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Tillage

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 (overturning with moldboards or chiseling with chisel shanks), rototilling, rolling with cultipackers or other rollers, harrowing, and cultivating with cultivator shanks (teeth).

Tillage that is deeper and more thorough is classified as primary, and tillage that is shallower and sometimes more selective of location is 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. Within agriculture, both can refer to any kind of soil agitation. 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.

Definitions
Primary tillage loosens the soil and mixes in fertilizer 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 seedbed 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 two 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
Tilling was first performed via human labor, sometimes involving slaves. Hoofed animals could also be used to till soil by trampling, in addition to pigs, whose natural instincts are to root the ground regularly if allowed to. The wooden plow was then invented. (It is difficult to pinpoint the exact date of its invention. However, the earliest evidence of plow usage dates back to around 4000 BCE in Mesopotamia (modern-day Iraq ) . It could be pulled with human labor, or by mule, ox, elephant, water buffalo, or a similar sturdy animal. Horses are generally unsuitable, though breeds such as the Clydesdale were bred as draft animals.

Tilling could at times be very labor-intensive. This aspect is discussed in the 16th-century French agronomic text written by Charles Estienne:

"A raw, rough, and tough soil is hard to till and will neither bring forth corn, nor any other thing without great labor, however the seasons be temperate in moisture and dryness... you must labor it most exquisitely, harrow it and manure it very oft with great store of dung, so you shall make it better... but especially desire that they may not be watered with rain, for water is as good as poison to them."

The popularity of tillage as an agricultural technique in early modern times had to do with theories about plant biology proposed by European thinkers. In 1731, English writer Jethro Tull published the book "Horse-Hoeing Husbandry: An Essay on the Principles of Vegetation and Tillage," which argued that soil needed to be pulverized into fine powder for plants to make use of it. Tull believed that, since water, air, and heat were clearly not the primary substance of a plant, plants were made of earth, and thus had to consume very small pieces of earth as food. Tull wrote that each subsequent tillage of the soil would increase its fertility, and that it was impossible to till the soil too much. However, scientific observation has shown that the opposite is true; tillage causes soil to lose structural qualities that allow plant roots, water, and nutrients to penetrate it, accelerates soil loss by erosion, and results in soil compaction.

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 made modern large-scale agriculture possible. However, the destruction of the prairie grasses and tillage of the fertile topsoil of the American Midwest caused the Dust Bowl, in which the soil was blown away and stirred up into dust storms that blackened the sky. This prompted re-consideration of tillage techniques, but in the United States as of 2019, 3 trillion pounds of soil were estimated to be lost due to erosion while adoption of improved techniques for controlling erosion are still not widespread. In the mid 1930s Frank and Herbert Petty of Doncaster, Victoria, Australia developed the Petty Plough. This steerable plough could be pulled by either two horses or a tractor and the disc wheels could be steered in unison, or separately allowing the operator to plough the center of rows as well as between and around orchard trees.

Primary and secondary tillage
Primary tillage is usually conducted after the last harvest, when the soil is wet enough to allow plowing but also allows good traction. Some soil types can be plowed dry. The objective of primary tillage is to attain a reasonable depth of soft soil, incorporate crop residues, kill weeds, and to aerate the soil. Secondary tillage is any subsequent tillage, to incorporate fertilizers, reduce the soil to a finer tilth, level the surface, or control weeds.

Reduced tillage
Reduced tillage leaves between 15 and 30% crop 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 leaves less than 15% crop residue cover or less than 500 pounds per acre (560 kg/ha) of small grain residue. This type of tillage is often referred to as conventional tillage, but as conservational tillage is now more widely used than intensive tillage (in the United States), it is often not appropriate to refer to this type of tillage as conventional. Intensive tillage often involves multiple operations with implements such as a mold board, disk, or chisel plow. After this, 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 leaves at least 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. Additionally, conservation tillage has been found to benefit predatory arthropods that can enhance pest control. Conservation tillage also benefits farmers by reducing fuel consumption and soil compaction. By reducing the number of times the farmer travels over the field, significant savings in fuel and labor are made.

Conservation tillage is used on over 370 million acres, mostly in South America, Oceania and North America. In most years since 1997, conservation tillage was used in US cropland more than intensive or reduced tillage.

However, conservation tillage delays 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 – plows, disks, et cetera are not used. Aims for 100% ground cover.
 * Strip-till – Narrow strips are tilled where seeds will be planted, leaving the soil in between the rows untilled.
 * Mulch-till - Soil is covered with mulch to conserve heat and moisture. 100% soil disturbance.
 * Rotational tillage – Tilling the soil every two years or less often (every other year, or every third year, etc.).
 * Ridge-till

Zone tillage
Zone tillage is a form of modified deep tillage in which only narrow strips are tilled, leaving soil in between the rows untilled. This type of tillage agitates the soil to help reduce soil compaction problems and to improve internal soil drainage. It is designed to only disrupt the soil in a narrow strip directly below the crop row. In comparison to no-till, which relies on the previous year's plant residue to protect the soil and aids in postponement of the warming of the soil and crop growth in Northern climates, zone tillage produces a strip approximately five inches wide that simultaneously breaks up plow pans, assists in warming the soil and helps to prepare a seedbed. When combined with cover crops, zone tillage helps replace lost organic matter, slows the deterioration of the soil, improves soil drainage, increases soil water and nutrient holding capacity, and allows necessary soil organisms to survive.

It has been successfully used on farms in the Midwest and West of the USA for over 40 years, and is currently used on more than 36% of the U.S. farmland. Some specific states where zone tillage is currently in practice are Pennsylvania, Connecticut, Minnesota, Indiana, Wisconsin, and Illinois.

Its use in the USA's Northern Corn Belt states lacks consistent yield results; however, there is still interest in deep tillage within agriculture. In areas that are not well-drained, deep tillage may be used as an alternative to installing more expensive tile drainage.

Positive
Plowing:
 * Loosens and aerates the top layer of soil or horizon A, which facilitates planting the crop.
 * Helps mix harvest residue, organic matter (humus), and nutrients evenly into the soil.
 * Mechanically destroys weeds.
 * Dries the soil before seeding (in wetter climates, tillage aids in keeping the soil drier).
 * When done in autumn, helps exposed soil crumble over winter through frosting and defrosting, which helps prepare a smooth surface for spring planting.
 * Can reduce infestations of slugs, cut worms, army worms, and harmful insects as they are attracted by leftover residues from former crops.
 * Reduces the risk of crop diseases which can be harbored in surface residues.

Negative

 * Dries the soil before seeding.
 * Soil loses nutrients, like nitrogen and fertilizer, and its ability to store water.
 * Decreases the water infiltration rate of soil. (Results in more runoff and erosion as the soil absorbs water more slowly than before)
 * Tilling the soil results in dislodging the cohesiveness of the soil particles, thereby inducing erosion.
 * Chemical runoff.
 * Reduces organic matter in the soil.
 * Reduces microbes, earthworms, ants, etc.
 * Destroys soil aggregates.
 * Compaction of the soil, also known as a tillage pan.
 * Eutrophication (nutrient runoff into a body of water).

Archaeology
Tilling can damage ancient structures such as long barrows. In the UK, half of the long barrows in Gloucestershire and almost all the burial mounds in Essex have been damaged. According to English Heritage in 2003, ploughing with modern powerful tractors had done as much damage in the last six decades as traditional farming did in the previous six centuries.

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.

Alternatives
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.

Site preparation of forest land
Site preparation is any of various treatments applied to a site to ready it for seeding or planting. The purpose is to facilitate the regeneration of that site by the chosen method. Site preparation may be designed to achieve, singly or in any combination: improved access, by reducing or rearranging slash, and amelioration of adverse forest floor, soil, vegetation, or other biotic factors. Site preparation is undertaken to ameliorate one or more constraints that would otherwise be likely to thwart the objectives of management. A valuable bibliography on the effects of soil temperature and site preparation on subalpine and boreal tree species has been prepared by McKinnon et al. (2002).

Site preparation is the work that is done before a forest area is regenerated. Some types of site preparation are burning.

Burning
Broadcast burning is commonly used to prepare clearcut sites for planting, e.g., in central British Columbia, and in the temperate region of North America generally.

