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The district of Arauca is the second-largest producer of cacao in Colombia. However, despite its quality, it faces issues for export due to levels of cadmium (Cd) higher than the regulatory thresholds. A central question is how it may impact agricultural performance in the presence of Cd in cacao and chocolates. This study quantified Cd in cacao plantations from Arauca. Thus, 180 farms were assessed in the municipalities of Arauquita, Fortul, Saravena, and Tame. Five sample types (soil, irrigation channel sediment, soil litter, cacao seeds, and chocolates) were assessed for Cd. As a technological innovation, the new MXRF technology was used for Cd in chocolates. The sequence of Cd content was soil litter > chocolate > soils > cacao seeds > irrigation-channel sediment. A gradient north-south of Cd content in soil was observed, where highest content was found in farms near the Arauca River, and lower farther away. In irrigation channel sediment, Cd levels averaged 0.07 mg kg-1. The Cd content in cacao seeds was 0.78 mg kg-1 on average. Cd content in chocolates was above the threshold (1.10 mg kg-1 on average, including several cacao mass percentages). These artisanal chocolate bars produced by single farms were near the limit of Cd set by the European Union (up to 0.8 mg kg-1). Therefore, mixing beans from different farms could reduce their Cd content. The present study underscores the complexity of Cd distribution, emphasizing the importance of integrating soil, crop, and landscape features in managing and mitigating Cd levels in cacao.

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Plant development and productivity depend on interactions with soil microorganisms for nutrient availability, promotion of growth and protection against phytopathogens. Although the influence of the phenological stages of soybean crops and their environmental conditions on the soil bacterial communities have already been reported, no studies have focused on the influence of integrated agrosilvopastoral systems on bacterial consortia. In this study, we evaluated the influence of the phenological stages of soybean cultivated under conventional full sunlight (CFS) and integrated crop-livestock-forestry (ICLF) systems on bacterial communities in the rhizosphere and in bulk soil using high-throughput sequencing techniques. Proteobacteria, Actinobacteriota and Acidobacteriota were the most abundant phyla in both the rhizosphere and the bulk soil at all growth stages. The results support our hypotheses that the richness and diversity of soil bacterial communities are influenced by different cultivation systems, and that the structure of the bacterial communities in the rhizosphere and the bulk soil are modulated by the phenological stages of the soybean crop.

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High Andean wetlands, particularly those known as vegas or bofedales, are essential conservation ecosystems due to their significant contribution to ecosystem services. The soil microbial communities in these ecosystems play a crucial role in fundamental processes such as decomposition and nutrient cycling, sustaining life in the region. However, at present, these microbial communities are poorly understood. In order to contribute to this knowledge, we aimed to characterize and compare the microbial communities from soils of seven Argentine Puna vegas and to analyze their association with soil physicochemical characteristics. Proteobacteria (Gamma and Alphaproteobacteria) was the dominant phylum across all vegas, followed in abundance by Actinobacteriota, Desulfobacterota, and Chloroflexi. Furthermore, the abundance of specific bacterial families and genera varied significantly between the vegas; some of them can be associated with plant growth-promoting bacteria such as Rhodomicrobium in La Quebradita and Quebrada del Diablo, Bacillus in Antofalla and Las Quinuas. Laguna Negra showed no shared ASVs with abundance in genera such as Sphingomonas and Pseudonocardia. The studied vegas also differed in their soil physicochemical properties; however, associations between the composition of microbial communities with the edaphic parameters measured were not found. These results suggest that other environmental factors (e.g., geographic, climatic, and plant communities' characteristics) could determine soil microbial diversity patterns. Further investigations are needed to be focused on understanding the composition and function of microorganisms in the soil associated with specific vegetation types in these high-altitude wetlands, which will provide valuable insights into the ecological dynamics of these ecosystems for conservation strategies.

