Abstract Phytoliths are plant micro-remains found in soils and sediments. Their durability, abundance and diagnostic morphologies make them reliable environmental proxies, especially when associated with other biological, chemical, or physical indicators. However, in some cases, phytoliths are the only biological proxy available on the soil for paleoenvironmental studies, therefore, it requires extra attention to taphonomic processes affecting these silica bodies’ assemblage. The preservation and conservation of this markers in the soil is directly linked to the edaphic conditions to which it is subjected over time. Hence, the application of this proxy requires care in order to avoid misinterpretations, since phytoliths are subject to degradation and movement within the soil due to soil-plant-water interactions, soil hydrological processes a/nd bioturbation. In this article we examine the diversity and taphonomic evidence found in an Oxisol’s phytolith assemblage in search to better our understanding of this silica bodies preservation in tropical soils. The result shows that the assembly found is very resistant to tropical edaphic conditions, displaying taphonomic signs such as breakage and corrosion across the profile, with significant increase with depth, pointing to the phytolith’s early deposition. Also, results suggest that Grass Silica Short Cell Phytolith tend to present more breakage than corrosion due to its smaller size when compared to bigger morphotypes, which have corrosion features more often. microremains micro remains sediments durability proxies chemical indicators However cases studies therefore time Hence misinterpretations soilplantwater water interactions a nd bioturbation Oxisols Oxisol s profile depth deposition Also morphotypes often

Resumo A erosão hídrica é uma das principais causas da degradação das terras agricultáveis brasileiras, levando à diminuição da produtividade das culturas e à acidificação do solo, prejudicando sua capacidade de armazenar carbono, nutrientes e água. O manejo inadequado do solo é um dos principais responsáveis por esse tipo de degradação. A identificação da intensidade da erosão pode ser feita por meio da utilização de atributos indicadores que são altamente sensíveis as mudanças no ambiente edáfico. O estudo teve como objetivos: i) analisar os atributos físicos e químicos do solo em áreas de voçorocas com diferentes graus de degradação/estabilização; e ii) verificar a viabilidade de utilização desses atributos como indicadores de recuperação ambiental. O estudo foi realizado em quatro áreas com diferentes graus de formação de voçorocas: a) inicial, intermédia, madura e senil. As amostras foram coletadas nas faces externa e interna de cada voçoroca no final da estação seca. Entre os atributos físicos avaliados, a densidade do solo e a porosidade total foram os mais significativamente alterados. A avaliação dos microagregados permitiu conhecer a qualidade do solo através de frações como a argila dispersável em água, a argila refloculável em água e a argila não dispersível em água. O carbono total, o nitrogênio total e a relação C/N elucidaram a dinâmica da perda de solo e de nutrientes em diferentes fases dos processos de formação e estabilização da erosão, com valores mais baixos observados na face interna das voçorocas em comparação a externa. Observou-se que a vegetação influenciou os resultados dos atributos físicos e químicos. No geral, os valores tenderam ao equilíbrio entre as faces na voçoroca SE, indicando maior estabilização. Com base nesses resultados, os atributos avaliados podem servir como indicadores de qualidade do solo, pois são mais eficientes e sensíveis em expressar a recuperação da qualidade física e química do solo, fornecendo informações valiosas para o monitoramento de processos de degradação e para a prevenção, controle e recuperação de voçorocas no Bioma Mata Atlântica. brasileiras edáfico objetivos i degradação/estabilização degradaçãoestabilização ii ambiental inicial intermédia senil seca alterados CN C N Observouse Observou se geral SE prevenção Atlântica

Abstract Water erosion is one of the primary causes of agricultural soil degradation in Brazil, leading to diminished crop productivity and soil acidification, thereby impairing its ability to store carbon, nutrients, and water. Identifying the intensity of erosion can be achieved by utilizing indicator attributes that are highly sensitive to changes in the edaphic environment. The study analyzed the physical and chemical attributes of soil in areas with gullies exhibiting varying degrees of degradation/stabilization. The study was conducted across four areas with varying degrees of gully formation: a) initial, intermediate, mature, and senile. Samples were collected from both the external and internal sides of each gully at the end of the dry season. Among the physical attributes assessed, soil density and total porosity were found to be the most significantly altered. Evaluation of microaggregates provided insights into soil quality through fractions including water-dispersible clay, water-reflocculable clay, and non-water-dispersible clay. Total carbon, total nitrogen, and the C/N ratio elucidated the dynamics of soil and nutrient loss across different stages of erosion formation and stabilization processes, with lower values observed on the internal side of the gullies compared to the exterior side. Vegetation was observed to influence the results of the physical and chemical attributes. Overall, the values tended towards equilibrium between the faces at the senile stage, indicating greater stabilization. Brazil acidification carbon nutrients water environment degradationstabilization degradation/stabilization a initial intermediate mature season assessed altered waterdispersible dispersible clay waterreflocculable reflocculable nonwaterdispersible non nitrogen CN C N processes Overall stage

