Jorge Arnaldo Orozco-Vidal

Localization of local soil classes in an arid region of Mexico, using satellite imagery

A map of local soil classes (LSCs) was used to make digital maps of soil classes using computer-assisted cartography. The objectives were to establish classes of the local soils of an arid locality; to determine their physical and chemical characteristics; to relate the content of clay (Cl), organic matter (OM) and electrical conductivity (EC) to the levels of reflectance from the classes of soil; and to obtain a digital map of classes of local soils using a supervised classification of the image and verify its precision. The map of LSCs was used as basis for generating information about the physical and chemical characteristics of soils. The information was related to digital levels of a Landsat 7 Enhanced Thematic Mapper Plus (ETM+) image, and a supervised classification was performed. The precision of the digital maps was verified. The results show that a map of LSCs can be used as basis for generating digital maps.

Fuentes de nitrógeno en el crecimiento y producción de biomasa en maíz

El objetivo de esta investigacion fue determinar la dinamica de crecimiento y la eficiencia de produccion y distribucion de biomasa en un hibrido de maiz forrajero (HT9019Y) fertilizado con dos fuentes de nitrogeno (tradicional y de lenta liberacion), a partir de muestreos vegetativos y reproductivos efectuados en diferentes etapas fenologicas. La siembra se realizo en el ciclo primavera-verano 2014. Las fuentes de nitrogeno se distribuyeron en un diseno experimental de bloques al azar con ocho repeticiones. En cuatro fechas diferentes (20, 40, 60 y 80 dds) se realizaron muestreos donde se colectaron dos plantas por unidad experimental para obtener datos de area foliar, peso seco total y peso seco de organos vegetativos y fructiferos. Indices del crecimiento como la tasa de crecimiento del cultivo (TCC), tasa de asimilacion neta (TAN), indice de area foliar (IAF), relacion de area foliar (RAF), area foliar especifica (AFE) y relacion de peso foliar (RPF) fueron estimados con los datos obtenidos. Los resultados muestran que existio diferencia estadistica significativa en los indicadores de la magnitud del aparato fotosintetico (RAF y AFE) entre las fuentes de nitrogeno estudiadas, obteniendo los mejores resultados con la fuente de nitrogeno de lenta liberacion (Ecology Nitrogen Technology). Asi como tambien para la tasa de produccion con diferencias de 262.4 g m-2 al utilizar la fuente de nitrogeno Entec, generando en sus ultimas fases de crecimiento una mayor velocidad de sus procesos metabolicos y una mayor eficiencia fotosintetica al obtener una TCC de 142.00 y una TAN de 48.75 g m-2 d-1, respectivamente

Pumice for Efficient Water Use in Greenhouse Tomato Production

The worldwide water demand is increasing (Yokwe, 2009). Although the type, magnitude and scope of the problems for water can vary from country to country (Biswas, 2010), the sector considered as the biggest user of water is agricultural (Hamdy et al., 2003). Therefore, water conservation through the efficient use of this resource in agriculture, is one of the most important firsts in the world (Diaz et al., 2004), especially in arid and semiarid regions (Forouzani & Karami, 2011). Different alternatives have been proposed to achieve sustainable water use in agriculture (Abad & Noguera, 2000; Diaz et al., 2004; Fuentes & Garcia, 1999). The food production in greenhouses is one of the alternatives to ensure efficient use of water (Abad & Noguera, 2000; Cadahia, 2000; Tahi et al., 2007). Greenhouses are structures that have a plastic cover, easy climate control systems, irrigation equipment and automated fertilization, elements that are used to increase productivity of horticultural and ornamentals crops (Cadahia, 2000; Cantliffe et al., 2003). In this production system, soil is often not used; instead other materials or mixtures of materials, known as substrate are used (Abad et al., 1996). Substrates are mineral or organic materials, used for an anchor for plants and as a container of water they need (Dalton et al., 2006). To this end, substrates must have high storage capacity of water and keep it available to plants (Bender, 2008). However, these materials are often not native to the region where the activities of greenhouse production are taking place, which increases their cost (Cadahia, 2000). Therefore, natural materials and wastes are in a given region, have an important role in agricultural activities (Yaalon & Arnold, 2000) and in the preparation of substrates. One of the naturally occurring mineral substrates, readily available and inexpensive is the sand, the material found in all environments (Moinereau et al., 1987). However, its moisture retention capacity is low, which implies the constant application of water to keep the plants grown on this substrate. Some industrial wastes such as rice husks, coconut fiber, coffee husks, rockwool, phenolic foams (Calderon & Cevallos, 2003), compost (Lopez & Salinas, 2004) and pumice (Segura et al., 2008), also used as substrates.