Two Landsat images, acquired in 1987 and 2008, were analyzed to evaluate desertification processes in central North Kurdufan State (Sudan). Spectral Mixture Analysis (SMA) and multitemporal ...comparison techniques (change vector analysis) were applied to estimate the long-term desertification/re-growing of vegetation cover over time and in space.
Site-specific interactions between natural processes and human activity played a pivotal role in desertification. Over the last 21 years, desertification significantly prevailed over vegetation re-growth, particularly in areas around rural villages. Changes in land use and mismanagement of natural resources were the main driving factors affecting degradation. More than 120,000 km2 were estimated as being subjected to a medium-high desertification rate. Conversely, the reforestation measures, adopted by the Government in the last decade and sustained by higher rainfall, resulted in low-medium re-growth conditions over an area of about 20,000 km2.
Site-specific strategies which take into account the interactions of the driving factors at local scale are thus necessary to combat desertification, avoiding any implementation of untargeted measures. In order to identify the soundest strategies, high-resolution tools must be applied. In this study the application of spectral mixture analysis to Landsat data appeared to be a consistent, accurate and low-cost technique to identify risk areas.
► Spectral mixture analysis to Landsat data allows to assess desertification risk. ► Site-specific interactions between environment and man affect desertification. ► Local-scale strategies are necessary to combat desertification.
•Consider the provision/selling of interruptible load by power-intensive plants.•Use detailed discrete-time scheduling formulation to model the production process.•Characterize uncertainty in load ...reduction demand by budget uncertainty set.•Apply adjustable robust optimization approach to account for recourse decisions.•Practical insights are drawn from a real-world industrial case study.
To ensure the stability of the power grid, backup capacities are called upon when electricity supply does not meet demand due to unexpected changes in the grid. As part of the demand response efforts in recent years, large electricity consumers are encouraged by financial incentives to provide such operating reserve in the form of load reduction capacities (interruptible load). However, a major challenge lies in the uncertainty that one does not know in advance when load reduction will be requested. In this work, we develop a scheduling model for continuous industrial processes providing interruptible load. An adjustable robust optimization approach, which incorporates recourse decisions using linear decision rules, is applied to model the uncertainty. The proposed model is applied to an illustrative example as well as a real-world air separation case. The results show the benefits from selling interruptible load and the value of considering recourse in the decision-making.
In this study we used X-ray microtomography (micro-CT) to evaluate the 3D pore size distribution and morphology of both undisturbed soil cores (5cm diameter, 6cm length) and aggregates (sieved at ...5–6mm). 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 6.25–2000μm 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 >560μm of soil cores and, at the same time, decreased the pores in the range 80–320μm. By contrast aggregate porosity, in the range 12.5–200μm, was weakly affected by the SOC and management practices.
Most likely the low instrumental resolution would mask their effects since previous studies conducted on the same soils showed a significant effect of the management practices on soil microporosity (0.0074–100μm). Therefore the integration of these data, with those obtained in the same plots in previous studies, highlighted the dual effect of SOC as it affected the soil structure at both micro- and macroscale.
•SOC affects the soil structure at both micro- and macroscale.•Pore connectivity was the best index to distinguish the soil management effects.•Pore size distribution was partially able to discriminate between treatments.•Micro-CT must be combined with mercury porosimetry to quantify the soil structure.
Pore complexity and micro‐heterogeneity are pivotal in characterizing biogeochemical processes in soils. Recent advances in X‐ray computed microtomography (microCT) allow the 3D soil morphology ...characterization of undisturbed samples, although its geometrical reproduction at very small spatial scales is still challenging. Here, by combining X‐ray microCT with 3D multijet printing technology, we aimed to evaluate the reproducibility of 3D‐printing soil structures at the original scale with a resolution of 80 μm and compare the hydraulic properties of original soil samples with those obtained from the soil‐like prototypes. Results showed that soil‐like prototypes were similar to the original samples in terms of total porosity and pore shape. By contrast the pore connectivity was reduced by incomplete wax removal from pore cavities after the 3D printing procedure. Encouraging results were also obtained in terms of hydraulic conductivity since measurements were successfully conducted on five out of six samples, showing positive correlation with experimental data. We are confident that future developments of 3D‐printing technologies and of their combination with microCT will help to further the understanding of soil micro‐heterogeneity and its effects on soil‐water dynamics.
► We compared experimental methods for measuring the soil water retention curve. ► Comparative results showed that experimental errors were introduced by traditional methods. ► A relationship between ...experimental errors and textural properties was established. ► Experimental differences affected parameters estimation of hydraulic properties. ► Hydraulic properties parameters impacted computation of deep drainage and evaporation.