Summary: Amphipterigyum adstringens “cuachalalate” is growing on degraded soils of the low deciduous forest of the coast of Oaxaca. Two objectives were carried out: 1. On cuachalalate: to define the vertical and horizontal population structure, to identify the dispersal pattern of the individuals, and observe the period of the phenological phases. 2. On the soil: to determinate the physical and chemical characteristics of the degraded Lithosol of San Pedro Mixtepec, Oaxaca, where cuachalalate is growing. In sites of 1000 m2 all cuachalalate individuals were registered. These were classified by growing stage (saplings, juveniles and trees). To analyze the size hierarchy, the horizontal and vertical structure of the cuachalalate populations was analyzed. The spatial dispersion of populations was estimated with the Morisita Index. Phenological events were recorded in the trees: foliation, female and male flowering, fruiting and defoliation, during one year (2017 rainy season to 2018 dry season). The cuachalalate presented lower (2.0 to 9.5 m) and upper (10.0 to 16.0 m) vertical structure; the horizontal structure showed that saplings and juveniles have diameters < 2.5 cm, and trees of 5 to 10 cm. The spatial distribution of the populations is aggregated. Flowering occurred during the rainy season, fruiting during rainy to dry season of next year, foliation from dry to rainy season of the same year and defoliation from rainy season to dry season of next year. Degraded lithosols tend to be eroded by runoff, are impermeable and hydrophobic. The piedmont soils have physical and chemical characteristics that highlight incipient accumulation processes, which anticipate a transition to an eutrophic regosol, a favorable soil for the persistence of the low deciduous forest.

Resumen: Amphypterigium adstringens “cuachalalate” crece en los suelos degradados de la selva baja de la costa de Oaxaca. Dos objetivos fueron llevados a cabo: 1. En cuachalalate: obtener la estructura poblacional vertical y horizontal, identificar el patrón de dispersión de los individuos y observar el periodo de las fases fenológicas. 2. En el suelo: determinar las características físicas y químicas del litosol degradado de San Pedro Mixtepec, Oaxaca, donde crece el cuachalalate. En sitios de 1000 m2 fueron registrados todos los individuos de cuachalalate. Éstos fueron clasificados por etapas de crecimiento (brinzal, latizal, fustal). Para analizar la jerarquía de tamaños de las poblaciones de cuachalalate se analizó la estructura horizontal y vertical. La dispersión espacial de las poblaciones fue estimada con el índice de Morisita. En los fustales se registraron los eventos fenológicos: foliación, floración femenina y masculina, fructificación y defoliación, durante un año (época lluviosa de 2017 a época seca de 2018). La estructura vertical de las poblaciones de cuachalalate presentó dos estratos: inferior (2.0 a 9.5 m) y superior (10.0 a 16.0 m); la estructura horizontal mostró que brinzales y latizales tienen diámetros < 2.5 cm y fustales de 5 a 10 cm. La distribución espacial de las poblaciones es agregada. La floración ocurrió durante la época lluviosa, la fructificación durante la época lluviosa a la seca del siguiente año, la foliación de la época seca a la lluviosa del mismo año, la defoliación de la época lluviosa a la seca del siguiente año. Los litosol degradados tienden a ser erosionados por escurrimiento, son impermeables e hidrófobos. Los suelos de piedemonte poseen características físicas y químicas que destacan procesos incipientes de acumulación, lo que anticipa transición hacia regosol éutrico, suelo favorable para la persistencia de la selva baja caducifolia.

Abstract Environmental conditions influence several ecological and phenological processes of plant species, such as dispersal, seed bank in the soil, and germination. The objective of the present study was to analyze the relationship between the abundance of adult individuals and seedlings, seed rainfall, germination rate, and survival of Abies hickelii regarding environmental conditions in the Sierra Norte Oaxaca, Mexico. We conducted vegetation sampling, placed traps for seed rain, collected seed banks in the soil, and quantified germination and survival. At each site, we measured environmental conditions (climatic, edaphic, topographic, and light). It was recorded that at the highest altitude site (3150 m), A. hickelii had a higher density of adults and seedlings and a higher percentage of germination compared to the lower altitude sites. The abundance of adult individuals and seedlings of A. hickelii is related to canopy openness and maximum rainfall intensity. Seed production is related to total annual precipitation, while germination and survival were not associated with any of the environmental variables analyzed. This study considered different aspects of the A. hickelii life cycle and its relationship with the environmental conditions where it was established, which allowed us to determine the most significant environmental variables in each growth stage. The results represent relevant information for endemic and endangered species.

