Conservation tillage practices

Evidence Rating  
Scientifically Supported
Evidence rating: Scientifically Supported

Strategies with this rating are most likely to make a difference. These strategies have been tested in many robust studies with consistently positive results.

Health Factors  
Decision Makers

Tillage is the preparation of land to grow crops, which involves digging, stirring, and overturning soil. Conservation tillage is any method of soil cultivation that keeps at least one-third of cultivated soil covered with the previous year’s crop residue. There are several types of reduced or low-intensity tillage, including mulch till, ridge till, strip till, and no-till; under no-till farming the soil is not tilled at all. Conservation tillage is often used with crop rotations, cover cropping, composting, and other soil erosion control practices. Tillage practices affect soil carbon and water pollution, as well as farmers’ energy and fertilizer use1, 2.

Expected Beneficial Outcomes (Rated)

  • Reduced soil erosion
  • Improved soil quality

Other Potential Beneficial Outcomes

  • Reduced run-off
  • Improved water quality
  • Reduced emissions

Evidence of Effectiveness

There is strong evidence that conservation tillage and no-till practices reduce soil erosion and improve soil quality and structure, especially in the soil’s top surface layer3, 4, 5, 6, 7. Improving soil quality and structure increases water penetration and soil’s moisture content and reduces run-off2, 8. Agricultural run-off can carry excess nutrients, sediment, pesticides, and other pollutants that contaminate surface water and groundwater9.

Conservation tillage improves soil quality by increasing soil microbial properties, particularly soil microbial count and fungal and bacterial biomass, as well as significantly increasing soil total carbon (C) and nitrogen (N) concentrations3, 4. Greater soil organic C concentrations increase soil productivity, biological activity, and improve crop resilience to extreme weather conditions6. Conservation tillage practices also improve soil physical properties, for example, bulk density, available water capacity, and soil pH5. Effectiveness varies depending on site context and duration of conservation tillage practices, with greater improvements in soil quality the longer conservation tillage practices are used3, 4. Soil quality improvements from conservation tillage and no-till practices are enhanced when combined with increased crop residue retention practices4, crop rotations, and cover cropping10. Soil texture also influences effectiveness; conservation tillage practices are least effective for sandy soils3.  

The effects of adopting no-till techniques on crop yield vary significantly by climate and crop category; overall, yields tend to decline initially in the first few years, and then increase over the longer term. The best yields are typically in rainfed conditions in dry climates, where yields are often equal to or better than those produced under conventional tillage practices11. Once established, no-till practices provide consistent, high yields with enhanced yield stability against unfavorable environmental conditions, especially when practices also include using legume, or nitrogen-fixing, cover crops12. In some cases, farmers increase N fertilizer applications to avoid initial declines in crop yields when implementing no-till practices; however, this practice increases potential N run-off and soil nitrous oxide emissions13.

Conservation tillage, especially no-till practices, appear to reduce nitrate loss in the event of intense rainstorms, while conventional tillage systems in intense rainstorms increase N leaching to groundwater14. Conservation tillage and no-till practices can also reduce run-off of minerals and other nutrients15.

Conservation tillage can increase profitability and reduce farm operating costs, since fewer tillage trips reduce fuel use, labor costs, and machinery repair costs16, 17. By reducing fuel use, conservation tillage also reduces emissions18, 19. Conservation tillage practices, especially no-till farming, may be an effective means of carbon sequestration, although studies show variation in the amount of stored carbon by region, crop7, and depth6, 19, 20. Transitioning tilled cropland to no-till and conservation tillage has substantial potential to mitigate climate change via C storage6. However, the potential benefits of soil carbon sequestration for climate change may be limited if nitrous oxide emissions increase from N fertilizer applications during tillage transition periods13.

Impact on Disparities

No impact on disparities likely

Implementation Examples

According to the 2017 Census of Agriculture, US farmers used no-till practices on 104.5 million acres, conservation tillage on 97.8 million acres, and conventional tillage on 80 million acres. These numbers represent a 35% decline in the number of farms and a 24% decline in the number of acres under intensive tillage methods since 2012. Kansas, Nebraska, Iowa, Montana, North Dakota, South Dakota, and Illinois are the top states in no-till practices by millions of acres, and Iowa, Illinois, North Dakota, Minnesota, Kansas, and Nebraska are the top states in conservation tillage by millions of acres21.

Some states (e.g., Minnesota) have established resources to support conservation tillage practices2. In other states (e.g., Pennsylvania and Colorado) producers have formed a network to share ideas and experiences to support no-till farming22, 23.

The American Farmland Trust (AFT) is a national organization that supports and promotes the adoption of environmentally sound farming practices that sequester carbon in the soil to combat climate change, prevent erosion, reduce runoff, and rebuild soil health, including no-till, cover crops, and crop rotations24.

Implementation Resources

USDA-NAL Conservation tillage - US Department of Agriculture (USDA), National Agricultural Library (NAL). Soil and water management: Conservation tillage practices and erosion control.

