This article needs additional citations for verification .(March 2009) |
A disc harrow is a harrow whose cutting edges are a row of concave metal discs, which may be scalloped or set at an oblique angle. It is an agricultural implement that is used to till the soil where crops are to be planted. It is also used to chop up unwanted weeds or crop residue.
It consists of many carbon steel discs, and sometimes longer-lasting boron steel discs, which have many varying concavities and disc blade sizes and spacing (the choices of the latter being determined by the final result required in a given soil type) and which are arranged into two sections ("offset disc harrow") or four sections ("tandem disc harrow"). When viewed from above, the four sections would appear to form an "X" which has been flattened to be wider than it is tall. The discs are also offset so that they are not parallel with the overall direction of the implement. This arrangement ensures that the discs will repeatedly slice any ground to which they are applied, in order to optimize the result. The concavity of the discs as well as their offset angle causes them to loosen and lift the soil that they cut.
A discer is an evolved form of a disc harrow, more suitable to Saskatchewan prairies, where it was developed in the 1940s. It does not leave ridging and it is lighter to pull, so it can be made bigger. After the 1980s their domination started to fade. [1]
In various regions of the United States, farmers call these implements just discs (or disks), and they reserve the word harrow for the lighter types of harrow, such as chain and tooth harrows. Therefore, in these regions, the phrase "plowing, disking, and harrowing" refers to three separate tillage steps. This is not any official distinction but is how farmers tend to speak.
It is also common, at least in the United States, to consider disc plows to be a separate class of implement from discs (disc harrows). The first is a true plow, which does primary tillage and leaves behind a rough surface, whereas the second is a secondary tillage tool.
Before invention of the modern tractor, disc harrows typically consisted of two sections, which were horse-drawn and had no hydraulic power. These harrows were often adjustable so that the discs could be changed from their offset position. Straightening the discs allowed for transport without ripping up the ground; also, they were not as difficult to pull. Overuse of disc harrows in the High Plains of the United States in the early 20th century may have contributed to the "Dust Bowl".
Modern disc harrows are tractor-driven and are raised either by a three-point lift or hydraulically by wheels. The large ones have side sections that can be raised vertically or that fold up to allow easier road transport or to provide better storage configurations.
Primary heavy duty disc harrows of 265 to 1,000 pounds (120 to 454 kg) per disc are mainly used to break up virgin land, to chop material/residue, and to incorporate it into the top soil. Lighter secondary disc harrows help completely incorporate residue left by a primary disc harrow, eliminate clumps, and loosen the remaining packed soil. The notched disc blades chop up stover left from previous crops, such as cornstalks. Disc harrows incorporate remaining residue into the top soil, promoting the rapid decay of the dead plant material. Applying fertilizer onto residue on the surface of the soil results in much of the applied nitrogen being tied up by residual plant material; therefore it is not available to germinating seeds. Disc harrows are also generally used prior to plowing in order to make the land easier to manage and work after plowing. Applying a disc harrow before plowing can also reduce clogging and allow more complete turning of the soil during plowing.
A disc harrow is the preferred method of incorporating both agricultural lime (either dolomitic or calcitic lime) and agricultural gypsum, and disc harrowing achieves a 50/50 mix with the soil when set correctly, thereby reducing acid saturation in the top soil and so promoting strong, healthy root development. Lime does not move in the soil, and this poses a critical challenge to sustainable zero-till farming, especially considering that chemical fertilizers are generally used by farmers around the world.
In the event of a wildfire, farmers will often use a disc harrow to quickly create a firebreak between fields or around structures by circling a structure or a field, thereby tilling under flammable stubble, stover, or residue to deprive the advancing fire of fuel.
