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[BACKGROUND] Despite the optimal characteristics of peat, more environmental-friendly materials are needed in the nursery sector, although these must guarantee specific quantitative and qualitative commercial standards. In the present study, we evaluated the influence of biochar and compost as peat surrogates on yield and essential oil profile of two different varieties of basil (Ocimum basilicum var. Italiano and Ocimum basilicum var. minimum). In two 50-day pot experiments, we checked the performances of biochar from pruning of urban trees and composted kitchen scraps, both mixed in different proportions with commercial peat (first experiment), and under different nitrogen (N) fertilization regimes (second experiment), in terms of plant growth and volatile compounds profile of basil., [RESULTS] Total or high substitution of peat with biochar (100% and 50% v.v.) or compost (100%) resulted in seedling death a few days from transplantation, probably because the pH and electrical conductivity of the growing media were too high. Substrates with lower substitution rates (10–20%) were underperforming in terms of plant growth and color compared to pure commercial peat during the first experiment, whereas better performances were obtained by the nitrogen-fertilized mixed substrates in the second experiment, at least for one variety. We identified a total of 12 and 16 aroma compounds of basil (mainly terpenes) in the two experiments. Partial replacement of peat did not affect basil volatile organic compounds content and composition, whereas N fertilization overall decreased the concentration of these compounds., [CONCLUSION] Our results support a moderate use of charred or composted materials as peat surrogates.

Mineral fertilizers are widely used in conventional agriculture to boost crop yield. However, their overuse can lead to inefficient nutrient use by plants, causing environmental issues like nutrient losses and water pollution. Recently, there has been a growing interest in using chars, such as biochar or hydrochar (HC), as sustainable alternatives to traditional fertilizers for enhancing plant growth. Yet, exploring the potential toxic impact of these materials on soil and plants is an area that requires further investigation. Similarly, assessing their fertilizing capacity requires studies beyond plant biomass analysis. For this reason, the present study focuses on evaluating the impact of applying HC derived from chicken manure on the use efficiency of some of the most important macronutrients for sunflower plants (Helianthus annuus L.). Additionally, it was studied under both well-irrigated and drought conditions to understand the performance of the plants under two different irrigation scenarios. For this purpose, a greenhouse soil pot experiment lasting for 77 days was conducted. HC was administered to a soil at application rates of 3.25 and 6.5 t ha-1 (HC-3.23 and HC-6.5). Comparative mineral fertilizer treatments (NPK) with equivalent total nitrogen contributions as the amendment were incorporated for evaluation. Under both irrigation conditions, soils treated with HC-6.5 demonstrated significantly increased total plant and seed biomass yields in comparison to untreated soils, but no significant differences were observed compared to the mineral fertilizer counterpart. When parameters related to nutrient use efficiency were analyzed, HC-6.5 treatment under both irrigation conditions exhibited the highest values in S uptake efficiency. Interestingly, regarding K, plants treated with HC-6.5 showed two strategies of use efficiency depending on the irrigation condition. While under well-irrigated conditions, these plants demonstrated a higher K uptake efficiency

In recent decades, the potential use of chars, such as biochar or hydrochar, as soil amendments to enhance plant growth, has garnered significant interest. However, understanding potential toxic impact of these materials on soil and plants remains an area requiring further exploration. In this study, the effect of applying hydrochar (HC) derived from chicken manure on the yield and nutritional quality of sunflower (Helianthus annuus L.) seeds was assessed under both wellirrigated and water deficit (WD) conditions. To address it, the HC was applied to a Cambisol at rates of 3.25 and 6.5 t ha-1. Mineral fertilizer treatments with equivalent total nitrogen contributions as the amendment were included for comparison. Sunflower plants were cultivated in pots under two irrigations conditions (60 and 30% of the soil water holding capacity). After 77 days of cultivation, the plants were harvested, and the content of macro- and micronutrients, heavy metals in both seeds and leaves, as well as the seed fatty acid composition, were analyzed. Additionally, soil nutrient contents were assessed post-experiment. Initially, HC application did not cause a noticeable change in soil nutrient composition. However, both HC applications demonstrated high productivity under well-irrigated conditions. Likewise, under WD conditions, the best yields were achieved with a HC dose of 6.5 t ha-1. Conversely, the composition of the different fatty acids in the seed oil remained unaffected by the treatments and irrigation conditions. Nonetheless, seed nutrient content was notably affected, particularly in plants treated with 6.5 t ha-1. Under well-irrigated conditions, the seeds of these plants exhibited decreased K and P levels, along with higher levels of toxic elements and heavy metals such as Al, Ba, Cd, Pb, and Sr. Under WD conditions, the impact of the treatment on heavy metals contents was less pronounced, but there was a marked reduction of seed macronutrient content (Ca, K, Mg, P and S).

