ABSTRACT: The substantial generation of organic waste together with increasing interest in developing sustainable agriculture heralds an opportunity for mobilizing the recycling of these materials as a source of organic matter and nutrients into a viable management strategy option. A field experiment was conducted to evaluate the use of compost derived from waste produced by the winery and distillery industries in a drip-irrigated melon crop traditionally grown in the area where these wastes are generated. A randomized complete block design was used with four treatments consisting of three different dose levels of compost: 7 (D1), 13 (D2) and 20 (D3) t ha−1 and a control (D0) without the application of compost. The effects of these treatments on plant growth, nitrogen (N) and phosphorus (P) accumulation as well as fruit yield and quality were studied. The application of compost produced a slight increase in plant biomass accompanied by changes in the relative growth rate (RGR) and net assimilation rate (NAR). As a result, a significant improvement in fruit yield was observed in the plots amended with D2, which met all the requirements to obtain elevated yields. In terms of environmental correctness applications were below the limits established by a number of impact indexes. Additionally, the application of compost improved fruit quality resulting in an enhancement of Brix degrees. Although the potential effects of N and P derived from compost were partially masked by other inputs of these nutrients into the system (N in irrigation water, P supplied through fertigation), an effect of P was observed resulting in an increase in the number of individual fruits in the plots amended with compost.

Abstract In this study, the reflections of two future mathematics teachers is analyzed through the professional problems related to teaching and learning school algebra that they identify, define, and face during teaching practice. For this purpose, we planned and implemented a teacher education module in the practicum of an undergraduate mathematics and physics program in Colombia, under the realistic theory of teacher education to promote a thoughtful ALaCT cycle. Following the approach of qualitative and interpretative research and using content analysis, the productions of the participants, the records obtained in the intervention, and a research journal were reviewed. The study shows that the teachers carried out the phases of reflection and it tells us how the professional problem evolves, according to the characteristics and nature of the problem object and professional knowledge involved to support the definition about teaching algebra.

Resumen En este estudio se analiza la reflexión de dos futuros profesores de matemáticas, cuando identifican, definen y afrontan problemas profesionales relacionados con la enseñanza y el aprendizaje del álgebra escolar durante las prácticas de enseñanza. Con este propósito se planificó e implementó un módulo formativo en el prácticum de un programa de licenciatura en matemáticas en Colombia, bajo la teoría del aprendizaje realista, para promover la realización de un ciclo reflexivo bajo el modelo ALaCT. Siguiendo el enfoque de la investigación cualitativa, de carácter interpretativo, y usando el análisis de contenido se han examinado las producciones de los participantes, los registros obtenidos en la intervención y del diario de campo del investigador. El estudio muestra que los profesores llevaron a cabo las fases de reflexión, se informa cómo va evolucionando el problema profesional, atendiendo a las características y a la naturaleza objeto de la situación problema y al conocimiento profesional involucrado para fundamentar la definición del problema acerca de la enseñanza del álgebra.

O nitrogênio (N) é um nutriente importante para a produção de melão (Cucumis melo L.), porém existe pouca informação sobre a quantidade necessária para se obter um balanço entre o crescimento e a produtividade. Os órgãos vegetativos do melão precisam se desenvolver suficientemente para interceptor luz, acumular água e nutrients, mas também é importante alcançar uma grande relação de massa seca produtiva-vegetativa para maximizar a produção de frutos. Investigou-se a influência de quantidades de N no crescimento, na produção de matéria seca e na produtividade do melão tipo 'Pele de sapo'. Foi conduzido experimento com três anos de duração, de maio a setembro, com irrigações de 100% da evapotranspiração e 11 doses de adubação de N, no intervalo de 11 a 393 kg ha-1 em três anos. A produção de massa seca de folhas e caules aumentou com o aumento das doses de N. A matéria seca da planta toda foi afetada de maneira semelhante, enquanto a dos frutos decresceu com o aumento de N acima de 112, 93 e 95 kg ha-1, em 2005, 2006 e 2007, respectivamente. O índice de área foliar máxima (LAI) mais aulto (3.1) foi obtido com a dose de 393 kg N ha-1de N. A dose mais baixa de N reduziu a produtividade de frutos em 21%, enquanto a dose mais alta aumentou o crescimento vegetative, LAI e a duração de área foliar (LAD), mas reduziu a produtividade em 24% em relação ao tratamento N93. Aplicações excessivas de N aumentam o crescimento vegetativo às expensas do crescimento vegetativo. Para este tipo de melão, doses da ordem de 90-100 kg ha-1 de N são suficientes para crescimento adequado e produção máxima. Para obter produções próximas ao máximo, a concentração de N na folha no final do ciclo da cultura não deve ser maior que 19.5 g kg-1.

Nitrogen (N) is an important nutrient for melon (Cucumis melo L.) production. However there is scanty information about the amount necessary to maintain an appropriate balance between growth and yield. Melon vegetative organs must develop sufficiently to intercept light and accumulate water and nutrients but it is also important to obtain a large reproductive-vegetative dry weight ratio to maximize the fruit yield. We evaluated the influence of different N amounts on the growth, production of dry matter and fruit yield of a melon 'Piel de sapo' type. A three-year field experiment was carried out from May to September. Melons were subjected to an irrigation depth of 100% crop evapotranspiration and to 11 N fertilization rates, ranging 11 to 393 kg ha-1 in the three years. The dry matter production of leaves and stems increased as the N amount increased. The dry matter of the whole plant was affected similarly, while the fruit dry matter decreased as the N amount was increased above 112, 93 and 95 kg ha-1, in 2005, 2006 and 2007, respectively. The maximum Leaf Area Index (LAI), 3.1, was obtained at 393 kg ha-1 of N. The lowest N supply reduced the fruit yield by 21%, while the highest increased the vegetative growth, LAI and Leaf Area Duration (LAD), but reduced yield by 24% relative to the N93 treatment. Excessive applications of N increase vegetative growth at the expense of reproductive growth. For this melon type, rates about 90-100 kg ha-1 of N are sufficient for adequate plant growth, development and maximum production. To obtain fruit yield close to the maximum, the leaf N concentration at the end of the crop cycle should be higher than 19.5 g kg-1.