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Scientific Investigations Report 2012-5207

National Water-Quality Assessment Program

County-Level Estimates of Nitrogen and Phosphorus from Commercial Fertilizer for the Conterminous United States, 1987–2006

By Jo Ann M. Gronberg and Norman E. Spahr

Abstract

The U.S. Geological Survey’s National Water-Quality Assessment program requires nutrient input for analysis of the national and regional assessment of water quality. Detailed information on nutrient inputs to the environment are needed to understand and address the many serious problems that arise from excess nutrients in the streams and groundwater of the Nation. This report updates estimated county-level farm and nonfarm nitrogen and phosphorus input from commercial fertilizer sales for the conterminous United States for 1987 through 2006. Estimates were calculated from the Association of American Plant Food Control Officials fertilizer sales data, Census of Agriculture fertilizer expenditures, and U.S. Census Bureau county population. A previous national approach for deriving farm and nonfarm fertilizer nutrient estimates was evaluated, and a revised method for selecting representative states to calculate national farm and nonfarm proportions was developed. A national approach was used to estimate farm and nonfarm fertilizer inputs because not all states distinguish between farm and nonfarm use, and the quality of fertilizer reporting varies from year to year. For states that distinguish between farm and nonfarm use, the spatial distribution of the ratios of nonfarm-to-total fertilizer estimates for nitrogen and phosphorus calculated using the national-based farm and nonfarm proportions were similar to the spatial distribution of the ratios generated using state-based farm and nonfarm proportions. In addition, the relative highs and lows in the temporal distribution of farm and nonfarm nitrogen and phosphorus input at the state level were maintained—the periods of high and low usage coincide between national- and state-based values. With a few exceptions, nonfarm nitrogen estimates were found to be reasonable when compared to the amounts that would result if the lawn application rates recommended by state and university agricultural agencies were used. Also, states with higher nonfarm-to-total fertilizer ratios for nitrogen and phosphorus tended to have higher urban land-use percentages.

First posted November 19, 2012

For additional information contact:
Director, California Water Science Center
U.S. Geological Survey
6000 J Street, Placer Hall
Sacramento, California 95819
http://ca.water.usgs.gov

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Suggested citation:

Gronberg, J.M., and Spahr, N.E., 2012, County-level estimates of nitrogen and phosphorus from commercial fertilizer for the Conterminous United States, 1987–2006: U.S. Geological Survey Scientific Investigations Report 2012-5207, 20 p.



Contents

Forward

Abstract

Introduction

Purpose and Scope

Description of the Association of American Plant Food Control Officials Fertilizer Sales Data

Estimation of State-Level Farm and Nonfarm Portions of Fertilizer Sales

Distribution to the County Level

Description of the County-Level Fertilizer Nutrient-Input Dataset

Evaluation of the Farm and Nonfarm Fertilizer Data

Summary

References Cited

Appendix 1. Total Number of Fertilizer Products and Number of Nonfarm Fertilizer Products Summarized from the Association of American Plant Food Control Officials Data, by State, 1987–2006

Appendix 2. Product Tonnage as Reported in Raw Association of American Plant Food Control Officials Data, by State, 1987–2006

Appendix 3. Location of States With at Least One Year (1987–2006) of Association of American Plant Food Control Officials (AAPFCO) Fertilizer Product Tonnage Data Estimated from Previous Years or from Surrounding States, and Summary of States and Years with Estimated AAPFCO Fertilizer Product Tonnage Data, 1987–2006

Appendix 4. Location of Counties with Association of American Plant Food Control Officials Fertilizer Product Tonnage data Reported at the County Level, 1987–2006

Appendix 5. Farm and Nonfarm Nitrogen and Phosphate Tonnage, by State, 1987–2006

Appendix 6. Nitrogen and Phosphorus Tonnage Based on National and State Farm and Nonfarm Proportions, by State, 1987–2006


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