Abstract: Using the reasoned nitrogen (N) fertilization method in potato crops (Solanum tuberosum L.) requires the validation of its parameters under the probable conditions of crop response. A field experiment in an Andisol was established to assess the parameters of this method and the nitrogen utilization efficiency of the crop. To describe the crop N response, five statistical models were used. Dry matter production and nutrient concentration were measured in tubers, leaves, fruits and roots. At both the beginning and the end of the experiment soil samples were collected to evaluate the mineral N. The quadratic-potential model was the most appropriate to describe the positive response of the potato crop to available nitrogen, from an initial level of nitrogen (the control, zero application ) to a maximum application of 200 kg N ha-1. The relationship between the N doses and the potato yield reached a physical optimal of productivity at a rate of 228 kg N ha-1. Higher rates (300 kg N ha-1) resulted in a decrease in yield, generating phytotoxicity for cultivation. This variation allowed us to evaluate the reasoned application method under different nitrogen availabilities (deficiency, optimal and above-optimal) in addition to the variation of the parameters generated.

Abstract: The residual value of phosphorus addition is described by two reactions: a quick initial reaction followed by a slower reaction over time. In this study, the residual effect of two P sources was evaluated: monopotassium phosphate (MKP) and triple superphosphate (TSP) added to soils from Ecuador and Chile with contrasting soil P retention capacity. Olsen-P extractability was measured and compared in soil samples 1, 2, 4, 8, 15, 45, 90, 180 and 360 days after the addition. The Olsen-P extracted at 24 hours after the P addition varied among soils, and extracted between 10 and 66% of the P added depending upon the soil, with lower extraction values in soils with high P retention capacity. When the source was TSP, only approximately 70% of P was extracted compared to that extracted when MKP was added. After the phosphate addition there was a clear initial effect followed by a progressive loss of Olsen-P extractability. Furthermore, over time, a state of quasi-equilibrium or a stationary state become evident in which the loss of P extractability was minimal. When the initial effect was removed, as a point that characterizes different types of soils, the loss of P extractability was similar among soils, and reflects the amount of phosphate added despite the type of fertilizer used.

This activity is not something that is currently being carried out this type of agriculture has been giving many years ago, recently has taken more relevance as it is contributing to food sovereignty, we know that within 30 years approximately we have to produce twice as much Food due to an increasingpopulation, it is estimated that by 2050 we will have twice the currentpopulation, therefore this type of agriculture will help to meet these food requirements in the future. The methodology used in this research to identify the urban farmers was the Snowball or snowball methodology, after which the respective surveys were carried out, with which it was possible to determine through the principal components analysis (ACP) that there are two major items Dedicated to this activity in the city of Valdivia as are the production of vegetables and ornamental plants, in addition to being able to conclude that there are three well marked groups of which the ones with more experience and with a basic education manage to obtain higher income than the farmers Urban areas that have a complete university education level.

Esta actividad no es algo que se esté realizando actualmente, este tipo de agricultura se viene dando hace muchos años, recientemente ha tomado mayor relevancia ya que está contribuyendo a la soberanía alimentaria, sabemos que dentro de 30 años aproximadamente tenemos que producir el doble de alimentos debido a una población en aumento, se estima que para el 2050 tendremos el doble de la población actual, por tanto este tipo de agricultura ayudará a cubrir estos requerimientos alimenticios a futuro. La metodología utilizada en esta investigación para identificar a los agricultores urbanos fue la metodología Snowball o bola de nieve, posterior a esto se realizaron las encuestas respectivas, con la que se pudo determinar mediante el análisis de componentes principales (ACP) que existen dos grandes rubros dedicados a esta actividad en la ciudad de Valdivia, como son la producción de hortalizas y plantas ornamentales, además de poder concluir que existen tres grupos bien marcados de los que cuentan con mayor experiencia y con una educación básica logran obtener mayores ingresos que los agricultores urbanos que cuentan con un nivel de educación universitaria completa.

Background: Culture is defined by the Webster's dictionary as acquaintance with and taste infine arts, humanities, and broad aspects ofscience as distinguished from vocational and technical skills. Aim: To assess the general cultural knowledge of university students. Material andMethods: A test containing 58 questions about art, national and universal literature, national and universal history, mythology science and trivial national issues was designed and applied to 251 medical students in Santiago (149 from first year and 86 from fifth year, Universidad de Chile) and 138 agronomy students in Valdivia (61 from first year and 77 from fifth year, Universidad Austral de Chile). Results: All students answered the test. Medical students from first and fifth year omitted 19 and 15% of questions respectively The figures for first and fifth year agronomy students were 23% each. The percentage of corred answers among first and fifth year medical students was 50 and 59% respectively. The figures for first and fifth year agronomy students were 39 and 44% respectively. The questions with higher rates of corred answers were those about trivial issues. Conclusions: There was a high rate of omissions and wrong answers about general cultural issues among university students particularly in national cultural subjects.

Given the importance of nitrogen fertilization in the production of tulip (Tulipa gesneriana L.) bulbs and the limited information relative to this crop in Chile, a study was conducted to characterize its growth and nitrogen uptake. Tulips were cultivated outdoors and included two deflorations. Bulbs of the variety negrita, 7-9 cm, were planted. A randomized complete blocks design was used with five treatments: 0, 70, 120, 160 and 200 kg N ha-1 and three replications. Periodically, plants were sampled to analyze their growth and N content. Accumulation of dry matter and N of the entire crop and individual plants were not significantly affected (p>0.05) by nitrogen fertilization, undoubtedly because of the high N supply from the soil. However, bulbs increased N concentration at harvest (p<0.05) and reached marketable size. Daily growth rates and N uptake by plants and individual organs exhibited similar patterns. Nitrogen fertilization should be divided: in early winter to promote later leaf expansion and then in full spring to cover the period of maximum crop growth and N uptake.