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La espectroscopía de reflectancia en el infrarrojo cercano (NIRS) es una tecnología rápida, multiparamétrica, amigable con el ambiente, de bajo costo y gran exactitud, para el análisis de diversos componentes en alimentos, en suelo y en agricultura. El objetivo del presente estudio fue construir modelos de calibración NIRS, para la predicción de nutrientes en tejido vegetal de caña de azúcar, para producción de panela, cultivada en la región de la Hoya del río Suárez. Un total de 416 muestras de tejido fueron escaneadas en el segmento espectral Vis-NIR. El análisis quimiométrico, se realizó con el software WinISI V4.10, aplicando la regresión de mínimos cuadrados parciales modificados, junto a una validación cruzada. Se evaluaron cuatro modelos con diferentes tratamientos matemáticos y el rendimiento de las calibraciones, se hizo por medio de la validación externa, analizando las medidas de bondad de ajuste, como el coeficiente de determinación de la predicción, el error estándar de la predicción ajustado por el sesgo y la desviación predictiva residual. Los resultados muestran que el modelo de calibración para N presentó el mayor poder predictivo. Para macronutrientes, las calibraciones, con mayor poder predictivo, fueron P y K y para micronutrientes, el modelo para B, mientras que para Cu presentó el más bajo poder predictivo. Se encontraron modelos adecuados para la predicción de los contenidos de N, Ca y P; para los demás nutrientes, se recomienda ampliar el conjunto de calibración.

Near Infrared Reflectance Spectroscopy (NIRS) is a fast, multiparametric, environmentally friendly, low-cost, and highly accurate technology for the analysis of components in food, soil, and agriculture. The purpose of this study was to generate NIRS calibration models for the prediction of nutrients in plant tissue of sugarcane to panela production cultivated in the Hoya del Río Suárez region. A total of 416 tissue samples were scanned in Vis-NIR spectral segment. Chemometric analysis was performed with the WinISI V4.10 software applying modified partial least squares regression with cross-validation. Four models with different mathematical treatments were evaluated, and the performance of calibrations was made through external validation analyzing the goodness-of-fit measures as prediction determination coefficient, standard error of the bias-adjusted prediction, and residual predictive deviation. The results showed that the calibration model for N had the highest predictive power. For macronutrients, the calibrations with the best predictive power were for P and K, and micronutrients for B, while Cu presented the lowest predictive power. Adequate models were found for the prediction of N, Ca, and P. In the case of the other nutrients, it is recommended to expand the calibration set.

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In recent years, the release of metal and metallic oxide engineered nanoparticles (ENPs) into the environment has generated an increase in their accumulation in agricultural soils, which is a serious risk to the ecosystem and soil health. Here, we show the impact of ENPs on the physical and chemical properties of soils. A literature search was performed in the Scopus database using the keywords ENPs, plus soil physical properties or soil chemical properties, and elements availability. In general, we found that the presence of metal and metallic oxide ENPs in soils can increase hydraulic conductivity and soil porosity and reduce the distance between soil particles, as well as causing a variation in pH, cation exchange capacity (CEC), electrical conductivity (EC), redox potential (Eh), and soil organic matter (SOM) content. Furthermore, ENPs or the metal cations released from them in soils can interact with nutrients like phosphorus (P) forming complexes or precipitates, decreasing their bioavailability in the soil solution. The results depend on the soil properties and the doses, exposure duration, concentrations, and type of ENPs. Therefore, we suggest that particular attention should be paid to every kind of metal and metallic oxide ENPs deposited into the soil.

