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Rahmatullah Qureshi - One of the best experts on this subject based on the ideXlab platform.
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seed bank density and weed flora Dynamics of bindweed convolvulus arvensis as affected by different tillage systems in rainfed wheat triticum aestivum
International Journal of Agriculture and Biology, 2016Co-Authors: Safdar Ali, M A Malik, Muhammad Ansar, Ghulam Qadir, Rahmatullah QureshiAbstract:Field bindweed (Convolvulus arvensis L.) is a troublesome weed of rainfed areas. Seed bank density, weed population Dynamics and crop productivity were studied in wheat crop under different tillage treatments in a field experiment carried out during summer and winter seasons of 2012‒2013 and 2013‒2014. Different combinations of tillage, integrated with glyphosate herbicide were used in the fallow period (summer season). Results showed that tillage systems along with glyphosate in summer season controlled the establishment of seed bank density as observed in conventional tillage treatment. There was a positive and very week correlation between tillage intensity and seed bank density of C. arvensis L. Similarly the weed population Dynamics with reference to importance value index of weed was minimum in 1 Disc harrowing + 4 cultivations that was not significantly different from no-till + glyphosate. Tillage intensity integrated with glyphosate showed negligible but negative correlation with the weed population Dynamics. In crux, no tillage integrated with glyphosate is recommended for economical reduction of seed bank density and weed population of field bindweed in rainfed wheat areas. © 2016 Friends Science Publishers
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Seed Bank Density and Weed Flora Dynamics of Convolvulus arvensis as Affected by Different Tillage Systems in Rainfed Wheat (Triticum
2016Co-Authors: Safdar Ali, M A Malik, Muhammad Ansar, Ghulam Qadir, Rahmatullah QureshiAbstract:Field bindweed (Convolvulus arvensis L.) is a troublesome weed of rainfed areas. Seed bank density, weed population Dynamics and crop productivity were studied in wheat crop under different tillage treatments in a field experiment carried out during summer and winter seasons of 2012-2013 and 2013-2014. Different combinations of tillage, integrated with glyphosate herbicide were used in the fallow period (summer season). Results showed that tillage systems along with glyphosate in summer season controlled the establishment of seed bank density as observed in conventional tillage treatment. There was a positive and very week correlation between tillage intensity and seed bank density of Convolvulus arvensis L. Similarly the weed population Dynamics with reference to importance value index of weed was minimum in 1 Disc harrowing + 4 cultivations that was not significantly different from no-till + glyphosate. Tillage intensity integrated with glyphosate showed negligible but negative correlation with the weed population Dynamics. In crux, no tillage integrated with glyphosate is recommended for economical reduction of seed bank density and weed population of field bindweed in rainfed wheat areas.
Bhagirath Singh Chauhan - One of the best experts on this subject based on the ideXlab platform.
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Weed population Dynamics, herbicide efficacies, and crop performance in a sprinkler-irrigated maize-rice cropping system
Field Crops Research, 2014Co-Authors: Jhoana L. Opeña, Teodoro Q. Correa, James R. Quilty, Bhagirath Singh ChauhanAbstract:Abstract In the future, maintaining food security will require an increase in rice productivity with less land, labor, and water. Agronomic approaches to reducing the water and labor demands of rice-based cropping systems include crop diversification to include crops with higher water productivity, direct-seeded rice, and irrigation scheduling based on soil water potential or alternate wetting and drying cycles. However, weeds are a major constraint to increasing rice productivity in these systems. A two-year study was conducted to identify the changes in weed population and to evaluate the efficacy of herbicides and their effect on crop performance in a sprinkler-irrigated maize-rice cropping system. The dominance of weed species shifted from a grass weed Echinochloa colona to broadleaved weeds, such as Hedyotis corymbosa, Lindernia spp., and Murdannia nudiflora. At 41 days after sowing (DAS) and at tasseling stage, glyphosate application provided a 90–100% decrease in total weed biomass of maize. The combined effects of all the herbicides applied in rice provided almost 100% control in total weed biomass at 40 DAS. However, the herbicide schedule in the cropping system was ineffective in controlling M. nudiflora. The weed control treatments had no significant effect on the yield of maize [8.7 and 11.5 (herbicide-treated) and 8.4 and 12.0 (partially weedy) Mg ha−1 in 2012 and 2013, respectively], but rice grain yield was influenced significantly. Rice grain yield in herbicide-treated plots in 2012 and 2013 were more than 1.5 and 8.5 times greater than yield achieved in the weedy plots, respectively. A significant negative relationship was found between rice grain yield and weed biomass in both years. Future research in maize-rice cropping systems should focus on the integration of appropriate agronomic practices with herbicide rotation to ensure that weed management strategies are sustainable and effective, and to avoid the risk of herbicide resistance developing in weed populations.