Prescribed burning is carried out primarily for slash hazard reduction and to improve site conditions for regeneration; all or some of the following benefits may accrue:

 * a) Reduction of logging slash, plant competition, and humus prior to direct seeding, planting, scarifying or in anticipation of natural seeding in partially cut stands or in connection with seed-tree systems.

 * b) Reduction or elimination of unwanted forest cover prior to planting or seeding, or prior to preliminary scarification thereto.

 * c) Reduction of humus on cold, moist sites to favour regeneration.

 * d) Reduction or elimination of slash, grass, or brush fuels from strategic areas around forested land to reduce the chances of damage by wildfire.

Prescribed burning for preparing sites for direct seeding was tried on a few occasions in Ontario, but none of the burns was hot enough to produce a seedbed that was adequate without supplementary mechanical site preparation.

Changes in soil chemical properties associated with burning include significantly increased pH, which Macadam (1987) in the Sub-boreal Spruce Zone of central British Columbia found persisting more than a year after the burn. Average fuel consumption was 20 to 24 t/ha and the forest floor depth was reduced by 28% to 36%. The increases correlated well with the amounts of slash (both total and ≥7 cm diameter) consumed. The change in pH depends on the severity of the burn and the amount consumed; the increase can be as much as 2 units, a 100-fold change. Deficiencies of copper and iron in the foliage of white spruce on burned clearcuts in central British Columbia might be attributable to elevated pH levels.

Even a broadcast slash fire in a clearcut does not give a uniform burn over the whole area. Tarrant (1954), for instance, found only 4% of a 140-ha slash burn had burned severely, 47% had burned lightly, and 49% was unburned. Burning after windrowing obviously accentuates the subsequent heterogeneity.

Marked increases in exchangeable calcium also correlated with the amount of slash at least 7 cm in diameter consumed. Phosphorus availability also increased, both in the forest floor and in the 0 cm to 15 cm mineral soil layer, and the increase was still evident, albeit somewhat diminished, 21 months after burning. However, in another study in the same Sub-boreal Spruce Zone found that although it increased immediately after the burn, phosphorus availability had dropped to below pre-burn levels within 9 months.

Nitrogen will be lost from the site by burning, though concentrations in remaining forest floor were found by Macadam (1987) to have increased in two out of six plots, the others showing decreases. Nutrient losses may be outweighed, at least in the short term, by improved soil microclimate through the reduced thickness of forest floor where low soil temperatures are a limiting factor.

The Picea/Abies forests of the Alberta foothills are often characterized by deep accumulations of organic matter on the soil surface and cold soil temperatures, both of which make reforestation difficult and result in a general deterioration in site productivity; Endean and Johnstone (1974) describe experiments to test prescribed burning as a means of seedbed preparation and site amelioration on representative clear-felled Picea/Abies areas. Results showed that, in general, prescribed burning did not reduce organic layers satisfactorily, nor did it increase soil temperature, on the sites tested. Increases in seedling establishment, survival, and growth on the burned sites were probably the result of slight reductions in the depth of the organic layer, minor increases in soil temperature, and marked improvements in the efficiency of the planting crews. Results also suggested that the process of site deterioration has not been reversed by the burning treatments applied.

Ameliorative intervention
Slash weight (the oven-dry weight of the entire crown and that portion of the stem less than four inches in diameter) and size distribution are major factors influencing the forest fire hazard on harvested sites. Forest managers interested in the application of prescribed burning for hazard reduction and silviculture, were shown a method for quantifying the slash load by Kiil (1968). In west-central Alberta, he felled, measured, and weighed 60 white spruce, graphed (a) slash weight per merchantable unit volume against diameter at breast height (dbh), and (b) weight of fine slash (<1.27 cm) also against dbh, and produced a table of slash weight and size distribution on one acre of a hypothetical stand of white spruce. When the diameter distribution of a stand is unknown, an estimate of slash weight and size distribution can be obtained from average stand diameter, number of trees per unit area, and merchantable cubic foot volume. The sample trees in Kiil's study had full symmetrical crowns. Densely growing trees with short and often irregular crowns would probably be overestimated; open-grown trees with long crowns would probably be underestimated.

The need to provide shade for young outplants of Engelmann spruce in the high Rocky Mountains is emphasized by the U.S. Forest Service. Acceptable planting spots are defined as microsites on the north and east sides of down logs, stumps, or slash, and lying in the shadow cast by such material. Where the objectives of management specify more uniform spacing, or higher densities, than obtainable from an existing distribution of shade-providing material, redistribution or importing of such material has been undertaken.

Access
Site preparation on some sites might be done simply to facilitate access by planters, or to improve access and increase the number or distribution of microsites suitable for planting or seeding.

Wang et al. (2000) determined field performance of white and black spruces 8 and 9 years after outplanting on boreal mixedwood sites following site preparation (Donaren disc trenching versus no trenching) in 2 plantation types (open versus sheltered) in southeastern Manitoba. Donaren trenching slightly reduced the mortality of black spruce but significantly increased the mortality of white spruce. Significant difference in height was found between open and sheltered plantations for black spruce but not for white spruce, and root collar diameter in sheltered plantations was significantly larger than in open plantations for black spruce but not for white spruce. Black spruce open plantation had significantly smaller volume (97 cm3) compared with black spruce sheltered (210 cm3), as well as white spruce open (175 cm3) and sheltered (229 cm3) plantations. White spruce open plantations also had smaller volume than white spruce sheltered plantations. For transplant stock, strip plantations had a significantly higher volume (329 cm3) than open plantations (204 cm3). Wang et al. (2000) recommended that sheltered plantation site preparation should be used.

Mechanical
Up to 1970, no "sophisticated" site preparation equipment had become operational in Ontario, but the need for more efficacious and versatile equipment was increasingly recognized. By this time, improvements were being made to equipment originally developed by field staff, and field testing of equipment from other sources was increasing.

According to J. Hall (1970), in Ontario at least, the most widely used site preparation technique was post-harvest mechanical scarification by equipment front-mounted on a bulldozer (blade, rake, V-plow, or teeth), or dragged behind a tractor (Imsett or S.F.I. scarifier, or rolling chopper). Drag type units designed and constructed by Ontario's Department of Lands and Forests used anchor chain or tractor pads separately or in combination, or were finned steel drums or barrels of various sizes and used in sets alone or combined with tractor pad or anchor chain units.

J. Hall's (1970) report on the state of site preparation in Ontario noted that blades and rakes were found to be well suited to post-cut scarification in tolerant hardwood stands for natural regeneration of yellow birch. Plows were most effective for treating dense brush prior to planting, often in conjunction with a planting machine. Scarifying teeth, e.g., Young's teeth, were sometimes used to prepare sites for planting, but their most effective use was found to be preparing sites for seeding, particularly in backlog areas carrying light brush and dense herbaceous growth. Rolling choppers found application in treating heavy brush but could be used only on stone-free soils. Finned drums were commonly used on jack pine–spruce cutovers on fresh brushy sites with a deep duff layer and heavy slash, and they needed to be teamed with a tractor pad unit to secure good distribution of the slash. The S.F.I. scarifier, after strengthening, had been "quite successful" for 2 years, promising trials were under way with the cone scarifier and barrel ring scarifier, and development had begun on a new flail scarifier for use on sites with shallow, rocky soils. Recognition of the need to become more effective and efficient in site preparation led the Ontario Department of Lands and Forests to adopt the policy of seeking and obtaining for field testing new equipment from Scandinavia and elsewhere that seemed to hold promise for Ontario conditions, primarily in the north. Thus, testing was begun of the Brackekultivator from Sweden and the Vako-Visko rotary furrower from Finland.

Mounding
Site preparation treatments that create raised planting spots have commonly improved outplant performance on sites subject to low soil temperature and excess soil moisture. Mounding can certainly have a big influence on soil temperature. Draper et al. (1985), for instance, documented this as well as the effect it had on root growth of outplants (Table 30).

The mounds warmed up quickest, and at soil depths of 0.5 cm and 10 cm averaged 10 and 7 °C higher, respectively, than in the control. On sunny days, daytime surface temperature maxima on the mound and organic mat reached 25 °C to 60 °C, depending on soil wetness and shading. Mounds reached mean soil temperatures of 10 °C at 10 cm depth 5 days after planting, but the control did not reach that temperature until 58 days after planting. During the first growing season, mounds had 3 times as many days with a mean soil temperature greater than 10 °C than did the control microsites.

