The PRISMA satellite mission launched on March 22nd, 2019 is one of the latest spaceborne imaging spectroscopy mission for Earth Observation. The PRISMA satellite comprises a high-spectral resolution ...VNIR-SWIR imaging spectrometer and a panchromatic camera. In summer 2019, first operations during the commissioning phase were mainly devoted to acquisitions in specific areas for evaluating instrument functioning, in-flight performance, and mission data product accuracy. A field and airborne campaign was carried out over an agriculture area in Italy to collect in-situ multi-source spectroscopy measurements at different scales simultaneously with PRISMA. The spectral, radiometric and spatial performance of PRISMA Level 1 Top-Of-Atmosphere radiance (LTOA) product were analyzed. The in-situ surface reflectance measurements over different landcovers were propagated to LTOA using MODTRAN5 radiative transfer simulations and compared with satellite observations. Overall, this work offers a first quantitative evaluation about the PRISMA mission performance and imaging spectroscopy LTOA data product consistency. Our results show that the spectral smile is less than 5 nm, the average spectral resolution is 13 nm and 11 nm (VNIR and SWIR respectively) and it varies ±2 nm across track. The radiometric comparison between PRISMA and field/airborne spectroscopy shows a difference lower than 5% for NIR and SWIR, whereas it is included in the 2–7% range in the VIS. The estimated instrument signal to noise ratio (SNR) is ≈400–500 in the NIR and part of the SWIR (<1300 nm), lower SNR values were found at shorter (<700 nm) and longer wavelengths (>1600 nm). The VNIR-to-SWIR spatial co-registration error is below 8 m and the spatial resolution is 37.11 m and 38.38 m for VNIR and SWIR respectively. The results are in-line with the expectations and mission requirements and indicate that acquired images are suitable for further scientific applications. However, this first assessment is based on data from a rural area and this cannot be fully exhaustive. Further studies are needed to confirm the performance for other land cover types like snow, inland and coastal waters, deserts or urban areas.
•The PRISMA mission is successfully operating and collecting data after the launch.•In-situ simultaneous field/airborne spectroscopy data were compared to PRISMA.•PRISMA spectral resolution is 13–11 nm (VNIR-SWIR), smile is lower of 5 nm.•A radiometric difference of 2–7% was observed between PRISMA and in-situ data.•VNIR-to-SWIR spatial co-registration error is lower of 8 m.
► Biochar application to soil could be a viable option for carbon sequestration. ► Durum wheat yield is increased by biochar application and its quality maintained. ► Converting agricultural residues ...to biochar is a method to reduce CO
2 emissions.
Carbon sequestration in agricultural soils is a climate change mitigation option since most of cultivated soils are depleted of soil organic carbon and far from saturation. The management practices, most frequently suggested to increase soil organic carbon content have variable effects depending on pedo-climatic conditions and have to be applied for a long time periods to maintain their sink capacity. Biochar (BC), a carbon rich product obtained through carbonization of biomass, can be used for carbon sequestration by applying large amounts of carbon very resistant to decomposition. The BC remains into soil for a long time and there is evidence that the BC stores atmospheric carbon from centennial, to millennial timescales. However most of the agronomic studies on BC application have been made in tropical and sub-tropical climates, while there is a substantial lack of studies at mid-latitudes and in temperate climates. This paper presents the results on an investigation of large volume application of BC (30 and 60
t
ha
−1) on durum wheat in the Mediterranean climate condition, showing the viability of BC application for carbon sequestration on this crop. BC application also has positive effects up to 30% on biomass production and yield, with no differences in grain nitrogen content. Moreover no significant differences between the two BC treatments were detected, suggesting that even very high BC application rates promote plant growth and are, certainly, not detrimental. The effect of the biochar on durum wheat was sustained for two consecutive seasons when BC application was not repeated in the second year.