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No-till (NT) as a conservation practice aims to minimize soil disturbance and enhance soil sustainability. However, how NT practice affects soil physicochemical and biological properties in soybean areas remains unclear. This study selected 65 high-yielding soybean farms under a long-term NT system in the Brazilian Cerrado and collected soil samples at 0.0-0.10 m (L1), 0.10-0.20 m (L2) and 0.20-0.40 m (L3) depths. The effect of NT on soil properties and interactions with soybean productivities were assessed. Results showed that the average soybean yield of the study areas in the last three years was 4.13 Mg ha-1, with 26 areas presenting yields over 4.20 Mg ha-1. Most studied soil properties showed a depth stratification and were strongly concentrated in L1, except for S, Al3+ and aluminum saturation, which displayed lower surface and higher subsurface concentrations. Moreover, a high proportion of SOM is composed of light SOM fraction in areas of high soybean yield, with the average SOM values of 39.9, 27.8 and 19.6 g kg-1 in L1, L2 and L3, respectively. Soils under long-term NT present moderate values of enzyme activity compared with the relatively low values under conventional tillage system, especially 94 % of the plots have moderate values of activity of arylsulfatase enzymes. The data presented support the conclusion that NT system can enhance soil fertility and biological quality in soybean cultivation. Our results suggest that it is necessary to adopt NT practice because it allows increasing soybean productivity in Brazil without the need to increase the sown area, in addition to increasing productivity associated with an improvement in the agroecosystem quality, thus moving toward a more sustainable agriculture.

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The sustainable management of water and soil resources for agricultural purposes is related to the ability to store and mobilize available water for crops, particularly under a spatial analysis. The objective of the study was to design and evaluate a methodology for spatial analysis of resistance to soil penetration and infiltration on loamy-clay textures. The basic methodological principles included sampling grid planning, data capture at defined points, data fitting to empirical models, data processing, and spatial representation. A defining moment was evaluated for an established feijoa crop with permanent production. With a georeferenced rectangular sampling grid of 40m x 40m, an area of 1.36 ha was covered. Penetration resistance was measured with a penetrometer, covering 4 depths per node (sampled point). Infiltration was evaluated with ring infiltrometers. The results allowed validation of the methodology implemented through a single processing environment through RStudio. Resistance to penetration sensitively affected the variation in infiltration rates, adjusting planning activities for irrigation activities. The methodological proposal was designed to reduce processing times and graphic responses, tabulated, and integrated with a single script in the R tool, compared to traditional geostatistical techniques, which articulate the implementation of multiple tools for the generation of results.

La gestión sostenible de los recursos agua y suelo, con fines agrícolas, tiene relación con la capacidad para almacenar y movilizar agua disponible para los cultivos, particularmente, bajo un análisis espacial. El objetivo del estudio fue diseñar y evaluar una metodología de análisis espacial de la resistencia a la penetración e infiltración del suelo sobre texturas franco-arcillosas. Los principios básicos metodológicos incluyeron planificación de grilla de muestreo, captura de datos en puntos definidos, ajuste de datos a modelos empíricos, procesamiento y representación espacial de datos. Se evaluó un momento definido para un cultivo de feijoa establecido con producción permanente. Con una grilla de muestreo rectangular georreferenciada de 40m x 40m, se abarcó una superficie de 1,36 ha. La resistencia a penetración, se midió con un penetrómetro, cubriendo 4 profundidades por nodo (punto muestreado). La infiltración fue evaluada con anillos infiltrómetros. Los resultados permitieron validar la metodología implementada, mediante un entorno de procesamiento único, a través de RStudio. La resistencia a la penetración afectó sensiblemente la variación en las tasas de infiltración, ajustando actividades de planeación de actividades de riego. La propuesta metodológica fue diseñada para disminuir tiempos de procesamiento y respuestas gráficas, tabuladas e integradas en un único script en la herramienta R, comparado con técnicas tradicionales geoestadísticas, que articulan la implementación de múltiples herramientas para la generación de resultados.

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Open-cast iron mining causes drastic disturbances in soil properties. Recovery of soil chemical and physical properties is essential for successful revegetation and landscape rehabilitation. To identify changes in soil properties during the mining and revegetation process, soil samples were collected from undisturbed sites represented by forest and ferriferous savannas stocking above iron outcrops, called "cangas," in open-pit benches, and in rehabilitation chronosequences of iron waste piles in the Carajás Mineral Province (CMP), Eastern Amazon, Brazil. The samples were analyzed for chemical and physical properties. Our results showed that iron mining operations resulted in significant alteration of the chemical soil properties when forest and canga vegetation are suppressed to form open-pit benches or waste piles in the CMP. Mining substrates showed lower contents of soil organic matter (SOM) and nutrients than undisturbed areas of forests and cangas. In order to achieve the success of revegetation, nutrients have been added prior to plant establishment. We have demonstrated how soil fertility changes along with mineland rehabilitation, and the variation among chronosequence was attributable mainly due to contents of SOM, K, and B in the soil. The slight improvement of SOM found in rehabilitated waste piles reinforces the notion that recovery of soil quality can be a slow process in iron minelands in the CMP.

