25 research outputs found
Broad-scale cruciferous weed patch classification in winter wheat using QuickBird imagery for in-season site-specific control
Las agrociudades mediterraneas como forma de dominio cultural: Los casos de Sicilia y Andalucia
Neither town nor country: The importance of transitional space in the organisation of Andalusia's Habitat
Respuesta fisiol贸gica de un cultivo de mel贸n (Cucumis Melo L.) a distintas dosis de riego
En este trabajo se presentan los resultados de resistencia estom谩tica (Rs) obtenidos en diferentes momentos del d铆a y al alba a lo largo del desarrollo del cultivo, con el fin de valorar la respuesta fisiol贸gica de las hojas de mel贸n sometido a distintas dosis de riego, as铆 como su relaci贸n con la evoluci贸n del 铆ndice de 谩rea foliar (LAI) y el rendimiento. Los niveles h铆dricos se determ铆naron en funci贸n de las necesidades de riego calculadas (NRc) a partir de la evapotranspiraci贸n del cultivo, ensay谩ndose cuatro tratamientos correspondientes a 1,25 NRc ; 1,00 NRc ; 0,75 NRc y 0,50 NRc. Los estomas del haz y del env茅s de la hoja no respondieron de forma similar a las distintas condiciones del medio, obteni茅ndose valores de Rs superiores en el haz. La dosis de riego no afect贸 de forma significativa a este par谩metro en las distintas fechas de medida al alba. Tampoco hubo diferencias entre los valores registrados a intervalos de 2 h a lo largo del d铆a, excepto el 12 de agosto de 1997, 95 d铆as despu茅s de la emergencia (DDE), a las 12:00 hora solar en el env茅s de la hoja, cuando la Rs del tratamiento m谩s deficitario (TR4) fue significativamente mayor. Sin embargo, el d茅ficit h铆drico produjo una reducci贸n significativa del LAI y del rendimiento, por lo que la medida de Rs no es un buen indicador del estado h铆drico de la planta cuando el riego se aplica diariamente con dosis deficitarias
Spectral discrimination of wild oat and canary grass in wheat fields for less herbicide application
Wheat, Triticum durum L, is a major cereal crop in Spain with over five
million ha grown annually. Wild oat, Avena sterilis L., and canary grass,
Phalaris spp., are distributed only in patches in wheat fields but
herbicides are applied over entire fields, thus leading to over-application and
unnecessary pollution. To reduce herbicide application, site-specific management
techniques based on weed maps are being developed to treat only weed patches. Intensive
weed scouting from the ground is time-consuming and expensive, and it relies on estimates
of weeds at unsampled points. Remote sensing of weed canopies has been shown to be a more
efficient alternative. The principle of weed remote sensing is that there are differences
in the spectral reflectance between weeds and crops. To test this principle, we studied
spectral signatures taken on the ground in the visible and near-infrared windows for
discriminating wheat, wild oat and canary grass at their last phenological stages.
Late-season phenological stages included initial seed maturation through advanced
maturation for weeds, and initial senescence to senescent for wheat. Spectral signatures
were collected on eight sampling dates from April 28 through May 26 using a handheld field
spectroradiometer. A stepwise discriminant analysis was used to detect differences in
reflectance and to determine the accuracy performance for a species classification as
affected by their phenological stage. Four scenarios or classification sets were
considered: wheat-wild oat-canary grass, with each species represented by a different
group of spectra; wheat and grass weeds, combining the two weed species into one spectral
group; wheat and wild oat with each represented as a single group, and finally, wheat and
canary grass. Our analysis achieved 100% classification accuracy at the phenological
stages of initial seed maturation, and green and advanced seed maturation and partly green
for weeds and wheat, respectively, between the dates of April 28 and May 6. Furthermore,
we reduced the number of hyperspectral wavelengths to thirteen out of 50. Multispectral
analysis also showed that broad wavebands corresponding to those of QuickBird satellite
imagery discriminated wild oat, canary grass and wheat at the same phenological stages and
dates. Our findings are very useful for determining the timeframe during which future
multispectral QuickBird satellite images will be obtained and the concrete wavelengths
that should be used in case of using airborne hyperspectral imaging. Accurate and timely
mapping of the spatial distribution of weeds is a key element in achieving site-specific
herbicide applications for reducing spraying volume of herbicides and costs
Geographic distribution of human Blastocystis subtypes in South America
Blastocystis is a cosmopolitan enteric protist colonizing probably more than 1 billion people. This protozoan exhibits genetic diversity and is subdivided into subtypes (STs). The aim of this study was to determine the distribution of Blastocystis STs in symptomatic and asymptomatic human samples from different countries of South America. A total of 346 fecal samples were genotyped by SSU rDNA showing ST1 (28.3%), ST2 (22.2%), ST3 (36.7%), ST4 (2%), ST5 (2.3%), ST6 (2%), ST7 (2.3%), ST8 (0.6%), ST12 (0.9%) and a novel ST (2.7%). These findings update the epidemiology of Blastocystis in South America and expand our knowledge of the phylogeographic differences exhibited by this stramenopile. 漏 2016 Elsevier B.V
Geographic distribution of human Blastocystis subtypes in South America
Blastocystis is a cosmopolitan enteric protist colonizing probably more than 1 billion people. This protozoan exhibits genetic diversity and is subdivided into subtypes (STs). The aim of this study was to determine the distribution of Blastocystis STs in symptomatic and asymptomatic human samples from different countries of South America. A total of 346 fecal samples were genotyped by SSU rDNA showing ST1 (28.3%), ST2 (22.2%), ST3 (36.7%), ST4 (2%), ST5 (2.3%), ST6 (2%), ST7 (2.3%), ST8 (0.6%), ST12 (0.9%) and a novel ST (2.7%). These findings update the epidemiology of Blastocystis in South America and expand our knowledge of the phylogeographic differences exhibited by this stramenopile. 漏 2016 Elsevier B.V