Draper et al.'s (1985) mounds received 5 times the amount of photosynthetically active radiation (PAR) summed over all sampled microsites throughout the first growing season; the control treatment consistently received about 14% of daily background PAR, while mounds received over 70%. By November, fall frosts had reduced shading, eliminating the differential. Quite apart from its effect on temperature, incident radiation is also important photosynthetically. The average control microsite was exposed to levels of light above the compensation point for only 3 hours, i.e., one-quarter of the daily light period, whereas mounds received light above the compensation point for 11 hours, i.e., 86% of the same daily period. Assuming that incident light in the 100–600 μE/m2/s intensity range is the most important for photosynthesis, the mounds received over 4 times the total daily light energy that reached the control microsites.

Orientation of linear site preparation
With linear site preparation, orientation is sometimes dictated by topography or other considerations, but the orientation can often be chosen. It can make a difference. A disk-trenching experiment in the Sub-boreal Spruce Zone in interior British Columbia investigated the effect on growth of young outplants (lodgepole pine) in 13 microsite planting positions: berm, hinge, and trench in each of north, south, east, and west aspects, as well as in untreated locations between the furrows. Tenth-year stem volumes of trees on south-, east-, and west-facing microsites were significantly greater than those of trees on north-facing and untreated microsites. However, planting spot selection was seen to be more important overall than trench orientation.

In a Minnesota study, the N–S strips accumulated more snow but snow melted faster than on E–W strips in the first year after felling. Snow-melt was faster on strips near the centre of the strip-felled area than on border strips adjoining the intact stand. The strips, 50 feet (15.24 m) wide, alternating with uncut strips 16 feet (4.88 m) wide, were felled in a Pinus resinosa stand, aged 90 to 100 years.

title: Tillage


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Threshing machine

A threshing machine or a thresher is a piece of farm equipment that separates grain seed from the stalks and husks. It does so by beating the plant to make the seeds fall out. Before such machines were developed, threshing was done by hand with flails: such hand threshing was very laborious and time-consuming, taking about one-quarter of agricultural labour by the 18th century. Mechanization of this process removed a substantial amount of drudgery from farm labour. The first threshing machine was invented circa 1786 by the Scottish engineer Andrew Meikle, and the subsequent adoption of such machines was one of the earlier examples of the mechanization of agriculture. During the 19th century, threshers and mechanical reapers and reaper-binders gradually became widespread and made grain production much less laborious.

Separate reaper-binders and threshers have largely been replaced by machines that combine all of their functions, that is combine harvesters or combines. However, the simpler machines remain important as appropriate technology in low-capital farming contexts, both in developing countries and in developed countries on small farms that strive for especially high levels of self-sufficiency. For example, pedal-powered threshers are a low-cost option, and some Amish sects use horse-drawn binders and old-style threshers.

As the verb thresh is cognate with the verb thrash (and synonymous in the grain-beating sense), the names thrashing machine and thrasher are (less common) alternate forms.

Early social impacts

The Swing Riots in the UK were partly a result of the threshing machine. Following years of war, high taxes and low wages, farm labourers finally revolted in 1830. They had faced unemployment for years, due to the widespread introduction of the threshing machine and the policy of enclosing fields. No longer were thousands of men needed to tend the crops; a few would suffice. With fewer jobs, lower wages and no prospects, the threshing machine was the final straw; it would place them on the brink of starvation. The Swing Rioters smashed threshing machines and threatened farmers who had them. The riots were dealt with very harshly. Nine of the rioters were hanged and a further 450 were transported to Australia.

Later adoption
Early threshing machines were hand-fed and horse-powered. Some were housed in a specially constructed building, a gin gang, which would be attached to a threshing barn. They were small by today's standards and were about the size of an upright piano. Later machines were steam-powered, driven by a portable engine or traction engine. Isaiah Jennings, a skilled inventor, created a small thresher that does not harm the straw in the process. In 1834, John Avery and Hiram Abial Pitts devised significant improvements to a machine that automatically threshes and separates grain from the chaff, freeing farmers from a slow and laborious process. Avery and Pitts were granted United States patent #542 on December 29, 1837.

John Ridley, an Australian inventor, also developed a threshing machine in South Australia in 1843.

The 1881 Household Cyclopedia said of Meikle's machine:

 * "Since the invention of this machine, Mr. Meikle and others have progressively introduced a variety of improvements, all tending to simplify the labour, and to augment the quantity of the work performed. When first erected, though the grain was equally well separated from the straw, yet as the whole of the straw, chaff, and grain, was indiscriminately thrown into a confused heap, the work could only with propriety be considered as half executed. By the addition of rakes, or shakers, and two pairs of fanners, all driven by the same machinery, the different processes of thrashing, shaking, and winnowing are now all at once performed, and the grain immediately prepared for the public market. When it is added, that the quantity of grain gained from the superior powers of the machine is fully equal to a twentieth part of the crop, and that, in some cases, the expense of thrashing and cleaning the grain is considerably less than what was formerly paid for cleaning it alone, the immense saving arising from the invention will at once be seen."

 * 1926 Threshing Machine.png"The expense of horse labour, from the increased value of the animal and the charge of his keeping, being an object of great importance, it is recommended that, upon all sizable farms, that is to say, where two hundred acres [800,000 m²], or upwards, of grain are sown, the machine should be worked by wind, unless where local circumstances afford the conveniency of water. Where coals are plenty and cheap, steam may be advantageously used for working the machine."

Steam-powered machines used belts connected to a traction engine; often both engine and thresher belonged to a contractor who toured the farms of a district. Steam remained a viable commercial option until the early post-WWII years.

In Europe and Americas
Modern-day combines harvesters (or simply combines) operate on the same principles and use the same components as the original threshing machines built in the 19th century. Combines also perform the reaping operation at the same time. The name combine is derived from the fact that the two steps are combined in a single machine. Also, most modern combines are self-powered (usually by a diesel engine) and self-propelled, although tractor-powered, pull-type combines models were offered by John Deere and Case International into the 1990s.

Today, as in the 19th century, threshing begins with a cylinder and concave. The cylinder has sharp serrated bars, and rotates at high speed (about 500 RPM) so that the bars beat against the entire plant as it is mechanically fed from the reaping equipment at the front of the combine to the gap between the concave and the rotating beater/cylinder. The concave is curved to match the curve of the cylinder, and the grain, now separated from the plant stalks falls immediately through grated openings in the concave as it is beaten. The motion of the rotating cylinder thrusts the remaining straw and chaff toward the rear of the machine.

Whilst the majority of the grain falls through the concave, the straw is carried by a set of "walkers" to the rear of the machine, allowing any grain and chaff still in the straw to fall below. Below the straw walkers, a fan blows a stream of air across the grain, removing dust and small bits of crushed plant material out of the back of the combine. The residues fall to the ground and occasionally are collected for other purposes, such as fodder.

The grain, either coming through the concave or the walkers, meets a set of sieves mounted on an assembly called a shoe, which is shaken mechanically. The top sieve has larger openings and serves to remove large pieces of chaff from the grain. The lower sieve separates clean grain, which falls through, from incompletely threshed pieces. The incompletely threshed grain is returned to the cylinder by means of a system of conveyors, where the process repeats.

Some threshing machines were equipped with a bagger, which invariably held two bags, one being filled, and the other being replaced with an empty. A worker called a sewer removed and replaced the bags, and sewed full bags shut with a needle and thread. Other threshing machines would discharge grain from a conveyor, for bagging by hand. Combines are equipped with a grain tank, which accumulates grain for deposit in a truck or wagon.

A large amount of chaff and straw would accumulate around a threshing machine, and several innovations, such as the air chaffer, were developed to deal with this. Combines generally chop and disperse straw as they move through the field, though the chopping is disabled when the straw is to be baled, and chaff collectors are sometimes used to prevent the dispersal of weed seed throughout a field.

The corn sheller was almost identical in design, with slight modifications to deal with the larger kernel size and presence of cobs. Modern-day combines can be adjusted to work with any grain crop and many unusual seed crops.

Both the older and modern machines require a good deal of effort to operate. The concave clearance, cylinder speed, fan velocity, sieve sizes, and feeding rate must be adjusted for crop conditions.

Another development in Asia
From the early 20th century, petrol or diesel-powered threshing machines, designed especially to thresh rice, the most important crop in Asia, have been developed along different lines to the modern combine.