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RESUMEN La acidez del suelo limita la disponibilidad, la absorción y la concentración de nutrientes y el rendimiento del cultivo de cacao. El objetivo fue evaluar el efecto del pH del suelo sobre la concentración de nutrientes en hoja, cáscara y grano, para cuatro clones de cacao autocompatibles (ICS-1, CCN-51) y autoincompatibles (ICS-39, TSH-565), en el departamento del Caquetá. El diseño experimental consistió en un arreglo factorial con cuatro clones (factor A), cuatro niveles de pH y fertilidad (factor B) y cuatro repeticiones. Los resultados indican diferencias en la concentración de nutrientes por efecto del clon y tratamiento, siendo la acumulación de N, P y Mg en grano>hoja>cáscara, K en cáscara>hoja>grano, Ca, Fe, Mn, Zn y B en hoja>cáscara>grano, S en cáscara>hoja>grano y Cu en grano>cáscara>hoja. La concentración de P, Mg y S fue mayor y, a su vez, menor Mn, cuando aumentó el pH. El orden de extracción nutrimental en grano fue N>K>P>Mg>S>Ca>Fe>Mn>Zn>Cu>B. Con relación a los clones, CCN-51 presentó habilidad para la toma de nutrientes y alcanzar mayores producciones, incluso, en suelos con pH ≥ 5,5, lo que sugiere efecto de las condiciones edafoclimáticas y, por lo tanto, la necesidad de evaluar los clones para cada zona de cultivo.

ABSTRACT The soil acidity limits availability, absorption and concentration of nutrients and yield of the cocoa crop. The objective was to evaluate the effect of soil pH on the concentration of macro and micronutrients in leaf, husk and grain for four cocoa clones, self-compatible (ICS-1, CCN-51) and self-incompatible (ICS-39, TSH-565) in the department of Caquetá. The experimental design consisted in a factorial arrangement with four clones (factor A), four pH and fertility levels (factor B) and four repetitions. The results indicate differences in the concentration of nutrients due to the effect of the clone and the treatment, being the accumulation of N, P and Mg in grain>leaf>husk, K in husk>leaf>grain, Ca, Fe, Mn, Zn y B in leaf>husk>grain, S in husk>leaf>grain and Cu in grain>husk>leaf. The concentration of P, Mg and S was higher, and in turn Mn lower, when the pH increased. The order of nutrient extraction in grain was N>K>P>Mg>S>Ca>Fe>Mn>Zn>Cu>B. Regarding clones, CCN-51 showed ability to take nutrients and reach higher productions, even in soils with pH ≥ 5.5, suggesting effect of edaphoclimatic conditions, and therefore, the need to evaluate the clones for each growing area.

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Soil ecosystem service (SES) approaches evidence the importance of soil for human well-being, contribute to improving dialogue between science and decision-making and encourage the translation of scientific results into public policies. Herein, through systematic review, we assess the state of the art of SES approaches in tropical regions. Through this review, 41 publications were identified; while most of these studies considered SES, a lack of a consistent framework to define SES was apparent. Most studies measured soil natural capital and processes, while only three studies undertook monetary valuation. Although the number of publications increased (from 1 to 41), between 2001 and 2019, the total number of publications for tropical regions is still small. Countries with the largest number of publications were Brazil (n = 8), Colombia (n = 6) and Mexico (n = 4). This observation emphasizes an important knowledge gap pertaining to SES approaches and their link to tropical regions. With global momentum behind SES approaches, there is an opportunity to integrate SES approaches into policy and practice in tropical regions. The use of SES evaluation tools in tropical regions could transform how land use decisions are informed, mitigating soil degradation and protecting the ecosystems that soil underpins.