Once worn down too small to be of further use in harrows, the hardened steel discs have been adapted to form the blades of hand tools for wildland firefighters, farmers, and trail-building crews.[ citation needed ]
The heavy duty disc with large diameter disc blades of 26", 28", 30", 32", 36", and 40", and with increased disc spacings of 10", 14", and 18" are the primary tillage tools that are used to break virgin ground, to incorporate residue into the soil in preparation for a ripper / subsoiler, and to break up a compacted soil in order to increase soil aeration and to promote soil permeability in lower levels of the soil profile. Prior to a planting operation, a secondary disc harrow with narrow disc spacing of 8", 9", and even 10" with disc sizes ranging from 20", 22", 24", to 26" can be used. Other similar secondary tillage tine implements or rotary harrows are also widely used. When choosing secondary tillage equipment, soil type as well as soil moisture content at the time must be considered. Lighter secondary disc harrows are primarily used to break down soil clods into smaller pieces. By so doing, water penetrates more easily into the soil, soil aeration is increased, and the activity of soil biota is enhanced; the final result is a seed bed that is suitable for planting.
A plough or plow is a farm tool for loosening or turning the soil before sowing seed or planting. Ploughs were traditionally drawn by oxen and horses but in modern farms are drawn by tractors. A plough may have a wooden, iron or steel frame with a blade attached to cut and loosen the soil. It has been fundamental to farming for most of history. The earliest ploughs had no wheels; such a plough was known to the Romans as an aratrum. Celtic peoples first came to use wheeled ploughs in the Roman era.
Tillage is the agricultural preparation of soil by mechanical agitation of various types, such as digging, stirring, and overturning. Examples of human-powered tilling methods using hand tools include shoveling, picking, mattock work, hoeing, and raking. Examples of draft-animal-powered or mechanized work include ploughing, rototilling, rolling with cultipackers or other rollers, harrowing, and cultivating with cultivator shanks (teeth).
Crop rotation is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. This practice reduces the reliance of crops on one set of nutrients, pest and weed pressure, along with the probability of developing resistant pests and weeds.
In agriculture, a harrow is a farm implement used for surface tillage. It is used after ploughing for breaking up and smoothing out the surface of the soil. The purpose of harrowing is to break up clods and to provide a soil structure, called tilth, that is suitable for planting seeds. Coarser harrowing may also be used to remove weeds and to cover seed after sowing.
The stale seed bed or false seed bed method is a weed control technique used at both the farm and garden scales. In this that the young weeds can then be easily eliminated. By destroying them early, the farmer or gardener eliminates most of that season's annual weeds, which reduces their labor and improves their crop yields.
In agriculture, a green manure is a crop specifically cultivated to be incorporated into the soil while still green. Typically, the green manure's biomass is incorporated with a plow or disk, as is often done with (brown) manure. The primary goal is to add organic matter to the soil for its benefits. Green manuring is often used with legume crops to add nitrogen to the soil for following crops, especially in organic farming, but is also used in conventional farming.
Dryland farming and dry farming encompass specific agricultural techniques for the non-irrigated cultivation of crops. Dryland farming is associated with drylands, areas characterized by a cool wet season followed by a warm dry season. They are also associated with arid conditions, areas prone to drought and those having scarce water resources.
No-till farming is an agricultural technique for growing crops or pasture without disturbing the soil through tillage. No-till farming decreases the amount of soil erosion tillage causes in certain soils, especially in sandy and dry soils on sloping terrain. Other possible benefits include an increase in the amount of water that infiltrates into the soil, soil retention of organic matter, and nutrient cycling. These methods may increase the amount and variety of life in and on the soil. While conventional no-tillage systems use herbicides to control weeds, organic systems use a combination of strategies, such as planting cover crops as mulch to suppress weeds.
A seed drill is a device used in agriculture that sows seeds for crops by positioning them in the soil and burying them to a specific depth while being dragged by a tractor. This ensures that seeds will be distributed evenly.
Tilth is a physical condition of soil, especially in relation to its suitability for planting or growing a crop. Factors that determine tilth include the formation and stability of aggregated soil particles, moisture content, degree of aeration, soil biota, rate of water infiltration and drainage. Tilth can change rapidly, depending on environmental factors such as changes in moisture, tillage and soil amendments. The objective of tillage is to improve tilth, thereby increasing crop production; in the long term, however, conventional tillage, especially plowing, often has the opposite effect, causing the soil carbon sponge to oxidize, break down and become compacted.
