Plows are absent on farms practicing conservation agriculture, and for good reason. When farmers till their fields to destroy weeds and fold in fertilizer, water in the freshly turned soil evaporates. Soil itself can be blown or washed away and carbon held within it released into the atmosphere. Tilling can make a field nutrient poor and less life-giving.
Conservation agriculture was developed in Brazil and Argentina in the 1970s, and adheres to three core principles:
- Minimize soil disturbance: absent tilling, farmers seed directly into the soil.
- Maintain soil cover: farmers leave crop residues after harvesting or grow cover crops.
- Manage crop rotation: farmers change what is grown and where.
The Latin root of conserve means “to keep together.” Conservation agriculture abides by these principles to keep the soil together as a living ecosystem that enables food production and helps redress climate change.
Conservation agriculture sequesters a relatively small amount of carbon—an average of half a ton per acre. But given the prevalence of annual cropping around the world, those tons add up. Because conservation agriculture makes land more resilient to climate-related events such as long droughts and heavy downpours, it is doubly valuable in a warming world.
Brazil and Argentina in the 1970s: Farooq, M., and K. Siddique. “Conservation Agriculture: Concepts, Brief History, and Impacts on Agricultural Systems.” In Conservation Agriculture, 3–20. New York: Springer, 2015.
Annual crops…89 percent of…cropland: Toensmeier, Eric. The Carbon Farming Solution. White River Junction, VT: Chelsea Green Publishing, 2016; FAO Statistical Services online.
Conservation agriculture…acres: Friedrich, Theodor, Rolf Derpsch, and Amir Kassam. “Overview of the Global Spread of Conservation Agriculture.” Field Actions Science Reports, Special Issue 6 (2012); Toensmeier, Solution; FAO Statistical Services online.
South America, North America, Australia, and New Zealand: Friedrich et al, “Overview.”
half a ton [of carbon] per acre: Toensmeier, Solution.
Correction: Conservation agriculture sequesters a relatively small amount of carbon—an average of half a ton per acre.
Project Drawdown defines conservation agriculture as: an annual crop production system that provides biosequestration via crop rotation, cover cropping, and reduced tillage. This solution replaces conventional annual cropping systems with tillage.
The three components of conservation agriculture are: minimal soil disturbance (no-till or reduced tillage), permanent soil cover (cover crops), and diversified crop rotations. It is suited to both mechanized and unmechanized contexts. Climate mitigation from conservation agriculture is through reduced emissions from tillage and soil carbon sequestration.
Conservation agriculture is modeled as a bridge technology, which transitions to regenerative agriculture over time. Converting from conservation agriculture to regenerative agriculture only requires the addition of one more practice (compost application, organic farming, or green manure use). The soil health movement, the International Federation of Organic Movements’ “Organic 3.0”, and the many farmers working to implement organic no-till agriculture are all evidence that this transition is underway.
Total Land Area 
The total land area allocated to conservation agriculture and regenerative agriculture is the same: 788 million hectares of non-degraded croplands with minimal slopes, which is allocated differently under different custom adoption scenarios. In all scenarios, conservation agriculture grows until at least 2030 and then starts declining, but never shrinks below its 2014 rate of 71.7 million hectares.
Adoption Scenarios 
Five custom adoption scenarios were developed for conservation agriculture. All begin with current adoption  of 71.7 million hectares. Some scenarios use the current global adoption rate of 0.24 percent, while others use 1.24 percent, which is the rate from South America, the highest regional rate. The conservative scenarios assume adoption to continue through 2050, while the aggressive scenarios assume that the adoption of conservation agriculture will reach its peak by 2030 and begin to decline as land area under conservation agriculture converts to regenerative agriculture. This conversion was assumed based on the increasing demand for organic and semi-organic agricultural products.
Impacts of increased adoption of conservation agriculture 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: This scenario was determined through analysis of the five custom adoption scenarios, in which the land area under conservation agriculture reaches to its peak (401 million hectares) by 2038 and then declines to 310 million hectares by 2050. The 91 million hectares lost from conservation agriculture are assumed to be converted to regenerative agriculture.