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Conventional tillage and mineral fertilization (CTMF) jeopardize soil health in conventional vegetable production systems. Using a field experiment established in Uruguay in 2012, we aimed to compare the soil restoration potential of organic fertilization (compost and poultry manure) combined with conventional tillage and cover crop incorporated into the soil (CTOF) or with reduced tillage and the use of cover crop as mulch (RTOF). In 2017, table beet was cultivated under CTMF, CTOF and RTOF, and yields, soil aggregate composition and nutrients, as well as soil and table beet rhizosphere microbiota (here: bacteria and archaea) were evaluated. Microbiota was studied by high-throughput sequencing of 16S rRNA gene fragments amplified from total community DNA. RTOF exhibited higher soil aggregation, soil organic C, nutrient availability and microbial alpha-diversity than CTMF, and became more similar to an adjacent natural undisturbed site. The soil microbiota was strongly shaped by the fertilization source which was conveyed to the rhizosphere and resulted in differentially abundant taxa. However, 229 amplicon sequencing variants were found to form the core table beet rhizosphere microbiota shared among managements. In conclusion, our study shows that after only 5 years of implementation, RTOF improves soil health under intensive vegetable farming systems.

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Restoring forest ecosystems has become a global priority. Yet, soil dynamics are still poorly assessed among restoration studies and there is a lack of knowledge on how soil is affected by forest restoration process. Here, we compile information on soil dynamics in forest restoration based on soil physical, chemical, and biological attributes in temperate and tropical forest regions. It encompasses 50 scientific papers across 17 different countries and contains 1,469 points of quantitative information of soil attributes between reference (e.g., old-growth forest) and restored ecosystems (e.g., forests in their initial or secondary stage of succession) within the same study. To be selected, studies had to be conducted in forest ecosystems, to include multiple sampling sites (replicates) in both restored and reference ecosystems, and to encompass quantitative data of soil attributes for both reference and restored ecosystems. We recorded in each study the following information: (1) study year, (2) country, (3) forest region (tropical or temperate), (4) latitude, (5) longitude, (6) soil class, (7) past disturbance, (8) restoration strategy (active or passive), (9) restoration age, (10) soil attribute type (physical, chemical, or biological); (11) soil attribute, (12) soil attribute unit, (13) soil sampling (procedures), (14) date of sampling, (15) soil depth sampled, (16) soil analysis, (17) quantitative values of soil attributes for both restored and reference ecosystems, (18) type of variation (standard error of deviation) for both restored and reference ecosystems, and (19) quantitative values of the variation for both restored and reference ecosystems. These were the most common data available in the selected studies. This extensive database on the extent soil physical, chemical, and biological attributes differ between reference and restored ecosystems can fill part of the existing gap on both soil science and forest restoration in terms of (1) which are the critical soil attributes to be monitored during forest restoration? and (2) how do environmental factors affect soil attributes in forest restoration? The data will be made available to the scientific community for further analyses on both soil science and forest restoration. Soil information gaps during the forest restoration process and their general patterns can be addressed using this data set. There are no copyright or proprietary restrictions.

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Spiders are part of the soil biodiversity, considered fundamental to the food chain hierarchy, directly and indirectly influencing several services in agricultural and forest ecosystems. The present study aimed to evaluate the biodiversity of soil spider families and identify which soil properties influence their presence, as well as proposing families as potential bioindicators. Native forest (NF) and reforested sites (RF) with Araucaria angustifolia (Bertol.) Kuntze were evaluated in three regions of the state São Paulo, both in the winter and summer. Fifteen soil samples were collected from each forest to evaluate the biological (spiders and microbiological), chemical and physical soil properties, in addition to properties of the litter (dry matter and C, N and S contents). For soil spiders, two sampling methods were used: pitfall traps and soil monoliths. In total, 591 individuals were collected, and distributed in 30 families, of which 306 individuals (22 families) came from pitfall traps and 285 individuals (26 families) from monoliths. Only samples obtained by the monolith method revealed seasonal differences in the mean density and richness of spiders between NF and RF. Canonical discriminant analysis showed the separation of these forests of Araucaria. Principal Component Analysis demonstrated the correlation of a number of spider families with certain soil properties (organic carbon, basal respiration, metabolic quotient, litter carbon, total porosity, bulk density and soil moisture). We identified 10 families (Anapidae, Corinnidae, Dipluridae, Hahniidae, Linyphiidae, Lycosidae, Nemesiidae, Palpimanidae, Salticidae, Scytodidae) that contributed most to separating native forest from the replanted forest, indicating the possibility of the spiders being used as bioindicators.

