Modelización de la emergencia de Conyza bonariensis en clima mediterráneo

Ponencia presentada en el XIII Congreso Nacional de Malgerbología, "Plantas Invasoras Resistencias a Herbicidas y Detección de Malas Hierbas", celebrado en San Cristóbal de la Laguna del 22 al 24 de noviembre de 2011.Peer Reviewe

Herbicidal strategies to control Phalaris brachystachys in a wheat-sunflower rotation: a simulation approach

Phalaris brachystachys is a common and troublesome weed in winter cereals in Mediterranean countries. A deterministic model was developed to simulate P. brachystachys seedbank dynamics in the wheat-sunflower rotation, a commonly practiced cropping system in southern Spain, under different herbicide-based management scenarios: no herbicide application, full herbicide dose (standard rate) and two reduced dose rates (75 and 50% of the standard rate). Without treatment, a steady increase of the seed bank is predicted up to an equilibrium level of 54,859 seeds m-2 (575 plants m-2) after 25 years. Full dose herbicide applications in wheat years resulted in a progressive seed bank decline over years. Reducing the efficacy of the herbicide by using 50% or 75% of the recommended rate resulted in no long-term seed bank decline. Instead, a population increase until equilibrium densities is predicted. A sensitivity analysis showed that seedling survival and fecundity were the most sensitive demographic parameters under the full dose strategy, whereas fecundity and seedbank mortality were the most sensitive parameters under reduced dose strategies. Reduced dose strategies tended to be less sensitive than the full dose strategy. Simulations indicated that long-term control of this weed may be attained under full dose, highly effective, herbicide applications. Unless effectiveness could be maintained at very high levels, reduced herbicide doses may not be a recommendable option for the long-term control of this species in a wheat-sunflower rotation

İLK 500 ARASINDA YER ALAN DEMİR-ÇELİK SEKTÖRÜNE AİT FİRMALARIN VZA VE MALMQUIST YÖNTEMLERİYLE VERİMLİLİKLERİNİN ÖLÇÜMÜ

DergiPark: 336920klujfeasThe main objectives of the study is to examine the efficiency performance of the firms among the 500biggest firms operating in iron and steel industry between the years of 2013 thru 2015 and to revealthe development and causes of total factor productivity besides the partial productivity by dataenvelopment analysis and Malmquist total factor productivity index based on the DEA. According tothe result, it has been shown that only 1 company works 100% efficiently during 3 years period.According to the Malmquist total factor productivity index result, it has been found that 11 firmsprogressed in a positive way. Araştırmanın temel amacı, 2013-2015 döneminde en büyük 500 şirket arasına yer alan demir-çeliksektörüne ait firmaların verimlilik performansını incelemek, kısmi verimliliklerin yanı sıra toplamfaktör verimliliği gelişimini ve nedenlerini ortaya koymaktır.Bu çalışmada veri elde edilebilirliği dikkate alınarak ülkemizin en büyük 500 şirketi içerisindebulunan demir çelik sektöründe faaliyet gösteren 13 firma incelenmiştir. Bu firmaların 2013 - 2015yıllarındaki verimlilikleri hem VZA hem de VZA’ya dayanan Malmquist toplam faktör verimliliğiendeksinden yararlanılarak analiz edilmiştir. Analiz sonucunda, üç yılda da tek bir firmanın etkinçalışma sergilediği VZA yöntemi ile elde edilmiştir. Malmquist toplam faktör verimliliği endeksisonuçlarına göre ise, on bir firmanın olumlu yönde ilerleme gösterdiği tespit edilmiştir.&nbsp

A hydrothermal seedling emergence model for Conyza bonariensis

Conyza bonariensis is a South American native annual Asteraceae that has been introduced to the Mediterranean, where it behaves as a ruderal plant and a weed that is difficult to control in several crops. The development of predictive models can contribute to control measures at early growth stages, but currently there are no studies to predict seedling emergence of Conyza species. Our objectives were to develop and evaluate a model for predicting emergence response of C. bonariensis to the soil hydrothermal environment. A hydrothermal seed germination model was fitted to time course germination data from germination tests carried out at different constant temperatures and water potentials with the aim of establishing the hydrothermal parameters characterising C. bonariensis seed germination. The relationship between cumulative seedling emergence and cumulative hydrothermal time under field conditions was analysed using the Gompertz function. Model development was based on 2 years' data from a field experiment. Base temperature and base water potential for seed germination were estimated at 10.6°C and -0.70 ± 0.151 MPa, respectively. The emergence model showed a very good fit to the experimental data. According to this model, seedling emergence starts at 15 accumulated hydrothermal time (HTT) after sowing, and 50 and 95% emergence is completed at 53 HTT and 105 HTT, respectively. For model evaluation, independent field experiments were carried out in two localities. Cumulative seedling emergence was accurately predicted by the model. Results indicate that this model can be useful as a predictive tool contributing to effective control of C. bonariensis populations. © 2013 European Weed Research Society.This work has been partially funded by FEDER funds and the Spanish Ministry of Innovation and Science (Projects AGL2009-7883) and by a scholar grant from CDCH-UCV (Council of Scientific and Humanistic-Central University of Venezuela) to Castor Zambrano.Peer Reviewe

A cohort-based stochastic model of the population dynamic and long-term management of Conyza bonariensis in fruiting tree crops

Conyza bonariensis is currently a frequent and abundant weed in fruiting tree crops associated with non-tillage in Mediterranean climate areas, such as citrus groves and olive orchards. Because of the mild winters characteristic of this climate, an extended season of seedling emergence, from early autumn to early spring, is often found for this species, this leading to multiple annual cohorts. In this work, a cohort-based stochastic model of C. bonariensis population dynamics was developed and used to simulate the behaviour of the seed bank in Mediterranean fruiting tree crops under ten contrasting management strategies, including single or integrated herbicide and non chemical control measures. The demographic impact of tillage system (ploughing vs. no-till), the use of cover, and timing of herbicide applications was simulated. The model was parameterized with information taken from the literature. In the absence of any control and under no-tillage the modelled seed bank reached an average equilibrium density of 378,092 ± 10,865 seeds m−2. The most effective management strategy integrated no-till, the use of cover and early and late applications of herbicides, which reduced the equilibrium densities of the seed bank by 78.7%. A sensitivity analysis indicated that C. bonariensis populations in Mediterranean fruiting tree crops are particularly sensitive to small changes in the demographic parameters associated with the earlier cohort and to the efficacy of early herbicide treatments. A diversified, integrated approach including different interventions of chemical and cultural nature appears to be the most successful strategy at the field level for controlling C. bonariensis in Mediterranean fruiting tree crops.This work has been funded by FEDER (European Regional Development Funds) and the Spanish Ministry of Innovation and Science (Project AGL2009-7883) and by a scholar grant from CDCH-UCV (Council of Scientific and Humanistic – Central University of Venezuela) to Castor Zambrano.Peer reviewe

Desarrollo de un modelo bioeconómico de Phalaris brachystachys y simulación de escenarios de manejo

Póster presentado en el XIII Congreso Nacional de Malgerbología, celebrado en San Cristóbal de la Laguna del 22 al 24 de noviembre de 2011.Peer Reviewe