Development of a Quantitative Pasture Phosphorus Management Tool Using the SWAT Model1

Abstract: Assessment tools to evaluate phosphorus loss from agricultural lands allow conservation planners to evaluate the impact of management decisions on water quality. Available tools to predict phosphorus loss from agricultural fields are either: (1) qualitative indices with limited applicability to address offsite water quality standards, or (2) models which are prohibitively complex for application by most conservation planners. The purpose of this research was to develop a simple interface for a comprehensive hydrologic/water quality model to allow its usage by farmers and conservation planners. The Pasture Phosphorus Management (PPM) Calculator was developed to predict average annual phosphorus (P) losses from pastures under a variety of field conditions and management options. PPM Calculator is a vastly simplified interface for the Soil and Water Assessment Tool (SWAT) model that requires no knowledge of SWAT by the user. PPM Calculator was validated using 33 months of data on four pasture fields in northwestern Arkansas. This tool has been extensively applied in the Lake Eucha/Spavinaw Basin in northeastern Oklahoma and northwestern Arkansas. PPM Calculator allows conservation planners to take advantage of the predictive capacity of a comprehensive hydrologic water quality model typically reserved for use by hydrologists and engineers. This research demonstrates the applicability of existing water quality models in the development of user friendly P management tools.     

A Multilevel Model of the Impact of Farm‐Level Best Management Practices on Phosphorus Runoff1

Abstract: Multilevel or hierarchical models have been applied for a number of years in the social sciences but only relatively recently in the environmental sciences. These models can be developed in either a frequentist or Bayesian context and have similarities to other methods such as empirical Bayes analysis and random coefficients regression. In essence, multilevel models take advantage of the hierarchical structure that exists in many multivariate datasets; for example, water quality measurements may be taken from individual lakes, lakes are located in various climatic zones, lakes may be natural or man‐made, and so on. The groups, or levels, may effectively yield different responses or behaviors (e.g., nutrient load response in lakes) that often make retaining group membership more effective when developing a predictive model than when working with either all of the data together or working separately with the individuals. Here, we develop a multilevel model of the impact of farm level best management practices (BMPs) on phosphorus runoff. The result of this research is a model with parameters which vary with key practice categories and thus may be used to evaluate the effectiveness of these practices on phosphorus runoff. For example, it was found that the effect of fertilizer application rate on farm‐scale phosphorus loss is a function of the application method, the hydrologic soil group, and the land use (crop type). Further, results indicate that the most effective method for controlling fertilizer loss is through soil injection. In summary, the resultant multilevel model can be used to estimate phosphorus loss from farms and hence serve as a useful tool for BMP selection.     

The analysis of monitoring data with the aid of time-series analysis

Methods derived from time-series analysis are proposed for processing monitoring data. The necessity for the use of these methods is demonstrated. In a case study time-series analysis was applied to assess the impact of the closure of the Grevelingen estuary (S. W. Netherlands) in 1971 on a local wintering population of Oystercatchers (Haematopus ostralegus) in the adjacent Oosterschelde estuary.Communication No. 328 of the Delta Institute for Hydrobiological Research.     

Motivated to disengage: The ethical consequences of goal commitment and moral disengagement in goal setting

A growing literature has suggested that high performance goals can have unintended consequences within organizations as employees engage in unethical behavior to achieve outcomes associated with goal attainment. Extending research on the dark side of goal setting, we suggest that high performance goals not only create a desire to achieve a particular outcome but also alter moral reasoning processes related to goal attainment. Integrating goal-setting theory with motivated moral reasoning, we hypothesize an indirect effect of high performance goals on unethical behavior via state moral disengagement. We also examine goal commitment—which tends to amplify the relationship between high goals and performance—as a key boundary condition associated with this indirect effect. We build this conditional indirect effect model across three studies conducted in the field and the laboratory. Our results provide new insight into both when and why high goals can facilitate moral disengagement and unethical behavior within organizations.     

