Resumen. Las raíces finas (≤ 2 mm de diámetro) en los árboles son de vida corta, en condiciones de sequía y baja fertilidad éstas alcanzan mayor longitud por unidad de volumen de suelo; así, la densidad de longitud de raíces es una variable que indica el potencial de absorción de agua y nutrientes que tiene el árbol. El objetivo del presente estudio fue estimar la densidad de longitud de raíces finas (DLRF) su distribución en profundidad y distancia de la base del árbol de teca, por el efecto de la fertilización sintética y abono verde. La metodología utilizada fue la del cilindro, a los 36 meses de edad de los árboles de teca, se tomaron muestras verticales de suelos, cada 10 cm hasta 40 cm de profundidad en las cuatro caras del perfil; y a los 46 meses se muestreó horizontalmente a tres distancias de la base del árbol: 50, 100 y 175 cm, en un diseño de bloques completos al azar. Los resultados muestran que los tratamientos con mayor DLRF fueron: la dosis 60-60-60 kg ha-1 sin abono verde y el testigo con abono verde. La DLRF fue mayor en la profundidad 20-30 cm y 10-20 cm a los 38 y 46 meses. La distancia de 50 cm de la base del árbol mostró mayor DLRF (0.75 km.m−3). La DLRF disminuyó cuando se incrementó la dosis de fertilización sintética o cuando se estableció abono verde (Crotalaria juncea L.).

Abstract. The fine roots (≤ 2 mm in diameter) in the trees are short-lived, in conditions of drought and low fertility they reach a greater length per unit volume of soil; Thus, the root length density is a variable that indicates the water and nutrient absorption potential of the tree. The objective of this study was to estimate the fine root length density (DLRF) its distribution in depth and distance from the base of the three-year-old teak tree, due to the effect of chemical fertilization and a green manure. The methodology used was that of the cylinder, at 36 months of age of the teak trees, vertical soil samples were taken, every 10 cm up to 40 cm deep on the four faces of the profile; and at 46 months it was sampled horizontally at three distances from the base of the tree: 50, 100 and 175 cm, in a randomized complete block design. The results show that the treatments with the highest DLRF were: the 60-60-60 kg ha-1 dose without Green Manure and the control with Green Manure. The DLRF was greater at depth 20-30 cm and 10-20 cm at 38 and 46 months. At a distance of 50 cm from the base of the tree, it showed higher DLRF (0.75 km.m−3). The DLRF decreased when the chemical fertilization dose was increased or when green manure (Crotalaria juncea L.) was established.

Resumen El tomate (Solanum lycopersicum) se consume en el mundo, porque es rico en vitaminas y sales minerales. El QfosfiK® es un bioestimulante que incrementa el rendimiento y mejora la calidad de fruto en diferentes cultivos. El objetivo de la investigación fue evaluar el efecto de la aplicación foliar de fosfito de potasio sobre el crecimiento y rendimiento de los cultivares de tomate Paipai y Cid. El experimento se realizó en condiciones de invernadero en la Facultad de Ciencias Agrícolas, durante 2019 sobre un suelo vertisol, en un diseño de bloques al azar con 10 tratamientos y 4 repeticiones. Los tratamientos aplicados surgieron del arreglo factorial de los dos cultivares de tomate y cinco concentraciones de fosfito de potasio (0, 1,2, 1,5, 1,8 y 2,1 L ha-1) prorrateados en el trasplante, estado vegetativo e inicio de la etapa reproductiva. Se evaluó el número de hojas, el índice de área foliar, la tasa de asimilación neta, el rendimiento de baya y los componentes morfológicos: número de racimos y frutos. El cultivar Cid tuvo el mejor rendimiento debido al mayor número de hojas, índice de área foliar, tasa de asimilación neta y número de racimos planta-1. Respecto a las dosis, cuando se adicionó 1.2 L-1 ha-1 se optimizó la producción. La interacción cultivar × dosis reveló que la mayor cantidad de fruto la logró Cid (3.18 kg planta-1) cuando se añadieron 1.2 L ha-1 de producto, mientras qué, Paipai con 1.5 L ha-1 produjo 2.74 kg planta-1.

Abstract Tomato (Solanum lycopersicum) is consumed worldwide as it is rich in vitamins and mineral salts. QfosfiK® is a biostimulant that increases yield and improves fruit quality in different crops. The objective of the research was to evaluate the effect of foliar application of potassium phosphite on the growth and yield of tomato cultivars Paipai and Cid. The experiment was conducted under greenhouse conditions at the Faculty of Agricultural Sciences, during 2019 on a vertisol soil, in a randomized block design with 10 treatments and 4 replications. The treatments applied arose from the factorial arrangement of the two tomato cultivars and five concentrations of potassium phosphite (0, 1.2, 1.5, 1.5, 1.8 and 2.1 L ha-1) prorated at transplanting, vegetative stage and beginning of the reproductive stage. Leaf number, leaf area index, net assimilation rate, berry yield and morphological components: number of clusters and fruit were evaluated. The cultivar Cid had the best yield due to the highest number of leaves, leaf area index, net assimilation rate and number of bunches plant-1. Regarding the doses, when 1.2 L ha-1 was added, yield was optimized. The cultivar × dose interaction revealed that the highest fruit yield was achieved by Cid (3.18 kg plant-1) when 1.2 L ha-1 of product was added, while Paipai with 1.5 L ha-1 produced 2.74 kg plant-1.