Resumen Las condiciones ambientales influyen en varios procesos ecológicos y fenológicos de las especies vegetales, como la dispersión, el banco de semillas en el suelo y la germinación. El objetivo del presente estudio fue analizar la relación entre la abundancia de los individuos adultos y plántulas, la lluvia de semillas, la tasa de germinación y la supervivencia de Abies hickelii, con respecto a las condiciones ambientales en la Sierra Norte, Oaxaca, México. Se realizaron muestreos de vegetación, se colocaron trampas para la lluvia de semillas, se colectó el banco de semillas en el suelo y se cuantificó la germinación y su supervivencia. En cada sitio se midieron las condiciones ambientales (climáticas, edáficas, topográficas y lumínicas). Se registró que en el sitio de mayor altitud (3150 m), A. hickelii presentó mayor densidad de adultos y plántulas, y mayor porcentaje de germinación en comparación con los sitios de menor altitud. La abundancia de individuos adultos y plántulas de A. hickelii está relacionada con la apertura del dosel y la intensidad máxima de precipitación. La producción de semillas está relacionada con la precipitación total anual; mientras que la germinación y la supervivencia no se asociaron con ninguna de las variables ambientales analizadas. Este estudio consideró diferentes aspectos del ciclo de vida de A. hickelii y su relación con las condiciones del medio donde se establece, para conocer las variables ambientales más relevantes en cada etapa de su crecimiento. Esta información es relevante para especies endémicas y en peligro de extinción.

RESUMEN El algodón es un cultivo de gran importancia económica en todo el mundo. En Colombia las siembras han aumentado en los últimos años; no obstante, existen prácticas agronómicas que favorecen la degradación del suelo. El objetivo del trabajo fue evaluar la respuesta morfofisiológica y productiva de cuatro variedades de algodón, bajo el efecto de dos sistemas de labranza en condiciones de Armero-guayabal, Colombia. La investigación se realizó en el Centro Universitario Regional Norte (CURDN) de la Universidad del Tolima. El diseño experimental fue en parcelas subdivididas con bloques al azar con cuatro repeticiones. En la parcela principal se ubicó una labranza mínima (LM) y otra tradicional (LT) (reducida para LM usando arado de cincel y una labranza con volteo del suelo, con uso de rastra y rastrillo para LT). Las variedades manejadas fueron: RR, Nuopal RR, FM 9063 y FM9171Bt (Bacillus thuringiensis). Los resultados se sometieron al Análisis de Varianza (ANOVA) y pruebas de comparación de medias de Tukey y Bonferroni (p≤0,05). Los procesos de rotación de gramíneas y oleaginosas, en manejos agronómicos a largo plazo, presentan cambios significativos en la fertilidad potencial y efectiva edáfica, así como también, en los procesos de conservación, calidad y salud del suelo, en una zona históricamente con problemas edáficos en prácticas deficientes de laboreo.

ABSTRACT Cotton is a crop of great economic importance throughout the world. In Colombia, plantings have increased in recent years; however, there are agronomic practices that favor soil degradation. The objective of the work was to evaluate the morphophysiological and productive response of four cotton varieties, under the effect of two tillage systems under conditions of Armero-guayabal, Colombia. The research was conducted at the North Regional University Center (CURDN) of the University of Tolima. The experimental design was sub-divided plots with randomized blocks with four replications. In the main plot, a minimum tillage (LM) and a traditional one (LT) were located (reduced for LM using a chisel plow and tillage with soil turning, with the use of a harrow and a rake for LT). The varieties managed were: RR, Nuopal RR, FM 9063 and FM9171Bt (Bacillus thuringiensis). The results were submitted to the Analysis of Variance (ANOVA) and Tukey and Bonferroni tests for comparison of means (p≤0.05). The processes of rotation of grasses and oilseeds, in long-term agronomic management, present significant changes in the potential and effective edaphic fertility, as well as in the processes of conservation, quality and health of the soil, in an area historically with edaphic problems in poor tillage practices.

