Field olfactometry assessment of dairy manure land application methods

Surface application of manure in reduced tillage systems generates nuisance odors, but their management is hindered by a lack of standardized field quantification methods. An investigation was undertaken to evaluate odor emissions associated with various technologies that incorporate manure with minimal soil disturbance. Dairy manure slurry was applied by five methods in a 3.5-m swath to grassland in 61-m-inside-diameter rings. Nasal Ranger Field Olfactometer (NRO) instruments were used to collect dilutions-to-threshold (D/T) observations from the center of each ring using a panel of four odor assessors taking four readings each over a 10-min period. The Best Estimate Threshold D/T (BET10) was calculated for each application method and an untreated control based on preapplication and <1 h, 2 to 4 h, and approximately 24 h after spreading. Whole-air samples were simultaneously collected for laboratory dynamic olfactometer evaluation using the triangular forced-choice (TFC) method. The BET10 of NRO data composited for all measurement times showed D/T decreased in the following order (a = 0.05): surface broadcast > aeration infiltration > surface + chisel incorporation > direct ground injection Sshallow disk injection > control, which closely followed laboratory TFC odor panel results (r = 0.83). At 24 h, odor reduction benefits relative to broadcasting persisted for all methods except aeration infiltration, and odors associated with direct ground injection were not different from the untreated control. Shallow disk injection provided substantial odor reduction with familiar toolbar equipment that is well adapted to regional soil conditions and conservation tillage operations.     

Manure application technology in reduced tillage and forage systems: a review

Managing manure in reduced tillage and forage systems presents challenges, as incorporation by tillage is not compatible. Surface-applied manure that is not quickly incorporated into soil provides inefficient delivery of manure nutrients to crops due to environmental losses through ammonia (NH3) volatilization and nutrient losses in runoff, and serves as a major source of nuisance odors. An array of technologies now exist to facilitate the incorporation of liquid manures into soil with restricted or minor soil disturbance, some of which are new: shallow disk injection; chisel injection; aeration infiltration; pressure injection. Surface banding of manure inforages decreases NH3 emissions relative to surface broadcasting, as the canopy can decrease wind speed over the manure, but greater reductions can be achieved with manure injection. Soilaeration is intended to hasten manure infiltration, but its benefits are not consistent and may be related to factors such as soildrainage characteristics. Work remains to be done on refining its method of use and timing relative to manure application, which may improve its effectiveness. Placing manure under the soil surface efficiency by injection offers much promise to improve N use efficiency through less NH3 volatilization, reduced odors and decreased nutrient losses in runoff, relative to surface application. We identified significant gaps in our knowledge as manyof these technologies are relatively new, and this should help target future research efforts including environmental, agronomic, and economic assessments.     

Modelling of occupational respirable crystalline silica exposure for quantitative exposure assessment in community-based case-control studies

We describe an empirical model for exposure to respirable crystalline silica (RCS) to create a quantitative job-exposure matrix (JEM) for community-based studies. Personal measurements of exposure to RCS from Europe and Canada were obtained for exposure modelling. A mixed-effects model was elaborated, with region/country and job titles as random effect terms. The fixed effect terms included year of measurement, measurement strategy (representative or worst-case), sampling duration (minutes) and a priori exposure intensity rating for each job from an independently developed JEM (none, low, high). 23,640 personal RCS exposure measurements, covering a time period from 1976 to 2009, were available for modelling. The model indicated an overall downward time trend in RCS exposure levels of -6% per year. Exposure levels were higher in the UK and Canada, and lower in Northern Europe and Germany. Worst-case sampling was associated with higher reported exposure levels and an increase in sampling duration was associated with lower reported exposure levels. Highest predicted RCS exposure levels in the reference year (1998) were for chimney bricklayers (geometric mean 0.11 mg m(-3)), monument carvers and other stone cutters and carvers (0.10 mg m(-3)). The resulting model enables us to predict time-, job-, and region/country-specific exposure levels of RCS. These predictions will be used in the SYNERGY study, an ongoing pooled multinational community-based case-control study on lung cancer.     

The Relationship Between Shift Work Schedules and Spillover in a Sample of Nurses

The aim of the present study was to estimate spillover effects between the work and the family sphere in a sample of nurses (N = 2058). Hierarchical regression analyses investigated whether shift work schedules were associated with negative or positive spillover, both from family to work and vice versa, controlling for demographic factors, job demands and decision latitude. With daytime work as a reference group, all types of shift work (day and evening shift, night shift only and rotating 3 shift) were associated with higher negative work-to-family spillover. Night work was associated with significantly less negative family-to-work spillover. None of the different shift work schedules were related to any type of positive spillover. The results indicate that working outside of daytime hours is less compatible with workers’ family lives, compared to working ordinary day shifts. On the other hand, working night shifts only was associated with reduced negative family-to-work spillover.     

How conservation and humanitarian groups respond to production of border security on the Arizona–Sonora border

US policies for securing the border with Mexico are driven by multiple political concerns, including the desire to control illegal trade and immigration in a way that conveys “border security” to a national audience. Highly visible border enforcement near urban centres and via the border fence has pushed migrants into far less visible and remote wilderness areas, driving both ecological degradation and a humanitarian crisis. This study employed ethnographic methods to explore how natural resource agency employees and humanitarian volunteers in Altar Valley Arizona perceived and responded to the production of border security. We found that both groups recognised human rights and environmental concerns, although they assigned different priorities and addressed them through conflicting means. As in other cases where consumers are separated from production practices, there was a general consensus among informants that it was important to raise the consciousness of the national audience about the negative externalities of producing border security.     

Sexual dimorphism in Bosmina: the role of morphology, drag, and swimming

Some Bosmina water flea species develop morphological antipredatory defenses, such as long antennules and a high carapace, but in Bosmina (Eubosmina) coregoni gibbera these traits are larger and more variable in females than in males. Here we propose that this sexual dimorphism derives from differential costs of hydrodynamic drag and selection for mobility in males. We tested this hypothesis by estimating drag of several Bosmina morphologies by using scale models sinking in glycerin of different concentrations and viscosities. Body forms included males, sexual and asexual females of B. c. gibbera, and males and asexual females of Bosmina (Eubosmina) longispina, a taxon with less variable body shape. For a given body length or body volume, male models had lower drag than models of sexual and asexual females, suggesting that males can swim 14-28% faster with the same energy consumption. Consistent with this conclusion, video recordings showed that males of B. c. gibbera advanced 55-73% farther than females in each swimming stroke. We conclude that hydrodynamic drag may have significant implications for swimming and evolution of sexual dimorphism in water fleas, and we suggest that males lack the defensive structures of females of B. c. gibbera (e.g., high carapaces) because competition over mates favors low drag.