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Crop Production Systems (crop + production_system)
Selected AbstractsSoils and land use in the Tigray highlands (Northern Ethiopia)LAND DEGRADATION AND DEVELOPMENT, Issue 3 2008J. Nyssen Abstract Land use in a 208,ha representative catchment in the Tigray Highlands, Dogu'a Tembien district in Northern Ethiopia was studied in relation to soil geography. Typical soils are Vertisols, Vertic Cambisols, Cumulic Regosols, Calcaric Regosols and Phaeozems. Patterns of land use vary greatly within the catchment and results from ,2 -tests showed strong associations (p,<,0·001) between soil type and land use and crop production system. There is a strong association between cropland and colluvium high in basaltic content because the most fertile soils, such as Vertisols and Vertic Cambisols, have developed on this material. Preference is for autochthonous soils on in situ parent material, irrespective of the rock type, to be put under rangeland. Land use by smallholders in Dogu'a Tembien appears to be the result primarily of the interaction between environmental and social factors. Copyright © 2007 John Wiley & Sons, Ltd. [source] A host-pathogen simulation model: powdery mildew of grapevinePLANT PATHOLOGY, Issue 3 2008A. Calonnec An epidemiological model simulating the growth of a single grapevine stock coupled to the dispersal and disease dynamics of the airborne conidia of the powdery mildew pathogen Erysiphe necator was developed. The model input variables were either climatic (temperature, wind speed and direction) or related to the pathogen (location and onset of primary infection). The environmental input variables dictated plant growth and pathogen spread (latent period, infection, lesion growth, conidial spore production and release). Input parameters characterized the crop production system, the growth conditions and the epidemiological characteristics of the pathogen. Output described, at each time step, number, age and pattern of healthy and infected organs, infected and infectious leaf area and aerial density of spores released. Validation of the model was achieved by comparing model output with experimental data for epidemics initiated at different times of host growth. Epidemic behaviour for two contrasting years of crop development and 7 phenological stages at the time of primary infection (PI) was examined. For PI occurring at day 115 a vine with late budbreak (1998) showed 58% of primary leaves diseased at flowering compared with only 19% for a vine with early budbreak (2003). Depending on the phenological stage at PI (1,4 leaves), the proportion of diseased primary leaves decreased from 42% to 6% at flowering. Simulations suggested that differences resulted from the interplay between the timing of the first sporulation event, the phenological stage at the time of initial infection, and the age structure and spatial distribution of the leaf population. [source] Interactions between arbuscular mycorrhizal fungi and bacteria and their potential for stimulating plant growthENVIRONMENTAL MICROBIOLOGY, Issue 1 2006Veronica Artursson Summary Arbuscular mycorrhizal (AM) fungi and bacteria can interact synergistically to stimulate plant growth through a range of mechanisms that include improved nutrient acquisition and inhibition of fungal plant pathogens. These interactions may be of crucial importance within sustainable, low-input agricultural cropping systems that rely on biological processes rather than agrochemicals to maintain soil fertility and plant health. Although there are many studies concerning interactions between AM fungi and bacteria, the underlying mechanisms behind these associations are in general not very well understood, and their functional properties still require further experimental confirmation. Future mycorrhizal research should therefore strive towards an improved understanding of the functional mechanisms behind such microbial interactions, so that optimized combinations of microorganisms can be applied as effective inoculants within sustainable crop production systems. In this context, the present article seeks to review and discuss the current knowledge concerning interactions between AM fungi and plant growth-promoting rhizobacteria, the physical interactions between AM fungi and bacteria, enhancement of phosphorus and nitrogen bioavailability through such interactions, and finally the associations between AM fungi and their bacterial endosymbionts. Overall, this review summarizes what is known to date within the present field, and attempts to identify promising lines of future research. [source] Weed species shifts in glyphosate-resistant cropsPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 4 2008Micheal DK Owen Abstract The adoption of glyphosate-based crop production systems has been one of the most important revolutions in the history of agriculture. Changes in weed communities owing to species that do not respond to current glyphosate-based management tactics are rapidly increasing. Clearly, glyphosate-resistant crops (GRCs) do not influence weeds any more than non-transgenic crops. For most crops, the trait itself is essentially benign in the environment. Rather, the weed control tactics imposed by growers create the ecological selection pressure that ultimately changes the weed communities. This is seen in the adoption of conservation tillage and weed management programs that focus on one herbicide mode of action and have hastened several important weed population shifts. Tillage (disturbance) is one of the primary factors that affect changes in weed communities. The intense selection pressure from herbicide use will result in the evolution of herbicide-resistant weed biotypes or shifts in the relative prominence of one weed species in the weed community. Changes in weed communities are inevitable and an intrinsic consequence of growing crops over time. The glyphosate-based weed management tactics used in GRCs impose the selection pressure that supports weed population shifts. Examples of weed population shifts in GRCs include common waterhemp [Amaranthus tuberculatus (Moq ex DC) JD Sauer], horseweed (Conyza canadensis L), giant ragweed (Ambrosia trifida L) and other relatively new weed problems. Growers have handled these weed population shifts with varying success depending on the crop. Copyright © 2008 Society of Chemical Industry [source] The Economic Value of Soil Quality under Alternative Management in the Canadian PrairiesCANADIAN JOURNAL OF AGRICULTURAL ECONOMICS, Issue 2 2003K. W. Belcher This paper describes a dynamic simulation model that integrates environmental and economic components of agricultural crop production systems to predict changes in soil quality and the concomitant impact on economic returns. The model is used to simulate crop yield, soil quality and economic performance of a conventional crop rotation and several alternative crop rotations in two contrasting environments in western Canada over a 50-year period. This information is used to quantify the impact of the crop rotations on soil organic carbon (SOC) and the economic value of on-site SOC changes. The estimated value of these impacts range from $0.20/t to $2.10/t of SOC/ha/yr. Les auteurs décrivent un modèle de simulation dynamique intégrant les paramètres environnementaux et économiques des systèmes de production végétale pour prévoir la qualityé du sol et l'incidence de cette dernière sur les rentrées. Le modèle simule le rendement des cultures, la qualityé du sol et la performance économique d'un système d'assolement classique et de plusieurs de ses variantes, dans deux milieux contrastants de l'ouest du Canada, sur une période de 50 ans. Les résultats ont permis de quantifier l'incidence de l'assolement sur la teneur du sol en carbone organique et la valeur économique des fluctuations d'une telle concentration. Les auteurs situent cette incidence entre 0.20 $ et 2,10 $ la tonne de carbone organique par hectare et par année. [source] | ||||||||||