Pressure plates apparatus are very common experimental devices utilized to measure the soil water retention curve. Many studies have demonstrated the lack of reliability of pressure plates apparatus when they are used to measure the soil water retention curve in the dry range, due to low plate and soil conductance, lack of hydrostatic equilibrium, lack of soil–plate contact and soil dispersion. In this research, we investigated measurements of soil water retention curves obtained with a combination of Stackman’s tables, pressure plates apparatus and the chilled-mirror dew point technique. Specifically, the aim of this research was: (a) to investigate the differences in the measured soil water retention curves by the different experimental methods, (b) evaluate relationships between the experimental differences and soil texture, (c) analyze the effect of experimental differences on hydraulic properties parameterization and (d) investigate the effects of the different parameters set on water transport computation. The results showed differences in measurements made by the combination of Stackman’s tables and Richards’ pressure plates apparatus as compared to the dew point method, for fine textured soils, while no significant differences were detected for coarse textured soils. Computed cumulative drainage and evaporation displayed lower values if soil water retention curves were obtained from data obtained with the Stackman’s tables and Richards’ pressure plates apparatus instead of the dew point method. In soils, where the soil water retention curve was measured with traditional methods (Stackman’s tables and Richards’ pressure plates apparatus) average cumulative drainage was 173mm, with respect to a combination of methods including the dew point methods, where the average cumulative drainage was 184mm. Average cumulative evaporation was 77mm for the traditional methods, while it was 91mm, for the combination of methods. Overall, when simulation models are used for studies related to solute transport, polluted soil remediation, irrigation management and others, erroneous measurement of the SWRC for fine textured soils, may lead to erroneous computation of the soil water balance.
Summary
Recent advances suggest that organic substances of different origins might have different aggregate stability dynamics. We investigated the extent to which contrasting soil types affect the ...dynamics of aggregation after the addition of crop residues (R) and of biochar at two doses (BC20, 20 Mg ha−1; BC40, 40 Mg ha−1) in a 2‐year experiment. To evaluate disaggregation, we measured a set of physical–chemical and structure‐related properties of clay and sandy loam aggregates sieved to 1–2 mm, including wet aggregate stability after different pretreatments combined with laser diffraction analysis. The electrochemical properties of the colloidal suspension were also analysed to identify changes in soil chemistry affected by organic inputs. Different amounts of added biochar and soil types produced contrasting effects on wet aggregate stability. In sandy loam, the increased soil surface area from added biochar (at either dose) offset the initial small soil organic carbon (SOC) content and subsequently promoted SOC‐controlled aggregation. Conversely in clay soil, the larger biochar dose (BC40) strengthened the repulsive forces between particles with the same charge and monovalent cations, which led to chemical perturbation and some aggregate breakdown not found with BC20. Pore structure also changed in clay aggregates. A shift towards more micropores (30–5 μm, + 29% more than in the control) and ultramicropores (5–0.1 μm, + 22% more than in the control), which contributed to aggregate stabilization, resulted when biochar was added, but not for residue. Our results suggest that biochar promotes aggregate stability, which, in turn, improves the physical fertility of soil, especially if it has a coarse texture and small organic carbon content. Further study is needed of the physical–chemical interactions between added biochar and surface‐charged clay‐rich soils.
Highlights
Aggregate dynamics are poorly understood because of complex interactions between organic inputs and soil type.
A multidisciplinary approach was used to study aggregation dynamics.
Large biochar input changed soil chemical properties that weakened stability in clay aggregates.
Aggregate stability depended on biochar dose and soil type.
Concerns about ammonia (NH3) losses from nitrogen (N) mineral fertilizers have forced policymakers to set emission reduction commitments across Europe. Although best available techniques (BATs) have ...been recommended, large uncertainties still exist due to poorly targeted site-specific approaches that might compromise their effectiveness. Here we proposed and tested a conceptual framework designed to identify most effective BATs that reduce NH3 at the site-specific level. The study was conducted in the Veneto region, northeast Italy. After the mapping of NH3 emission potential areas, BATs and business-as-usual N fertilization scenarios were assessed using a modified version of the DNDC agroecosystem model and compared with urea broadcast distribution under different pedo-climatic conditions. The most promising practices were further tested in a field experiment using a wind tunnel combined with a FTIR gas analyzer. Results showed that closed-slot injection reduced NH3 emissions with any type of mineral or organic fertilizers. Injected application, with ammonium nitrate or organic fertilizers, reduced NH3 loss in maize by 75% and 96%, respectively, and in winter wheat by 87% and 98%, compared to surface broadcast. Injection was the most promising technology to support, being already available to farmers. However, some increase in nitrate leaching was observed, mostly in case of winter wheat (+24% for AN injection; +89% for organic fertilizers). By contrast, urea incorporation with hoeing, the most common technique used by farmers in spring crops, did not show satisfactory results, because the partial burial of urea caused strong NH3 emissions that were even higher compared to surface broadcast. Recommended NH3 reduction techniques should be tailored to local pedo-climatic and management conditions, and evaluated, in a holistic approach, considering all N fluxes in the environment.