Resumen Introducción. Debido a la alta tasa de degradación del suelo a nivel mundial, se requiere encontrar prácticas agrícolas que promuevan la conservación de suelos. Objetivo. Evaluar el balanceo estático de cargas de un tractor dedicado a la labranza, por medio de diferentes distribuciones de contrapesos en sus ejes, para mejorar las propiedades físicas, mecánicas e hidráulicas y la eficiencia de operación en un suelo vertisol. Materiales y métodos. Se plantearon 3 balanceos de cargas diferentes en los ejes delantero y trasero 40-60%, 30-70% y 50-50%; mediante la adición de contrapesos en el eje trasero del tractor. Se realizaron muestreos de campo a una profundidad de 15 cm en 3 etapas de muestreo (antes de mecanizar, inmediatamente y 2 meses después de mecanizar) en un vertisol con cultivo de pasto (Digitaria decumbens Stent). Se analizaron las variables de contenido de humedad del suelo, densidad aparente, límites plásticos, resistencia a la penetración del suelo, así como las necesidades hídricas del cultivo de acuerdo con los tratamientos. Además, se determinaron variables de operación y eficiencia, tales como profundidad de labranza, patinaje, consumo de combustible y fricción. Se analizaron las diferencias de las variables entre los tratamientos y entre etapas de muestreo con el fin de determinar el tratamiento con la menor afectación a las propiedades del suelo y mayor eficiencia de operación. Resultados. Se encontraron diferencias significativas entre los balanceos de carga por eje evaluados para todas las propiedades del suelo analizadas, excepto en el contenido de humedad. El balanceo 30-70% presentó los valores más bajos de consumo de combustible y de agua para el riego, patinaje, resistencia al corte y resistencia a la penetración. Conclusiones. El balanceo 30-70% se considera ideal para mecanizar bajo las condiciones estudiadas. No se recomienda mecanizar con el balanceo 50-50%, ya que la profundidad de labranza y los cambios en las propiedades del suelo fueron en detrimento de algunas propiedades del mismo.

Abstract Introduction. Due to the high worldwide rate of soil degradation, it is necessary to look for agricultural practices that promote soil conservation. Objective. To assess the tractor axle load balancing dedicated to tillage, through different counterweights distributions, to improve the physical, mechanical, and hydraulic properties of a vertisol and the efficiency of tillage operation. Materials and methods. Three different load balances were set on the front and rear axles, being 40-60%, 30-70% and 50-50%, by adding counterweights to the rear axle of the tractor. Field samples were taken at a depth of 15 cm in 3 sampling stages (before, immediately and 2 months after tillage), in a grass (Digitaria decumbens Stent) cultivated lot. Soil water content, bulk density, plastic limits, soil penetration resistance, as well as the water needs of the crop according to the treatments were analyzed. In addition, operation and efficiency variables were determined, such as tillage depth, slippage, fuel consumption, friction, and tractor power required. The differences of the variables between the treatments and sampling stages were analyzed to determine the treatment with the least impact to the soil properties and greater efficiency of operation. Results. Significant differences were found between balances in all the soil properties analyzed, except in the soil water content. The balance 30-70% presented the lowest values of fuel and water consumption for irrigation of the grass crop, wheel slippage, shear stress and penetration resistance. Conclusions. The balance treatment of 30-70% was considered as the best treatment under the studied conditions. Tillage with the treatment 50-50% was not recommended since tillage depth and soil property changes between sampling stages affected negatively to some soil properties.

Resumen El estado de Tabasco es principal productor de palma de aceite. El objetivo del presente trabajo fue generar una dosis de fertilización por subunidad de suelo y un rendimiento potencial para la palma de aceite. Se utilizó la metodología del Sistema Integrado para Recomendar Dosis de Fertilizantes (SIRDF). Se obtuvieron ocho polígonos de Thiessen, los cuales se agruparon en polígonos de baja (1 281 a 1 623 mm), mediana (1 830 a 1 977 mm) y alta precipitación (> 2 044 mm). Además de 13 subunidades de suelos, de las cuales 11 están cultivadas con palma de aceite: Leptosol Réndzico (Húmico), Luvisol Gléyico (Arcíllico, Éutrico, Diferéntico), Acrisol Gléyico Crómico (Éutrico, Francoso, Cutánico, Diferéntico), Calcisol Pétrico Cámbico (Francoso, Rúptico), Cambisol Gléyico Éutrico (Francoso), Phaeozem Réndzico Léptico Cámbico (Arcíllico), Vertisol Pélico (Gléyico, Mesotrófico, Estágnico), Fluvisol Gléyico Calcárico (Arcíllico), Gleysol Oxigléyico Dístrico (Arcíillico, Vértico), Lixisol Abrúptico (Arcíllico, Cutánico), y Arenosol Dístrico (Alúmico). El análisis de suelos indica de mediana a baja fertilidad con deficiencia de N, P, K, Ca, Fe, Zn, Cu, y B. Se generó la dosis de fertilizante para cada subunidad de suelo y para tres escenarios de rendimiento de fruta fresca. Se generó la recomendación de macro y micro nutrimentos para lograr una fertilización balanceada de la palma de aceite y su forma de aplicación.

