Forbs, annual grasses
Indiscriminate
Moderate–high ($1000–$5000/gross)
Low–moderate risk
Moderate risk
High risk
High (erosion, sensitive plants, wildlife, habitat)
Overview
Tillage involves purposely disturbing the soil to sever, chop, bury or desiccate weeds. This occurs most often on large scales by large mechanized agricultural equipment but can be conducted at smaller scales with mechanized push equipment as well. The terms tillage and cultivation and are often used interchangeably when referring to a method of controlling weeds through soil disturbance with a mechanical implement.
Tillage is most common in agricultural settings but can also be used in rangelands and other non-crop areas. Historically tillage equipment was pulled by draft animals, but most modern tillage is accomplished with mechanized equipment (tractors, off-road vehicles, or mechanized push equipment). This document is specific to mechanized tillage. The use of hand tools to sever weeds in the soil is covered in other BMP sections on stirrup and scuffle hoe and grub hoes.
Tillage has been a method of controlling weeds in agriculture for millennia, and a variety of tools have been developed to aid in reducing weeds. Implements commonly used for tillage include cultivators, harrows, and plows, alone or in combination. If a land manager does not have access to large agricultural equipment, smaller tillage options include a rototiller or dragging implements behind an off-road vehicle (ORV). Tillage equipment should always be thoroughly washed before and after working on a new site to prevent unwanted dispersal of weed seeds or propagules.
Tillage is a non-selective form of weed control that causes extensive soil disturbance. It can be used to prepare sites for the establishment of desirable species through active revegetation.
How to Use
Effective tillage for weed control involves dragging metal blades and/or tines through the soil, usually pulled by a tractor. The depth and shape of the blade or tines vary with the type of soil, whether the soil is to be turned over (thus burying the weeds), or if the blade just severs the weeds underground. The types of weeds, slope, soil type, soil depth and moisture content will determine which implements to use.
The main categories of mechanized tillage equipment used for weed control includes cultivators, harrows, and plows, each with several variations. Many have local names or are referred to by manufacturer name, which can be confusing to non-experts. Cultivators include equipment with tines (sometimes called teeth or shanks) that are dragged through the soil, or equipment that use rotary motion of discs to uproot or bury weeds and weed seed. Cultivators generally only disturb linear trails and not the entire soil surface, as they were designed to till soil on either side of a row of a planted crop. Plows use blades to turn over soil layers, creating furrows and also burying weeds and weed seed. Plows (e.g., chisel plow or soil ripper) usually created the deepest soil disturbance. Harrows use blades (e.g. disc harrow), tines, or chains to create a shallow soil disturbance relative to plows but cover the entire soil surface as opposed to cultivators.
Tilling is most efficient on large, flat areas with friable soils lacking clods or stones, with relatively uniform weed infestations. Often sites need to have low or reduced residual vegetation to avoid clogging or breaking the equipment, especially when using rotary tillers. This is not necessarily true for deep ripping with heavy tines or plowing non-woody vegetation. Tillage in steeply sloped areas is not advised because of high safety risk and erosion risk.
When using large equipment good road access is crucial so that the equipment may be off-loaded from trailers used for transport. That said, if tillage equipment is mounted on a three-point hitch and can be elevated above the soil surface and vegetation, a tractor can drive for miles to reach control sites once off-loaded. In more remote settings or areas with more difficult access tillage implements are pulled/propelled with ORVs.
Larger implements are more efficient because more soil can be tilled with a single pass of machinery. Width of implements can vary greatly from 20 to 60 feet wide field cultivators, to single row cultivators with wings a few inches wide.
Control is most easily achieved for annual weeds that do not resprout when buried by turning over soil layers. Repeated tillage in consecutive years is often required for successful weed control. Tillage is best used at a time of year when the soil is not so dry that wind erosion is a concern, but not excessively wet so that damage to soil structure is a risk. Furthermore, proper soil moisture is critical for implements to be able to penetrate the soil, working the ground appropriately. Hard dry soil may not be effectively penetrated with tilling implements.
