Editorial Temas Agrarios Volume 26(2) of 2021 | Editorial Temas Agrarios Volumen 26(2) de 2021

1st International and 2nd National Symposium of Agronomic Sciences: The rebirth of the scientific discussion space for the Colombian Agro. | 1 Simposio Intenacional y 2 Nacional de Ciencias Agronómicas: El renacer del espacio de discusión científica para el Agro colombiano.

1 Simposio Intenacional y 2 Nacional de Ciencias Agronómicas: El renacer del espacio de discusión científica para el Agro colombiano.

The objective of this work was to analyze the behavior of the price of the smoke in the five main markets: Barranquilla, Cartagena, Montería, Sincelejo and Valledupar of the Caribbean Region of Colombia. The data used were from the DANE Price Information System in weekly periods during the years 2012 to 2019. With the use of cointegration techniques, the relationships between the series were identified, and causality was also determined by the Granger method. The work proved that there is integration of the markets in the price formation process. The results show the comprehensiveness of the markets and the absence of causality between the prices of the five cities without the size of the market affecting this situation. It is concluded that, even in the absence of causality between the markets, they are integrated in the long term, which shows compliance with the single price law.

To determine the viability of micrografting of Valencia orange and Tahiti Lime plants on Cleopatra mandarin rootstocks for possible use in massive plant propagation, different steps o the micrografting procedure were evaluated. Seeds of Cleopatra mandarin were established in semisolid MS (Murashige and Skoog) with, or without, GA3 to evaluate the effect on percentage and time time of germination. Plants of Valencia and Tahiti were, either, treated with 1 mg l -1 BAP or manually pruned to evaluate the effect on vegetative shoot production, and the effect of three positions of the shoot tip meristem (Topping, sided and slant) onto the decapitated surface of the rootstock on the percentage of success were evaluated. Treatments for all experiments were distributed with a complete randomized design and data for vegetative shoot production were analyzed with ANOVA and means separated with Tukey test. Results evidenced that GA3 had no effect on increasing percentage and reducing time of germination, pruning statistically increased the number of vegetative shoots in plants. Micrografting success of 28% for Valencia orange and 14% for Tahiti lime are consistent with reported studies for recovery of disease-free plants; however, to increase success level for massive plant propagation, it is recommended for further studies to consider evaluation of in vitro conditions such as increased sucrose concentration, in vitro adaptation of shoot tip meristems and auxin supply, among others.

Cañafistol (Cassia moschata Kunth) and yopo (Mimosa trianae Benth.) are important native species in the Colombian Orinoco Region, however, their behavior in a monoculture system and genetic variability are unknown. In a 7-year-old plantation located at La Libertad Research Center (Villavicencio, Meta), the phenotypic variability of 108 M. trianae trees and 52 C. moschata trees was evaluated using 37 quantitative and qualitative plant descriptors (crown, stem, leaf). Principal component analysis and multiple correspondence were used for quantitative and qualitative variables respectively, in order to reduce the dimensionality of the data, followed by cluster analysis using the WARD algorithm. C. moschata had a smaller size and a less vigorous crown, in comparison to M. trianae which stands out for its greater number of branches, crown diameter, wood volume and annual average increase of the total height and DBH. The cluster analysis allowed classifying the individuals of C. moschata and M. trianae into six and five groups retaining 99.92% and 99.58% of the original variability respectively. The variables trunk volume, crown diameter, number of branches and total height are the most important for the selection of timber trees and use in agroforestry systems. In M. trianae the number of leaflets per leaf and the size of the leaves are equally relevant variables for the selection of shade trees.

The modification of the landscape, the intense exploitation of natural resources through intensive agriculture and the advance of the agricultural frontier result in the homogenization of the landscape and alteration of soil physicochemical conditions. These soil alterations cause changes in the composition and diversity of edaphic arthropod communities that can be used as biomonitoring and diagnostic tools in local areas. The objective of the study was to evaluate the diversity of edaphic arthropods and their association to different physicochemical parameters (i.e., pH, real density, bulk density, %OC, %OM and gravimetric and volumetric humidity) in three soil uses (permanent crop, rotational crop and pasture) in the experimental farm Tunguavita Paipa - Boyacá. The plot sampling technique was used to obtain data on biological and physicochemical variables. Samples were taken in three soil uses, permanent crop, rotational crop and cattle ranch. The edaphic arthropods and physicochemical variables were determined in the soil laboratory of the Universidad Pedagógica y Tecnológica de Colombia. The highest diversity of edaphic arthropods (309 individuals) was recorded in the permanent crop plot, followed by the rotational crop plot, both with high average values of %OM (1.82 - 1.90) and %OC (1.05 - 1.10). The Oligochaeta, Diplopoda and Araneae group were the major contributors to the biological differentiation between land uses. The changes in the abundance of edaphic arthropods were related to % gravimetric humidity, %volumetric humidity, pH, %OM and %OC, while the values of real density and bulk density did not correlate to a great extent with the changes in abundance. These variations allow the differentiation of land uses in an intervention gradient.