Nitrogen (N) immobilization controls the N availability in soil, however, mechanisms involved in the chemical N fixation into soil organic N (SON) through reactions of reactive N compounds with soil organic matter (SOM) is not clear. Knowledge about the composition and stability of chemically produced SON is limited, which impedes understanding of the interplay of N and carbon (C) cycles at both the local and global scale. Here, we studied the chemical N immobilization of nitrite in soils from grassland, cropland, and forest with 15N labelling technique. And solid state 15N- and 13C NMR spectroscopies were applied to further explore the structure of chemically immobilized SON. We found that the chemical retention rate of nitrite did not differ significantly between land-uses, while the fulvic acid fraction was the SOM component most reactive to nitrite. In contrast to the common assumption that amides are mainly of biological origin and that black N compounds are formed from organic N compounds at high temperature during fires, our study revealed that amides and black N in the form of pyrroles were the main products of chemical reactions of nitrite with SOM. These findings indicate that chemical processes play a key role in biogeochemical N cycling, and provide new insight into the mechanisms of Csingle bondN interactions in soil

Background: The use of carbonaceous materials for environmental remediation is attractive due to low expense and high sorption capacity. However, their efficiency in contaminant removal is affected by substrate composition and sorption mechanism.Objective: This study investigated atrazine sorption and desorption in three carbon-rich substrates. Data were evaluated considering isotherm models and sorbent chemical composition.Methods: Sorption was performed by the batch equilibrium method with three substrates obtained from pig slurry composting with different proportions (w/w) of charcoal fines (CF): CF0, CF9 (9% CF), and CF18 (18% CF). The substrates were characterized by elemental analysis, 13C NMR CP/MAS spectroscopy. The Freundlich and Dubinin-Radushkevich (DRK) models better fitted the sorption data (0.96>R2>0.81), followed by Temkin (0.95>R2>0.76). Charcoal addition to composting substrates increased carbon content and the aromaticity in the order CF010 mg L-1), and the desorption Kf values were greater than the respective sorption values. Conclusions: Atrazine sorption in the tested C-rich substrates is not governed by the carbon content or aromaticity. The low sorption reversibility implies a low atrazine mobility from the tested substrates and suggests their potential for herbicide removal in the environment. © 2023, Sociedade Brasileira da Ciencia das Plantas Daninha. All rights reserved.

Slash-and-burn of Amazon Forest (AF) for pasture establishment has increased the occurrence of AF wildfires. Recent studies emphasize soil organic matter (SOM) molecular composition as a principal driver of post-fire forest regrowth and restoration of AF anti-wildfire ambience. Nevertheless, SOM chemical shifts caused by AF fires and post-fire vegetation are rarely investigated at a molecular level. We employed pyrolysis–gas chromatography–mass spectrometry to reveal molecular changes in SOM (0–10, 40–50 cm depth) of a slash-burn-and-20-month-regrowth AF (BAF) and a 23-year Brachiaria pasture post-AF fire (BRA) site compared to native AF (NAF). In BAF (0–10 cm), increased abundance of unspecific aromatic compounds (UACs), polycyclic aromatic hydrocarbons (PAHs) and lipids (Lip) coupled with a depletion of polysaccharides (Pol) revealed strong lingering effects of fire on SOM. This occurs despite fresh litter deposition on soil, suggesting SOM minimal recovery and toxicity to microorganisms. Accumulation of recalcitrant compounds and slow decomposition of fresh forest material may explain the higher carbon content in BAF (0–5 cm). In BRA, SOM was dominated by Brachiaria contributions. At 40–50 cm, alkyl and hydroaromatic compounds accumulated in BRA, whereas UACs accumulated in BAF. UACs and PAH compounds were abundant in NAF, possibly air-transported from BAF.