Abstract The cultivation of oil palm in the state of Tabasco is the main producer. The objective of this work was to generate a fertilization dose per soil subunit and a potential yield for oil palm. The methodology of the Integrated System to Recommend Fertilizer Doses (SIRDF) was used. Eight Thiessen polygons were obtained, which were grouped into low (1 281 to 1 623 mm), medium (1 830 to 1 977 mm) and high precipitation (>2 044 mm) polygons. In addition to 13 soil subunits, of which only 11 are cultivated with oil palm: Leptosol Réndzico (Humic), Luvisol Gléyico (Arcíllico, Eutrico, Diferéntico), Acrisol Gléyico Crómico (Eutrico, Loamy, Cutánico, Diferéntico), Calcisol Pétrico Cambic (Franky, Ruptic), Gleyic Eutric (Franky) Cambisol, Phaeozem Réndzic Leptic Cambic (Arcyllic), Pelic Vertisol (Gleyic, Mesotrophic, Stagnin), Gleyic Calcaric (Arcyllic) Fluvisol, Oxygleyic Dystric (Arcyllic, Vertic) Gleysol, Abruptic Lixisol (Claylic, Cutanic), and Dystric Arenosol (Aluminic). Soil analysis indicates medium to low fertility with deficiencies of N, P, K, Ca, Fe, Zn, Cu, and B. The fertilizer dose was generated for each soil subunit and for three fresh fruit yield scenarios. Recommendations for macro and micronutrients were generated to achieve a balanced fertilization of the oil palm and its form of application.

RESUMEN La compactación del suelo por efecto de la cosecha mecanizada constituye un problema fundamental en el cultivo de la caña de azúcar, que provoca el deterioro vegetativo de las plantas y la disminución del rendimiento agrícola. El trabajo se realizó con el objetivo de evaluar el efecto de la cosecha mecanizada sobre la variabilidad espacial de la resistencia a la penetración, en un perfil del entresurco del cultivo de la caña de azúcar plantada en un Vertisol Pélico en áreas de la Unidad Empresarial de Base Cristino Naranjo. La cosecha mecanizada se hizo mediante una cosechadora cañera CASE IH A8800 y un tractor YTO 1604 con semirremolque autobasculante. Se escogieron al azar tres sitios de muestreo, en los que se determinó la resistencia a la penetración a 0, 10, 20, 30, 40, 50, 60, 70 y 80 cm de distancia del centro del surco. Los muestreos se realizaron antes y después de la cosecha mecanizada y se expresaron en intervalos constantes (5 cm), hasta los 40 cm de profundidad. Los valores observados en los tres sitios de muestreo fueron promediados, y se obtuvieron dos perfiles de compactación. Se realizó el análisis geoestadístico y se verificó la dependencia espacial. Antes de la cosecha mecanizada, la mayor resistencia a la penetración se encontró a los 30 cm del surco y a una profundidad de 15 cm, prolongándose diagonalmente hasta 65 cm del surco, a 35 cm de profundidad. Los primeros 5 cm de profundidad mostraron pocos cambios luego de la cosecha, cuando apareció una capa subsuperficial con una resistencia a la penetración por encima de 6 MPa desde el surco hasta el camellón, donde se encontró una resistencia a la penetración superior a los 8 MPa.

ABSTRACT Soil compaction as a result of mechanized harvesting constitutes a fundamental problem in the culti^vation of sugarcane, which causes the vegetative deterioration of plants and a decrease in agricultural yield. The work was carried out with the objective of evaluating the effect of mechanized harvesting on the spatial variability of soil penetration resistance in a profile of the cultivation of sugarcane inter-furrow space planted in a Pellic Vertisol in areas of the Base Business Unit "Cristino Naranjo". Mechanized harvesting was carried out using a CASE IH A8800 sugarcane harvester and YTO 1604 tractor with a self-tipping semi-trailer. Three sampling sites were randomly chosen, in which the soil penetration resistance was determined at 0, 10, 20, 30, 40, 50, 60, 70 and 80 cm from the center of the furrow. The samplings were carried out before and after the mechanized harvest and were expressed in constant intervals (5 cm), up to 40 cm deep. The values obtained in the three sampling sites were averaged, obtaining two compactionprofiles. Geostatistical analysis wasperformed and spatial depgndence was verified. Before mechanized harvesting, the greatest soil penetration resistance was found at 30 cm from the furrow and at a depth of 15 cm, extending diagonally up to 65 cm from the furrow, at a depth of 35 cm. The first 5 cm of depth showed little change after harvest, when a subsurface layer appeared with a soil penetration resistance above 6 MPa from the furrow to the ridge, where a soil penetration resistance greater than 8 MPa was found.

ABSTRACT Water quality and soil quality are of great importance for crop yield in the context of small-scale irrigated agriculture in the Northeast region of Brazil. In this respect, this study aimed to determine changes in soil fertility and resistance to root penetration caused by fertigated cropping, as compared to soil under native forest. In each area, a non-regular sampling grid was established, which consisted of 87 georeferenced points in the melon cultivated area and 8 points in the native forest area. At these points, samples were obtained at depths of 0-10, 10-20, 20-30 and 30-40 cm. The determinations performed included soil physical, chemical and mechanical attributes. Multivariate analysis techniques and geostatistical procedures were used to analyze and interpret the data. The cultivation of the Vertisol altered all the variables studied, compared to the area under native forest. Soil decompaction and increase in phosphorus content were positive effects, while organic matter decomposition and reductions in potassium, calcium, magnesium and cation exchange capacity were negative effects. Sodium content and porosity parameters were prominent factors in soil alterations.