► The present work provides field evidence on the effect of biochar on GHG fluxes in Mediterranean wheat crop. ► No significant increase of N
2O and CO
2 emissions observed in char treated plots. ► ...No significant effect of char on CH
4 soil consumption and production. ► Short term stimulating effect of biochar on soil microflora.
Biochar has been recently proposed as a management strategy to improve crop productivity and global warming mitigation. However, the effect of such approach on soil greenhouse gas fluxes is highly uncertain and few data from field experiments are available. In a field trial, cultivated with wheat, biochar was added to the soil (3 or 6
kg
m
−2) in two growing seasons (2008/2009 and 2009/2010) so to monitor the effect of treatments on microbial parameters 3
months and 14
months after char addition. N
2O, CH
4 and CO
2 fluxes were measured in the field during the first year after char addition. Biochar incorporation into the soil increased soil pH (from 5.2 to 6.7) and the rates of net N mineralization, soil microbial respiration and denitrification activity in the first 3
months, but after 14
months treated and control plots did not differ significantly. No changes in total microbial biomass and net nitrification rate were observed. In char treated plots, soil N
2O fluxes were from 26% to 79% lower than N
2O fluxes in control plots, excluding four sampling dates after the last fertilization with urea, when N
2O emissions were higher in char treated plots. However, due to the high spatial variability, the observed differences were rarely significant. No significant differences of CH
4 fluxes and field soil respiration were observed among different treatments, with just few exceptions. Overall the char treatments showed a minimal impact on microbial parameters and GHG fluxes over the first 14
months after biochar incorporation.
•Crop management strategies play an important role in the soil water content.•The impact of biochar application on soil–water relations and on Vitis vinifera water status was assessed.•Two rates of ...biochar application in two years were considered.•Biochar addition increases the soil water-holding capacity and plant available water content.•Biochar addition substantially affected ecophysiological parameters of V. vinifera.
Soil water status plays an important role in growth-yield and grape quality of Vitis vinifera (L.). In some cases, periods of moderate water stress have been indicated to exert a positive effect on the quality of grape production. However, prolonged water stress may have a strong negative affect grapevine photosynthesis and grape yield, especially in dry Mediterranean environments. Biochar is a co-product of a thermochemical conversion of biomass that is recognized to be a beneficial soil amendment, which when incorporated into the soil increases soil water retention. We investigated the effect of two rates of biochar application (22 and 44tonha−1) on plant water relations of V. vinifera in a field experiment in central Italy. Biochar obtained from the carbonization of orchard pruning waste was applied to the soil over two consecutive growing seasons. The treatments did not show a significant increase in soil hydrophobicity. Moreover, soil analysis and ecophysiological measurements indicated a substantial relative increases in available soil water content compared to control soils (from 3.2% to 45% in the 22 and 44tonha−1 application rates, respectively) and in leaf water potential (24–37%) during droughts.
•The addition of pelletized biochar suddenly increases soil water retention.•The use of pelletized biochar is effective as conditioner in a fine-textured soil.•The incorporation of pelletized biochar ...creates functional accommodation pores.•The amount of biochar directly influences AWC of amended soil.•The pyrolysis process influences biochar AWC.
The field application of pelletized biochar is seldom employed and its effect on soil hydrological behavior scarcely investigated. Biochar is usually added in powdered or granular form to improve the homogeneity of distribution, meanwhile favoring its interaction with soil matrix. In this paper we evaluated the possibility of applying pelletized biochar as soil conditioner during a single cropping season of a tomato cultivation. For that purpose, the water retention curves (WRCs) were determined three months after the addition of two differently pyrolysed biochars (B1 and B2), at the rate of 14Mgha−1, to a silty clay loam soil prone to compaction. Starting from the WRCs the pore size distribution was determined. The gravimetric water content at both field capacity (FC) and wilting point (WP) was also measured on biochar samples to assess their available water capacity (AWC).
