Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Cocoa (Theobroma cacao L.) is one of the most important agricultural crops in Ecuador; however, the production and quality of the crops is af fected by the disease “cocoa moniliasis”, caused by the fungus Moniliophthora roreri. Currently, this pathogen is considered the main limiting factor for cocoa production in the country. In this study, the ecological niche of the cultivation of T. cacao and M. roreri was evaluated to identify the possible changes in the potential geographic distributions and in the areas of crop-pathogen coexistence in the face of climate change scenarios. For this, records of the presence of M. roreri and T. cacao were collected from national and international databases. Fif teen bioclimatic variables of worldclim 1.4 for the present and future were selected, and the algorithm of maximum entropy MaxEnt to obtain the models. The areas where cocoa and the phytopathogen are potentially distributed are the coastal and Amazon regions of the country at present. The transfer of models in the RCP 4.5 and RCP 8.5 scenarios for the year 2050, predicted the expansion of areas suitable for cocoa, especially in the south of the country, by 16% and 18%, respectively. On the contrary, for the phytopathogen, the model predicts a 5% decrease in suitability in the same future scenarios in the Ecuadorian Amazon region. The areas susceptible to the invasion of the fungus and coexistence with cocoa coincide and are located mainly in the Ecuadorian coast and Amazon for the present and future scenarios, representing a risk for cocoa cultivation. For this reason, it is suggested to adopt early warning measures for the detection and control of the disease, focused on these risk areas for the conservation of biodiversity and food security in the country.

Forage quality is important since it intervenes in aspects related to animal nutrition and productivity and in environmental effects such as methane generation (CH4). Forage quality is determined by a bromatological analysis, which measures variables such as: dry weight (DW), crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF) and ash. Thus, the objective of this study is to evaluate the effects of drinking water and two nutritional solutions with different nitrate/ammonium (NO3-/NH3+) ratios on fresh weight (FW) and bromatological quality of hydroponic green forage (HGF). Oats (Avena sativa) and barley (Hordeum vulgare) were sampled at 5, 10, 15, 20, 25 and 30 days after planting. The variables FW, DW, CP, NDF, ADF, and ash were measured. For the statistical analysis, a 3×2 factorial model (three nutritive solutions and two seed species) was used with repeated measurements over time and Tukey’s comparison of means (P ≤ 0.05). According to the analysis of variance (P ≤ 0.05) (i) time had significant effects on all the variables studied; (ii) nutrient solutions only affected CP; and (iii) the species used had an effect on CP, NDF, ADF and ash. Consistent with the comparison of means, (i) an increase in value of all variables was observed as sampling time progressed; (ii) CP percentage was higher with nutritive solutions than with drinking water, but no difference was observed between solutions; and (iii) hydroponically-grown (HGF) oats had higher CP, NDF, ADF and ash values. To conclude, HGF oats has better nutritional characteristics for livestock than HGF barley.

An increase in photosynthetic capacity, a decrease in transpiration rate, greater growth of plants and increase in yields and quality of crops are effects caused by silicon (Si) and chlorine (Cl). These beneficial effects caused by both elements depend on species and genotypes within a species. Therefore, the objective of the research was to determine the effect of silicon and chlorine, individually or in combination, as well as which are the most effective doses in growth, yield and postharvest quality of cucumber and tomato. The cultivars ‘Paraíso F1’ and ‘tomate F3’ were sown, watered every 24 h and fertilized with 200 kg ha-1 of N and 2 L ha-1 of Micro-Min foliar (20-30-10) on the 36th and 56th day after planting. In both experiments, a randomized complete block design was established, managed in drip irrigation. Treatments consisted of 20, 30 and 50 mg L-1 of Si or Cl and combinations of 20:20 and 30:30 mg L-1 of Si:Cl, plus the control. The highest dose of Si and the three doses of Cl or two of Si:Cl were more effective to induce growth in cucumber, although in regard to yield, the most suitable were the two highest doses of Si and the three of Cl. In tomato, the lowest dose of Cl induced a slight increase in leaf greenness, the two nutrients decreased height, and the highest dose of Si:Cl was more effective to slightly increase the leaf area, however, the yield did not increase. With regards to total soluble solids, the highest dose of Cl and the lowest combination of Si:Cl caused a better response in cucumber; however, in tomato only the lowest dose of Cl caused the highest response.