We checked the effect of biochar addition to a fertile temperate soil on plant growth and the quantity and quality of seeds of four varieties of wheat (Triticum spp., two “ancient” varieties, Verna and Senatore Cappelli, and two “modern” varieties, Bologna and Claudio) and a high oleic hybrid of sunflower (Helianthus annuus L.). Relatively novel is the qualitative investigation of the marketable product, as few are the works on this topic. We tested three different doses of biochar—1, 4, and 20 t ha−1—versus an untreated soil (“control”) in a 2-year open field trial in Central Italy, where wheat was grown the first year and sunflower the second year. Biochar addition did not change the soil characteristics save for the carbon content, which increased significantly with the highest dose of biochar. Also, we did not find any significant biochar-induced effect on plant growth and yields of both wheat and sunflower. Regarding the qualitative aspects, adding biochar to the soil implied an increase in total polyphenols in the middlings and bran of wheat and, with the highest dose of biochar, also in total proteins and in flavonoids and caffeic acid derivatives. Instead, no difference in carotenoids concentration and antiradical activity was observed in middlings or bran. As for the sunflower, no significant difference in seeds’ composition was detected at any of the biochar doses. The addition of biochar to a fertile, well-drained soil as the one we investigated is not detrimental to the quantity and quality of wheat and sunflower seeds. Rather, the concentration of some polyphenols in wheat appears to be positively affected by biochar addition.

Maritime Antarctic King George Island (South Shetland Islands) has experienced rapid warming in recent decades, but the impacts on soil organic matter (SOM) decomposition remain ambiguous. Most vegetation cover is dominated by bryophytes (mosses), whereas a few vascular plants, such as Deschampsia antarctica and Colobanthus quitensis grow interspersed. Therefore, SOM is mainly enriched with carbohydrates and C-alkyl, provided by mosses, which lack lignin as a precursor for aromatic compounds and humus formation. However, there is no clear answer to how substrate and temperature increase changes in Antarctic microbial respiration. We determined in what way SOM mineralization changes with temperature and substrate addition by characterizing the temperature sensitivity (Q10) of soil respiration in an open-top chamber warming experiment. We hypothesized that: (a) cold-tolerant microorganisms are well adapted to growing in maritime Antarctic soils (~ 0°C), so would not respond to low and moderate temperature increases because they undergo various metabolic mechanism adjustments until they experience increasing temperatures toward optimum growth (e.g., by enzyme production); and (b) cellulose, as a complex carbonaceous substrate of vegetated areas in Maritime Antarctic soils, activates microorganisms, increasing the Q10 of soil organic carbon (SOC) mineralization. Soils (5–10 cm) were sampled after four consecutive years of experimental warming for SOC composition, microbial community structure, and C mineralization at 4, 12, and 20°C with and without cellulose addition. Functional group chemoheterotrophs, represented mainly by Proteobacteria, decomposed more refractory SOC (aromatic compounds), as indicated by nuclear magnetic resonance (NMR) spectroscopy, in ambient plots than in warming plots where plants were growing. The C-CO2 efflux from the incubation experiment remained stable below 12°C but sharply increased at 20°C. Q10 varied between 0.4 and 4 and was reduced a

Black carbon or pyrogenic carbon (PyC) represents a ubiquitous entity of soil organic matter (SOM). Presently, it is best described as a continuum of thermally altered biomolecules. The degree of their alteration depends on heat severity, heating conditions (oxic, pyrolysis), and the nature of the feedstock. Comparably, a paradigm shift occurred with respect to the biochemical recalcitrance of PyC taking into consideration that the latter depends not only on the degree of charring of the respective PyC but also relies on soil conditions. There is a clear effect on PyC properties (increasing pH, darkness, hydrophobicity, and plant nutrient contents), which can survive on a long-term scale. Thus, fire and biochar amendment may play an important role in pedogenetic processes. © 2023 Elsevier Ltd. All rights reserved.

