Technical Summary

Nutrient Management

Project Drawdown defines nutrient management as fertilizer application practices that use right source, right rate, right time and right placement principles. These principles are important for both countries where fertilizer consumption is high and nitrogen use efficiency low (e.g., United States, China) as well as in countries where substantial increases in nutrient inputs on cropland is needed (Sub-Saharan Africa).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.

Methodology

Total Land Area[1]

Total available land for nutrient management is 1,411 million hectares (essentially all annual and perennial cropland).[2] Current adoption[3] is estimated at 139.1 million hectares. In the absence of data on current adoption of nutrient management, this figure is based on current adoption for conservation agriculture and areas that achieved 70% of nutrient use efficiency (NUE).. National level NUE for 124 countries from 1961-2009 (Lassetta et al, 2014) were combined with total cropland area available at UN Food and Agriculture Organization (2011). Only countries that have NUE in 70-80% range were considered in estimates of cropland that adopt nutrient management practices. Our estimates show that in 1990 total cropland area with NUE (70-80%) was 70 Mha while in 2009 total area was 101 Mha. We used aspirational goal defined for 2020 defined in the report Our Nutrient World that result in 336 Mha.

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 estimates available on regional and country level estimates on NUE.

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

  • Scenario 1: The conservative adoption scenarios resulted in the adoption of nutrient management on 380.3million hectares of the total cropland area.
  • Scenario 2: In this scenario, the adoption increases aggressively and reaches 816.7  million hectares.

Emissions Model

Emissions reduction is 0.49 (based on 20 data points from 14 sources) tons of carbon dioxide per hectare per year and 0.44 (based on 65 data points from 17 sources) tons of nitrous oxide carbon dioxide-equivalent per hectare per year based on the difference of per hectare application of nutrients in the conventional practices compare to the solution.

Financial Model

First cost of nutrient management is $0 per hectare,[5] as reducing the over-application of fertilizer costs farmers nothing. Operational cost is US$19.86 per hectare per year (savings in fertilizer cost), , compare to the operational cost of US$23.06 per hectare per year for the conventional practice, 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 Scenario 1 is 380.3 million hectares in 2050, representing 27 percent of the total suitable land. Of this, 241.15 million hectares are adopted from 2020-2050. The emissions impact of this scenario is 2.34 gigatons of carbon dioxide-equivalent by 2050. Net cost is US$0. Net savings in lifetime operational cost is US$23.03billion.

Total adoption in the Scenario 2 is 816.7 million hectares in 2050, representing 58 percent of the total suitable land. Of this, 677.54 million hectares are adopted from 2020-2050. The impact of this scenario is 12.06  gigatons of carbon dioxide-equivalent by 2050. Net cost is US$0. Net savings in lifetime operational cost is US$70.79 billion.

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 0.9 to 1.84 million metric tons of carbon dioxide-equivalent per year by 2030 (Smith, 2007, Table 8.6). Griscom et al (2017)’s “Natural climate solutions” calculate 0.63-0.71 gigatons of carbon dioxide equivalent per year in 2030, based on a higher percentage reduction of fertilizer use than that used by Drawdown. Though this is not a precise benchmark, the Drawdown model calculates 0.01-0.33 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 2018 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.