RESUMO A qualidade da água e do solo têm grande importância para a produtividade das culturas no contexto da pequena agricultura irrigada na região Nordeste do Brasil. Neste sentido, este estudo visou determinar as alterações na fertilidade e na resistência do solo causadas pelo cultivo fertirrigado, em relação ao solo sob mata nativa. Em cada área foi estabelecida uma grade de amostragem não regular, as quais constaram de 87 pontos georreferenciados, na área cultivada com melão, e 8 pontos na área de mata nativa. Nestes pontos foram obtidas amostras nas profundidades de 0-10, 10-20, 20- 30 e 30-40 cm. As determinações realizadas incluíram atributos físicos, químicos e mecânicos do solo. Técnicas de análise multivariada e procedimentos de geoestatística foram empregadas para analisar e interpretar os dados. O cultivo do Vertissolo alterou todas as variáveis estudadas, em relação à área sob mata nativa. As alterações positivas foram a descompactação do solo e o aumento no teor de fósforo e as negativas foram a decomposição da matéria orgânica e a redução nos teores de potássio, cálcio, magnésio e na capacidade de troca de cátions. O teor de sódio e os parâmetros de porosidade foram fatores de destaque nas alterações do solo.

Resumen: Las características físicas y químicas del suelo desempeñan un papel fundamental en el crecimiento y el rendimiento de la vid. Los suelos del sur de Uruguay presentan un alto contenido de montmorillonita o illita. Las proporciones de estos minerales merecen especial atención ya que influyen en la estructura del suelo y en sus propiedades hídricas. El presente estudio se realizó en un viñedo de 1,1 ha de esta región (Canelones), caracterizado por una alta heterogeneidad de vigor de las plantas. El objetivo fue determinar y cartografiar las propiedades físicas y químicas del suelo, y su relación con el vigor de las plantas y el rendimiento. La capacidad de intercambio catiónico (CEC) y los contenidos de arcilla y materia orgánica se midieron en 84 lugares de este viñedo para calcular los contenidos de montmorillonita e illita del suelo. Además, se corroboró el tipo y la abundancia de arcillas mediante análisis de difractometría de rayos X. Los contenidos de CEC y de montmorillonita se correlacionaron positivamente con el vigor de la vid, expresado por el índice de vegetación normalizado (NDVI), el diámetro del tronco, el peso de la poda, el área foliar y con el rendimiento. Así, la distribución dentro del viñedo de la relación montmorillonita/ilita condicionó la heterogeneidad del crecimiento de la vid y del rendimiento a nivel de campo. Se discute el impacto de estos minerales en el suministro de agua y minerales a la planta.

Abstract: Soil physical and chemical characteristics play a key role on vine growth and yield. The soils of South Uruguay display high content of montmorillonite or illite. The proportion of these minerals deserves special attention as they influence the soil structure and its hydrological properties. The present study was conducted in a 1.1 ha vineyard of this region (Canelones), characterized by a high heterogeneity of plant vigour. It was aimed to determine and map the physical and chemical properties of the soil and their relations with plant vigour and yield. The cation exchange capacity (CEC) and the clay and organic matter contents were measured in 84 locations within this vineyard to calculate the montmorillonite and illite contents of the soil. In addition, the type and abundance of clays was corroborated by X-ray diffractometry analysis. The CEC and montmorillonite contents were positively correlated with vine vigour, expressed by the Normalized Vegetation Index (NDVI), trunk diameter, pruning weight, leaf area, and with yield. Thus, the within vineyard distribution of the ratio montmorillonite/illite conditioned the heterogeneity of vine growth and yield at the field level. The impact of those minerals on water and mineral supply to the plant is discussed.

Resumo: As características físicas e químicas do solo desempenham um papel fundamental no crescimento e rendimento da vinha. Os solos do Sul do Uruguai apresentam um elevado teor de montmorilonite ou illite. As proporções destes minerais merecem especial atenção, uma vez que influenciam a estrutura do solo e as propriedades hídricas. O presente estudo foi realizado numa vinha de 1,1 ha desta região caracterizada por uma elevada heterogeneidade de vigor vegetal. O seu objetivo era determinar e mapear as propriedades físicas e químicas do solo e as suas relações com o vigor e rendimento das plantas. A capacidade de troca catiônica (CEC) e os teores de argila e matéria orgânica foram medidos em 84 locais dentro desta vinha para calcular os teores de montmorilonite e illite do solo. Além disso, o tipo e abundância de argilas foram corroborados pela análise difractométrica de raios X. Os teores de CEC e montmorillonite foram positivamente correlacionados com a vigor da vinha, expresso pelo Índice de Vegetação Normalizada (NDVI), diâmetro do tronco, peso da poda, área foliar, e com o rendimento. Assim, a distribuição dentro da vinha da razão montmorilonite/ilite condicionou a heterogeneidade do crescimento da vinha e o rendimento ao nível do campo. O impacto desses mineraisminerais na água e no fornecimento de minerais à planta é discutido.

