https://revistaschilenas.uchile.cl/handle/2250/43758 [0-9]{4} Sun, 10 May 2026 17:47:51 GMT 2026-05-10T17:47:51Z https://revistaschilenas.uchile.cl:443/bitstream/id/8233299a-83b4-45bf-ab7d-210a012bfafa/ https://revistaschilenas.uchile.cl/handle/2250/43758 https://revistaschilenas.uchile.cl/handle/2250/225307 EVALUATION OF TWO SUBSOILERS IN DIRECT DRILLED SOILS; EVALUACIÓN DE DOS DESCOMPACTADORES EN SIEMBRA DIRECTA Background: No tillage is a widely used tillage system in Argentinean extensive grain production. Despite their benefits, the risk of soil compaction is still a critical point. Deep tillage is a valid option to solve compaction problems and several types of deep tillage agricultural equipment are available. Nevertheless, accurate knowledge on their energetic performance rates and agricultural parameters is still limited. Objectives: a) determine energy requirements of different subsoiling equipment, b) evaluate the effect of different subsoilers on physical soil properties and c) analyze the recompaction of subsoiled soil. Methods: A field experiment in a direct drill system (Typical Argiudol soil type) was carried out. Treatments were: a) without decompaction, b) paratill and c) chisel with flexible and rigid shanks. Traction, soil disturbance and specific resistance were measured. After tillage, physical soil properties were assessed. Results: Traction and specific resistance were 5,5% and 11,5% greater in chisel. In general, soil density and penetration resistance were reduced by subsoiling but these benefits do not persist after 18 months. Conclusions: Paratill performance in direct-drilled soils is higher than chisel performance. Subsoiling of direct-drilled soils improve soil physical properties. ; Antecedentes: La siembra directa se ha generalizado en los sistemas de producción de cultivos extensivos en Argentina. Esta técnica presenta varias ventajas, aunque uno de sus aspectos críticos lo constituye el riesgo de compactación. La labranza vertical profunda es una alternativa viable para solucionar los problemas de compactación. Existen numerosas opciones de descompactadores, sin que se disponga, para la mayoría de ellos, de información sobre sus prestaciones, en términos energéticos y agronómicos. Objetivos: a) determinar los requerimientos de energía de diferentes equipamientos de descompactación, b) valorar el efecto de distintos diseños de descompactadores sobre las propiedades físicas del suelo, c) analizar la recompactación de suelos descompactados. Métodos: Se realizó un experimento sobre un suelo Argiudol típico, contrastándose tres tratamientos: a) sin descompactar, b) descompactado con paratill y c) descompactado con cincel de arcos rígidos y flexibles. Se cuantificó el esfuerzo de tracción, el área de suelo removida y la resistencia específica al laboreo. Luego de realizadas las labores se evaluaron las propiedades físicas del suelo. Resultados: El cincel demandó un 5,5% más de esfuerzo de tracción y tuvo 11,2% más de resistencia específica al laboreo. El subsolado disminuyó la densidad aparente y la resistencia a la penetración, aunque esas diferencias se pierden a los 18 meses. Conclusiones: La descompactación de suelos en siembra directa con paratill es energéticamente más eficiente que con cincel. Las labores de descompactado, ya sea por medio del cincel como del paratill, realizadas sobre un suelo con historia en siembra directa, mejoran las propiedades físicas del suelo: densidad aparente y resistencia a la penetración. https://revistaschilenas.uchile.cl/handle/2250/225307 https://revistaschilenas.uchile.cl/handle/2250/225306 TOXICITY OF LEAF POWDERS OF MEXICAN TEA (Chenopodium ambrosioides L.) AND BOLDO (Peumus boldus MOL.) SINGLY AND MIXED WITH CALCIUM CARBONATE AGAINST MAIZE WEEVIL (Sitophilus zeamais MOTSCHULSKY); TOXICIDAD DE POLVOS DE FOLLAJE DE PAICO (Chenopodium ambrosioides L.) Y BOLDO (Peumus boldus MOL.) SOLOS Y EN MEZCLA CON CARBONATO DE CALCIO SOBRE GORGOJO DEL MAÍZ (Sitophilus zeamais MOTSCHULSKY) Stored grains are damaged by insect pests like maize weevil (Sitophilus zeamais Motschulsky; Coleoptera: Curculionidae). This study aimed to assess the biocidal properties of powdered foliage of Chenopodium ambrosioides L. and Peumus boldus Molina, both singly and mixed with calcium carbonateat 0.5%, 1% and 2% (w/w), against Sitophilus zeamais Motschulsky under laboratory conditions. In 250 mL jars, 250 g of maize seeds were mixed with the treatments and then infested with 10 insect couples. Mortality and emergence of adult insects (F1), grain germination, fumigant and repellent effects ofpowders were the evaluated parameters. The experimental design was completely randomized with 19 treatments, with five replicates. The whole