- Drawdown Scenario: In this scenario, the land area under conservation agriculture reaches its peak (313 million hectares) by 2036 and then declines to 243 million hectares by 2050; the difference of 70 million hectares is added to regenerative agriculture.
- Optimum Scenario: This scenario results in the adoption of 267 million hectares by 2030, which declines to 204 million hectares by 2050. The difference of 63 million hectares is added to regenerative agriculture.
Usually, the adoption area under any solution increases from the Plausible to Optimum Scenario; however, this is not the case for conservation agriculture, due to its transition to regenerative agriculture. Thus, a continuous decrease in conservation agriculture leads to a continuous increase in regenerative agriculture from the Plausible to Optimum Scenarios.
Emissions, Sequestration, and Yield Model
Sequestration rates are set at 0.71, 0.35, 0.61, and 0.25 tons of carbon per hectare per year for tropical humid, temperate/boreal humid, tropical semi-arid, and temperate/boreal semi-arid zones, respectively. These are the result of meta-analysis of 62 data points from 34 sources. Emissions reduction rates from conservation agriculture are 0.23 tons of carbon dioxide-equivalent per hectare per year, based on meta-analysis of 16 data points from 7 sources.
Yield gains compared to business as usual annual cropping were set at 8.3 percent, based on meta-analysis of 7 data points from 3 sources.
Financial inputs for conservation agriculture were determined via meta-analysis of 33 data points from 11 sources. First costs are estimated at US$157.32  per hectare; for all agricultural solutions, it is assumed that there is no conventional first cost, as agriculture is already in place on the land. Net profit is US$650.65 per hectare per year, compared to US$407.47 for the conventional practice.
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. Adoption of conservation agriculture was constrained by several factors. These include: limiting adoption to cropland of minimal slope, competition for said cropland with rice solutions, and a higher priority for regenerative agriculture. The combined conservation/regenerative agriculture practice is assigned third-level priority for non-degraded cropland of minimal slopes. Only rice-based solutions are more highly prioritized.
Total adoption in the Plausible Scenario is 310.0 million hectares in 2050, representing 39.3 percent of the total available land. Of this, 238.4 million hectares are adopted from 2020-2050. The impact of this scenario is 17.3 gigatons of carbon dioxide-equivalent sequestered by 2050. Net cost is US$37.5 billion. Net savings is US$2,119.1 billion. Yield gain is 2,607.7 million metric tons between 2020-2050.
Total adoption in the Drawdown Scenario is 243.0 million hectares in 2050, representing 30.8 percent of the total available land. Of this, 171.4 million hectares are adopted from 2020-2050. The impact of this scenario is 12.6 gigatons of carbon dioxide-equivalent by 2050.
Total adoption in the Optimum Scenario is 204.0 million hectares in 2050, representing 16.8 percent of the total available land. Of this, 132.4 million hectares are adopted from 2020-2050. The impact of this scenario is 10.1 gigatons of carbon dioxide-equivalent by 2050.
Drawdown’s conservation agriculture mitigation impact is somewhat higher than Intergovernmental Panel on Climate Change (IPCC) benchmarks, which estimate 0.8 gigatons of carbon dioxide-equivalent per year by 2030 for cropland management, excluding rice and agroforestry (Smith, 2007). The Drawdown model shows 0.4-0.7 gigatons carbon dioxide-equivalent per year by 2030 for conservation agriculture and 0.5-0.7 for regenerative agriculture, for a combined 0.9-1.4 gigatons sequestered per year in 2030. This is slightly higher than the benchmark, reflecting the higher sequestration rate modeled for regenerative agriculture.
This study was constrained by limited access to financial data at the farm, regional, and global levels. Future work should include collecting additional data on first costs and net profit per hectare.
Conservation agriculture is already a potent global force for climate change mitigation. Drawdown's model builds on this success, and projects evolution and improvement in the practice (in the form of regenerative agriculture) to keep it a critical agricultural mitigation strategy into the future.
 To learn more about the Total Land Area for the Food Sector, click the Sector Summary: Food link below.
 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.
 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.
 All monetary values are presented in US2014$.
 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.