LeRoy T. Hansen

Nitrogen in Agricultural Systems: Implications for Conservation Policy

Nitrogen is an important agricultural input that is critical for crop production. However, the introduction of large amounts of nitrogen into the environment has a number of undesirable impacts on water, terrestrial, and atmospheric resources. This report explores the use of nitrogen in U.S. agriculture and assesses changes in nutrient management by farmers that may improve nitrogen use effi ciency. It also reviews a number of policy approaches for improving nitrogen management and identifi es issues affecting their potential performance. Findings reveal that about two-thirds of U.S. cropland is not meeting three criteria for good nitrogen management. Several policy approaches, including fi nancial incentives, nitrogen management as a condition of farm program eligibility, and regulation, could induce farmers to improve their nitrogen management and reduce nitrogen losses to the environment.

The Use of Markets to Increase Private Investment in Environmental Stewardship

U.S. farmers and ranchers produce a wide variety of commodities for food, fuel, and fiber in response to market signals. Farms also contain significant amounts of natural resources that can provide a host of environmental services, including cleaner air and water, flood control, and improved wildlife habitat. Environmental services are often valued by society, but because they are a public good—that is, people can obtain them without paying for them—farmers and ranchers may not benefit financially from producing them. As a result, farmers and ranchers under-provide these services. This report explores the use of market mechanisms, such as emissions trading and eco-labels, to increase private investment in environmental stewardship. Such investments could complement or even replace public investments in traditional conservation programs. The report also defines roles for government in the creation and function of markets for environmental services.

Conservation Reserve Program: Environmental Benefits Update

This paper presents the methodology, assumptions, and data used to generate regional and national environmental benefit estimates of the USDAs Conservation Reserve Program (CRP). Its assumed that, without the program, production and conservation practices on CRP lands would be the same as those used on surrounding lands. When range and forest lands are (are not) included as land-use options, 54 (71) percent of the CRP land would be in crop production—which is consistent with past analyses. Soil erosion would be 222 to 248 million tons per year—about 11 percent—higher than the current level. Benefits are estimated by applying environmental benefit models, estimated in previous analyses, to the CRPs estimated effect on erosion and wildlife habitat. Nationally, the CRP is estimated to provide

The Value of the Reservoir Services Gained with Soil Conservation

1.3 billion in annual benefits, which represents 75 to 80 percent of the programs cost. In seven of the 10 USDA Farm Production Regions, the CRPs environmental benefits exceed costs. Thus, reallocating acreage to these regions could increase net program benefits. However, because many benefits could not be estimated, one cannot conclude that regional and national benefits do not exceed costs.

Plasma methionine, choline, betaine, and dimethylglycine in relation to colorectal cancer risk in the European Prospective Investigation into Cancer and Nutrition (EPIC)

To evaluate the impact of soil conservation on reservoir services, we extend replacement cost theory to cases where reservoir benefits are restored or preserved for multiple years. The framework is used to value the effect that a marginal change in soil erosion has on current and future reservoir benefits. Results show that, across the 2,111 U.S watersheds, a one-ton reduction in soil erosion provides benefits ranging from zero to

An Assessment of Re-Directing Breeding Waterfowl Conservation Relative to Predictions of Climate Change

1.38. Furthermore, in a policy application, the lower soil erosion level in 1997, relative to 1982, was shown to have conserved

An epidemiologic risk prediction model for ovarian cancer in Europe: the EPIC study

154 million in reservoir benefits. (JEL Q26, Q51)

Nitrogen fertilizer application timing: A decision theoretic approach for United States cotton

BACKGROUND Disturbances in one carbon metabolism may contribute to carcinogenesis by affecting methylation and synthesis of DNA. Choline and its oxidation product betaine are involved in this metabolism and can serve as alternative methyl group donors when folate status is low. PATIENTS AND METHODS We conducted a case-control study nested within the European Prospective Investigation into Cancer and Nutrition (EPIC), to investigate plasma concentrations of the methyl donors methionine, choline, betaine (trimethylglycine), and dimethylglycine (DMG) in relation to colorectal cancer (CRC) risk. Our study included 1367 incident CRC cases (965 colon and 402 rectum) and 2323 controls matched by gender, age group, and study center. Multivariate-adjusted odds ratios (ORs) and 95% confidence intervals (95% CIs) for CRC risk were estimated by conditional logistic regression, comparing the fifth to the first quintile of plasma concentrations. RESULTS Overall, methionine (OR: 0.79, 95% CI: 0.63-0.99, P-trend = 0.05), choline (OR: 0.77, 95% CI: 0.60-0.99, P-trend = 0.07), and betaine (OR: 0.85, 95% CI: 0.66-1.09, P-trend = 0.06) concentrations were inversely associated with CRC risk of borderline significance. In participants with folate concentration below the median of 11.3 nmol/l, high betaine concentration was associated with reduced CRC risk (OR: 0.71, 95% CI: 0.50-1.00, P-trend = 0.02), which was not observed for those having a higher folate status. Among women, but not men, high choline concentration was associated with decreased CRC risk (OR: 0.62, 95% CI: 0.43-0.88, P-trend = 0.01). Plasma DMG was not associated with CRC risk. CONCLUSIONS Individuals with high plasma concentrations of methionine, choline, and betaine may be at reduced risk of CRC.

THE APPLICATION TIMING OF NITROGEN FERTILIZER

Abstract The U.S. Fish and Wildlife Service has a long history of habitat conservation in the Prairie Pothole Region (PPR) of the United States that has focused on migratory birds, particularly wat...

Cash or Credit? Tax Credits and Conservation Outcomes

Background:Ovarian cancer has a high case-fatality ratio, largely due to late diagnosis. Epidemiologic risk prediction models could help identify women at increased risk who may benefit from targeted prevention measures, such as screening or chemopreventive agents.Methods:We built an ovarian cancer risk prediction model with epidemiologic risk factors from 202 206 women in the European Prospective Investigation into Cancer and Nutrition study.Results:Older age at menopause, longer duration of hormone replacement therapy, and higher body mass index were included as increasing ovarian cancer risk, whereas unilateral ovariectomy, longer duration of oral contraceptive use, and higher number of full-term pregnancies were decreasing risk. The discriminatory power (overall concordance index) of this model, as examined with five-fold cross-validation, was 0.64 (95% confidence interval (CI): 0.57, 0.70). The ratio of the expected to observed number of ovarian cancer cases occurring in the first 5 years of follow-up was 0.90 (293 out of 324, 95% CI: 0.81–1.01), in general there was no evidence for miscalibration.Conclusion:Our ovarian cancer risk model containing only epidemiological data showed modest discriminatory power for a Western European population. Future studies should consider adding informative biomarkers to possibly improve the predictive ability of the model.