Even after the combine was invented and became popular, a new compact-size thresher called a harvester, with wheels, still remains in use and at present it is available from a Japanese agricultural manufacturer. The compact-size machine is very convenient to handle in small terrace fields in mountain areas where a large machine, such as a combine, is not usable.

People there use this harvester with a modern compact binder.

Preservation
A number of older threshing machines have survived into preservation. They are often to be seen in operation at live steam festivals and traction engine rallies such as the Great Dorset Steam Fair in England, and the Western Minnesota Steam Threshers Reunion in northwest Minnesota.

Musical references
Irish songwriter John Duggan immortalised the threshing machine in the song "The Old Thrashing Mill". The song has been recorded by Foster and Allen and Brendan Shine.

On the Alan Lomax collection Songs of Seduction (Rounder Select, 2000), there is a bawdy Irish folk song called "The Thrashing Machine" sung by tinker Annie O'Neil, as recorded in the early 20th century.

In his film score for Of Mice and Men (1939) and consequently in his collection Music for the Movies (1942), American composer Aaron Copland titled a section of the score "Threshing Machines," to suit a scene in the Lewis Milestone film where Curley is threatening Slim over giving May a puppy, when many of the itinerant worker men are standing around or working on threshers.

In the song "Thrasher" from the album Rust Never Sleeps, Neil Young compares the modern threshing machine's technique of separating wheat from wheat stalks to the natural forces of time that separate close friends from one another.

Threshing machines appear in Twenty One Pilots' music video for the song "House of Gold".

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Threshing machine


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Moss, Norway

Moss is a coastal town and a municipality in Østfold county, Norway. The administrative centre of the municipality is the town of Moss. The city of Moss was established as a municipality on 1 January 1838 (see formannskapsdistrikt) and City in 1720. The rural municipality of Jeløy was merged with the city on 1 July 1943. The former municipality of Rygge was merged into it on January 1, 2020.

Its administrative district covers areas east of the town, such as the island of Dillingøy in the lake Vansjø. Parts of the town are located on the peninsula of Jeløy. The city of Moss has 30,723 inhabitants (2012).

Name
The Old Norse form of the name was Mors. It may be derived from an old root mer- which means to "divide" or "split".

The adjacent topography shares similar etymology:
 * Mosse-elva, Mosse-"marsh-river-border"+ elva (see elbe, elver, Old Norse for river). The name is thought to be very old and the meaning of it is not clear.
 * Mosse-sundet, Mosse-"marsh-river-border"+ sundet (Moss channel).
 * Mosse-herred, Mosse-"marsh-river-border"+ herred -"court" akin to hort(us,en), "garden," from PIE *ghr-ti-, from base *gher- "to grasp, enclose" (see yard) Actually "Moss county".

History
Archeological finds suggest that there were settlements in the area more than 7,000 years ago and continuously through the Iron Age, Viking Age, through to modern times. During the Viking era, the place was known as Varna (from the Old Norse vorn, or protection) and was the site of a cooperative for battleships held by local warlords on behalf of the king.

The first literary reference to the name Mo(u)ſs(ß) is from Bishop Eystein Aslaksson's Red book (NRA AM fol. 328) from 1396, and by then the town had become a commercial center with craftsmen and mills. By the 16th century, the town's port was significant enough to warrant its own customs official. Liquor distilleries became one of the dominant industries, and it was not until 1607, after the Reformation, that the town got its own church.

By 1700, Moss had become a hub for both ship and land traffic between Copenhagen and Christiania, and in 1704 Moss Jernverk (Moss Ironworks) was established just north of the city center. By 1720 it received its charter as a merchant town, with its own official. This may have had background in an important battle in 1716 that was fought in the town square in Moss in which Norwegian troops commanded by Vincent Budde prevailed over invading Swedish forces, sent by Charles XII to capture Akershus Fortress. In 1767 a local resident built a "pleasure pavilion" near the town, which survives as the Hotel Refsnes Gods.

In 1814, Moss became the site for the signing of the Convention of Moss, which effectively put an end to the Dano-Norwegian kingdom. This set the stage for economic development that has persisted to this day.

On the morning of 14 July 2006, a bolide exploded above the nearby town of Rygge - moments later, several stony meteorites fell over Moss. A number of meteorites were recovered by local residents and visiting meteorite hunters, which after analysis and classification, were found to be a rare type of carbonaceous chondrite.

Seal and coat-of-arms
Moss became a separate city in 1786 and received its first seal the same year. The seal showed a church under some clouds, placed within a circle. Above the circle were fasces, the late 19th century symbol of freedom. A later seal, dating from around 1829, shows the same composition, but with six birds flying around the church.

In the 1930s the city wanted to adopt a coat-of-arms and the birds were chosen as a possible symbol. The original birds were likely doves, a symbol of peace. In 1934, the idea of the crow was launched. The residents of Moss have long been referred to as crows. An old tale tells of a number of birds, thought to have been crows, swarming around the church spire due to a fire that started when lightning struck a birds' nest in the spire. The fire was quickly put out; birds became a motif in the city seal (and later coat-of-arms) for that reason.

The coat-of-arms was granted on 2 April 1954 and shows a yellow crow on a red background. It was designed by Christian Stenersen.

Norwegian lady statues
Moss and Virginia Beach, Virginia in the United States are sister cities. On Good Friday, 27 March 1891, the Norwegian bark Dictator, whose home port was Moss, was lost in the treacherous waters of the Graveyard of the Atlantic. The ship had been en route to England from Pensacola, Florida with a cargo of Georgia Pine lumber. After being caught and disabled in a storm, she was headed for port at Hampton Roads, Virginia to make repairs when she encountered another storm just off Virginia Beach.

Working in the high winds and seas, lifesaving crews from shore were able to save some of the 17 persons aboard. However, the pregnant wife of Captain J.M. Jorgensen, Johanne, and their 4-year-old son Carl were among the 7 persons who drowned.

The ship's wooden female figurehead had washed ashore. It was placed in a vertical position facing the ocean near the boardwalk as a memorial to those who died in the shipwreck. It was a landmark there for more than 60 years, but gradually became weathered and eroded.

In 1962, Norwegian sculptor Ørnulf Bast was commissioned to create two nine-foot bronze replicas of the original figurehead by the City of Moss. The Norwegian Lady Statues were unveiled on 22 September 1962. One was presented as a gift to Virginia Beach, and an exact duplicate was erected in Moss to unite the two sister cities. Each statue gives the appearance of facing the other across the Atlantic Ocean.

On 13 October 1995, Queen Sonja of Norway visited the Norwegian Lady statue in Virginia Beach, and placed memorial flowers.

Geography
Moss is located on the eastern shore of Oslofjord, 60 km south of Oslo. The municipality also includes some islands, like Jeløya. The Raet goes through the municipality. The area is forested lowland, the highest point is 140 m asl. 84% of the population is located in the town Moss.

Climate
Moss has a humid continental climate (Dfb), or a temperate oceanic climate (Cfb) if the original -3 °C threshold in the Köppen climate classification is used. The weather station at Moss Airport Rygge (40 m) started recording temperature in 1955. The all-time high 34.2 °C was recorded August 1982, and the all-time low -31.5 °C in February 1985. 10 of the record lows are from before 1990, and only the December record low is from after 2000. Rygge airport is located more inland and will have colder lows in winter and autumn than the town. The average date for first overnight freeze (below 0 °C) in autumn is October 7 (1981-2010 average) at Rygge.

Industry
The town is known for paper mills, as well as metalworks and other factories. Dillingøy is known as a place for alternative non-military civil service. Moss is mentioned since the Renaissance and was the site of the signing of the Convention of Moss in 1814, which solidified the union with Sweden. The headquarters of textile producer Helly Hansen were located in Moss until 2009. The maker of international hotel keycards, Trio Ving, also has their headquarters here.

Transport
The railway Østfold Line runs through Moss, stopping at Moss Station, which is the southern terminus of one service of the Oslo Commuter Rail and an intermediate stop for regional trains. Moss connects across the Oslofjord to Horten via the Moss–Horten Ferry. There are also bus-lines to Oslo Airport, Gardermoen, Gothenburg, Copenhagen, Oslo in addition to local bus lines. Moss port is one of the top 3 busiest container ports in Norway (measured in TEUs).

