A survey of 10 producers of conventional corn (Hybrids PAC 105 and Maximus) and 10 producers of transgenic corn (Pioneer Hybrid 30T17) was carried out in the municipality of Valle de San Juan in the territorial division of Tolima (Colombia), in order to analyze the differences in production costs and environmental impacts of these two agricultural technologies.  The environmental impacts were determined by calculating the field "Environmental Index Quotient" (EIQ). In the production cost analysis, a difference of 15% was found in benefit of the transgenic technology. The structure of costs of the transgenic technology was benefited by the reduced use of pesticides (insecticides and herbicides). In regards to production, the transgenic technology showed a greater yield, 5.22 ton/ha in comparison to 4.25 ton/ha the conventional technology, thus a 22% difference in yield. Finally, the EIQ calculation showed quantitative differences of 196.12 for the conventional technology (EIQ insecticides 165.14 + EIQ herbicides 30.98), while the transgenic technology was of 4.24 (EIQ insecticides 0 + EIQ herbicides 4.24). These results show a minor environmental impact when using the transgenic technology in comparison to the conventional technology, in regards to the use of insecticides and herbicides in a temporal, spatial and genotypical context analysis. :

Acacia mangium es una especie leguminosa de rápido crecimiento originaria de Australia y Asia central, cuyo uso se ha expandido por el resto del mundo debido a su ciclo corto, morfología, trabajabilidad de la madera y por su capacidad de adaptación a diferentes condiciones climáticas y edáficas. Adicionalmente, tiene potencial para el aprovechamiento de los subproductos (raleo, residuos de aserrín y lodos de papel) del cultivo y como recuperador de suelos degradados. Desde el punto de vista morfofisiológico, una característica destacada es la presencia de filodios, pecíolos ensanchados que se forman después de cuatro semanas de edad, cuando pierden las hojas verdaderas, y que realizan la actividad fotosintética que le confiere tolerancia a la planta en ambientes secos por tiempo prolongado. La asociación simbiótica con bacterias nitrificantes y hongos micorrícicos, facilita la toma de nutrientes en suelos de baja fertilidad. La floración de A. mangium se induce por genes que pueden estar relacionados con la temperatura, el fotoperíodo y la activación de señales por parte de la sacarosa y puede ocurrir en cualquier época del año, pero según su ubicación geográfica se presentan picos marcados en determinados periodos. A pesar de que en Colombia la especie ha sido cultivada desde años atrás, muchos aspectos relacionados con la respuesta de la especie a las condiciones de las regiones de cultivo, así como la calidad de los materiales genéticos introducidos, se encuentran aún sin precisar.

No abstract

The low fertility of soils of the eastern plains of Colombia makes it necessary to search for methods of improving different soil properties. Fertile soils increase yields of different crops in the region, and particularly agroforestry agroecosystems will increase wood volume. Including stabilized waste residues such as biochar will probably increase fertility. The objective of this research was to estimate the optimal volume of Acacia mangiumwood that can be obtained, when using two fertilizers applied to the soil at two levels, fitting a central composite design with star points. In the model, two levels of treatment were applied: 40 and 80 ton · ha-1of biochar and 50 and 100 g per plant ofsynthetic fertilizer 15-15-15. The optimum wood volume was found at 8566.9 cm3when the biochar was combined with 63.1 ton·ha-1and 15-15-15 at a dose of 84.4 g per plant.

One of the basic principles of experimental design is blocking, which is an important factor in the treatment of the systematic spatial variability that can be found in the edaphic properties where agricultural experiments are conducted. Blocking has a mitigating or suppressing effect on the spatial dependence in the residuals of a model, something desirable in standard linear modeling, specifically in design models. Some computer programs yield a p value associated with the blocking effect in the analysis of variance table that in many cases has been incorrectly used to discard it, and although it may improve some properties of the analysis, it may affect the independence assumption required in several models. Therefore, the present research recommends the use of the H statistic associated with the corrected blocking efficiency to show the role of blocking in modeling with the incorporation of an additional advantage rarely considered related to the suppression or mitigation of spatial dependence. With the use of the Moran index, the spatial dependence of the residuals was studied in a simple factorial design in a completely randomized and blocking field layout, which evidenced the advantages of blocking in the mitigation or suppression of the spatial dependence despite the apparently little or no importance it seems to show in the analysis of variance table.

No abstract

Biochar is a product of pyrolysis obtained from any type of biomass and can be used as a soil amendment or conditioner, improving the physical, chemical, and biological properties of the soil. Additionally, it can serve as an alternative to the application of synthetic fertilization in forest species such as Acacia mangium Willd. This research was oriented towards the determination of the economic efficiency of the use of biochar in A. mangium compared to the use of synthetic fertilizers. Production costs of wood and by-products, income and profits from forestry, economic efficiency of capital (cost-benefit ratio), labor (wood production per worker), and land (wood production ha-1) were considered. We found that the production of wood using biochar increased by 47% per unit area (ha), by 23% per unit of work (worker), and increased earnings by approximately one million Colombian pesos ha-1 compared to the use of only synthetic fertilizers.

The generation of sludge as anthropic waste is a fundamental pollution problem. However, its conversion to biochar can be an alternative to conventional fertilization for its management and use in agriculture. In this research, we evaluated the effect of the application of different doses of dry sludge (DS) and biochar of pyrolyzed sludge (PS) on the height and dry matter of a tomato (Solanum lycopersicum L.) crop and the nutrient content in the substrate. The biochar was made by rapid pyrolysis, and the substrate and the dry matter of plants were analyzed by different physical and chemical methods. An evaluation of 11 treatments was carried out in allometric measurements of plants and foliar dry matter, in three replicates with two materials (DS and PS) added to the substrate at different levels. The plant height and dry weight were evaluated using an incomplete factorial design in a completely randomized arrangement by performing statistical analysis of multivariate variance. An increase in plant height and dry weight was observed when the doses of DS and PS were increased; however, there were no statistical differences between the two materials. The amount of carbon, organic matter, and Ca concentrations in the dry leaf weight were increased with the addition of DS and PS. Likewise, the use of these materials as conditioners or amendments to agricultural soil at doses of 10-15 t ha-1 may be viable and can contribute to reducing environmental externalities through the use of these anthropic waste materials.