Tillage is traditionally done to prepare a seed bed for planting or mechanical weed control. It can also be used to manage soil moisture/ temperature through the manipulation of residue cover. Tillage is also used to incorporate inputs such as soil-activated, pre-emergence herbicides and broadcast nutrient applications. Tillage happens in association with the planting of annual or perennial seeded crops or transplants.
Tillage intensity to maintain target residue cover encompasses a range of practices. Tillage tools can be set to vary in intensity of soil disturbance to maintain a targeted amount of crop residue on the soil surface. The target is generally an afterplanting residue cover of 30 percent. The purpose of the practices is to reduce in-field sheet and rill erosion. Higher covers of 80 percent might be recommended for surface application of manure or fertilizer. Tillage practices generally fall into three main categories based on how much crop residue is maintained on the soil surface: conservation
tillage, reduced tillage, and conventional tillage. The Conservation Technology Information Center provides descriptions of the various tillage types at ctic.purdue.edu/resourcedisplay/322.
Conservation tillage encompasses a range of tillage types that leaves 30 percent residue cover on the field. Photographic examples are provided for corn and soybean fields.
Tillage Type Definitions
Conservation Tillage Types (30 percent or more crop residue left, after planting).
Any tillage and planting system that covers 30 percent or more of the soil surface with crop residue, after planting, to reduce soil erosion by water. Where soil erosion by wind is the primary concern, any system that maintains at least 1,000 pounds per acre of flat, small grain residue equivalent on the surface throughout the critical wind erosion period is recommended. The pictures below show after planting residue cover with both corn and soybean residue.
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Figure 37. Conservation tillage, leaving 30 percent residue cover. Credit: USDA-NRCS.
No-till
The soil is left undisturbed from harvest to planting. Planting or drilling is accomplished using disc openers, coulter(s), row cleaners, in-row chisels or roto-tillers equiped on the planter frame. Weed control is accomplished primarily with crop protection products. Other common terms used to describe No-till include direct seeding, slot planting, zero-till, row-till, and slot-till.
Figures 38a and 38b. Residue cover for corn (38a) and soybeans (38b) in a no-till system. Credit for both images: Greg LaBarge, OSU Extension.
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Strip-till
The soil is left undisturbed from harvest to planting except for strips up to 1/3 of the row width (strips may involve only residue disturbance or may include soil disturbance). Planting or drilling is accomplished using disc openers, coulter(s), row cleaners, in-row chisels or roto-tillers planted into the prepared strips. Weed control is accomplished primarily with crop protection products. Cultivation may be used for emergency weed control.
Figures 39a and 39b. Strip-till system planting (39a) and afterplanting residue cover (39b). Credit for both images: Greg LaBarge, OSU Extension.
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Ridge-till
The soil is left undisturbed from harvest to planting except for strips up to 1/3 of the row width. Planting is completed on the ridge and usually involves the removal of the top of the ridge. Planting is completed with sweeps, disk openers, coulters, or row cleaners. Residue is left on the surface between ridges. Weed control is accomplished with crop protection products (frequently banded) and/or cultivation. Ridges are rebuilt during row cultivation.
Figures 40a and 40b. Ridge-till system planting (40a) and afterplanting residue cover (40b). Credit for both images: Randall Reeder, OSU Extension.
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Mulch-till
Other Tillage Types:
Reduced-till (15-30% residue)-
Full-width tillage involving one or more tillage trips which disturbs all of the soil surface and is performed prior to and/or during planting. There is 15-30 percent residue cover after planting or 500 to 1,000 pounds per acre of small grain residue equivalent throughout the critical wind erosion period. Weed control is accomplished with crop protection products and/or row cultivation.
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Source: Farming with Residue from NRCS
Conventional-till or intensive-till
Full width tillage which disturbs all of the soil surface and is performed prior to and/or during planting. There is less than 15 percent residue cover after planting, or less than 500 pounds per acre of small grain residue equivalent throughout the critical wind erosion period. Generally involves plowing or intensive (numerous) tillage trips. Weed control is accomplished with crop protection products and/or row cultivation.
Figures 43a and 43b. Conventional tillage, also called intensive tillage, includes tillage and planting systems that leave less than 15 percent residue cover after planting (43a). Conventional or intensive tillage system afterplanting residue cover (43b). Credit for both images: Greg LaBarge, OSU Extension.
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Unofficial:
Stale seedbed is not an official category. The residue level after planting dictates the tillage category (mulch-till, reduced-till, or intensive-till). Fields are tilled full-width soon after harvest. The seedbed “settles” until planting is performed in the undisturbed (settled) seedbed or in re-formed beds (minimum disturbance). Weeds and/or cover crops are controlled with crop protection product(s) and/or row cultivation.
Tillage and residue management take place on any land where a crop is grown.