Health care
Together with Østfold Kalnes Hospital, Østfold Moss Hospital covers general health care services for the municipality. The hospital is a modern unit for planned operations. There is a large outpatient and inpatient activity in a number of disciplines, in the field of somatics and mental health care as well as an operation department for both inpatient and day surgery. There is an eye department, imaging services, blood sampling and blood bank and more. The municipality also has three health stations - City center, Bredsand and Kambo health stations.

Sport
Moss FK are the town's football club. They play in the First Division, and have played in the Norwegian Premier League as recently as 2002.

Notable people

 * people from Moss are known locally as "Mossinger"
 * Ari Behn (1972–2019), author and playwright; former husband of Princess Märtha Louise of Norway; brought up in Moss
 * Tina Bru (born 1986 in Moss), politician and government minister
 * Palle Rømer Fleischer (1781 in Moss – 1851), representative at the Norwegian Constitutional Assembly
 * Gregers Gram (1846 in Moss – 1929), Norwegian prime minister in Stockholm, 1889 to 1891
 * Christopher Hansteen (1822 in Moss – 1912), judge, associate justice on the Supreme Court of Norway, 1867 to 1905
 * Eyvind Hellstrøm (born 1948 in Moss), gourmet chef and TV personality
 * Knut Jacobsen (1910–1971), actor and costume designer
 * Gretha Kant (born 1945), politician, mayor of Moss, 1995 to 2003
 * Jorunn Kristiansen, Miss Norway 1959
 * David Menkin (born 1977 in Moss), film, TV and voice actor
 * Jon Michelet (1944 in Moss – 2018), novelist, author of crime novels, newspaper columns, and children's books
 * Grynet Molvig (born 1942 in Rygge), Norwegian actress and singer
 * Hanna Paulsberg (born 1987 in Rygge), jazz musician (tenor saxophone) and composer
 * Johan Scharffenberg (1869 in Moss – 1965), psychiatrist, politician, speaker, and writer
 * Per Schwenzen (1899 in Moss – 1984), writer of screenplays and librettos for operettas
 * Arild Sibbern (1785 in Rygge – 1863), representative at the Norwegian Constituent Assembly
 * Georg Sibbern (1816 in Rygge – 1901), prime minister of Norway 1858/61 and 1861/1871
 * Torgrim Sørnes (born 1956 in Moss), physician, historian, and author

Sports

 * Einar Jan Aas (born 1955 in Moss), former footballer with 35 caps for Norway
 * Agnete Carlsen (born 1971 in Moss), former footballer with 97 caps with Norway women
 * Erik Holtan (born 1969 in Moss), retired football goalkeeper with 330 club caps
 * Rune Pedersen (born 1963 in Moss), former football referee
 * Thomas Myhre (born 1973, grew up in Moss), retired football goalkeeper with 56 caps for Norway
 * Erland Johnsen (born 1967, grew up in Moss), retired footballer with 24 caps for Norway

Twin towns — Sister cities
The following cities are twinned with Moss:
 * 🇬🇹 Aguacatán, Guatemala
 * 🇮🇸 Blönduós, Iceland
 * 🇩🇰 Horsens, Denmark
 * 🇸🇪 Karlstad, Sweden
 * 🇫🇮 Nokia, Finland
 * 🇷🇺 Novgorod, Russia
 * 🇺🇸 Virginia Beach, Virginia, United States

Use of preposition with Moss
"In Moss" is translated i Moss. In the 1800s one said [on Moss] på Moss.

In popular culture

 * A traditional expression, [the hay scale at Moss] høyvekta på Moss, means "something that you can not trust".
 * Moss is known throughout Norway for the local "dish" "Pølse i Vaffel" - sausage in waffle. The dish consists of a Vienna Sausage served in a Scandinavian style waffle with ketchup and mustard. The dish was most likely created in the 1960s, but this is widely discussed. Eyvind Hellstrøm - who later became a Michelin-star chef - and his brother Jan are often referred to as the creators. Eyvind Hellstrøm has not denied this in interviews.

title: Moss, Norway


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Marl

Marl is an earthy material rich in carbonate minerals, clays, and silt. When hardened into rock, this becomes marlstone. It is formed in marine or freshwater environments, often through the activities of algae.

Marl makes up the lower part of the cliffs of Dover, and the Channel Tunnel follows these marl layers between France and the United Kingdom. Marl is also a common sediment in post-glacial lakes, such as the marl ponds of the northeastern United States.

Marl has been used as a soil conditioner and neutralizing agent for acid soil and in the manufacture of cement.

Description

Marl or marlstone is a carbonate-rich mud or mudstone which contains variable amounts of clays and silt. The term was originally loosely applied to a variety of materials, most of which occur as loose, earthy deposits consisting chiefly of an intimate mixture of clay and calcium carbonate, formed under freshwater conditions. These typically contain 35–65% clay and 65–35% carbonate. The term is today often used to describe indurated marine deposits and lacustrine (lake) sediments which more accurately should be named 'marlstone'.

Marlstone is an indurated (resists crumbling or powdering) rock of about the same composition as marl. This is more correctly described as an earthy or impure argillaceous limestone. It has a blocky subconchoidal fracture, and is less fissile than shale. The dominant carbonate mineral in most marls is calcite, but other carbonate minerals such as aragonite or dolomite may be present.

Glauconitic marl is marl containing pellets of glauconite, a clay mineral that gives the marl a green color. Glauconite is characteristic of sediments deposited in marine conditions.

Occurrences

The lower stratigraphic units of the chalk cliffs of Dover consist of a sequence of glauconitic marls followed by rhythmically banded limestone and marl layers. Such alternating cycles of chalk and marl are common in Cretaceous beds of northwestern Europe. The Channel Tunnel follows these marl layers between France and the United Kingdom. Upper Cretaceous cyclic sequences in Germany and marl–opal-rich Tortonian-Messinian strata in the Sorbas Basin related to multiple sea drawdown have been correlated with Milankovitch orbital forcing.

Marl as lacustrine sediment is common in post-glacial lake-bed sediments. Chara, a macroalga also known as stonewort, thrives in shallow lakes with high pH and alkalinity, where its stems and fruiting bodies become calcified. After the alga dies, the calcified stems and fruiting bodies break down into fine carbonate particles that mingle with silt and clay to produce marl. Marl ponds of the northeastern United States are often kettle ponds in areas of limestone bedrock that become poor in nutrients (oligotrophic) due to precipitation of essential phosphate. Normal pond life is unable to survive, and skeletons of freshwater molluscs such as Sphaerium and Planorbis accumulate as part of the bottom marl.

In Hungary, Buda Marl is found that was formed in the Upper Eocene era. It lies between layers of rock and soil and may be defined it as both "weak rock and strong soil."

Marl is the dominant rock type in the Vaca Muerta Formation in Argentina.

Economic geology
Marl has been used as a soil conditioner and neutralizing agent for acid soil and in the manufacture of Portland cement. Because some marls have a very low permeability, they have been exploited for construction of the Channel Tunnel between England and France and are being investigated for the storage of nuclear waste.

Historical use in agriculture
Marl is one of the oldest soil amendments used in agriculture. In addition to increasing available calcium, marl is valuable for improving soil structure and decreasing soil acidity and thereby making other nutrients more available. It was used sporadically in Britain beginning in prehistoric times and its use was mentioned by Pliny the Elder in the 1st century. Its more widespread use from the 16th century on contributed to the early modern agricultural revolution. However, the lack of a high-energy economy hindered its large-scale use until the Industrial Revolution.

Marl was used extensively in Britain, particularly in Lancashire, during the 18th century. The marl was normally extracted close to its point of use, so that almost every field had a marl pit, but some marl was transported greater distances by railroad. However, marl was gradually replaced by lime and imported mineral fertilizers early in the 19th century. A similar historical pattern was seen in Scotland.

Marl was one a few soil amendments available in limited quantities in the southern United States, where soils were generally poor in nutrients, prior to about 1840. By the late 19th century, marl was being mined on an industrial scale in New Jersey and was increasingly being used on a more scientific basis, with marl being classified by grade and the state geological survey publishing detailed chemical analyses.

Modern agricultural and aquacultural uses
Marl continues to be used for agriculture into the 21st century, though less frequently. The rate of application must be adjusted for the reduced content of calcium carbonate versus straight lime, expressed as the calcium carbonate equivalent. Because the carbonate in marl is predominantly calcium carbonate, magnesium deficiency may be seen in crops treated with marl if they are not also supplemented with magnesium.