RESUMEN El aumento de los procesos de salinización de los suelos es una problemática de importancia debido al condicionamiento para la agricultura. En Argentina una zona susceptible se encuentra en el SE de la provincia de Córdoba. En la Pampa Húmeda, la principal fuente de sales es la napa freática. En el campo bajo estudio se localizan zonas marginales con presencia de sales en superficie. El objetivo del trabajo es evaluar el grado de salinización del ambiente e identificar especies viables para una futura fitorremediación, a través del estudio del comportamiento germinativo de especies tolerantes a ciertos rangos de salinidad. Se tomaron muestras de suelo y agua subterránea, en tres sub-ambientes del bajo salino. Se analizó conductividad eléctrica (CE) en pasta de saturación y pH1:2,5 en suelo, pH y CE del agua subterránea. Se realizaron ensayos de germinación con agua subterránea, con las especies: Festuca arundinacea, Thynopyrum ponticum, Lolium multiflorum, Hordeum vulgare y Chenopodium quinoa. Los suelos presentaron pH ligeramente alcalino y CE>2dS m-1, alcanzando valores extremos de 20,9dS m-1 en superficie; la napa freática utilizada estaba a 60 cm de profundidad, con una CE de16,8 dS m-1. La capacidad germinativa fue mayor al 80% para L. multiflorum, F. arundinacea y Ch. quinoa; H. vulgare igual a 67% y Th. Ponticum 50%. Se observó retraso en la germinación según un gradiente de concentraciones salinas. Para la recuperación del ambiente podría utilizarse una mezcla de L. multiflorum, F. arundinacea y Th. ponticum. En ambientes de alta salinidad Ch. quinoa resulta prometedora como especie productora de alimentos.

ABSTRACT The increase in the salinization processes of the soils is an important problem because it conditions agriculture. In Argentina, a susceptible zone is found in the SE of the province of Córdoba. In the Humid Pampa, the main source of salts is the groundwater. In the field under study, marginal areas with the presence of salts on the surface are located. The objective of this work is to evaluate the degree of salinization of the environment and identify viable species for future phytoremediation, through the study of the germinative behavior of species tolerant to certain ranges of salinity. Soil and groundwater samples were taken in three sub-environments of saline lowland soils. Electrical conductivity (EC) in saturation paste and pH1: 2.5 in soil, pH and EC of groundwater were analyzed. Germination tests were carried out with groundwater, using several species: Festuca arundinacea, Thynopyrum ponticum, Lolium multiflorum, Hordeum vulgare and Chenopodium quinoa. The soils presented slightly alkaline pH and EC>2 dS m-1, reaching extreme values of 20,9 dS m-1on the surface; groundwater used was at at 60 cm depth with EC = 16,8 dS m-1. The germination capacity was greater than 80% for L. multiflorum, F. arundinacea and Ch. Quinoa; equal to 67% and 50% for H. vulgare and Th. ponticum respectively. Germination delay was observed according to a gradient of salt concentrations. For the recovery of the environment investigated a mixture of L. multiflorum, F. arundinacea, and Th. ponticum could be used. In high salinity environments Ch. quinoa shows promising as a food-producing species.

RESÚMEN La piña es la tercera fruta tropical más producida a nivel mundial, sin embargo, es un cultivo que puede conllevar a la generación e intensificación de procesos como la erosión del suelo, debido a su forma de manejo. El artículo presenta una revisión bibliográfica acerca de los factores que inciden en la erosión en suelos dedicados al cultivo de la piña, abordando artículos reportados en la literatura internacional, posteriormente posicionándolo en el contexto de los principales municipios productores presentes en la región del Valle del Cauca. Las investigaciones disponibles abarcan las últimas cuatro décadas, donde se estimaron pérdidas entre 35 y 178ton. ha-1. año-1; la topografía, las condiciones de las vías de acceso, algunas prácticas de manejo, así como propiedades edáficas relacionadas con la erodabilidad se destacan entre los factores más importantes. Finalmente, a partir de las características climáticas, edafológicas y topográficas reportadas en literatura para los principales municipios productores de piña del Valle del Cauca, y considerando las actuales prácticas de manejo, se encuentra que esta zona puede presentar valores muy altos de erosión, ya que los suelos son susceptibles, y las pendientes son pronunciadas, algunas de ellas incluso superiores al 70%. Por lo tanto, se sugiere realizar más investigaciones que permitan determinar la erodabilidad y la erosividad de esas áreas, para conocer el índice de degradación potencial, que funcionará como una valiosa herramienta para la toma de decisiones, la generación de recomendaciones de manejo y conservación de estos suelos.

ABSTRACT Pineapple is the third most-produced tropical fruit worldwide; however, it is a crop that, due to its management, can lead to the generation and intensification of processes such as soil erosion. This paper presents a bibliographic review about the factors that influence erosion in soils dedicated to pineapple cultivation, addressing papers reported in the international literature, subsequently positioning it in the context of the main producing municipalities presented in the Valle del Cauca region. The available research covers the last four decades, where losses are estimated between 35 and 178t ha-1year-1; the topography, the conditions of the access roads, some management practices, and edaphic properties related to erodibility stand out among the most critical factors. Finally, based on the climatic, edaphological, and topographic traits reported in the literature for the main pineapple producing region of Valle del Cauca, and considering current management practices, it is found that this area can present very high erosion values since the soils are susceptible, and the slopes are steep, some of them even higher than 70%. Therefore, it is suggested to carry out more research to determine the erodibility and erosivity of these areas to know the potential degradation index, which will function as a valuable tool for decision-making, the generation of management, and conservation recommendations of these soils.

