Ciencia y Tecnología Agropecuaria

Introductory learning on soil science through a MOOC course

Abstract The purpose of this research was to describe the resources used in the design of an introductory massive open online course (MOOC) on soil science, to evaluate the effect of resources on student performance and evaluate the development of the course. The course was structured for six weeks, including different educational resources, with qualified activities like tasks and tests, and optional as forums and suggested activities. The data collected from 1,020 students of different careers or disciplines, of which the respective descriptive performance analysis was performed, was expressed as percentage. In addition, a qualitative and quantitative optional evaluation was carried out to evaluate the course that was aimed for students. The results indicate that the strategies used influence the positive performance of students and the evaluation indicates that the student-teacher interaction is key for the success of the course. This exploratory study explains the process for the design and implementation of an online course on soil sciences in an efficient way.

Resumen El propósito de esta investigación fue describir los recursos utilizados en el diseño de un curso masivo de acceso abierto en línea introductorio de ciencias del suelo, y evaluar tanto el efecto de los recursos obligatorios en el rendimiento de los estudiantes, como el desarrollo del curso. Este último fue estructurado para una duración de seis semanas, y en él se incluyeron diferentes recursos educativos, con actividades calificadas, como retos y test, y opcionales, como foros y actividades recomendadas. Se recolectaron datos de 1.020 estudiantes de diferentes carreras o disciplinas, de los cuales se realizó un análisis descriptivo del rendimiento, y los datos se expresaron en porcentaje. Además, se hizo una evaluación opcional dirigida a los estudiantes, cualitativa y cuantitativa, para evaluar el curso. Los resultados indican que las estrategias utilizadas influyen en el rendimiento positivo de los participantes, y la evaluación muestra que la interacción entre el estudiante y el docente es clave para el éxito del curso. En este estudio exploratorio se explica el proceso eficaz para diseñar e implementar un curso en línea sobre las ciencias del suelo.

Characterization and role of Amazonian fruit crops in family farms in the provinces of Sucumbíos and Orellana (Ecuador)

Abstract Fruit crops in the northern Ecuadorian Amazon region are part of the crop diversity found in a production system called "chakra" that is known as a traditional and diverse agroforestry system. The aim of this study was to characterize the Amazonian fruits crops present in production farms with cacao (Theobroma cacao), coffee (Coffea canephora) and silvopastoral systems located in the provinces of Orellana and Sucumbíos. The information was obtained through targeted surveys and direct observations in the field. The results indicated that in the two provinces, producers establish from 1 to 19 fruit crop species in their plots, being the farms of less than 10 hectares the most diverse. In most farms, the predominant fruit crops in these production systems are avocado (Persea americana), citrus (Citrus spp.), coconut (Cocos nucifera), ice-cream-bean (Inga edulis), papaya (Carica papaya), peach palm (Bactris gasipaes) and pineapple (Ananas comosus). These crops are associated with cacao, coffee, monocultures, silvopastoral systems, or dispersed outside these systems. On the other hand, other species have been introduced and are considered as fruit crops with market potential, namely, fig (Ficus carica), grapefruit (Citrus x paradisi), passion fruit (Passiflora edulis) and star gooseberry (Phyllanthus acidus). Fruit crop production is mainly destined for self-consumption and animal feed; however, the surplus is sold to generate an economic income.

