1,721,071 research outputs found
Pedotransfer functions for estimating soil water retention curve of Sicilian soils
Full text linkPedotransfer functions (PTFs) make use of routinely surveyed soil data to estimate soil properties but their application to soils different from those used for their development can yield inaccurate estimates. This investigation aimed at evaluating the water retention prediction accuracy of eight existing PTFs using a database of 217 Sicilian soils exploring 11 USDA textural classes. PTFs performance was assessed by root mean square differences (RMSD) and average differences (AD) between estimated and measured data. Extended Nonlinear Regression (ENR) technique was adopted to recalibrate or develop four new PTFs and Wind’s evaporation method was applied to validate the effectiveness of the relationships proposed. PTFs evaluation resulted in RMSD and AD values in the range 0.0630–0.0972 and 0.0021–0.0618 cm3 cm–3, respectively. Best and worst performances were obtained respectively by PTF-MI and PTF-ZW. ENR allowed to recalibrate PTF-MI and PTF-ZW with improvements of RMSD (0.0594 and 0.0508 cm3 cm–3) and to develop two relationships that improved RMSD by 75–78% as compared to PTF-MI. The results confirmed the potential of ENR technique in calibrating existing PTFs or developing new ones. Validation conducted with an independent dataset suggested that recalibrated/developed PTFs represent a viable alternative for water retention estimation of Sicilian soils
Testing the hydrodynamic behavior of a loam soil by beerkan infiltration runs with six heights of water pouring
Full text linkInterpreting and simulating rainfall partition into infiltration and surface runoff has to consider that surface soil hydraulic properties, including saturated soil hydraulic conductivity (Ks) and sorptivity (S), could change even at very short temporal scales. Soil deterioration due to water impact can be tested in the field by the multi-height beerkan (MHB) method, that is, by pouring water on the infiltration surface from different heights. Soil hydraulic properties can be estimated coupling the MHB method with the steady version of the Beerkan Estimation of Soil Transfer parameters procedure (BEST-steady). The MHB method with six heights of water pouring (H) in the range 0.03-2 m was applied on a relatively dry loam soil to investigate height of water pouring effects on i) the established infiltration process, and ii) Ks, S, the scale parameter of the water retention curve (hg) and the characteristic microscopic pore radius (m). Higher heights of water pouring generally induced a slowdown of the infiltration process, smaller S, Ks and m values and higher |hg| values. The S, Ks, |hg| and m vs. H relationships were statistically significant but the fitted relationships for S and Ks were stronger than those for |hg| and m, indicating a different sensitivity of the considered parameters to the height of water pouring. Small or negligible soil deterioration was observed for both small (H < 0.25 m) and large (H > 1.5 m) heights. Between these two extremes, the soil deteriorated as H increased, suggesting that the external solicitations were high enough to overcome the resistance of the porous medium but not so high to determine a complete soil alteration. The tested methodology appears promising to determine the effects of water impact on the soil hydrodynamic behavior and it could be applied to perform a soil hydraulic characterization usable for modelling hydrological processes
Effects of maquis clearing on the properties of the soil and on the near-surface hydrological processes in a semi-arid Mediterranean environment
No full textMany hillslopes covered with maquis in the semi-arid Mediterranean environment have been cleared in recent decades. There is little information on what effect this has on the hydrology of the soil. We compared the hydraulic properties of the soil and the subsurface hydrological dynamics on two adjacent sites on a hillslope. One site was covered with maquis, the other with grass. The
grass started to grow some 10 years ago, after the maquis had been cleared and the soil had been ploughed. Our study found that the hydraulic properties and the hydrological dynamics of the maquis and the grassed soil differed greatly. The grassed soil had less organic matter and higher apparent density than did the soil covered in maquis. Moreover, the maquis soil retained more water than the grassed soil in the tension range from saturation to 50 cm of water. Infiltration tests performed in summer and in winter indicated that the field saturated hydraulic conductivity (Kfs) of the maquis soil was higher than that of the grassy soil. However the data showed that the Kfs of the two soils changed with the season. In the maquis soil the Kfs increased from summer to winter. This was assumed to be due to water flowing more efficiently through wet soil. By contrast, in the grassy soil the Kfs decreased from summer to winter. This was because the desiccation cracks closed in the wet soil. As result, the influence of the land use change was clear from the Kfs measurements in winter, but less so from those in the summer. Changes in land use altered the dynamics of the infiltration, subsurface drainage and soil water storage of the soil. The maquis soil profile never saturated completely, and only short-lived, event based perched water tables were observed. By contrast, soil saturation and a shallow water table were observed in the grass covered site throughout the wet season. The differences were assumed to be due to the high canopy interception of the maquis cover, and to the macropores in the grassed soil being destroyed after the maquis had been cleared and the soil ploughed. The results of this work are helpful for predicting the changes in the hydraulic properties of the soil and in the near-surface hydrological processes in similar Mediterranean environments where the natural vegetation has been cleared. These changes must be taken into consideration when developing rainfall-runoff models for flood forecasting and water yield evaluation
Qualità fisica del suolo in un’area ad uso agricolo tradizionale della Sicilia centrale
No full textNella memoria viene valutata la qualità fisica dei suoli di un’area in cui sono
presenti usi del suolo a basso impatto tipici della collina interna siciliana. La
valutazione è stata effettuata utilizzando i tradizionali indici basati sulla curva di
ritenzione idrica, integrati da misure della porosità dinamica effettuate con l’infiltrometro
a depressione. Secondo le classificazioni comunemente adottate, condizioni
di qualità fisica prossime a quelle ottimali si sono riscontrate solamente nel
suolo sottoposto ad avvicendamento colturale e lavorato secondo pratiche tradizionali.
