Nutrient management programs, nitrogen fertilizer practices, and groundwater quality in Nebraska's Central Platte Valley (U.S.), 1989-1998.

Given the societal concern about groundwater pollution from agricultural sources, public programs have been proposed or implemented to change farmer behavior with respect to nutrient use and management. However, few of these programs designed to change farmer behavior have been evaluated due to the lack of detailed data over an appropriate time frame. The Central Platte Natural Resources District (CPNRD) in Nebraska has identified an intensively cultivated, irrigated area with average groundwater nitrate-nitrogen (N) levels about double the EPA"s safe drinking water standard. The CPNRD implemented a joint education and regulatory N management program in the mid-1980s to reduce groundwater N. This analysis reports N use and management, yield, and groundwater nitrate trends in the CPNRD for nearly 3000 continuous-corn fields from 1989 to 1998, where producers faced limits on the timing of N fertilizer application but no limits on amounts. Groundwater nitrate levels showed modest improvement over the 10 years of this analysis, falling from the 1989-1993 average of 18.9 to 18.1 mg/l during 1994-1998. The availability of N in excess of crop needs was clearly documented by the CPNRD data and was related to optimistic yield goals, irrigation water use above expected levels, and lack of adherence to commercial fertilizer application guidelines. Over the 10-year period of this analysis, producers reported harvesting an annual average of 9729 kg/ha, 1569 kg/ha (14%) below the average yield goal. During 1989-1998, producers reported annually applying an average of 162.5 kg/ha of commercial N fertilizer, 15.7 kg/ha (10%) above the guideline level. Including the N contribution from irrigation water, the potential N contribution to the environment (total N available less estimated crop use) was estimated at 71.7 kg/ha. This is an estimate of the nitrates available for denitrification, volatilization, runoff, future soil N, and leaching to groundwater. On average, between 1989-1993 and 1994-1998, producers more closely followed CPNRD N fertilizer recommendations and increased their use of postemerge N applications--an indication of improved synchrony between N availability and crop uptake.

Alternative measures of pesticide use.

One kilogram of a pesticide is not necessarily equal to a kilogram of a different pesticide. This issue can be significant. Whether it is depends on the use to which pesticide-use data are put. While kilograms of pesticide is the most common way of measuring agricultural chemical use, the type of analysis will generally define what measure of chemical use is best. Quantifying the risk from the exposure to pesticides, for example, typically requires weighing usage or residues by acute or chronic health and environmental toxicity coefficients and subsequently estimating human or environmental exposure to such hazards. The interferences one draws concerning pesticide use can vary substantially depending on the measure considered.

Location and cost of ambulances serving a rural area.

A location model is used to determine the most efficient (i.e., least-cost) number and location of ambulance facilities in a rural area. The model incorporates response time and service time standards into the analysis and indicates the trade-off between costs and various time standards. The financial feasibility of individual facility locations is then analyzed. The results indicate why many rural areas depend on volunteer or part-time purveyors of emergency medical transportation.