Conservation tillage practices

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 layer (Chen 2020, Li 2020, Li 2019a, Haddaway 2017, Manley 2005). Improving soil quality and structure increases water penetration and soil’s moisture content and reduces run-off (MN BWSR-Conservation tillage, Zhang 2007). Agricultural run-off can carry excess nutrients, sediment, pesticides, and other pollutants that contaminate surface water and groundwater (USDA-NRCS Water).

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) concentrations (Li 2020, Chen 2020). Greater soil organic C concentrations increase soil productivity, biological activity, and improve crop resilience to extreme weather conditions (Haddaway 2017). Conservation tillage practices also improve soil physical properties, for example, bulk density, available water capacity, and soil pH (Li 2019a). Effectiveness varies depending on site context and duration of conservation tillage practices, with greater improvements in soil quality the longer conservation tillage practices are used (Li 2020, Chen 2020). Soil quality improvements from conservation tillage and no-till practices are enhanced when combined with increased crop residue retention practices (Li 2020), crop rotations, and cover cropping (Jilling 2020). Soil texture also influences effectiveness; conservation tillage practices are least effective for sandy soils (Chen 2020).

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 practices (Pittelkow 2015). 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 crops (Nouri 2020a). 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 emissions (Wang 2020).

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 groundwater (Hess 2020). Conservation tillage and no-till practices can also reduce run-off of minerals and other nutrients (Pisani 2020).

Conservation tillage can increase profitability and reduce farm operating costs, since fewer tillage trips reduce fuel use, labor costs, and machinery repair costs (Knowler 2007, USDA-NRCS Boyle 2006). By reducing fuel use, conservation tillage also reduces emissions (USDA-NRCS 2012, Alvarez 2005). Conservation tillage practices, especially no-till farming, may be an effective means of carbon sequestration (Project Drawdown-Reg Ag), although studies show variation in the amount of stored carbon by region, crop (Manley 2005), and depth (Haddaway 2017, Bauer 2006, Alvarez 2005). Transitioning tilled cropland to no-till and conservation tillage has substantial potential to mitigate climate change via C storage (Haddaway 2017). 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 periods (Wang 2020).

According to the 2017 Census of Agriculture, U.S. 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 acres (USDA-Ag Census 2017).

Some states (e.g., Minnesota) have established resources to support conservation tillage practices (MN BWSR-Conservation tillage). In other states (e.g., Pennsylvania and Colorado) producers have formed a network to share ideas and experiences to support no-till farming (PA No-Till, CO No-till).

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 rotations (AFT).

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

Project Drawdown-Reg Ag - Project Drawdown. Climate solutions: Regenerative annual cropping.

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

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

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

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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

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.

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

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.

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.

Project Drawdown-Reg Ag - Project Drawdown. Climate solutions: Regenerative annual cropping.

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

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

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

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

USDA-NRCS Water - U.S. Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS). Water.

USDA-WI Ag Census 2017 - U.S. Department of Agriculture (USDA), Natural Agricultural Statistics Service. 2017 Census of Agriculture: Wisconsin State and County Data.

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.

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.