Dada la importancia de la fertilización nitrogenada en la producción de bulbos de tulipán (Tulipa gesneriana L.) y la limitada información relacionada con este cultivo en Chile, se realizó un ensayo para caracterizar su crecimiento y absorción de nitrógeno. El cultivo se realizó al aire libre e incluyó dos desbotonaduras. Se plantaron bulbos variedad negrita, tamaño 7-9 cm y se usó un diseño de bloques completos al azar con cinco tratamientos: 0, 70, 120, 160 y 200 kg N ha-1 y tres repeticiones. Se realizaron muestreos periódicos de plantas para analizar su crecimiento y contenido de N. La acumulación de materia seca y N del cultivo y de órganos individuales no fue afectada significativamente (p>0.05) por la fertilización nitrogenada, debido seguramente a un alto suministro de N del suelo. Sin embargo, los bulbos aumentaron su concentración de N a la cosecha (p<0.05) y alcanzaron un tamaño comercial. Las tasas diarias de crecimiento y absorción de N de plantas y órganos individuales presentaron patrones similares. La fertilización nitrogenada debiera fraccionarse: temprano en el invierno para promover la posterior expansión foliar, y luego en plena primavera para cubrir el período de máximo crecimiento y absorción de N del cultivo.

To evaluate the variation of the same type of soils to liming, a study was carried out in selected soil samples from soils derived from volcanic ashes. The parameters evaluated were the variation of initial pH (4.76 to 5.03), the initial content of exchangeable bases (2.3 to 8.3 cmol+ kg-1) and organic matter content (11.6 to 26.8 g 100 g-1). The initial pH level and organic matter affected the soil acidity parameters evaluated (buffering capacity, exchangeable Ca and exchangeable Al content). For agronomic purposes, it was established that for each gram of CaCO3 applied to a kilogram of soil, the pH is increased 0.2 units, exchangeable Ca content increased 70%, and the exchangeable Al content decreased to 50% of its previous value, and there is a pH buffering capacity and exchangeable Ca content in the evaluated soils dependent on its organic matter content.

Con el objetivo de evaluar la variación de un mismo tipo de suelo a la adición de cal, se realizó un estudio en muestras seleccionadas de suelos derivados de cenizas volcánicas. Los parámetros evaluados fueron: variación del pH inicial (4,76 a 5,03), contenido inicial de bases de intercambio (2,3 a 8,3 cmol+ kg-1) y el contenido de materia orgánica (11,6 a 26,8 g 100 g-1). El nivel inicial de pH y materia orgánica afectaron los parámetros de acidez del suelo evaluados (capacidad tampón, Ca intercambiable y contenido de Al intercambiable). Para propósitos agronómicos, se determinó que por cada gramo de CaCO3 aplicado por kilogramo de suelo, el pH aumentó 0,2 unidades, el contenido de Ca intercambiable aumentó en un 70% y el contenido de Al intercambiable disminuyó en un 50% de su valor previo, y que existe una variación de la capacidad tampón de pH y del contenido de Ca intercambiable en los suelos dependiendo del contenido de materia orgánica.

This research was conducted for two years to evaluate magnesium fertilizer application (0, 24, 48 and 96 kg ha-1 year-1 of Mg) on a permanent pasture composed by Lolium perenne and Trifolium repens as an agronomic alternative of hypomagnesaemia management in grazing herds. The effect on magnesium, calcium, potassium and sodium concentration in the pasture dry matter and the ratio between cations were evaluated. The research was carried out on an Hapludand (Valdivia serie) with an initial available magnesium content of 0.8 cmol c kg-1. Pasture dry matter production was not affected by magnesium fertilization, nevertheless, the concentration of magnesium in the pasture dry matter increased proportionally to the magnesium applied. A weighed average showed an increase of 0.006 and 0.012 g kg-1 of dry matter for each kg of magnesium applied during the first and second year, respectively. In addition, the magnesium fertilization decreased the calcium dry matter concentration, but it did not affect potassium and sodium dry matter concentration. The ratios between calcium/magnesium, potassium/magnesium and sodium/magnesium decreased with the increase of the magnesium fertilization rate.

Como una alternativa de manejo agronómico de la hipomagnesemia en rebaños a pastoreo se estudió, durante dos años, el efecto de la fertilización magnésica (0, 24, 48 y 96 kg ha-1 año-1 de Mg) sobre la concentración de magnesio, calcio, potasio y sodio y sus relaciones en la materia seca del forraje cosechado de una pradera permanente compuesta por Lolium perenne y Trifolium repens. El ensayo se realizó en un suelo Hapludand (Serie Valdivia) con un nivel inicial de 0,8 cmol c kg-1 de Mg. No se detectó un efecto de la fertilización magnésica sobre la producción de materia seca de la pradera, pero la concentración de magnesio en la materia seca se incrementó proporcionalmente a la dosis de magnesio aplicada. Considerando el promedio ponderado anual el aumento de la concentración de magnesio fue de 0,006 y 0,012 g kg-1 de materia seca por cada kg de magnesio aplicado, durante el primero y segundo año, respectivamente. La fertilización magnésica disminuyó la concentración de calcio, pero no afectó la concentración de potasio ni de sodio en la materia seca del forraje cosechado. Las relaciones entre Ca/Mg, K/Mg y Na/Mg en general disminuyeron en la medida que aumentó la dosis de fertilización con magnesio.