In both the treatments, soil bulk density (BD) was significantly lower compared to control (Co), apparently as direct consequence of the addition of low density pellets. Actually, excluding the intrinsic biochar porosity from soil bulk density calculation, BD values of the treated soils remain lower of around 10% over Co. Such findings suggest that a modification of soil structural characteristics might have been induced by pellet addition. Data of the SWRCs indicate a significant increase in transmission (500–50μm), storage (50–0.5μm) and AWC pores (30–0.2μm) for the amended soils. The pyrolysis process seemed to differentiate the extent of direct biochar contribution expressed by AWC values The addition of pelletized biochar was able to enhance the soil water retention properties even in the short term, and such improvement might be correlated to both the inherent biochar retention capacity and to a more functional rearrangement of soil aggregates/particles with pellets.
In regions characterized by arid seasons, such as the Mediterranean basin, soil moisture is a major driver of ecosystem CO₂ efflux during periods of drought stress. Here, a rain event can induce a ...disproportional respiratory pulse, releasing an amount of CO₂ to the atmosphere that may significantly contribute to the annual ecosystem carbon balance. The mechanisms behind this pulse are unclear, and it is still unknown whether it is due to the stimulation of autotrophic, heterotrophic and/or inorganic CO₂ fluxes. On the Mediterranean island of Pianosa, eddy flux measurements showed respiratory pulses after rain events following prolonged drought periods, which occurred in the summer of 2003 and 2006. To investigate the mechanisms of this observed enhanced respiration fluxes and partition of the soil CO₂ sources, two water manipulation experiments were performed. The first was designed to estimate the effect of soil rewetting on soil CO₂ efflux, in the different ecosystem types existing on the island (i.e. woodland, ex-agricultural and Mediterranean shrubland). The second was a soil CO₂ partitioning experiment to investigate the relative contribution of inorganic and organic CO₂ sources to soil respiration, under dry and wet soil conditions. Our results suggest that the pulse in the CO₂ efflux is primarily due to the enhancement of heterotrophic respiration, likely caused by the degradation of easily decomposable substrates, accumulated in soils during the dry period. In fact, the vegetation at the site was senescent and did not play any significant role in CO₂ exchange, as suggested by the absence of diurnal CO₂ uptake in eddy covariance measurements. In addition, soil rewetting did not significantly enhance inorganic CO₂ efflux.
•Field biochar application did not enhance tomato yield nor affect quality.•Biochar application had positive effects on soil fertility.•Biochar application in high fertility conditions can be a ...sustainable practice.
Biochar addition to soil is a promising option for climate change mitigation and is recognized to exert beneficial effects on soil fertility. However, recent meta-analysis documented controversial effects on soil–plant interactions and on crop yields response.
The data presented in this paper are the results of a field experiment on a processing tomato crop aiming to enhance the knowledge on the real applicability of biochar at farm scale in a high fertility alkaline soil. The effects of two biochar types on soil properties and on quantitative and qualitative parameters of processing tomato were evaluated. Biochar application significantly increased the soil carbon content, the soil cation exchange capacity and the availability of NH4+, P and K. Moreover, it stimulated plant growth and N, P and base cation contents at harvest, reducing the leaf water potential in the warmer period. These results demonstrate that also intensive cultivations in fertile soil can benefit from biochar amendment.
Observations on the net carbon exchange of forests in the European Mediterranean region, measured recently by the eddy covariance method, have revived interest in a phenomenon first characterized on ...agricultural and forest soils in East Africa in the 1950s and 1960s by H. F. Birch and now often referred to as the "Birch effect." When soils become dry during summer because of lack of rain, as is common in regions with Mediterranean climate, or are dried in the laboratory in controlled conditions, and are then rewetted by precipitation or irrigation, there is a burst of decomposition, mineralization and release of inorganic nitrogen and CO(2). In forests in Mediterranean climates in southern Europe, this effect has been observed with eddy covariance techniques and soil respiration chambers at the stand and small plot scales, respectively. Following the early work of Birch, laboratory incubations of soils at controlled temperatures and water contents have been used to characterize CO(2) release following the rewetting of dry soils. A simple empirical model based on laboratory incubations demonstrates that the amount of carbon mineralized over one year can be predicted from soil temperature and precipitation regime, provided that carbon lost as CO(2) is taken into account. We show that the amount of carbon returned to the atmosphere following soil rewetting can reduce significantly the annual net carbon gain by Mediterranean forests.