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Spiders are part of the soil biodiversity, considered fundamental to the food chain hierarchy, directly and indirectly influencing several services in agricultural and forest ecosystems. The present study aimed to evaluate the biodiversity of soil spider families and identify which soil properties influence their presence, as well as proposing families as potential bioindicators. Native forest (NF) and reforested sites (RF) with Araucaria angustifolia (Bertol.) Kuntze were evaluated in three regions of the state São Paulo, both in the winter and summer. Fifteen soil samples were collected from each forest to evaluate the biological (spiders and microbiological), chemical and physical soil properties, in addition to properties of the litter (dry matter and C, N and S contents). For soil spiders, two sampling methods were used: pitfall traps and soil monoliths. In total, 591 individuals were collected, and distributed in 30 families, of which 306 individuals (22 families) came from pitfall traps and 285 individuals (26 families) from monoliths. Only samples obtained by the monolith method revealed seasonal differences in the mean density and richness of spiders between NF and RF. Canonical discriminant analysis showed the separation of these forests of Araucaria. Principal Component Analysis demonstrated the correlation of a number of spider families with certain soil properties (organic carbon, basal respiration, metabolic quotient, litter carbon, total porosity, bulk density and soil moisture). We identified 10 families (Anapidae, Corinnidae, Dipluridae, Hahniidae, Linyphiidae, Lycosidae, Nemesiidae, Palpimanidae, Salticidae, Scytodidae) that contributed most to separating native forest from the replanted forest, indicating the possibility of the spiders being used as bioindicators.(AU)

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Spiders are part of the soil biodiversity, considered fundamental to the food chain hierarchy, directly and indirectly influencing several services in agricultural and forest ecosystems. The present study aimed to evaluate the biodiversity of soil spider families and identify which soil properties influence their presence, as well as proposing families as potential bioindicators. Native forest (NF) and reforested sites (RF) with Araucaria angustifolia (Bertol.) Kuntze were evaluated in three regions of the state São Paulo, both in the winter and summer. Fifteen soil samples were collected from each forest to evaluate the biological (spiders and microbiological), chemical and physical soil properties, in addition to properties of the litter (dry matter and C, N and S contents). For soil spiders, two sampling methods were used: pitfall traps and soil monoliths. In total, 591 individuals were collected, and distributed in 30 families, of which 306 individuals (22 families) came from pitfall traps and 285 individuals (26 families) from monoliths. Only samples obtained by the monolith method revealed seasonal differences in the mean density and richness of spiders between NF and RF. Canonical discriminant analysis showed the separation of these forests of Araucaria. Principal Component Analysis demonstrated the correlation of a number of spider families with certain soil properties (organic carbon, basal respiration, metabolic quotient, litter carbon, total porosity, bulk density and soil moisture). We identified 10 families (Anapidae, Corinnidae, Dipluridae, Hahniidae, Linyphiidae, Lycosidae, Nemesiidae, Palpimanidae, Salticidae, Scytodidae) that contributed most to separating native forest from the replanted forest, indicating the possibility of the spiders being used as bioindicators.