Philip A Stephens - One of the best experts on this subject based on the ideXlab platform.
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modelling the effects of management on population Dynamics some lessons from annual weeds
Journal of Applied Ecology, 2008Co-Authors: Robert P Freckleton, William J Sutherland, A R Watkinson, Philip A StephensAbstract:Summary 1. Agricultural and invasive weeds are major threats to managed and natural ecosystems, costing billions of dollars annually. Models for arable and invasive weed population Dynamics can contribute to the management of problem species through generating predictions of population densities, and how those are likely to respond to changing management. Frequently, however, little attention is paid to quantifying the errors in estimates of model parameters and how these may affect the robustness of model predictions. 2. Most weed models are parameterized using a combination of field-estimated and literature derived parameters. Only rarely are estimates of error available for all parameters, despite the fact that most parameters will be subject to considerable error. 3. Close to extinction boundaries, predictions of population densities may be highly sensitive to small errors in model parameters. However, because of their generally high reproductive capacities, many weeds may occur at high and economically significant densities while close to extinction. Consequently, models may be numerically unstable at ecologically realistic densities. 4. We review methods of dealing with parameter uncertainty in weed modelling. We stress that it is important to recognize that many models may be structurally incorrect and all stabilizing mechanisms may not have been identified. Also, alternative model forms have seldom been explored, although a variety of alternatives to conventional difference equations exist. 5. Synthesis and applications. Only when different management interventions have greatly contrasting effects on population sizes are most models of weed populations likely to provide qualitatively correct predictions of their effects. Quantitative predictions from demographic models will usually be subject to large errors. Modelling methods that account for spatial heterogeneity and other stabilizing effects may yield more accurate predictions; however, their parameterization will often require approaches for data collection very different from those currently used.
Matt Liebman - One of the best experts on this subject based on the ideXlab platform.
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are many little hammers effective velvetleaf abutilon theophrasti population Dynamics in two and four year crop rotation systems
Weed Science, 2005Co-Authors: Paula R Westerman, Matt Liebman, Fabian D Menalled, Robert G Hartzler, Andrew H Heggenstaller, Philip M DixonAbstract:Abstract To improve understanding of relationships between crop diversity, weed management practices, and weed population Dynamics, we used data from a field experiment and matrix models to examine how contrasting crop rotations affect velvetleaf. We compared a 2-yr rotation system (corn–soybean) managed with conventional rates of herbicides with a 4-yr rotation (corn–soybean–triticale + alfalfa–alfalfa) that received 82% less herbicide. In November 2002, a pulse of velvetleaf seeds (500 seeds m−2) was added to 7- by 7-m areas within replicate plots of each crop phase–rotation system combination. Velvetleaf seed, seedling, and reproductive adult population densities, seed production, and seed losses to predators were measured during the next year. Velvetleaf seed production was greater in the 4-yr rotation than in the 2-yr rotation (460 vs. 16 seeds m−2). Averaged over 12 sampling periods from late May to mid-November 2003, loss of velvetleaf seeds to predators also was greater in the 4-yr rotation than i...
