Nitrogen fertilizers have vastly improved the productive capacity of agricultural systems in the past century. Some of the synthetic nitrogen is taken up by crops, increasing growth and yield. The nitrogen that is not utilized by plants, however, causes untold problems:
- Chemically destroying organic matter in the soil.
- Seeping into waterways; creating algal blooms and oxygen-depleted oceanic dead zones; and causing major fish kills.
- Causing global warming, as soil bacteria convert nitrate fertilizers into nitrous oxide—298 times more powerful than carbon dioxide in its warming effect.
Nitrogen can be more efficiently managed to reduce these effects by attending to the Four R’s:
- Right source: matching fertilizer choices with plant needs.
- Right time and right place: managing fertilizer applications to deliver nitrogen when and where crop demand is highest.
- Right rate: ending over-application of fertilizer as “insurance.”
Implementation of this solution is simple: It requires farmers to moderately reduce their inputs rather than undertake a new practice or install a new technology. Education, assistance, incentives, and regulation can accelerate adoption. The true solution to nutrient management, however, is rotational, regenerative land practices that eliminate most, if not all, need for synthetic nitrogen.
free, reactive nitrogen: Robertson, G. Philip, and Peter M. Vitousek. “Nitrogen in Agriculture: Balancing the Cost of an Essential Resource.” Annual Review of Environment and Resources 34, no. 1 (October 15, 2009): 97–125.
oceanic dead zones: UNEP. “Excess Nitrogen in the Environment.” In UNEP Year Book 2014: Emerging Issues in Our Global Environment, 6-11. Nairobi: United Nations Environment Programme.
Nitrous oxide…[vs.] carbon dioxide: Myhre, Gunnar, Drew Shindell, François-Marie Bréon, William Collins, Jan Fuglestvedt, Jianping Huang, Dorothy Koch et al. “Anthropogenic and natural radiative forcing.” In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK, and New York: Cambridge University Press, 2013.
the four Rs: Ehmke, Tanner. “The 4 Rs of Nutrient Management.” Crops and Soils Magazine. September-October 2012.
Right source: Venterea, Rodney T., Maharjan Bijesh, and Michael S. Dolan. “Fertilizer Source and Tillage Effects on Yield-Scaled Nitrous Oxide Emissions in a Corn Cropping System.” Journal of Environment Quality 40, no. 5 (2011): 1521.
Right time and right place: Drury, C. F., W. D. Reynolds, X. M. Yang, N. B. McLaughlin, T. W. Welacky, W. Calder, and C. A. Grant. “Nitrogen Source, Application Time, and Tillage Effects on Soil Nitrous Oxide Emissions and Corn Grain Yields.” Soil Science Society of America Journal 76, no. 4 (2012): 1268; Zebarth, B. J., P. Rochette, D. L. Burton, and M. Price. “Effect of Fertilizer Nitrogen Management on nitrogen oxide Emissions in Commercial Corn Fields.” Canadian Journal of Soil Science 88, no. 2 (2008): 189–95.
right rate: Robertson and Vitousek, “Nitrogen.”
how producers make decisions: Stuart, D., R. L. Schewe, and M. McDermott. “Reducing Nitrogen Fertilizer Application as a Climate Change Mitigation Strategy: Understanding Farmer Decision-Making and Potential Barriers to Change in the US.” Land Use Policy 36 (January 2014): 210–18.
incentives and educational programs: Napier, T L, and T. Bridges. “Adoption of Conservation Production Systems in Two Ohio Watersheds: A Comparative Study.” Journal of Soil and Water Conservation 57, no. 4 (2002): 229–35.
carbon-offset methodology: American Carbon Registry. “Reduced Use of Nitrogen Fertilizer.” http://americancarbonregistry.org/resources/reduced-use-of-nitrogen-fertilizer; Millar, Neville, G. Philip Robertson, Peter R. Grace, Ron J. Gehl, and John P. Hoben. “Nitrogen Fertilizer Management for Nitrous Oxide (N2O) Mitigation in Intensive Corn (Maize) Production: An Emissions Reduction Protocol for.” Mitigation and Adaptation Strategies for Global Change 15, no. 2 (2010): 185–204.
Vermont…nutrient-management plans: Vermont Agency of Agriculture, Food, and Markets. “Nutrient Management Planning and Land Treatment Planning.” http://agriculture.vermont.gov/water-quality/farmer-assistance/nmp-ltp.
United Kingdom…Nitrate Vulnerable Zones: Department for Environment, Food, and Rural Affairs and Environment Agency. “Nutrient Management: Nitrate Vulnerable Zones.” https://www.gov.uk/guidance/nutrient-management-nitrate-vulnerable-zones.
close yield gaps and ensure adequate supply: Licker, Rachel, Matt Johnston, Jonathan A. Foley, Carol Barford, Christopher J. Kucharik, Chad Monfreda, and Navin Ramankutty. “Mind the Gap: How Do Climate and Agricultural Management Explain the ‘Yield Gap’ of Croplands around the World?” Global Ecology and Biogeography 19, no. 6 (2010): 769–82.
Nitrates Directive; Denmark and the Netherlands: UNEP, “Nitrogen.”
data on fertilizer consumption: FAOSTAT. “Fertilizers.” http://faostat.fao.org/beta/en/#data/RF/visualize.
[impact of] 20 percent improvement: UNEP, “Nitrogen.”
Correction: The United Nations Environment Programme estimates that a 20 percent improvement in nutrient use would eliminate more than 20 million tons of nitrogen fertilizer and produce potential savings of $50 billion to $400 billion.