Growth and consolidation in the livestock industry in the past 30 years have resulted in more total farm animals being raised on fewer Iowa farms. The effects of this on stream water quality at the landscape scale have largely gone unexplored. The main objective of this work was to quantify the effects on stream nitrate levels of livestock concentration in two western Iowa watersheds relative to seven other nearby watersheds. To achieve this objective, we used data on high-frequency nitrate concentration and stream discharge, commercial nitrogen fertilizer use, and manure-generated nitrogen in each watershed. Our analysis shows much higher stream nitrate in the two watersheds where livestock concentration has been greatest, and little difference in commercial fertilizer inputs with the widespread availability of manure N. Reducing N inputs and better management of manure N, including analysis of crop N availability in soil and manure, can reduce uncertainty regarding fertilization while improving water quality.
KeywordsConcentrated livestock Commercial fertilizer Flow weighted average Manure Nitrate-nitrogen
This publication was prepared by the authors with funds from the Iowa Nutrient Research Center. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the Iowa Nutrient Research Center or Iowa State University. The authors thank Dan Gilles for graphics assistance.
- Commoner, B. 1977. Cost-Risk-Benefit Analysis of Nitrogen Fertilization: A Case History. Ambio 6: 157–161.Google Scholar
- Gronberg, J.M., and N.E. Spahr. 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. https://pubs.usgs.gov/sir/2012/5207/.
- Gronberg, J.M., and T.L. Arnold. 2017. County-level estimates of nitrogen and phosphorus from animal manure for the conterminous United States, 2007 and 2012, U.S. Geological Survey Open-File Report 2017-1021, https://doi.org/10.3133/ofr20171021.
- Honeyman, M.S., and M.D. Duffy. 2006. Iowa’s Changing Swine Industry. Animal Industry Report 652: 64.Google Scholar
- IAC (Iowa Administrative Code) 2018. Chapter 65.1. https://www.legis.iowa.gov/docs/iac/rule/11-09-2016.567.65.1.pdf.
- IDNR, Iowa Department of Natural Resources, 2018a. Iowa DNR Animal Feeding Operation Database. https://programs.iowadnr.gov/animalfeedingoperations/.
- Iowa DNR, Iowa Department of Natural Resources 2018b. Iowa’s Ambient Water Quality Monitoring and Assessment Program. http://www.iowadnr.gov/Environmental-Protection/Water-Quality/Water-Monitoring.
- Iowa Nutrient Reduction Strategy. 2013. A Science‐and Technology‐Based Framework to Assess and Reduce Nutrients to Iowa Waters and the Gulf of Mexico. http://publications.iowa.gov/23225/.
- Iowa State University, College of Agriculture, Department of Agronomy. 2017. Iowa Environmental Mesonet, IEM Climodat Reports. From: http://mesonet.agron.iastate.edu/climodat/index.phtml.
- Jackson, L.L., D.R. Keeney, and E.M. Gilbert. 2000. Swine Manure Management Plans in North-central Iowa: Nutrient Loading and Policy Implications. Journal of Soil and Water Conservation 55: 205–212.Google Scholar
- Klepper, R., 1974. Fertilizer application rates and nitrate concentrations in Illinois surface waters. National Agricultural Library. http://agris.fao.org/agris-search/search.do?recordID=US201300533223.
- Letson, D., N. Gollehon, C. Kascak, V. Breneman, and C. Mose. 1998. Confined Animal Production and Groundwater Protection. Review of Agricultural Economics 20: 348–364.Google Scholar
- Libra, R.D., C.F. Wolter, and R.J. Langel. 2004. Nitrogen and phosphorus budgets for Iowa and Iowa watersheds. https://ir.uiowa.edu/cgi/viewcontent.cgi?article=1046&context=igs_tis.
- MPCA, Minnesota Pollution Control Agency, Environmental Data Access. 2018. https://cf.pca.state.mn.us/eda/stationInfo.php?ID=S000-687&ORG=MNPCA&wdip=2.
- Sawyer, J.E., 2016. Iowa State University, Extension and Outreach Publications 5-2016. Nitrogen use in Iowa corn production. https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1081&context=extension_pubs.
- USDA, 2009. Natural Resources Conservation Service, Crop Nutrient Tool, Plants Database. A tool for calculating the approximate amount of nitrogen, phosphorus, and potassium that is removed by the harvest of agricultural crops. https://plants.usda.gov/npk/main.
- USDA. National agricultural statistics service quick stats. 2018. https://quickstats.nass.usda.gov/.
- USGS, 2018. National Water Information System, Web Interface, Current Conditions for Iowa: Streamflow. https://waterdata.usgs.gov/ia/nwis/current/?type=flow.
- Yadav, S.N., W. Peterson, and K.W. Easter. 1997. Do Farmers Overuse Nitrogen Fertilizer to the Detriment of the Environment? Environmental & Resource Economics 93: 323–340.Google Scholar