ABSTRACT The thermal efficiency of naturally ventilated greenhouses is limited due to the permanent exchange of air through the vents, especially during the night hours. The objective of the work consisted in evaluating a system of inflatable air ducts that close the roof vents during the night as a strategy to reduce the energy loss during these hours. For the development of this work, we applied the computational fluid dynamics (CFD) method to a passive multi span greenhouse operating under the dominant nocturnal climatic conditions of the Bogota savannah (Colombia). The results indicated that the use of the ducts system reduces the value of the negative thermal gradient between the interior and exterior of the greenhouse. The CFD model used was validated by comparing experimental data and simulated data and by calculating goodness-of-fit parameters, finding that the numerical model predicts satisfactorily and with an adequate degree of fit the actual thermal behavior of the greenhouse evaluated.

Resumo O desempenho espacial das variáveis ambientais envolvidas na produção de rosas é um dos fatores de maior interesse atual no setor ornamental colombiano. O objetivo deste trabalho foi a avaliação de uma estufa passiva através de uma abordagem experimental que incluiu a captura e registro de dados através de uma rede de 40 sensores uniformemente distribuídos dentro da estufa. O processamento de dados foi feito através da aplicação de técnicas geoestatísticas que permitiram a obtenção de gráficos de contorno para 5 níveis de intensidade de radiação. Os resultados da análise exploratória mostraram que o desempenho da temperatura, umidade relativa e déficit de pressão de vapor não são os mais adequados para a produção de rosas, principalmente para as condições do período noturno em que a temperatura apresentou valores abaixo de 12,5 °C, a umidade relativa estava acima de 90% e o déficit de pressão de vapor estava abaixo de 0,1 kPa. Por outro lado, na análise estrutural, o modelo circular do semivariograma teórico foi o que apresentou o melhor grau de ajuste em relação aos dados experimentais, encontrando que existe uma forte dependência espacial para as variáveis estudadas. A previsão dos pontos não amostrados foi feita através do método de kriging ordinário, encontrando que existem gradientes horizontais de temperatura e umidade relativa dentro da estufa que aumentam de magnitude de acordo com o nível de radiação, atingindo valores de 6.1 °C e 30.4%.

Abstract The spatial behavior of the environmental variables involved in rose production is one of the factors of greatest current interest in the Colombian ornamental sector. The aim of this work consisted in the evaluation of a passive greenhouse through an experimental approach that included the capture and recording of data through a grid of 40 sensors homogeneously distributed inside the greenhouse. The data processing was carried out through the application of geostatistical techniques that allowed to obtain contour plots for 5 levels of radiation intensity. The results of the exploratory analysis showed that the behavior of temperature, relative humidity and vapour pressure deficit are not the most suitable for rose production, mainly for the conditions of the night period where the temperature exhibited values below 12.5 °C, the relative humidity was above 90% and the vapour pressure deficit was below 0.1 kPa. On the other hand in the structural analysis the circular model of theoretical semivariogram was the one that better degree of adjustment presented in comparison with the experimental data finding that a strong spatial dependency exists for the studied variables, the prediction of the not sampled points was made by means of the method of ordinary kriging finding that horizontal gradients of temperature and relative humidity exist inside the greenhouse that increases in magnitude according to the level of radiation arriving to reach values of 6.1 °C and 30.4%.

Resumo A produção de cravos na Colômbia, o principal exportador mundial, é realizada inteiramente em estufas agrícolas com ventilação natural. Neste tipo de estrutura, estão presentes condições microclimáticas não homogêneas, que afetam negativamente o crescimento e desenvolvimento dos cultivos, razão pela qual esta questão tem sido de grande interesse de pesquisa nos últimos anos. O objetivo foi determinar o desempenho microclimático de estufa agrícola com ventilação natural de tipo espacial utilizada na Colômbia para a produção de cravo. A abordagem experimental incluiu a coleta de dados meteorológicos no ambiente externo através de uma estação meteorológica e no interior da estufa através de uma grade de 40 sensores uniformemente distribuídos em um plano horizontal. O processamento de dados para determinar a variabilidade espacial da temperatura, umidade relativa e déficit de pressão de vapor (VPD) foi feito usando técnicas geoestatísticas e prevendo estas variáveis em pontos não amostrados através do método de Kriging comum. Os principais resultados obtidos permitiram determinar que as condições geradas dentro da estufa não são as ideais recomendadas para a produção de cravos e que, além disso, o desempenho das variáveis estudadas mostra uma distribuição heterogênea, obtendo variações espaciais no perfil horizontal avaliado para o período noturno de 0,5 °C, 9,1% e 1,5 kPa e para o período diurno de 7,2 °C, 42,6% e 1,5 kPa para a temperatura, umidade e VPD, respectivamente.

