||It has been suggested that Zone tillage be merged into this article. (Discuss) Proposed since June 2012.|
Tillage is the agricultural preparation of the soil by mechanical agitation of various types, such as digging, stirring, and overturning. Examples of human-powered tilling methods using hand tools include shovelling, picking, mattock work, hoeing, and raking. Examples of draft-animal-powered or mechanized work include ploughing (overturning with moldboards or chiseling with chisel shanks), rototilling, rolling with cultipackers or other rollers, harrowing, and cultivating with cultivator shanks (teeth). Small-scale gardening and farming, for household food production or small business production, tends to use the smaller-scale methods above, whereas medium- to large-scale farming tends to use the larger-scale methods. There is a fluid continuum, however. Any type of gardening or farming, but especially larger-scale commercial types, may also use low-till or no-till methods as well.
Tillage is often classified into two types, primary and secondary. There is no strict boundary between them so much as a loose distinction between tillage that is deeper and more thorough (primary) and tillage that is shallower and sometimes more selective of location (secondary). Primary tillage such as ploughing tends to produce a rough surface finish, whereas secondary tillage tends to produce a smoother surface finish, such as that required to make a good seedbed for many crops. Harrowing and rototilling often combine primary and secondary tillage into one operation.
"Tillage" can also mean the land that is tilled. The word "cultivation" has several senses that overlap substantially with those of "tillage". In a general context, both can refer to agriculture generally. Within agriculture, both can refer to any of the kinds of soil agitation described above. Additionally, "cultivation" or "cultivating" may refer to an even narrower sense of shallow, selective secondary tillage of row crop fields that kills weeds while sparing the crop plants.
Tillage systems 
Reduced tillage 
Reduced tillage systems leave between 15 and 30% residue cover on the soil or 500 to 1000 pounds per acre (560 to 1100 kg/ha) of small grain residue during the critical erosion period. This may involve the use of a chisel plow, field cultivators, or other implements. See the general comments below to see how they can affect the amount of residue.
Intensive tillage 
Intensive tillage systems leave less than 15% crop residue cover or less than 500 pounds per acre (560 kg/ha) of small grain residue. These types of tillage systems are often referred to as conventional tillage systems but as reduced and conservation tillage systems have been more widely adopted, it is often not appropriate to refer to this type of system as conventional. These systems involve often multiple operations with implements such as a mold board, disk, and/or chisel plow. Then a finisher with a harrow, rolling basket, and cutter can be used to prepare the seed bed. There are many variations.
Conservation tillage 
Conservation tillage systems are methods of soil tillage which leave a minimum of 30% of crop residue on the soil surface or at least 1,000 lb/ac (1,100 kg/ha) of small grain residue on the surface during the critical soil erosion period. This slows water movement, which reduces the amount of soil erosion. Conservation tillage systems also benefit farmers by reducing fuel consumption and soil compaction. By reducing the number of times the farmer travels over the field, farmers realize significant savings in fuel and labor. Conservation tillage was used on about 38%, 109,000,000 acres (440,000 km2), of all US cropland, 293,000,000 acres (1,190,000 km2) planted as of 2004 according to the USDA.
However, conservation tillage systems delay warming of the soil due to the reduction of dark earth exposure to the warmth of the spring sun, thus delaying the planting of the next year's spring crop of corn.
- No-till - Never use a plow, disk, etc. ever again. Aims for 100% ground cover.
- Rotational Tillage - Tills the soil at a specific interval. (every crop, every other year, etc.)
- Zone tillage - a form of deep tillage where only narrow strips are tilled.
Effects of tillage 
- Ploughing loosens and aerates the top layer of soil which can facilitate the planting of the crop.
- It helps in the mixing of residue from the harvest, organic matter (humus) and nutrients evenly throughout the soil.
- It is a mechanical way to destroy weeds.
- Dries the soil before seeding.
- Autumn tilling means that the exposed soil will crumble over winter when frosting and defrosting, helping to prepare a smooth surface for spring planting.
- Dries the soil before seeding.
- The soil loses a lot of its nutrients like nitrogen and its ability to store water. See No-till farming
- Erosion of soil.
- Higher rate of fertilizer and chemical runoff.
- Decreases the water infiltration rate of soil. (Results in more runoff and erosion since the soil absorbs water slower than before)
- Reduces organic matter in the soil (Microbes, carbon compounds, earthworms, ants, etc.).
- Destroys soil aggregates.
- Compaction of the soil, also known as a tillage pan.
- Can attract slugs, cut worms, army worms, and other harmful insects to the left over residues.
- Crop diseases can be harbored in surface residues.
General comments 
- The type of implement makes the most difference, although other factors can have an effect.