ABSTRACT Castor bean (Ricinus communis L.) is an oleaginous plant of economic importance due to its different industrial applications. Edaphic characteristics are used to determine the viability of places considered as suitable to obtain castor oil. The objectives of this study were to determine the edaphic characteristics and oil content of R. communis, and to evaluate elicitation with salicylic acid (SA) in El Marqués, Querétaro, Mexico. Sampling was carried out in a direct way, selecting sites where castor bean plants were found. Samples of 1.5 kg of soil were taken and 3 clusters of castor bean in a mature state were collected from 21 accessions. The physicochemical characteristics of the soil and oil content of seeds were determined. Finally, 300 plants of the Guanajuatoil variety were planted and elicitated with different SA concentrations under greenhouse conditions in order to determine oil content. The physical analysis of the soil samples indicated dark-colored soils, Mollisol and Vertisol types, with different textures: clay, clay loam, sandy clay loam and sandy loam. Soil chemical analyses showed the following soil characteristics: pH 7.22; electrical conductivity 0.52 dS m-1; organic matter 7.17%; cation exchange capacity 26.77; calcium 38.62, magnesium 6.81, sodium 13.41and potassium 6.97 cmol kg-1; and nitrogen and phosphorus contents of 16.32 and 54 mg kg-1, respectively. Castor oil content was higher in clay soils (41.46%). The plants elicited with SA presented oil contents ranging from 28.99% to 52.9%, obtained with 100 and 900 ^M. In conclusion, elicitation with SA is an adequate method to increase oil content in castor bean seeds. The locality of El Marqués has good potential for the production of castor oil.

ABSTRACT An important aspect in the study and understanding of the physical phenomena involved in water movement in the soil-plant system is the need to carry out the hydrodynamic characterization (HC) of non-saturated field soils. Studies of this type have been widely developed in soils of temperate climates, but they are infrequent in the tropics, hence there is a need for further research in tropical Vertisols under field conditions. Hydrodynamic characterization consists of finding the functional relationship between soil hydraulic conductivity (K), matric head (h) and soil moisture content (θ), widely known as K(θ) and h(θ) relationships, being the main objective of this study. The instantaneous profile method (IPM) was applied, in which splines were used for the HC of a bare, tropical agricultural field soil classified as a Vertisol. Field measurements of h and θ were made at five different soil depths (0.15, 0.30, 0.45, 0.60 and 0.90 m) and values of K at the same depths were estimated with the IPM, which allowed for the estimation of pairs of values of the K(θ) relationships in the soil profile. Unlike in other studies with the same objective, the use of splines was proposed to represent the spatial variation of the H(z) and θ(z) functions in the IPM. Subsequently, the van Genuchten equation was adjusted to the specific values determined for the h(θ) relations (r2 value ranged from 0.65 to 0.87), and the Ks values and the point data of K and θ were used to estimate the accuracy of the equation proposed by Mualem–van Genuchten (M-vG): in this case negative values for the exponent l of the M-vG function were determined for the five soil depths under study, ranging from –7.04 (0.45 m deep), to -13.26 (0.90 m deep). In addition, pedotransfer functions for tropical soils proposed in the literature, based on different soil physical properties, were used to estimate the h(θ) and K(θ) relationships and the saturated hydraulic conductivity (Ks). Best square root of the mean squared error (SRMSEθ) observed was 0.02853 cm3 cm-3 at 0.15 m depth and 0.02262 cm3 cm-3 at 0.9 m depth for h(θ) relations, and in all cases, the SRMSEk values are less than 0.0018 m day-1 for K(θ) relationships. The results reveal the utility of splines in the IPM for characterizing the soil profile K(θ) relationships in field studies, as well as the need for more research to the generation of pedotransfer functions in tropical Vertisols.

ABSTRACT The salinity of the soil constitutes today one of the main degradation processes that affects the lands under irrigation; and especially the production of rice. The objective of the research was to estimate the electrical conductivity of the soil by means of spectral information in the cultivation of rice in the Mayarí municipality, Holguín. The research was developed on a Chromic Vertisol, which are the most prone in the territory to trigger degradation processes such as salinity, given by management practices in rice cultivation. Two semi-empirical models proposed from different spectral indices were used, the NDSI and the IS, which were calculated in the QGis 3.10 software with multispectral images from the Landsat 8 OLI / TIRS sensor. The NDSI and the SI-ASTER showed the lowest determination and negative correlation in both models. The SI and the SI-ASTER produce an overestimation of the electrical conductivity values of the soil (EC ≥ 100%), the NDSI, SSSI.1 and SSSI.2 indicate a moderate content of salts in the soil (EC 20% ˂ EC ≤ 40%). Although the use of spectral salinity indices yielded a high determination, the SI and the SI-ASTER indicated an overestimation of the electrical conductivity existing in the soil, which could be due to the presence of a saturation of the signal captured by the sensor and reflected in the indices obtained, which exceeded the values in which the saline index oscillates.