Depth of tillage will depend on the size of the weeds. Weeds in the seedling stage can be tilled at a depth of a few inches. This can be done with a drag harrow, or in some cases by dragging objects such as bundles of old tires, or chain link fencing using a pickup truck, ATV or UTV. When using modified (non-agricultural) equipment several passes may be necessary to adequately control the seedling weeds (this can also be true for a traditional disc harrow). Dragging these sorts of implements will disturb the soil surface and uproot seedling plants, while minimizing soil disturbance compared to deeper tillage with other implements. Weeds that are well established may need to be tilled at a depth of several to many inches in order to sever the stem below the soil surface. Larger perennial weeds may need to be deeply plowed with a chisel plow or ripper at a depth of 8 in. to greater than a foot. Do not till perennial plants with rhizomatous roots, as tillage can break up the roots into smaller pieces, spreading patches throughout the field.
Tilling is indiscriminate and cannot be used selectively when weeds are intermixed with desirable vegetation. Tractors can drive around established native perennials or patches of annuals when cover is low or patchy. If desirable vegetation cover is high, tillage should not be used unless removing desirable species is considered acceptable. Smaller equipment such as ATVs/UTVs can be more selective because they can be steered around nontarget vegetation more easily.
Tilling can be used to selectively remove weeds growing at different seasons. For example, winter annual weeds (e.g., wild oatsAvena spp., bromesBromus spp., or storkbillsErodium spp.) can be tilled from fall through winter if desirable spring or summer annuals, especially those that thrive in disturbed soils (e.g., doveweed,Croton setiger, or tarweeds,Deinandra spp.). are planted later in the growing season. Depending on precipitation, soil moisture, temperatures, and other factors, multiple flushes of weed seedlings may emerge which will require multiple tillage events.
Repeated tilling is often used to flush the weed seed bank by bringing more deeply buried seeds or propagules closer to the soil surface. These seeds will sprout and can be killed with a repeated tilling or other treatment. Additionally, when invasive species have built up a shallow seedbank, tillage utilizing an implement such as a moldboard plow can invert the soil deeply burying that shallow seedbank. This type of tillage can only take place in deep non rocky soils and may require active revegetation of desirable species following the treatment.
Utilization of competitive planting is almost always necessary following tillage for invasive weed control. The soil disturbance associated with tillage can promote new or increased weed invasion on site and may be harmful over the long term if disturbed soils are not actively revegetated. Many weed species present in California thrive in disturbed soils and tillage will promote ruderal species colonization and development on site. Species such as tumbleweed (Salsola spp.), invasive annual grasses (non-nativeHordeum spp.,Avena spp., andBromus spp., among others), field bindweed (Convolvulus arvensis) or hairy fleabane (Erigeron bonariensis) all thrive in disturbed soils. Without additional management of these weeds, land managers may face a problem worse than initially found on the site. On the other hand, tilling is one of the few non-chemical weed control methods that can be highly effective for killing weeds uniformly in heavily infested fields (From small to large and very large sites, over 100 or even 1,000 ac.).
Tilling may not result in eradication of a weed species from a site and is usually best used in combination with other techniques as part of an integrated weed management strategy. As a standalone technique, tillage can be effective for local eradication under the following conditions:
- The target population is limited to flat ground and accessible by road,
- There are no cultural resources present that are sensitive to soil disturbance,
- There are no sensitive species interspersed among the target invasive population,
- The soil can be deeply tilled if perennials with extensive root systems or underground reproductive structures are present, and
- Repeated tillage (multiple times per year) is possible to address the soil seed bank and to control plants that are missed.
Some important caveats exist for the last two points. First, tillage is generally not recommended for perennial species unless the entire plant can reliably be uprooted and left to desiccate on the soil surface (rooting depth and rooting system are important considerations). Second, repeated tillage can be very expensive and is associated with accelerated soil erosion.
Tillage will require expensive machinery and managers should budget not only for operation but also for maintenance, depreciation, transportation and fuel. The method itself is costly but can be cost effective at large scales or for repeated treatments. Associated restoration costs may be inevitable and also costly due to the disturbance of the area.
Special Tips
Shallow tillage can be achieved via equipment like a flexible tine harrow, rotary hoe, or Perfecta® cultivator. This is useful to avoid disturbing deeply buried weed seed or perennial structures like tubers of desirable species. Deeper tillage can be achieved using equipment with strong tines (rippers and chisels) that can be a foot or more in length. This can be useful for uprooting shrub and tree species or severing deep roots. Often these larger tines are attached to equipment with tracks and require substantial of power to drag the implement through the soil. Utilization of these deep implements can be useful for breaking up soil in heavily compacted areas such as restoration of old roads
Another modification of this technique is chaining. Chaining is most typically used on rangelands where the cover of woody species is above target levels. In this technique a long piece of marine anchor chain is dragged on the ground between two tractors, or in a large circle with one tractor. Chaining will disturb the soil and uproot or break the stem of woody weeds. This technique is best used on woody weeds that do not resprout. If woody weeds can resprout, the improvements will only last several years and will need additional treatments to reduce the surviving woody plants. Often herbaceous vegetation will be only moderately damaged by the chain and will quickly recover on the site. As with all tilling, soil disturbance and erosion following chaining could be significant.
