrometer (SWS) on-board the ISO satellite, on the star forming region associated with the Herbig-Haro objects HH24-25 and 26. In particular, we obtained low-resolution LWS spectra towards the two Class 0 sources HH24MMS and HH25MMS as well as towards the Class I source HH26IR and its associated flow. In addition, SWS scans of pure H2 rotational lines in HH24MMS where acquired. All the spectra present the [OI] 63 μm and the [CII] 158 μm lines, while significant molecular emission from CO and H2O is detected only from HH25MMS and along the blue lobe of the HH26IR outflow, where the shocked activity is also evidenced by the presence of strong near infrared knots. The physical conditions of the regions strongly emitting in molecular lines are derived, showing that the two Class 0 sources are characterised by lower temperatures and higher densities than the HH26IR flow. The presence of both J and C shocks are envisaged to take into account the observed emission

An investigation of the B335 region through far infrared spectroscopy with ISO

We present far infrared spectra of the B335 dark cloud region, obtained with the Long Wavelength Spectrometer (LWS) on-board the ISO satellite. Deep spectra were obtained towards the far infrared outflow exciting source, located in the B335 core, and on the three associated Herbig Haro (HH) objects HH119 A, B and C. In addition, a region of about 9' in RA and 4' in Dec. was mapped which covers the whole molecular outflow. [CII]158 μm emission was found to be uniformly distributed across the observed region, with the intensity expected for a photodissociation region excited by the average interstellar field. The [OI]63 μm emission was detected only towards two out of the three HH objects and from the B335 FIR source; excitation from the high-velocity shocks responsible for the HH119 knots can account for the observed line intensity. CO line emission from the rotational levels J=15 to J=18 was detected only towards B335 FIR and can be modelled as arising in warm gas whose excitation temperature is in the range 150-800 K, located in a compact ( ~ 10-3 pc) and dense (nH2 ~ 106 cm-3 ) region. If we assume that the CO J = 6→5 line observed from the ground is also emitted from the same gas component, we derive for this component a temperature of 350 K and a density of 5•105 cm-3. Current collapse models for the B335 core fail to predict the presence of such warm gas in the infalling source envelope, at the spatial scales implied by our model fit. It is likely that the molecular emission is excited in a low-velocity (v ~ 10 km s-1 ) non-dissociative shock, originating at the base of the flow

URBAN CENTER. Una casa di vetro per le politiche urbane.

Nella cultura di governo della città, il termine "Urban Center" (o "Casa della città") designa una serie di strutture il cui denominatore comune risiede nello svolgimento di attività di servizio per le comunità urbane ai fini di soddisfare la crescente domenda di democrazia partecipativa e deliberativa nei processi di trasformazione degli insediamenti. Traendo spunto dalla storicizzazione del fenomeno e dal confronto tra i consolidati modelli statunitensi e le recenti esperienze in Italia, il volume si interroga sulla maturazione delle missioni dell' "Urban Center" nel passaggio da asettico spazio di informazione a luogo provilegiato per la costruzione trasparente di politiche urbane condivise. Il percorso logico del volume si sviluppa seguendo un fil rouge articolato in quattro parti. Il primo blocco si apre con due tematiche che costituiscono dialetticamente la cornice di riferimento entro cui può essere correttamente collocata la questione degli UC: l’urbanistica partecipata e il marketing urbano. Nella seconda parte attraverso lo studio di casi si ricostruisce il quadro delle articolate declinazioni statunitensi di Urban Center, consolidatesi in diversi decenni di storia. Sono strutture fortemente caratterizzate e autonome per stile, missioni, obiettivi, priorità, modalità operative, ma allo stesso tempo accomunate da un equilibrato mix di passione civile e pragmatismo professionale. Il terzo gruppo di saggi è dedicato alla condizione attuale e di prospettiva degli UC in Italia, delineando criticamente una sorta di “mappa dinamica” delle diverse strutture attivate e in divenire, caratterizzate per soggetti ispiratori, missioni “stili” e protagonismo degli attori coinvolti. Il cerchio delle riflessioni si chiude nella quarta parte discutendo la questione dell’innovazione di metodo per la costruzione di un UC sia attraverso la dimensione teoretica che le potenzialità operative. Testi in italiano e inglese di B. Monardo (curatore), M.C. Bizzarri, E. Carmagnani, M. Carta, F. Ceci, P. Colarossi, L. De Bonis, A. Dina, A. De Rossi, D. Filippi, A. Giorgi, P. Laconte, F. Lovato, L. J. Osmond, R. Shiffman, O Tommasi, A. Uttaro; postfazione di M. Ricci

