InterVeg

Enhancing multifunctional benefits of cover crops –vegetables intercropping

Régionalisation des modules annuels et des régimes d'étiage du bassin hydrographique de la Moselle française : lien entre modèles régionaux

Les modélisations régionales proposées sur les modules annuels et les débits moyens d'étiage des sous-bassins de la Moselle française devraient contribuer à l'amélioration des connaissances sur le fonctionnement physique actuel des hydrosystèmes. Elles s'inscrivent dans le contexte des directives de la loi Pêche et de la loi sur l'Eau et plus récemment de la Directive Cadre Européenne. Quarante neuf sous-bassins répartis en trois jeux ont permis de caler et valider un modèle régional des modules annuels et un modèle régional d'étiage. Dans le cas du bassin hydrographique de la Moselle française une certaine dépendance existe entre modèles régionaux dont la loi statistique choisie est la loi de Weibull à 2 paramètres. Une pseudo-dépendance est observée entre la loi régionale des modules annuels et la loi régionale des débits moyens d'étiage pour les années moyennes à sèches. Cette propriété va permettre en particulier l'usage d'une procédure simplifiée commune, établie à partir de la connaissance de jaugeages épisodiques d'étiage, pour l'estimation des descripteurs de débit d'un sous-bassin non observé : le module médian /qa et le débit quotidien minimal médian /vcnd=1. Pour le modèle régional d'étiage un deuxième descripteur local est nécessaire. Il s'agit d'un temps caractéristique d'étiage du sous-bassin ∆e (j) permettant de généraliser le modèle à toute durée d. Le concept débit-durée-fréquence QdF appliqué aux étiages exploite la convergence observée des distributions de différentes durées d et est indépendant de la loi fréquentielle choisie. Le caractère opérationnel de ces modélisations régionales dépend essentiellement de la précision d'estimation des descripteurs de débit du sous-bassin étudié /qa, pour les modules annuels et /vcnd=1 pour les étiages. Ces descripteurs de débit ont été estimés selon deux approches : l'approche classique par régression multiple et selon une approche simple de recherche d'un coefficient de tendance k entre jaugeages épisodiques d'étiage concomitants au sous-bassin étudié (pas ou peu d'observations) et au sous-bassin de référence (chronique de débit continue). Pour cela, un choix de cinq jaugeages d'étiage par an sur les douze dernières années en moyenne a été fait. Le descripteur de débit du sous-bassin étudié est ensuite déduit du produit de k par le descripteur de débit du sous-bassin de référence. Pour /vcnd=1, sb. étudié nous observons dans la majorité des cas une nette amélioration de l'estimation obtenue par régression, notamment une forte réduction des écarts les plus importants. Une similitude des classes de superficie entre sous-bassin étudié et sous-bassin de référence n'est pas exigée. La proximité géographique des sous-bassins semble donner de meilleurs résultats. En ce qui concerne le module médian /qasb. étudié, son estimation par régression multiple est assez performante. Parallèlement à cela, le coefficient k de tendance permet, de même que pour, une estimation cohérente de /qasb. étudié. Ce résultat un peu inattendu laisse supposer que la pseudo-dépendance observée entre modèles régionaux a bien une réalité physique. Nous avons insisté sur cette démarche "de régionalisation" nécessitant un faible investissement en mesures de débit des sous-bassins non observés par rapport au réseau national de suivi hydrométrique. Elle se présente à notre avis comme une alternative (ou complémentarité) intéressante aux méthodes de régionalisation à bases géostatistiques : telles que l'identification du voisinage hydrologique homogène du sous-bassin étudié ou encore la prise en compte de l'effet structurant du réseau hydrographique dans la cartographie du descripteur de débit. L'ensemble des connaissances relative à cette recherche est repris dans un Système d'Information Géographique pour répondre éventuellement à la demande.Regional modelling of the annual mean discharge and average low-flow discharge of the French Moselle sub-basins should improve our knowledge of its hydrosystem functioning. These models are part of the directives of the Water Act and Fishery Act and more recently of the European Framework Directive. Forty-nine sub-basins divided into three groups were used to calibrate and validate a regional model of the annual mean discharge and a regional model of low-flow discharge.A two-parameter Weibull distribution was used to represent the regional models of the Moselle catchment. Results show a relative dependence between the regional models. A pseudo-dependence was observed between the regional annual mean discharge model and the regional average low-flow discharge model for the average years to the dry ones. This property allowed us to use a common simplified procedure, established from the low-flow episodic discharge measurements, to estimate the flow descriptors of an ungauged sub-basin, namely the median annual mean discharge /qa and the median minimal daily low-flow discharge /vcnd=1. For the low-flow regional model a second local descriptor was necessary, the characteristic time of low-flow discharges of the sub-basin ∆e (j), which allowed us to generalize the model for every duration (d). The QdF flow-duration-frequency concept, applied to the low-flow discharge, is independent of the selected frequency law and uses the observed convergence of the distributions of various durations (d). The operational character of these regional models depends strongly on the accuracy of the estimation of the flow descriptors of the studied sub-basin (/qa for the annual mean discharges and /vcnd=1 for the low-flow discharges). These flow descriptors were estimated according to two approaches: a traditional approach based on multiple regression and a simple approach based on a trend coefficient (k) calculated between low-flow episodic discharge measurements that are concomitant between the studied sub-basin (no or few observations) and the reference sub-basin (time series of continuous discharges). A choice of five low flow discharge measurements per year over the last twelve years (on average) was made. Knowing the flow descriptor of the reference sub-basin, the flow descriptor of the studied sub-basin was then deduced from the trend coefficient k. For /vcnd=1, sb. étudié we observe in the majority of cases a significant improvement of the estimation obtained by regression, especially a net reduction of the most important variations. A similarity of the surface classes between the studied sub-basin and the reference sub-basin is not required. Geographical proximity of the sub-basins seems to provide better results. The estimation of the median annual mean discharges /qasb. étudié using multiple regression was rather impressive. In addition, the trend coefficient k established for the low-flow discharges allowed a coherent estimation of /vcnd=1, sb. étudié and /qasb. étudié. This quite unexpected result suggests that the observed pseudo-dependence between regional models has a physical reality.The "regionalization" technique detailed herein does not require a significant investment in flow measurements of the ungauged sub-basin compared to the national hydrometric network. It is an interesting (or complementary) alternative to the regionalization approach based on geostatistical methods that, for instance, identify the homogeneous hydrological vicinity of each sub-basin or take into account the structuring effect of the hydrographic network in the cartography of the flow descriptor