Marl has been used in Pamlico Sound to provide a suitable artificial substrate for oysters in a reef-like environment.

Portland cement
Marl has been used in the manufacture of Portland cement. It is abundant and yields better physical and mechanical properties than metakaolin as a supplementary cementitious material and can be calcined at a considerably lower temperature.

Civil engineering
The Channel Tunnel was constructed in the West Melbury Marly Chalk, a geological formation containing marl beds. This formation was chosen because of its very low permeability, absence of chert, and lack of fissures found in overlying formations. The underlying Glauconitic Marl is easily recognizable in core samples and helped establish the right level for excavating the tunnel.

Marl soil has poor engineering properties, particularly when alternately wetted and dried. The soils can be stabilized by adding pozzolan (volcanic ash) to the soil.

Nuclear waste storage
Some marl beds have a very low permeability and are under consideration for use in the storage of nuclear waste. One such proposed storage site is the Wellenberg in central Switzerland.

Marl lakes

A marl lake is a lake whose bottom sediments include large deposits of marl. They are most often found in areas of recent glaciation and are characterized by alkaline water, rich in dissolved calcium carbonate, from which carbonate minerals are deposited.

Marl lakes have frequently been dredged or mined for marl, often used for manufacturing Portland cement. However, they are regarded as ecologically important, and are vulnerable to damage by silting, nutrient pollution, drainage, and invasive species. In Britain, only the marl lakes of the more remote parts of northern Scotland are likely to remain pristine into the near future.

title: Marl


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Talk:Threshing machine

Old comments (2002 and 2005)
This article is seriously outdated, so much so that I'm not sure it's even useful for a modern encylopedia, unless it were rephrased as a historical note! -- April (2002)

If you want updated information on this topic, see: Combine harvester. The Threshing machine was the historical predecessor to the combine harvester, which began to replace threshing machines early in the 20th century. That's probably why it may seem outdated. Landroo 16:00, 3 March 2007 (UTC)

I'm opposed to making wikipedia the meta-encyclopedia by including information just because it was in some old encyclopedia that happens to be in the public domain. MichaelTinkler (2002)

Not everyone appreciates the value of history, but history defines what is today. Many lessons that could have been learned from the past were repeated out of ignorance of what happened before.Landroo (talk) 16:20, 12 July 2009 (UTC)

update please
this needs to really be updated i am a nerd and i want to learn -alex pacheco (2005)

Social impact of mechanization
This section was added because the adoption of the threshing machine has become a classic argument in favor of automation. If laws had been passed in the 1830 is favor of farm laborers, and threshing machines had been outlawed, the cost of bread would have remained a very high percentage of a typical family's income for many years to come.

Landroo 19:56, 25 Jun 2006 (UTC)

cartoon
is there a talented wikiworker out there who can make a cartoon of a working thresher or combine? Sfsorrow2 22:14, 16 Aug 2006 (UTC)

"Enough to feed a thresher" - ??
The following "Interesting Fact" was added today:

 * Operating the thresher was said to be exhausting work. When the threshers would come home they were known for consuming large amounts of food. This created a phrase, commonly used by midwestern Baby Boomers, "Enough to feed a Thresher."

I have found only one online reference, and that says "the thresher" rather than "a thresher" (Chapter 23 of "O! Pioneers"), suggesting that it is the machine rather than the workers which is 'hungry'. So, I am not convinced by the explanation, which anyway counts as Original Research if it can't be backed-up.

I know online references are not the final word, but I am suspicious that this assertion is erroneous, hence the 'fact' tag.

EdJogg 10:47, 17 May 2007 (UTC)

 * Thanks for looking into that. I have removed the explanation, given the lack of a citation and no improvement over the 5 months since you added this to the talk page. Kingdon 14:01, 18 October 2007 (UTC)

Sentence removed...
The following unsourced comment was added by an anon editor today:
 * It was neverwidely used by the average farmer. Only the farmers with alot of land and money had one. It took alot of labor to do.

I have removed it since (a) it does not make sense where it was placed in the article and (b) needs further work. However, it is probably a valid sentiment.

EdJogg 23:41, 6 September 2007 (UTC)

threshing machine, or in modern spelling, threshing machine
"threshing machine, or in modern spelling, threshing machine" It says this right at the top of the article. I've read both spellings about 20 times. Am I missing something?

Inadequte
Yet another hippy-mentality English article that examines essentially only the history of the subject, and not the nuts and bolts of modern threshing machines. — Preceding unsigned comment added by Maelli (talk • contribs) 12:46, 19 September 2019 (UTC)

My name is roy
A 37.186.51.18 (talk) 09:13, 23 April 2022 (UTC)

title: Talk:Threshing machine


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User:Roger~enwiki

Software architect living in France. Pages I plan to edit :  A number of English language pages concerning France : RennesBrittanyFrench culture etc. Anything else that catches my eye.

Welcome, bienvenue, Roger! -- April

title: User:Roger~enwiki


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Pink noise

Pink noise, $1/f$ noise, fractional noise or fractal noise is a signal or process with a frequency spectrum such that the power spectral density (power per frequency interval) is inversely proportional to the frequency of the signal. In pink noise, each octave interval (halving or doubling in frequency) carries an equal amount of noise energy.

Pink noise sounds like a waterfall. It is often used to tune loudspeaker systems in professional audio. Pink noise is one of the most commonly observed signals in biological systems.

The name arises from the pink appearance of visible light with this power spectrum. This is in contrast with white noise which has equal intensity per frequency interval.

Definition
Within the scientific literature, the term 1/f noise is sometimes used loosely to refer to any noise with a power spectral density of the form

$$S(f) \propto \frac{1}{f^\alpha},$$

where f is frequency, and 0 < α < 2, with exponent α usually close to 1. One-dimensional signals with α = 1 are usually called pink noise.

The following function describes a length $$N$$ one-dimensional pink noise signal (i.e. a Gaussian white noise signal with zero mean and standard deviation $$\sigma$$, which has been suitably filtered), as a sum of sine waves with different frequencies, whose amplitudes fall off inversely with the square root of frequency $$u$$ (so that power, which is the square of amplitude, falls off inversely with frequency), and phases are random:

$$h(x)=\sigma \sqrt{\frac{N}{2}} \sum_u \frac{\chi_u}{u} \sin ( \frac{2 \pi u x}{N} +\phi_u), \quad \chi_u \sim \chi(2), \quad \phi_u \sim U(0,2\pi).$$

$$\chi_u$$ are iid chi-distributed variables, and $$\phi_u$$ are uniform random.

In a two-dimensional pink noise signal, the amplitude at any orientation falls off inversely with frequency. A pink noise square of length $$N$$ can be written as: $$h(x,y)= \frac{\sigma N}{\sqrt{2}} \sum_{u,v} \frac{\chi_{uv}}{\sqrt{u^2+v^2}} \sin \left(\frac{2 \pi}{N}(ux+vy) +\phi_{uv} \right), \quad \chi_{uv} \sim \chi(2), \quad \phi_{uv} \sim U(0,2\pi).$$

General 1/fα-like noises occur widely in nature and are a source of considerable interest in many fields. Noises with α near 1 generally come from condensed-matter systems in quasi-equilibrium, as discussed below. Noises with a broad range of α generally correspond to a wide range of non-equilibrium driven dynamical systems.

Pink noise sources include flicker noise in electronic devices. In their study of fractional Brownian motion, Mandelbrot and Van Ness proposed the name fractional noise (sometimes since called fractal noise) to describe 1/fα noises for which the exponent α is not an even integer, or that are fractional derivatives of Brownian (1/f2) noise.

Description

In pink noise, there is equal energy per octave of frequency. The energy of pink noise at each frequency level, however, falls off at roughly 3 dB per octave. This is in contrast to white noise which has equal energy at all frequency levels.

The human auditory system, which processes frequencies in a roughly logarithmic fashion approximated by the Bark scale, does not perceive different frequencies with equal sensitivity; signals around 1–4 kHz sound loudest for a given intensity. However, humans still differentiate between white noise and pink noise with ease.

Graphic equalizers also divide signals into bands logarithmically and report power by octaves; audio engineers put pink noise through a system to test whether it has a flat frequency response in the spectrum of interest. Systems that do not have a flat response can be equalized by creating an inverse filter using a graphic equalizer. Because pink noise tends to occur in natural physical systems, it is often useful in audio production. Pink noise can be processed, filtered, and/or effects can be added to produce desired sounds. Pink-noise generators are commercially available.