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RESUMEN Los sistemas de producción agrícolas en la subregión Valle del Sinú, en Colombia, en los últimos 50 años, se han basado en la siembra de cultivos en rotación o alternancia de maíz - algodón y arroz, y se caracterizan por el uso intensivo de implementos de mecanización e insumos agrícolas. El objetivo de este estudio fue evaluar las características fisicoquímicas de los suelos, bajo los sistemas productivos de maíz - algodón y arroz e identificar las principales limitantes de suelo, que afectan el desarrollo y la productividad de los cultivos, en la subregión Valle del Sinú. Para lo anterior, se realizaron muestreos de suelo en 64 sitios, distribuidos en cinco municipios del Valle del Sinú, evaluando propiedades físicas y químicas del suelo. El suelo en estudio pertenece al orden Inceptisol, moderadamente profundo, compuesto por arcillas expansivas y horizonte argílico. El suelo, se caracterizó por una reacción acida (5,82±0,87 a 6,78±0,34), contenido medio de MO. La media de la CIC varió en rango, de 18,45±2,94 a 22,85±4,36cmol(+) kg-1, la CE estuvo no salinos, variando de 0,29±0,09 a 0,91±1,70dS cm-1. Los contenidos de P, S, Ca, Mg y K fueron altos. La densidad aparente mostró valores promedios restrictivos para el desarrollo de raíces en cuatro de los cinco municipios, variando de 1,42±0,10 a 1,49±0,08g cm-3, excepto en San Carlos (1,33±0,14g cm-3). Los resultados obtenidos evidencian indicios de procesos de degradación de suelo, relacionados con el manejo de los suelos.

ABSTRACT The agricultural production systems in the Valle del Sinú subregion in Colombia, in the last 50 years, have been based on the sowing of crops in rotation and / or alternation of corn - cotton and rice, and are characterized by the intensive use of implements mechanization and agricultural inputs. The aim of this study was to evaluate the physicochemical characteristics of the soils under the corn - cotton and rice production systems and identifying the main soil limitations, which affect crop development and productivity, in the Sinú Valley Subregion. For the above, soil sampling was carried out at 64 sites distributed in five municipalities of the Sinú Valley, evaluating the physical and chemical properties of the soil. The soil under study belongs to the order Inceptisol, moderately deep, composed of expansive clays and argillic horizons. The soil was characterized by an acid reaction (5.82 ± 0.87 to 6.78 ± 0.34), average MO content. The mean of the CIC varied in the range of 18.45 ± 2.94 to 22.85 ± 4.36cmol(+) kg-1, the EC was not saline, varying from 0.29 ± 0.09 to 0.91 ± 1.70dS cm-1. The contents of P, S, Ca, Mg and K were high. The apparent density showed restrictive average values for root development in four of the five municipalities, ranging from 1.42 ± 0.10 to 1.49 ± 0.08g cm-3, except in San Carlos (1.33 ± 0.14g cm-3). The results obtained show evidence of soil degradation processes related to soil management.

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Arsenic is a ubiquitous, toxic element that is efficiently accumulated by rice plants. This study assessed the spatial variability in the total As (tAs) contents and organic and inorganic forms in different types of rice, plant parts (husk, stem, leaves and phytoliths) and residues. Samples were collected in different countries in Latin America (Ecuador, Brazil and Peru) and the Iberian Peninsula (Spain and Portugal). The tAs content in commercial polished rice from the Latin American countries was similar (0.130-0.166 mg kg-1) and significantly lower than in the rice from the Iberian countries (0.191 ± 0.066 mg kg-1), and together, the tAs concentration in brown rice (236 ± 0.093 mg kg-1) was significantly higher than in polished and parboiled rice. The inorganic As (iAs) content in rice was similar in both geographical regions, and the aforementioned difference was attributed to dimethylarsinic acid (DMA). The relative abundance of organic species increased as the tAs content in rice grain increased. A meta-analysis of our and previously reported data confirmed the negative correlation between iAs/tAs and tAs. At low tAs concentrations, inorganic forms are dominant, while at higher values (tAs > 0.300 mg kg-1) the concentration of organic As increases substantially and DMA becomes the dominant form in rice grain. On the contrary, inorganic arsenic was always the dominant form, mainly as arsenate [As(V)], in leaves and stems. The presence in soils of high concentrations of amorphous Fe and Al oxides and hydroxides, which are capable of strongly adsorbing oxyanions (i.e. arsenate), was associated with low concentrations of As in rice plants. In addition, the presence of high concentrations of As(V) in stems and leaves, low concentration of As in phytoliths, and the As associated with organic matter in stems and husk, together suggest that rice plants take up more As(V) than As(III).