The COVID-19 pandemic caused massive use and improper disposal of surgical polypropylene (PP)-based face masks. For a first evaluation of the respective environmental consequences, we performed a 6-month microcosm experiment at 25 °C to determine the microbial degradability of 10 × 10 mm cuts of single mask layers and of a complete mask mixed with topsoil (Cambisol). By analyzing the CO2 production, we identified a fast pool with a mean residence time (MRTfast) of 3 to 7 days, corresponding to approximately 4 to 5% of the total mask carbon. Solid-state nuclear magnetic resonance (NMR) spectroscopy of the degraded masks suggests a cut-off of PP units or oligomers as a main degradation mechanism. The slow carbon pool of the center mask revealed an MRTslow of 7 years and those of the remaining mask material MRTslows between 19 and 28 years, which is three to five times longer than those of soil organic matter (SOM) of the pure soil. Since the masks were not pretreated, and decomposed in the dark without UV radiation, our data support our hypothesis that in soils, microbes must exist that can decompose PP, although their nature still has to be revealed in future attempts.

Endocarp residues remaining after coconut oil extraction from Acrocomia aculeate are traditionally used for combustion as fuel. As an alternative, we propose its conversion into biochar to substitute peat in planting substrates. To test the feasibility of this approach, untreated endocarp residues (particle size approx. 10 mm) and materials shredded into particles of 4 and 1 mm were pyrolyzed at 200 °C, 325 °C and 450 °C and were subsequently characterized. The pyrolysis-induced loss of organic matter increased the ash contents and pH. Nuclear magnetic resonance (NMR) spectroscopy confirmed the aromatization and a loss of carboxyl C with an increasing pyrolysis temperature. This is commonly associated with an enhanced biochemical recalcitrance. The particle size of the feedstock had no significant effect on the chemical composition or microporosity (BET-adsorption with COs) of the biochars, but affected their water holding capacity. With respect to macro- and micronutrients, only the potassium and Olsen P levels occurred in concentrations that are optimal for tomato seed growth. The low nitrogen level of the products may be advantageous for hydroponic culturing since it allows for a higher flexibility for the adaptation of nutrient contents based on the needs of the used culture.

The use of peat in traditional cultivation systems and in commercial nurseries is an environmental problem. In this work, we evaluated the partial replacement of peat with different amounts of biochar sourced from vineyard pruning as plant growing substrates. We studied its effect on the growth of lettuce plants under greenhouse and semi-hydroponic conditions. Substrate mixtures contained 30% (v/v) of vermiculite and 70% (v/v) of different biochar:peat treatments as follows: 0:70 (B0), 15:55 (B15), 30:40 (B30), 50:20 (B50), and 70:0 (B70). Higher biochar treatments increased the pH and electrical conductivity of the substrate, negatively affecting plant growth and germination (especially in B70). The partial substitution of peat by 30% biochar (B30) delayed seed germination but improved plant growth and nitrogen use efficiency (NUE), with shoots containing higher levels of organic nitrogen and nitrate. Moreover, it increased the water holding capacity (WHC) and led to an efficient use of nutrients. Our study demonstrates that biochar can successfully replace and reduce peat and N fertilizer consumption. This has the potential to promote more sustainable farming with positive impacts on both plant growth and the environment.

Hydrothermal technologies are considered promising for producing valuable products like hydrochar from renewable biomass waste. Hydrochar (HC), acting as a hopeful substitute for current commercial fertilizers, has the potential to serve as a soil amendment, improving soil quality, microbial activity, and crop production. However, our understanding of the underlying mechanisms of hydrochar biogeochemical processes and their effects on planted soils is still challenging. Additionally, there is limited knowledge about the effects under deficit irrigation conditions. The aim of this study was to assess the impact of the interaction between treated soil, plants, and microorganisms on soil organic matter (SOM), soil nutrients, microbial activity, plant growth, and irrigation management in soils.

Climate change, with its increasing temperaturas and prolonged drought events, poses pressing challenges for agricultura, food security and the environment. To address these concerns, alternative agricultural practices are needed, including sustainable fertilization methods and improved water use efficiency. Promoting the circular economy and environmental sustainability, hydrothermal carbonization offers a promising solution by converting biomass waste into hidrochar (HC), a carbon-rich soil amendment with the potential to serve as a substitute form traditional fertilizers and enhance water management in agriculture. The aim of this study was to evaluate the use of HC as an alternative fertilizer and investigate its impact on plant productivity and water status under two different irrigation conditions.