RESUMEN La salinidad del suelo constituye hoy en día uno de los principales procesos de degradación que afecta las tierras bajo riego; y en especial la producción de arroz. La investigación tuvo como objetivo estimar la conductividad eléctrica del suelo mediante información espectral en el cultivo del arroz en el municipio Mayarí, Holguín. La investigación se desarrolló sobre un Vertisol Crómico, los cuales son los más proclives en el territorio a desencadenar procesos de degradación como la salinidad, dado por las prácticas de manejo en el cultivo del arroz. Se utilizaron dos modelos semiempíricos propuestos a partir de índices espectrales diferentes, el NDSI y el IS los cuales se calcularon en el software QGis 3.10 con imágenes multiespectrales del sensor Landsat 8 OLI/TIRS. El NDSI y el SI-ASTER arrojaron la menor determinación y correlación negativa en ambos modelos. El SI y el SI-ASTER producen una sobreestimación de los valores de conductividad eléctrica del suelo (EC ≥ 100%), el NDSI, SSSI.1 y el SSSI.2 indican un contenido moderado de sales en el suelo (EC 20% ˂ EC ≤ 40%). Aunque la utilización de los índices espectrales de salinidad arrojó una alta determinación, el SI y el SI-ASTER indicaron un sobreestimación de la conductividad eléctrica existente en el suelo lo cual podría deberse a la presencia de una saturación de la señal captada por el sensor y reflejada en los índices obtenidos, la cual sobrepasó los valores en los cuales oscila el índice salino.

RESUMO O objetivo deste trabalho foi verificar o efeito de diferentes sistemas de manejo sobre a qualidade físico-hídrica de um Vertissolo localizado no domínio climático do Semiárido brasileiro. Os tratamentos foram compostos pelos seguintes sistemas de manejo: (S1) Pastagem (Cynodon spp.) com 4 anos; (S2) Romã (Punicata granatum L.) com 6 anos;(S3) Sorgo forrageiro (Sorghum bicolor L.) com 4 anos e, (S4) vegetação nativa. Avaliou-se a retenção de água no solo por meio da curva característica de umidade, densidade do solo, porosidade do solo (macro e microporosidade e porosidade total), capacidade de aeração do solo e porosidade livre de ar. Os dados foram analisados através da estatística multivariada. Os resultados demonstram que o Vertissolo apresenta elevada retenção e baixa disponibilidade de água as plantas. Melhor qualidade estrutural foi observada no solo sob mata nativa. Conclui-se que os sistemas de manejo composto por pastagem e sorgo estão promovendo mudanças, até o presente momento de forma negativa à estrutura do solo, com redução da macroporosidade e da capacidade de aeração do solo.

ABSTRACT The objective of this work was to verify the effect of different management systems on the physical-hydric quality of a Vertisol located in the climatic domain of the Brazilian Semiarid. The treatments were composed by the following management systems: (S1) Pasture (Cynodon spp.) With 4 years; (S2) Pomegranate (Punicata granatum L.) aged 6; (S3) Forage sorghum (Sorghum bicolor L.) aged 4 years and (S4) native vegetation. The soil water retention curve, soil density, porosity of soil (macro, microporosity and, total porosity), soil aeration capacity and free air porosity. The data were analyzed using multivariate statistics. The results demonstrate that the Vertisol presents high retention and low availability of water to the plants. Better structural quality was observed in the soil under native forest. It is concluded that the management systems composed of pasture and sorghum are promoting negative changes to the soil structure, with a reduction of macroporosity and of the aeration capacity of the soil.

ABSTRACT Soil compaction causes negative effects on crop yield and its mechanical response analysis has recently gained relevance for research through numerical methods. In this work, Finite Element Method (FEM) using the Mohr-Coulomb (MC) and Hardening Soil (HS) constitutive models were employed to simulate the mechanical response of a Vertisol agricultural soil. First, an experimental study of the unconsolidated-undrained (UU) triaxial compression test with different moisture contents (w = 10%, 20% and 34%) and confining pressures (σ3 = σc = 0.05 MPa, 0.10 MPa and 0.15 MPa) was carried out, to obtain the shear strength parameters cohesion (c) and friction angle (φ), as well as the Young’s modulus (E) of the soil. The experimental study was conducted through a 32 factorial design with three replicates that it was used to evaluate the influence of the w and σc on E of the studied soil. Also, an analysis of the behavior of the φ and c parameters at each w was performed. Numerical simulations were done with similar conditions as the experimental tests with respect to loading and boundary conditions. A comparison of the mechanical response between numerical results and physical experiments was carried out. As a result, the MC model allowed to estimate satisfactorily the stress-strain relationship of the soil for w of 10% and 20%, while HS model exhibited a better approximation for w of 34% in comparison with the MC model. Finally, the methodology and the adjusted parameters of the agricultural soil obtained in this work, can be used in the study of soil compaction produced by the agricultural machinery.