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This study evaluated the concentration and distribution of heavy metals (HM) (Cr, Ni, Pb, Cd, Hg, and Zn) and pesticides (organochlorine and organophosphorus) and the relationship of these pollutants with the physicochemical properties of agricultural soils in an Irrigation District (ID) in Colombia. Soils samples were analyzed for pH, humidity, organic matter, P total, N total, electric conductivity (EC), cation exchange capacity, and texture (% sand, clay and silt). Canonical correlation was used to determined relationship between soil properties and HM. Soil pollution were evaluated with geoaccumulation index (Igeo), contamination factor (CF), degree of contamination (Cdeg) and pollution load index (PLI). The results indicated that, in general, the soils had adequate physicochemical conditions for the establishment and development of crops. The presence of pesticides in the soils was not reported. However, concentrations HM was detected (Zn > Cr > Ni > Pb > Hg > Cd). The soil characteristics (silt, clay, pH and EC) contributed to explain HM concentrations. The Igeo indicated that the soils are heavily contaminated with Hg (3 < Igeo<4). The CF was very high for Hg (>6). The Cdeg presented moderate to considerable variations (>6Cdeg<24). The PLI indicated that the soils are contaminated (1.308). The presence of HM may be associated with the agricultural and quarries activities carried out near the ID. The impact caused by high concentrations of HM can lead environmental, economic and social impacts in the study zone.

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BACKGROUND: A great number of studies have shown that the distribution of microorganisms in the soil is not random, but that their abundance changes along environmental gradients (spatial patterns). The present study examined the spatial variability of the physicochemical characteristics of an extreme alkaline saline soil and how they controlled the archaeal and bacterial communities so as to determine the main spatial community drivers. METHODS: The archaeal and bacterial community structure, and soil characteristics were determined at 13 points along a 211 m transect in the former lake Texcoco. Geostatistical techniques were used to describe spatial patterns of the microbial community and soil characteristics and determine soil properties that defined the prokaryotic community structure. RESULTS: A high variability in electrolytic conductivity (EC) and water content (WC) was found. Euryarchaeota dominated Archaea, except when the EC was low. Proteobacteria, Bacteroidetes and Actinobacteria were the dominant bacterial phyla independent of large variations in certain soil characteristics. Multivariate analysis showed that soil WC affected the archaeal community structure and a geostatistical analysis found that variation in the relative abundance of Euryarchaeota was controlled by EC. The bacterial alpha diversity was less controlled by soil characteristics at the scale of this study than the archaeal alpha diversity. DISCUSSION: Results indicated that WC and EC played a major role in driving the microbial communities distribution and scale and sampling strategies were important to define spatial patterns.

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Amazon rainforest has been subjected to particularly high rates of deforestation caused mainly by the expansion of cattle pasture and agriculture. A commonly observed response to land-use change is a negative impact on biodiversity of plant and animal species. However, its effect on the soil microbial community and ecosystem functioning is still poorly understood. Here, we used a DNA metagenomic sequencing approach to investigate the impact of land-use change on soil microbial community composition and its potential functions in three land-use systems (primary forest, pasture and secondary forest) in the Amazon region. In general, the microbial community structure was influenced by changes in soil physicochemical properties. Aluminum and water-holding capacity significantly correlated to overall community structure and most of microbial phyla. Taxonomic changes were followed by potential functional changes in the soil microbial community, with pasture presenting the most distinct profile in comparison with other sites. Although taxonomic structure was very distinct among sites, we observed a recovery of the potential functions in secondary forest after pasture abandonment. Our findings elucidate a significant shift in belowground microbial taxonomic and potential functional diversity following natural forest re-establishment and have implications for ecological restoration programs in tropical and sub-tropical ecosystems.

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