A Química na agricultura: perspectivas para o desenvolvimento de tecnologias sustentáveis

Food production and preservation of the environment are among the challenges faced by contemporary society. In Brazil, as in most parts of the world, the possibility of increasing the agricultural area is limited by several factors. Thus, an increase in productivity through the application of innovative technologies is regarded as the best solution to overcome such a problem. For long, chemistry has contributed to agricultural innovations such as synthetic pesticides for pest management. However, due to the well-known adverse effects of these compounds, new "greener" strategies are being explored. Research in chemical ecology, in combination with other emerging sciences, is leading to the development of new technologies such as plant-based pesticides (biopesticides); synthetic pheromones and plant volatile organic compounds, both of them to manipulate insect behavior; chemical elicitors to boost plant resistance; and genetic engineering of plant varieties. In these, chemistry plays an important role in the identification and synthesis of functional compounds. These techniques may be incorporated in integrated pest management programs and may contribute to a sustainable agriculture in the future.

Interactions of onion (Allium cepa) and yellow wax bean (Phaseolus vulgaris) in monoculture and intercropping with weeds, Chenopodium album and Amaranthus hybridus

Intercropping systems are seen as advantageous as they can provide higher crop yield and diversity along with fewer issues related to pests and weeds than monocultures. However, plant interactions in intercropped crop species and between crops and weeds in these systems are still not well understood. The main objective of this study was to investigate interactions between onion (Allium cepa) and yellow wax bean (Phaseolus vulgaris) in monocultures and intercropping with and without the presence of a weed species, either Chenopodium album or Amaranthus hybridus. Another objective of this study was to compare morphological traits of C. album from two different populations (conventional vs. organic farms). Using a factorial randomized block design, both crop species were planted either in monoculture or intercropped with or without the presence of one of the two weeds. The results showed that intercropping onion with yellow wax bean increased the growth of onion but decreased the growth of yellow wax bean when compared to monocultures. The relative yield total (RYT) value was 1.3. Individual aboveground dry weight of both weed species under intercropping was reduced about 5 times when compared to the control. The poor growth of weeds in intercropping might suggest that crop diversification can help resist weed infestations. A common garden experiment indicated that C. album plants from the conventional farm had larger leaf area and were taller than those from the organic farm. This might be associated with specific evolutionary adaptation of weeds to different farming practices. These findings contribute to the fundamental knowledge of crop-crop interactions, crop-weed competition and adaptation of weeds to various conditions. They provide insights for the management of diversified cropping systems and integrated weed management as practices in sustainable agriculture.

Effects of different tillage treatments on labile soil organic matter pools and stabilization processes