ABSTRACT Glyphosate, the most used herbicide worldwide, disrupts the synthesis of essential aromatic amino acids, eliminating sensitive plants. Its use has increased with the implementation of genetically modified crops that are tolerant to this herbicide and with its adoption as desiccant in some annual crops. Glyphosate, classified as probable carcinogen, has induced adverse effects to human health and has exerted selective pressure on plants resistant to this herbicide. Commercial formulations of glyphosate include molecules such as polyoxyethylenamines and heavy metals. There is no precise data on the amount of glyphosate used in Mexican agriculture, but it has been monitored in soils, rivers, seas, and the bodies of people directly or indirectly exposed to the herbicide in several countries. Glyphosate and its metabolite aminomethylphosphonic acid (AMPA) have low mobility in soils due to its high adsorption capacity. Its mobility and decomposition depend on the structure of soils, the amount and quality of the organic matter, temperature, pH, and type of clay, among other factors. Edaphic microbiota and glyphosate correlate on-to-one. Some bacterial species uses glyphosate as C and P source, metabolizing the herbicide, while, in presence of glyphosate other species change their fitness. Glyphosate alters the mycorrhization capacity of several fungi species, deregulates the expression of genes essential in processes such as amino acids’ metabolism or pathways related with detoxification. Glyphosate affects several species of worms, decreasing their ability to recycle organic matter. It is necessary to aim scientific research in agriculture to reducing the use of highly toxic and persistent agrichemicals.

RESUMEN El glifosato, que es el herbicida más usado mundialmente, interfiere en la síntesis de aminoácidos aromáticos esenciales, eliminando las plantas sensibles. Su uso aumentó al introducirse cultivos genéticamente modificados tolerantes al herbicida, y al usarse como desecante de cultivos anuales. El glifosato, clasificado como probable cancerígeno, ha generado efectos adversos en la salud humana y ha ejercido presión de selección generando plantas resistentes al herbicida. Las formulaciones comerciales contienen moléculas como polioxietilenaminas y metales pesados. En México no hay datos sobre la cantidad de glifosato empleado en la agricultura, pero se detectó en suelo, ríos y mares, así como en personas directa o indirectamente expuestas al herbicida. El glifosato y su metabolito ácido aminometilfosfónico (AMPA) tienen baja movilidad en los suelos por su alta capacidad de adsorción; su movilización y descomposición dependen de la estructura del suelo, cantidad y calidad de la materia orgánica, temperatura, pH, y tipo de arcilla, entre otros. La relación entre la microbiota edáfica y el glifosato es biunívoca: algunas especies bacterianas lo usan como fuente de C y P, degradando al herbicida, y otras sufren alteraciones adaptativas ante la exposición al glifosato. El herbicida altera la capacidad de micorrización de los hongos arbusculares y desregula la expresión de genes implicados en procesos como el metabolismo de los aminoácidos o vías relacionadas con detoxificación. Asimismo, afecta a diversas especies de lombrices del suelo, disminuyendo su capacidad de reciclar materia orgánica. Debe promoverse la investigación orientada a la producción agrícola sin el uso de agroquímicos altamente tóxicos y persistentes.

Resumen Introducción. Los procesos de degradación del suelo están asociados principalmente a malas prácticas y cambios en su uso. Generar indicadores que permitan conocer el estado del suelo es necesario para buscar alternativas que permitan mejorar la calidad del suelo. Objetivo. Evaluar algunos indicadores edáficos en diferentes sistemas de ganadería bovina tradicionales en el Caribe Colombiano. Materiales y métodos. Se colectaron muestras de suelo de 72 fincas por triplicado, para un total de 216 muestras, distribuidas en los 6 departamentos (Córdoba, Sucre, Bolívar, Atlántico, Cesar y Magdalena). Se evaluaron propiedades físicas y químicas del suelo con el fin de identificar los principales indicadores y construir los índices de calidad de suelo. Resultados. Se evidenciaron procesos de compactación en todas las fincas evaluadas, con valores de densidad aparente superiores a 1,4 g.cm-3, con predominio de texturas mediadas a finas (franco). Se encontraron valores de materia orgánica por encima de 2% en los departamentos de Córdoba (3,18±0,99%) y Bolívar (3,10±01,55%), contrario a lo identificado en Atlántico, Cesar y Magdalena con contenidos inferiores a 2%. La capacidad de intercambio catiónico efectivo (CICe) presentó valores superiores a 20 cmol(+).kg-1en la gran mayoría de los suelos evaluados, excepto los valores registrados en las fincas ubicadas en el departamento de Cesar. Los contenidos de P, S, Ca, Mg y K fueron altos en todas las fincas evaluadas. El índice de calidad del suelo está determinado por las propiedades químicas (pH, capacidad de intercambio catiónico y conductividad eléctrica). Conclusiones. Se reconocieron procesos de compactación relacionados con altos valores de densidad aparente y bajo contenido de poros totales. El manejo de suelo bajo los sistemas ganaderos es determinante en la cuantificación del índice de calidad de suelo.