Conservation tillage practices, including reduced tillage, leave more crop residue on the soil surface during the nongrowing portions of the season and reduce root-zone disturbance. A farmer needs to balance soil conservation goals with crop production needs in selecting a management system for his or her farm.
Factors include:
- reduced sheet, rill, and wind erosion, and excessive soil in surface water.
- reduced tillage-induced particulate emissions (i.e., dust).
- improved soil health and tilth.
- maintained or increased organic matter content.
- reduced energy use and labor.
- maintained water infiltration and soil structure.
Effectiveness
A long-term Ohio study on two different soils found that infiltration rates were at least 1.9–4.2 times greater under a no-till system when compared to those under minimum tillage and conventional moldboard plowing to 25 cm followed by secondary tillage to 10 cm. Reduced-till was comprised of chisel plowing, without soil inversion, to 25 cm followed by cultivation to 10 cm before planting. The study also found that soils in the no-till system had higher soil organic carbon, improved or maintained soil tilth, enhanced aggregate stability, and higher available water content (Kumar et al., 2012).
Diesel fuel use comparisons of different tillage systems determined that a conventional system used 5 gallons/acre, a mulch-till system used 4 gallons/acre, and a no-till system used 3 gallons/acre (NRCS Energy Estimator Tool). NRCS expects the total energy consumption associated with conservation tillage to be reduced by at least 20 percent compared to the conventional tillage. Reduced tillage systems also conserve fuel and reduce labor needs on the farm. Less soil disturbance equals less horsepower needed per pass. Tillage passes can be replaced by a pass made with spray equipment making an herbicide application. Diesel fuel use in in different tillage systems has been calculated with a plowed system using 5.28, chisel 3.34 and no-till at 1.35 gallons per acre.
Conservation tillage practices, including reduced tillage and no-till, leave more crop residue on the soil surface after planting and reduce root zone disturbance resulting in reduced erosion and improved soil tilth. Water infiltration and structure is improved by preservation of natural channels formed by cracks, fissures and biopores. In a long-term study in Ohio on two different soils, Kumar et al. (2012a) found that infiltration rates were at least 1.9 to 4.2 times greater under no-till when compared to those under minimum tillage and conventional moldboard plowing to 25 cm followed by secondary tillage to 10 cm. Reduced-till was comprised of chisel plowing, without soil inversion, to 25 cm followed by cultivation to 10 cm before planting. They also found that soils in the no-till system had higher soil organic carbon, improved or maintained soil tilth, enhanced aggregate stability, and higher available water content (Kumar et al. 2012b).
Organic matter is improved with reduced soil disturbance. Introducing oxygen through tillage activities results in oxidation of organic matter. The short-term benefit of oxidation of organic matter is the release of plant available nutrients but the long-term impact of reduced organic matter is the reduction in water holding capacity, loss of soil tilth and natural nutrient cycling capacity of the soil. For each 1% increase in soil organic matter, water holding capacities will increase 0.75 to 1 inch.
Conservation Tillage leaves significant residue cover to provide for erosion control during the non-growing portions of the season. Maintaining a targeted level of 30% residue cover after planting is recommended to provide enough cover to reduce soil losses. The guide Farming with Crop Residue provides a pictorial view of residue in corn and soybean systems.
Considerations
Maintaining a targeted level of 30 percent residue cover after planting is recommended to provide enough cover to reduce soil losses. NRCS’ guide Farming With Crop Residue provides a pictorial view of residue at different levels of cover in corn and soybean production systems.
Reducing tillage results in system changes that must be accounted for to be successful. Drainage, pH and weed problems should be addressed before moving to no-till.
Drainage and soil type considerations in adoption of no-tillage.
pH and Liming
Cost
Cost of equipment and the required horsepower for the tractor are the major capital costs required to change tillage systems for the farm. Used equipment may be available that will lower the initial cost of the switch. A second consideration will be labor required. Due to actual number of passes involved in the new system vs current practices, more or less labor may be involved.
Residue provides a protective cover to the soil that reduces the energy of raindrops hitting the soil surface. This reduces soil-particle detachment and, ultimately, sheet and rill soil erosion. More intensive tillage systems introduce oxygen, which results in oxidation of organic matter. The short-term benefit of oxidation of organic matter is the release of plant-available nutrients, but the long-term impact of reduced organic matter is the reduction in water holding capacity, loss of soil tilth, and the natural nutrient cycling capacity of the soil. For each 1 percent increase in soil organic matter, water holding capacities increase .75–1 inch (USDA-NRCS). Less intense tillage systems, especially no-till, result in lower soil disturbance and reduced losses of organic matter. This results in a slow building of organic matter percentage.
Lower intensity tillage systems conserve fuel and reduce labor needs on the farm. Less soil disturbance equals less horsepower needed per pass. Tillage passes can be replaced by a pass made with spray equipment making an herbicide application.