Ornamental plants, in addition to beautifying, have medicinal, melliferous, entomological and environmental utility; however, the studies carried out in this group are not very representative. The objective was to evaluate the diversity and social perception of the ornamental flora present in suburban farms in Santiago de Cuba and its potential to generate goods and services at a community scale. Selected the farms, samplings were carried out to establish the composition and diversity of ornamental evaluating the Richness of Species, Dominance of Simpsons and General Diversity. Then interviews were applied to people related to the production or use of ornamental plants. 6 778 individuals belonging to 36 families, 52 genera and 57 species were found. The botanical composition was variable, tending to increase from one period to the next, being the families Amaryllidaceae, Asteraceae, Araceae and Euphorbiaceae the ones that contributed the most. The richness varied between 1 and 24 species, the highest being reported in the farm La Esperanza for both periods. The dominance values were within the established range, although de trend was to increase with the arrival of the rain, influenced by 26.31% of the species that were the most abundant. The general diversity varied between 0 and 2.7720 decreasing with the change of period; however, in Tres Palmas, La Juliana and La Sorpresa farms, values were not obtained within the established range. There is good social perception about this group of plants and improving their availability was recognized as a social need.

El estudio se realizó en el año 2021 con el objetivo de estimar el rendimiento agrícola de la caña de azúcar mediante el Índice de Diferencia Normalizado de Vegetación en la Empresa Azucarera “Cristino Naranjo”, ubicado en el municipio Cacocum provincia Holguín, Cuba. Se trazaron 32 puntos aleatorios de muestreo en los diferentes meses en los que se escogieron las imágenes pertenecientes al satélite Landsat 8 OLI/TIRS proyectadas en el sistema WGS 84 UTM Zona 18 Norte en la cuadrícula 011/046. En el software QGIS “A Coruña” versión 3.10 se realizó la corrección radiométrica de cada imagen satelital y el esquema de muestreo, mientras que en ArcGIS 10.5 se realizó la extracción de los valores de cada punto luego del cálculo del NDVI Para el procesamiento estadístico se utilizó el software Stargraphics Plus 5.0; en el cual se realizó el análisis de regresión lineal entre los valores obtenidos del NDVI en cada punto de muestreo y los valores del rendimiento real ofrecidos por especialistas del área de análisis del Central que se corresponden a las fechas de las imágenes utilizadas. La determinación del índice vegetativo NDVI muestra valores desde 0 hasta 0,5 se presenta una escasa vegetación en el área de estudio. El coeficiente de determinación indica que el modelo explica el 97,8598 de la variabilidad del rendimiento en el cultivo de la caña de azúcar lo cual puede ser utilizado como modelos matemáticos para la estimación del rendimiento de este cultivo bajo las condiciones edafoclimáticas del sitio de estudio.

El presente estudio se llevó a cabo con el objeto de monitorear el crecimiento foliar, la emisión de hojas y el comportamiento diario de la fotosíntesis en plantas de fique cv Ceniza. Para lo anterior, en un cultivo comercial se seleccionaron plantas de fique a las cuales se les realizó un monitoreo semanal para determinar las ganancias en número, longitud, ancho y grosor de las hojas, durante un período de 154 días. En dos oportunidades durante el periodo experimental, se realizó también un monitoreo cada hora a las tasas de intercambio gaseoso durante los periodos de luz y oscuridad. Los resultados de crecimiento permitieron estimar un filocrono promedio de 8,65 días. El monitoreo a las tasas de intercambio gaseoso indicaron una baja conductancia estomática durante el período de luz. Sin embargo, a partir de las 15:30 h, la conductancia estomática se incrementó sustancialmente, manteniéndose a niveles máximos durante todo el período de oscuridad, para posteriormente decrecer a partir de las 09:30 h, del siguiente periodo de luz. Se encontró una alta correlación de la conductancia estomática con el déficit de presión de vapor y la temperatura foliar. Las máximas tasas de fijación de CO2 detectadas variaron entre 12,2 y 14,5 µmol m-2 s-1, las cuales se registraron entre las 19:19 y las 19:26 h, durante el período de oscuridad. Estos resultados corroboran el metabolismo CAM de las plantas de fique cv Ceniza.