•New insights into the effects of biochar on fine root dynamics are presented.•An increase of fine root biomass occurred immediately after biochar application.•Fine root biomass increment during ...water shortage could be attributed to radial growth.•Biochar had no significant effect on the annual production of arbuscular mycorrhiza.
Application of biochar to the soil is globally recognised as a means to improve soil structure and fertility, increase carbon sequestration, enhance crop production and mitigate climate change. However, although the fine root system is fundamental for plant growth, crop productivity, carbon and nutrient cycling, little is known about the effect of biochar on plant fine roots. This study, conducted in a Montepulciano (Vitis vinifera L.) vineyard, was aimed at investigating the impact of biochar application (at the rate of 10tha−1) on soil chemical and physical properties, fine root dynamics and arbuscular mycorrhizal fungi (AMF) production during a one-year sampling period. To this aim, seasonal variation of fine root mass, length and diameter was measured by the sequential coring technique, whereas fine root annual production was calculated by minimum-maximum procedure and turnover rate of live roots by maximum standing biomass. For AMF annual production, in-growth mesh bags were used to measure glomalin as quantitative indicator of mycorrhizae presence. Results showed that biochar significantly increased organic carbon (20.7%), available ammonium (84.4%), and available water content of the soil (11.8%), while it also promoted the formation of the large fraction of macro aggregates (ø>2mm; 3.1% control; 5.5% treated). Cation exchange capacity, pH, total nitrogen content, and total and available phosphorus content remained unaffected. Immediately after biochar soil amendment, while fine root length remained unchanged, a significant increase in fine root biomass was measured resulting in a higher mean annual biomass (8.56gm−2 control; 13.34gm−2 treated), annual production (8.71gm−2 control; 12.7gm−2 treated) and lifespan (as evidenced by a lower turnover rate; 1.02 yr−1 control; 0.95 yr−1 treated). Moreover, the increase of fine root biomass resulted to be associated with radial growth since mean fine root diameter was significantly higher in biochar-treated plants (0.56mm) than in control plants (0.46mm). Biochar had no significant effect on the annual production of AMF. The results of the present study show that the improvements of soil chemical and physical features due to biochar application have an immediate effect on fine root dynamics and morphology. Furthermore, the increase of fine root biomass is mainly due to radial growth and occurs during the water shortage period, supporting fruit setting and ripening in grapevine plants.
The agronomic use of charcoal from biomass pyrolysis (biochar) represents an interesting option for increasing soil fertility and sequestering atmospheric CO2. However, before moving toward ...large-scale biochar applications, additional research must evaluate all possible land-atmosphere feedbacks. Despite the increasing number of studies investigating the effect of biochar on soil physical, chemical and biological properties, only a few have been done on surface albedo variations on agricultural lands. The present work had the aim of characterizing the annual albedo cycle for a durum wheat crop in Central Italy, by means of a spectroradiometer measurement campaign. Plots treated with biochar, at a rate of 30-60 t ha−1, showed a surface albedo decrease of up to 80% (after the application) with respect to the control in bare soil conditions, while this difference tended to decrease during the crop growing season, because of the prevailing effect of canopy development on the radiometer response. After the post-harvesting tillage, the soil treated with biochar again showed a lower surface albedo value (<20-26% than the control), while the measurements taken in the second year after application suggested a clear decrease of biochar influence on soil color. The modeling of the surface energy balance highlighted changes in the partitioning of heat fluxes and in particular a substantial increase of ground heat fluxes on an annual basis.
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