Invitación por parte del Dr. Jorge Medina Otárola para impartir una presentación oral en españól, en la jornada de seminario con título "Valorización de residuos agropecuarios y sus potenciales usos agroambientales en contexto de cambio climático" del Campus Colchagua de la Universidad de O'Higgins (San Fernando, Chile). Pueden ver en video a través de @YouTube, la presentación a partir del minuto 49:30 el doctorando Francisco J. Moreno-Racero del IRNAS CSIC hizo la presentación oral: Multidisciplinary approach on the impact of hydrochar on the soil-plant-microorganisms systems.en la jornada de seminarios con título "Valorización de residuos agropecuarios y sus potenciales usos agroambientales en contexto de cambio climático" del Campus Colchagua de la Universidad de O'Higgins (San Fernando, Chile).https://www.youtube.com/live/M7B06bfpW0Q?feature=shared

Climate change, with its increasing temperaturas and prolonged drought events, poses pressing challenges for agricultura, food security and the environment. To address these concerns, alternative agricultural practices are needed, including sustainable fertilization methods and improved water use efficiency. Promoting the circular economy and environmental sustainability, hydrothermal carbonization offers a promising solution by converting biomass waste into hidrochar (HC), a carbon-rich soil amendment with the potential to serve as a substitute form traditional fertilizers and enhance water management in agriculture. The aim of this study was to evaluate the use of HC as an alternative fertilizer and investigate its impact on plant productivity and water status under two different irrigation conditions.

Hydrothermal technologies are considered promising for producing valuable products like hydrochar from renewable biomass waste. Hydrochar (HC), acting as a hopeful substitute for current commercial fertilizers, has the potential to serve as a soil amendment, improving soil quality, microbial activity, and crop production. However, our understanding of the underlying mechanisms of hydrochar biogeochemical processes and their effects on planted soils is still challenging. Additionally, there is limited knowledge about the effects under deficit irrigation conditions. The aim of this study was to assess the impact of the interaction between treated soil, plants, and microorganisms on soil organic matter (SOM), soil nutrients, microbial activity, plant growth, and irrigation management in soils.

Compost amendments, apart from improving fertility and the general characteristics of agricultural soils, have known implications for global C cycling and sequestration in soils. Their effects are usually assessed via the quantification of soil organic carbon (SOC) pools, usually labile (fast) and recalcitrant (slow) pools, with varying intrinsic decomposition rates and distinct resident times. However, the real C-sequestration potential of organic additions to soil is still under discussion. In this study, a field trial and a lab incubation experiment were designed to study the C-sequestration mechanism in an agricultural Mediterranean soil. Soil with a history of C3 photosystem crop was amended with two maize composts from maize harvesting surpluses (C4 photosystem) with different maturity stages (AC: aged compost; NC: new, less mature compost). The evolution of SOM was monitored for 6 months using complementary analytical techniques, including analysis of stable C isotopes (IRMS), thermogravimetry (TG) and C-stock and priming effect (PE) modelling. Based on the natural C-isotope labelling, the proportion of new C was calculated. More than 50% of the C added to the soil with the compost was incorporated into the SOM in only 6 months. However, the application of maize compost did not always enhance soil C-sequestration capacity. The addition of compost caused a general PE, enhancing SOM decay and reducing the fast (labile) SOM mean residence time (MRT) (11.2 days). This was more pronounced with the addition of a higher dose of AC, causing a PE up to a 718%. On the other hand, a higher MRT (54.4 days) occurred in soils with NC applied, likely due to its deleterious effects, limiting heterotrophic activity. Despite that, the average MRT of the slow (recalcitrant) SOM pool was lower than usually reported. The application of higher doses of both composts generally showed greater MRT values compared to control (1.7 years vs. 3.8 and 2.9 years for NC and AC, respectively

E n el contexto actual de cambio climático, las zonas del sur de Europa corren un elevado riesgo de verse afectadas por la desertificación. En particular España, con más de la mitad de su superficie cubierta por tierras de secano [1]. Por ello, la gestión sostenible del suelo agrícola es crucial para mantener no sólo la calidad del suelo sino también su potencial para actuar como sumidero de carbono (C). En este trabajo, se han estudiado suelos de un olivar ubicado en Benacazón (Sevilla, España) expuestos a diferentes sistemas de manejo para determinar la calidad y la cantidad de materia orgánica del suelo (MOS) y su microbioma. Se estudiaron tres tratamientos: líneas de árboles con regadío y tratadas con herbicida (LAHerb.), y calles entre árboles con laboreo convencional (LC) o con cobertura de vegetación natural mixta (CM). Se tomaron muestras compuestas de la capa superior del suelo (0-20 cm). Mediante espectroscopia de resonancia magnética nuclear (RMN) 13C CP/MAS en estado sólido para la caracterización de la MOS, no se observaron diferencias importantes entre las muestras de las calles interarbóreas, que presentaron un mayor grado de humificación (menor ratio alquil C / O alquil C) que las de las líneas de árboles tratadas con herbicida. Esto puede atribuirse al efecto del herbicida, que redujo la cantidad de biomasa vegetal que entraba en el sistema del suelo. Por otro lado, utilizando el análisis de ácidos grasos de fosfolípidos (PLFA), los suelos CM mostraron el mayor contenido de biomasa bacteriana y fúngica. Para una mejor comprensión de cómo estas diferencias están relacionadas con el secuestro de C, los datos obtenidos se compararán con las respectivas reservas de carbono de los suelos estudiados.