Abstract Carnation production in Colombia, the world’s main exporter, takes place entirely in naturally ventilated greenhouses. This type of structure presents non-homogeneous microclimate conditions which differentially affect crop growth and development, which is why this issue has been of great research interest in recent years. The objective was to determine the microclimatic behavior of a passive spatial-type greenhouse used in Colombia for carnation production. The experimental approach included the collection of meteorological data in the external environment through a weather station and in the inside of the greenhouse through a grid of 40 sensors uniformly distributed in a horizontal plane. Data processing to determine the spatial variability of temperature, relative humidity and vapour pressure deficit (VPD) is done by using geostatistical techniques and predicting these variables at unsampled points through the ordinary Kriging method. The main results obtained allowed us to determine that the conditions generated inside the greenhouse are not the optimal ones recommended for carnation production and that, in addition, the behavior of the variables studied shows a heterogeneous distribution, obtaining spatial variations in the horizontal profile evaluated for the night period of 0.5 °C, 9.1% and 1.5 kPa and for the daytime period of 7.2 °C, 42.6% and 1.5 kPa for temperature, humidity and VPD respectively.

RESUMEN Los modelos de cultivo potenciales simulan el crecimiento de la planta bajo condiciones biofísicas no limitantes, sin más que el clima al que están expuestas las plantas. Estos modelos pueden no representar adecuadamente el rendimiento del cultivo si no se adaptan a las condiciones locales. Las particularidades de los sistemas colombianos de tomate (invernadero y campo abierto) demandan la recalibración de modelos existentes para hacer una representación más realista de esos sistemas. Por lo tanto, en el presente trabajo se propone un modelo de cultivo calibrado localmente considerando ambos sistemas de producción. Para ello, se realizaron cuatro experimentos de calibración en finca, dos en condiciones de invernadero con temperaturas promedio de 17,4 y 17,9°C en Santa Sofía (Boyacá) y dos en campo abierto en Páramo y San Gil (Santander), con temperaturas promedio de 20,6 y 24,0°C, respectivamente. Los cultivos fueron manejados comercialmente según las prácticas locales. Los datos de las plantas se recolectaron mediante muestreos destructivos realizados cada dos semanas, mientras que los datos climáticos se recolectaron durante todo el ciclo de cultivo. La calibración independiente de las fracciones de materia seca asignadas a los órganos de las plantas en función del tiempo térmico dio como resultado un rendimiento aceptable del modelo. La calibración del modelo en condiciones comerciales dio una mejor representación de los sistemas locales, pero a expensas de la precisión, ya que los experimentos en las fincas no pueden ser controlados como los realizados en instalaciones de investigación.

ABSTRACT Potential crop models simulate the plant growth under non-limiting biophysical conditions with no other factor than the climate to which the plants are exposed to. These models may fail to adequately represent the crop performance if they are not adapted to the local conditions. The particularities of Colombian tomato systems (greenhouse and open field) demand the recalibration of existing models to make a more realistic representation of those systems. Therefore, a locally calibrated crop model was proposed considering both production systems. To this purpose, four on-farm calibration experiments were carried out, two under greenhouse conditions with average temperatures of 17.4 and 17.9°C in Santa Sofía (Boyacá) and two under open field conditions in Páramo and San Gil (Santander), with average temperatures of 20.6 and 24.0°C, respectively. The crops were commercially managed according to the local practices. Plant data was collected through destructive measurements carried out on a fortnightly basis, while climate data were collected for the entire crop growth cycle. Independent calibration of the dry matter fractions allocated at the plant organs in function of thermal time resulted in an acceptable model performance. The calibration of the model under commercial conditions gave a better representation of the local systems but at the expense of accuracy since on-farm experiments cannot be controlled as those performed in research facilities.

