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A study of the impact of two agroecological development programs in central America was conducted in 1994, five years and fifteen years after the programmes had ended. Yields of maize and beans being achieved by those farmers involved in each program were, on the average, more than seven times the yields being achieved at the time of program initiation. Increases in yields and incomes were achieved through the use of a large number of innovations, involving especially soil retention measures, purchased organic matter, intercropped green manure/cover crops, natural pest control, crop diversification and crop rotations. Use of chemical fertilizer was reduced, herbicides avoided almost entirely, and several substitutes for pesticides are now used. These technologies, plus more recent innovations such as microscale water harvesting and precision planting, should enable small farmers around the world to increase productivity enough that the world can avoid major hunger over the next 30 years, without increasing substantially, if at all, the world's use of chemical inputs.  相似文献   
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Sterols as a measure of fecal pollution   总被引:3,自引:0,他引:3  
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A preliminary laboratory study was conducted to investigate the impact of different residual types and sediment surface roughness on copper contaminant fluxes to the water column. Sediments from Torch Lake, Michigan served as the test samples. These sediments are mining by‐products with elevated Cu levels. Six experiments were run during which the sediments were conditioned to simulate different forms of residuals. During these experiments, the water column above the sediments was circulated via peristaltic pumping or orbital shaking and the total and dissolved Cu levels were monitored periodically for 15 days. Dissolved Cu levels indicated that during the first 48 hr the water column concentrations approached equilibrium for all six cases. Total Cu levels increased with time and did reach equilibrium but were more susceptible to fluctuations in water column suspended solids levels. Analysis of the resulting dissolved Cu data indicated that the resulting water column Cu concentrations differed with sediment surface and residual type. The highest dissolved Cu water column concentrations were observed for a roughened surface with a larger surface area. The lowest water column dissolved Cu levels were observed for the case with sediment slurry placed over clean sand. The dissolved Cu levels in the water column for all six simulated conditions were several orders higher than the USEPA ambient water quality criteria for protection of aquatic life. © 2014 Wiley Periodicals, Inc.*  相似文献   
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Water quality monitoring involves a complex set of steps and a variety of approaches. Its goals include understanding of aquatic habitats, informing management and facilitating decision making, and educating citizens. Environmental nongovernmental organizations (ENGOs) are increasingly engaged in water quality monitoring and act as environmental watchdogs and stewards of water resources. These organizations exhibit different monitoring mandates. As government involvement in water quality monitoring continues to decline, it becomes essential that we understand their modi operandi. By doing so, we can enhance efficacy and encourage data sharing and communication. This research examined Canadian ENGOs that collect their own data on water quality with respect to water quality monitoring activities and information needs. This work had a twofold purpose: (1) to enhance knowledge about the Canadian ENGOs operating in the realm of water quality monitoring and (2) to guide and inform development of web-based geographic information systems (GIS) to support water quality monitoring, particularly using benthic macroinvertebrate protocols. A structured telephone survey was administered across 10 Canadian provinces to 21 ENGOs that undertake water quality monitoring. This generated information about barriers and challenges of data sharing, commonly collected metrics, human resources, and perceptions of volunteer-collected data. Results are presented on an aggregate level and among different groups of respondents. Use of geomatics technology was not consistent among respondents, and we found no noteworthy differences between organizations that did and did not use GIS tools. About one third of respondents did not employ computerized systems (including databases and spreadsheets) to support data management, analysis, and sharing. Despite their advantage as a holistic water quality indicator, benthic macroinvertebrates (BMIs) were not widely employed in stream monitoring. Although BMIs are particularly suitable for the purpose of citizen education, few organizations collected this metric, despite having public education and awareness as part of their mandate.  相似文献   
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This study examined how the perceptions and attitudes of third party observers of punishment events are influenced by characteristics of the violator and the punishment event itself. Using a scenario methodology, we manipulated the past performance record of the violator and the severity of the consequences administered by the supervisor. Subjects read the scenarios from the point of view of a coworker/ observer, and responded to questions measuring their perceptions of retributive justice and fairness of the punishment, as well as their desire for more punishment, their attitudes toward the supervisor, and their intention to leave the organization. Results showed that observers judged violators with poor performance records as more deserving of punishment than those with good records, and judged events as more fair when the manager's response was severe. Interactions between these two factors were also found to be significant. Implications of these findings are discussed. © 1998 John Wiley & Sons, Ltd.  相似文献   
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