An improved understanding of soil organic carbon (Corg) dynamics in interaction with the mechanisms of soil structure formation is important in terms of sustainable agriculture and reduction of environmental costs of agricultural ecosystems. However, information on physical and chemical processes influencing formation and stabilization of water stable aggregates in association with Corg sequestration is scarce. Long term soil experiments are important in evaluating open questions about management induced effects on soil Corg dynamics in interaction with soil structure formation. The objectives of the present thesis were: (i) to determine the long term impacts of different tillage treatments on the interaction between macro aggregation (>250 µm) and light fraction (LF) distribution and on C sequestration in plots differing in soil texture and climatic conditions. (ii) to determine the impact of different tillage treatments on temporal changes in the size distribution of water stable aggregates and on macro aggregate turnover. (iii) to evaluate the macro aggregate rebuilding in soils with varying initial Corg contents, organic matter (OM) amendments and clay contents in a short term incubation experiment. Soil samples were taken in 0-5 cm, 5-25 cm and 25-40 cm depth from up to four commercially used fields located in arable loess regions of eastern and southern Germany after 18-25 years of different tillage treatments with almost identical experimental setups per site. At each site, one large field with spatially homogenous soil properties was divided into three plots. One of the following three tillage treatments was carried in each plot: (i) Conventional tillage (CT) with annual mouldboard ploughing to 25-30 cm (ii) mulch tillage (MT) with a cultivator or disc harrow 10-15 cm deep, and (iii) no tillage (NT) with direct drilling. The crop rotation at each site consisted of sugar beet (Beta vulgaris L.) - winter wheat (Triticum aestivum L.) - winter wheat. Crop residues were left on the field and crop management was carried out following the regional standards of agricultural practice. To investigate the above mentioned research objectives, three experiments were conducted: Experiment (i) was performed with soils sampled from four sites in April 2010 (wheat stand). Experiment (ii) was conducted with soils sampled from three sites in April 2010, September 2011 (after harvest or sugar beet stand), November 2011 (after tillage) and April 2012 (bare soil or wheat stand). An incubation study (experiment (iii)) was performed with soil sampled from one site in April 2010. Based on the aforementioned research objectives and experiments the main findings were: (i) Consistent results were found between the four long term tillage fields, varying in texture and climatic conditions. Correlation analysis of the yields of macro aggregate against the yields of free LF ( ≤1.8 g cm-3) and occluded LF, respectively, suggested that the effective litter translocation in higher soil depths and higher litter input under CT and MT compensated in the long term the higher physical impact by tillage equipment than under NT. The Corg stocks (kg Corg m−2) in 522 kg soil, based on the equivalent soil mass approach (CT: 0–40 cm, MT: 0–38 cm, NT: 0–36 cm) increased in the order CT (5.2) = NT (5.2) < MT (5.7). Significantly (p ≤ 0.05) highest Corg stocks under MT were probably a result of high crop yields in combination with reduced physical tillage impact and effective litter incorporation, resulting in a Corg sequestration rate of 31 g C-2 m-2 yr-1. (ii) Significantly higher yields of macro aggregates (g kg-2 soil) under NT (732-777) and MT (680-726) than under CT (542-631) were generally restricted to the 0-5 cm sampling depth for all sampling dates. Temporal changes on aggregate size distribution were only small and no tillage induced net effect was detectable. Thus, we assume that the physical impact by tillage equipment was only small or the impact was compensated by a higher soil mixing and effective litter translocation into higher soil depths under CT, which probably resulted in a high re aggregation. (iii) The short term incubation study showed that macro aggregate yields (g kg-2 soil) were higher after 28 days in soils receiving OM (121.4-363.0) than in the control soils (22.0-52.0), accompanied by higher contents of microbial biomass carbon and ergosterol. Highest soil respiration rates after OM amendments within the first three days of incubation indicated that macro aggregate formation is a fast process. Most of the rebuilt macro aggregates were formed within the first seven days of incubation (42-75%). Nevertheless, it was ongoing throughout the entire 28 days of incubation, which was indicated by higher soil respiration rates at the end of the incubation period in OM amended soils than in the control soils. At the same time, decreasing carbon contents within macro aggregates over time indicated that newly occluded OM within the rebuilt macro aggregates served as Corg source for microbial biomass. The different clay contents played only minor role in macro aggregate formation under the particular conditions of the incubation study. Overall, no net changes on macro aggregation were identified in the short term. Furthermore, no indications for an effective Corg sequestration on the long term under NT in comparison to CT were found. The interaction of soil disturbance, litter distribution and the fast re aggregation suggested that a distinct steady state per tillage treatment in terms of soil aggregation was established. However, continuous application of MT with a combination of reduced physical tillage impact and effective litter incorporation may offer some potential in improving the soil structure and may therefore prevent incorporated LF from rapid decomposition and result in a higher C sequestration on the long term.