MU Ext-No-till planting manual - University of Missouri Extension (MU Ext). Missouri no-till planting systems manual. M164;1997.

USDA-Ag census by state - US Department of Agriculture (USDA). 2012 Census of agriculture publications: Census by state.

Footnotes

* Journal subscription may be required for access.

1 USDA-Horowitz 2010 - Horowitz J, Ebel R, Ueda K. “No-till” farming is a growing practice. Washington, DC: US Department of Agriculture (USDA), Economic Research Service (ERS); 2010.

2 MN BWSR-Conservation tillage - Minnesota Board of Water and Soil Resources (MN BWSR). Carbon sequestration: Conservation tillage and cover crops.

3 Chen 2020* - Chen H, Zhongmin D, Veach A, et al. Global meta-analyses show that conservation tillage practices promote soil fungal and bacterial biomass. Agriculture, Ecosystems and Environment. 2020;293:106841.

4 Li 2020* - Li Y, Zhang Q, Cai Y, Yang Q, Chang SX. Minimum tillage and residue retention increase soil microbial population size and diversity: Implications for conservation tillage. Science of the Total Environment. 2020;716:137164.

5 Li 2019a* - Li Y, Li Z, Cui S, Jagadamma S, Zhang Q. Residue retention and minimum tillage improve physical environment of the soil in croplands: A global meta-analysis. Soil and Tillage Research. 2019;194:104292.

6 Haddaway 2017 - Haddaway NR, Hedlund K, Jackson LE, et al. How does tillage intensity affect soil organic carbon? A systematic review. Vol 6. BioMed Central; 2017.

7 Manley 2005* - Manley J, van Kooten GC, Moeltner K, Johnson DW. Creating carbon offsets in agriculture through no-till cultivation: A meta-analysis of costs and carbon benefits. Climatic Change. 2005;68(1-2):41-65.

8 Zhang 2007* - Zhang GS, Chan KY, Oates A, Heenan DP, Huang GB. Relationship between soil structure and runoff/soil loss after 24 years of conservation tillage. Soil and Tillage Research. 2007;92(1-2):122-128.

9 USDA-NRCS Water - US Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS). Water.

10 Jilling 2020* - Jilling A, Kane D, Williams A, et al. Rapid and distinct responses of particulate and mineral-associated organic nitrogen to conservation tillage and cover crops. Geoderma. 2020;359:114001.

11 Pittelkow 2015 - Pittelkow CM, Linquist BA, Lundy ME, et al. When does no-till yield more? A global meta-analysis. Field Crops Research. 2015;183:156-168.

12 Nouri 2020a* - Nouri A, Lee J, Yoder DC, et al. Management duration controls the synergistic effect of tillage, cover crop, and nitrogen rate on cotton yield and yield stability. Agriculture, Ecosystems and Environment. 2020;301:107007.

13 Wang 2020* - Wang J, Zou J. No-till increases soil denitrification via its positive effects on the activity and abundance of the denitrifying community. Soil Biology and Biochemistry. 2020;142:107706.

14 Hess 2020* - Hess LJT, Hinckley ELS, Robertson GP, Matson PA. Rainfall intensification increases nitrate leaching from tilled but not no-till cropping systems in the U.S. Midwest. Agriculture, Ecosystems and Environment. 2020;290:106747.

15 Pisani 2020 - Pisani O, Liebert D, Bosch DD, et al. Element losses from fields in conventional and conservation tillage in the Atlantic Coastal Plain, Georgia, United States. Journal of Soil and Water Conservation. 2020;75(3):376-386.

16 Knowler 2007* - Knowler D, Bradshaw B. Farmers' adoption of conservation agriculture: A review and synthesis of recent research. Food Policy. 2007;32(1):25-48.

17 USDA-NRCS Boyle 2006 - Boyle K. The economics of on-site conservation tillage. US Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS); 2006.

18 USDA-NRCS 2012 - US Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS), US Environmental Protection Agency (US EPA). Agricultural air quality conservation measures: Reference guide for cropping systems and general land management. 2012.

19 Alvarez 2005* - Alvarez R. A review of nitrogen fertilizer and conservation tillage effects on soil organic carbon storage. Soil Use and Management. 2005;21(1):38-52.

20 Bauer 2006* - Bauer PJ, Frederick JR, Novak JM, Hunt PG. Soil CO2 flux from a norfolk loamy sand after 25 years of conventional and conservation tillage. Soil and Tillage Research. 2006;90(1-2):205-11.

21 USDA-Ag Census 2017 - US Department of Agriculture (USDA), Natural Agricultural Statistics Service. 2017 Census of Agriculture: United States Summary and State Data.

22 PA No-Till - Pennsylvania No-Till Alliance. Farmers improving soil health.

23 CO No-till - Colorado Conservation Tillage Association. Serving the conservation and no-till farmers of the High Plains.

24 AFT - American Farmland Trust (AFT). Agricultural conservation innovation center.

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