Effects of long term application of compost and poultry manure on soil quality of citrus orchards in Southern Italy.

A six-year study was carried out in an organically managed orange orchard located in Sicily (Southern Italy) to assess the effect of compost and organic fertilizers utilisation on soil quality. Adopting a randomized-block experimental design with three replicates, four treatments were carried out. In treatments 1 and 2, two different composts (C1 from distillery by products and C2 from livestock wastes) were applied. The plots of treatment 3 were fertilized using dried poultry manure. The control treatment was fertilized with mineral/synthetic fertilizers. In order to verify the hypothesis that composts and organic fertilizers improve soil fertility, soil quality was evaluated by selecting dynamic soil parameters, as indicators linked to C and N cycles. Total organic C, total N, C/N ratio, humified fraction, isoelectric focusing (IEF) of extracted organic matter, microbial biomass C, potentially mineralisable N under anaerobic conditions, potenzially mineralizable C, C mineralization quotient and metabolic quotient were determined for each sample. Furthermore, the Comunity level Physiological Profile (by Biolog tecnique) was defined, calculating derived functional biodiversity and versatility indexes. Parameters related to IEF and potentially mineralizable C showed significant differences among the treatments. Moreover, total C, total N and humification parameters tended to increase, while no differences were observed in biodiversity indexes. On these findings, it was concluded that composts and poultry manure only weakly affected soil properties, though they increased soil nutritive elements potentially available to crops

Large Magnetoresistance in Co/Ni/Co Ferromagnetic Single Electron Transistors

We report on magnetotransport investigations of nano-scaled ferromagnetic Co/Ni/Co single electron transistors. As a result of reduced size, the devices exhibit single electron transistor characteristics at 4.2K. Magnetotransport measurements carried out at 1.8K reveal tunneling magnetoresistance (TMR) traces with negative coercive fields, which we interpret in terms of a switching mechanism driven by the shape anisotropy of the central wire-like Ni island. A large TMR of about 18% is observed within a finite source-drain bias regime. The TMR decreases rapidly with increasing bias, which we tentatively attribute to excitation of magnons in the central island.Comment: 12 pages (including 4 figures). Accepted for publishing on AP

Enhancing multifunctional benefits of living mulch in organic vegetable cropping systems