Abstract Introduction. Soil degradation processes are mainly associated with poor management practices and changes in its use. Indicators that allow knowing the state of the soil is required to seek for alternatives that will help to improve soil quality. Objective. To evaluate some edaphic indicators in different traditional bovine livestock systems in the Colombian Caribbean. Materials and methods. Soil samples in triplicate were collected from 72 farms distributed in 6 departments (Cordoba, Sucre, Bolivar, Atlantico, Cesar and Magdalena), for a total of 216 samples. Soil physical and chemical properties were evaluated in order to identify the main indicators to develop a soil quality index. Results. Compaction processes were evident in all the evaluated farms with bulk density values higher than 1.4 g.cm-3with a predominance of medium to fine textures (loam). Organic matter values above 2% were found in the departments of Cordoba (3.18±0.99%) and Bolívar (3.10±01.55%), contrary to what was identified in Atlantico, Cesar, and Magdalena with contents below to 2%. The effective cation exchange capacity presented values higher than 20 cmol(+).kg-1in most of the soils, except for the values registered in the farms located in the department of Cesar. The contents of P, S, Ca, Mg and K were high in all the evaluated farms. Soil quality index is determined by the chemical properties (pH, cation exchange capacity and electrical conductivity). Conclusions. Compaction processes related to high bulk density values and low total pore content were recognized. Soil management under the livestock systems is decisive in the quantification of the soil quality index.

Abstract Nitrogen loss volatilization is one of the processes that may be greater depending on edaphic and climatic factors, it also depends on the source and the application method. This study was conducted at the farm El Plantel, owned by the Universidad Nacional Agraria, located at Masaya, Nicaragua. The objective of the study was to quantify the nitrogen losses due to volatilization and its influence on the yield of sorghum (Sorghum bicolor L.). Treatments consisted on two nitrogen fertilizers and two application methods. Treatments were as follow: 46% urea applied to the soil surface, urea incorporated into the soil, ammonium sulfate on the soil surface, and ammonium sulfate incorporated in soil. Nitrogen fertilization was carried out fractionally, 30 % (57 kg N ha-1) at planting and 70 % (133 kg N ha-1) 35 days after planting. The four treatments were set up in a randomized complete block design with three replications. Volatilization losses samplings were recorded on day one, three, six and nine after the first fertilization, and the second sampling was carried out in the same sequence from the second day after the second fertilization. An analysis of variance and mean separation were performed by less significant differences of Fisher 95 % using professional InfoStat 2009 programm. Volatilization losses are higher when urea is applied on the soil surface (57.68 kg N ha-1), reaching a cumulative loss of 43.37 %. Yields was statistically similar among the sources of nitrogen evaluated.

Resumen La volatilización es un proceso más de pérdida del nitrógeno, puede aumentar según factores edafoclimáticos, fuente y método de aplicación. Este estudio se realizó en la finca El Plantel, propiedad de la Universidad Nacional Agraria, ubicada en Masaya, Nicaragua. El objetivo fue cuantificar las pérdidas de nitrógeno por volatilización y su influencia en el rendimiento del cultivo de sorgo (Sorghum bicolor L.). Se evaluaron dos fertilizantes nitrogenados y dos métodos de aplicación en un diseño de bloque completo al azar con cuatro tratamientos y tres repeticiones. Los tratamientos fueron: urea 46 % aplicada en la superficie del suelo, urea incorporada al suelo, sulfato de amonio en la superficie y sulfato de amonio incorporado. La fertilización nitrogenada se realizó de manera fraccionada, 30 % (57 kg N ha-1) al momento de la siembra y 70 % (133 kg N ha-1) a los 35 días después de la siembra. Los muestreos de la volatilización se registraron los días uno, tres, seis y nueve después de la primera fertilización y el segundo en la misma secuencia a partir del segundo día después de la segunda fertilización. Se realizó un análisis de varianza y separación de medias por diferencias mínimas significativas de Fisher con 95 % de confiabilidad usando InfoStat profesional 2009. Las pérdidas por volatilización son mayores cuando se aplica urea en la superficie del suelo (57,68 kg N ha-1), lo que representa un 43,37 %. Los rendimientos son iguales al incorporar las fuentes nitrogenadas.

