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.

Arrow cane (Gynerium sagittatum Aubl.) is a Poaceae associated to human development of the ancient Zenú culture present nowadays in the flat lands of Córdoba and Sucre department in the Colombian north Coast. Despite its importance, arrow cane is not cultivated in large scale and extraction from natural populations is the most common way for plant exploitation with negative environmental and economic consequences for the aboriginal communities. A research program based on biotechnology was implemented to generate information related to plant genetic diversity, plant propagation and genetic resource conservation in order to provide knowledge to contribute to implement technical crop development to minimize the impact of artisans´ activity on the environment and increase sustainability on fiber source for craftsmanship. Accessions from different zones of the Colombian territory were characterized using morphological and molecular markers founding low genetic diversity. Cultivars UC121, “Criolla”, “Criolla 1”, Costera and “Martinera” were in vitro established and micropropagation results indicated that large quantities of high quality, fully adapted, homogeneous plants can be produced from any cultivar. In vitro cultured arrow cane plants can be stored by means of slow growth or modified structures such as micro rhizomes developed in vitro.

The Sinu Valley is a subregion with the largest corn planting and production area in Colombia. Corn yield in recent years have presented a stagnation, despite having agri-ecological technologies and conditions suitable for cultivation. It is presumed that continuous soil tillage through the years has generated a high degree physical and chemical deterioration of soil characteristics. This research was carried out with the objective of diagnosing corn cultivated soil fertility based on some physicochemical properties. Sampling was carried out in 80 farms, where corn have been continuously planted, and rotated with cotton. The results indicated that from the chemical point of view, in general soils present an adequate fertility for crop development and productivity; however, some degree of deterioration on the physical characteristics was observed, and evidenced by variables such as apparent density, basic infiltration, and distribution of roots in the profile, mainly conditioned to the type of tillage that has been practiced. This has probably affected the root growth, free water and gas circulation, and nutrition of corn crops. A more detailed study on root distribution in the soil profile was recommended to propose strategies for soil recovery.

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.

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 Sinu Valley is a subregion with the largest corn planting and production area in Colombia. Corn yield in recent years have presented a stagnation, despite having agri-ecological technologies and conditions suitable for cultivation. It is presumed that continuous soil tillage through the years has generated a high degree physical and chemical deterioration of soil characteristics. This research was carried out with the objective of diagnosing corn cultivated soil fertility based on some physicochemical properties. Sampling was carried out in 80 farms, where corn have been continuously planted, and rotated with cotton. The results indicated that from the chemical point of view, in general soils present an adequate fertility for crop development and productivity; however, some degree of deterioration on the physical characteristics was observed, and evidenced by variables such as apparent density, basic infiltration, and distribution of roots in the profile, mainly conditioned to the type of tillage that has been practiced. This has probably affected the root growth, free water and gas circulation, and nutrition of corn crops. A more detailed study on root distribution in the soil profile was recommended to propose strategies for soil recovery.

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.

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.

El cultivo de cítricos en Colombia, desde el 2016, está en riesgo por la enfermedad huanglongbing – HLB. El municipio de Ponedera (Atlántico) es uno de los más afectados por la enfermedad, sin embargo, existe escasa información sobre el impacto en el sistema productivo de los cítricos. Con el propósito de categorizar a los productores, identificar sus condiciones y dimensionar el impacto del HLB, a 134 agricultores se les aplicó una encuesta semiestructurada con 79 preguntas sobre aspectos socioeconómicos, ambientales y agronómicos con énfasis en el conocimiento de la enfermedad. Mediante análisis descriptivo y correspondencia múltiple se seleccionaron las variables con mayor aporte a la categorización de los productores, con la identificación de cinco grupos de acuerdo con la asistencia a capacitaciones, especies cítricas, tipo y origen del material de propagación y categoría de edad del limón común (Citrus aurantifolia Swingle), y categoría de edad y marco de siembra de la lima ácida Tahití (Citrus × latifolia Tanaka ex Q. Jiménez). Este estudio determinó que entre 2016 y 2020, más del 85% de los agricultores perdió, al menos, el 50% de los árboles debido a limitantes como: carencia de riego (67,6%), de fertilización (75,4%), de control del psílido asiático de los cítricos (76,9%) o de HLB (87,3%). Asimismo, evidenció el efecto devastador de la enfermedad HLB en el cultivo. La caracterización de los productores estableció la capacitación como una variable diferenciadora, resultado que servirá para el desarrollo de ofertas tecnológicas, extensión agrícola y formación de clústeres productivos.