Resumen En la región norte de la Amazonía ecuatoriana, los frutales hacen parte de la diversidad de cultivos que se encuentran en los sistemas de producción denominados chakra, que constituye un sistema agroforestal tradicional y diverso. El objetivo de este estudio fue caracterizar los frutales amazónicos presentes en las fincas productoras de cacao (Theobroma cacao), café (Coffea canephora) y con sistemas silvopastoriles, ubicadas en las provincias de Orellana y Sucumbíos. La información se basó en encuestas dirigidas y en la observación directa en el campo. Los resultados indicaron que, en las dos provincias, los productores establecen entre 1 y 19 especies de frutales en sus parcelas, y que las fincas de menos de 10 hectáreas son las más diversas. En la mayoría de ellas, los frutales predominantes en los sistemas de producción son aguacate (Persea americana), cítricos (Citrus spp.), coco (Cocos nucifera), chontaduro (Bactris gasipaes), guaba (Inga edulis), papaya (Carica papaya) y piña (Ananas comosus). Estos cultivos están asociados con café, cacao, sistemas silvopastoriles, monocultivos, o dispersos fuera de estos sistemas. Por otro lado, se han introducido especies consideradas frutales con potencial de mercado, entre las que se encontraron grosella (Phyllanthus acidus), higo (Ficus carica), maracuyá (Passiflora edulis) y pomelo (Citrus x paradisi). En su mayoría, la producción de los frutales está destinada al autoconsumo y la alimentación de los animales de la finca; sin embargo, el excedente se vende, para generar un ingreso económico.

Edaphoclimatic characterization of the productive zone of Tahiti lime (Citrus latifolia Tanaka) in Tolima (Colombia) affected by a physiopathy

Abstract In the department of Tolima (Colombia), citrus orchards affected by a physiopathy that induces a progressive death of the trees was observed. A physiopathy is a plant damage or disorder caused by abiotic origin agents. A similar problem called wood pocket was reported for the United States and Mexico. In California (U.S.A.), the problem was solved with the use of resistant rootstocks. In Saudi Arabia and Oman this result could not be replicated. It has been reported that this physiological disorder is enhanced in dry hot climate, typical condition found in the study area: high temperatures, water deficit, high soil infiltration rates and poor irrigation management. These factors lead to plants having low water availability to meet the high atmospheric demand, causing a state of stress during the productive season. The citrus production area shows eight months of water deficit during the year, and the evapotranspiration exceeds in 34 % the precipitation. In very dry years, as 2015, the anomaly may occur throughout the year. Likewise, the soil storage capacity does not exceed 7.3 %, i.e. a lower value than the 14 % reported for sandy soils. It is necessary to adjust the irrigation programs in affected and unaffected areas to prevent this problem.

Resumen En el departamento del Tolima (Colombia) se han observado huertos afectados por una fisiopatía que induce una muerte progresiva de los árboles. Una fisiopatía es un daño o trastorno vegetal, provocada por agentes de origen abiótico. En Estados Unidos y México se ha reportado una problemática similar, denominada wood pocket. En California (EE. UU.), el inconveniente se solucionó con el uso de patrones resistentes, pero en Arabia Saudita y Omán este resultado no fue replicable. Se ha reportado que este desorden fisiológico se potencia en clima cálido seco, condición propia de la zona de estudio: altas temperaturas, déficit hídrico, altas velocidades de infiltración del suelo y un mal manejo del riego. Estos factores llevan a que las plantas tengan una baja disponibilidad hídrica para suplir la alta demanda atmosférica, lo que causa un estado de estrés durante la época productiva. La zona productora presenta un déficit hídrico hasta ocho meses en el año, y la evapotranspiración supera en un 34 % a la precipitación. En años muy secos, como 2015, la anomalía puede presentarse durante todo el año. Asimismo, la capacidad de almacenamiento del suelo no supera el 7,3 %, inferior al 14 % reportado para suelos arenosos. Es necesario ajustar los programas de riego tanto en zonas afectadas como no afectadas, con el fin de prevenir el problema.

Meloidogyne exigua (Meloidogynidae) em clones de seringueira em duas épocas do ano

Abstract Meloidogyne exigua Goeldi, race 3 (Nematoda: Tylenchida: Meloidogynidae), has become an important pest for rubber tree plantations. Thus, the objective of this work was to monitor its infestation in rubber tree plantations and to determine the spatial distribution of the population in the roots of clones GT 1 and RRIM 600, without identification of the rootstock, in two periods of 2013, in the municipality of Itiquira, MT, Brazil. In May, 264 samples were collected, and in November, 227 samples were collected in the total area of 6,646 hectares planted with 22 clones, which were used for the interpolation by the kriging method for mapping infestations in the total area. Based on this planting map, the plots of the two evaluated clones were cut, resulting in 55 samples in May (clone GT 1 = 29 and RRIM 600 = 26 samples) and 52 in November (clone GT 1 = 27 and RRIM 600 = 25 samples), in a total area of 2,409 hectares. With a GNSS device, each sampling point was identified, and roots of the rubber tree were collected at 0.10 m depth. For the two clones, the infestations in May were larger than those recorded in November. The Spatial Dependency Index (IDE) between collections collected in May and November of 2013 were moderate. The cross-validation of the data was not satisfactory, due to the high variation of infestations.