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crop rotation and intercropping strategies for weed management
Ecological Applications, 1993Co-Authors: Matt Liebman, Elizabeth DyckAbstract:: Results of a literature survey indicate that weed population density and biomass production may be markedly reduced using crop rotation (temporal diversification) and intercropping (spatial diversification) strategies. Crop rotation resulted in emerged weed densities in test crops that were lower in 21 cases, higher in 1 case, and equivalent in 5 cases in comparison to monoculture systems. In 12 cases where weed seed density was reported, seed density in crop rotation was lower in 9 cases and equivalent in 3 cases when compared to monocultures of the component crops. In intercropping systems where a main crop was intersown with a "smother" crop species, weed biomass in the intercrop was lower in 47 cases and higher in 4 cases than in the main crop grown alone (as a sole crop); a variable response was observed in 3 cases. When intercrops were composed of two or more main crops, weed biomass in the intercrop was lower than in all of the component sole crops in 12 cases, intermediate between component sole crops in 10 cases, and higher than all sole crops in 2 cases. It is unclear why crop rotation studies have focused on weed density, whereas intercropping studies have focused on weed biomass. The success of rotation systems for weed suppression appears to be based on the use of crop sequences that create varying patterns of resource competition, allelopathic interference, soil disturbance, and mechanical damage to provide an unstable and frequently inhospitable environment that prevents the proliferation of a particular weed species. The relative importance and most effective combinations of these weed control tactics have not been adequately assessed. In addition, the weed-suppressive effects of other related factors, such as manipulation of soil fertility Dynamics in rotation sequences, need to be examined. Intercrops may demonstrate weed control advantages over sole crops in two ways. First, greater crop yield and less weed growth may be achieved if intercrops are more effective than sole crops in usurping resources from weeds or suppressing weed growth through allelopathy. Alternatively, intercrops may provide yield advantages without suppressing weed growth below levels observed in component sole crops if intercrops use resources that are not exploitable by weeds or convert resources to harvestable material more efficiently than sole crops. Because of the difficulty of monitoring the use of multiple resources by intercrop/weed mixtures throughout the growing season, identification of specific mechanisms of weed suppression and yield enhancement in intercrop systems has so far proven elusive. Significant advances in the design and improvement of weed-suppressive crop rotation and intercropping systems are most likely to occur if three important areas of research are addressed. First, there must be continued attention to the study of weed population Dynamics and crop-weed interference in crop rotation and intercropping systems. More information is needed concerning the effects of diversification of cropping systems on weed seed longevity, weed seedling emergence, weed seed production and dormancy, agents of weed mortality, differential resource consumption by crops and weeds, and allelopathic interactions. Second, there needs to be systematic manipulation of specific components of rotation and intercropping systems to isolate and improve those elements (e.g., interrow cultivation, choice of crop genotype) or combinations of elements that may be especially important for weed control. Finally, the weed-related impacts of combining crop rotation and intercropping strategies should be assessed through careful study of extant, complex farming systems and the design and testing of new integrated approaches. Many aspects of crop rotation and intercropping are compatible with current farming practices and could become more accessible to farmers if government policies are restructured to reflect the true environmental costs of agricultural production.
J L Gonzalezandujar - One of the best experts on this subject based on the ideXlab platform.
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controlling annual weeds in cereals by deploying crop rotation at the landscape scale avena sterilis as an example
Ecological Applications, 2012Co-Authors: L Gonzalezdiaz, Femke Van Den Berg, Frank Van Den Bosch, J L GonzalezandujarAbstract:Weed control through crop rotation has mainly been studied in a nonspatial context. However, weed seeds are often spread beyond the crop field by a variety of vectors. For weed control to be successful, weed management should thus be evaluated at the landscape level. In this paper we assess how seed dispersal affects the interactions between crop rotation and landscape heterogeneity schemes with regard to weed control. A spatially explicit landscape model was developed to study both short- and long-term weed population Dynamics under different management scenarios. We allowed for both two- and three-crop species rotations and three levels of between-field weed seed dispersal. All rotation scenarios and seed dispersal fractions were analyzed for both completely homogeneous landscapes and heterogeneous landscapes in which more than one crop was present. The potential of implementing new weed control methods was also analyzed. The model results suggest that, like crop rotation at the field level, crop rotation implemented at the landscape level has great potential to control weeds, whereby both the number of crop species and the cropping sequence within the crop rotation have significant effects on both the short- and long-term weed population densities. In the absence of seed dispersal, weed populations became extinct when the fraction of each crop in the landscape was randomized. In general, weed seed densities increased in landscapes with increasing similarity in crop proportions, but in these landscapes the level of seed dispersal affected which three-crop species rotation sequence was most efficient at controlling the weed densities. We show that ignoring seed dispersal between fields might lead to the selection of suboptimal tactics and that homogeneous crop field patches that follow a specific crop rotation sequence might be the most sustainable method of weed control. Effective weed control through crop rotation thus requires coordination between farmers with regard to cropping sequences, crop allocation across the landscape, and/or the fraction of each crop across the landscape.