Aluminum (Al) is the third most abundant element in the Earth’s crust. Its chemical form depends on the soil pH values. In acidic soils, Al is released and solubilized mainly in the ionic form of Al3+, which is toxic to most plants. The main toxic ef fects of Al are observed at the root apex, inhibiting cell division and elongation, which causes a def icient root to uptake water and nutrients, resulting in growth inhibition, thus, a decrease in plant productivity. At present, Al is available in soils that are not naturally acidic and used as farmland, which has generated a research line in relation with the ef fect of Al in dif ferent plant species, for example, accumulation and concentration sites in the dif ferent plant organs. In this context, the objective of this review article is to provide a guide to select the most appropriate technique that allows localizing and quantifying Al in the dif ferent organs of plants growing in acidic soils. For this purpose, the fundamentals of the dif ferent techniques to locate and quantify Al in plant organs and/or tissues are f irst described, and this information is integrated by providing a guide recommending the most appropriate technique based on some characteristics of the species to be analyzed. Furthermore, going deeper into the study of Al accumulation sites and concentrations that the plants can absorb should allow selecting tolerant crops that can be used for agricultural production or phytoremediation studies.

Due to the lack of methods to accurately estimate soil loss in Mexico, experimental studies should be conducted to estimate erosion based on validated data. Therefore, the objective of this research is to estimate the Annual Erosion Rate (A) for various soil covers using the Universal Soil Loss Equation (EUPS) and adjusting its relationship with the Sediment Generation Index (IGS) obtained in experimental batches. The results show that during the period and conditions of this study, EUPS underestimates the value of A, when estimating the erosivity of the rain with the Modif ied Fournier Index (RIMF), in treatments with Natural Vegetation (VN) and Roturation with Esquilmo (RE). Soils without covers evidenced a higher IGS. Likewise, the equations obtained with the relationship IGS vs A, of the treatments with Bare (SD) and Broken Soil (RT) can be used to adjust the edaphic loss rate in soils with the same characteristics as those of the study, complying partially with the objective of this research.

La productividad agrícola de la Amazonía Ecuatoriana es def iciente debido a la mala calidad del suelo, ocasionada por diversos contaminantes. El objetivo del presente estudio fue identif icar el potencial agrícola de suelos de la Amazonía Ecuatoriana, a partir de variables físico-químicas, biológicas y ambientales. Para esto, se tomaron 10 muestras de suelo de los principales agroecosistemas. Las variables físico-químicas se determinaron mediante técnicas estandarizadas. Para el conteo de bacterias (UFC/gr) se usó la metodología de recuento en placa y para la descripción ambiental se usaron variables espaciales (distancia a centros poblados) y espectrales (índice de vegetación de diferencia normalizada NDVI, infrarrojo cercano NIR, índice de vegetación mejorado EVI). A partir del pH, carbono orgánico y saturación relativa (Bases y Al+H) se def inieron índices de fertilidad potencial (IFP). Se presentó un pH ácido en todos los suelos y un porcentaje de materia orgánica menor al 2%, con un nivel promedio de Al y Al+H de 3.7 y 5.7 mEq 100 mL-1. Las relaciones de Ca Mg-1, Mg K-1 y (Ca+Mg) K-1 fueron de 7.7, 10.2 y 83.4. Se observó una relación signif icativa directa entre el pH y el Ca y Mg, con coef icientes de correlación de 0.67 y 0.80. El promedio IFP de los suelos fue 0.46, con rango de 0.33-0.65. La concentración de Cd y Pb fue 0.13 y 59.35 mg kg-1. El conteo de bacterias presentó valores altos en dos muestras (2.64×108 y 2.13×108). El 70% de las áreas se corresponden con el uso de suelo tierra agropecuaria-pastizal. La menor variación se observó en el NDVI, que tuvo un promedio de 0.77. El área central de la zona de muestreo tuvo altos niveles de contaminantes (Al, Cd, Pb), así como la zona de inf luencia alrededor de estos puntos. Es necesario implementar estrategias de remediación, para favorecer las prácticas agrícolas.