RESUMEN Los Vertisoles presentan factores edáficos limitantes fundamentalmente de carácter físico. El estudio de su hidropedología, apoyado en técnicas multivariadas, es de vital importancia. El trabajo se desarrolló con el objetivo de determinar, mediante análisis multivariado, el comportamiento hidropedológico de un Vertisol Crómico bajo diferentes usos de la tierra. En áreas bajo pasto natural, caña de azúcar y bosque secundario, pertenecientes a la Estación Provincial de Investigaciones de la Caña de Azúcar de Holguín, se escogieron tres puntos al azar en cada una. Se determinó la resistencia a la penetración, la densidad aparente, la humedad gravimétrica y la humedad volumétrica a las profundidades de 0-10, 10-20 y 20-30 cm. Se realizó un Análisis de Componentes Principales y de Correlaciones Canónicas, con los softwares Statistica 7 y Statgraphics Plus XV.II. Se encontró que las dos primeras componentes realizaron la mayor contribución a la varianza, con un 83.09%. Los mayores aportes (1ra componente) estuvieron dados por la humedad en todas las profundidades y por la compactación del suelo en la profundidad de 20-30 cm. La 2da componente estuvo influenciada por la compactación del suelo en las capas de 0-10 y de 10-20 cm. Existió contraposición entre las variables que caracterizan la fase sólida con las que describen la fase líquida del suelo. Existió correlación entre la humedad del suelo y la compactación. Los dos primeros pares de variables canónicas mostraron una fuerte correlación lineal y dispersada regularmente a lo largo de los valores centrales del modelo, con un notable agrupamiento por profundidades.

ABSTRACT Vertisols present edaphic limiting factors primarily of a physical nature. The study of their hydropedology, supported by multivariate techniques, is of vital importance. The work was developed with the objective of determining, through multivariate analysis, the hydropedological behavior of a Chromic Vertisol under different plant covers. In areas under natural grass, sugarcane, and secondary forest, belonging to the Holguín Sugarcane Provincial Research Station, three random points were chosen in each. Soil penetration resistance, soil bulk density, gravimetric moisture, and volumetric moisture at depths of 0-10, 10-20 and 20-30cm were determined. A Principal Component Analysis and Canonical Correlations were performed using Statistica 7 and Statgraphics Plus XV.II. The first two components made the greatest contribution to the variance, with 83.09%. The greatest contributions (1st component) were given by moisture at all depths and by soil compaction at a depth of 20-30cm. The 2nd component was influenced by soil compaction in the 0-10 and 10-20cm layers. There was a contrast between the variables that characterize the solid phase with which they describe the liquid phase of the soil. There was a correlation between soil moisture and compaction. The first two pairs of canonical variables showed a strong linear correlation and regularly dispersed along the central values of the model, with a remarkable grouping by depths.

Resumen Se evaluaron tres híbridos de maíz bajo tres niveles de fertilización nitrogenada (50, 100 y 150 kg de N/ha) durante la estación lluviosa 2019 en la Granja Experimental Agrícola de la ESPOL (Escuela Superior Politécnica del Litoral), Guayaquil, Guayas, Ecuador. El suelo donde se implementó el experimento se clasifica como Vertisol y es conocido como de alta fertilidad, teniendo en cuenta su alto contenido de mineral arcilloso tipo 2:1 tales como la montmorillonita y/o ilita. Con una CIC y saturación de bases en la superficie son de 43,9meq/100g y 99,4%, respectivamente. Los híbridos que se experimentaron son: Pioneer 4039 (P4039), Advanta 9313 (AV9313) y Advanta 9139 (AV9139), distribuidos por la compañía FARMAGRO. En el área experimental, se aplicaron tres niveles de fertilización nitrogenada (50, 100 y 150kgN/ha), 50 kg de P2O5 y 50 kg de K2O/ha, respectivamente. Como característica agronómica, se observó diferencia significativa al 1% no sólo para el híbrido sino también para el nitrógeno, así como en la longitud de hoja, obteniendo el más alto valor para el AV 9139. Al igual que el caso anterior, el rendimiento del grano con 14% de humedad, se observó una diferencia significativa al 5% para la interacción. Aunque el más alto rendimiento fue para el AV9139, se observó una tendencia negativa de acuerdo a la mayor dosis de nitrógeno. Recomendándose el híbrido AV 9139 con la aplicación de 50kgN/ha de acuerdo con los resultados obtenidos en el análisis económico.

Resumo Avaliaram-se três híbridos de milho sob três níveis de fertilização com nitrogênio (50, 100 e 150 kg de N/ha) durante a estação chuvosa 2019 na Fazenda Experimental Agrícola da ESPOL (Escola Superior Politécnica do Litoral), Guayaquil, Guayas, Equador. O solo onde implantou-se o experimento é classificado como Vertissolo e é conhecido como de alta fertilidade, levando em conta seu alto teor de mineral argiloso tipo 2: 1 tais como a montmorilonita e/ou ilita. Com uma CTC e saturação por bases na superfície são de 43,9 meq/100g e 99,4%, respectivamente. Os híbridos que foram experimentados são: Pioneer 4039 (P4039), Advanta 9313 (AV9313) e Advanta 9139 (AV9139), distribuídos pela empresa FARMAGRO. Na área experimental, aplicaram-se três níveis de adubação nitrogenada (50, 100 e 150kgN/ha), 50kg de P2O5 e 50kg de K2O/ha, respectivamente. Como característica agronômica, observou-se foi diferença significativa ao 1% não só para o híbrido, mas também para o nitrogênio, assim como na longitude de folha, obtendo-se o maior valor para AV 9139. Ao igual que o caso anterior, o rendimento do grão com 14% de umidade, observou-se diferença significativa ao 5% para a interação. Embora o mais alto rendimento foi para AV9139, observou-se uma tendência negativa de acordo com a maior dose de nitrogênio. Recomendando-se o híbrido AV 9139 com a adubação de 50kgN/ha de acordo com os resultados obtidos na análise econômica.