methodology was repeated three times in different days. The highest mortality (100%) was obtained with plant powders alone at 2% (w/w) and the lowest adult insect emergence (0.2 y 0.1%) was reached with P. boldus powder alone at 1% and 2% (w/w). Seed germination was not affected by Ch. ambrosioides powder, while the use of P. boldus powder decreased germination respect to the untreated control. The fumigant effects of powders decreased as the proportion of calcium carbonate increased. Powders from both species mixed with calcium carbonate were repellent to S. zeamais. It was concluded that P. boldus powder and Ch. ambrosioides powder, singly and mixed with calcium carbonate, have insecticidal contact action, as well as fumigant and repellent effects on S. zeamais, and that they cause no significant effect on maize germination. ; Los cereales almacenados son dañados por insectos plaga, tales como el gorgojo del maíz (Sitophilus zeamais Motschulsky; Coleoptera: Curculionidae). El objetivo de este experimento fue evaluar en laboratorio polvos de follaje de Chenopodium ambrosioides L. y Peumus boldus Molina, solos y en mezclacon carbonato de calcio en concentraciones de 0,5%, 1% y 2% (p/p) para el control de S. zeamais. En frascos de 250 mL se mezclaron 200 g de semillas de maíz con los tratamientos que luego fueron infestados con 10 parejas de insectos. Las variables evaluadas fueron mortalidad y emergencia de insectosadultos (F1), germinación de los granos y efecto fumigante y repelente de los polvos. El diseño experimental fue completamente al azar, con 19 tratamientos, con cinco repeticiones; toda la metodología se repitió tres veces en diferentes días. La mayor mortalidad (100%) se obtuvo con los polvos vegetales solos al 2% (p/p) y las menores emergencias de insectos adultos (0,2 y 0,1%) se lograron con P. boldus solo al 1% y 2% (p/p). La germinación de las semillas no se vio afectada por los polvos de Ch. ambrosioides, mientras que con P. boldus disminuyó en relación al testigo sin tratar. El efecto fumigantede los polvos disminuyó cuando aumentó la proporción de carbonato de calcio y los polvos de Ch. ambrosioides y P. boldus solos y mezclados con carbonato de calcio mostraron repelencia para S. zeamais. Se concluyó que los polvos de P. boldus y Ch. ambrosioides solos y en mezcla con carbonato de calcio tienen efecto insecticida de contacto y efecto fumigante y repelente contra S. zeamais sin afectar sinificativamente la germinación del maíz. https://revistaschilenas.uchile.cl/handle/2250/225306 https://revistaschilenas.uchile.cl/handle/2250/225308 EFFECT OF SOLAR RADIATION ON THE DISAPPEARANCE OF EGERIA DENSA (HYDROCHARITACEAE) IN THE WETLANDS OF THE CRUCES RIVER (VALDIVIA, CHILE); EFECTO DE LA RADIACIÓN SOLAR EN LA DESAPARICIÓN DE EGERIA DENSA PLANCH. (HYDROCHARITACEAE) DESDE EL HUMEDAL DEL RÍO CRUCES (VALDIVIA, CHILE) Background: The submersed macrophyte Egeria densa Planch., locally known as "luchecillo", disappeared from the wetlands of Rio Cruces or Nature Sanctuary Carlos Anwandter (Valdivia, Chile) in October 2004. It was established that this phenomenon occurred due to the chemical pollution coming from industrial origin. Objectives: Analyze an alternative hypothesis that identifies the increase in the intensity of solar radiation as the cause of the reduction of Egeria densa populations, especially in the UV region. Methods: Cultures of Egeria densa were covered by Raschel mesh, mylar filter, acetate filter, while one of the cultures was not covered. During the experiment the Egeria densa chlorophyll content was determined by a SPAD-meter. Results: The experimental study showed that the damage was not likely to be attributed to UV radiation. However, it was determined that the intensity of solar radiation affected the development of Egeria densa by reducing chlorophyll content in direct proportion to exposure time. Conclusions: An increase in sunlight intensity or other unknown radiation could have caused the death of Egeria densa in shallow waters. The absence of a protective epidermis that filters certain wavelengths in Egeria densa leaves could facilitate the deleterious effect of radiation under prolonged exposure at low tide.; Antecedentes: Egeria densa Planch., localmente conocida como "luchecillo" desapareció del humedal Santuario de la Naturaleza "Carlos Anwandter" en el río cruces (Valdivia, Chile), en octubre del año 2004. Se estableció que la causa del fenómeno era una contaminación química de origen industrial. Objetivos:Analizar una hipótesis alternativa que considera que la causa de la reducción de las poblaciones de Egeria densa fue un aumento de la intensidad de la radiación solar, especialmente en la región UV. Métodos: Se trabajó con cultivos