Some farmers who practice organic agriculture or conservation tillage are developing tilling methods that greatly reduce weed populations and, in some cases, reduce soil disturbance too. These methods can vary from using various plow types in novel ways to detailed timing of tilling. These methods are not discussed in this document, but land managers are encouraged to contact their local experts to learn more about methods that may be adapted to wildlands.
Optimal Conditions for Use
Weeds are best tilled when small and optimally at the seedling stage. Terrain should consist of large, flat areas, and soils should be in a condition that can be easily worked. Annual and biennial plants are easily controlled with tillage, but it is important to till before plants produce fruits or underground storage structures (bulbs, tubers rhizomes, etc.) as tilling can exacerbate weed issues by spreading propagules. Perennial species can be controlled well with tillage if used during the summer months when conditions are hot and dry, and perennial underground structures can be brought to the soil surface to desiccate and die. (This is only effective for perennials with shallow and discrete root systems.) Under cooler or moister conditions, tillage may be counterproductive by cutting up the perennial underground structures and spreading these vegetative propagules throughout the area, exacerbating the problem. Small shrubs, tree seedlings, and vines may be effectively controlled if tillage is performed during summer months under hot and dry conditions.
Caveats
Tillage requires the use of mechanized equipment, and in some cases this equipment is expensive and requires specially trained operators. Tillage can result in short-term control of certain weeds but can also exacerbate weed problems in the absence of repeated treatments. In this case an integrated weed management strategy or a restoration plan is necessary. Repeated tillage can shift vegetation composition toward the dominance of more disturbance-adapted species, which are often invasive weeds, and less diverse plant communities. Tillage may exacerbate spread of perennial grass weeds and those with underground storage structures but provides excellent control of annuals.
Potential Hazards to Humans, Environment, and Cultural Resources
Human hazards. Moderate risk. All vehicles, heavy machinery, and cutting equipment incurs direct risk of human injury. Internal combustion engines typically use petroleum products that generate chemicals known to have acute and chronic risks from exposure.
Habitat. High risk. Tillage disrupts the soil surface and soil structure. It has very high impact to undisturbed habitat.
Sensitive species. High risk. Ground nesting birds and burrowing animals are particularly susceptible to mortality or injury from tillage. Tillage should be performed outside of the breeding season for birds or avoided altogether when burrowing animals that are priorities for conservation are present. Slow moving animals like reptiles, amphibians, turtles and tortoises cannot outrun tillage machinery and are also at risk. Juveniles of species such as deer may often hide in high weed cover so care should be taken to avoid tillage when juveniles of these species are known to be present.
Erosion. High risk. Tillage breaks the soil crust and removes vegetation that otherwise covers soil surfaces, leaving the surface highly vulnerable to erosion from wind and rainfall. Silt fences should be employed wherever tillage is used next to streams or other waterways, or where there is undisturbed habitat downslope.
Cultural. High risk. Tillage should not be used in areas where cultural resources are present unless under supervision of the appropriate regulatory jurisdiction or agency.
Consider Combining with the Following Non-Chemical Methods
The flush of seedlings following the soil disturbance from tillage can be controlled with other tools, such as flaming or solarization for smaller-scale control efforts. Mowing can be employed to reduce seed production of target weeds while maintaining vegetative cover and minimizing erosion.
Tillage can be used in combination with other methods that first reduce residual vegetation. For example, livestock grazing or prescribed fire can be used before tillage to reduce vegetation which would otherwise clog or damage equipment.
Tillage can be used in conjunction with competitive planting. Tillage can be an excellent way to prepare a seedbed at a highly disturbed site by loosening soil while controlling non desirable species the site. Often tillage is utilized in areas with large populations of non-desirable vegetation. Planting desirable species into the areas which have been tilled is often necessary to shift the community to a more desirable plant community.
Don’t Use This Technique When/For
Caution should be used when tilling any species that reproduces vegetatively. Tillage can be used effectively against such species under specific conditions, such as during hot and dry weather when underground reproductive structures can be brought to the soil surface to desiccate, though unintentional spread of propagules is still a concern.