Natural areas of high biological diversity are being degraded to meet man's need to convert them to various uses. The ecological restoration through litter transposition enables for the reestablishment of ecological processes and may contribute to the increase of microorganisms. It aimed to evaluate the influence of litter on the community of mycorrhizal fungi in an area of Cabreúva, São Paulo State, Brazil. Ten plots were delimited, five control and five treatment. Soil samples were collected during two distinct periods for physical, chemical and microbiological analysis. Results indicated that the edaphic conditions of the place are consistent with the presence of AMF; also, the transposed organic matter did not increase species richness and did not facilitate the colonization of plant species, whereas gravimetric humidity and grass may have influenced species richness.

Áreas naturais de elevada diversidade biológica estão sendo degradadas para suprir a necessidade do homem em convertê-las em usos diversos. A restauração ecológica por meio da transposição de serapilheira possibilita o reestabelecimento dos processos ecológicos e pode contribuir com o aumento de microrganismos. Objetivou-se avaliar a influência da serapilheira na comunidade de fungos micorrízicos em uma área de Cabreúva, SP. Dez parcelas foram delimitadas, sendo cinco controle e cinco com tratamento. Foram coletadas amostras de solo em dois períodos para análises físicas, químicas e microbiológicas. Os resultados indicaram que as condições edáficas do local condizem com a presença de FMA, a matéria orgânica transposta não promoveu aumento da riqueza de espécies e não facilitou a colonização de espécies vegetais, enquanto que a umidade gravimétrica e a gramínea podem ter influenciado na riqueza de espécies.

RESUMO Áreas naturais de elevada diversidade biológica estão sendo degradadas para suprir a necessidade do homem em convertê-las em usos diversos. A restauração ecológica por meio da transposição de serapilheira possibilita o reestabelecimento dos processos ecológicos e pode contribuir com o aumento de microrganismos. Objetivou-se avaliar a influência da serapilheira na comunidade de fungos micorrízicos em uma área de Cabreúva, SP. Dez parcelas foram delimitadas, sendo cinco controle e cinco com tratamento. Foram coletadas amostras de solo em dois períodos para análises físicas, químicas e microbiológicas. Os resultados indicaram que as condições edáficas do local condizem com a presença de FMA, a matéria orgânica transposta não promoveu aumento da riqueza de espécies e não facilitou a colonização de espécies vegetais, enquanto que a umidade gravimétrica e a gramínea podem ter influenciado na riqueza de espécies.

ABSTRACT Natural areas of high biological diversity are being degraded to meet man’s need to convert them to various uses. The ecological restoration through litter transposition enables for the reestablishment of ecological processes and may contribute to the increase of microorganisms. It aimed to evaluate the influence of litter on the community of mycorrhizal fungi in an area of Cabreúva, São Paulo State, Brazil. Ten plots were delimited, five control and five treatment. Soil samples were collected during two distinct periods for physical, chemical and microbiological analysis. Results indicated that the edaphic conditions of the place are consistent with the presence of AMF; also, the transposed organic matter did not increase species richness and did not facilitate the colonization of plant species, whereas gravimetric humidity and grass may have influenced species richness.

ABSTRACT: The soil particles can be gathered through physical and/or chemical processes in association with the biological activity, leading to the formation of aggregates. Soil aggregates has several functions in the soil, increasing macroporosity and water circulation - consequently reducing soil erosion and mechanical resistance to root growth, contributing to greater fixation of plants to the soil and absorption of water and nutrients, and protection of intra-aggregate organic matter. The aggregates were initially classified morphologically and in terms of their stability. In recent years, another way of evaluating aggregates, regarding their formation or origin pathway, has gained prominence in the studies conducted in Brazil. As for their origin, the aggregates can be classified morphologically as physicogenic, biogenic, or intermediate. This manuscript presents the techniques used to sample aggregates, the morphological patterns for their distinction observed in different soil classes and management types, and the chemical and physical properties. Additionally, we present analyses that are not commonly used to evaluate aggregates but which have the potential to be used as tools for a better understanding of their origin and to evaluate their modifications when subject to different types of management. In practical terms, identifying the aggregate origin and determining the related attributes allows recognizing the effect of vegetation/soil/management on soil aggregate forming agents, mainly roots and soil fauna, which reflects soil quality. For future studies, and especially to determine the importance of biogenic aggregation in improving edaphic properties, we suggest the use of micromorphology, near-infrared spectroscopy, X-ray computed tomography, clay dispersion analyses in addition with chemical, physical, and biological analysis. This approach can contribute to the identification of other patterns related to pedogenesis and the pathways of aggregate formation.