cubiertos por malla Raschel, filtro UV-B mylar, filtro de acetato y una réplica sin cubierta. Durante el experimento se determinó la clorofila foliar con un medidor SPAD. Resultados: Según el estudio experimental la causa del daño no sería atribuible a la radiación UV, pero demuestra que la intensidad de la radiación solar afectó el desarrollo de Egeria densa, reduciendo su contenido de clorofila, proporcionalmente al tiempo de exposición. Conclusiones: Se concluye que un aumento de la intensidad lumínica del sol o de otra radiación desconocida pudo provocar la muerte de Egeria densa en lugares someros y su profundización, en los cauces más profundos. La ausencia de una epidermis protectora y filtradora de algunas longitudes de onda de las hojas de Egeria densa pudo facilitar la acción deletérea de la radiación, junto a una exposición prolongada durante la bajamar.  https://revistaschilenas.uchile.cl/handle/2250/225308 https://revistaschilenas.uchile.cl/handle/2250/219284 METHODOLOGY FOR AVOCADO (Persea americana Mill.) ORCHARD EVALUATION USING DIFFERENT MEASUREMENT TECHNOLOGIES; METHODOLOGY FOR AVOCADO (Persea americana Mill.) ORCHARD EVALUATION USING DIFFERENT MEASUREMENT TECHNOLOGIES Avocado crop (Persea americana Mill.) is of great commercial importance due to its high profitability. However, it is being affected by various diseases and pests that affect yield and reduce fruit quality. The aim of this research was to develop methodologies for the evaluation of avocado plantations using different non-destructive technologies for rapid phenotyping and early detection of the incidence of diseases or damage due to stress in the stem. A plot of 0.7 ha. was evaluated, with a total of 44 individuals using Field-Map technology (dasometric and morphological characterization), RGB-multispectral images from Remotely Piloted Aircraft System (RPAS) (rapid phenotyping), while 15 individuals were evaluated using tomography (assessment of the internal state of the stem). The results with tomography indicated that there is a tree with wood rot of 14% with a lower acoustic speed with respect to the other trees evaluated. A high correlation was observed between the dasometric variables (r- earson from 0.63 to 0.98) estimated with Field-Map [crown base height, crown projection (m2) and total height] and with RPAS (height, perimeter and area). The vegetation indices do not have a direct correlation with the dasometric variables; five of the indices have a high contribution to variability except for the Normalized Difference Red Edge (NDRE). It can be concluded that the technologies used in this study would help to perform evaluations with a greater number of reliable and precise data with respect to the information obtained in a traditional way, while they can be replicated in commercial plots or research studies of different perennial crops, generating useful information for management decisions and crop evaluation.; Avocado crop (Persea americana Mill.) is of great commercial importance due to its high profitability. However, it is being affected by various diseases and pests that affect yield and reduce fruit quality. The aim of this research was to develop methodologies for the evaluation of avocado plantations using different non-destructive technologies for rapid phenotyping and early detection of the incidence of diseases or damage due to stress in the stem. A plot of 0.7 ha. was evaluated, with a total of 44 individuals using Field-Map technology (dasometric and morphological characterization), RGB-multispectral images from Remotely Piloted Aircraft System (RPAS) (rapid phenotyping), while 15 individuals were evaluated using tomography (assessment of the internal state of the stem). The results with tomography indicated that there is a tree with wood rot of 14% with a lower acoustic speed with respect to the other trees evaluated. A high correlation was observed between the dasometric variables (r-Pearson from 0.63 to 0.98) estimated with Field-Map [crown base height, crown projection (m2 ) and total height] and with RPAS (height, perimeter and area). The vegetation indices do not have a direct correlation with the dasometric variables; five of the indices have a high contribution to variability except for the Normalized Difference Red Edge (NDRE). It can be concluded that the technologies used in this study would help to perform evaluations with a greater number of reliable and precise data with respect to the information obtained in a traditional way, while they can be replicated in commercial plots or research studies of different perennial crops, generating useful information for management decisions and crop evaluation. https://revistaschilenas.uchile.cl/handle/2250/219284