One parameter of noise, the peak versus average energy contents, or crest factor, is important for testing purposes, such as for audio power amplifier and loudspeaker capabilities because the signal power is a direct function of the crest factor. Various crest factors of pink noise can be used in simulations of various levels of dynamic range compression in music signals. On some digital pink-noise generators the crest factor can be specified.

Generation
Pink noise can be computer-generated by first generating a white noise signal, Fourier-transforming it, then dividing the amplitudes of the different frequency components by the square root of the frequency (in one dimension), or by the frequency (in two dimensions) etc. This is equivalent to spatially filtering (convolving) the white noise signal with a white-to-pink-filter. For a length $$N$$ signal in one dimension, the filter has the following form:

$$a(x)=\frac{1}{N} \left[ 1+ \frac{1}{\sqrt{N/2}} \cos \pi (x-1) + 2 \sum_{k=1}^{N/2-1} \frac{1}{\sqrt{k}} \cos {\frac{2\pi k}{N}(x-1)} \right].$$

Matlab programs are available to generate pink and other power-law coloured noise in one or any number of dimensions.

Power-law spectra
The power spectrum of pink noise is $$\frac{1}{f}$$ only for one-dimensional signals. For two-dimensional signals (e.g., images) the average power spectrum at any orientation falls as $$\frac{1}{f^2}$$, and in $$d$$ dimensions, it falls as $$\frac{1}{f^d}$$. In every case, each octave carries an equal amount of noise power.

The average amplitude $$a_\theta$$ and power $$p_\theta$$ of a pink noise signal at any orientation $$\theta$$, and the total power across all orientations, fall off as some power of the frequency. The following table lists these power-law frequency-dependencies for pink noise signal in different dimensions, and also for general power-law colored noise with power $$\alpha$$ (e.g.: Brown noise has $$\alpha=2$$):

Distribution of point values
Consider pink noise of any dimension that is produced by generating a Gaussian white noise signal with mean $$\mu$$ and sd $$\sigma$$, then multiplying its spectrum with a filter (equivalent to spatially filtering it with a filter $$\boldsymbol{a}$$). Then the point values of the pink noise signal will also be normally distributed, with mean $$\mu$$ and sd $$\lVert \boldsymbol{a} \rVert \sigma$$.

Autocorrelation
Unlike white noise, which has no correlations across the signal, a pink noise signal is correlated with itself, as follows.

1D signal
The Pearson's correlation coefficient of a one-dimensional pink noise signal (comprising discrete frequencies $$k$$) with itself across a distance $$d$$ in the configuration (space or time) domain is: $$r(d)=\frac{\sum_k \frac{\cos \frac{2 \pi k d}{N} }{k}}{\sum_k \frac{1}{k}}.$$ If instead of discrete frequencies, the pink noise comprises a superposition of continuous frequencies from $$k_\textrm{min}$$ to $$k_\textrm{max}$$, the autocorrelation coefficient is: $$r(d)=\frac{\textrm{Ci}(\frac{2 \pi k_\textrm{max}d}{N} )-\textrm{Ci}(\frac{2 \pi k_\textrm{min}d}{N} )}{\log \frac{k_\textrm{max}}{k_\textrm{min}}},$$ where $$\textrm{Ci}(x)$$ is the cosine integral function.

2D signal
The Pearson's autocorrelation coefficient of a two-dimensional pink noise signal comprising discrete frequencies is theoretically approximated as: $$r(d)=\frac{\sum_k \frac{J_0 (\frac{2 \pi k d}{N})}{k}}{\sum_k \frac{1}{k}},$$ where $$J_0$$ is the Bessel function of the first kind.

Occurrence
Pink noise has been discovered in the statistical fluctuations of an extraordinarily diverse number of physical and biological systems (Press, 1978; see articles in Handel & Chung, 1993, and references therein). Examples of its occurrence include fluctuations in tide and river heights, quasar light emissions, heart beat, firings of single neurons, resistivity in solid-state electronics and single-molecule conductance signals resulting in flicker noise. Pink noise describes the statistical structure of many natural images.

General 1/fα noises occur in many physical, biological and economic systems, and some researchers describe them as being ubiquitous. In physical systems, they are present in some meteorological data series, the electromagnetic radiation output of some astronomical bodies. In biological systems, they are present in, for example, heart beat rhythms, neural activity, and the statistics of DNA sequences, as a generalized pattern.

An accessible introduction to the significance of pink noise is one given by Martin Gardner (1978) in his Scientific American column "Mathematical Games". In this column, Gardner asked for the sense in which music imitates nature. Sounds in nature are not musical in that they tend to be either too repetitive (bird song, insect noises) or too chaotic (ocean surf, wind in trees, and so forth). The answer to this question was given in a statistical sense by Voss and Clarke (1975, 1978), who showed that pitch and loudness fluctuations in speech and music are pink noises. So music is like tides not in terms of how tides sound, but in how tide heights vary.

Precision timekeeping
The ubiquitous 1/f noise poses a "noise floor" to precision timekeeping. The derivation is based on. Suppose that we have a timekeeping device (it could be anything from quartz oscillators, atomic clocks, and hourglasses ). Let its readout be a real number $$x(t)$$ that changes with the actual time $$t$$. For concreteness, let us consider a quartz oscillator. In a quartz oscillator, $$x(t)$$ is the number of oscillations, and $$\dot x(t)$$ is the rate of oscillation. The rate of oscillation has a constant component $$\dot x_0$$and a fluctuating component $$\dot x_f$$, so $\dot x(t) = \dot x_0 + \dot x_f(t)$. By selecting the right units for $$x$$, we can have $$\dot x_0 = 1$$, meaning that on average, one second of clock-time passes for every second of real-time.

The stability of the clock is measured by how many "ticks" it makes over a fixed interval. The more stable the number of ticks, the better the stability of the clock. So, define the average clock frequency over the interval $$[k\tau, (k+1)\tau]$$ as$$y_k = \frac{1}{\tau}\int_{k\tau}^{(k+1)\tau}\dot x(t)dt = \frac{x( (k+1 ) \tau) - x(k\tau)}{\tau}$$Note that $$y_k$$ is unitless: it is the numerical ratio between ticks of the physical clock and ticks of an ideal clock.

The Allan variance of the clock frequency is half the mean square of change in average clock frequency:$$\sigma^2(\tau) = \frac 12 \overline{(y_{k} - y_{k-1})^2} = \frac{1}{K}\sum_{k=1}^K \frac 12 (y_{k} - y_{k-1})^2$$where $$K$$ is an integer large enough for the averaging to converge to a definite value. For example, a 2013 atomic clock achieved $$\sigma(25000\text{ seconds}) = 1.6 \times 10^{-18}$$, meaning that if the clock is used to repeatedly measure intervals of 7 hours, the standard deviation of the actually measured time would be around 40 femtoseconds.

Now we have$$y_{k} - y_{k-1} = \int_\R g(k\tau - t) \dot x_f(t) dt = (g\ast \dot x_f)(k\tau) $$where $$g(t) = \frac{-1_{[0, \tau]}(t) + 1_{[-\tau, 0]}(t)}{\tau}$$ is one packet of a square wave with height $$1/\tau$$ and wavelength $$2\tau$$. Let $$h(t)$$ be a packet of a square wave with height 1 and wavelength 2, then $$g(t) = h(t/\tau)/\tau$$, and its Fourier transform satisfies $$\mathcal F[g](\omega) = \mathcal F[h](\tau\omega)$$.

The Allan variance is then $$\sigma^2(\tau) = \frac 12 \overline{(y_{k} - y_{k-1})^2} = \frac 12 \overline{(g\ast \dot x_f)(k\tau)^2} $$, and the discrete averaging can be approximated by a continuous averaging: $$\frac{1}{K}\sum_{k=1}^K \frac 12 (y_{k} - y_{k-1})^2 \approx \frac{1}{K\tau}\int_0^{K\tau} \frac 12(g\ast \dot x_f)(t)^2 dt$$, which is the total power of the signal $$(g\ast \dot x_f)$$, or the integral of its power spectrum: $$\sigma^2(\tau) \approx \int_0^\infty S[g\ast \dot x_f](\omega) d\omega = \int_0^\infty S[g](\omega) \cdot S[\dot x_f](\omega) d\omega = \int_0^\infty S[h](\tau \omega) \cdot S[\dot x_f](\omega) d\omega$$In words, the Allan variance is approximately the power of the fluctuation after bandpass filtering at $$\omega \sim 1/\tau$$ with bandwidth $$\Delta\omega \sim 1/\tau $$.