- Tilling in absolute darkness (night tillage) might reduce the number of weeds that sprout following the tilling operation by half. Light is necessary to break the dormancy of some weed species' seed, so if fewer seeds are exposed to light during the tilling process, fewer will sprout. This may help reduce the amount of herbicides needed for weed control.
- Greater speeds, when using certain tillage implements (disks and chisel plows), lead to more intensive tillage (i.e., less residue is on the soil surface).
- Increasing the angle of disks causes residues to be buried more deeply. Increasing their concavity makes them more aggressive.
- Chisel plows can have spikes or sweeps. Spikes are more aggressive.
- Percentage residue is used to compare tillage systems because the amount of crop residue affects the soil loss due to erosion.
- See Soybean management practices to see what types of tillage are currently recommended for Soybean Production.
Primary tillage loosens the soil and mixes in fertilizer and/or plant material, resulting in soil with a rough texture.
Secondary tillage produces finer soil and sometimes shapes the rows, preparing the seed bed. It also provides weed control throughout the growing season during the maturation of the crop plants, unless such weed control is instead achieved with low-till or no-till methods involving herbicides.
- The seed bed preparation can be done with harrows (of which there are many types and subtypes), dibbles, hoes, shovels, rotary tillers, subsoilers, ridge- or bed-forming tillers, rollers, or cultivators.
- The weed control, to the extent that it is done via tillage, is usually achieved with cultivators or hoes, which disturb the top few centimeters of soil around the crop plants but with minimal disturbance of the crop plants themselves. The tillage kills the weeds via 2 mechanisms: uprooting them, burying their leaves (cutting off their photosynthesis), or a combination of both. Weed control both prevents the crop plants from being outcompeted by the weeds (for water and sunlight) and prevents the weeds from reaching their seed stage, thus reducing future weed population aggressiveness.
History of tilling 
Tilling was first performed via human labor, sometimes involving slaves. Hoofed animals could also be used to till soil via trampling. The wooden plow was then invented. It could be pulled by mule, ox, elephant, water buffalo, or similar sturdy animal. Horses are generally unsuitable, though breeds such as the scyne could work. The steel plow allowed farming in the American Midwest, where tough prairie grasses and rocks caused trouble. Soon after 1900, the farm tractor was introduced, which eventually made modern large-scale agriculture possible.
Alternatives to tilling 
Modern agricultural science has greatly reduced the use of tillage. Crops can be grown for several years without any tillage through the use of herbicides to control weeds, crop varieties that tolerate packed soil, and equipment that can plant seeds or fumigate the soil without really digging it up. This practice, called no-till farming, reduces costs and environmental change by reducing soil erosion and diesel fuel usage. Researchers are investigating farming in polyculture that would eliminate the need for both tillage and pesticides, such as no-dig gardening.
See also 
- Advance sowing
- Optimum water content for tillage
- SWEEP (Soil and Water Environmental Enhancement program)
- TERON (Tillage erosion)
- "Strip Till for Field Crop Production". Ag.ndsu.edu. 2012-11-14. Retrieved 2012-12-20.
- Gebhardt_et_al. 1985
- "Soil Compaction and Conservation Tillage". Conservation Tillage Series. PennState- College of Agricultural Sciences - Cooperative Extension. Retrieved 26 March 2011.
- Conservation Tillage and Residue Management to Reduce Soil Erosion University of Missouri: Extension
- "Nightmare in Tilling Fields - a Horror for Weed Pests". Ars.usda.gov. Retrieved 2012-07-05.
- Mahdi Al-Kaisi, Mark Hanna, Michael Tidman (May 13, 2002). "Methods for measuring crop residue". Iowa State University. Retrieved 2012-12-28.
- Sprague, Milton A., and Glover B. Triplett. 1986. No-tillage and surface-tillage agriculture : the tillage revolution. New York, Wiley. ISBN 978-0-471-88410-1
- Troeh, Frederick R., J. Arthur Hobbs, Roy L. Donahue. 1991. Soil and water conservation for productivity and environmental protection, 2nd ed. Englewood Cliffs, N.J., Prentice-Hall. ISBN 978-0-13-096807-4
- Soil Science of America. 2009. Glossary of Soil Science Terms. [Online]. Available at https://www.soils.org/publications/soils-glossary (28 September 2009; verified 28 September 2009). Soil Science of America, Madison, WI.
- No-Plow Farmers Save Our Soil
- I will teach the world farming without oil
Further reading 
- Brady, Nyle C.; R.R. Weil (2002). The nature and property of soils, 13th edition. New Jersey: Prentice Hall. ISBN 0-13-016763-0.