The moderating role of calling in the work–family interface: Buffering and substitution effects on employee satisfaction

This research seeks for improved understanding regarding the interaction of meaningful work and the work–family interface. Existing literature suggests that experiencing a sense of calling toward work makes the work domain particularly salient to employees compared to other life domains. In this article, we draw on this idea, rooted in identity theory, to hypothesize that a sense of calling toward work diminishes the effects of work–family conflict and work–family enrichment on employee's job and life satisfaction. We test these ideas in two studies. First, we surveyed an alumni sample of 598 employees from various jobs, industries, and job levels. Then, in a constructive replication, we surveyed 327 employees using a time-lagged design. Calling was found to significantly buffer the effect of work–family conflict on job satisfaction in Study 2, but not Study 1. Calling did not buffer the effect of conflict on life satisfaction in either study. However, both studies demonstrated that calling attenuated (substituted for) the effect of work–family enrichment on job satisfaction. Study 1 supported the idea that calling attenuates the effect of enrichment on life satisfaction; however, this interactive effect was reversed in Study 2, contrary to expectations. We discuss implications for theory and practice related to callings and career choices, as well as for the role of calling and work identity in the work–family interface.     

Freshwater aquatic macrophytes as heavy metal monitors — the Ottawa River experience

The ability of freshwater aquatic vascular plants to accumulate heavy metals was examined in some detail during a five year study. Differences in uptake rate were found to depend on the species of plant, the seasonal growth rate changes and the metal ion being absorbed. Lead and mercury were concentrated to a greater extent than the lighter nickel and copper. Laboratory experiments were designed to establish uptake rate constants which were used to calculate water concentrations of mercury from the analyses of plant samples from the river. Background levels of mercury in aquatic plants of 35–50 ng g^-1 dry weight corresponded to a water concentration near 15 ng L^-1 of total mercury of which 25–30% was methylmercury. Higher concentrations of mercury in the plants indicated a proportional increase in the mercury level in the water.     

Evidence for biodegradation and volatilisation of dissolved petroleum hydrocarbons during in situ air sparging in large laboratory columns

Laboratory column experiments run for up to 13 days compared air sparging of groundwater contaminated by dissolved petroleum hydrocarbons in sterile and non-sterile aquifer sediments as well as uncontaminated sediments and groundwater. Loss of dissolved BTEX compounds in the contaminated columns was very rapid, occurring through volatilisation. The majority of the dissolved total organic carbon (TOC) persisted for much longer periods however. A direct comparison between losses from sterile and non-sterile columns suggested a negligible contribution of biodegradation to the removal of TOC. This was difficult to confirm through examination of O₂ utilisation because oxidation of a small amount of reduced sulphur in the aquifer materials was the dominant sink for O₂. Despite this, it was possible to conclude that less than 22% of the removal of TOC was through biodegradation during the first three days of air sparging.     

Animal-sediment relations and community analysis of a Florida estuary

Five species assemblages of the intertidal infauna of Old Tampa Bay, Florida, USA are identified. Two assemblages are judged to constitute distinct communities, while a third is shown to be an interdigitation of the two communities. Dominance by on species is the prevalent pattern within the assemblages. Numbers of deposit feeders are found to be inversely correlated to that of filter feeders, and both trophic types are found to be correlated to the sediment parameters of median grain size, sorting and skewness. Three transects with three stations each were established along the south side of Courtney Campbell Causeway in Tampa Bay, Florida. A faunal sample (0.4 m²), a sediment sample, and a water sample were taken at each station in September, December, and March of 1968/1969. Sediment samples were wet-seived. Animal samples were reduced to numbers of organisms and biomass per species. Trellis diagrams and correlation tests were generated. Support is shown for the trophic group-amensalims hypothesis, however, the silt-clay fraction is apparently of lesser importance to deposit feeders in Florida sediments than in Buzzards Bay sediments. An attempt is made to relate an analysis of the optimal grain size for filter feeders to the trophic group-amensalism hypothesis. A view of communities as abstractions from continua is more realistic than communities as discrete units.     

EFFECTS OF TIME STEP SIZE IN IMPLICIT DYNAMIC ROUTING1

ABSTRACT The effects of the size of the Δt time step used in the integration of the implicit difference equations of unsteady open-channel flow are determined for numerous typical hydrographs with durations in the order of days or even weeks. Truncation errors related to the size of the Δt time step cause a numerical distortion (dispersion and attenuation) of the computed transient. The magnitude of the distortion is related directly to the size of the time step, the length of channel reach, and the channel resistance and inversely to the time of rise of the hydrograph. The type of finite difference expression which replaces spatial derivatives and non-derivative terms in the partial differential equations of unsteady flow has an important influence on the magnitude of the numerical distortion, as well as the numerical stability of the implicit difference equations. Time step sizes in the range of 3 to 6 hrs generally tend to minimize the combination of required computation time and numerical distortion of transients having a time of rise of the order of several days.