Tillage
Tillage is the agricultural preparation of the soil by ploughing, ripping, or turning it. Tillage can also mean the land that is tilled. There are two types of tillage: primary and secondary tillage.
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Tillage systems
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 plow, disk, and/or chisel plow. After Moldboard plowing, a disk is often used to break clods. Then a finisher with a harrow, rolling basket, and cutter can be used to prepare the seed bed. There are many variations.
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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 effect the amount of residue.
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; it also warms the soil, enabling the next year’s crop to be planted earlier in the spring. 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.
- No-till
- Strip-Till
- Mulch-Till
- Ridge-Till
Purposes Of Tillage
- Ploughing loosens and aerates the soil which in turn facilitates deeper penetration of roots. A drawback is the compaction of the lower layers of soil.
- It helps in the growth of microorganisms present in the soil and thus, maintains the fertility of the soil. It is debatable whether worms benefit or suffer from tillage.
- It helps in the mixing of organic matter(humus)and nutrients evenly throughout the soil.
- It is used for destroying weeds.
General comments
- The type of implement makes the most difference but other factors can have an effect. The table in this publication gives some idea of the amount of residue that might be left with different tillage operations.
- The greater the speeds with which you move some tillage implements (disks and chisel plows), the more intensive the tillage (ie., 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.
- The reason the percent residue is used to define tillage systems is that the amount of crop residue impacts the amount of soil loss due to erosion. This graph demonstrates the amount of soil that might be expected to be lost with different amounts of crop residue.
- Look at this reference to see how to measure crop residues.
- In the same reference as above you can see what different amounts of corn and soybean residue look like.
- See Soybean management practices to see what types of tillage are currently recommended for Soybean Production.
Types of tillage systems in the USA
(Broken links)
- Click here to see the distribution tillage systems across the United States in 1995.
- Click here to see the acres of tilled land in the United States.
- Here you can see the number of conservation tillage acres.
- More maps can be found here
Definitions
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. It can be done by a using various combinations of equipment: plough, disk plough, harrow, dibble, hoe, shovel, rotary tillers, subsoiler, ridge or bed forming tillers, roller.
Weed plants (seeds, tubers, etc.) may be exhausted by repeated tilling. The weeds expend energy to reach the surface, and then get turned into the soil by tilling. The cycle is repeated until the weeds are dead.
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 plough 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 Clydesdale could work. The steel plough 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, genetically modified crops 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 (although it does require the use of pesticides). Most organic farming tends to require extensive tilling, as did most farming throughout history, although researchers are investigating farming in polyculture that would eliminate the need for both tillage and pesticides, such as no-dig gardening.
See also
- TERON (Tillage erosion)
External Natural Resource Conservation Service (NRCS) links
Other external links
For 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.