Management of Fertigation in Horticultural Crops through Automation with Electrotensiometers: Effect on the Productivity of Water and Nutrients.

Water and nutrient requirements of horticultural crops are influenced by different factors such as: Type of crop, stage of development and production system. Although greenhouse horticultural crops are more efficient in the use of water and fertilizers compared to other production systems, it is necessary increase efficiency for which individualized fertigation strategies must be designed for each greenhouse. The automation of fertigation based on the level of soil moisture allows optimization of management. The objective of this work was to determine the influence of the activation command of fertigation with electrotensiometers and the characteristics of the greenhouse on the productivity of the crop and the efficiency of use of water and nutrients in a sweet pepper crop. The trial was developed in two greenhouses. Four treatments were studied, combination of who two-factor: Soil matric potential (SMP) (SMP-10: Automatic activation of irrigation to -10 kPa and SMP-20: Automatic activation of irrigation to -20 kPa) and greenhouse characteristics (G1 and G2). The nutritive solution applied was the same in all treatments. The yield and volume of water and nutrients applied were determined, calculating the productivity of the water (WP), as well as productivity the nutrients. The fertigation activation threshold of -10 kPa presented the best results, increasing the yield and conserving WP and nutrient productivity with respect to -20 kPa in both greenhouses. The automation of irrigation with electrotensiometers allowed the application of different volume of fertigation demanded by the crop in each greenhouse, equalizing the WP and nutrient productivity without producing drainage. The pepper crop in the greenhouse G1 presented greater vegetative development, higher yield and demanded a greater volume of fertigation than G2 regardless of the activation threshold. This was due to the fact that the soil matric potential after irrigation in greenhouse G1 was closer to zero, being able to conclude that not only the soil matric potential threshold of irrigation activation has an influence on crop, but also the potential registered after irrigation. Soil matric potentials closer to zero are more productive.

Territorio y saber en disputa. La controversia limítrofe Chileno-Argentina sobre los Andes / Territory and knowledge in conflict. The border dispute of Chile and Argentina in the Andes

Utilizando las alternativas de la disputa fronteriza entre Argentina y Chile en la Patagonia, se ofrece una reflexión y ejemplo del uso del saber geográfico para la reivindicación de soberanías territoriales. Con los presupuestos de la historia social de la ciencia y de la historia cultural, se muestran los condicionamientos que influyeron en los argumentos de las partes, como en la resolución política de una querella territorial que hace más de cien años, como en la actualidad, obligó a Chile a recurrir a instancias internacionales para determinar sus límites y asegurar derechos. Una situación que primero implicó resolver sobre el conocimiento geográfico de la naturaleza disputada, tarea que sin embargo no garantizó asegurar la pretensión nacional pues, en definitiva, el árbitro llamado a decidir no falló basándose solo en el conocimiento adquirido (AU)

Through the study of the border dispute between Argentina and Chile in Patagonia, the article offers a reflection and an example of the use of geographical knowledge in claiming territorial sovereignty. Based on the social history of science and cultural history, it presents the conditionings that influenced the arguments of both countries, and the political resolution of a territorial quarrel that over a hundred years ago, and also nowadays, forced Chile to resort to international bodies to determine its limits and ensure its rights. This situation implied a decision on the geographical knowledge of the disputed nature. This argument, however, did not bolster the Chilean position, since the referee called upon to decide the dispute, after revised several sources and not only the geographical knowledge claimed by Chile (AU)

En el Chile decimonónico: los enfermos y sus patologías / Chile in nineteenth-century: the sick and their pathologies

Diversas fuentes permiten identificar las enfermedades de los chilenos y los remedios con que las enfrentaban a comienzos del siglo XIX. A través de ellas se configura un patrimonio cultural y social todavía poco conoido.

En el Chile decimonónico: los enfermos y sus patologías / Chile in nineteenth-century: the sick and their pathologies

Diversas fuentes permiten identificar las enfermedades de los chilenos y los remedios con que las enfrentaban a comienzos del siglo XIX. A través de ellas se configura un patrimonio cultural y social todavía poco conoido. (AU)