Abstract It was evaluated three hybrids of corn under the three levels of the nitrogen application (50, 100 and 500kgN/ha) during the rainy season at the Experimental Field in the ESPOL (Escuela Superior Politécnica del Litoral), Guayaquil, Guayas, Ecuador. The soil where the experiment was implemented is classified as Vertisol and it is known as high fertility, taking into account its high content of type 2: 1 clay mineral such as montmorillonite and / or illite. It was 43,9 meq/100g for CEC and 99,4% for the base saturation, respectively. These hybrids which were experimented are: Pioneer 4039 (P4039), Advanta 9313 (AV9313) and Advanta 9139 (AV9139), distributed by the company FARMAGRO. On the experimental area, it was applied 50kgP2O5 and 50kgK2O/ha, respectively. As agronomic character, it was observed the significant difference al 1% not only for the hybrid but also for nitrogen, as well as for length of leave, obtaining the largest for the AV 9139. Like the previous case of the grain yield with 14% moisture, it was observed the significant difference at 5% for the interaction. Although it was the highest performance for the AV9139, it was observed the negative trend in accordance with the higher nitrogen amounts. Recommending the hybrid AV 9139 with the application of 50kgN/ha according to the results obtained with the highest net benefit.

Summary: This study performed two assays to analyze the effect of inoculating mycorrhizal fungi on wheat production during winter both by rotating crop and increasing fertilizer doses to implement agricultural conservation practices. The following treatments were established for the first assay: (1) wheat inoculation with mycorrhizal fungus Glomus mosseae without fertilizer; (2) application of 200 units of N ha-1 without inoculation; (3) inoculation + 100 units of N ha-1; (4) application of 100 units of N ha-1 without inoculation; (5) inoculation + 150 units of N ha-1; (6) application of 150 units of N without inoculation. The second assay assessed the response of wheat production to the two preceding crop rotations: maize‑wheat (G-G) and bean-wheat (L-G) and four increasing nitrogen fertilization doses: 0, 100, 150, and 200 units ha-1. With the inoculation of G. mosseae + 75% of nitrogen fertilization, wheat production had the greatest grain yield (5.6 Mg ha-1) and was 36% greater than the control group with the application of only 100% fertilizer without inoculant. Wheat inoculation without nitrogen fertilizer had the lowest production (2.6 Mg ha-1). On the other hand, wheat production with L-G rotation had a better response (R2 = 0.72) at increasing N doses where the greatest grain yield was obtained with 4.7 Mg ha-1 and only 150 units of N ha-1, which corresponded to 1 Mg ha-1 more compared with the maximum wheat production obtained in the G-G rotation with 2000 units of N ha-1. The use of inoculated biofertilizers, such as mycorrhizal fungi or by the effect of crop rotation with legumes, such as bean, requires supplementary N dosage to boost wheat production; however, it is feasible to decrease nitrogen fertilizer dosage to 25%.

Resumen: Se realizaron dos ensayos para estudiar el efecto de la inoculación de hongos micorrízicos en la producción de trigo de invierno y la rotación de cultivos y dosis crecientes de fertilización, ambos aunados a la implementación de prácticas de agricultura de conservación. En el primero se establecieron los siguientes tratamientos: (1) Inoculación del trigo con los hongos micorrízicos: Glomus mosseae, sin fertilización; (2) aplicación de 200 unidades de N ha‑1, sin inoculación; (3) inoculación + 100 unidades de N ha-1; (4) aplicación de 100 unidades de N ha-1, sin inoculación; (5) inoculación + 150 unidades de N ha-1; (6) aplicación de 150 unidades de N, sin inoculación. En el segundo se evaluó la respuesta, en la producción de trigo, a dos rotaciones precedentes de cultivo: maíz-trigo (G-G) y frijol-trigo (L-G), y cuatro dosis crecientes de fertilización nitrogenada: 0, 100, 150 y 200 unidades ha-1. La producción de trigo, con la inoculación de G. mosseae + 75% de fertilización nitrogenada recomendada, tuvo el mayor rendimiento de grano (5.6 Mg ha-1), y fue 36 % mayor, respecto al testigo con aplicación de sólo 100% de la fertilización, sin inoculante. La inoculación de trigo, sin aplicación de fertilizante nitrogenado tuvo la producción más baja (2.6 Mg ha-1). Por otra parte, la producción de trigo con la rotación L-G tuvo una menor respuesta (R2 = 0.72) a las dosis crecientes de N, y fue donde se obtuvo el mayor rendimiento de grano, con 4.7 Mg ha-1, con sólo 150 unidades de N ha-1, que correspondió a 1 Mg ha-1 más, comparado con la máxima producción de trigo que se obtuvo en la rotación G-G, con 200 unidades de N ha-1. El uso de biofertilizantes inoculados, como los hongos micorrízicos, o por efecto de la rotación de cultivos con leguminosas, como frijol, requiere de dosis completarías de N para potenciar la producción de trigo; sin embargo, es factible disminuir en 25% la dosis de fertilización nitrogenada.