Resumo Meloidogyne exigua Goeldi, raça 3 (Nematoda: Tylenchida: Meloidogynidae), tem se tornado importante para plantios de seringueira. Assim o objetivo deste trabalho foi monitorar sua infestação em plantio de seringueira e posteriormente realizar a distribuição espacial da população nas raízes dos clones GT 1 e RRIM 600, sem identificação do porta-enxerto, em duas épocas de 2013, no município de Itiquira, MT, Brasil. Em maio foram coletadas 264 e em novembro 227 amostras na área total de 6.646 hectares plantados com 22 clones, utilizados para a interpolação pelo método da krigagem, para elaboração do mapa de infestação na área total. Baseado neste mapa do plantio, foram recortados os talhões dos dois clones avaliados, representados com 55 amostras em maio (clone GT 1 = 29 e RRIM 600 = 26 amostras) e 52 em novembro (clone GT 1 = 27 e RRIM 600 = 25 amostras), em área total de 2.409 hectares. Com um aparelho GNSS foi identificado cada ponto amostral, coletando-se raízes da seringueira a 0,10 m de profundidade. As infestações em maio, nos dois clones, foram maiores do que em novembro. Os Índices de Dependência Espacial (IDE) entre as coletas realizadas em maio e novembro de 2013 foram moderados. A validação cruzada dos dados não foi satisfatória, devido a alta variação de infestações.

Methods of extraction refining and concentration of fish oil as a source of omega-3 fatty acids

Abstract Fish oil is an industrial product of high nutritional value because of its Omega-3 polyunsaturated fatty acids content, currently valued for their beneficial effects on health. Studies and advances made since year 2000 on fish oil extraction from several fish species, its refining and polyunsaturated fatty acids concentration are reviewed in this article. Extraction techniques range from conventional technologies such as wet pressing and extraction using solvents, to more recently proposed technologies such as supercritical fluids and fish silage. Moreover, although refining is performed by traditional methods, there are new technologies with potential to be applied on fish oil. On the other hand, interest in omega-3 polyunsaturated fatty acids concentration has increased and several techniques such as winterization, enzymatic methods, super-critical fluids fractionation, complex formation with urea, fractionation by chromatographic methods and concentration by membranes have been proposed. The information collected indicates a trend to combine different conventional and emerging technologies to improve product yields and purity.

Resumen El aceite de pescado es un producto industrial de alto valor nutricional, por su contenido de ácidos grasos poliinsaturados omega-3, valorados en la actualidad por sus efectos benéficos en la salud. En este artículo se revisan estudios y avances realizados desde el año 2000 en la extracción de aceite de pescado de diversas especies, su refinación y concentración de ácidos grasos. Las técnicas de extracción van desde tecnologías convencionales, como prensado húmedo y extracción por solventes, hasta otras propuestas más recientemente, como fluidos supercríticos y ensilaje de pescado. Así mismo, aunque la refinación se realiza con métodos tradicionales, existen nuevas tecnologías con potencial para aplicarse en aceite de pescado. Por otro lado, el interés en la concentración de ácidos omega-3 ha crecido y se han propuesto varias técnicas, como hibernación, métodos enzimáticos, fraccionamiento por fluidos supercríticos y por métodos cromatográficos, formación de complejos con urea y concentración por membranas. La información recopilada indica una tendencia a combinar diferentes tecnologías convencionales y emergentes, con el fin de mejorar los rendimientos y la pureza del producto obtenido.