La agricultura actual se enfrenta al reto de garantizar el suministro de alimentos a una población en continuo crecimiento mientras la actividad humana ya ha deteriorado sobre el 40% de los suelos cultivables del planeta, aumentando la dependencia de los fertilizantes minerales. En este contexto, la valorización de residuos agrícolas para utilizarlos como sustratos o suplementos del suelo se propone como alternativa, creando además una solución a la generación masiva de residuos orgánicos agro-ganaderos. Este trabajo muestra las propiedades físicas de interés agrnómico y la composición (macro y micronutrientes) de biochars, composts y cenizas producidas a partir de restos vegetales de las agroindustrias olivadera y des arroz, y los efectos de su aplicación a los suelos calcáreos (Xerochrept y Luvisol) bajo condiciones de clima mediterraneo. Las enmiendas mostraron atributos apropiados para mejorar las propiedades agronómicas del suelo. El biochar mostró una alta aromaticidad y abundancia de C orgánico estable. Las enmiendas ricas en ceniza mostraron altos contenidos en P y K y micronutrientes. El compost presento una elevada capacidad de retención de agua y un adecuado balance de C y N. Todas las enmiendas orgánicas redujeron la hidrofobicidad del suelo. La aplicación de biochar consiguió aunmentar la humedad del suelo en los primeros 10 cm y reducir su compactación, los que se evidencio por la reducción significativa de la resistencia del suelo a la penetrabilidad. Las plantas de las parcelas enmendadas mostraron un mejor potencial hídrico foliar. Además, los valores de la tasa de fotosíntesis neta, la eficiencia media de uso del agua intrínseca y la tasa máxima del transporte de electrones en el momento de la cosecha mejoraron significativamente en los árboles de las parcelas enmendadas con una dosis de biochar de 40 t ha-1. En relación al ciclo de C, la adición de compost incrementó de manera significativa la respiración (emisión de CO2) y la cantidad de C proced

The use of peat in traditional agricultural systems and nursery enterprises is an environmental preoccupation. Since the high CO2 and greenhouse gas (GHG) emission due to peat excavation and transport contributes considerably to climate change and global warming it is key to find alternative material which can substitute this limited resource. One of this represents biochar. As a potential highly recalcitrant and aromatic "humic substance" (HS) it was shown to promote sustainable agriculture, contributing to the concept of circular economy, leveraging biomass waste and boosting nutrient recovery and use efficiency. In this work we partially replaced peat with different amounts of biochar obtained from vineyard pruning as plant growing substrates whereas implementing N (Nitrogen) fertirrigation. We studied the effect on the growth, different content of N forms and other nutrient dynamics impact of lettuce plants grown under greenhouse and semi-hydroponics conditions. Substrate mixtures contained 30% of vermiculite and 70% of different biochar:peat treatments as follows: 0:70 (B0), 15:55 (B15), 30:40 (B30), 50:20 (B50), and 70:0 (B70). Higher biochar treatments increased pH and electrical conductivity of the substrate, negatively affecting plant growth and germination. The substitution of 30% peat by biochar (B30) delayed seed germination but improved plant growth and N use efficiency without showing stress symptoms. This is related with a higher nitrate (NO3-) retention capacity in the substrate, leading to higher allocation and flux of N to the plant shoot and a better performance of N metabolic enzymes (NR, GS, GOGAT, GDH). The treatment B30 also increased the water holding capacity of the substrate, which may enhance soil moisture characteristics and pore size distribution, maximizing water availability to plants.