•A site-specific approach is required to quantify NH3 emissions from N fertilizer management.•Urea incorporation with hoeing suffers from partial burial that does not limit NH3 emissions.•NH3 emission reduction is achieved by closed-slot injection of mineral N fertilizer.•Technologies limiting NH3 emission can result in increased N leaching or N2O emissions.
•Conservation agriculture management system affected the SOC depth distribution.•C accumulation was observed in conservation agriculture only in the first 30cm.•C accumulation was affected by mineral ...clay composition.•Conservation management led to higher polycondensed humic molecules content.•Soil tillage management did not affect microbial C and N contents.
Conservation agriculture is one of the agro-environment measures promoted by the Veneto Region (North-eastern Italy) to regulate and support many ecosystem services. This study compared conventional and conservation agriculture management systems in order to evaluate their effects on both SOC stocks and quality i.e. humic C and its molecular weight fractions, microbial C and N. The experiment was set up in 2010 on three farms in Veneto Region. In order to improve the monitoring procedures, a massive soil sampling programme was conducted in 2011 and 2014 in ca. 150 positions, considering the SOC stratification within a 0–50cm profile.
Results suggested that conservation agriculture practices affected SOC distribution rather than its total amount. The retention of crop residues on the soil surface and the absence of tillage operations drove SOC dynamics in the top layer (0–5cm) of the conservation system, while residues incorporation with ploughing was responsible for SOC accumulation at the 30–50cm depth in the conventional one. SOC stock variation in the conservation treatment was also influenced by root C input, which was identified as a major factor able to promote SOC accumulation in the 0–30cm profile. The role of clay on SOC dynamics was not uniform in the three farms since it depended both on the clay amount and its mineral composition. The strong interactions existing between management systems and local soil conditions were also confirmed by the C quality analyses.
This research did not demonstrate the benefits of conservation practices on SOC sequestration during the transition period. However, SOC sequestration is only one of the numerous ecosystem services provided by conservation practices. Some of these depend on the C content and quality in the top layers that, as demonstrated in our work, were strongly affected by the C stratification processes triggered by conservation agriculture.
In gravelly soils, surveys are generally time-consuming, labour-intensive and costly. This limits the possibility of adopting an appropriate sampling to determine within-field spatial variability. ...The potential use of electro-magnetic induction scans (EMI) to measure apparent electrical conductivity (EC) and improve the estimate accuracy of sparsely sampled primary variables was assessed in a 5-ha gravelly soil vineyard in Valpolicella, north-eastern Italy. EC was measured using a Geonics EM38DD operating in both horizontal and vertical mode. Geo-electrical investigations were also done in 18 positions with the electrical resistivity tomography (ERT) method to obtain high-resolution images of the soil profile. The spatial variability of soil properties and their relationships with EC in horizontal and vertical mode was estimated using multivariate geostatistical techniques. Spatial dependence between EC and physical soil properties (particle-size distribution) was explored with factorial kriging analysis (FKA) that could isolate and display sources of variation acting at different spatial scales, expressed as regionalised factors, which was followed by fuzzy c-means classification for zoning the vineyard.
There was a generally close relationship between EC and the measured physical properties: EC was negatively correlated with the coarser texture components (gravel and sand) and positively with the finer ones (clay and silt). EC measurements were also consistent with ERT profiles, evidencing the presence of gravelly parent material, with low electrical conductivity, variably distributed in the 3 dimensions and affecting vine rooting depth. FKA isolated two significant regionalised factors which, with an acceptable loss of information, give a concise description of the soil physical variability at the different selected spatial scales. These factors, used in fuzzy c-means classification, allowed the delineation of zones to be managed separately. The results prove that EM38DD could be advantageously used to map soil spatial variability in gravelly soils, even if ground-truth soil samples are obligatory to understand and interpret the EC measurements.
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