Los cultivos de tomate bajo invernadero utilizan estructuras que protegen los cultivos de condiciones ambientales extremas, sin embargo el clima dentro de los invernaderos colombianos, a menudo, no es el óptimo y los cultivos son susceptibles al ataque de enfermedades fungosas. El uso de modelos de simulación que alertan de manera temprana el ataque de enfermedades ha ayudado a racionalizar el uso de plaguicidas químicos aumentando su eficiencia al ser asperjados en los momentos críticos de ataque de la enfermedad. El objetivo del presente trabajo fue calibrar el modelo de balance energético para una superficie húmeda (SWEB) para estimar la duración de la presencia de agua libre sobre el follaje (LWD), en el tomate bajo invernadero de la provincia del Alto Ricaurte (Boyacá). Para su calibración, las simulaciones fueron contrastadas con registros provenientes de sensores dieléctricos de humedad de hoja. El modelo representó adecuadamente el fenómeno de agua libre sobre el follaje en dos invernaderos de Santa Sofía y Sutamarchán. El modelo simuló un promedio de ocurrencia de LWD de 9.9 y 12.1 horas día-1 en los invernaderos de Santa Sofía y Sutamarchán, respectivamente. Las simulaciones para estos dos invernaderos indicaron comportamientos variables, donde la diferencia promedio diaria de número de horas con agua libre sobre el follaje para Santa Sofía fue de 0.8 horas mientras que para Sutamarchán la diferencia alcanzó las 4 horas en promedio. El índice de estimaciones correctas indicó que el modelo tuvo la capacidad de predecir correctamente el 92 y el 72% de las horas con la presencia o ausencia de LWD en Santa Sofía y Sutamarchán, respectivamente. El modelo SWEB es una herramienta útil de alerta temprana para el ataque de enfermedades fungosas en tomate bajo invernadero. Sin embargo, las deficiencias de los invernaderos utilizados para la producción indican un alto grado de susceptibilidad de los cultivos al ataque de estos patógenos.

Greenhouse tomato production uses structures that protect crops from extreme environmental conditions; however, the climate inside Colombian greenhouses is often not optimal and crops are susceptible to attack by fungal diseases. The use of simulation models for early warnings of attack by diseases have helped to rationalize the use of chemical pesticides by increasing their efficiency when sprayed at critical times of disease onset. The aim of this study was to calibrate the surface wetness energy balance (SWEB) model to estimate the leaf wetness duration (LWD) for greenhouse tomatoes in the Alto Ricaurte province (Boyaca). For the validation, the performances of the SWEB model were evaluated by comparing a simulated LWD with records from dielectric leaf wetness sensors. The model adequately represented the phenomenon of free water on the leaves for plants in two greenhouses of Santa Sofia and Sutamarchan. The model simulated an average LWD of 9.9 and 12.1 hours day-1 in Santa Sofia and Sutamarchan, respectively. However, the simulations for the two greenhouses indicated different behaviors, with average differences between the observed and simulated daily number of hours with free water of 0.8 hours for Santa Sofia, while, for Sutamarchan, the difference reached 4 hours. The fraction of correct estimates index indicated the model had the ability to correctly predict 92 and 72% of the hours with a presence or absence of LWD in Santa Sofia and Sutamarchan, respectively. The SWEB model is a useful tool for early warnings for the attack of fungal diseases in greenhouse tomatoes. However, due to the shortcomings of the greenhouse structures used for production, the crops are highly susceptible to attack from these pathogens.

Este trabalho apresenta os resultados da validação de um método simples, rápido e de baixo custo de preparação de amostras para a determinação de resíduos de pesticidas em solo por cromatografia líquida ultrarrápida acoplada a espectrometria de massas com ionização por electrospray. O método se baseia na extração com acetonitrila assistida por ultrassom, centrifugação e evaporação, sem etapa de purificação adicional. As recuperações foram avaliadas a partir de dois tipos de solo, apresentando resultados na faixa de 70-110%, com desvio padrão relativo menor que 20%. Os coeficientes de correlação para as curvas analíticas de calibração foram maiores do que 0,99. Os resíduos de pesticidas foram detectados em solos no intervalo de 1-62 ng g-1, dependendo do composto. A incerteza do método foi estimada a partir de diferentes experimentos de adição e recuperação e materiais certificados. O processo de extração foi identificado como a principal fonte de incerteza e as incertezas expandidas para cada pesticida, utilizando-se um fator de cobertura de 2, situaram-se entre 8,4 e 33%. O método proposto foi aplicado para a determinação de pesticidas em amostras reais.

This work presents the validation results of a simple, fast and low-cost sample preparation method for the determination of pesticide residues in soil by ultrafast liquid chromatography coupled to electrospray ionization mass spectrometry. The method uses acetonitrile ultrasound-assisted extraction, centrifugation and evaporation step, without further cleanup. Recovery studies were performed for two soil blanks, presenting results in the range of 70-110% with relative standard deviation lower than 20%. The correlation coefficients for analytical calibration curves were higher than 0.99. Pesticide residues were detected in soils in the range of 1-62 ng g-1, depending on the compound. The uncertainty of the method was estimated from different addition-recovery experiments and calculations from certificates. The extraction process was identified as the main source of uncertainty, and the expanded uncertainties for each pesticide, using a coverage factor of two, were between 8.4 and 33%. The proposed method was applied to the determination of pesticides in real samples.