Soil conservation is the prevention of loss of the topmost layer of the soil from erosion or prevention of reduced fertility caused by over usage, acidification, salinization or other chemical soil contamination.
A cultivator is a piece of agricultural equipment used for secondary tillage. One sense of the name refers to frames with teeth that pierce the soil as they are dragged through it linearly. It also refers to machines that use the rotary motion of disks or teeth to accomplish a similar result. The rotary tiller is a principal example.
A subsoiler or flat lifter is a tractor-mounted farm implement used for deep tillage, loosening and breaking up soil at depths below the levels worked by moldboard ploughs, disc harrows, or rototillers. Most such tools will break up and turn over surface soil to a depth of 15–20 cm (6–8 in), whereas a subsoiler will break up and loosen soil to twice those depths.
Strip-till is a conservation system that uses a minimum tillage. It combines the soil drying and warming benefits of conventional tillage with the soil-protecting advantages of no-till by disturbing only the portion of the soil that is to contain the seed row. This type of tillage is performed with special equipment and can require the farmer to make multiple trips, depending on the strip-till implement used, and field conditions. Each row that has been strip-tilled is usually about eight to ten inches wide.
The term cropping system refers to the crops, crop sequences and management techniques used on a particular agricultural field over a period of years. It includes all spatial and temporal aspects of managing an agricultural system. Historically, cropping systems have been designed to maximise yield, but modern agriculture is increasingly concerned with promoting environmental sustainability in cropping systems.
Agricultural machinery relates to the mechanical structures and devices used in farming or other agriculture. There are many types of such equipment, from hand tools and power tools to tractors and the countless kinds of farm implements that they tow or operate. Diverse arrays of equipment are used in both organic and nonorganic farming. Especially since the advent of mechanised agriculture, agricultural machinery is an indispensable part of how the world is fed. Agricultural machinery can be regarded as part of wider agricultural automation technologies, which includes the more advanced digital equipment and robotics. While agricultural robots have the potential to automate the three key steps involved in any agricultural operation, conventional motorized machinery is used principally to automate only the performing step where diagnosis and decision-making are conducted by humans based on observations and experience.
Soil management is the application of operations, practices, and treatments to protect soil and enhance its performance. It includes soil conservation, soil amendment, and optimal soil health. In agriculture, some amount of soil management is needed both in nonorganic and organic types to prevent agricultural land from becoming poorly productive over decades. Organic farming in particular emphasizes optimal soil management, because it uses soil health as the exclusive or nearly exclusive source of its fertilization and pest control.
Harrows, whether spring tooth, spike tooth or disc harrows can have a drag connection or have a 3 point mounting. A drag harrow is pulled and cannot be backed up. Three point implements can be raised and lowered hydraulicly and maneuvered more easily. A spring-tooth harrowis a type of harrow, and specifically a type of tine harrow. It uses many flexible iron teeth mounted in rows to loosen the soil before planting.
Emerging in North America in the 1970s and 1980s, vertical tillage (VT) is a system of principles and guidelines similar to conservation agriculture (CA) in that it aims to improve soil health, increase water infiltration and decrease soil erosion and compaction. With varying degrees of soil movement, it aims to not invert the soil and keep residue on the surface where it protects the soil. It usually includes small forward-facing discs that limit soil inversion and slices the residue for faster decomposition and to get a seeder or planter into the heavy residue-laden fields. Many times it also includes a deep ripping tool for breaking up hard pans and compaction created from traditional tillage implements and heavy equipment like large tractors and combine harvesters.
This glossary of agriculture is a list of definitions of terms and concepts used in agriculture, its sub-disciplines, and related fields. For other glossaries relevant to agricultural science, see Glossary of biology, Glossary of ecology, Glossary of environmental science, and Glossary of botanical terms.
Media related to Disk harrows at Wikimedia Commons