Update--Use of Conservation Tillage Practices in the U.S.
Tillage is used to control weeds, incorporate crop residue and fertilizers, and prepare land for planting. However, minimizing soil disturbance and maintaining soil cover are critical production practices needed for improving or maintaining soil health.
Soybeans in Mississippi are grown on a variety of soils with varying textures, from sandy to clay. Each of these soils has unique properties and/or conditions that may benefit from some sort of tillage. There is no set rule for if, when, and how much of a particular type of tillage should be used to grow soybeans or any other crop on any of these soils. However, the preponderance of evidence indicates that tillage per se is not required for optimum soybean production on any of these soils. Also, it is accepted that minimizing tillage will lead to enhanced soil properties that will benefit soil health.
A Sept. 2018 report from the USDA-ERS titled “Tillage Intensity and Conservation Cropping in the United States–EIB-197” by Claassen et al. summarizes results from a national-level survey of farming operations that was conducted to identify/estimate tillage and conservation practices’ adoption and use in the production of corn [2001, 2005, 2010, and 2016], soybeans [2002, 2006, and 2012], cotton [2003, 2007, and 2015], and wheat [2004, 2009, 2017] in the U.S. Major results from that survey were summarized in a previous article on this website. In Oct. 2022, the USDA-ERS published an update that provides a chart with results for more recent years–e.g. 2018 for soybeans and 2021 for corn. Click here for that update.
To ensure that the survey results are interpreted correctly, the below partial glossary of terms provided in the report is shown.
• Conservation Tillage: Tillage management practices that result in a STIR (see below) of less than or equal to 80, and do not use a moldboard plow. Conservation tillage practices can include mulch-till, no-till, and strip-till.
• Conventional Tillage: A combination of tillage management practices that result in a STIR >80.
• Crop Residue: Plant material, such as cornstalks or soybean stubble/residue, that remains after harvest.
• Mulch-Till: A type of conservation tillage where soil is tilled (e.g. with a chisel plow) but soil disturbance is low [STIR <80].
• No-Till: The practice of refraining from tilling the soil from harvest of the previous crop to harvest of the current crop.
• Residue Harvest: The practice of harvesting the residue of a cash crop for a secondary use [e.g. cornstalks for ethanol production].
• Soil Health: The continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans. Soil health benefits from conservation tillage may be fully realized only when practices such as no-till, mulch-till, or strip-till that minimize soil disturbance are used consistently over time.
• Soil Tillage Intensity Rating [STIR]: A numerical index that represents the type and severity of soil disturbance caused by tillage operations. The STIR value incorporates the type, speed, depth, and degree of disturbance caused by tillage.... The STIR is the sum of STIR values of individual tillage operations.
• Strip-Till: A tillage system used to minimize soil disturbance in row crops by tilling only in narrow strips where seeds are planted. In fields where strip-till is used, the STIR is typically <80.
Major findings from the survey update that pertain to conservation tillage systems used in U.S. soybean production follow. [Remember that using STIR rather than methods based on soil residue cover (previously used to estimate conservation tillage adoption) focused the estimates on soil disturbance rather than a combination of soil disturbance and residue cover from a previous crop].
• Conservation tillage [no-till and mulch-till] was used on about 70% of soybean acres in 2012 and 74% of soybean acres in 2018.
• Most of the small increase in use of conservation tillage on soybean acres in this time span resulted from an increase in use of mulch-till.
• Conservation tillage [no-till and mulch-till] was used on about 66% of corn acres in 2016 and about 76% of corn acres in 2021.
• Most of the increase in use of conservation tillage on corn acres in this time span resulted from an increase in use of no-till.
• See the aforementioned previous article for more details about the original survey.
To increase sustainability in U.S. soybean cropping, conservation programs must increasingly focus on reducing tillage and adopting cropping practices that will improve soil health. The above original and updated survey results can be used to determine the recent use of these practices, as well as where their adoption can or should be increased.
Composed by Larry G. Heatherly, Nov. 2022, larryh91746@gmail.com