Damage to soil structure is likely under moist conditions, so tillage cannot typically be used in marsh, wetland or riparian settings.
Tillage can be used in shrubland, woodland, and forest areas (assuming that spacing of woody species allows for access of mechanized equipment) but damage to nontarget species is likely.
Moderate to steep slopes should be avoided due to risk of vehicle rollover and erosion.
Tillage cannot be used under cobbly or rocky conditions.
Supplementary Information
In some wildland restoration projects tilling is used to control weeds on large-scale restoration plots of several hundred acres. For example, an entire field may be tilled to control the weeds, then planted with native trees in rows (at 8 ft. apart), maintaining a 2’-wide planting area and a 6’-wide tilling area to manage weeds throughout the growing season. Spacing between the rows can vary depending on the tractor width and the height of the native plants. If trying to establish large perennial shrubs or trees, the minimum row spacing will be the width of the tractor. If establishing shorter wildflowers or native grasses a variety of agricultural implements can be used to shape narrow bed widths.
In some areas tillage may be used to add a soil disturbance that has been lost. For example, in some wind-blown sand dune habitats weeds dominate the soil surface and reduce sand movement. Tillage can break up the weed’s roots and reduce soil structure to allow for the movement of sand on windy days. Careful planning is required to avoid stuck equipment, excessive erosion and sand deposition on downwind properties.
References
Bottoms, R.M., and T.B. Whitson. 1998. A systems approach for the management of Russian knapweed (Centaurea repens). Weed Technology 12: 363-366.
Brown, M.L., C.A. Duncan, and M.B. Halstvedt. 1999. Spotted knapweed management with integrated methods. Proceedings of the Western Society of Weed Science 52: 68-70.
Clements, C.D., D.N. Harmon, M. Weltz, and J. White. 2016. Wildlife Habitat Improvement Using Range Improvement Practices. Society for Range Management Meeting Proceedings. 69:93. https://www.ars.usda.gov/research/publications/publication/?seqNo115=321723. (accessed 8/12/19).
Clements, C.D., D.N. Harmon, and J.A. Young. 2009. The Effects of Discing to Reduce Cheatgrass Competition Following Wildfires [abstract]. Society for Range Management, Albuquerque, New Mexico, February 8-12, 2009. 62:33. https://www.ars.usda.gov/research/publications/publication/?seqNo115=229998 (accessed 8/12/19).
DiTomaso, J.M., G.B. Kyser, and M.J. Pitcairn. 2006. Yellow starthistle management guide. Cal-IPC Publication 2006-03. California Invasive Plant Council: Berkeley, CA. 78 pp.
Grey, T.L., T.M. Webster, X. Li, W. Anderson, and G.S. Cutts. 2015. Evaluation of control of Napiergrass (Pennisetum purpureum) with tillage and herbicides. Invasive Plant Science and Management 8: 393-400.
MacDonald, N.W., L.M. Martin, C.K. Kapolka, T.F. Bottling, and T.E. Brown. 2013. Hand pulling following mowing and herbicide treatments increases control of spotted knapweed (Centaurea stoebe). Invasive Plant Science and Management 6: 470-479.
Miller, T.W. 2016. Integrated strategies for management of perennial weeds. Invasive Plant Science and Management 9: 148-159.
Miller, T.W., and D.E. D’Auria. 2011. Effects of herbicide, tillage, and grass seeding on wild chervil (Anthriscus sylvestris). Invasive Plant Science and Management 4: 326-331.
Patten, K., C. O'Casey, and C. Metzger. 2007. Large-Scale Chemical Control of Smooth Cordgrass (Spartina alterniflora) in Willapa Bay, WA: Towards Eradication and Ecological Restoration. Invasive Plant Science and Management 10: 284-292.
Rask, A.M., and P. Kristoffersen. 2006. A review of non-chemical weed control on hard surfaces. Weed Research 47:370-380.
Tu, M., C. Hurd, and J.M. Randall. 2001. "Weed Control Methods Handbook: Tools & Techniques for Use in Natural Areas" The Nature Conservancy Paper 533. https://digitalcommons.usu.edu/govdocs/533
Vitelli, J.S., B.A. Madigan, and P.E. van Haaren. 2010. Control techniques and management strategies for the problematic Navua sedge (Cyperus aromaticus). Invasive plant science and management 3: 315-326.
