Clarifying the definition ofSustainable agriculture

A number of distinct definitions ofsustainable agriculture have been proposed. In this paper we criticize two such definitions, primarily for conflating sustainability with other objectives such as economic viability and ecological integrity. Finally, we propose and defend a definition which avoids our objections to the other definitions.     

Attributional conflict between managers and subordinates: An investigation of leader-member exchange effects

The present study investigated the discrepancies, or conflict, between the attributions of leaders and members as a function of LMX quality and explored the relation between attributional conflict and subordinate job satisfaction, perceptions of equity, and turnover intentions. Data for the study were provided by 141 supervisor-subordinate dyads from the managerial ranks of a large manufacturing organization. Both parties of the dyad made attributions for subordinate loyalty, affect, and contributions, member behaviors identified as critical in previous LMX research. Limited support emerged for the hypothesis that attributional conflict would be greater in dyads where subordinates reported lower rather than higher LMX quality. Findings suggested that attributional discrepencies are due, in part, to the tendency of leaders to make more favorable attributions for subordinates reporting higher LMX quality than for subordinates reporting lower LMX quality. Results also revealed that, while attributional conflict was negatively related to subordinate satisfaction and perceptions of equity and positively related to turnover intentions, attributional conflict did not predict subordinate work outcomes when the effects of LMX quality were controlled. Implications of these findings were discussed.     

Legal implications in development and use of Expert Systems in agriculture

Applications of Artificial Intelligence, particularly Expert Systems, are rapidly increasing. This science promises to give computer-based systems the capability of reasoning and decision making in near human-like fashion. Whether used for farm management or intelligent machine control, Expert Systems will find many agricultural applications. Much of the development and distribution of such systems will probably take place in the public sector, particularly the Cooperative Extension Service. A major nontechnical factor affecting the development and extensive use of Expert Systems is the legal issue of products, liability, and negligence. The legal issues surrounding Expert Systems have not yet been fully tested and defined by the courts. Developers and users of Expert Systems must consider these factors for each particular application.     

Modeling natural attenuation of petroleum hydrocarbon contamination using alternate electron acceptors: Case study comparing bioplume iii with BIOSCREEN

Natural attenuation holds great promise as a cost‐effective means of remedying groundwater contamination at petroleum spill sites: this is particularly true at sites with sufficient background concentrations of alternate electron acceptors (nitrate and/or sulfate). The study reported in this article compared the results of a new Environmental Protection Agency (EPA) numerical model (BIOPLUME III) with an updated EPA analytical model (BIOSCREEN Version 1.4) used to predict natural attenuation at an underground fuel spill site in Oklahoma. High background sulfate concentrations were shown to result in unrealistic predictions from both BIOSCREEN and BIOPLUME III. BIOSCREEN could be easily used with a data set not significantly enlarged from that used in a routine leaking fuel tank investigation. BIOPLUME III was much more difficult to use and did not yield reliable results. Results of this study indicate that the additional complexity of the BIOPLUME III model is not justified for simple sites.     

APPLICATION OF THE BASINS DATABASE AND NPSM MODEL ON A SMALL OHIO WATERSHED1

ABSTRACT: The purpose of this study was to evaluate the Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) watershed management system. BASINS data were used with the NPSM model to predict discharge and sediment concentrations at the outlet of a 103 km² Ohio watershed. It was concluded that the NPSM model should always be calibrated but only a few of the parameters provided with BASINS needed to be calibrated. For a three‐year study period, there was a 2 percent underestimation of discharge using area weighted precipitation values and a 25 percent overestimation using the single station data in BASINS. A comparison of observed and predicted monthly discharge resulted in an r² of 0.86 with area‐weighted precipitation and an r² of 0.74 with the single station data. Calibrating the model to substantially improve sediment predictions was unsuccessful and we concluded that a calibration period of one year was too short. For the three‐year study period, the r² for sediment was 0.36 with a slope of 0.37 and an intercept of 18.8 mg/l. The mean observed and predicted sediment concentrations were 27.1 mg/l and 22.6 mg/l, respectively.     

Using urban man-made ponds to reconstruct a 150-year history of air pollution in northwest England

A regional pollution history has been reconstructed for the borough of Halton (northwest England) from four urban ponds in north Cheshire and south Merseyside, using environmental analyses of lake sediment stratigraphies. Mineral magnetism, geochemistry and radiometric dating have produced profiles of pollution characteristics dating from the mid-nineteenth century to present day. These pollution profiles reflect the atmospheric deposition of a range of pollutants over 150 years of intensified industry. Distinct phases of pollution deposition and characteristics are identified reflecting: (1) intensification of industry in the nineteenth century; (2) expansion of industry during the twentieth century; (3) post 1956 Clean Air Acts. This work promotes the potential use of these pollution archives for use in epidemiology to better understand links between human health and environmental pollution, especially for diseases with long latency times, where retrospective pollution exposure assessments are important.     

Assessment of Benthic Infaunal Condition on the Mainland Shelf of Southern California

Benthic infauna were sampled from 251 Southern California Bight (SCB) mainland shelf sites in the summer of 1994. Sample sites were selected using a stratified random design, with the primary strata being depth zone, geography, and proximity to point and non-point discharges. Benthic infaunal condition was assessed using the Benthic Response Index (BRI), and by comparing dominant taxa and community parameters (e.g., number of taxa) among strata. Ninety-one percent of sediments in the SCB were found to contain healthy benthic communities. Most stations with altered benthos were located near river mouths, in Santa Monica Bay, or on the Palos Verdes Shelf. Deviations at sites with altered benthic communities were mostly limited to minor changes in species composition, rather than to large declines in diversity or abundance.     

Integration of SWAT and HSPF for Simulation of Sediment Sources in Legacy Sediment‐Impacted Agricultural Watersheds

A total maximum daily load for the Chesapeake Bay requires reduction in pollutant load from sources within the Bay watersheds. The Conestoga River watershed has been identified as a major source of sediment load to the Bay. Upland loads of sediment from agriculture are a concern; however, a large proportion of the sediment load in the Conestoga River has been linked to scour of legacy sediment associated with historic millpond sites. Clarifying this distinction and identifying specific segments associated with upland vs. channel sources has important implications for future management. In order to address this important question, we combined the strengths of two widely accepted watershed management models — Soil and Water Assessment Tool (SWAT) for upland agricultural processes, and Hydrologic Simulation Program FORTRAN (HSPF) for instream fate and transport — to create a novel linked modeling system to predict sediment loading from critical sources in the watershed including upland and channel sources, and to aid in targeted implementation of management practices. The model indicates approximately 66% of the total sediment load is derived from instream sources, in agreement with other studies in the region and can be used to support identification of these channel source segments vs. upland source segments, further improving targeted management. The innovated linked SWAT‐HSPF model implemented in this study is useful for other watersheds where both upland agriculture and instream processes are important sources of sediment load.