Economics of Management Zone Delineation in Cotton Precision Agriculture

This paper develops a management zone delineation procedure based on a spatial clustering approach and evaluates its economic impact for the case of Texas cotton production. The results show that there is potential economic value in using a spatial approach to management zone delineation, but its value critically depends on the cost of collecting soil test information needed to delineate those zones.Management Zones, Exploratory Spatial Data Analysis, Site-Specific Nitrogen Management, Cotton Precision Agriculture, Crop Production/Industries, Q12,

Economics of Management Zone Delineation in Cotton Precision Agriculture

This paper develops a management zone delineation procedure based on a spatial statistics approach and evaluates its economic impact for the case of Texas cotton production. With the use of an optimization model that utilizes a yield response function estimated through spatial econometric methods, we found that applying variable N rates based on the management zones delineated would result in higher cotton yields and higher net returns, above Nitrogen cost, relative to uniformly applying a single N rate for the whole field. In addition, a variable rate N application using the delineated management zones produced higher net returns, above Nitrogen cost, relative to a variable N rate system where the zones are based solely on landscape position. This is indicative of the potential economic value of using a spatial statistics approach to management zone delineation.Management Zones, Exploratory Spatial Data Analysis, Site-Specific Nitrogen Management, Cotton Precision Agriculture., Crop Production/Industries, Q1, Q16,

On the Evolution of Thermonuclear Flames on Large Scales

The thermonuclear explosion of a massive white dwarf in a Type Ia supernova explosion is characterized by vastly disparate spatial and temporal scales. The extreme dynamic range inherent to the problem prevents the use of direct numerical simulation and forces modelers to resort to subgrid models to describe physical processes taking place on unresolved scales. We consider the evolution of a model thermonuclear flame in a constant gravitational field on a periodic domain. The gravitational acceleration is aligned with the overall direction of the flame propagation, making the flame surface subject to the Rayleigh-Taylor instability. The flame evolution is followed through an extended initial transient phase well into the steady-state regime. The properties of the evolution of flame surface are examined. We confirm the form of the governing equation of the evolution suggested by Khokhlov (1995). The mechanism of vorticity production and the interaction between vortices and the flame surface are discussed. The results of our investigation provide the bases for revising and extending previous subgrid-scale model.Comment: 15 pages, 22 postscript figures. Accepted for publication by the Astrophysical Journal. High resolution figures can be found at http://flash.uchicago.edu/~zhang/research_paper.htm

Dietary Analysis of Batfishes (Lophiiformes: Ogcocephalidae) in the Gulf of Mexico

Stomach content analyses, performed on three species of batfishes, Halieutichthys aculeatus, Ogcocephalus declivirostris, and Ogcocephalus pantosticus collected in the Gulf of Mexico in summer (June-July) and fall (Oct.-Nov.) 2002 and 2003, revealed a variety of benthic invertebrates, particularly gastropods, polychaete worms, and xanthid crabs. Schoener\u27s dietary overlap indices (Sl) were calculated between the three species within the same seasons, and within each species between seasons. SI values indicated that each species consumed a different assemblage of prey and that two of the species exhibited temporal variation in diet

Allosteric collaboration between elongation factor G and the ribosomal L1 stalk directs tRNA movements during translation

Determining the mechanism by which transfer RNAs (tRNAs) rapidly and precisely transit through the ribosomal A, P and E sites during translation remains a major goal in the study of protein synthesis. Here, we report the real-time dynamics of the L1 stalk, a structural element of the large ribosomal subunit that is implicated in directing tRNA movements during translation. Within pre-translocation ribosomal complexes, the L1 stalk exists in a dynamic equilibrium between open and closed conformations. Binding of elongation factor G (EF-G) shifts this equilibrium towards the closed conformation through one of at least two distinct kinetic mechanisms, where the identity of the P-site tRNA dictates the kinetic route that is taken. Within post-translocation complexes, L1 stalk dynamics are dependent on the presence and identity of the E-site tRNA. Collectively, our data demonstrate that EF-G and the L1 stalk allosterically collaborate to direct tRNA translocation from the P to the E sites, and suggest a model for the release of E-site tRNA

Brown Stem Rot and its Interaction with the Soybean Cyst Nematode

Brown stem rot (BSR) of soybeans is caused by the fungal vascular pathogen Cadophora gregata (previously named Phialophora gregata). BSR is an economically important disease of soybeans in the north central United States, being prevalent in 68 to 73% of the soybean fields of Illinois, Iowa, and Minnesota (Workneh et al. 1999). There are two genetic types (called genotypes) of C. gregata that differ in their ability to cause foliar symptoms on susceptible soybeans (Chen et al. 2000). Infection by genotype A of the fungus can result in mild to severe brown discoloration of the pith and severe foliar symptoms on susceptible soybeans and mild or no foliar symptom on resistant soybeans. In contrast, infection by genotype B of the fungus causes mild to severe brown discoloration of the pith, but mild or no foliar symptoms. Soybeans can be colonized by both genotypes of the fungus without exhibiting stem or foliar symptoms (Taboret al. 2003a). Consequently, hidden yield loss due to BSR may frequently occur

Towards improved psychological outcomes for survivors of burn injuries

Editoria

Un análisis económico de la aproximación estadística para el establecimiento de zonas de manejo en agricultura de precisión: caso de algodón en Texas

Este artículo desarrolla un proceso para el establecimiento de zonas de manejo basado en una aproximación estadística espacial y evalúa su impacto económico para el caso de producción de algodón en Texas. Con el uso de un modelo de optimización que utiliza funciones de producción estimadas tomando en cuenta la autocorrelación espacial mediante métodos de econometría espacial, se encontró que al aplicar nitrógeno a una tasa variable, basada en las zonas de manejo delineadas, se obtienen rendimientos de algodón más altos comparados con los rendimientos obtenidos al aplicar una tasa uniforme de nitrógeno sobre toda la unidad productiva. Así mismo, se encontró que las aplicaciones de N a una tasa variable generan ingresos netos superiores comparados con los ingresos netos generados por la aplicación uniforme de N a la tasa agronómica sugerida, y retornos inferiores comparados con la aplicación uniforme derivada del óptimo económico. Adicionalmente, se encontró que niveles promedios de nitrógeno más bajos son requeridos con las aplicaciones de nitrógeno a una tasa variable para alcanzar rendimientos más altos comparados con la aplicación uniforme de nitrógeno.Zonas de manejo, análisis espacial exploratorio de datos, manejo espacial específico de nitrógeno, agricultura de precisión con aplicaciones en algodón.