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^{3, 4, 5, 6, 7}. Improving soil quality and structure increases water penetration and soil’s moisture content and reduces run-off^{2, 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) concentrations^{3, 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 used^{3, 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 costs^{16, 17}. By reducing fuel use, conservation tillage also reduces emissions^{18, 19}. Conservation tillage practices, especially no-till farming, may be an effective means of carbon sequestration²⁰, although studies show variation in the amount of stored carbon by region, crop⁷, and depth^{6, 19, 21}. 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.

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 acres²².

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 farming^{23, 24}.

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 rotations²⁵.