RESUMO: A biofortificação de culturas alimentares é implementada através da aplicação de fertilizantes minerais, para melhorar os níveis de elementos minerais essenciais para a nutrição humana. O magnésio é um macronutriente essencial na produção e qualidade das culturas, no entanto, em todo o mundo, é o macronutriente mais limitante da agricultura. O magnésio desempenha um papel importante na manipulação de processos fisiológicos e bioquímicos nas plantas. Portanto, o objetivo deste estudo foi avaliar a eficácia da biofortificação com cloreto e sulfato de magnésio no acúmulo de compostos bioativos e capacidade antioxidante em feijões verdes cv. Strike. Duas fontes de magnésio foram aplicadas por via edáfica: cloreto de magnésio e sulfato de magnésio nas doses de 0, 50, 100 e 200 ppm durante o ano de 2018 no México. Foram avaliados o acúmulo de compostos bioativos (fenóis totais, flavonóides totais e antocianinas totais) e a capacidade antioxidante em frutos de feijão-vagem. Os resultados obtidos indicam que a concentração de flavonoides totais, antocianinas totais e capacidade antioxidante nas partes comestíveis do feijão-vagem foram maiores no tratamento com MgSO4 do que nos tratamentos com MgCl2, ultrapassando 30, 59 e 6% respectivamente. Este é um dos primeiros estudos sobre a biofortificação agronômica edáfica do Mg+ e seu efeito na qualidade nutracêutica do feijão-vagem. Um resultado interessante é que o MgSO4 produziu altas concentrações de antocianinas no feijão-vagem comestível. Esses resultados podem ser aplicados como uma nova estratégia para reduzir a desnutrição e melhorar a saúde da população em comunidades urbanas e rurais pobres em países em desenvolvimento.

ABSTRACT: Biofortification of food crops is implemented through the application of mineral fertilizers, to improve the levels of essential mineral elements for human nutrition. Magnesium is a key macronutrient in crop production and quality; however, worldwide, it is the most limiting macronutrient in agriculture. Magnesium plays an important role in manipulating physiological and biochemical processes in plants. Therefore, the objective of this study was to evaluate the efficacy of biofortification with magnesium chloride and sulfate on the accumulation of bioactive compounds and antioxidant capacity in snap bean cv. Strike. Two sources of Magnesium were applied via edaphic route: Magnesium chloride and magnesium sulfate at doses of 0, 50, 100 and 200 ppm during 2018 in Mexico. Accumulation of bioactive compounds (total phenols, total flavonoids and total anthocyanins) and antioxidant capacity in snap bean fruits were evaluated. Results obtained indicate that the concentration of total flavonoids, total anthocyanins and antioxidant capacity in the edible parts of snap beans were higher in the MgSO4 treatment than in the MgCl2 treatments, exceeding 30, 59 and 6% respectively. This is one of the first studies on the edaphic agronomic biofortification of Mg+ and its effect on nutraceutical quality in snap bean. An interesting result is that MgSO4 produced high concentrations of anthocyanins in edible snap beans. These results can be applied as a new strategy to reduce malnutrition and improve the health of the population in poor urban and rural communities in developing countries.

ABSTRACT Land-use change from herbaceous to woody cover -or vice versa- largely affects water fluxes, which in turn can mobilize existing salts dissolved in the soil, and thereby negatively affect soil and/or water quality and site productivity. Secondary salinization was observed after afforestation at the Northern and Eastern subregions of the Río de la Plata Grassland. Based on this, our objective was to determine the degree of association between the climatic (e.g. water balance), edaphic (e.g. texture, presence of petrocalcic horizons) and biological factors (age of plantation, stand density and stand basal area) with the secondary salinization processes under the particular environmental conditions of the Austral Pampas. The lowest electrical conductivity (EC, µS.cm-1) values were found in sites with sandy-textured soils and negative water balance, regardless of tree canopy cover. When EC differences did occur between land uses of the same site (50% of the sites), in most cases - but not in all of them - the highest EC was measured under tree cover. When salinization was significant, no pattern was observed in the salt distribution along the soil profile. An increase of EC was associated with the oldest-unmanaged plantations, with mean age of 40 years, a period much longer than the productive rotation recommended. Under similar edaphic conditions where salinization was observed (i.e. clayed soils, with naturally high salt level), salinization was not significant in relatively young plantations (<rotation period), demonstrating the key role of forest management to decrease its negative impacts on soils.