The application of biochar as an organic amendment in polluted soils can facilitate their recovery by reducing the availability of contaminants. In the present work, the effect of biochar application to acid soils contaminated by heavy metal spillage is studied to assess its effect on the quantity and composition of soil organic matter (SOM), with special attention given to soil humic acids (HAs). This effect is poorly known and of great importance, as HA is one of the most active components of SOM. The field experiment was carried out in 12 field plots of fluvisols, with moderate and high contamination by trace elements (called MAS and AS, respectively), that are located in the Guadiamar Green Corridor (SW Spain), which were amended with 8 Mg·ha−1 of olive pit biochar (OB) and rice husk biochar (RB). The results indicate that 22 months after biochar application, a noticeable increase in soil water holding capacity, total organic carbon content, and soil pH were observed. The amounts of oxidisable carbon (C) and extracted HAs in the soils were not altered due to biochar addition. Thermogravimetric analyses of HAs showed an increase in the abundance of the most thermostable OM fraction of the MAS (375–650 °C), whereas the HAs of AS were enriched in the intermediate fraction (200–375 °C). Spectroscopic and chromatographic analyses indicate that the addition of biochar did not alter the composition of the organic fraction of HAs, while Cu, Fe, and as were considerably accumulated at HAs.

Endocarp residues remaining after coconut oil extraction from Acrocomia aculeate are traditionally used for combustion as fuel. As an alternative, we propose its conversion into biochar to substitute peat in planting substrates. To test the feasibility of this approach, untreated endocarp residues (particle size approx. 10 mm) and materials shredded into particles of 4 and 1 mm were pyrolyzed at 200 °C, 325 °C and 450 °C and were subsequently characterized. The pyrolysis-induced loss of organic matter increased the ash contents and pH. Nuclear magnetic resonance (NMR) spectroscopy confirmed the aromatization and a loss of carboxyl C with an increasing pyrolysis temperature. This is commonly associated with an enhanced biochemical recalcitrance. The particle size of the feedstock had no significant effect on the chemical composition or microporosity (BET-adsorption with COs) of the biochars, but affected their water holding capacity. With respect to macro- and micronutrients, only the potassium and Olsen P levels occurred in concentrations that are optimal for tomato seed growth. The low nitrogen level of the products may be advantageous for hydroponic culturing since it allows for a higher flexibility for the adaptation of nutrient contents based on the needs of the used culture.

El uso excesivo de plásticos tales como el polipropileno representa un serio problema ambiental agravado con la llegada de la pandemia y el desecho constante de mascarillas higiénicas, fabricadas con fibras de este material. En este trabajo planteamos el estudio de la degradación microbiana de mascarillas debido a la larga persistencia del polipropileno en la naturaleza. Realizamos cultivos de enriquecimiento de microorganismos procedentes de una muestra natural de suelo suplementados con fragmentos de mascarillas. La identificación de los microorganismos que componen el enriquecimiento obtenido se llevó a cabo por secuenciación de su metagenoma (shotgun sequencing). Con objeto de simular posibles efectos físico-químicos sobre la biodegradabilidad del material, se analizaron una serie de factores, incluyendo pre-tratamientos térmicos, enzimáticos, con metales y la presencia de surfactantes. Las fibras se evaluaron mediante análisis microscópico. El enriquecimiento obtenido mostraba un aparente inicio de descomposición en anaerobiosis. Los componentes mayoritarios de la comunidad microbiana enriquecida fueron Franconibacter daqui, Desulfotomaculum aeronauticum, Sedimentibacter sp. y Clostridium intestinale. Cultivos de ese enriquecimiento en medio destinado al crecimiento de bacterias reductoras de sulfato dió lugar a la presencia de partículas de sulfuro metálico adheridas a la mascarilla lo que sugería que Desulfotomaculum, una típica bacteria reductora de sulfatos, podría estar implicada en la degradación de las fibras de las mascarillas. Los análisis microscópicos de fibras han permitido observar la asociación de estas bacterias a las fibras. Visualmente no se han observado efectos debido a los pretratamientos físico-químicos evaluados. Resultados previos obtenidos mediante RMN (Resonancia Magnética Nuclear) han demostrado que esta técnica permite caracterizar los productos resultantes de la rotura de las fibras de mascarillas incubadas en suelos [1]. En la actua