Search results for " rotation"
showing 10 items of 278 documents
Evaluation of cropping systems for management of herbicide-resistant populations of blackgrass (Alopecurus myosuroides Huds.)
2001
Abstract Simplification of cropping systems often leads to an increase in weed populations which require an intensive use of herbicides to maintain populations at an acceptable level. Due to a heavy reliance on herbicides and a lack of cultural control measures, herbicide-resistant blackgrass (Alopecurus myosuroides Huds.) biotypes appeared recently in France. An experiment was conducted to evaluate the effects of different cropping systems on a population of herbicide-resistant blackgrass. Two crop rotations, one consisting exclusively of winter crops and another including spring crops, were assessed over a three-year period. Crop rotation was combined with different cultural practices (mo…
Effect of timing of grassland destruction on nitrogen mineralization kinetics.
2007
International audience
The role of slabs and oceanic plate geometry in the net rotation of the lithosphere, trench motions, and slab return flow
2012
International audience; [1] Absolute plate motion models with respect to a deep mantle reference frame (e.g., hot spots) typically contain some net rotation (NR) of the lithosphere. Global mantle flow models for the present-day plate setting reproduce similarly oriented NRs but with amplitudes significantly smaller than those found in some high NR Pacific hot spot reference frames. It is therefore important to understand the mechanisms of NR excitation, which we attempt here with two-dimensional cylindrical models of an idealized Pacific domain. We study the influence of slab properties, oceanic ridge position, continental keels, and a weak asthenospheric layer on NR and trench migration. F…
Assessing non-chemical weeding strategies through mechanistic modelling of blackgrass (Alopecurus myosuroides Huds.) dynamics
2010
; Because of environmental and health safety issues, it is necessary to develop strategies that do not rely on herbicides to manage weeds. Introducing temporary grassland into annual crop rotations and mechanical weeding are the two main features that are frequently used in integrated and organic cropping systems for this purpose. To evaluate the contribution of these two factors in interaction with other cropping system components and environmental conditions, the present study updated an existing biophysical model (i.e. AlomySys) that quantifies the effects of cropping system on weed dynamics. Based on previous experiments, new sub-models were built to describe the effects on plant survi…
Alomysys, un modèle simulant l’évolution de la flore adventice sous l’effet des pratiques agricoles
2012
Fiche n°13 - Filière Protéagineux EA EcolDur
Economic assessment of Eucalyptus (spp.) for biomass production as alternative crop in Southern Italy
2015
The increase in energy prices and the stagnation of sales prices of the main agricultural commodities required a rethinking of farm production strategies. Since during the last years, thanks to a series of policies aimed at promoting renewable sources it has been a rapid diffusion of lignocellulosic biomass species, this paper aimed at evaluating the economic feasibility of the introduction of eucalyptus (Eucalyptus spp.) as energy crop for farmers of Southern Italy, by comparing it with traditional crop rotations. In particular, economic analysis has been carried out in a representative case study located in the Sicilian hilly hinterland where, in 2013, it has been built a biomass plant fo…
ANALYSIS OF ENTREPRENEUR’S MOTIVATION TO START BUSINESS (COMPARATIVE STUDIES IN LATVIA IN COMPARISON WITH CANADA, USA, MEXICO)
2014
Business start is important issue from government policy side as well as it has interests of academic researchers worldwide. Researcher attention is paid on decision to start or not to start business (Townsend, et al, 2010), on issues on business takeover or new venture start (Parker, et al, 2012), different approaches in business start – up are analysed (Chwolka and Raith, 2012), there are made evaluations of different research conducted in this area during half a decade (Lambert and Davidson, 2013), made comparisons and cross – country investigations (Clerq, et al, 2012), made different kinds of forecasts (Cassar, 2014). Researchers are interested in performance expectations of entreprene…
Modeling of 137Cs migration in soils using an 80-year soil archive: role of fertilizers and agricultural amendments
2008
An 80-year soil archive, the 42-plot experimental design at the INRA in Versailles (France), is used here to study long-term contamination by 137Cs atmospheric deposition and the fate of this radioisotope when associated with various agricultural practices: fallow land, KCl, NH4(NO3), superphosphate fertilizers, horse manure and lime amendments. The pertinence of a simple box model, where radiocaesium is supposed to move downward by convectional mechanisms, is checked using samples from control plots which had been neither amended, nor cultivated since 1928. This simple model presents the advantage of depending on only two parameters: α, a proportional factor allowing the historical atmosph…
Internal rotation of 1,2-dichloroethane in haloalkane dehalogenase. A test case for analyzing electrostatic effects in enzymes
2003
1,2-Dichoroethane (DCE) is a prototypical molecule for studying electrostatic solvent effects on molecular conformation as far as rotation around the carbon−carbon bond notably changes the electric...
Modification of Chiral Properties Due to Interaction of Polymers and Small Molecules or Ions
1979
The first part of this report deals with changes in the optical rotatory dispersion and circular dichroism resulting from the chemical modification of optically active polymers. Amylose derivatives have very different chiroptical properties compared with cellulose derivatives. Variations in glucosidic bonds and differing secondary structures are described and suggested as causes for this. The N-chlorination of synthetic optically active polyamides is also described, which in all probability proceeds without changing the configuration at the asymmetric C atoms. Reactions of inactive polymers with low molecular weight chiral reagents usually give optical rotation values proportional to the de…