Walker K.J., C. Auld, E. Austin, and J. Rook. 2016. Effectiveness of methods to control the invasive non-native pitcherplantSarracenia purpurea L. on a European mire. Journal for Nature Conservation 31:1-8.
Authors and Credit
Lead Author: Travis Bean, University of California Extension Weed Specialist, UC Riverside
Co-authors:
Christopher
McDonald, University
of California Extension Weed Specialist, UC ANR
Thomas Getts, University of
California Extension Weed Advisor, UC ANR
Additional Contributors:
Jutta Burger, Science Program Director, California Invasive Plant Council
Efficacies
| Rating | |||
|---|---|---|---|
| Plant | Flowering Period | ||
| Winter | Good | ||
| Spring | Good | ||
| Summer | Good | ||
| Fall | Good | ||
| Multiple Seasons | Good | ||
| None | Good | ||
| Plant | Germination | ||
| Winter | Good | ||
| Winter / Spring | Good | ||
| Spring / Summer | Good | ||
| Opportunistic | Good | ||
| Plant | Palatability | ||
| Yes | No Information | ||
| No | No Information | ||
| Partial | No Information | ||
| Plant | Plant Growth Form | ||
| Grass | Good | ||
| Forb | Excellent | ||
| Shrub | Fair | ||
| Tree | Fair | ||
| Vine | Fair | ||
| Plant | Plant Type | ||
| Annual | Excellent | ||
| Biennial | Excellent | ||
| Perennial | Good | ||
| Plant | Propagule Production | ||
| Low (<1000/square meter) | Good | ||
| Moderate (1000–10,000/square meter) | Good | ||
| High (>10,000/square meter) | Good | ||
| Plant | Rate of Spread | ||
| High (doubling in <10 year) | Good | ||
| Moderate (50–75% increase in 10 years) | Good | ||
| Slow Rate (25% increase in 10 years) | Good | ||
| Plant | Resprouting / Regenerative Capacity | ||
| Low | Good | ||
| Moderate | Fair | ||
| High | Poor | ||
| None | Excellent | ||
| Plant | Seed Life | ||
| Short (≤3 years) | Good | ||
| Moderate (4–10 years) | Good | ||
| Long (>10 years) | Good | ||
| Plant | Type of Reproduction | ||
| Seed | Excellent | ||
| Vegetative | Poor | ||
| Seed & Vegetative | Poor | ||
| Plant | Type of Vegetative Reproduction | ||
| Rhizome / Stolon / Stem | Poor | ||
| Bulb / Corm / Tuber | Poor | ||
| Root sprout / Sucker / Crown sprout | Poor | ||
| Site | Existing Desirable Plant Cover | ||
| <10% | Excellent | ||
| 10–25% | Good | ||
| 26–50% | Fair | ||
| 51–75% | Poor | ||
| >75% | Ineffective | ||
| Site | Ground Condition | ||
| Muddy | N/A | ||
| Smooth | Excellent | ||
| Cobbly | Ineffective | ||
| Rocky | Ineffective | ||
| Site | Habitat | ||
| Marsh / Wetland | Ineffective | ||
| Riparian | Ineffective | ||
| Grassland | Excellent | ||
| Shrubland | Poor | ||
| Woodland / Forest | Poor | ||
| Site | Level of Tolerable Disturbance | ||
| Low | N/A | ||
| Medium | Poor | ||
| High | Excellent | ||
| Site | Slope | ||
| Flat | Excellent | ||
| Moderate (10–40%) | Poor | ||
| Steep (>40%) | Ineffective | ||
| Site | Target Area | ||
| <40 square feet | Fair | ||
| 0.001–0.01 acre | Good | ||
| 0.02–0.1 acre | Good | ||
| 0.2–1 acre | Excellent | ||
| 2–10 acres | Excellent | ||
| 11–50 acres | Excellent | ||
| 51–100 acres | Excellent | ||
| >100 acres | Good | ||
| Site | Targeted Invasive Plant Cover | ||
| <1% | Poor | ||
| 1–10% | Fair | ||
| 11–25% | Good | ||
| 26–50% | Excellent | ||
| 51–75% | Excellent | ||
| >75% | Excellent | ||
| Site | Vehicle Accessibility | ||
| Roadside | Excellent | ||
| <100 feet from road | Good | ||
| 100–1000 feet from road | Fair | ||
| >1000 feet from road | Poor | ||