ISO-LWS observations of Herbig Ae/Be stars. II. Molecular lines

We present the first ISO-LWS observations of the molecular FIR lines in 3 out of a sample of 11 Herbig Ae/Be stars (HAEBE), namely IRAS12496-7650, RCrA and LkHα 234. High-J rotational CO lines (from Jup = 14 to Jup = 19) have been observed in all the spectra, while two (at 79 μm and 84 μm) and three OH lines (at 71 μm, 79 μm and 84 μm) were detected in LkHα 234 and RCrA respectively. For all sources the molecular emission has been consistently fitted with a Large Velocity Gradient (LVG) model and it results originated in a warm (T ≳ 200 K) and dense (nH2 ≳ 105 cm-3) gas located in very compact regions having diameters of few hundreds of AU. These three sources are those with the highest density among the stars of the sample; this suggests that the molecular emission arises in regions showing density peaks. By comparing the observed cooling ratios with model predictions, we find that the FUV radiation from the central source (or from a more embedded companion) is the most likely responsible for the line excitation. At least for the sources where OH has been observed, the contribution of shocks to the line emission can be reasonably ruled out because of the absence in the spectra of any water vapour lines, in contrast with the predictions for molecular emission coming from warm shocked environments

ISO-LWS observations of Herbig Ae/Be stars. I. Fine structure lines

We present the results of the first spectrophotometric survey of a sample of eleven Herbig Ae/Be stars (HAEBE) obtained with the Long Wavelength Spectrometer (LWS) on board the Infrared Space Observatory (ISO). The [OI] 63μm and the [CII] 158μm lines are observed in all the investigated sources, while the [OI] 145μm transition, due to its relative faintness, sometimes remains undetected. By comparing line intensity ratios with model predictions, photodissociation, due to the UV photons from the central star, results the dominating excitation mechanism although contributions of C-shocks to the [OI] emission cannot be ruled out. A clear example for the presence of a photodissociation region (PDR) illuminated by an HAEBE is shown by LWS spectroscopic mapping of NGC 7129. Some diagnostic probes of the radiation field and density are provided for the objects in our sample: these substantially agree with the known characteristics of both the star and its circumstellar environment, although the observed ratio [OI]63/[OI]145 tends to be smaller than predicted by PDR models. The most likely explanation for this behaviour is self-absorption at 63μm by cold atomic oxygen. Fine structure lines of the ionised species [OIII], [NII] were detected whenever the star had a spectral type of B0 or earlier; in particular, around the star CoD-42° 11721, besides a compact HII region, evidence is given for an extended low electron density ionised region. Finally, molecular line emission is associated with stars powering a CO outflow, and clumpy PDR models, better than C-shock models, predict for them relative cooling (CO vs OI and CO vs OH) similar to the observed ones

ISO-LWS two colour diagram of young stellar objects

We present a [60--100] vs. [100--170] $\mu$m two colour diagram for a sample of 61 young stellar objects (YSOs) observed with the Long Wavelength Spectrometer (LWS) on-board the Infrared Space Observatory (ISO). The sample consists of 17 Class 0 sources, 15 Class I, 9 Bright Class I ($L_{\rm bol}>10^4 L_\odot$), 20 Class II (14 Herbig Ae/Be stars and 6 T Tauri stars). We find that each class occupies a well defined region in our diagram with colour temperatures increasing from Class 0 to Class II. Therefore the [60--100] vs. [100--170] two colours diagram is a powerful and simple tool to derive from future (e.g. with the Herschel Space Observatory) photometric surveys the evolutionary status of YSOs. The advantage over other tools already developed is that photometry at other wavelengths is not required: three flux measurements are enough to derive the evolutionary status of a source. As an example we use the colours of the YSO IRAS 18148$-$0440 to classify it as Class I. The main limitation of this work is the low spatial resolution of the LWS which, for some objects, causes a high uncertainty in the measured fluxes due to the background emission or to the source confusion inside the LWS beam.Comment: 7 pages, 2 figures, requires mn2e document class. Accepted by MNRA