Soil organic carbon (SOC) at depth can be destabilized by various climatic or anthropogenic factors, so it is necessary to characterize it properly. The modeling of the vertical distribution of the SOC has generally been approximated using empirical approaches to mathematical model adjustments. This scheme is used to characterize the SOC at depth in different land uses and it is analyzed, but with an incremental approach of introducing constraints in the experimental adjustment, by nonlinear regression. The boundary conditions introduced (for zero and infinity depth) allow parameterizing models with physicochemical and biological sense. The best models selected in the progressive adjustment process were reviewed to analyze the congruence of their parameters, arguing that their bases are not clear to characterize the dynamics of the SOC. As an alternative, a reaction kinetics of variable order n was introduced in the experimental settings, obtaining good results (R2 > 0.99) and clear patterns in the relationships between order n and the kn reaction rate of the alternative model.

Para analizar la dinámica del carbono orgánico de los suelos (COS) asociada a su cambio de uso, de vegetación y prácticas de manejo, es necesario desarrollar modelos para usarse en forma predictiva. Un enfoque de modelación es la distribución del COS presente en los complejos organominerales primarios (arcillas, limos y arenas) ligado a las fracciones físicas. Para la separación de las fracciones físicas se emplea la dispersión del suelo por ultrasonido, paso que requiere optimizar las energías de sonicación para lograr la completa dispersión del suelo. En este trabajo se discute el modelo COLPOS y su hipótesis, así como sus posibles extensiones que consideran las masas y los enriquecimientos de las fracciones físicas del suelo, adicionalmente al análisis de las relaciones entre esas fracciones. Para analizar los patrones asociados al modelo COLPOS y sus extensiones, se analizan resultados disponibles de fraccionamientos de suelos mexicanos realizados con ultrasonido, además de tres bases de datos de fraccionamientos similares publicados en la literatura. Éstos muestran que el modelo COLPOS puede ser parametrizado en función del tamaño y masa de las partículas del suelo; aunque para el caso de las masas algunos resultados son inconsistentes. Del análisis de los cocientes del carbono orgánico entre fracciones para dos cinéticas lineales diferentes (organomineral y organomineral más partícula) las relaciones muestran mayor dispersión que para el caso de solo considerar fracciones de una cinética.

La distribución del carbono orgánico de los suelos (COS) a profundidad es importante para definir almacenes de carbono y analizar los impactos de diferentes mecanismos y procesos de desestabilización. La modelación de la distribución vertical del COS ha sido aproximada por enfoques empíricos o usando modelos de cinéticas de primer orden con multi-compartimentos. En este trabajo se introduce un modelo de cinética de orden n, que generaliza desarrollos previos de uso de un solo compartimento. El modelo es ajustado a perfiles de suelo del Proyecto de Manejo Sustentable de Laderas en la Sierra Norte de Oaxaca, México, en tres microcuencas de las regiones Mazateca, Cuicateca y Mixe. Los protocolos de muestreo, diseño experimental, sistemas y laboratorio son presentados. El modelo de cinética de orden n se ajustó bien a los datos experimentales (R2 > 0.99), aunque se encontró alta variabilidad (horizontal y a profundidad), la cual fue discutida como una posible relación con la posición de los puntos de muestreo en campo.