Nel rimboschimento, la qualità fisica dello strato superficiale è risultata
non ottimale anche come conseguenza del pascolamento. Il sito naturale e l’oliveto
hanno evidenziato qualità fisica del suolo scadente. Gli indicatori di natura
“dinamica” hanno dato origine a valutazioni coerenti con gli indici di tipo capacitivo
di cui possono costituire un’utile integrazione
An assessment of the BEST procedure to estimate the soil water retention curve: A comparison with the evaporation method
No full textThe Beerkan Estimation of Soil Transfer parameters (BEST) procedure is an attractive, easy, robust, and inexpensive way for a complete soil hydraulic characterization but testing the ability of this procedure to estimate the water retention curve is necessary as relatively little information is available in the literature. In this investigation the soil water retention curve was predicted for four differently textured soils by applying three existing BEST algorithms (i.e., slope, intercept and steady) and the results compared with those measured by the standard Wind evaporation method. A sensitivity analysis of the infiltration constants, beta and gamma, was also carried out and their impact on the estimated retention curve scale parameter, h(g), was evaluated. BEST-slope underestimated the soil water retention for three of the four soils under consideration, providing relatively low root mean squared differences between estimated and measured data (0.0261 cm(3)cm(-3) <= RMSD <= 0.0483 cm(3)cm(-3)). For one site (PAL, sandy-loam soil), BEST-steady provided the lowest RMSD value (0.0893 cm(3)cm(-3)) among the considered algorithms, but the water retention was systematically overestimated as a consequence of a relatively higher difference between field and lab saturated soil water contents. A specific calibration performed for beta and gamma highlighted that: i) the water retention estimations by BEST-slope were more sensitive to beta than those obtained by BEST-intercept and BEST-steady; ii) with the exception of PAL soil, the lowest RMSD values were obtained with BEST-slope. Estimation of the soil water retention curve was not significantly worse when reference values of infiltration constants (beta = 0.6 and gamma = 0.75) were used as detected by negligible differences in RMSDs as compared to calibrated beta and gamma. Therefore, it was concluded that the BEST slope algorithm yielded predictions of water retention closer to the laboratory estimated ones than the alternative BEST algorithms (i.e. BEST-intercept and-steady). For these algorithms, the less accurate estimates of the water retention data were attributed to h(g) overestimations due to the independence of the retention curve scale parameter from gamma
Evaluation of soil physical quality under different soil land uses in a small Sicilian watershed
Full text linkSustainability of extensive rain fed agriculture needs assessment of land use effects on soil physical and hydraulic properties. Several soil physical quality indices were determined for four adjacent areas in a small Sicilian watershed, that were characterized by a different land use, namely cropland (C), olive grove (O), grassland (G) and eucalyptus plantation (E).
Soil texture was similar for the considered areas, even if the no-tilled soils (G and E) showed a higher clay content in the top layer (0-20 cm) than in the lower layer (20-40 cm). The bulk density of the top layer ranged between 1.20-1.43 g cm-3 (C < G < O < E), with significant differences between C and E. In the lower layer, it ranged between 1.16-1.43 g cm-3 (C < O < E < G), with bulk density of C that was significantly smaller than that of the other land uses. The organic matter content was generally low and comparable for the different areas (in average 1.6%). The near-saturated soil hydraulic conductivity values were significantly higher for no-tilled (G, E) than tilled soils (C, O), whereas the opposite result was found for smaller degrees of saturation. The Dexter’s soil quality index assumed similar values in both the top (0.024-0.047) and the lower layer (0.024-0.040), with the higher values associated to tilled soils.
According to existing guidelines, the soil physical quality of the selected areas was generally poor independently of the land use. However, the cropland showed a better quality than the other land uses
Configurazioni di costi e tipologie produttive
No full textSi affronta la tematica della determinazione dei costi attraverso lo sviluppo di casi su Full costing e Direct costin
Progettazione dei sistemi di contabilità dei costi di produzione
No full textTratta di casi ed esercitazioni relativi all'applicazione dei diversi sistemi di progettazione dei costi di produzion
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