For $$1/f^\alpha$$ fluctuation, we have $$S[\dot x_f](\omega) = C/\omega^\alpha$$ for some constant $$C$$, so $$\sigma^2(\tau) \approx \tau^{\alpha-1} \sigma^2(1) \propto \tau^{\alpha-1}$$. In particular, when the fluctuating component $$\dot x_f$$ is a 1/f noise, then $$\sigma^2(\tau)$$ is independent of the averaging time $$\tau$$, meaning that the clock frequency does not become more stable by simply averaging for longer. This contrasts with a white noise fluctuation, in which case $$\sigma^2(\tau) \propto \tau^{-1}$$, meaning that doubling the averaging time would improve the stability of frequency by $$\sqrt 2$$.

The cause of the noise floor is often traced to particular electronic components (such as transistors, resistors, and capacitors) within the oscillator feedback.

Humans
In brains, pink noise has been widely observed across many temporal and physical scales from ion channel gating to EEG and MEG and LFP recordings in humans. In clinical EEG, deviations from this 1/f pink noise can be used to identify epilepsy, even in the absence of a seizure, or during the interictal state. Classic models of EEG generators suggested that dendritic inputs in gray matter were principally responsible for generating the 1/f power spectrum observed in EEG/MEG signals. However, recent computational models using cable theory have shown that action potential transduction along white matter tracts in the brain also generates a 1/f spectral density. Therefore, white matter signal transduction may also contribute to pink noise measured in scalp EEG recordings.

It has also been successfully applied to the modeling of mental states in psychology, and used to explain stylistic variations in music from different cultures and historic periods. Richard F. Voss and J. Clarke claim that almost all musical melodies, when each successive note is plotted on a scale of pitches, will tend towards a pink noise spectrum. Similarly, a generally pink distribution pattern has been observed in film shot length by researcher James E. Cutting of Cornell University, in the study of 150 popular movies released from 1935 to 2005.

Pink noise has also been found to be endemic in human response. Gilden et al. (1995) found extremely pure examples of this noise in the time series formed upon iterated production of temporal and spatial intervals. Later, Gilden (1997) and Gilden (2001) found that time series formed from reaction time measurement and from iterated two-alternative forced choice also produced pink noises.

Electronic devices
The principal sources of pink noise in electronic devices are almost invariably the slow fluctuations of properties of the condensed-matter materials of the devices. In many cases the specific sources of the fluctuations are known. These include fluctuating configurations of defects in metals, fluctuating occupancies of traps in semiconductors, and fluctuating domain structures in magnetic materials. The explanation for the approximately pink spectral form turns out to be relatively trivial, usually coming from a distribution of kinetic activation energies of the fluctuating processes. Since the frequency range of the typical noise experiment (e.g., 1 Hz – 1 kHz) is low compared with typical microscopic "attempt frequencies" (e.g., 1014 Hz), the exponential factors in the Arrhenius equation for the rates are large. Relatively small spreads in the activation energies appearing in these exponents then result in large spreads of characteristic rates. In the simplest toy case, a flat distribution of activation energies gives exactly a pink spectrum, because $$\textstyle \frac{d}{df}\ln f = \frac{1}{f}.$$

There is no known lower bound to background pink noise in electronics. Measurements made down to 10−6 Hz (taking several weeks) have not shown a ceasing of pink-noise behaviour. (Kleinpenning, de Kuijper, 1988) measured the resistance in a noisy carbon-sheet resistor, and found 1/f noise behavior over the range of $$[10^{-5.5} \mathrm{Hz}, 10^4 \mathrm{Hz}]$$, a range of 9.5 decades.

A pioneering researcher in this field was Aldert van der Ziel.

Flicker noise is commonly used for the reliability characterization of electronic devices. It is also used for gas detection in chemoresistive sensors by dedicated measurement setups.

In gravitational wave astronomy
1/fα noises with α near 1 are a factor in gravitational-wave astronomy. The noise curve at very low frequencies affects pulsar timing arrays, the European Pulsar Timing Array (EPTA) and the future International Pulsar Timing Array (IPTA); at low frequencies are space-borne detectors, the formerly proposed Laser Interferometer Space Antenna (LISA) and the currently proposed evolved Laser Interferometer Space Antenna (eLISA), and at high frequencies are ground-based detectors, the initial Laser Interferometer Gravitational-Wave Observatory (LIGO) and its advanced configuration (aLIGO). The characteristic strain of potential astrophysical sources are also shown. To be detectable the characteristic strain of a signal must be above the noise curve.

Climate dynamics
Pink noise on timescales of decades has been found in climate proxy data, which may indicate amplification and coupling of processes in the climate system.

Diffusion processes
Many time-dependent stochastic processes are known to exhibit 1/fα noises with α between 0 and 2. In particular Brownian motion has a power spectral density that equals 4D/f2, where D is the diffusion coefficient. This type of spectrum is sometimes referred to as Brownian noise. Interestingly, the analysis of individual Brownian motion trajectories also show 1/f2 spectrum, albeit with random amplitudes. Fractional Brownian motion with Hurst exponent H also show 1/fα power spectral density with α=2H+1 for subdiffusive processes (H<0.5) and α=2 for superdiffusive processes (0.5<H<1).

Origin
There are many theories about the origin of pink noise. Some theories attempt to be universal, while others apply to only a certain type of material, such as semiconductors. Universal theories of pink noise remain a matter of current research interest.

A hypothesis (referred to as the Tweedie hypothesis) has been proposed to explain the genesis of pink noise on the basis of a mathematical convergence theorem related to the central limit theorem of statistics. The Tweedie convergence theorem describes the convergence of certain statistical processes towards a family of statistical models known as the Tweedie distributions. These distributions are characterized by a variance to mean power law, that have been variously identified in the ecological literature as Taylor's law and in the physics literature as fluctuation scaling. When this variance to mean power law is demonstrated by the method of expanding enumerative bins this implies the presence of pink noise, and vice versa. Both of these effects can be shown to be the consequence of mathematical convergence such as how certain kinds of data will converge towards the normal distribution under the central limit theorem. This hypothesis also provides for an alternative paradigm to explain power law manifestations that have been attributed to self-organized criticality.

There are various mathematical models to create pink noise. Although self-organised criticality has been able to reproduce pink noise in sandpile models, these do not have a Gaussian distribution or other expected statistical qualities. It can be generated on computer, for example, by filtering white noise,  inverse Fourier transform, or by multirate variants on standard white noise generation.

In supersymmetric theory of stochastics, an approximation-free theory of stochastic differential equations, 1/f noise is one of the manifestations of the spontaneous breakdown of topological supersymmetry. This supersymmetry is an intrinsic property of all stochastic differential equations and its meaning is the preservation of the continuity of the phase space by continuous time dynamics. Spontaneous breakdown of this supersymmetry is the stochastic generalization of the concept of deterministic chaos, whereas the associated emergence of the long-term dynamical memory or order, i.e., 1/f and crackling noises, the Butterfly effect etc., is the consequence of the Goldstone theorem in the application to the spontaneously broken topological supersymmetry.

Audio testing
Pink noise is commonly used to test the loudspeakers in sound reinforcement systems, with the resulting sound measured with a test microphone in the listening space connected to a spectrum analyzer or a computer running a real-time fast Fourier transform (FFT) analyzer program such as Smaart. The sound system plays pink noise while the audio engineer makes adjustments on an audio equalizer to obtain the desired results. Pink noise is predictable and repeatable, but it is annoying for a concert audience to hear. Since the late 1990s, FFT-based analysis enabled the engineer to make adjustments using pre-recorded music as the test signal, or even the music coming from the performers in real time. Pink noise is still used by audio system contractors and by computerized sound systems which incorporate an automatic equalization feature.

In manufacturing, pink noise is often used as a burn-in signal for audio amplifiers and other components, to determine whether the component will maintain performance integrity during sustained use. The process of end-users burning in their headphones with pink noise to attain higher fidelity has been called an audiophile "myth".

title: Pink noise