On the probable composition of ‘Jamaican stone’ aphrodisiac

Producción CientíficaA dangerous aphrodisiac, commonly known as ‘Jamaican stone’, banned by the U.S. Food and Drug Administration, has been studied by vibrational spectroscopy in order to solve the controversy on its composition. The results of the ATR-FTIR analysis revealed the presence of the a-pyrone ring, which is characteristic of bufadienolides from toad venom and bulbs of squill (Drimia maritima (L.) Stearn). This conclusion was reached after a comparative study with the spectra for phytochemicals derived from gambir and cat’s claw, two Uncaria species also preconized as aphrodisiacs and deemed as possible constituents of the ‘stone’. Owing to their physiologic similarities to digoxin, bufadienolides have been shown to produce a toxic profile similar to that of digoxin, although the lack one of the side chains found on digoxin should allow the use of hemodialysis to treat ‘Jamaican stone’ overdose

UAV Detection of sinapis arvensis infestation in alfalfa plots using simple vegetation indices from conventional digital cameras

Producción CientíficaUnmanned Aerial Vehicles (UAVs) offer excellent survey capabilities at low cost to provide farmers with information about the type and distribution of weeds in their fields. In this study, the problem of detecting the infestation of a typical weed (charlock mustard) in an alfalfa crop has been addressed using conventional digital cameras installed on a lightweight UAV to compare RGB-based indices with the widely used Normalized Difference Vegetation Index (NDVI) index. The simple (R−B)/(R+B) and (R−B)/(R+B+G) vegetation indices allowed one to easily discern the yellow weed from the green crop. Moreover, they avoided the potential confusion of weeds with soil observed for the NDVI index. The small overestimation detected in the weed identification when the RGB indices were used could be easily reduced by using them in conjunction with NDVI. The proposed methodology may be used in the generation of weed cover maps for alfalfa, which may then be translated into site-specific herbicide treatment maps.Unión Europea (project LIFE11 ENV/ES/000535

Assessment of RGB vegetation indices to estimate chlorophyll content in sugar beet leaves in the final cultivation stage

Estimation of chlorophyll content with portable meters is an easy way to quantify crop nitrogen status in sugar beet leaves. In this work, an alternative for chlorophyll content estimation using RGB-only vegetation indices has been explored. In a first step, pictures of spring-sown ‘Fernanda KWS’ variety sugar beet leaves taken with a commercial camera were used to calculate 25 RGB indices reported in the literature and to obtain 9 new indices through principal component analysis (PCA) and stepwise linear regression (SLR) techniques. The performance of the 34 indices was examined in order to evaluate their ability to estimate chlorophyll content and chlorophyll degradation in the leaves under different natural light conditions along 4 days of the canopy senescence period. Two of the new proposed RGB indices were found to improve the already good performance of the indices reported in the literature, particularly for leaves featuring low chlorophyll contents. The 4 best indices were finally tested in field conditions, using unmanned aerial vehicle (UAV)-taken photographs of a sugar beet plot, finding a reasonably good agreement with chlorophyll-meter data for all indices, in particular for I2 and (R−B)/(R+G+B). Consequently, the suggested RGB indices may hold promise for inexpensive chlorophyll estimation in sugar beet leaves during the harvest time, although a direct relationship with nitrogen status still needs to be validated

Predicción de la dinámica del carbono orgánico en suelos agrícolas del Cerrato Palentino (España) aplicando el modelo RothC

La gestión de los suelos agrícolas tiene un gran potencial para el secuestro de carbono, la reducción de las emisiones de gases de efecto invernadero y la consecución de una agricultura sostenible. Para predecir la acumulación de materia orgánica en suelos agrícolas del Cerrato Palentino (Palencia, España) se ha utilizado el modelo RothC, un método para simular a escala regional los cambios del carbono orgánico del suelo (COS) en sistemas agrícolas y forestales utilizando datos de clima y suelo. Con datos estimados de la materia orgánica inerte y la entrada mensual de vegetación o de residuos de la planta se han determinado los porcentajes de carbono inicial, carbono orgánico total anual y error frente al carbono orgánico experimental. El incremento de los contenidos de carbono orgánico en el periodo 2012-2013 ha oscilado entre el 4,9 y el 22.5%, según parcela. Las predicciones de acumulación de carbono para 100 años han sido estimadas en torno al 70% para 4 de las cinco parcelas estudiadas y del 115% para la quinta. Esta información representa una herramienta útil para la planificación futura, en nuestra área geográfica, del uso de la tierra y su gestión en relación con la reducción de las emisiones de CO