Over the last several decades, agriculture in industrialized countries experienced a significant intensification as a result of the diffusion of mechanization, the widespread use of genetically improved genotypes, and the large-scale use of off-farm inputs, mainly in the form of fossil fuel energy and synthetic fertilizers and pesticides. Under the pressure of the growing agro-industrial sector, which has been oriented to promote models based on large volumes and long-distance supply chains, intensification was accompanied by progressive specialization of farms and cropping systems (Ratnadass et al., 2012). Indeed, the reduction of diversity at the field, farm, and territory level, a result of a low number of crops, the shortening of crop rotations, and a decrease in the number of cultivated genotypes, is becoming evident in many agro-environments in developed countries

Antimony doping of Si layers grown by solid-phase epitaxy

We report here that layers of Si formed by solid-phase epitaxial growth (SPEG) can be doped intentionally. The sample consists initially of an upper layer of amorphous Si (~1 µm thick), a very thin intermediate layer of Sb (nominally 5 Å), and a thin lower layer of Pd (~500 Å), all electron-gun deposited on top of a single-crystal substrate (1–10 Ω cm, p type, orientation). After a heating cycle which induces epitaxial growth, electrically active Sb atoms are incorporated into the SPEG layer, as shown by the following facts: (a) the SPEG layer forms a p-n junction against the p-type substrate, (b) the Hall effect indicates strong n-type conduction of the layer, and (c) Auger electron spectra reveal the presence of Sb in the layer

Avoidance distance test in goats: a comparison with its application in cows

The present study investigates the feasibility in goats of an avoidance distance (AD) behaviour test set-up for cattle, and compares the results in the two species to assess the suitability of the test for on-farm welfare evaluation in goat farms. The tests were performed on 324 lactating cows (170 in small farms and 154 in large farms) and 271 lactating goats (108 in small farms and 163 in large farms), housed in free stall farms (12 dairy cattle and 17 dairy goat farms) in the Province of Sondrio, Northern Italy, following a protocol validated for dairy cows in the Welfare Quality\uae project. After the assessors were adequately trained, this test was relatively easy to perform and no major difficulties were faced in either species. Goats exhibited a higher level of confidence with humans, as showed by lower AD (goats: 68.60 \ub1 4.98 cm; cows: 71.36 \ub1 4.37 cm; p < 0.10) and higher frequency of contacts (AD = 0) (goats: 45.8%; cows: 31.2%; p < 0.001). Farm size significantly affected AD values (lower in small farms) and frequency of contacts (higher in small farms) in goats, but not in cows. This was probably due to the less marked management difference between large and small farms of cattle than those of goats. The AD test seems feasible in goats; however, the experimenter contacted nearly half of the goats. To improve the sensitivity, a further level - represented by the possibility of gently stroking the goat's head after the contact - may be included in the test in addition to contact

Where is the spectral weight in magnetic neutron scattering in the cuprates?

We present estimates in the Hubbard and Heisenberg models for the spectral weight in magnetic neutron scattering experiments on the cuprates. With the aid of spin-wave theory and the time dependent Gutzwiller approximation we discuss how the spectral weight is distributed among the different channels and between high and low energies. In addition to the well known total moment sum rule we discuss sum rules for each component of the dynamical structure factor tensor which are peculiar for spin 1/2 systems. The various factors that reduce the spectral weight at the relevant energies are singled out and analyzed like: shielding factors, weight at electronic energies, multimagnon process etc. Although about 10% ~ 15% of the naively expected weight is detected in experiments after consideration of these factors the missing weight is within the experimental uncertainties. A large fraction of the spectral weight is hard to detect with present experimental conditions.Comment: 16 pages, 13 figures, submitted to PR

Spectral properties of a generalized chGUE

We consider a generalized chiral Gaussian Unitary Ensemble (chGUE) based on a weak confining potential. We study the spectral correlations close to the origin in the thermodynamic limit. We show that for eigenvalues separated up to the mean level spacing the spectral correlations coincide with those of chGUE. Beyond this point, the spectrum is described by an oscillating number variance centered around a constant value. We argue that the origin of such a rigid spectrum is due to the breakdown of the translational invariance of the spectral kernel in the bulk of the spectrum. Finally, we compare our results with the ones obtained from a critical chGUE recently reported in the literature. We conclude that our generalized chGUE does not belong to the same class of universality as the above mentioned model.Comment: 12 pages, 3 figure