En Colombia la optimización del diseño de los invernaderos no ha tenido mayor relevancia y en consecuencia las estructuras existentes presentan deficiencias en su ventilación, generando así microclimas inadecuados para los cultivos. A nivel productivo, el manejo climático es deficiente, olvidando que el microclima interior es función de características de diseño del invernadero. El objetivo del trabajo fue el de estudiar la eficiencia de variantes introducidas a la ventilación de un invernadero multi-túnel mediante simulaciones numéricas empleando el método de dinámica de fluidos computacional. A partir del modelo comercial se diseñaron dos variantes experimentales realizando cambios estructurales y de orientación de las ventanas cenitales fijas. Los tres diseños de invernaderos fueron sometidos a simulaciones por computador con el propósito de maximizar los índices de renovación de aire, mejorar el movimiento del flujo de aire en toda la estructura y buscar una homogeneidad en el microclima. El diseño más adecuado fue aquel que presentó un índice de renovación de aire suficiente para garantizar un adecuado control de la temperatura y la humedad a través de la ventilación natural. Este diseño generó además el microclima más homogéneo dentro de la zona de cultivo

In Colombia, greenhouse design optimization has not been a relevant topic and, as a consequence, the ventilation systems of current structures are not optimal, generating inadequate microclimates for the development of horticultural species. At the production level, management of the greenhouse climate is deficient, and this factor is not taken into account as a function of characteristics dependent on greenhouse design that cannot be modified during its lifespan. The aim of the present work was to study the efficiency of modifications applied to the ventilation system of a commercial greenhouse available on the Colombian market. This was accomplished by using numerical simulations through the application of the computational fluid dynamics method. Based on the commercial greenhouse design, two modified models were designed by applying structural modifications and changing the orientation of the fixed open ridges. Simulations with the three greenhouse models were carried out in order to maximize the air renovation rates and improve air movement within the entire greenhouse, striving for the highest degree of climate homogenization. The best greenhouse design was the one with the highest air renovation index, high enough to ensure adequate control of temperature and humidity extremes through natural ventilation. Additionally, this design generated the most homogenous microclimate within the cultivation zone

Actualmente en Colombia se siembran aproximadamente 3.390 ha de tomate dentro de invernaderos caracterizados por un bajo nivel de control de clima. En zonas donde las bajas temperaturas nocturnas limitan la producción de tomate, el uso de pantallas térmicas puede ser una alternativa orientada a mejorar las condiciones de producción del cultivo. El trabajo se realizó en dos invernaderos ubicados en Chía y Susa (Cundinamarca). Cada invernadero fue dividido en dos secciones, una de las cuales se cubrió con una pantalla aluminizada. En ambas localidades las pantallas se extendieron sobre el área de cultivo durante las horas de la noche (5:00 pm - 6:00 am). En cada sección de invernadero y durante un ciclo de cultivo se registraron la temperatura (T, °C) y la humedad relativa (HR, %) de forma permanente al igual que las condiciones climáticas externas. El efecto de las pantallas térmicas en campo sobre la producción de tomate se comparó con los resultados de simulaciones realizadas por el modelo potencial de crecimiento del tomate "Tomgro". En ambas localidades la sección con pantalla registró las temperaturas más altas durante la noche. En Chía, el aumento de temperatura nocturna por efecto de la pantalla fue de 1,5±0,1°C mientras que en Susa el aumento fue de 1,1±0,1°C. Los registros de producción indicaron incrementos del 6,6% (Chía) y 3,3% (Susa) con el uso de la pantalla. Los resultados del Tomgro sugieren la posibilidad de alcanzar incrementos en la producción potencial de hasta 15,7 y 13,6% debida al uso de pantallas en las localidades Chía y Susa, respectivamente. El uso de pantallas térmicas en las horas de la noche logra retener el calor dentro del invernadero, lo cual se ve reflejado en un incremento de la producción

Currently, Colombia has 3,390 ha cultivated with tomato under greenhouse conditions characterized by their low level of climate control. In areas where low night temperatures limit tomato production, we evaluated the effect of aluminized screens on the production of the crop. This work was conducted in two greenhouses planted with tomato in Susa and Chía (Cundinamarca). Each greenhouse was divided in two sections, one half covered with the screen and the other not. Screens at both locations were closed between 5:00 pm and 6:00 am. Inside each greenhouse section, temperature (T, °C) and relative humidity (HR, %) were recorded during the production cycle, as well as the external climate conditions. The effect of aluminized screens on tomato production was compared against the simulation output of the tomato potential growth model "Tomgro". In both locations the covered section with the screen yielded the highest temperatures during the night. At Chia, the night temperature increase due to the screen effect was 1.5±0.10°C, while in Susa the temperature increase was 1.1±0.1°C. Recorded yield under the screened sections showed increments of 6.6% (Chia) and 3.3% (Susa). Simulation results suggest that yield increments of about 15.7 and 13.6% are achievable under potential conditions in Chia and Susa, respectively. The use of thermal screens during night hours helps to retain heat, which in turn is reflected in production increments