Social-ecological analysis of integrated agriculture-aquaculture systems in Dedza, Malawi

Through the case of integrated agriculture-aquaculture in rural Malawi, this paper argues that hybrid research can reveal new interactions in social-ecological systems not evident when studies by social or natural methods independently. While recent research acknowledges the social and natural dimensions of aquaculture systems, studies often create an artificial divide by attempting to address each aspect in isolation. Social science research has overlooked the biophysical aspects of aquaculture, while scientific research has uncritically accepted orthodox explanations of environmental outcomes without addressing the social contexts of such systems. The social component of this research reveals that fish farmers in Malawi are rejecting practices which do not work in the local context (fertilization with pond mud) and adopting strategies that do work (irrigation with pond water). The physical component of this research compliments the social by elucidating that irrigation with pond water resulted in higher soil nutrient and moisture content. The paper concludes that small-scale aquaculture can make significant contributions to rural household food and income security in Africa and that hybrid research methods can improve our abilities to investigate the complex, connected nature of social-ecological systems.     

A spatiotemporal analysis of cattle herd movement in relation to drinking-water sources: implications for Cryptosporidium control in rural Kenya

Environmental Science and Pollution Research - Given the increasing evidence that domestic contact with livestock is a risk factor for child diarrhoea in low- and middle-income countries, there...     

A within‐individual study of interpersonal conflict as a work stressor: Dispositional and situational moderators

Focusing on interpersonal conflict as a work stressor, the authors used a within‐subjects research design to examine the effect of conflict episodes on employees' negative affect on the job. The roles of agreeableness and social support in moderating the negative effects of conflict episodes were also examined. A two‐week experience‐sampling study revealed that interpersonal conflict influenced employees' intraindividual fluctuations in negative affect. As predicted, agreeableness and social support influenced individuals' patterns of affective responses to conflict, such that conflict was more strongly associated with negative affect for agreeable employees, and for those with lower levels of social support at work. Overall, the results suggest that both personality (agreeableness) and context (social support) significantly moderate the affective implications of interpersonal conflict at work. Copyright © 2010 John Wiley & Sons, Ltd.     

Response of antibiotics and resistance genes to high-intensity and low-intensity manure management

The purpose of this study was to determine the response of antibiotics and antibiotic resistance genes (ARG) to manure management. A pilot field study was conducted using horse manure containing no antibiotics, into which chlortetracycline (CTC), tylosin (TYL), and monensin (MON) were spiked and compared to unspiked controls. Subsequently, a large-scale field study was conducted comparing manure from a dairy with minimal use of antibiotics and a feedlot with regular subtherapeutic use of antibiotics. The manures were subjected to high-intensity management (HIM) (amending, watering, and turning) and low-intensity management (LIM) (no amending, watering, or turning) and were monitored for antibiotic concentrations and levels of tetracycline ARG [tet(W) and tet(O)] using quantitative real-time polymerase chain reaction. All three antibiotics in the pilot study dissipated more rapidly in HIM manure, with half-lives ranging from 4 to 15 d, compared to LIM manure, with half-lives ranging from 8 to 30 d. Levels of tet(W) were significantly higher after 141 d of treatment, but levels of tet(O) were significantly lower in all treatments. In the large-scale study, the feedlot manure had higher initial concentrations than the dairy manure of tetracycline (TC), oxytetracycline (OTC), and CTC as well as tet(W) and tet(O). Tetracycline and OTC dissipated more rapidly in HIM manure, with half-lives ranging from 6 to 15 d, compared to LIM manure, with half-lives ranging from 7 to 31 d. After 6 mo of treatment, tet(W) and tet(O) decreased significantly in feedlot manure, whereas dairy manure required only 4 mo of treatment for similar results.     

Ammonia assessment from agriculture: U.S. status and needs

Recent studies suggest that human activities accelerate the production of reactive nitrogen on a global scale. Increased nitrogen emissions may lead to environmental impacts including photochemical air pollution, reduced visibility, changes in biodiversity, and stratospheric ozone depletion. In the last 50 yr, emissions of ammonia (NH3), which is the most abundant form of reduced reactive nitrogen in the atmosphere, have significantly increased as a result of intensive agricultural management and greater livestock production in many developed countries. These agricultural production practices are increasingly subject to governmental regulations intended to protect air resources. It is therefore important that an accurate and robust agricultural emission factors database exist to provide valid scientific support of these regulations. This paper highlights some of the recent work that was presented at the 2006 Workshop on Agricultural Air Quality in Washington, D.C. regarding NH3 emissions estimates and emission factors from agricultural sources in the U.S. and Europe. In addition, several best management practices are explored as the scientific community attempts to maximize the beneficial use of reactive nitrogen while simultaneously minimizing negative environmental impacts.     

Establishment and Growth of Experimental Grass Species Mixtures on Coal Mine Sites Reclaimed with Municipal Biosolids

The Surface Mining Control and Reclamation Act of 1977 requires that coal mine sites in the United States be reclaimed to establish vegetative cover that is diverse, native, and capable of plant succession. However, there is a question as to whether vegetation established on coal mine sites reclaimed with biosolids is diverse and capable of plant succession. The influx of nutrients with the addition of biosolids leads to long-term dominance by early-successional species, most notably grasses, and consequently, a low establishment of woody and volunteer species. Additionally, many grass species commonly planted in reclamation have aggressive growth habits that lead to their dominance in coal mine plant communities. The establishment and growth of selected grass mixes was evaluated to determine whether alternative grass mixes would be less competitive with woody and volunteer species as compared to commonly used grass mixes. Percent vegetative cover, species richness, and the survival of direct-seeded woody species were assessed for each treatment grass mixture. It was found that Poa compressa and a mixture of P. compressa, Panicum virgatum, and Trifolium repens provided adequate coverage while still allowing the highest species richness and survival of woody species. Use of these species mixtures in coal mine reclamation with biosolids in the eastern United States would likely lead to establishment of a more species-rich plant community with a greater woody species component while still providing erosion control and site protection.     

Larval regulation of worker reproduction in the polydomous ant Novomessor cockerelli

The Science of Nature - Many insects use chemical defence mechanisms to defend themselves against predators. However, defensive secretions are costly to produce and should thus only be used in...