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Credit: Andre Maslennikov

Food

Nutrient Management

Algal bloom off the coast of Sweden in the Baltic Sea.

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.

References

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.”

view all book references

Errata

p. 57

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.

view all errata

Technical Summary

Nutrient Management

Project Drawdown defines nutrient management as: reducing fertilizer waste and increasing efficiency to reduce nitrous oxide emissions associated with agriculture. This solution replaces conventional fertilizer use on cropland, and assumes that farmers reduce fertilizer use by 10 percent.

Nitrogen fertilizers have greatly increased agricultural production over the past century. But the application of fertilizers to soil can lead to emissions of nitrous oxide, a potent greenhouse gas, as fertilizer that is not used by plants is utilized by denitrifiying bacteria that release nitrous oxide as a metabolic byproduct. Fertilizer is routinely over-applied in many countries. Furthermore, since the production of fertilizer is an energy-intensive process that produces high amounts of carbon dioxide emissions, reducing fertilizer application will also have the effect of abating emissions associated with its production.

This solution has a modest impact, but asks of farmers only that they save money by reducing the over-application of fertilizer. It reduces the emissions of a powerful greenhouse gas and improves water quality by cleaning up runoff from farms.

Methodology

Total Land Area [1]

Total available land for nutrient management is 1,473 million hectares (essentially all annual and perennial cropland). [2] Current adoption [3] is estimated at 71.7 million hectares. In the absence of data on current adoption of nutrient management, this figure is based on current adoption for conservation agriculture, as it is assumed that both strategies are likely to appeal to mechanized farmers.

Adoption Scenarios [4]

Future adoption projections for nutrient management used the same scenarios as conservation agriculture (again assuming a link between these two solutions), and applied to the total available land of 1,473 million hectares.

Impacts of increased adoption of nutrient management from 2020-2050 were generated based on three growth scenarios, which were assessed in comparison to a Reference Scenario where the solution’s market share was fixed at the current levels.

  • Plausible Scenario: The conservative adoption scenarios resulted in the adoption of nutrient management on 821 million hectares of the total cropland area.
  • Drawdown Scenario: In this scenario, the adoption increases aggressively and reaches 893 million hectares.
  • Optimum Scenario: In this scenario, the adoption increases most aggressively and reaches 1,209 million hectares.

Emissions Model

Emissions reduction is 0.08 tons of carbon dioxide-equivalent per hectare per year in reduced emissions from the manufacture of nitrogen fertilizers. An additional reduction of 0.06 tons of carbon dioxide-equivalent per hectare per year comes from reduced nitrous oxide from fertilizer manufacture and over-application. Both figures are based on meta-analysis of 78 data points from 74 sources.

Financial Model

First cost of nutrient management is $0 per hectare, [5] as reducing the over-application of fertilizer costs farmers nothing. Net profit margin is US$7.48 per hectare per year (savings in fertilizer cost), based on 5 regional data points from the Food and Agriculture Organization (FAO)’s Statistical Service (2017).

Integration [6]

Drawdown’s Agro-Ecological Zone model allocates current and projected adoption of solutions to the planet’s forest, grassland, rainfed cropland, and irrigated cropland areas. In the case of nutrient management, all cropland is suitable, and it was determined that nutrient management can occur on land with other solutions implemented (e.g. conservation agriculture), as the reduced emissions operate independently from biosequestration and other Drawdown agricultural solutions.

Results

Total adoption in the Plausible Scenario is 821.1 million hectares in 2050, representing 55.7 percent of the total suitable land. Of this, 749.4 million hectares are adopted from 2020-2050. The emissions impact of this scenario is 1.8 gigatons of carbon dioxide-equivalent by 2050. Net cost is US$0. Net savings is US$102.3 billion.

Total adoption in the Drawdown scenario is 892.9 million hectares in 2050, representing 60.6 percent of the total suitable land. Of this, 821.2 million hectares are adopted from 2020-2050. The impact of this scenario is 1.9 gigatons of carbon dioxide-equivalent by 2050.

Total adoption in the Optimum scenario is 1,208.8 million hectares in 2050, representing 82.0 percent of the total suitable land. Of this, 1,137.1 million hectares are adopted from 2020-2050. The impact of this scenario is 2.7 gigatons of carbon dioxide-equivalent by 2050.

Discussion

Benchmarks

The Intergovernmental Panel on Climate Change (IPCC) reports that the emissions reduction from all agricultural nitrous oxide (including fertilizers, manure, and other sources) is projected to be 89 to 1,844 million metric tons of carbon dioxide-equivalent per year by 2030 (Smith, 2007, Table 8.6). Though this is not a precise benchmark, the Drawdown model calculates 50-80 gigatons of carbon dioxide-equivalent per year in 2030 from nitrogen fertilizer alone, not including manure and other nitrous oxide sources.

Limitations

This study could be improved should better data on current adoption of nutrient management become available.

Conclusions

This is a solution that should be adopted regardless of its mitigation impact. It saves farmers money and reduces water pollution. That it reduces emissions of a powerful greenhouse gas, and emissions associated with producing that gas, makes this a clear win-win solution.


[1] To learn more about the Total Land Area for the Food Sector, click the Sector Summary: Food link below.

[2] Determining the total available land for a solution is a two-part process. The technical potential is based on the suitability of climate, soils, and slopes, and on degraded or non-degraded status. In the second stage, land is allocated using the Drawdown Agro-Ecological Zone model, based on priorities for each class of land. The total land allocated for each solution is capped at the solution’s maximum adoption in the Optimum Scenario. Thus, in most cases the total available land is less than the technical potential.

[3] Current adoption is defined as the amount of functional demand supplied by the solution in the base year of study. This study uses 2014 as the base year due to the availability of global adoption data for all Project Drawdown solutions evaluated.

[4] To learn more about Project Drawdown’s three growth scenarios, click the Scenarios link below. For information on Land Use Sector-specific scenarios, click the Sector Summary: Food link.

[5] All monetary values are presented in US2014$.

[6] For more on Project Drawdown’s Food Sector integration model, click the Sector Summary: Food link below.

Full models and technical reports coming in late 2017.

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