The role of organic farming for food security: local nexus with a global view

A convergence of factors has made food security one of the most important global issues. It has been the core concept of the Milan Expo 2015, whose title, Feeding the Planet, Energy for Life, embodied the challenge to provide the world’s growing population with a sustainable, secure supply of safe, nutritious, and affordable high-quality food using less land with lower inputs. Meeting the food security agenda using current agricultural production techniques cannot be achieved without serious degradation to the environment, including soil degradation, loss of biodiversity and climate change. Organic farming is seen as a solution to the challenge of sustainable food production, as it provides more nutritious food, with less or no pesticide residues and lower use of inputs. A limit of organic farming is its restricted capability of producing food compared to conventional agriculture, thus being an inefficient approach to food production and to food security. The authors maintain, on the basis of a scientific literature review, that organic soils tend to retain the physical, chemical and biological properties over the long term, while maintaining stable levels of productivity and thereby ensuring long-term food production and safety. Furthermore, the productivity gap of organic crops may be worked out by further investment in research and in particular into diversification techniques. Moreover, strong scientific evidence indicates that organic agricultural systems deliver greater ecosystem services and social benefits.

Alternativas productivas para el sector agrícola de Sesquilé

A partir del proyecto macro “Municipio Saludable y Polo de Desarrollo Local” se desarrolló un trabajo de campo en el Municipio de Sesquilé, centrado principalmente en el sector agrícola, en donde se identificaron ciertas características en el proceso de cultivo ejecutado por los agricultores de la zona. Dichas características dejan ver que se está subutilizando la capacidad de cultivos, así como la necesidad de cambio y/o diversificación de los productos cosechados, mostrándose esto último como una gran oportunidad para el crecimiento del sector y por ende una nueva forma de generación de empleos. Es importante resaltar que el sector tiene una gran capacidad para el crecimiento agrícola por todos los factores naturales con los que cuenta, por lo que la identificación de nuevas alternativas de cultivos podrían tomarse como ejemplo por otras zonas para su implementación, lo que permitiría fortalecer el sector en otros municipios de Cundinamarca y convertir a Sesquilé en unos de los municipios con mayor desarrollo agrícola.

Tratado de libre comercio entre Colombia e Israel. Perspectivas generales y oportunidades para el sector agrícola colombiano

Las estrategias tendientes a la diversificación de los mercados de exportación e internacionalización de la economía por parte del gobierno colombiano y sus políticas gubernamentales han incluido la firma de una serie de Tratados de Libre Comercio, entre ellos el TLC de última generación firmado con El Estado de Israel. Estos tratados además de abordar temas tradicionales de comercio, tratan nuevos capítulos en inversiones y servicios. Así mismo se analizan las principales políticas por parte del gobierno de Israel para la competitividad en términos empresariales y sociales. Más adelante se consideran aspectos generales de la economía colombiana y se analiza la relación comercial bilateral entre el Estado de Israel y la República de Colombia para entender su comportamiento histórico y el ambiente actual. Finalmente se hace un énfasis en el sector agrícola de Israel y sus aspectos que lo han dirigido al éxito, una observación corta del sector en Colombia y luego aspectos adicionales para a facilitación del comercio con Israel. El estudio va dirigido a empresarios, compañías o entes públicos a nivel local e internacional que vean en el sector agrícola colombiano una oportunidad de desarrollo, aprovechando los beneficios de comercio y conocimiento, con el objetivo de mejorar la competitividad y productividad del sector en Colombia. Se utilizan metodologías tanto cuantitativas como cualitativas para la investigación y análisis de caso tomando la información correspondiente de fuentes verídicas e independientes para así poder reseñar y describir las oportunidades y retos del sector agrícola.

La cooperación internacional como instrumento para la construcción de paz en Colombia. Estudio de caso del proyecto “Fortalecimiento institucional para la atención a las víctimas del conflicto (FORVIC)” (2009-2014)

El presente estudio de caso pretende analizar los alcances de la cooperación internacional en materia de justicia transicional y construcción de paz tomando en consideración un proyecto de cooperación internacional emblemático denominado Fortalecimiento Institucional para la Atención a las Víctimas del Conflicto o FORVIC. Para conseguir esto, se analizarán primero los efectos generados por el Proyecto FORVIC en materia de fortalecimiento del Estado de Derecho y lucha contra la impunidad en Colombia, y a partir de los hallazgos se constituirán y se propondrán una serie de condiciones sobre las que puede pensarse la cooperación internacional como un instrumento genuino para la construcción de paz en Colombia.